tag:blogger.com,1999:blog-91737888936576036982024-03-08T06:16:42.601-08:00Power Quality In Electrical SystemsPowerQualityWorld is a compilation of various power quality information, issues, applications, technologies, news and updates.
yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.comBlogger97110tag:blogger.com,1999:blog-9173788893657603698.post-65799334188612557152012-06-17T01:24:00.000-07:002012-06-17T01:29:48.967-07:00EFFECTS OF HARMONICS ON CAPACITORS<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The <b>Effects of Harmonics on Capacitors</b>
include additional heating - and in severe cases overloading, increased
dielectric or voltage stress, and unwanted losses. Also, the combination of <a href="http://www.powerqualityworld.com/2011/07/harmonics-power-quality-basics.html">harmonics</a>
and capacitors in a system could lead to a more severe <a href="http://www.powerqualityworld.com/2011/03/what-is-power-quality.html">power quality</a> condition called
harmonic resonance, which has the potential for extensive damage. Consequently,
these negative effects will </span><span style="font-family: Arial, sans-serif;">shorten capacitor life.</span><br />
<span style="font-family: Arial, sans-serif; line-height: 150%;"></span><br />
<a name='more'></a><span style="font-family: Arial, sans-serif; line-height: 150%;">Capacitors are typically installed in
the electrical power system – from commercial and industrial to distribution
and transmission systems – as power factor correction devices. However, even
though it is a basic component of a </span><a href="http://www.powerqualityworld.com/2011/08/harmonic-filters-power-quality.html" style="font-family: Arial, sans-serif; line-height: 150%;">harmonic filter</a><span style="font-family: Arial, sans-serif; line-height: 150%;"> (aside from the
reactor), it is not free from the damaging effects of harmonics. In a power
system characterized by high harmonic distortion levels, capacitor banks are
vulnerable to failures.</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>IEEE Limits</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><a href="http://www.powerqualityworld.com/2011/03/ieee-power-quality-standards.html">IEEE 18-2002</a>
states that a </span><span style="font-family: Arial, sans-serif;">capacitor
is designed to operate at a maximum of 135% of its reactive power (kVAR)
ratings. In addition, it must withstand a continuous RMS <a href="http://www.powerqualityworld.com/2011/03/power-quality-basics-overvoltage.html">overvoltage</a> of 110%,
peak overvoltage of 120%, and an overcurrent of 180% of nameplate rating</span><span style="font-family: Arial, sans-serif;">. Although
the standard did not specify the limits for individual harmonics, the above percentages
can be used as basis to determine the maximum allowable harmonic levels. </span><span style="font-family: Arial, sans-serif;"> </span><span style="font-family: Arial, sans-serif;"><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Harmonic Effects</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The
reactance of a <a href="http://www.powerqualityworld.com/2011/06/shunt-capacitors.html">capacitor bank</a> is inversely proportional to the frequency, as
can be noted in the formula, <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Xc = 1/(2πfC)<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">where:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Xc =
Capacitive reactance<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">C =
Capacitance<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">f =
Frequency<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">As a
result, the capacitor bank acts like a sink, attracting unfiltered harmonic
currents. This effect increases the thermal and dielectric stresses to the
capacitor units (i.e. overload). <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">To
illustrate, consider a harmonic-rich electrical system with 5<sup>th</sup>
harmonic voltage of around 20% the fundamental. A</span><span style="background-color: white; font-family: Arial, sans-serif;"> 4160 V, 300 kVAR capacitor
bank has a reactance of 57.7 Ω at the fundamental frequency (e.g. 60 Hz) and
shall draw a capacitive current of 41.6 A according to Ohm's Law. On the other
hand, the capacitor reactance is only 11.54 Ω at the 5<sup>th</sup> harmonic (5
x 60 = 300 Hz). Subsequently, this same capacitor bank energized with 5<sup>th</sup>
order harmonic voltage will also draw 41.6 A. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="background-color: white; font-family: Arial, sans-serif;">Fundamental
Current:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="background-color: white; font-family: Arial, sans-serif; line-height: 150%;">I</span><sub style="font-family: Arial, sans-serif; line-height: 150%;">1</sub><span style="background-color: white; font-family: Arial, sans-serif; line-height: 150%;">
= 4.16 kV/(√3)(57.7 Ω)</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="background-color: white; font-family: Arial, sans-serif;">I<sub>1</sub>
= 41.62 A<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">5<sup>th</sup>
Harmonic Current:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;">I<sub>5</sub>
= (20%)(4.16 kV)/(</span><span style="background-color: white; font-family: Arial, sans-serif; line-height: 150%;"> √3)(11.54 Ω)</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">I<sub>5</sub>
= 41.62 A<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Total RMS
current:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;">Irms = √(I</span><sub style="font-family: Arial, sans-serif; line-height: 150%;">1</sub><sup style="font-family: Arial, sans-serif; line-height: 150%;">2</sup><span style="font-family: Arial, sans-serif; line-height: 150%;">
+ I</span><sub style="font-family: Arial, sans-serif; line-height: 150%;">H</sub><sup style="font-family: Arial, sans-serif; line-height: 150%;">2</sup><span style="font-family: Arial, sans-serif; line-height: 150%;">) = √(41.62</span><sup style="font-family: Arial, sans-serif; line-height: 150%;">2</sup><span style="font-family: Arial, sans-serif; line-height: 150%;"> + 41.62</span><sup style="font-family: Arial, sans-serif; line-height: 150%;">2</sup><span style="font-family: Arial, sans-serif; line-height: 150%;">)</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Irms = 58.86
A or 141.4% of Fundamental Current (I<sub>1</sub>) – could blow capacitor fuses</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><br /></span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-5pqgFP6M_Z0/T92OY7VU3nI/AAAAAAAAAVg/HlqF6BIhwxs/s1600/Harmonics-Capacitors.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="http://3.bp.blogspot.com/-5pqgFP6M_Z0/T92OY7VU3nI/AAAAAAAAAVg/HlqF6BIhwxs/s640/Harmonics-Capacitors.jpg" width="635" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">Increase in Capacitor Current Due to Harmonics</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;">In such
cases, nuisance blowing is expected since most capacitor fuses are sized based
on the 135% kVAR limit. Otherwise, capacitor unit shall suffer overloading and
heating. This shows why nuisance capacitor fuse blowing and/or breaker tripping
indicate very high harmonic distortion levels in the area.</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Moreover, frequent
switching of nonlinear magnetic components such as reactors and transformers
can generate harmonic currents that will increase capacitor loading.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Harmonic Resonance</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">A serious concern
arising from the use of capacitors in an electrical power system is the
possibility of system resonance. This effect imposes voltages and currents that
are higher than would be the case without resonance.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Harmonic resonance in a power system
may be classified as parallel or series resonance, and both types are present
in a harmonic-rich environment. Parallel resonance causes current
multiplication, whereas series resonance produces voltage magnification. Substantial
damage to capacitor banks would result if the amplitude of the offending
frequency is large enough during resonant conditions. Also, there is a high probability
that other electrical devices on the system would also be damaged.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">For such reason, harmonic analysis
must be performed before installation of a power factor improvement capacitor
bank to ensure that resonance frequencies do not correspond with prominent
harmonics contained in the currents and voltages.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>References:</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">IEEE 519-1992. Recommended Practice
