Electrical Engineering Tour

How Nuclear Power Plant Works ?

2012-12-12T20:15:00.000-08:00

Nuclear Energy Power Plant
The Potential Of Nuclear Energy

how a nuclear power plant works?
Why nuclear?, what is nuclear energy, nuclear and the environment, top 10 facts, learn more, nuclear glossary, the pressurized water reactor(PWR): containment structure, pressurizer, steam generator, control rods, reactor vessel, turbine, condenser, generator., boiling water reactor(BWR).
http://www.cleansafeenergy.org/CASEnergyClassroom/HowaNuclearPowerPlantWorks/tabid/170/Default.aspx

free download pdf site related to electrical and electronics engineering and many others

types of nuclear reactors
Boiling water reactor, boiling water reactor, pressurized water reactor, liquid metal fast breeder reactor, control rod structure, reactor core, feedwater pump, steam turbine, condenser. primary loop, secondary loop, primary liquid sodium cooling loop, intermediate liquid sodium cooling loop, water and steam loop to turbine.
http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/reactor.html

nuclear physics fission and fusion
Introduction to nuclear energy, with lecture and discussion : nuclear energy : chemistry analogy, binding energy. fission energy : reactions, resources, status. fusion energy : reactions, resources, wastes.
http://acdisweb.acdis.uiuc.edu:16080/NPRE201/coursematerial/nuclear_physics/lecture20.html

nuclear power reactors
Several components common to most types of reactors : fuel, moderator, control rods, coolant, pressure vessel of pressure tubes, steam generator, containment. several different types of reactors : pressurised water reactor, boiling water reactor, pressurised heavy water reactor, gas cooled reactor, light water graphite reactor, fast neutron reactor. floating nuclear power plants, primitive reactors, primary coolants, water, helium, carbon dioxide, sodium, lead, molten fluoride salt, heat transfer for different primary coolants, use of water for cooling.
http://www.uic.com.au/nip64.htm

the story of nuclear energy fission and fusion
Formula by famous scientist Albert Einstein, the equation says, Einstein's voice explaining. nuclear fission, nuclear fusion : deutrium, tritium, neutron, helium, energy.
http://www.energyquest.ca.gov/story/chapter13.html

video power plant tour
Take a virtual power plant tour, what you will need for the tour, tour tips, start the tour : view the entire tour from start to finish, start in the fuel section, start in the water section, start in the electricity section.
http://www.srpnet.com/education/tour/

inside a nuclear reactor
Controlling, coolant, fuel, moderator, shield, steam, electricity, test your knowledge.
http://schools.matter.org.uk/Content/NuclearReactor/NuclearReactorApplet.html

energy information administration
Nuclear power plants operating in the united states as of december 31, 2005, EIA data on reactors, EIA data on nuclear generation, nuclear and uranium forecasts, nuclear regulatory commission.
http://www.eia.doe.gov/cneaf/nuclear/page/at_a_glance/reactors/states.html

the virtual nuclear tourist, nuclear power plants around the world
Current hot topics, terrorism concerns, location, private spent fuel storage, russian enriched fuel, effects of low levels of radiation, transportation of nuclear waste, decommissioning of nuclear plants, reprocessingm advanced reactors, inside the nuclear power plants, US locations plant maps, plant status events assesment operational experience NRC plant assesments reactor oversight, sample preliminary safety analysis report, world locations plants, web searches for specific us power plants.
http://www.nucleartourist.com/

Pressurized Water Reactors
http://www.nrc.gov/reactors/pwrs.html

nuclear power plant operations
Reactor system, Pressurized Water Reactor System, Protective Barriers.
http://www.hsem.state.mn.us/HSem_view_Article.asp?docid=251&catid=3

All About Electrical Conductors Most Frequent Questions

2012-09-13T23:17:00.000-07:00

What is Conductor ac Resistance
A conductor offers a greater resistance to a flow of alternating current than it does to direct current. This increased resistance is generally expressed as the ac/dc resistance ratio. The two major factors for this increase are the skin effect and the proximity effect of closely spaced current carrying conductors. Other magnetic effects can also cause an additional increase in ac/dc resistance ratios.

What is Electric Fields and Voltage
Current flow is charge in motion. We might consider the simple case of a conductor carrying current out to a load and then a return conductor as two separated parallel cylinders of charge. If we neglect conductor diameter line of charge there are electric field lines represented by circles of diameters such that the center of the circles are on the 0 line and each circle passes through the center of the cylinders.

What is Conductor
Conductors may be solid or stranded. Metals used are commonly copper or aluminum. An attempt to use sodium was short-lived. The strand can be concentric, compressed,compacted, segmental, or annular to achieve desired properties of flexibility, diameter, and current density.

What is Circular Mil Sizes
Sizes larger than #4/0 AWG are specified in terms of the total cross-sectional area of the conductor and are expressed in circular mils. This method uses an arbitrary area of a conductor that is achieved by squaring the diameter of a solid conductor. This drops the π/4 multiplier required for the actual area of a round conductor. A circular mil is a unit of area equal to the area of a circle having a diameter of one mil, one mil equals 0.001
inch. Such a circle has an area of 0.7854 or π/4 square mils. Thus, a wire 10 mils in diameter has a cross-sectional area of 100 circular mils. Likewise, one square inch equals 4/π times 1,000,000=1,273,000 circular mils. For convenience, this is usually expressed in thousands of circular mils and abbreviated kcmil.

What is Non-Shielded Power Cable
A cable non-shielded cable may consist of one or several conductors and one or several
insulating layers. The cable may contain a jacket. The cable may also include a conductor
shield. A cable is not considered fully shielded until both conductor and insulation shields
are present. Non-shielded cables are common in the 0 to 5 kV voltage range although
non-shielded power cables through 8 kV have been available.

What is AIR INSULATED CONDUCTORS
A metallic conductor suspended from insulating supports, surrounded by air, and carrying electric signals or power may be considered as the simplest case of an insulated conductor.

What is INSULATING TO SAVE SPACE
Space is a common constraint that precludes the use of air as an insulator. Imagine the space requirements to wire a house or apartment using bare conductors on supports with air as the insulation. A voltage divider has been created that is made up of the impedance from the conductor to the outside covering surface and another impedance from the covering surface to ground. The distribution of voltage from conductor to the surface of the covering and from the covering surface to ground will be in proportion to these impedances.

What is RISING VOLTAGE
Return to the metallic conductor that is covered with an insulating material and suspended in air. When the ground plane is brought close or touches the covering,At low voltages, the effect is negligible. As the voltage increases, the point is reached where the potential gradients are sufficient to cause current to flow across the surface of the covering.

What is Electrical Insulation or Dielectric
The insulation dielectric provides sufficient separation between the conductor and the nearest electrical ground to adjacent phase to preclude dielectric failure. For low voltage cables, (2,000 volts and below), the required thickness of insulation to physically protect the conductor is more than adequate for required dielectric strength.

What is Jackets in a Condcutors
In low voltage applications, jackets are commonly used to protect underlying layers from physical abuse, sunlight, flame, or chemical attack. In medium voltage shielded cables chemical attack includes corrosion of underlying metallic layers for shielding and armoring. In multi-conductor designs, overall jackets are common for the same purposes. For medium and high voltage cables, jackets have been almost universally used
throughout the history of cable designs.

What is Medium Voltage Shielded Cables
Medium voltage cables generally are fully shielded having both conductor and insulation shield cables in the 5 kV through 35 kV voltage range.

What is Electric Field
Emphasis will be on 60Hz alternating current fields. In all cables, regardless of their kV ratings, there exists an electric field whenever the conductor is energized. This electric field can be visualized as electric field lines and lines of equipotential.

What is Equipotential Lines
Equipotential lines represent points of equal potential difference between electrodes having different electrical potentials.

What is Metric Designations
All of the world, except for North America, uses the SI unit of square millimeters (mm2) to designate conductor size. The International Electrotechnical Commission has adopted IEC 280 to define these sizes. An important consideration is that these are not precise sizes. For instance, their 50 mm2 conductor is actually 47 mm2. To accommodate everyone, the IEC standard allows as much as a 20% variation in conductor area from the size designated.

What is Skin Effect
In ac circuits, the current density is greater near the outer surface of the conductor. The current tends to crowd toward the outer surface. This is called skin effect. A longitudinal element of the conductor near the center of the axis is surrounded by more lines of magnetic force than near the rim. This results in an increase in inductance toward the center.

Electrical Power System Device Numbers and Acronyms By Alphabetical ANSI/IEEE

2012-09-03T05:40:00.000-07:00

In the design of electrical power systems, the ANSI Standard Device Numbers ANSI/IEEE Standard C37.2 denote what features a protective device supports such as a relay or circuit breaker. These types of devices protect electrical systems and components from damage when an unwanted event occurs, such as an electrical fault. Device numbers are used to identify the functions of devices shown on a schematic diagram. Function descriptions are given in the standard.
ANSI/IEEE C37.2-2008 is one of a continuing series of revisions of the standard, which originated in 1928.

List of device numbers and acronyms BY Alphabetical

ALARM RELAY 74
Is a relay other than an annunciator, as covered under device function 30, that is used to operate, or to operate in connection with, a visual or audible alarm.

ACCELERATING OR DECELERATING DEVICE - 18
Is a device that is used to close or to cause the closing of circuits which are used to increase or decrease the speed of a machine.

CIRCUIT BREAKER - 52
Is a device that is used to close and interrupt an a-c power circuit under normal conditions or to interrupt this circuit under fault of emergency conditions.

ATMOSPHERIC CONDITION MONITOR - 45
Is a device, that functions upon the occurrence of an abnormal atmospheric condition, such as damaging fumes, explosive mixtures, smoke or fire.

ANNUNCIATOR RELAY - 30
is a non-automatically reset device that gives a number of separate visual indications of the functions of protective devices, and which may also be arranged to perform a lockout function.

AUTOMATIC SELECTIVE CONTROL OR TRANSFER RELAY - 83
Is a relay that operates to select automatically between certain sources or conditions in a equipment, or performs a transfer operation automatically.

AUXILIARY MOTOR OR MOTOR GENERATOR - 88
Is one used for operating auxiliary equipment, such as pumps, blowers, exciters, rotating magnetic amplifiers, etc.

A-C RECLOSING RELAY - 79
Is a relay that controls the automatic reclosing and locking out of an a-c circuit interrupter.

APPARATUS THERMAL DEVICE - 26
is a device that functions when the temperature of the shunt field or the amortisseur winding of a machine, or that of a load limiting or load shifting resistor or of a liquid or other medium, exceeds a predetermined value: or if the temperature of the protected apparatus, such as a power rectifier, or of any medium decrease below a predetermined value.

ANODE CIRCUIT BREAKER - 7
Is a device used in the anode circuits of a power rectifier for the primary purpose of interrupting the rectifier circuit if an arc-back should occur.

A-C DIRECTIONAL OVERCURRENT RELAY - 67
Is a relay that functions on a desired value of a-c over-current flowing in a predetermined direction.

BLOCKING RELAY - 68
Is a relay that initiates a pilot signal for blocking of tripping on external faults in a transmission line or in other apparatus under predetermined condition, or cooperates with other devices to block tripping or to block re-closing on an out-of-step condition or on power savings.

BRUSH-OPERATING OR SLIPPING SHORT-CIRCUITING DEVICE - 35
Is a device for raising, lowering, or shifting the brushes of a machine, or for short-circuiting its slip rings, or for engaging or disengaging the contacts of a mechanical rectifier.

BEARING PROTECTIVE DEVICE - 38
Is a device that functions on excessive bearing temperature, or on another abnormal mechanical conditions associated with the bearing, such as undue wear, which may eventually result in excessive bearing temperature.

CARRIER OR PILOT-WIRE RECEIVER RELAY - 85
is a relay that is operated or restrained by a signal used in connection with carrier-current or d-c pilot-wire fault directional relaying.

CHECKING OR INTERLOCKING RELAY - 3
is a relay that operates in response to the position of a number of other devices (or to a number of predetermined conditions) in an equipment, to allow an operating sequence to proceed, or to stop, or to provide a check of the position of these devices or of these conditions for any purpose.

CONTROL POWER DISCONNECTING DEVICE - 8
is a disconnecting device, such as a knife switch, circuit breaker, or pull-out fuse block, used for the purpose of respectively connecting and disconnecting the source of control power to and from the control bus or equipment.

D-C CIRCUIT BREAKER - 72
is a circuit breaker that is used to close and interrupt a d-c power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions.

DIFFERENTIAL PROTECTIVE RELAY - 87
is a protective relay that functions on a percentage or phase angle or other quantitative difference of two currents or of some other electrical quantities.

DIRECTIONAL POWER RELAY - 32
is a device that functions on a desired value of power flow in a given direction or upon reverse power resulting from arcback in the anode or cathode circuits of a power rectifier.

D-C RECLOSING RELAY - 82
is a relay thast controls the automatic closing and re-closing of a d-c circuit interrupter, generally in response to load circuit conditions.

D-C OVERCURRENT RELAY - 76
is a relay that function when the current in a d-c circuit exceeds a given value.

DISTANCE RELAY - 21
is a relay that functions when the circuit admittance, impedance, or reactance increases or decreases beyond predetermined limits.

EQUALIZER CIRCUIT BREAKER - 22
is a breaker that serves to control or to make and break the equalizer or the current-balancing connections for a machine field, or for regulating equipment in a multiple -unit installation.

EXCITER OR D-C GENERATOR RELAY - 53
is a relay that forces the d-c machine field excitation to build up during starting or which functions when the machine voltage has been built up to a given value.

FIELD APPLICATION RELAY - 56
is a relay that automatically controls the application of the field excitation to an a-c motor at some predetermined point in the slip cycle.

FIELD-CHANGING CONTACTOR - 93
is a contactor that functions to increase or decrease, in one step, the value of field excitation on a machine.

FREQUENCY RELAY - 81
is a relay that functions on a predetermined value of frequency (either under or over or on normal system frequency) or rate of change of frequency.

FIELD RELAY - 40
is a relay that functions on a given or abnormally low value or failure of a machine field current, or on excessive value of the reactive component of armature current in an a-c machine indicating abnormally low field excitation.

FLAME DETECTOR - 28
is a device that monitors the presence of the pilot or main flame of such apparatus as a gas turbine or a steam boiler.

FIELD CIRCUIT BREAKER - 41
is a device that functions to apply or remove the field excitation of a machine.

GOVERNOR - 65
is the assembly of fluid, electrical, or mechanical control equipment used for regulating the flow of water, steam, or other medium to the prime mover for such purposes a starting, holding speed or load, or stopping.

GROUND PROTECTIVE RELAY - 64
is a relay that functions on failure of the insulation of a machine, transformer, or of other apparatus to ground, or on flashover of a d-c machine to ground.

HIGH-SPEED D-C CIRCUIT BREAKER - 54
is a circuit breaker which starts to reduce the current in the main circuit in 0.01 second or less, after the occurrence of the d-c overcurrent or the excessive rate of current rise.

ISOLATING CONTACTOR - 29
is a device that is used expressly for disconnecting one circuit from another for the purposes of emergency operation, maintenance, or test.

INCOMPLETE SEQUENCE RELAY - 48
is a relay that generally returns the equipment to the normal, or off, position and locks it out if the normal starting, operating, or stopping sequence is not properly completed within a predetermined time. If the device is used for alarm purposes only, it should preferably be designated as 48A (alarm).

INSTANTANEOUS OVERCURRENT OR RATE -OF-RISE RELAY - 50
is a relay that functions instantaneously on an excessive value of current or on an excessive rate of current rise, thus indicating a fault in the apparatus

or circuit being protected.

LIQUID OR GAS FLOW RELAY - 80
is a relay that operates on given values of liquid or gas flow or on given rates of change of these values.

LOCKING-OUT RELAY - 86
is an electrically operated hand, or electrically reset relay or device that functions to shut down or hold an equipment out of service, or both, upon the occurrence of abnormal conditions.

LIQUID OR GAS PRESSURE OR VACUUM RELAY - 63
is a relay that operates on given values of liquid or gas pressure or on given rates of change of these values.

LINE SWITCH - 89
is a switch used as a disconnecting, load-interrupter, or isolating switch in an a-c or d-c power circuit, when this device is electrically operated or has electrical accessories, such as an auxiliary switch, magnetic lock, etc.

LIQUID OR GAS-LEVEL RELAY - 71
is a relay that operates on given values of liquid or gas level or on given rates of change of these values.

LOAD-RESISTOR CONTACTOR - 73
is a contactor that is used to shunt or insert a step of load limiting, shifting, or indicating resistance in a power circuit, or to switch a space heater in circuit, or to switch a light or regenerative load resistor, a power rectifier, or other machine in and out of circuit.

MECHANICAL CONDITION MONITOR - 39
is a device that functions upon the occurrence of an abnormal mechanical condition (except that associated with bearing as covered under device function 38), such as excessive vibration, eccentricity, expansion shock, tilting, or seal failure.

MASTER ELEMENT - 1
is the initiating device, such as a control switch, voltage relay, float switch, etc., which serves either directly or through such permissive devices as protective and time-delay relays to place an equipment in or out of operation.

MANUAL TRANSFER OR SELECTOR DEVICE - 43
Is a manually operated device that transfers the control circuits in order to modify the plan of operation of the switching equipment or of some of the devices.

MASTER CONTACTOR - 4
is a device generally controlled by device function 1or the equivalent and the required permissive and protective devices, that serves to make and break the necessary control circuits to place an equipment into operation under the desired conditions and to take it out of operation under other or abnormal conditions.

MASTER SEQUENCE DEVICE - 34
is a device such as a motor-operated multi-contact switch, or the equivalent, or programming device, such as a computer, that establishes or determines the operating sequence of the major devices in a equipment during starting and stopping or during other sequential switch operations.

MACHINE OR TRANSFORMER THERMAL RELAY - 49
is a relay that functions when the temperature of a machine armature
or other load-carrying winding or element of a machine or the temperature of a power rectifier or power
transformer (including a power rectifier transformer) exceeds a predetermined value.

NOTCHING OR JOGGING DEVICE - 66
is a device that functions to allow only a specified number of operations of a given device or equipment, or a specified number of successive operations within a given time of each other. It is also a device that functions to energize a circuit periodically or for fractions of specified time intervals, or that is used to permit intermittent acceleration or jogging of a machine at low speeds for mechanical positioning.

OVER-SPEED DEVICE - 12
is usually a direct-connected speed switch which functions on machine over-speed.

POSITION CHANGING MECHANISM - 75
is a mechanism that is used for moving a main device from one position to another in an equipment: as for example, shifting a removable circuit breaker unit to and from the connected, disconnected, and test positions.

PULSE TRANSMITTER - 77
is used to generate and transmit pulses over a telemetering or pilot-wire circuit to the remote indicating or receiving device.

PHASE-ANGLE MEASURING OR OUT-OF-STEP PROTECTIVE RELAY - 78
is a relay that functions at a pre-determined phase angle between two voltages or between two currents or between a voltage and current.

POSITION SWITCH - 33
is a switch that makes or breaks contact when the main device or piece of apparatus which has no device function number reaches a given position.

POWER FACTOR RELAY - 55
is a relay that operates when the power factor in an a-c circuit rises above or falls below a predetermined value.

SHORT-CIRCUITING OR GROUNDING DEVICE - 57
is a primary circuit switching device that functions to short-circuit or to ground a circuit in response to automatic or manual means.

OPERATING MECHANISM - 84
is the complete electrical mechanism or servomechanism, including the operating motor, solenoids, position switches, etc., for a tap changer, induction regulator, or any similar piece of apparatus which otherwise has no device function number.

OVERVOLTAGE RELAY - 59
is a relay that functions on a given value of over-voltage.

POLARITY OR POLARIZING VOLTAGE DEVICE - 36
is a device that operates, or permits the operation of, another device on a predetermined polarity only, or verifies the presence of a polarizing voltage in an equipment.

PERMISSIVE CONTROL DEVICE - 69
is generally a two-position, manually-operated switch that, in one position, permits the closing of a circuit breaker, or the placing of an equipment into operation, an in the other position prevents the circuit breaker or the equipment from being operated.

PHASE-SEQUENCE VOLTAGE RELAY - 47
is a relay that function upon a predetermined value of polyphase voltage in the desired phase sequence.

RHEOSTAT - 70
is a variable resistance device used in an electric circuit, which is electrically operated or has other electrical accessories, such a auxiliary , position, or limit switches.

REGULATING DEVICE - 90
is a device that functions to regulate a quantity, or quantities, such as voltage, current power, speed, frequency, temperature, and load at a certain value or between certain (generally close) limits for machines, tie lines, or other apparatus.

RECTIFICATION FAILURE RELAY - 58
is a device that functions if one or mote anodes of a power rectifier fail to fire, or to detect and arc-back or on failure of a diode to conduct or lock properly.

TIME DELAY STARTING OR CLOSING RELAY - 2
is a device that functions to give a desired amount of time delay before or after any point of operation in switching sequence or protective relay system, except as specifically provided by service function 48, 62, and 79.

STOPPING DEVICE - 5
is a control device used primarily to shut down an equipment and hold it out of operation. (This device may be manually or electrically actuated, but excludes the function of electrical lockout [see device function 86] on abnormal conditions.)

STARTING CIRCUIT BREAKER - 6
is a device whose principal function is to connect a machine to its source of starting voltage.

REVERSING DEVICE - 9
is a device that is used for the purpose of reversing a machine field or for performing any other reversing functions.

RUNNING CIRCUIT BREAKER - 42
is a device whose principal function is to connect a machine to its source of running or operation voltage. This function may also be used for a device, such as a contactor, that is used in series with a circuit breaker or other field protecting means, primarily for frequent opening and closing of the breaker.

RESERVED FOR FUTURE APPLICATION - 16

RESERVED FOR FUTURE APPLICATION - 11

(USBR assigned – Control Power Transformer).

RESERVED FOR FUTURE APPLICATION - 24
(USBR assigned – bus tie circuit breaker, contactor, or switch.)

REVERSE PHASE OR PHASE BALANCE CURRENT RELAY - 46
is a relay that functions when the polyphase currents are of reverse-phase sequence, or when the polyphase currents are unbalanced or contain negative phase-sequence components above a given amount.

RESERVED FOR FUTURE APPLICATION. - 61

STARTING-TO-RUNNING TRANSITION CONTACTOR
is a device that operates to initiate or cause the automatic transfer of a machine from the starting to the running power connection.

SEPARATE EXCITATION DEVICE - 31
is a device that connects a circuit, such as the shunt field of a synchronous converter, to a source of separate excitation during the starting sequence; or one that energizes the excitation and ignition circuits of a power rectifier.

SYNCHRONIZING OR SYNCHRONISM-CHECK DEVICE - 25
is a device that operates when two a-c circuits are within the desired limits of frequency, phase angle, or voltage, to permit or to cause the paralleling of these two circuits

SYNCHRONOUS-SPEED DEVICE - 13
is a device such as a centrifugal switch, a slip-frequency relay, a voltage relay, and undercurrent relay , or any type of device that operates at approximately the synchronous speed of a machine.

SPEED OR FREQUENCY MATCHING DEVICE - 15
is a device that functions to match and hold the speed or frequency of a machine or of a system equal to, or approximately equal to, that of another machine, source, or system.