and Requirements for Harmonic Control in Electrical Power Systems<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Sankaran, C. (1999). Effects of
Harmonics on Power Systems 1<o:p></o:p></span></div>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com9tag:blogger.com,1999:blog-9173788893657603698.post-27323248965949657242012-05-31T08:39:00.000-07:002012-05-31T08:45:01.652-07:00STATIC SYNCHRONOUS SERIES COMPENSATOR (SSSC)<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Static Synchronous Series Compensator
(SSSC)</b> is a modern <a href="http://www.powerqualityworld.com/2011/03/what-is-power-quality.html" target="_blank">power quality</a> FACTS device that employs a voltage source converter
connected in series to a transmission line through a transformer. The SSSC
operates like a controllable series capacitor and series inductor. The primary
difference is that its injected voltage is not related to the line intensity
and can be managed independently. This feature allows the SSSC to work
satisfactorily with high loads as well as with lower loads.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"></span></div>
<span style="font-family: Arial, sans-serif; line-height: 150%; text-align: justify;"></span><br />
<a name='more'></a><span style="font-family: Arial, sans-serif; line-height: 150%; text-align: justify;">The Static Synchronous Series
Compensator has three basic components:</span><br />
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l0 level1 lfo3; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">a.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Voltage
Source Converter (VSC) – main component<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l0 level1 lfo3; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">b.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Transformer
– couples the SSSC to the transmission line<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l0 level1 lfo3; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">c.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">Energy
Source – provides voltage across the DC capacitor and compensate for device losses </span><span style="font-family: Arial, sans-serif; line-height: 150%;"> </span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-kAlXX4NgYUc/T8eJDRARlUI/AAAAAAAAAU4/40YQPuT3qBE/s1600/SSSC-Static-Synchronous-Series-Compensator.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Static Synchronous Series Compensator (SSSC)" border="0" src="http://3.bp.blogspot.com/-kAlXX4NgYUc/T8eJDRARlUI/AAAAAAAAAU4/40YQPuT3qBE/s1600/SSSC-Static-Synchronous-Series-Compensator.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">Static Synchronous Series Compensator (SSSC) Diagram</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<b><span style="font-family: Arial, sans-serif; line-height: 150%;">Operation and Capabilities</span></b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Static synchronous series compensator
works like the <a href="http://www.powerqualityworld.com/2011/09/statcom-static-synchronous-compensator.html">STATCOM</a>, except that it is serially connected instead of shunt. It
is able to transfer both active and reactive power to the system, permitting it
to compensate for the resistive and reactive voltage drops – maintaining high
effective X/R that is independent of the degree of series compensation.
However, this is costly as a relatively large energy source is required.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">On the other hand, if control is
limited to reactive compensation then a smaller supply should be enough. In
this case only the voltage is controllable because the voltage vector forms 90º
with the line intensity. Subsequently, the serial injected voltage can advance
or delay the line current, meaning, the SSSC can be uniformly controlled in any
value.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The SSSC when operated with the proper
energy supply can inject a voltage component, which is of the same magnitude
but opposite in phase angle with the voltage developed across the line. As a
result, the effect of the voltage drop on power transmission is offset. In
addition, the static synchronous series compensator provides fast control and is
inherently neutral to sub-synchronous resonance.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><u>Modes of Operation</u><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Generally, the line reactance is
constant but its net effect can be controlled through voltage injection. For
instance, the line current decreases as the inductive reactance compensation
level increases from 0% to 100%. Meanwhile, the line current increases with the
capacitive reactance compensation level from 0% to 33%.</span><span style="font-family: Arial, sans-serif; line-height: 150%;"> </span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-yFY_OKZYksw/T8eJ0ifulGI/AAAAAAAAAVI/Q6mUi1chBXI/s1600/SSSC-Modes-of-Operation.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="SSSC Modes of Operation" border="0" src="http://2.bp.blogspot.com/-yFY_OKZYksw/T8eJ0ifulGI/AAAAAAAAAVI/Q6mUi1chBXI/s1600/SSSC-Modes-of-Operation.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">SSSC Modes of Operation</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;">It can be noted that the static
synchronous series compensator does not only increase the transferable power
but it can also decrease it, by simply reversing the polarity of the injected voltage.
This reversed polarity voltage is fed directly to the line voltage drop as if
the line impedance was increased.</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In short, the effects of reactance compensation
on normalized power flow in the transmission line are as follows:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l2 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">When
the emulated reactance is capacitive, the active and reactive power flow
increases and the effective reactance decreases as the reactance compensation
increases in the positive direction.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l2 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">When
the emulated reactance is inductive, the active and reactive power flow
decrease and the effective reactance increases as the reactance compensation
increases in the negative direction<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>SSSC and DVR </b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The SSSC’s counterpart is the <a href="http://www.powerqualityworld.com/2011/06/dvr-dynamic-voltage-restorer.html">Dynamic VoltageRegulator (DVR)</a>. Although both are utilized for series <a href="http://www.powerqualityworld.com/2011/03/voltage-sags-dips-power-quality-basics.html">voltage sag</a>
compensation, their operating principles differ from each other. The static
synchronous series compensator injects a balance voltage in series with the
transmission line. On the other hand, the DVR compensates the unbalance in
supply voltage of different phases. Also, DVRs are usually installed on a
critical feeder supplying the active power through DC energy storage and the required
reactive power is generated internally without any means of DC storage. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Applications and Advantages</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The SSSC is typically applied to correct
the voltage during a fault in the power system. However, it also has several
advantages during normal conditions:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l1 level1 lfo2; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">Power
factor correction through continuous voltage injection and in combination with
a properly structured controller.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l1 level1 lfo2; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Load
balancing in interconnected distribution networks.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l1 level1 lfo2; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">It
can also help to cover the capacitive and reactive power demand.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l1 level1 lfo2; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Power
flow control.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l1 level1 lfo2; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Reduces
<a href="http://www.powerqualityworld.com/2011/07/harmonics-power-quality-basics.html">harmonic distortion</a> by active filtering.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>References:</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">El-Zonkoly A. (2006). Optimal Sizing
of SSSC Controllers to Minimize Transmission Loss and a Novel Model of SSSC to
Study Transient Response.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Gupta S., Pachar, R., and Tiwari, H.