SHUNTING OR DISCHARGE SWITCH - 17
is a switch that serves to open or to close a shunting circuit around any piece of apparatus (except a resistor, such as a machine field, a machine armature, a capacitor, or a reactor).

TRIPPING OR TRIP-FREE RELAY - 94
is a relay that function to trip a circuit breaker, contactor or equipment, or to permit immediate tripping by other devices; or to prevent immediate re -closure of a circuit interrupter if it should open automatically even though its closing circuit is maintained closed.

TEMPERATURE CONTROL DEVICE - 23
is a device that function to raise or lower the temperature of a machine or other apparatus, or of any medium, when its temperature falls below, or rises
above, a predetermined value.

TIME-DELAY STOPPING OR OPENING RELAY - 62
is a time-delay relay that serves in conjunction with the device that initiates the shutdown, stopping, or opening operation in an automatic sequence or
protective relay system.

TIME OVERCURRENT RELAY - 51
Is a relay with either a definite or inverse time characteristic that functions when the current in an a-c circuit exceed a predetermined value.

UNIT SEQUENCE SWITCH - 10
is a switch that is used to change the sequence in which units may be placed in and out of service in multiple-unit equipments.

UNDERVOLTAGE RELAY - 27
is a relay that functions on a given value of under-voltage.

UNDER-SPEED DEVICE - 14
is a device that functions when the speed of a machine fall below a pre -determined value.

UNDERCURRENT OR UNDERPOWER RELAY - 37
is a relay that function when the current or power flow decreases below a predetermined value.

UNIT SEQUENCE STARTING RELAY - 44
is a relay that function to start the next available unit in a multiple-unitequipment upon the failure or non-availability of the normally preceding unit.

VOLTAGE OR CURRENT BALANCE RELAY
is a relay that operates on a given difference in voltage, or current input or output, or two circuits.

VOLTAGE DIRECTIONAL RELAY - 91
is a device which operates when the voltage across an open circuit breaker or contactor exceeds a given value in a given direction.

VOLTAGE AND POWER DIRECTIONAL RELAY - 92
is a relay that permits or causes the connection of two circuits when the voltage difference between them exceed a given value in a predetermined direction and causes these two circuits to be disconnected from each other when the power flowing between them exceeds a given value in the opposite direction.

VALVE - 20
is one used in a vacuum, air, gas, oil, or similar line, when it is electrically operated or has electrical accessories such as auxiliary switches.

How A Prime Movers Works In An Electic Power Plant

2012-08-26T20:46:00.001-07:00

Electrical Power Plant today is more important than any other, that is because without those power plant operate we cannot do anything. From manufacturing plant, because we are all depend on Electricity. So therefore it a high time to know from the very beginning what is a prime movers, how it works or what is
all about. To get the plant started, prime movers are typically Diesel Engines, Gas or Steam Turbines, or Hydro and Wind Turbines. This Prime movers converts oil, gas, coal, wood, uranium, water, wind, etc. into mechanical energy. The mechanical energy is supplied to the shaft of the generator and the generator in turn transform this mechanical energy to electrical energy. High quality electric power generating systems deliver precise voltage and frequency. The voltage regulator as noted earlier, provides the precise voltage regulation. The prime mover GOVERNOR, by accurately controlling the speed, provides the precise frequency regulation.

What is a Governor?
Govers Define as a device which controls the speed or power of a prime mover in order to convert the power to useful work.When the governor senses the speed of a prime mover and controls the prime mover to maintain its speed (or load) at a desired output.Like for example if you drive a car. You function as a governor when you control the car’s speed under a varying driving conditions. The driver adjust the accelerator that controls the fuel to maintain the desired speed at a certain level and adjust from time to time should the desired speed varies. Acutually the original governors were entirely mechanical like a pair of centrifugal flyweights in most ballheads. It is known for its ruggedness, usefulness and sensitivity. The
flyweights are rotated by a drive from the prime mover that is directly related to the speed. As the speed changes, the flyweights move out at the top due to centrifugal force. The centrifugal action causes the weights to increase the force on the thruster that control the pilot valve thereby changing the speed of the prime mover due to applying or removing load.

What a Governor Does?
As the prime mover gets started or a speed of about 25%, a governor mechanism “comes to life”. The governor senses the prime mover rotation and begins to regulate the linkages controlling the fuel/steam supply of the prime mover.But if the prime mover tends to increase speed above the set speed of the governor, the governor mechanism decreases the controlling lever opening of the fuel/steam supply of the prime mover.Eventually, the prime mover speed will be controlled so that only enough fuel/steam is being admitted, (power in) to hold the prime mover approximately the speed setting of the governor.

What Happens as Load is Added to the System?
As the customer load demand increases, the generator must supply the load instantaneously. The generator slows down as more power is being taken out from the generator than what is being produced. But as soon as the shaft slows down, the governor mechanism senses and causes to increase the fuel/steam rack opening it and increasing fuel/steam supply of the prime mover.The power produced by the prime mover will increase to match the generator demand. As the speed will be a little less than before, since if the speed recover completely, the governor mechanism senses and causes to increase the fuel rack opening increasing
power for the prime mover. Therefore, the frequency of the AC produced by the generator will get lower as the generator slows down and load increases. What is a Governor Speed Setting Does? The speeder spring is the part that sets the “desired speed”. Applying more force down on the speeder spring causes the governor to increase fuel/steam supply to the prime mover. This initial force is usually set by the operator for the desired or “reference’ speed. It can be set by an adjusting screw, a knob, a lever, a DC electric motor, an air pressure, or solenoids, depending on the specific governor.

How to Adjust the Governor Setting?To Keep frequency constanct, need to operate governor speed setting mechanism to reaise the no-load speed setting, compensating for the droop in speed with
load

Characteristics Of Power Line Electrical Conductors Facts and Tables

2012-08-21T00:15:00.001-07:00

We usually used ACSR wire for primary and neutral line while we used AAC All Aluminun Conductor wire for secondary line. And most common size of wire that we used is no. 2 acsr wire to be used for rural electrification or small and large industrial and 336.4 acsr for mainline/feeder line. For secondary line we used always #2 aac wire that is for rural or residential household. But for the specific conductor designated transformers like 100 KVA we used 336.4 aac, 50 KVA 4/0 aac wire, 2/0 aac wire for 25 KVA wire and #2 aac wire for 10 kva transformer for service drop only.

All-aluminum conductor (AAC)
Aluminum grade 1350-H19 AAC
has the highest conductivity-to-weight ratio of all overhead conductors.

Aluminum conductor, steel reinforced (ACSR)
Because of its high mechanical strength-to-weight ratio, ACSR has equivalent or higher ampacity for the same size conductor (the kcmil size designation is determined by the cross-sectional area of the aluminum; the steel is neglected). The steel adds extra weight, normally 11 to 18% of the weight of the conductor. Several different strandings are available to provide different strength levels. Common distribution sizes
of ACSR have twice the breaking strength of AAC. High strength means the conductor can withstand higher ice and wind loads. Also, trees are less likely to break this conductor.

All aluminum alloy conductor (AAAC)
This alloy of aluminum, the 6201-T81 alloy, has high strength and equivalent ampacities of AAC or ACSR. AAAC finds good use in coastal areas where use of ACSR is prohibited because of excessive corrosion.

Aluminum Conductor, Alloy Reinforced (ACAR)
Strands of aluminum 6201-T81 alloy are used along with standard 1350 aluminum. The alloy strands increase the strength of the conductor. The strands of both are the same diameter, so they can be arranged in a variety of configurations.

Characteristics of All Aluminum Conductors (AAC)

Characteristics of Aluminum Conductors, Steel Reinforced (ACSR)

Characteristic of Steel Conductors

Types of Electrical Testing Equipment Instruments Uses and Its Definition

2012-08-10T01:59:00.002-07:00

Meter Testing Instrument in the field of electrical engineering or in electronics engineering is so importantwithout those instrument you cannot repair or analyze the system or equipmnent or even design a new one. As I googling on the Net I discovered that huge of instrument testing for as to know as an electrical engineer. Like Cable-Length Meters, Electric Tachometer, Electrical Thermometers, Footcandle Meter, Frequency Meter, Miscellaneous Testing Instruments and many others.

Cable-Length Meters
Cable-length meters measure the length and condition of a cable by sending a signal down the cable and
then reading the signal that is reflected back. These instruments are also called time-domain reflectometers
TDRs. A similar instrument used to measure the length of fiber optic cables is called an optical timedomain
reflectometer ODTR.

Electric Tachometer
This consists of a small generator that is belted or geared to the equipment whose speed is to be measured.
The voltage produced in the generator varies directly with the rotational speed of the generator.
Since this speed is directly proportional to the speed of the machine under test, the amount of the generated
voltage is a measure of the speed.

Electrical Thermometers
For the measurement of temperatures, there are three basic types of electrical thermometers.Resistance thermometers operate on the principle that the resistance of a metal varies in direct proportion to its temperature. They are normally used for temperatures up to approximately 1500°F.Thermocouples operate on the principle that a difference in temperature in different metals generates a voltage, and are used for measuring temperatures up to about 3000°F. Radiation pyrometers and optical pyrometers are generally used for temperatures above 3000°F. They combine the principle of the thermocouple with the effect of radiation of heat and light.

Footcandle Meter
A footcandle meter consists of a photosensitive element and a meter that indicates the average illumination of a room or other space in footcandles. Typical footcandle meters can read light intensity from 1 to
500 footcandles or more. To use the footcandle meter, first remove the cover. Hold the meter in a position so the cell is facing toward the light source and at the level of the work plane where the illumination is required. The shadow of your body should not be allowed to fall on the cell during tests. A number of such tests at various points in a room or area will give the average illumination level in footcandles. Readings are taken directly from the meter scale.

Frequency Meter
Frequency is the number of cycles completed each second by a given AC voltage, usually expressed in
hertz ; 1 Hz = 1 cycle per second. The frequency meter is used with AC powerproducing devices like generators to ensure that the correct frequency is being produced. Failure to produce the correct frequency can result in overheating and component damage.

Miscellaneous Testing Instruments
Ammeters, voltmeters, and megohmmeters are the most common analog devices used for field testing
and troubleshooting applications. However, several other specialized types of test instruments should be mentioned briefly.

Power Factor Meter
Power factor is the ratio of the true power,voltamperes to apparent power,watts, and it depends on the phase difference between current and voltage. Three-phase power factor meters are installed in
switchboards. Many utilities charge large commercial and industrial users a penalty if power factor falls
below 90 percent; so these users try to maintain high power factor at all times. A high power factor provides better voltage regulation and stability.

Power Quality Analyzers
Power quality analyzers are portable test instruments similar in construction to the digital multimeters.
unlike DMMs, which typically measure only one property of electrical circuits at a time, power quality analyzers have dual probes that allow both voltage and current to be measured simultaneously. Power quality analyzers can also measure frequency and harmonics. The ability to measure Power quality analyzer display showing voltage on top, current on bottom, and time stamp at upper right. and display multiple circuit characteristics at the same time is useful in troubleshooting power quality problems in power distribution systems.

Photo Tachometer
This instrument aims a light at the rotating shaft on which there is a contrasting color such as a mark, a chalk line, or a light-reflective strip or tape. The rotational speed in rpm is read from an indicating scale. Photo tachometers are especially useful on relatively inaccessible rotational equipment such as motors,
fans, grinding wheels, and other similar machines where it is difficult, if not impossible, to make contact
with the rotational unit.