(2010). Study on Major Issues and Their Impact on DVR System Performance.<o:p></o:p></span></div>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com0tag:blogger.com,1999:blog-9173788893657603698.post-930752466401180362012-04-30T07:58:00.000-07:002012-04-30T08:10:12.334-07:00FERRORESONANCE PREVENTION TUTORIALS<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Ferroresonance Prevention Tutorials</b>
deal with strategies that electric utilities and end-users could implement to
minimize occurrence of the power quality phenomenon. These practices are based
from the fact that ferroresonance usually happens with lightly loaded three-phase
transformer, having one or two phases open either intentionally or accidentally. Common strategies for managing ferroresonance
include: Preventing open phase condition, limiting overvoltages, damping
resonance with secondary load, limiting cable length, switching at transformer terminals
and grounding transformer primary.</span><br />
<b style="line-height: 150%;"><span style="font-family: Arial, sans-serif;"></span></b><br />
<a name='more'></a><b style="line-height: 150%;"><span style="font-family: Arial, sans-serif;">Prevention
of Open Phase Condition</span></b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><a href="http://www.powerqualityworld.com/2012/02/ferroresonance.html">Ferroresonance</a> is often the result of
linemen performing single-pole switching in lateral lines or blown fuses in one
or two of the phases due to short-circuits. Therefore, a logical effective
measure against ferroresonance would be to use three-phase or three-pole
switches and fault interrupters instead of fuse cut-outs. However, this would
be very costly and electric utilities could not afford to do this at every
riser pole, except in special cases where there are frequent fuse blowings and
sensitive end-users. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In addition, if single-pole switching
can’t be avoided, opening or closing all three phases should be executed as quickly
as possible.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<b><span style="font-family: Arial, sans-serif;">Limiting
Cable Length <o:p></o:p></span></b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Another strategy for ferroresonance
prevention is to limit the length of cable runs. This is because when cable
capacitance reaches critical value, it could resonate with the transformer
inductance. For delta primary connections cable length should be less than 100
feet, while the WYE(G) – wye(g) could tolerate a few hundred feet of cable
without exceeding 125% overvoltage during open phase conditions. Moreover, allowable
cable length is dependent on the voltage level – shorter cable for higher
system voltage.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<b><span style="font-family: Arial, sans-serif;">Switching
at Transformer Terminals<o:p></o:p></span></b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The location of switching when
energizing or deenergizing a transformer can play an important role in ferroresonance
prevention.</span><span style="font-family: Arial, sans-serif; line-height: 150%;"> </span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-afF023a6tZQ/T56mhymPpQI/AAAAAAAAAUs/kLCBt4mAA-0/s1600/Transformer-Switching-Ferroresonance.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="352" src="http://1.bp.blogspot.com/-afF023a6tZQ/T56mhymPpQI/AAAAAAAAAUs/kLCBt4mAA-0/s400/Transformer-Switching-Ferroresonance.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">Transformer Switching: (a) At transformer terminals; (b) At remote tapping point</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;">Diagram (a) shows switching at the
transformer terminals (switch R) after the underground cable is energized thru
switch L. Occurrence of ferroresonance is reduced since the capacitance seen
from an open phase after each phase of switch R closes is only the
transformer’s internal capacitance. The second diagram (b) illustrates remotely
energizing the transformer. Consequently, the likelihood of ferroresonance is
increased as the capacitance seen from switch L includes the cable capacitance.
Thus, one of the common ways of ferroresonance prevention during cable
switching is to switch the transformer by pulling the elbows at primary
terminals.</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<b><span style="font-family: Arial, sans-serif;">Secondary
Load<o:p></o:p></span></b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Ferroresonance can be suppressed by
the presence of secondary resistive loads. The amount of load needed is
dependent on the cable length and the transformer design. In a typical open
phase, a 10% resistive transformer load can significantly lessen the effects of
ferroresonance.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In contrast, cases with two phases
open are harder to dampen with load especially if coupled with having very long
cable runs (1 km or more). The transformer would have to be about 25% resistive
loaded just to restrict overvoltages to the commonly accepted threshold of 1.25
pu. Several electric utilities have reported that line crews carry resistive
load banks in their vehicles for use in cable-switching activity when the
transformers are unloaded or lightly loaded.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<b><span style="font-family: Arial, sans-serif;">Resistance
Grounding of Y-Connected Primary<o:p></o:p></span></b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Resistance grounding can prevent
ferroresonance. Nonetheless, this solution may create conflicting constraints
in that a resistor must be chosen to be high enough to avoid the bank from
acting as a low-impedance ground-current source but low enough to prevent
ferroresonance. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<b><span style="font-family: Arial, sans-serif;">Caution:</span></b><span style="font-family: Arial, sans-serif;"> Neutral point of primary windings
should be isolated from persons for safety purposes. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><a href="http://www.powerqualityworld.com/2012/03/ferroresonance-transformer-connection.html">READ MORE ABOUT FERRORESONANCE AND TRANSFORMER CONNECTIONS</a><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<b><span style="font-family: Arial, sans-serif;">Limiting
Overvoltages<o:p></o:p></span></b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><a href="http://www.powerqualityworld.com/2011/05/surge-arresters.html">Surge arresters</a> are effective
protection for the <a href="http://www.powerqualityworld.com/2011/03/power-quality-basics-overvoltage.html">overvoltage</a> effects of ferroresonance, particularly for
transformers with ungrounded primary connections where the voltages can go as
high as 3-4 per unit of nominal. These devices could limit the voltages to less
than 2.0 pu. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">However, surge arresters could fail
when subjected to long periods of ferroresonance. If linemen come across a
transformer with arresters in ferroresonance, they should always deenergize the
unit and wait for some time to cool the arresters. Overheated arresters could
fail hazardously if immediately reconnected to a source with high short-circuit
capacity.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<b><span style="font-family: Arial, sans-serif;">References:<o:p></o:p></span></b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Dugan, R., McGranaghan, M., Santoso,
S., and Beaty, H.W. (2004). Electrical Power Systems Quality (2nd ed.). <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">IEEE C57.105-1978. Guide for
Application of Transformer Connections in Three-Phase Distribution Systems<o:p></o:p></span></div>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com0tag:blogger.com,1999:blog-9173788893657603698.post-3887067413626442082012-03-24T18:18:00.000-07:002012-03-24T18:22:47.671-07:00FERRORESONANCE AND TRANSFORMER CONNECTIONS<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Ferroresonance</b> and <b>Transformer Connections</b>
are related as such that the latter is a significant factor to the occurrence
of the former during loss of phase or open phase conditions. There are certain transformer
configurations that are more susceptible to ferroresonance. Generally, ferroresonance
phenomenon becomes highly probable if the primary windings of the three-phase
transformer are ungrounded.</span><br />
<b style="font-family: Arial, sans-serif; line-height: 150%;"></b><br />
<a name='more'></a><b style="font-family: Arial, sans-serif; line-height: 150%;">Susceptible Transformer Connections</b></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><br /></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Ferroresonance is more likely to
happen with transformer banks of certain connections, particularly when the
bank is energized or deenergized using single-pole switches at a location
remote from the transformer, or when a conductor or fuse at a relatively
distant location opens. The table below shows frequently employed three-phase
transformer connections, which are prone to ferroresonance.</span><span style="font-family: Arial, sans-serif; line-height: 150%;"> </span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-gOt67CDlRm4/T25w9U-u21I/AAAAAAAAAUc/9C5WP-apSq0/s1600/Ferroresonance-Transformer-Connections-Prone.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="http://1.bp.blogspot.com/-gOt67CDlRm4/T25w9U-u21I/AAAAAAAAAUc/9C5WP-apSq0/s400/Ferroresonance-Transformer-Connections-Prone.jpg" width="281" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">Transformer Connections Susceptible to Ferroresonance (IEEE)</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;">The possibility of ferroresonance also
depends on the system and transformer electrical characteristics. Given a particular
transformer connection, the presence of phase-to-phase and/or phase-to-ground
capacitance of the lateral circuit and the transformer internal capacitance are
the main parameters that have the most effect on the establishment of
ferroresonance during loss of phase or open-phase conditions. The phenomenon
will happen only if the capacitances of the transformer and lateral circuit are
within a given range. The lower and upper bounds of this capacitance range are
established by the transformer size and design, as well as the primary voltage.
Typically, ferroresonance is more probable with smaller transformers in higher
primary voltage.</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In other words, the chance of
occurrence is increased as:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Transformer
connection is one of those listed above<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Transformer
size is reduced<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Primary
voltage is increased<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Lateral
length is increased<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Lateral
conductor is underground shielded cable <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Nonetheless, ferroresonance can occur
even if NOT all of the above-mentioned conditions are satisfied. For example, in
a 34.5 kV multigrounded neutral overhead system, ferroresonance with
overvoltages as high as 4-5 per unit has been recorded when energizing, even at
transformer terminals, ungrounded WYE-delta banks utilizing small single-phase
transformers. On the other hand, although not likely, ferroresonance can occur
for primary voltages below 12 kV when single-conductor shielded cable is used
to connect the single-pole fuses to the transformer. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Least Prone Transformer Connections</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Three-Phase Transformer Bank Connections
indicated below are least susceptible to ferroresonance. This is because the
line-to-ground capacitance of the lateral line and transformer is bypassed by
the solid connection to ground. However, please take note of the term “least
prone” – meaning they can still be subjected to ferroresonance but at a lower
risk.</span><span style="font-family: Arial, sans-serif; line-height: 150%;"> </span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-sqmLVK96E8M/T25x1OCxdEI/AAAAAAAAAUk/gfHBPTadWPU/s1600/Ferroresonance-Transformer-Connections-Least-Prone.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="241" src="http://3.bp.blogspot.com/-sqmLVK96E8M/T25x1OCxdEI/AAAAAAAAAUk/gfHBPTadWPU/s320/Ferroresonance-Transformer-Connections-Least-Prone.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">Ferroresonance-Free Transformer Connections</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;">For example, </span><span style="font-family: Arial, sans-serif; line-height: 150%;">if YG–yg
transformer is supplied through open-wire circuits where phase-to-phase
capacitance exists, ferroresonance could occur whether or not the bank consists
of three single-phase units or is a triplex three-phase unit.</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Fortunately,
the length of line required for ferroresonance under these conditions (over
three kilometers) is greater than that which normally exists between the
single-pole devices and the transformers. However, there should be caution if a
delta or ungrounded wye capacitor bank is installed between the single-pole
devices and transformer, since such condition leads to ferroresonance. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Otherwise,
the transformer connection with grounded WYE or grounded OPEN WYE primary is
considered free from ferroresonance. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Reference:</b><o:p></o:p></span></div>
<span style="font-family: Arial, sans-serif; font-size: 11pt; line-height: 115%;">IEEE C57.105-1978. Guide for Application of
Transformer Connections in Three-Phase Distribution Systems</span>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com2tag:blogger.com,1999:blog-9173788893657603698.post-62230682297848171412012-02-29T06:47:00.000-08:002012-02-29T16:27:01.392-08:00POWER QUALITY BASICS: FERRORESONANCE<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Ferroresonance</b> is usually described as
an irregular and chaotic type of resonance. This phenomenon occurs because of
the nonlinear characteristic of iron-core (saturable) inductors - ferromagnetic
material such as a transformer. Ferroresonance is often times associated with
unwanted and destructive overvoltages, but has found some helpful applications
in <a href="http://www.powerqualityworld.com/2011/04/constant-voltage-ferroresonant.html" target="_blank">Constant Voltage Transformers</a>, which can mitigate power quality problems
like voltage sags.<o:p></o:p></span><br />
</div>
<span style="font-family: Arial, sans-serif;"></span><br />
<a name='more'></a><br />
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Basically, ferroresonance involves series
connection of saturable inductors and system capacitance due to <a href="http://www.powerqualityworld.com/2011/06/shunt-capacitors.html">shunt capacitor banks</a>, <a href="http://www.powerqualityworld.com/2011/06/series-capacitors.html">series capacitors</a>, internal capacitance of transformers, overhead lines
and cables. </span><span style="font-family: Arial, sans-serif;">It does not normally occur in distribution systems but certain
conditions may be established such as an open phase during single-pole
switching. In connection, transformer bank configurations become a significant
factor that affects the occurrence of ferroresonance. <o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-layout-grid-align: none; text-autospace: none;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Causes</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Loss of
phase/s or having an open phase is the most common condition that makes
ferroresonance highly possible to occur (but not always). Some of these events
are listed below:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l1 level1 lfo2; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">1.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">One or two
distribution cut-out fuses may blow leaving a transformer with one or two
phases open. This is also true with single-phase reclosers. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l1 level1 lfo2; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">2.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">Switching
manually an unloaded three-phase transformer or transformer bank (cable-fed) where
only one phase is closed. Ferroresonance may occur when the first line is
closed for energization, or before the last phase is opened on deenergization. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l1 level1 lfo2; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">3.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">Manual
switching of an unloaded, cable-fed, three-phase transformer where one of the
lines is open either during energization or deenergization.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Moreover, there
are ordinary system conditions that help increase the possibility of the
ferroresonance phenomenon including, but not limited to:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Three-phase systems with single-phase switching
devices (e.g. cut-out fuses)<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Ungrounded transformer primary connections<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Higher distribution voltage levels – above 15 kV <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Long underground cable circuits<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Manual switching and cable damage during
construction of underground cable systems<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Switching of unloaded or lightly loaded
transformers<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Low-loss transformers (e.g. amorphous)<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .5in; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="font-family: Arial, sans-serif;">Unstable and weak systems (low short-circuit MVA)<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>How Does Ferroresonance Occur? </b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The figure
below shows an effectively grounded three-phase source supplying an unloaded
three-phase transformer with Delta Primary. In between the connection are single-pole
switches and shielded cables, which have considerable capacitance to
ground (C).</span><span style="font-family: Arial, sans-serif; line-height: 150%;"> </span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-sW9Yyh6LF0k/T0433CTZ2BI/AAAAAAAAAUU/zWH_8dedd64/s1600/Ferroresonance-Circuit.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="281" src="http://2.bp.blogspot.com/-sW9Yyh6LF0k/T0433CTZ2BI/AAAAAAAAAUU/zWH_8dedd64/s400/Ferroresonance-Circuit.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">Sample Ferroresonance Circuit</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;">When the switch
for phase A is closed, two of the transformer’s phases are energized via the
cable capacitances from B-G and C-G. In AC circuits, recall that capacitance
appears as a short circuit at the instant of closing. This causes the
transformer windings of legs A-B and A-C to draw the normal inrush current.</span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The transformer
iron during the first cycle of applied voltage could saturate due to closing at
or near zero voltage and/or due to residual flux in the transformer core. Consequently,
saturation produces large current pulse through the transformer windings and
capacitances of phases B and C. Then, the transformer iron drops out of
saturation leaving an ample trapped charge (voltage) on the cable capacitance.