Phase-Sequence Indicator
A common phase-sequence indicator is designed for use in conjunction with any multimeter that can
measure AC voltage. Most can be used on circuits with line voltages up to 550 VAC, provided the instrument used with the indicator has a rating this high. To use the phase-sequence indicator, set the multimeter to the proper voltage range. This can be determined if it is not known by measuring the line voltage before connecting the phase-sequence indicator. Next, connect the two black leads of the indicator
to the voltage test leads of the meter. Connect the red, yellow, and black adapter leads to the circuit in
any order and check the meter for a voltage reading. If the meter reading is higher than the original circuit voltage measured, then the phase sequence is black-yellow-red. If the meter reading is lower than the original circuit voltage measured, then the phase sequence is red-yellow-black. If the reading is the
same as the first reading, then one phase is open.

Tachometers
A tachometer is a device that indicates or records the speed of rotating equipment (motors and generators) in revolutions per minute,rpm. There are several different types:

Vibrating-reed Tachometer
This instrument is simply held against the motor, turbine, pump, compressor, or other rotating equipment, and the speed is shown by the vibration of a steel reed, which is tuned to a certain standard
speed.

WHAT IS Electrical Power System Quality With Terms and Definitions

2012-07-27T02:29:00.000-07:00

Listed below is the most important terms you should know before studying about electrical power system quality.

What is..

Aswell
is defined as an increase to between 1.1 and 1.8 pu in rms voltage or current at the power frequency for durations from 0.5 cycle to 1 min. DC Offset is defined of the presence of a dc voltage or current in an ac power system

Harmonics
are sinusoidal voltages or currents having frequencies that are integer multiples of the frequency at which the supply system is designed to operate termed the fundamental frequency; usually 50 or 60 Hz.

Interharmonics
is a Voltages or currents having frequency components that are not integer multiples of the frequency at which the supply system is designed to operate e.g., 50 or 60 Hz

Impulsive Transient
is a sudden, non–power frequency change in the steady-state condition of voltage, current, or both that is unidirectional in polarity primarily either positive or negative.

Interruption
is occurs when the supply voltage or load current decreases to less than 0.1 pu for a period of time not exceeding 1 min. Long-duration variation is encompass root-mean-square rms deviations at power frequencies for longer than 1 min. Notching is a periodic voltage disturbance caused by the normal operation of power electronic devices when current is commutated from one phase to another.

Noise
is defined as unwanted electrical signals with broadband spectral content lower than 200 kHz superimposed upon the power system voltage or current in phase conductors, or found on neutral conductors or signal lines.

Oscillatory Transient
is a sudden, non–power frequency change in the steady-state condition of voltage, current, or both, that includes both positive and negative polarity values.

Overvoltage
is an increase in the rms ac voltage greater than 110 percent at the power frequency for a duration longer than 1 min.

Power frequency variations
are defined as the deviation of the power system fundamental frequency from it specified nominal value e.g., 50 or 60 Hz.

Sustained Interruption
is When the supply voltage has been zero for a period of time in excess of 1 min in which a long-duration voltage variation is considered.

Short-duration voltage variations
are caused by fault conditions, the energization of large loads which require high starting currents, or intermittent loose connections in power wiring.

Sag
is a decrease to between 0.1 and 0.9 pu in rms voltage or current at the power frequency for durations from 0.5 cycle to 1 min.

Transients
has long been used in the analysis of power systemvariations to denote an event that is undesirable and momentary in nature.

Undervoltage
is a decrease in the rms ac voltage to less than 90 percent at the power frequency for a duration longer than 1 min.

Voltage Imbalance
or is also called voltage unbalance this is sometimes defined as the maximum deviation from the average of the three-phase voltage or currents, divided by the average of the three-phase voltages or currents, expressed in percent.

Voltage fluctuations
are systematic variations of the voltage envelope or a series of random voltage changes, the magnitude of which does not normally exceed the voltage ranges specified by ANSI C84.1 of 0.9 to 1.1
pu.

Waveform distortion
is defined as a steady-state deviation from an ideal sine wave of power frequency principally characterized by the spectral content of the deviation.

Power Transformer Guidelines When Making Internal Inspections

2012-07-10T02:55:00.001-07:00

Power Transformer Guidelines When Making Internal Inspections and Free Download pdf Ebook

1. Before climbing on the transformer, remove anything that may contaminate it and cause it to fail when energized: Remove all especially metal items from pockets and other loose items such as watches and rings. Wipe shoes clean of mud, stones, and other foreign material. Put clean disposable booties over shoes prior to entering the transformer. Attach lines to tools used in tank or near open manhole so that they cannot accidentally be dropped in the transformer.

2. Check the gasket of a power transformer before replacing the manhole covers.

3. For strick compliance no one should enter confined spaces for repair without prior authorization and review of applicable Company safety rules and General Safety Procedures for Confined Space Entry.

4. Do not permit the coils and insulation to be exposed to the air. You should lower the oil to the top of the core and coil assembly. Oil must be passed through an approved filter system. For oil-filled units power transformer.

5. Do not open transformers during periods of fog or precipitation or when relative humidity exceeds limits outlined in the manufacturer’s instruction book. If no value is specified in the instruction book, use a limit of 75%.

6. After sealing the transformer,unless it is the open type, it should be pressurized with dry nitrogen and purged until oxygen content is less than 1%.

7. It is advisable to check always the oxygen content before you entry and also monitor while you are inside the power transformer tank. Just be sure that the acceptable level of the oxygen is 19.5 percent.

8. Maintain a flow of dry air through the tank while it is open to help keep the insulation dry.If the core and coils are not covered with oil.

9. Do not allow transformer to stand open any longer than is necessary because of its tendency to absorb moisture from the air.

10. You should wear the proper attire during installation or repair of a power transformer.

Free Download

Instructions Manual
Installation, Operation, and Maintenance of Medium Power Substation Transformers, Although all transformers, components, and accessories
are carefully inspected and tested prior to shipment, a thorough receiving inspection should be conducted to detect any damage or loss that might have occurred during shipment.

An Important OverView about Power Transformers for Electrical
Transformer is the most important unit in an electrical distribution network. All transformers are subjected to thorough tests at the manufacturer’s works before despatch to the destination of erection.Due to limitations in transport, large capacity transformers are dis-assembled into various components before despatch.

Transformers Basics, Maintenance, and Diagnostics
Transformers have been used at powerplants since the inception of
alternating-current generation, a century ago. While operating
principles of transformers remain the same, the challenges of
maintaining and testing transformers have evolved along with
transformer design and construction.

TRANSFORMER INSTALLATION MANUAL
The purpose of this Instruction Manual is to provide guidance on the installation, commissioning and
maintenance of oil-filled transformers. This guide is necessarily general in nature.

What is the working principle of a transformer Questions and Answers

2012-06-22T06:17:00.000-07:00

20 Questions :

1. If a transformer is not marked, how could you test it for polarity?
2. A 10-kVA rating, that are connected in a closed delta arrangement, you would have a capacity of 30
K VA. If one transformer is taken out of the bank, what would be the output capacity of the remaining 10
K VA transformers?
3. When connecting transformers in parallel, what factors must be taken into consideration?
4. What is a split-coil transformer?
5. Where may autotransformers be used?
6. What is the purpose of the markings on transformer leads?
7. In a bank of three single-phase transformers that are connected in a delta, each transformer delivers 240 volts at 10 amperes. What are the line voltages and line currents?
8. If you have a bank of three single-phase transformers that are connected in a closed delta arrangement, and one transformer burns up, how would you continue operation on the remaining two transformers?
9. What special precaution must be taken when using a booster transformer?
10. What is a three-phase transformer?
11. If transformers with different electrical characteristics are connected in parallel, what will happen?
12. Describe a current transformer.
13. What precautions must be taken when working with current transformers? Why?
14. What is an induction regulator?
15.Is it possible to connect two single-phase transformers to secure a three-phase output from a three-phase input?
16. When connecting an ordinary transformer as a booster transformer, what important factors must be considered?
17. When you use a bank of two single-phase transformers in an open delta arrangement, do they supply their full output rating?
18. How are current transformers rated?
19. Describe a potential transformer.
20. What is the phase relation between the three phases of a three-phase circuit?

Answers Above Questions:

1.Connect the transformer as shown in Figure 6-7. If it has subtractive polarity, V will be less than the voltage of the power source; if it has additive polarity, V will be greater than the voltage of the power source.
2.Each transformer would deliver 8.66 kVA, and you would have a bank capacity of 17.32 k VA.
3.Their electrical characteristics, such as voltage ratio, impedance percentage, and voltage regulation.
4.A transformer that has the coils on the low or high side in separate winding's so that they can be connected in series or parallel for higher or lower voltages, as desired.
5.(a) Where the system being supplied contains an identified grounded conductor that is solidly connected to a similar identified
6.They are there for standardization, so that transformer polarities are recognizable for any type of use.
7.The line voltages are each equal to 240 volts; however, the line current in each phase would be the current of each transformer multiplied by 1.732 (the square root of 3), or 17.32 amperes.
8.By merely disconnecting the leads to the disabled transformer.
9.There must be no fusing in the high side, or primary. Because the booster transformer is similar to a current transformer, an extremely high voltage could be built up on the secondary side if the fuse should blow.
10.A transformer that is the equivalent of three single-phase transformers, which are all wound on one core and enclosed within one common case.
11.They won’t distribute the load equally; one transformer will tend to assume more of the load than the other. This leads to overheating and, in severe cases, the destruction of the transformers.
12.A current transformer has a primary of a few turns of heavy conductor capable of carrying the total current, and the secondary consists of a number of turns of smaller wire. The primary winding is connected in series with the circuit carrying the current that is to be measured.
13.The secondary must never be opened when the primary circuit is energized. If it is necessary to disconnect an instrument while the circuit is energized, the secondary must be short-circuited. If the secondary is opened while the circuit is energized, the potential on the secondary might reach dangerously high values. By short-circuiting the secondary, damage is avoided and the voltage on the secondary is kept within safe limits.
14.This device is similar to a booster transformer. It has a primary and a secondary winding, which are wound on separate cores. The primary can be moved in either direction; this is usually done by an electric motor. In turning, the primary bucks or boosts the line voltage, as required. The amount of bucking or boosting is anticipated by the current being drawn by the line.
15.Yes, they would have to be connected in an open delta.
16.The high side of the transformer must be able to handle the approximate voltage of the line; the low side must have a voltage of approximately the value by which you wish to boost the line voltage and must also have a current capacity that is sufficient to carry the line current.
17.No. Each transformer is only capable of supplying 86.6 percent of its output rating.
18.They are rated at 50 to 5, 100 to 5, etc. The first number is the total current that the transformer is supposed to handle, and the second figure is the current on the secondary when the fullloadcurrent is flowing through the primary. For example, a 50- to-5 rating would have a multiplier of 10 Kilo.
19.A potential transformer is built like the ordinary isolation transformer, except that extra precautions are taken to ensure that the winding ratios are exact. Also, the primary winding is connected in parallel with the circuit to be measured.
20.They are 120 electrical degrees apart.

Transformer Principles Questions and Answers For Engineering Students and Workers

2012-06-08T03:47:00.000-07:00

QUESTIONS:

1. What is the difference between the primary and the secondary of a transformer?
2. What is an oil-immersed transformer?
3. What is a transformer?
4. What factors affect the amount of induced electromotive force emf in a transformer?
5. Why is oil used in a transformer?
6. Is it possible to connect two single-phase transformers to secure a three-phase output from a three-phase input?
7. What is an air-core transformer?
8. What are eddy currents?
9. What means can be taken to keep eddy currents at a minimum?
10. Is hysteresis objectionable?
11. Are transformers normally considered to be efficient devices?
12. What factors constitute the major losses produced in transformers?
13. There are two basic types of transformers. What are they?
14. Is there a definite relationship between the number of turns and voltages in transformers?
15. What are instrument transformers?
16. Ordinarily, what is the phase relationship between the primary and secondary voltages of a transformer?
17. Is it possible to have the primary and secondary of a transformer in phase?
18. How are the leads of a transformer marked, according to ANSI (American National Standards Institute)?
19. What is mutual inductance?
20. What is a booster transformer?

ANSWERS:

1. The primary of the transformer is the input side of the transformer and the secondary is the output side of the transformer. On a step-down transformer, the high-voltage side is the primary and the low-voltage side is the secondary; on a step-up transformer, the opposite is true
2. The core and coils are immersed in a high-grade mineral oil, which has high dielectric qualities.
3. A device that transforms electrical energy from one or more circuits to one or more other circuits at the same frequency but usually at a different voltage and current. It consists of a core of soft-iron laminations surrounded by coils of copper-insulated wire.
4. The strength of the magnetic field, the speed at which the conductors are cut by the magnetic field, and the number of turns of wire being cut by the magnetic field.
5. To increase the dielectric strength of the insulation, to keep down the possibility of arcing between coils, and to dissipate heat to the outer case so that the transformer can carry heavier loads without excessive overheating.
6. Yes, they would have to be connected in an open delta.
7. A transformer that does not contain oil or other dielectric
compositions but is insulated entirely by the winding insulations and air.
8. Circulating currents induced in conductive materials (usually
the iron cores of transformers or coils) by varying magnetic
fields.
9. The iron used in the core of an alternation-current transformer
is laminated, or made up of thin sheets or strips of iron,
so that eddy currents will circulate only in limited areas.
10. Yes, it is a loss and affects the efficiency of transformers.
11. Yes, they have one of the highest efficiencies of any electrical device.
12. Power loss of the copper I2R losses, eddy currents, and hysteresis losses.
13. The isolation type, in which the two windings are physically isolated and electrically insulated from each other, and the autotransformer type, in which there is only one coil with a tap or taps taken off it to secure other voltages the primary is part of the secondary and the secondary is part of the primary.
14. Yes, the voltage varies in exact proportion to the number of turns connected in series in each winding.
15. In the measurement of current, voltage, or kilowatt-hours on systems with high voltage or high current, it is necessary to use a device known as an instrument transformer, which reproduces in its secondary circuit the primary current or voltage while preserving the phase relationship to measure or record at lower voltages
or lower amperages, and then to use a constant to multiply the readings to obtain the actual values of voltage or current. Current transformers CTs are used to measure the current, and potential transformers PTs are used to register the potential.
16. They are 180º out of phase.
17. Yes, by changing the connections on one side of the transformer.
18. The high side of the transformer is marked H1, H2, etc. The low side of the transformer is marked X1, X2, etc.
19. The linkage of flux between two coils or conductors, caused by the current flowing within one or both of the coils or conductors.
20. A transformer arrangement that is often used toward the end of a power line in order to raise the voltage to its desired value. These are often called “Buck-boost” transformers.

The History and Inventor of Nuclear Power plant

2012-05-17T03:25:00.001-07:00

In 100 BC an Alexandrian Greek speaking philosopher by the name of Ctesibius
invented the piston - pump.
In 1606, Italian scientist Giovanni Batista della Porta of Naples heated water in a flask until the water turned into steam.

In the 1600's several scientists continued work on steam powered pumps. Robert Boyle proposed the steam engine in 1678.

In 1680's a gunpowder explosion was used to heat water. Jean de Hautefeuille tried to up water, and Dutch astronomer Christiaan Huygens tried a piston in a

cylinder.

In 1712, Thomas Newcom and John Calley built their first successful steam engine.

In 1769 Nicholas Cugnot built the first mechanically propelled road vehicle

In 1789 Uranium was discovered by Martin Klaproth, a German chemist, and named after the planet Uranus.

In 1895 Ionising radiation was discovered by Wilhelm Rontgen by passing an electric current through an evacuated glass tube and producing continuous X-rays.
In 1896 Henri Becquerel found that pitchblende an ore containing radium and uranium caused a photographic plate to darken. He went on to demonstrate that

this was due to beta radiation electrons and alpha particles helium nuclei being emitted.
In 1896 Pierre and Marie Curie gave the name 'radioactivity' to this phenomenon.
In 1898 isolated polonium and radium from the pitchblende. Radium was later used in medical treatment.
In 1898 Samuel Prescott showed that radiation destroyed bacteria in food.
In 1902 Ernest Rutherford showed that radioactivity as a spontaneous event emitting an alpha or beta particle from the nucleus created a different element.

He went on to develop a fuller understanding of atoms.

In 1905 This was the first experimental confirmation of Albert Einstein's paper putting forward the equivalence between mass and energy, which had been

published.

In 1919 he fired alpha particles from a radium source into nitrogen and found that nuclear rearrangement was occurring, with formation of oxygen.
Niels Bohr was another scientist who advanced our understanding of the atom and the way electrons were arranged around its nucleus through to the 1940s.

In 1911 Frederick Soddy discovered that naturally-radioactive elements had a number of different isotopes radionuclides, with the same chemistry.
In 1911, George de Hevesy showed that such radionuclides were invaluable as tracers, because minute amounts could readily be detected with simple instruments.

In 1932 James Chadwick discovered the neutron.
In 1932 Cockcroft and Walton produced nuclear transformations by bombarding atoms with accelerated protons.

In 1934 Irene Curie and Frederic Joliot found that some such transformations created artificial radionuclides.
The next year Enrico Fermi found that a much greater variety of artificial radionuclides could be formed when neutrons were used instead of protons.

In January 1939 Frisch then confirmed this figure experimentally
1939 developments sparked activity in many laboratories. Hahn and Strassman showed that fission not only released a lot of energy but that it also released additional neutrons which could cause fission in other uranium nuclei and possibly a self-sustaining chain reaction leading to an enormous release of energy.

In 1900 Work on radioactive minerals found in central Asia began
Enrico Fermi (1901-1954), an Italian American physicist who won the 1938 Nobel Prize in Physics .
Otto Hahn (1879-1968), a German physical chemist who won the 1944 Nobel Prize in Chemistry.
Enrico Fermi (1901-1954), an Italian American physicist who won the 1938 Nobel Prize in Physics Otto Hahn (1879-1968), a German physical chemist who won the

1944 Nobel Prize in Chemistry Lise Meitner (1878-1968), an Austrian Swedish physicist Hyman G. Rickover (1898-1986), a Polish American naval officer

Discovering Fission Nuclear fission involves the splitting of an atomic nucleus, leading to the release of large amounts of energy. Nuclear fission was discovered in Germany in 1938 by Otto Hahn after he had bombarded uranium with neutrons and observed traces of radioactive barium. Meitner and her nephew, Otto Robert Frisch, were able to calculate the enormous energy that would be released in this type of reaction. They published their

results early in 1939. Nuclear fission was quickly verified in several laboratories.
Danish physicist Niels Bohr soon demonstrated that the rare uranium 235 (U-235) isotope is much more likely to fission than the common uranium 238 (U-238) isotope, which makes up 99.3 percent of natural uranium.

In 1909 St Petersburg Academy of Sciences began a large-scale investigation
1917 Revolution gave a boost to scientific research and over 10 physics institutes were established in major Russian towns, particularly St Petersburg, in the years which followed.

In the 1920s and early 1930s many prominent Russian physicists worked abroad, encouraged by the new regime initially as the best way to raise the level of expertise quickly. These included Kirill Sinelnikov, Pyotr Kapitsa and Vladimir Vernadsky.

In 1931 Kirill Sinelnikov returned from Cambridge to organise a department at the Ukrainian Physico-Technical Institute FTI in Kharkov which had been set up in 1928.

In 1933 became the Department of Nuclear Physics under Kurchatov with four separate laboratories.
In 1940 saw great advances being made in the understanding of nuclear fission including the possibility of a chain reaction. At the urging of Kurchatov and his colleagues, the Academy of Sciences set up a "Committee for the Problem of Uranium" in June 1940 chaired by Vitaly Khlopin

In June 1942 the US Army took over process development, engineering design, procurement of materials and site selection for pilot plants for four methods of making fissionable material.

In August 1943 an agreement was finally signed by Mr Churchill and President Roosevelt in Quebec.
In December 1951 The first nuclear reactor to produce electricity (albeit a trivial amount was the small Experimental Breeder reactor (EBR-1) in Idaho, in

the USA, which started up.

In October, 1956 It began producing about 90 megawatts of electric power.
In December 2, 1957, on the fifteenth anniversary of the first controlled nuclear chain reaction, the Shippingport Atomic Power Station in Shippingport,

Pennsylvania, became the first full-scale commercial nuclear power plant in the United States.

In September, 1959 The Dresden Nuclear Power Station, completed by Commonwealth Edison.
In 1973, forty-two plants were in operation producing 26,000 megawatts, fifty more were under construction, and about one hundred were on order.
In 1986, more than one hundred nuclear power plants were operating in the United States, producing about 60,000 megawatts of power.

In December 1993, the total number of nuclear power plants in the United States is 109, collectively producing 610 billion kWhs of electricity.

10 Largest Nuclear Power Plants In The World

2012-05-10T07:37:00.000-07:00

1. Kashiwazaki-Kariwa Nuclear Power Plant 8,212 Mega Watts

Niigata prefecture, Japan

Towns of Kashiwazaki and Kariwa

Has seven nuclear reactors.

The station is about 220 km northwest of Toyko

The plant, owned by Tepco, was built in 1985

2. Uljin Nuclear Power Plant 6,157 Mega Watts

Gyeongsangbuk-do province, South Korea

Has six nuclear reactors have been built to withstand 6.5 magnitude earthquakes

3. Yonggwang Atomic Energy Plant 6,137 Mega Watts

Yonggwang, South Korea

Has six nuclear reactors that each produce over 900 megawatts of power.

The plant, which began operation in 1978

4. Zaporizhzhia Atomic Energy Plant 6,000 Mega Watts

Enerhodar, Ukraine

The plant has six generators that The world’s worst nuclear disaster. About 400 times more radiation than the atomic bomb dropped over Hiroshima during World War II.

5. Gravelines Nuclear Power Plant 5,706 Mega Watts

Gravelines, France

The six reactors came online between 1980 and 1984 and the plant recently completed quite a milestone

It generated its 1000 billionth kilowatt hour of energy.

Local fish farmers use the water that carries waste heat from the plant to help raise European sea bass and other fish.

The warm water helps the fish grow faster.

6. Paluel Nuclear Power Plant 5,528 Mega Watts

Normandy, France

The second largest of its kind in France with four reactors that generate over 1,300 megawatts of power each hour.

The rest of the country’s nuclear stations are located away from the coast and get their cooling water from rivers.

About 11 of the 15 inland plants have evaporative cooling towers to lessen the need for fresh water.

7. Cattenom Nuclear Power Plant 5,448 Mega Watts

Cattenom, France

The station is owned by Electricite de France (EDF),Europe’s biggest power generator and the world’s second biggest utility company.

In April, about 2,000 people protested outside the site along with thousands across the country over the dangers of nuclear power.

France is one of the largest consumers of nuclear power, with 75 percent of its electricity coming from the source.

8. Bruce Nuclear Power Plant 5,090 Mega Watts

Inverhuron & Tiverton, Canada

The largest nuclear plant in North America.

The station takes up 2,300 acres near Lake Huron in Ontario.

It has eight nuclear reactors, but only six are operational.

The company is on track to restart the other two reactors by 2012, adding another 1,500 megawatts of power to the station. Once all eight are operational, the station will become the world’s second largest nuclear plant by capacity.

9. Oi Nuclear Power plant 4,710 Mega Watts

Fukui prefecture, Japan

Owned by Kansai Electric Power Company (KEPCO)

One of Japan’s largest utilities.

The plant houses four nuclear reactors that each generate over 1,000 megawatts of power per hour.

KEPCO has come under fire in the past for incidents at its nuclear plants.

In 2004, five employees were killed at its Mihama nuclear plant from a burst of steam, which was blamed on neglected safety checks.