In the succeeding cycles, the transformer may go into saturation in the
opposite direction, thus, changing the polarity of the trapped charge on the
capacitance. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">If the
transformer continues to go into and out of saturation, line-to-line and
line-to-ground overvoltages shall occur, which can cause over-excitation of the
transformer, and failure of arresters and insulation in the transformer or
system. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Furthermore,
closing the second phase may result to no better condition than as described
above. Nonetheless, if all three phases are closed, ferroresonance will cease.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-layout-grid-align: none; text-autospace: none;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Effects and
Indicators</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Ferroresonance
can usually lead to the following malfunctions that can be noted and measured:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l2 level1 lfo3; text-align: justify; text-indent: -.25in;">
<span style="color: #231f20; font-family: Arial, sans-serif;">a.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="color: #231f20; font-family: Arial, sans-serif;"><a href="http://www.powerqualityworld.com/2011/03/power-quality-basics-overvoltage.html">Overvoltages</a><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Peak
voltages (i.e. line-to-line and/or line-to-ground) may reach up to five or more
times the system nominal voltage. <a href="http://www.powerqualityworld.com/2011/05/surge-arresters.html">Surge arresters</a>, particularly low-voltage
types are commonly damaged, which indicates the occurrence of ferroresonance. Other
devices such as electronics may also fail due to high voltage.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l2 level1 lfo3; text-align: justify; text-indent: -.25in;">
<span style="color: #231f20; font-family: Arial, sans-serif;">b.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">
</span></span><span style="color: #231f20; font-family: Arial, sans-serif;">Excessive
Noise in the Transformer<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="color: #231f20; font-family: Arial, sans-serif;">This is mainly caused by the magnetostriction of the steel core being
driven into saturation. The noise is described as whining, rumbling or rattling
and is louder and different than the normal hum of a transformer. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l2 level1 lfo3; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">c.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">Irregular
voltage and current wave shapes <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="color: #231f20; font-family: Arial, sans-serif;"><a href="http://www.powerqualityworld.com/2011/09/voltage-fluctuations-flicker.html">Flicker</a> is an example of this abnormality, which considerably affects
electronic devices - immediate failure and/or shortens expected life. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; margin-left: .25in; mso-list: l2 level1 lfo3; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">d.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;"> </span></span><span style="font-family: Arial, sans-serif;">Transformer
Overheating<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="color: #231f20; font-family: Arial, sans-serif;">In cases when the core is saturated repeatedly, the magnetic flux will
find reach the tank wall and other metallic components, which are portions of
the transformer where the flux is not expected. Heating can cause the bubbling or
charring of the paint on the top of the tank.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="color: #231f20; font-family: Arial, sans-serif;"><b>Reference: </b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">IEEE C57.105-1978. Guide for
Application of Transformer Connections in Three-Phase Distribution Systems<o:p></o:p></span></div>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com0tag:blogger.com,1999:blog-9173788893657603698.post-62271690075922488942012-01-29T05:25:00.000-08:002012-01-29T05:26:39.708-08:00POWER QUALITY BASICS: VOLTAGE NOTCHING<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Voltage Notching</b> is described by IEEE
as a recurring power quality disturbance due to the normal operation of power
electronic devices (i.e. rectifier), when current is commutated from one phase
to another. Conventionally, the current waveform is used as the starting point
for harmonic analysis, and voltage notching is simply derived from the IZ drops
of the harmonic currents. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br />
<a name='more'></a></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In addition, voltage notching
characterizes an unusual case that falls between <a href="http://www.powerqualityworld.com/2011/07/harmonics-power-quality-basics.html">harmonics</a> and <a href="http://www.powerqualityworld.com/2011/05/transients-power-quality-basics.html">transients</a>. This
is because notching takes place in steady-state, thus, it can be distinguished
by the harmonic spectrum of the affected voltage. On the other hand, the components
of the frequency related to voltage notching are somewhat high and may not be promptly
categorized with a measurement device commonly employed for harmonic analysis.</span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-MyeeLTdCtHU/TyVF_MDHaWI/AAAAAAAAAUM/a_S0P1jDZ-0/s1600/Voltage-Notching.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Voltage Notching" border="0" height="116" src="http://4.bp.blogspot.com/-MyeeLTdCtHU/TyVF_MDHaWI/AAAAAAAAAUM/a_S0P1jDZ-0/s320/Voltage-Notching.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">Voltage Notching</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;"><b>Sources</b></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Voltage Notching is primarily caused
by three-phase rectifiers or converters that generate continuous DC current. As
mentioned, the voltage notches happen when the current commutates from one
phase to another. Subsequently, a momentary short circuit between two phases
will occur during this period. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Moreover, the depth of the notch at
any point in the system is influenced by the source inductance, the isolating
inductance between the rectifier/converter, as well as the point being examined.
Consequently, the width of the notch is the commutation angle.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">µ = cos<sup>-1</sup>[cos α – (X<sub>s</sub>+X<sub>t</sub>)I<sub>dc</sub>]
- α <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">cos µ = 1 – (2E<sub>x</sub>/E<sub>do</sub>)<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">where:<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">µ = commutation angle<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">α = delay angle<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Xs = system reactance in per unit on
converter base<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Xt = converter transformer reactance
in per unit on converter base<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Idc = DC current in per unit on
converter base<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">E<sub>x </sub>= direct-voltage drop
caused by commutating reactance<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">E<sub>d0 </sub>= theoretical direct
voltage<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Effects and Solution</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Voltage Notches introduce harmonic and
non-harmonic frequencies that are much higher than those found in higher
voltage systems. Usually, these frequencies are in the radio frequency range, that cause negative operational effects, such as signal interference
introduced into logic and communication circuits. Also, when of sufficient
power, the voltage notching effect may overload electromagnetic interference filters, and other similar high-frequency sensitive capacitive circuits. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Furthermore, the solution for voltage
notching typically involves isolation of the critical and sensitive equipment
from the source (i.e. rectifiers) of the power quality problem.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Synopsis:</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Duration: Steady-state <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Source: Electronic Devices (e.g.
converters)<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Symptoms: Malfunction <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Occurrence: Very Low<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Mitigation: Isolation <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>References:</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">IEEE 519-1992. Recommended Practice
and Requirements for Harmonic Control in Electrical Power Systems<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">IEEE 1159-1995. Recommended Practice for
Monitoring Electric Power Quality<o:p></o:p></span></div>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com0tag:blogger.com,1999:blog-9173788893657603698.post-55523537164034467992011-12-31T22:52:00.000-08:002012-01-29T05:27:51.507-08:00EFFECTS OF HARMONICS TO ELECTRONIC EQUIPMENT<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The <b>Effects of Harmonics to Electronic
Equipment</b> are experienced in various ways depending on the type of device -
from slight to serious consequences. Ironically, it is a known fact that most electronic
equipment is prone to misoperation due to harmonic distortion, even though it
is a harmonic generator itself. In this post, these common effects will be
briefly discussed.</span><br />
<span style="font-family: Arial, sans-serif;"></span><br />
<a name='more'></a></div>
<b style="font-family: Arial, sans-serif; line-height: 150%; text-align: justify;">Power Electronic Equipment</b><br />
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">This equipment is reliant upon accurate
determination of voltage zero crossings or other facets of the voltage wave shape.