In 2006, two employees were also injured in a plant fire.

10. Fukushima Daiichi 4,696 Mega Watts

Okuma, Japan

The world’s 10th largest nuclear station before Japan’s catastrophic earthquake and tsunami.

The plant started operations in 1971 and has six nuclear reactors, which were badly damaged on March 11.

Tepco had planned two more reactors at the site, but the company now plans to abandon these and scrap the site entirely.

Most of the reactors are old boiling water reactors (BWR) based on a GE design.

In February, Tepco admitted to the Japanese nuclear safety agency that it had submitted false inspection and safety reports.

Nuclear Power Plant Advantages and Disadvantages

2012-04-23T02:52:00.000-07:00

What Are Advantage and Disadvantages of Nuclear Power Plant

Advantages of A Nuclear Power Plant
1. Breeder reactors create more usable fuel than they use.
2.A nuclear aircraft carrier can circle the globe continuously for 30 years on its original fuel while a diesel fueled carrier has a range of only about 3000 miles before having to refuel.
3.Current nuclear waste in the US is over 90% Uranium. If reprocessing were made legal again in the US we would have enough nuclear material to last hundreds of years.
4.They can be sited almost anywhere unlike oil which is mostly imported.
5.Almost 0 emissions (very low greenhouse gas emissions.
6.A single nuclear reactor can produce a substantial amount of power. A nuclear reactor produces much more power per unit weight of nuclear fuel than conventional energy sources like coal and oil. The production of nuclear power does not release carbon dioxide into the atmosphere and hence does not contribute to global warming.
7.Nuclear power plants don't take up much space. This allows them to be placed in already developed areas and the power does not have to be transferred over long distances.
8.Nuclear power plants already exist and are available worldwide. So in comparison to, for example, nuclear fusion, the technology does not have to be developed first.
9.Another advantage of nuclear power is that nuclear energy is by far the most concentrated form of energy, so it can be produced in large quantities over short periods of time.
10.Nuclear power generation does emit relatively low amounts of CO2. Nowadays global warming because of the greenhouse gases is a hot topic. The contribution of nuclear power to global warming is relatively little.

Disadvantages of A Nuclear Power Plant
1.Mishaps at nuclear plants can render hundreds of square miles of land uninhabitable and unsuitable for any use for years, decades or longer, and kill off entire river systems
2.Early nuclear research and experimentation has created massive contamination problems that are still uncontained. Recently, for instance, underground contamination emanating from the Hanford Nuclear Reservation in Washington State in the U.S. was discovered and threatens to contaminate the Columbia River
3.Nuclear plants are more expensive to build and maintain.
4.Nuclear reactors are particularly vulnerable to terrorist attacks. The construction cost of a nuclear reactor is high. It takes a significantly long time to construct nuclear plants. At present, the reserves of uranium, a critical nuclear fuel, are limited in the world. Nuclear plant workers may be exposed to high levels of radiation, which can cause cancer and other ailments.
5.Nuclear reactors only last for about forty to fifty years, so where they are extremely productive, they break down and are costly to replace.
6.It is a high risk power supply. Of course a nuclear power plant has a very high security standard, but it is impossible to build a plant with a 100% security. We all know what horrible consequences there will be if an error or accident occurs in this plant.
7.A nuclear meltdown can often occur which will release massive amounts of radiation into the community.
8.nuclear energy can create more problems than they solve. Nuclear mishaps do not happen very often, but when they do, it creates a catastrophe that can damage the country and surrounding area for years to come.
9.The technology used for generating nuclear power can also be used for producing nuclear weapons. The country of North Korea is a classic example of this. The technology still does not exist to use nuclear power in relatively smaller devices like automobiles.
10.These plants also consume large amounts of water, which can damage marine life and affect the wildlife population in the area.

Free PDF Download Advantages and Disadvantages
Energy & the Environment
Advantages Nuclear fuel does not make harmful greenhouse gases. You only need a very small amount of nuclear fuel to make a lot of energy Disdvantages The waste that is produced when using nuclear fuel is radioactive and very harmful. It needs to be disposed of carefully Nuclear power stations are at risk from terrorist attack and sabotage. World uranium supplies may run out in about 50 years.

Free Download The Danger of Nuclear Power Plant

2012-04-06T18:13:00.000-07:00

The Risk and Danger of Nuclear power plant should everyone know why? because its affects in the human race, our health, our family etc. by way of teaching or learning I have here list of a free download pdf file from different site.
A dangerous waste of time greenpeace
The nuclear power industry is attempting to exploit the climate crisis by aggressively promoting nuclear technology as a “low-carbon” means of generating electricity. Nuclear power claims to be safe,
cost-effective and able meet the world’s energy needs. But nothingcould be further from the truth.

Understanding radiation
Radioactive materials are composed of atoms that are unstable. An unstable atom gives off its excess energy until it becomes stable. The energy emitted is radiation. Radiation has a cumulative effect. The longer a person is exposed to radiation, the greater the risk.

Nuclear Facts
Despite the fact that a national global warming emissions cap-and-trade system would materially assist the economic case for nuclear power, the nuclear industry has not been willing to openly advocate for such a system.

Nuclear Power Plant Security
Physical security at nuclear power plants involves the threat of radiological sabotage adeliberate act against a plant that could directly or indirectly endanger public health and safety through exposure to radiation.

Natural Disasters and Safety Risks
A typical nuclear power station will be connected to the electric grid through three or more transmission lines. Should these power lines go down or a regional electrical grid collapse occur, onsite emergency generators diesel, gas turbines or in few cases hydroelectric dams are designed to automatically start with manual
backup capability.

Radiation Risks and Realities
These findings allow us to use radioactive materials for beneficial purposes, such as generating electricity and diagnosing and treating medical problems. For these many benefits, excessive radiation exposure can also threaten our health and the quality of our environment.

The Tolerability of Risk
But in fact many people are bothered about nuclear power and other industrial risks and have become more so during the years since Sir Frank Layfield wrote his report.

How Does Electric Tractions Works? Question and Answer

2012-03-30T03:59:00.000-07:00

Electric Traction Theory
Steam Locomotive, Diesel Engines, Electric traction, Advantages, Electrical transmission, which is usually applied to high power units, has following advantages, The Direct and Alternating Current.

what is electric traction?
electric Traction means to use electic motors for railway service, Act of drawing or being drawn is known as traction.If electric supply is used for driving a locomotive, the system is known as electric traction.Electric traction may be A.C. or D.C. powered.e.g.600V dc is given to tramways and trolley buses.

ELECTRIC TRACTION
The electric locomotive and electric motor coach may be regarded as natural developments that have followed steam traction. New conditions have set new standards in railway travel. This is exemplified in the rapid development of electric suburban train services for the new built-up areas spreading in all directions round large cities.

Electric Traction Drives
This page describes the way electric motors on locomotives and multiple units drive the axles and wheels. See also the Electronic Power, Multiple Unit Operation, DC Traction Motor Systems and Electric Traction Glossary pages.

Answer tips/answer samples of What is electric traction?
Electric traction systems use DC motors, but nowadays, some people tend to use magnetic traction instead of electric ones.

ELECTRIC TRACTION FOR AUTOMOBILES - Free PDF download
a comparison concerning electric traction drives for passenger cars is given. Electric traction drives presently available on the market are analyzed and future developments are described.

Power Supply Installation in Electric Traction - Free PDF download
The book on "Power Supply Installation in Electrical Traction" was brought out by Institution of Railway Electrical Engineers (IREE) long back. Since, lot of changes have taken place in the field of Power Supply Installation, it has become necessary to incorporate the changes in this volume. Few additions and modifications in the field of Power Supply Installations are included in this book.

Question and Answer of Electric Traction

1. Overall efficiency of steam locomotive system is close to answer 5 to 10 percent
2. Maximum horse power of steam locomotive is answer 1500
3. The efficiency of diesel locomotives is nearly answer20 to 25 percent
4. The range of horsepower for diesel locomotives is 1500 to 2500
5. What motor is used in tramways? answer DC series motor
6. The advantages of electric braking is It prevents wear of track
7. What is the braking system on the locomotives answer Regenerative breaking on electric locomotives
8. What is the coefficient of adhesion highest? when answer the rails are dry
9. The estimated speed of the train, including the time of stop at a station, in addition to the actual running time between stops, is called its answer Schedule speed
10. Which of the following types of services consume the least specific energy? Main line service
11. Locomotives have two bogies with two driving axles with individual drive motors.
12. A composite system is made up of answer single phase power received is converted into DC or three phase power AC system
13. For 600 volts DC line for tram cars what is the correct voltages Track are connected to negative of the supply
14. Free running and coasting periods are generally long in case of which of the following services? answer Main line service
15. A train runs at an average speed of 50 kmph between stations situated 2.5 km apart. The train accelerates at 2 kmph and retards at 3 kmph. Speed time curve may be assumed to be trapezoidal. The maximum speed with these parameters will be answer 57.75kmph
16. Suri transmission is answer Hydro mechanical
17. When a locomotive for Indian Railways is designed as WAMI, what does the letter W indicate? answer The locomotive is to run on broad gauge track
18. The main differece between speed time curve of main line service as compared to suburban services lies in answer longer free running periods, longer coasting periods and shorter acceleration and braking periods

Transformer Built In Protection and Cooling Tutorials

2012-03-18T03:35:00.000-07:00

Protection Devices Built In For Safe Operation of A Transformer

Conservator

It is a sort of a drum, mounted on the top of transformer. A level indicatoris fixed to it. Conservator is connected through a pipe to the transformer containing oil. This oil expanse and contracts depending upon the heat produced so the oil level in the conservator rises and falls. Pipe connected to the conservator is left open to the atmosphere through a breather so that extra air any go out or come in.

Breather

Is is a box containing calcium chloride to absorb moisture of air entering the conservator as it sis well known fact that the insulating property of the transformer oil is lost even if a small amount of moisture enters in it, so the dry air is allowed to pass in through this breather.

Temperature Gauge

It is fitted to a transformer which indicates the temperature of transformer oil.Explosion Vent

It protects the transformer tank from the gases induced by any type of short circuit in the transformer.

Pipes

These are fitted for cooling the transformer oil. The hot oil circulates through these pipes where it becomes cool due to the air touching.

Important Facts About Transmission and Distribution Transformer

1. Eddy current losses in a transformer are minimised by laminating the core, the lamination being insulated from each other by a light coat of core plate varnish.

2. The basic property of the transformer is that it changes the voltage level of an alternating current signal without changing power, frequency or shape.

3. The primary and secondary voltages are 180 degree out of phase in transformer.

4. Eddy current lossesin transformer core are reduced by decreasing the thickness of laminations.

5. The resistance of low voltage side of a transformer is less than the resistance of its high voltage side.

6. The efficiency of a transformer is normally in the range of ninety ot ninety eight percent.

7. The reactance of transformer is determined by its leakage flux.

8. The principle of working of a transformer is mutual induction.

9. Transformer is used to change the valuesof voltage.

10. The path of the magnetic flux in a transformer has low reactance.

11. Electric power is transformed from one coil to the other coil in a transformer magnetically.

12. Ideal transformer assumptions do not include zero reactance of windings.

13. Preferably, the resistance between the primary and the secondary of a transformer should be as low as possible.

14. The main function of the iron core in a transformer is to decrease the reluctance of the magnetic path.

15. Magnetic circuit is common in the two windings of a transformer.

16. A transformer operates at power factor depending on the power factor of the load.

17. The lamination are made from nickel alloy steel stampings.

18. The steel for construction of transformer core is made so as to have high permeability and low hysteresis.

19. The special silicon stell in used for laminations because hysteresis losses are reduced.

20. Power transformer are designed to have maximum efficiency at near full load.

Cooling Of Transformer

Natural Cooling

The cooling is provided through natural circulation of air. The surface area of the core and the transformer winding are sufficient to dissipate the heat generated. It is used for small transformer from ten kva to fifteen kva.

Natural Oil Cooling

The transformer is placed in tank filled with oil known as transformer oil. The oil used in the tank not only helps cooling the transformer but also provides insulating for the winding. The oil takes the heat produced by the transformer, the oil circulate through the pipes and tank. The hot oil becomes lighter in weight and goes up from where comes down through pipes to the bottom of the tank after cooling. The oil level should never fall below the upper ends of pipes.

Oil Blast Cooling

In this method radiator tanks are provided to the side walls of the main tank. The oil circulators through these radiators from the main tank. The radiator tanks are cooled by air blast. The system of cooling is known as oil blast type. It is used for transformer rated above five hundred kva.

Force Water Cooling

The winding of transformer is placed inside the tank containing oil and cold water is passed through the copper pipe spiral kept in the transformer oil. The cold water absorbs and carrier away the heat of the oil. The pressure of the water is not kept greater than the pressure of the oil in the tank because in case of leakage in the pipe, the water will enter into the oil. It is used for transformer having output greater than five hundred KVA.

Force Air Cooling

In this method the air is first filtered to eliminate moisture and dust particless and this filetered air under pressure is forced to passed through the winding care of the transformer and the dusts provided in them. This method is used where there

is a scarcity of water.

Power Transformer Tutorials Links

Tutorials on Electrical Power Factor Correction

2012-03-17T06:54:00.000-07:00

All About Power Factor Links

Power Factor Meter
A direct reading instrument for measuring power factor. It is provided with a scale graduated in power factor.

Power Factor Relay
Power system device function numbers. A relay that operates when the power factor in an alternating current circuit rises above or falls below a predetermined value.

Power Feeder
A feeder supplying principally a power or heating load.

Power Frequency
The value of frequency used in the Electrical power system, such as 50 hz or 60 Hz.

Power Inverter
A converter unit in which the direction of average power flow in from the DC circuit to the alternating circuit.

Power Monitor
A functional module that monitors the status of the primary power source to the system, and signals when that power has strayed outside the limits required for reliable system operation. Since most systems are powered by an alternating current source, the power monitor is typically designed to detect dropout or
brown out conditions on alternating current lines.

Power Factor Question and Answer

1. If a current of 10 amperes at a power factor of 0.8 lagging is taken from 250 Volt alternating current supply, the reactive power of the system will work out to be 1500 VAR.
2. Many industrial tariffs penalise consumers whose power factor falls below 0.8.
3. Power factor improvement may be achieved the use of synchronous motor.
4. One of the reasons for improving the power factor is to decrease the reactive power.
5. The power factor of incadescent bulb is unit.
6. The power facotor of an inductive circuit can be improved by connecting a capacitor to it in series.
7. The capacitor of power factor correction are rated in terms of KVAR.
8. In an alternating current circuit, a low value of with reactive volt ampere compared with watts indicates high power factor.
9. It is not easy to find the value of impedance for a parallel circuit but power factor can easily be obtained as a ratio of active current to line current.
10. In a series circuit consisting of resistance and reactance, power factor is a defined as the ratio of resistance to impedance.
11. In pure reactive circuit, the power factor is zero.
12. Power factor is defined as the ratio of watts to volt ampere.
13. For a parallel circuit consisting of resistance and reactance the value of power factor is the ratio of impedance to resistance.
14. The power factor of an alternating current circuit containing both a resistor and a conductor is between 0 - 1 leading.
15. In a given circuit when power factor is unity the reactive power is zero.
16. A poor power factor results in overloading of transformer as well as alternators.
17. For the same load, if the power factor of load is reduced, it will draw more current.
18. The power factor of the magnetizing component of a transformer is always leading.
19. Another reason for improving the power factor is to avoid poor voltage regulation.
20. The advantage of using static capacitors to improve the power factor is that they are almost loss free.

Causes of Low Power Factor
1. Arc lamps and industrial heating furnaces are typical of low power factor operating equipments.
2. During the night time when load is less the supply voltage increase which in turn, causes the magnetising current of transformers and motors to increase. Therefore, the power factor at which the system operates becomes low.
3. Mostly alternating current motors are of induction type. These operate on low lagging power factor.

The Adverse of Low Power Factor
1. With low p.f. cost of generation and transmission increases due to increase in current and use of thicker wires and bigger switches.
2. Low pf. makes the voltage regulation of generators, transformer and transmission line greater.
3. For a given p.f. to be supplied, the current is increased due to low p.f. in causes increase in copper losses, and decreases the efficiency of both apparatus and supply system.
4. With low pf generators, transformer, swithes transmission lines become over loaded.

Electrical Transformer tutorials Current Potential and Auto tutorials

2012-03-14T03:20:00.000-07:00

Current Transformers The primary of this transformer consists of a few turns or even a single turn to carry the current to be measured and is connected in series with the main circuit. The secondary winding with large number of turns supplies a reduced current to the ammeter. The meter scale is calibrated directly in terms of the primary circuit current.The core is worked at low flux density so that, at all loads, secondary current is a constant ratio of the main circuit current. When the cuurent is flowing in the primary circuit, the secondary circuit should not be opened. In that case high voltage may be induced in the secondary and the core may become over saturated, heated up and thereby damage the magnetic properties permanently.

Potential Transformer
This is used to reduce the primary voltage to a safe value for operation of voltmeter and other instrument. Primary is connected to the H.T. to be measured and the secondary to a voltmeter. It is so designed that the ratio of primary to secondary is constant throughout. To limit the short circuit in case of failure of the transformer, limiting resistances are placed in series with the H.T. winding.

Auto-transformer works on the priciple of self Induction
It has only one winding which performs the function of both primary and secondary winding. As in ordinary transformer, the transformation ratio in autotransformer, is also equal to the turns ratio.
In case of step down transformer, the complete winding acts as primary winding while the tapped section of this winding works as secondary winding. In the step up transformer, the whole winding works as secondary winding and its there is much saving of copper. These transformers are used as regulating transformers where only a small variation of voltage is required. It is mainly used for starting and speed control of induction motors. It suffers from a disadvantage that the two windings are not electrically separate and in case of failure of insulation between the two, either a sever shock may be felt on the low voltage side.

Various parts of a Transformer
Primary winding
Secondary winding
Oil level
Conservator
Breather
Drain cock
Tube for cooling
Transformer Oil
Earth Point
Explosion vent
Buchhol's Relay
H.T. Terminals
L.T Terminals

Free Pdf file about the kinds of Transformer

Current Transformers
Current transformers are used in electrical grids for measurement and protective applications to provide signals to equipment such as meters and protective relays by stepping down the current of that system to measurable values.

Instrument Transformers
Technical Information and Application Guide

Selecting Current Transformers
As engineers, we are aware that electrical power systems have grown. How much have they grown?

Current Transformer Principles and Operation
Used with watt transducers enable the owner to control demand as well as monitor building and/or tenant power consumption. When CT's are used with Current Transducers, the result is an excellent method of diagnosing the performance of fans,pumps, chillers.

Potential Transformer
Voltage transformers connected line-to-ground cannot be considered to be grounding transformers and must not be operated with the secondaries in closed delta because excessive currents may flow in the delta.
VOLTAGE TRANSFORMERS
Potential transformer are so small that they may be neglected for protective-relaying purposes if the burden is within the "thermal" volt-ampere rating of the transformer. This thermal volt-ampere rating corresponds to the full-load rating of a power transformer.

Auto Transformer
The currents drawn by these two windings are out of phase by 180◦. This prompted the use of a part of the primary as secondary. This is equivalent to fusing the secondary turns into primary turns.

Transformers vs. Autotransformers
A transformer converts audio from one voltage and impedance to a different voltage and impedance. Transformers are passive which means they do not require a power supply to operate.

All About Electrical Distribution and Power Transformer Tutorials

2012-03-08T16:42:00.000-08:00

This is All About Transformer its principles, Definition, Testing Facts and Tutorials

Transformer Classification

Transformer Definition
It is a static device for transforming electrical energy from one alternating current circuit to another without any change in frequency. It changes voltage from high to low and low to high with a corresponding increase or in decrease current. If the voltage is increased it is said to be stepped up. If it is decreased, then it is said as stepped down.

Electrical Transformer Principle
When one coil like primary is connected to the alternating current supply current flows and an alternating flux is set up in the core. Most of this flux links with the second coil secondary. Law of electromagnetic induction.If the circuit is completed, current will flow. The secondary voltage depends upon the ratio of secondary turns to primary turns.

The Testing of the Transformer

Two test are performed on the transformer which are open circuit test and short circuit test. These tests are performed to determine the parameter or constants of transformer, efficiency and regulation.

1. Open Circuit Test
This is also called no load test. It determined the iron losses and the no load current. One winding of the transformer, usually the low voltage side is connected to its normal supply with an ammeter to measure the voltage applied to the winding and a wattmeter to measure taken by transformer at no load. the high voltage winding is kept open. Under these conditions normal flux will be set up in the core, therefore, normal iron losses will occur. The current taken will be wattmeter will indicate the iron losses.

2. Short Circuit Test
This test is used to determine the full load copper losses and the equivalent resitances and reactances referred to the metering side. In this test on the high voltage winding a reduced value of the voltage is increased until full load current is flowing in this winding. The applied voltage is a small fraction of the normal working voltage, the mutual flux produced is very small and hence the core losses at this voltage can be neglected. The wattmeter during this test gives the total coppery losses.

What is Distribution Transformer?
Transformer up to a size of 200 KVA, used to step down the distribution voltage to a standard service voltage, are known as distribution transformers. They are kept in operation all the 24 hours a day whether they are carrying load or not. Energy is lost in iron losses throughout the day while the copper losses account for loss in energy when the transformer is loaded. Therefore, the distribution transformer should have their iron losses small as compared to full load copper losses, in other words, they should be designed to have maximum efficiency at a load much lower than full load about 50 percent. Owing to low iron loss, the distribution transformer have good all day efficiency. These transformer have a good voltage regulation.

What is Power Transformer?
These transformers have rating about 20 KVA and are in generating stations and substations at each of a power transmission line for stepping up or stepping down the voltage. They may be either single or three phase units. They are put in operation during load periods and are disconnected during light load periods. Therefore the power transformer should be designed to have maximum efficiency at or near full load. Power transformer are designed to have considerable greater leakage reactance than that permissible in distribution transformers because in the case of power transformer, voltage regulation is less important than current limiting effect of higher leakage reactance.

Important Facts About Transformer
1. In and ideal transformer on no load, the primary applied voltage is balanced by the secondary.
2. The concentric windings are used in core type transformer with LT winding placed next to core.
3. Cross over windings are used for high voltage winding of small rating transformers.
4. The magnitude of mutual flux in a transformer is same at all levels.
5. The induced emf in the transformer secondary will depend upon frequency, flux and number of turns in the secondary.

Electrical Illumination Tutorials and Its Engineering Definition

2012-02-22T03:18:00.000-08:00

Light

The light is defined as the energy radiated in the form of waves which produces the sensation of vision to the eyes. It may be natural light from sun or the artificial from the means created by human beings.

Lumen

It is the unit of luminous flux and is defined as the luminous flux emitted per unit solid angle by a point source of one candle power.

Brightness

The brightness is defined as the luminous intensity per unit projected area of either a source of light or reflecting surface. It is denoted by B and the unit is stib which is nothing but candle per centimeter squared, other unit is nit which is candle per meter squared.

Coefficient of Utilization

It is defined as the ratio of the lumens actually received by a particular surface to the total lumens emitted by the luminous source. The coefficient of utilization or the utilizing factor is the total lumens actually received by the working plane per total lumens emitted by the light source.