Unfortunately, <a href="http://www.powerqualityworld.com/2011/07/harmonics-power-quality-basics.html">harmonics</a> can shift the voltage zero crossing, or the point at
which one phase-to-phase voltage becomes greater than another phase-to-phase
voltage. These are both significant points for many types of electronic circuit
controls, and the unwanted shifts can lead to equipment misoperation.</span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-2GjZbZgjOZc/TwABOk8dw5I/AAAAAAAAATU/kmznkkDbGO4/s1600/Voltage-Zero-Crossing.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Voltage Zero Crossing" border="0" height="296" src="http://1.bp.blogspot.com/-2GjZbZgjOZc/TwABOk8dw5I/AAAAAAAAATU/kmznkkDbGO4/s400/Voltage-Zero-Crossing.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif;">Voltage Zero Crossing Point</span></td></tr>
</tbody></table>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif; line-height: 150%;"><b>Medical Instruments</b></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Malfunctioning medical instruments
present the most serious negative effect of harmonics to electronic devices. This
is because it may place a person’s life in jeopardy. For this reason, many
medical instruments are provided with line-conditioned power and protected by
proper power quality devices. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In addition, less dramatic
interference effects of harmonics can sometimes be observed in radio and
television equipment, as well as in video recorders and audio reproduction
systems.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Computers and Other Electronic Devices</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Computers and allied equipment like
programmable controllers typically require AC sources that have no more than a
5% harmonic voltage distortion factor, with the largest single harmonic being
no more than 3% of the fundamental voltage. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Harmonic distortion levels that exceed
standard limits may result to malfunctioning equipment, which in some cases,
have serious consequences. It must be noted that electronic devices can be
disturbed by the transmission of AC supply harmonics via the equipment power
supply or through magnetic coupling of harmonics into equipment components. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Moreover, other electronic instruments
can be affected by harmonics by giving incorrect data or unpredictable
performance (i.e. digital energy meters).<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Voltage Notching</b><o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Most electronic devices are installed
at the low voltage level of its associated power distribution system. As a
result, they also become exposed to the effects of <a href="http://www.powerqualityworld.com/2012/01/voltage-notching-power-quality-basics.html">voltage notching</a>. Voltage
notches often introduce frequencies, both harmonic and non-harmonic, which are
much higher than those exhibited in 5 kV and higher voltage distribution
systems. <o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Subsequently, these frequencies are in
the radio frequency (RF) range, which can lead into detrimental effects associated
with spurious RF, such as signal interference introduced into communication or
logic circuits. Sometimes, the voltage notching effect is of adequate power to
overload electromagnetic interference (EMI) filters and similar high-frequency
sensitive capacitive circuits.<o:p></o:p></span></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<br /></div>
<div class="MsoNoSpacing" style="line-height: 150%; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Reference:</b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">IEEE
519-1992. Recommended Practice and Requirements for Harmonic Control in
Electrical Power Systems<o:p></o:p></span></div>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com2tag:blogger.com,1999:blog-9173788893657603698.post-70131431401356847842011-11-02T07:12:00.000-07:002012-03-29T08:14:48.292-07:00DELTA CONVERSION ONLINE UPS<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Delta
Conversion Online UPS</b> is a modern innovation that eliminates the disadvantages of the traditional double conversion online UPS.
The enhancements are based on having a delta inverter and allowing
bidirectional power flow. Today, this design is the only major <a href="http://www.powerqualityworld.com/2011/04/uninterruptible-power-supply-ups.html" target="_blank">uninterruptible power supply</a> technology
protected by patents and is unlikely to be offered from a broad range of UPS
suppliers. Also, delta conversion online units are available in the market from
5 kVA to 1 MVA.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br />
<a name='more'></a></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Similarities
and Differences</b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>A. Components</b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The
delta conversion online UPS differs physically from the conventional design
because of two main components – the delta inverter and delta transformer.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><u>Delta
Inverter </u><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The
delta conversion online UPS has a so-called delta inverter, which is a
current-controlled IGBT Pulse Width Modulator (PWM) inverter. It performs two
major functions:<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">1. Input power and current regulation<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Delta
inverter acts like a variable current source in the secondary circuit of the
transformer, such that it works like a load without power dissipation (except
for switching losses). This active front end draws power that is sinusoidal and
in-phase with the source voltage. Consequently, current magnitude, wave shape and
power factor can be controlled. Thus, with a delta conversion online UPS, the
following can be achieved:<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<ul style="margin-top: 0in;" type="disc">
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l0 level1 lfo1; text-align: justify;"><span style="font-family: Arial, sans-serif;">Reduced heating and system wear in the electrical
power system.<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l0 level1 lfo1; text-align: justify;"><span style="font-family: Arial, sans-serif;">Minimized <a href="http://www.powerqualityworld.com/2011/07/harmonics-power-quality-basics.html">harmonics</a>.<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l0 level1 lfo1; text-align: justify;"><span style="font-family: Arial, sans-serif;">Optimal conditions for utility and generator
systems.<o:p></o:p></span></li>
</ul>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">2. Charge
the battery of the UPS <o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Delta
inverter converts AC voltage to the suitable DC charging voltage.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><u>Delta
Transformer</u><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The
delta transformers in a delta conversion online UPS are actually three
single-phase isolation transformers with one for each phase. Usually, these
transformers have a voltage ratio of 1:5 (primary:secondary). It also follows
that the current ratio is normally 5:1. <o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>B. Power
Flow</b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In a delta conversion online UPS, both the main and delta inverters are
bidirectional devices, such that they have the capability to transform AC power
to DC power, and at the same time DC power to AC power.</span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-hnldEQYaldg/TrFNi0nOzsI/AAAAAAAAAS0/75xLAUaLH4Y/s1600/Delta-Conversion-Online-UPS.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Delta Conversion Online UPS" border="0" height="235" src="http://2.bp.blogspot.com/-hnldEQYaldg/TrFNi0nOzsI/AAAAAAAAAS0/75xLAUaLH4Y/s400/Delta-Conversion-Online-UPS.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span class="Apple-style-span" style="font-family: Arial, Helvetica, sans-serif;">Delta Conversion Online UPS Block Diagram</span></td></tr>
</tbody></table>
<span class="Apple-style-span" style="font-family: Arial, sans-serif;">On the
other hand, the double conversion online UPS has only one power path. This is
because the rectifier/charger and the main inverter are unidirectional power
conversion devices. In such a case, first, the rectifier changes real AC power
(watts) to DC. Then, the main inverter transforms back DC power to AC, which is
supplied to the loads.</span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-Ye_bQ-vlYTY/TrFN_FcEoOI/AAAAAAAAAS8/K3zchePO1SA/s1600/Double-Conversion-Online-UPS.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Double Conversion Online UPS" border="0" height="320" src="http://4.bp.blogspot.com/-Ye_bQ-vlYTY/TrFN_FcEoOI/AAAAAAAAAS8/K3zchePO1SA/s320/Double-Conversion-Online-UPS.jpg" width="270" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span class="Apple-style-span" style="font-family: Arial, Helvetica, sans-serif;">Double Conversion Online UPS Block Diagram</span></td></tr>
</tbody></table>
<span class="Apple-style-span" style="font-family: Arial, sans-serif;">In
other words, both designs have similar fundamental functions, but the delta
conversion devices can perform improved functionality.</span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The delta conversion online UPS always has the inverter supplying the load during
normal conditions - which is the basic concept of an <a href="http://www.powerqualityworld.com/2011/05/online-ups.html">online UPS</a>. However, the
delta inverter also contributes power to the main inverter output. As a result,
it can deliver power to the loads with much greater efficiency than the double
conversion. Yet, under conditions of AC power disturbances, the delta
conversion online UPS functions just like the conventional design.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>C. Benefits</b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">The
delta conversion online UPS provides output characteristics that are similar to
the double conversion online design. Nonetheless, the former can control both
input and output power, which makes possible to gain the following benefits:<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<ul style="margin-top: 0in;" type="disc">
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l1 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Significant reduction in energy losses<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l1 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Makes the UPS compatible with all generator sets<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l1 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Reduces the need for wiring and generator oversizing<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l1 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Power Factor Correction<o:p></o:p></span></li>
</ul>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">To sum
up, the delta conversion online UPS is more efficient since it will directly
deliver power only the difference (delta) between the input and the output.
Under normal conditions, it bypasses the steps wherein AC power is converted to DC
(for battery charging), and transformed back to AC energizing the loads.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Reference:</b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">APC<o:p></o:p></span></div>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com0tag:blogger.com,1999:blog-9173788893657603698.post-27800223408933883552011-10-30T08:41:00.000-07:002011-10-30T08:43:43.837-07:00MOTOR-GENERATOR (M-G) SET FOR IMPROVED RIDE-THROUGH<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Motor-Generator
(M-G) set</b> is basically a combination of a motor and generator, although it is
physically different from an ordinary electric motor that is attached to a
separate generator. It has many practical functions that generally involve
converting voltage, frequency and phase of power. However, this post will focus
on its <a href="http://www.powerqualityworld.com/2011/03/what-is-power-quality.html" target="_blank">power quality</a> applications, as it is a mature technology used for
isolating sensitive and critical loads from <a href="http://www.powerqualityworld.com/2011/03/voltage-sags-dips-power-quality-basics.html">voltage sags</a> and <a href="http://www.powerqualityworld.com/2011/04/interruptions-power-quality-basics.html">interruptions</a>. Also,
it is available in various sizes and configurations to suit different purposes.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br />
<a name='more'></a></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Design
and Construction </b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">A motor-generator set
has both the rotor coils of the motor and generator wound around a single
rotor. In addition, both coils share the same outer magnets or field coils.
Usually, the motor coils are driven from a commutator on one end of the shaft,
while the generator coils output to another commutator on the other end of the
shaft. Generally, the entire shaft and rotor assembly is only slightly larger
in size than in a normal electric motor, and may not have any exposed drive
shafts.</span><span class="Apple-style-span" style="font-family: Arial, sans-serif;"> </span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-on1zPZfSBHs/Tq1sKN2ZMCI/AAAAAAAAASk/FtawouzFdvs/s1600/Motor-Generator.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Motor-Generator (M-G) Set" border="0" height="145" src="http://3.bp.blogspot.com/-on1zPZfSBHs/Tq1sKN2ZMCI/AAAAAAAAASk/FtawouzFdvs/s320/Motor-Generator.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span class="Apple-style-span" style="font-family: Arial, Helvetica, sans-serif;">Motor-Generator (M-G) Set</span></td></tr>
</tbody></table>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span class="Apple-style-span" style="font-family: Arial, sans-serif;">Another
kind of motor-generator utilizes a special synchronous generator called a
written-pole motor, which produces a constant 60-Hz frequency as the machine
slows. It is able to supply a constant output by continually changing the
polarity of the rotor’s field poles. Therefore, each revolution can have a
different number of poles than the previous one. As long as the rotor is spinning
at speeds between 3150 and 3600 revolutions per minute (rpm), constant output
is maintained. The inertia of the flywheel permits the generator rotor to keep
rotating at speeds above 3150 rpm once power shuts off. Normally, the rotor weight
creates enough inertia to keep it spinning fast enough to produce 60 Hz for 15
s under full load.</span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Operation
Principle </b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">A
motor supplied by the incoming line drives a generator, which powers the load. The
M-G set may contain a flywheel on the same shaft to provide greater inertia, and
subsequently improve ride-through time. When the line is subjected to voltage
sags and interruptions, the inertia of the machines and the flywheels maintains
the power supply for several seconds. This set-up may also be employed to
isolate sensitive and critical loads from other power quality problems such as
switching <a href="http://www.powerqualityworld.com/2011/05/transients-power-quality-basics.html">transients</a> and <a href="http://www.powerqualityworld.com/2011/07/harmonics-power-quality-basics.html">harmonic distortion</a>. Motor-generator sets also have
inherently superb resistance to <a href="http://www.powerqualityworld.com/2011/07/electrostatic-discharge-esd.html">electrostatic discharge (ESD)</a>.</span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-PkX7OdQini8/Tq1sj8aHQ9I/AAAAAAAAASs/RIYSAqzqktQ/s1600/Motor-Generator-Diagram.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Motor-Generator Diagram" border="0" height="183" src="http://1.bp.blogspot.com/-PkX7OdQini8/Tq1sj8aHQ9I/AAAAAAAAASs/RIYSAqzqktQ/s400/Motor-Generator-Diagram.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span class="Apple-style-span" style="font-family: Arial, Helvetica, sans-serif;">Motor-Generator Diagram</span></td></tr>
</tbody></table>
<span class="Apple-style-span" style="font-family: Arial, sans-serif;"><b>Other Applications
and Benefits</b></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In
addition, motor-generators have even been employed where the input and output
currents are basically the same. Consequently, the mechanical inertia of the
M-G set will filter out transients in the input power. The output's electric
current can become noise-free and shall be able to ride-through transients
and interruptions at the input to the motor-generator set. This may facilitate
the smooth cut-over from mains power to AC power provided by
a diesel generator set.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Motor-generator
sets have been replaced by semiconductor devices for some purposes. However,
they are still being preferred in industrial settings where harmonics removal, line
isolation and/or frequency conversion is required.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Moreover,
the motor-generator can deal with large short-term overloads better than modern
semiconductor devices of the same average load rating. This is because the
thermally current-limited components of M-G set are copper windings weighing
hundreds of kilograms, which are intrinsically attached to their own large
thermal mass. In contrast, large semiconductor inverters have solid-state
switches that have a few grams of mass with a thermal time constant to their
heat sinks of likely more than 100 milliseconds only. <o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Disadvantages</b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Motor-Generator
sets have disadvantages for some types of loads:<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<ol start="1" style="margin-top: 0in;" type="1">
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l0 level1 lfo1; text-align: justify;"><span style="font-family: Arial, sans-serif;">There are losses associated with the machines, although
they are not significantly larger than other technologies. <o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l0 level1 lfo1; text-align: justify;"><span style="font-family: Arial, sans-serif;">The frequency and voltage drop during interruptions
as the machine slows. This may not work well with some loads. <o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l0 level1 lfo1; text-align: justify;"><span style="font-family: Arial, sans-serif;">Noise and maintenance may be issues with some
installations.<o:p></o:p></span></li>
</ol>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Reference:</b><o:p></o:p></span></div>
<span style="font-family: Arial, sans-serif; line-height: 115%;">Dugan, R., McGranaghan, M., Santoso, S., and
Beaty, H.W. (2004). Electrical Power Systems Quality (2nd ed.).</span>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com2tag:blogger.com,1999:blog-9173788893657603698.post-19747807065482589902011-10-26T23:26:00.000-07:002011-11-02T07:29:52.123-07:00EMTP-RV: REFERENCE FOR POWER SYSTEM TRANSIENTS<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>EMTP-RV</b>
is a powerful and dedicated software for the simulation and analysis of
<a href="http://www.powerqualityworld.com/2011/05/transients-power-quality-basics.html" target="_blank">transients</a> in power systems. It provides an extensive variety of system
modeling capabilities covering electromagnetic and electromechanical
oscillations ranging in duration from microseconds to seconds. EMTP-RV is the
most comprehensive analysis and simulation program for power system transients.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br />
<a name='more'></a></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">EMTP-RV
has gained a reputation of being a super-fast computational engine that gives
improved solution methods for nonlinear models, user-defined models and control
systems. It also features a plug-in model interface, which allows users to add
their own models.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-6mFgca2gyuE/Tqjz3417wtI/AAAAAAAAASE/bNlt5uj45Ek/s1600/EMTP-RV.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="EMTP-RV" border="0" src="http://4.bp.blogspot.com/-6mFgca2gyuE/Tqjz3417wtI/AAAAAAAAASE/bNlt5uj45Ek/s1600/EMTP-RV.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span class="Apple-style-span" style="font-family: Arial, Helvetica, sans-serif;">EMTP-RV</span></td></tr>
</tbody></table>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span class="Apple-style-span" style="font-family: Arial, sans-serif;"><b><br /></b></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span class="Apple-style-span" style="font-family: Arial, sans-serif;"><b>Applications</b></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Generally,
EMTP-RV can be used in the analysis of insulation coordination, lightning and
switching surges, ferroresonance, power electronics applications (i.e. HVDC and
voltage source converters), shaft torsional oscillations, temporary <a href="http://www.powerqualityworld.com/2011/03/power-quality-basics-overvoltage.html">overvoltage</a>
and other power quality issues. <o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">In
other words, EMTP-RV is applicable to power system studies, whether they relate
to project design and engineering, or to solving problems and inexplicable
failures. It is the most technically advanced analysis software for the
simulation of a range of phenomena in areas such as:<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<ul style="margin-top: 0in;" type="disc">
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">General purpose circuit analysis: wideband, from
load-flow to steady-state initialization to time-domain<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Multiterminal HVDC systems<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Network analysis, which involve network separation,
<a href="http://www.powerqualityworld.com/2011/03/what-is-power-quality.html">power quality</a>, geomagnetic storms, interaction between compensation and
control components<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Power electronics<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Power system design<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Protection - saturation problems and power
oscillations and <a href="http://www.powerqualityworld.com/2011/05/surge-arresters.html">surge arrester</a> influences<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Renewable energy generation<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Series compensation: MOV energy absorption,
short-circuit conditions and network interaction<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Simulation and analysis of large
scale electrical systems<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Simulation and analysis of electrical system
transients<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Switchgear - TRV, current chopping, arc interaction,
delayed-current zero conditions and shunt compensation<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Synchronous machines: SSR, auto-excitation and
control<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Transient stability analysis<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Transmission line systems, including design, insulation
coordination, cable models, switching and wideband line<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l2 level1 lfo2; text-align: justify;"><span style="font-family: Arial, sans-serif;">Unbalanced distribution networks<o:p></o:p></span></li>
</ul>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>EMTP-RV
Studies </b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Furthermore,
studies that use EMTP-RV can be classified into:<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: .25in; margin-right: 0in; margin-top: 0in; mso-list: l1 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">1.<span style="font: normal normal normal 7pt/normal 'Times New Roman';">
</span></span><span style="font-family: Arial, sans-serif;">Design<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">This
includes:<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<ul style="margin-top: 0in;" type="disc">
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l3 level1 lfo3; text-align: justify;"><span style="font-family: Arial, sans-serif;">Control system design<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l3 level1 lfo3; text-align: justify;"><span style="font-family: Arial, sans-serif;">Equipment ratings<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l3 level1 lfo3; text-align: justify;"><span style="font-family: Arial, sans-serif;">Harmonic studies<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l3 level1 lfo3; text-align: justify;"><span style="font-family: Arial, sans-serif;">Insulation coordination<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l3 level1 lfo3; text-align: justify;"><span style="font-family: Arial, sans-serif;">Power quality assessment<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l3 level1 lfo3; text-align: justify;"><span style="font-family: Arial, sans-serif;">Protective device specification<o:p></o:p></span></li>
</ul>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: .25in; margin-right: 0in; margin-top: 0in; mso-list: l1 level1 lfo1; text-align: justify; text-indent: -.25in;">
<span style="font-family: Arial, sans-serif;">2.<span style="font: normal normal normal 7pt/normal 'Times New Roman';">
</span></span><span style="font-family: Arial, sans-serif;">Solving
Operating Problems<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<ul style="margin-top: 0in;" type="disc">
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l0 level1 lfo4; text-align: justify;"><span style="font-family: Arial, sans-serif;">Equipment failures<o:p></o:p></span></li>
<li class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; mso-list: l0 level1 lfo4; text-align: justify;"><span style="font-family: Arial, sans-serif;">Unexplained Outages<o:p></o:p></span></li>
</ul>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><b>Software
Package Inclusions</b><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Enhanced
and maintained by the Development Coordination Group (DCG), the EMTP-RV software
package also includes a very intuitive graphical user interface (EMTPWorks), a fully
reprogrammed computational engine and an advanced output processor.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><u>EMTPWorks</u><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">A
cutting edge and easy-to-use graphical user interface (GUI), which maximizes
the features and capabilities of the underlying EMTP-RV engine. EMTPWorks
offers drag-and-drop convenience allowing users to quickly design, modify and
simulate electric power systems. A drawing canvas and the ability to externally
program device data permit users to fully customize simulations to their needs.
It can be used for small systems or very large-scale systems.<o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><u>ScopeView</u><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;">Provides
waveform visualization and advanced mathematical post-processing capabilities.</span></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-3Bat8F8Y2yQ/Tqj2lGLoNpI/AAAAAAAAASM/1Cs4ACCzqp4/s1600/EMTP-RV-ScopeView.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="EMTP-RV ScopeView" border="0" height="275" src="http://1.bp.blogspot.com/-3Bat8F8Y2yQ/Tqj2lGLoNpI/AAAAAAAAASM/1Cs4ACCzqp4/s400/EMTP-RV-ScopeView.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span class="Apple-style-span" style="font-family: Arial, Helvetica, sans-serif;">EMTP-RV ScopeView</span></td></tr>
</tbody></table>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span class="Apple-style-span" style="font-family: Arial, sans-serif;"><b>Link:</b></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<span style="font-family: Arial, sans-serif;"><a href="http://www.emtp.com/?q=content/request-trial-license">Click here to request for EMTP-RV Demo</a><o:p></o:p></span></div>
<div class="MsoNormal" style="line-height: 150%; margin-bottom: .0001pt; margin-bottom: 0in; text-align: justify;">
<br /></div>
<span style="font-family: Arial, sans-serif; font-size: 9pt; line-height: 115%;"><b>Note:</b> Requests from students or from individuals
without organizational membership will not be considered (a professional email
address is required).</span>yepyephttp://www.blogger.com/profile/15301935748026280435noreply@blogger.com0