Candle Power

The candle power is the light radiating capacity of a source in a given direction. It is defined as the number of lumens given out by a source in a unit C.P. and one meter away from it.

Colour

The sensation of colour is due to the difference in the wavelengths of the light radiations. Visible light can have length between 4000 A to 7500 A and colour varies in the way.

Luminous Intensity

The luminous intensity in any given direction is the luminous flux emitted by a source per unit solid angle. It is represented by I and measured in candle power.

Luminous Flux

It is the total quantity of light emitted by the source of light per second. It is represented by symbol O or F. It is measured in lumen. The total flux emitted by a source of I candle is 4 pi times I lumen where I is the luminous intensity of the source.

Some Characteristics of a good Illumination

1. The light source should not strike the eyes of the worker.
2. The type and size of the lamp should be correct.
3. Location should be proper.
4. Reflecting equipment should be suitable.

The Advantages of Correct Illumination

1. Factory production increases
2. Accidents decrease
3. Wastage of jobs decreases.

The sources of light is Three practicable ways of producing light are incandescent of heated filament and electric are glow discharge. Where the incandescent filament lamp is the light obtained by passing, current through a high resistance called the filament, this current being sufficient to raise the filament to luminosity. The filament is enclosed in an evacuated glass bulb. The object of the vacuum is first to prevent the filament burning away to reduce loss of heat by convection. The filament must be a conductor and must be capable of withstand a hight temperature.

All About Electrical and Electronics Measurement Facts and Tutorials

2012-02-16T16:50:00.000-08:00

It is important as an electrical engineer, we have a great knowledge how electrical or electronics measuring works, because the income of the electrical company depends on. listed below are key facts and tutorials that electrical engineer you should know.

A mirror is provided behind the pointer in measuring instruments to eliminate the reading errors, due to inclined observations, by removing parallel between the pointer and its image in the mirror.

Threshold of sensitivity with respect to instrument is the smallest signal that results in a detachable output.

Schering Bridge can be used to measure capacitance and its power factor.

Hay bridge is used to measure inductance of a high Q inductor.

Damping provides braking action on a meter pointer.

In moving coil meters, damping is provided by the aluminum frame.

Moving coil instruments are used in DC circuits only.

The sensitivity in accuracy of an instrument does not depend on hysteresis or dead bond, amplitude distortion and frequency response.

The sensitibity inaccuracy of a recording instrument means the maximum error in sensitivity displayed by a pen.

When using any instrument for measurement or testing an electrical circuit, your personal safety should be considered first.

The resolution of an indicating instrument is the smallest change in applied stimulas that indicates a detachable change in deflection.

The accuracy classes of industrial measuring instruments should be 1, 2.5, 2.5 and 5.

In measuring instrument, the internal resistance of ammeters should be very small, and that of voltmeters very high.

Meter accuracy is determined by full scale deflection.

The reliability of an instrument means degree to which as instrument's readability continues to remain within specific limits.

To reduce the effect of a voltmeter upon the circuit under test, we should get an instrument with a higher internal resistance.

To increase the range of a voltmeter a high resistance is connected in series.

The function of the zero adjust control in a multimeter is that the zero point is corrected with the help of this control.

If moving iron type ammeter is connected to a circuit, and we interchange its connected, then its reading will not change.

Eddy current damping methods is common in moving coil instruments.

The main reason for using springs in a measuring instrument is to control the pointer movement.

A moving iron type instrument has a nonlinear scale.

In moving coil instruments, the scale used is linear scale.

The function of a shunt in an ammeter is to by pass the current.

The shunt resistance in an ammeter is to bypass the current.

External shunts are generally used for measuring currents greater than about 30 ampere.

Induction type single phase energy meter is true watt hour meter.

A wattmeter can measure AC as well as DC power.

Meggar essentially is megaohmmeter. Meggar's operation is based upon moving coil meter.

If the aproximate value of the current to be measured is not known, the measurement should start on the highest range and then increase the range.

An electrodymic meter can be used to measure DC as well as AC voltage.

Meggar is an instrument to measure insulation resistance.

The cell used in a potentiometer is a lead accumulator.

A coil of high inductance equipment is not a part of meggar with a coil of high inductance.

The number of the coils in the meter of meggar is two.

With the measurement terminals open circuit, the infinity reading of meggar is due to currents in the coil connected across the measurement points.

Carey Foster Bridge is specially designed to determine the difference between two nearly equal resistances.

Maxwell bridge is used to measure inductance of a low Q inductor.

A multimeter consists of voltmeter, current meter and ohmmeter.

Sensitivity of a voltmeter is expressed as Ohms/Volt.

If a low voltage is measure on a higher scale of a voltmeter, the measurement would have low accuracy low resolution an low precision.

The disadvantage associated with an electro dynamic instrument are first it consumes more power second it has a low torque to

weight ration and third is its frequency range is low.

The simplest and most convenient form of detector used in a Wheatstone Bridge for audio frequency range is a pair of headphones
Inductance is measured in terms of capacitance and resistance by Anderson Bridge.

The potentiometer wire should have high specific resitance and low temperature coefficient.

Sensitivity of a potentiometer can be increased by increasing the length of potentiometer wire.

All About Electromagnetic Induction Facts and Tutorials

2012-02-09T05:54:00.000-08:00

Key Facts of Electromagnetic Induction

When a magnetic core is magnetized in a strong magnetic field, it retains magnetism after the magnetic force has been withdrawn. This phenomenon of lagging of induction flux density behind the magnetizing force is known as magnetic hysteresis. Moreover the same path is not followed during magnetization and demagnetization processes.

A Degaussing is the process of the demagnetizing metallic part.

Hysteresis can be reduced by the using grain oriented silicon steel.

According to Lenz's law the direction of induced electro motive force and hence current always opposes the cause producing it.

The time constant of an inductive circuit is defined as the ratio of L/R.

Air gap in the iron core of an inductive prevents linear law.

Sparking occurs when a load is switched off because the circuit has high inductance.

The growth of currents is an inductive circuit follows exponential law.

The mutual inductance of two coils is maximum when the coils are touching each other.

The coupling coefficient denotes the degree of magnetic linkage.

In electrical machines laminated cores are used with a view to reducing eddy current loss.

It is difficult to magnetize steel because of its low permeability.

Good Smoothing factor of a coil depends on the inductance of the coil.

The effect of the inductance of a coil on a constant direct current is that it does not effect the constant direct current.

The law that induces emf and current always opposes the cause producing them was discovered by the Lenz.

Leakage factor is more than unity.

A collapsing field around a coil tends to oppose the decay of coil current.

A conductor of length L has a current passing through it, when it is placed parallel to a strong magnetic field. The force experienced by the conductor will be zero.

The left hand rule, thumb correlates current, magnetic field and direction of force on a conductor.

While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with the current electric circuit.

Whenever a conductor cuts magnetic flux. An emf is induced in that conductor. This statement is due to Faraday's law.

While comparing magnetic and electric circuits, the point of dissimilarity exists while considering is flux and current flow.

Current Electricity Flow of Electrons Engineering Tutorials

2012-02-01T01:47:00.000-08:00

The Nature of Electricity
The modern theory defines matter as electrical in nature. All matter is made up of extremely small particles called molecules, each of which has the properties of matter of which it is a constituent. The molecules, in turn are made up of atoms, which are the smallest units of several elements. An atom consists of central nucleus of positive charge around which small negatively charged particles, called electrons, revolve in different paths or orbits.

Free Electrons
The electrons which can be easily removed or detached from an atom are called free electrons.
In metals, the atom lie very close together in regular formed crystal lattice. The nearness of one atom to another causes the electron in the outer orbit or valence electrons of each atom to be attracted by the nucleus is relatively weak. As a result, a large number of electrons are free to drift about interatomic space from atom to atom. These are called free electrons. The free electrons can be easily removed by applying a small amount of external energy.

Charge
A body is said to be charged if it has either excess or deficit of electrons from normal due share. If an electron is freed from a neutral atom, the proton predominate and the atom is said to posses a positive electric charge.

Unit
The unit of charge is coulomb and 1 coulomb is equal to charge on 628 by 10 to the power of 16. We say that a body has a positive discharge of ano coulomb, it means that it has a deficit of 628 by to the power of 16 electrons from normal due share.

Electric Potential
It is a measure of the density and sign of the electric charge at a point relative to that at some time. Thus electric potential, like electric charges and electric current is a phenomenon of displaced charges that exist in matter. For example, consider a copper rod of six meters length having the same number of electrons and protons distributed uniformly throughout.
If by some means, such as intercepting the flux in a magnetic field, one billion electrons can be shifted towards one end of the rod, that end will posses positive charge. The two ends of rod will have a different of potential. Work has been done to create this difference of potential energy.

Nucleus
It is the central part of an atom and contains protons and neutrons. A proton is positively charged particle while the neutron has nearly the same mass as proton, but has no charge. Therefore, the nucleus of an atom is positively charged. The sum of protons and neutrons constitute the entire weight of an atom and is called its atomic weight, it is because the particles in the extra nucleus has negligible weight as compared to protons or neutrons.

Extra Nucleus
It is the outer part of an atom and contains electrons only. An electron is a negatively charged particle having negligible mass. The charge on an electron is equal but opposite to that on a proton. Also, the number of electrons is equal to the number of protons in an atom under ordinary conditions. Therefore, an atom is neutral as a whole. The number of electrons or protons in an atom is called its atomic number.

All About Electrical Relays, Principles, Classification and Requirements

2012-01-22T04:31:00.000-08:00

Protective relays
Relay is a device by means of which an electric circuit can be controlled by the change in the same circuit or in other circuit. The primary function of the protective relay is to sense the fault in the system, compare the signal so obtained with the reference signal under normal conditions of operation and amplify the error signal such that the trip coil of the circuit breaker is energized and faulty section of the system is disconnected from the rest of the system.Under normal conditions of the system, a protective relay is required to keep itself alert such that in case of any emergency, the action may be taken almost instantneously.It should remain silent under normal condition. Under certain operating condition, the power system components are required to carry more than rated current on a temporary basis. During peak load condition, the power system components arc intentionally over-loaded. Under such conditions of operation, often known as abnormal condition, it is not necessary to disconnect the section from the system. When the operation parameters are unduly strained, the protective relays are required to energize the alarms such that proper precautions are taken.

The Basic Principles of Relays
In electromechanical relays, there are one or more coils, movable elements, contact system, etc. The operation of such relays depends on whether the operating torque/force is greater than the restraining torque/force.The relay operates, if the net force, F in equation given below is positive. Where F is the net force, Fo is the operating force and Fr is the restraining force. In other words, the relay operates only if the operating force is greater than the restraining force. In electromechanical relays, the operating torque is produced by electromagnetic attraction/electromagnetic induction/thermal effects of electric current. The restraining torque is given by springs.

The Classification of Relays
Protective relays are classified as follows according to their construction and the principle of operation.
1. Electromagnetic relays These are actuated by Direct current or Alternating current quantities.
2. Electomagnetic induction relays
3. Electothermal relays
4. Static relays these employ transistors or magnetic amplifiers to obtain the operating characteristic.
5. Electrodynamic relays these are operate on the same principle as moving coil instruments.
6. Under-voltage, under-current and under-power relays.
7. Over-voltage, over-current and over-power relays
8. Direntional or reverse current relays
9. Differential relays
10. Distance relays

The Basic Requirements of Protective System
The efficient protective relaying system should posses the following characteristics:
1. Speed
Minimum voltage and minimum fault time operate.
2. Selectivity
Maximum continuity of service by disconnecting the faulty part of the system.
3. Sensitivity
Capability of operating reliably under the actual desired conditions.

Protective Relays
These are the devices that detect abnormal conditions in electrical circuits by measuring the electrical quantities which are different under normal and faulty conditions. Due to abnormal conditions, voltage, current, phase and frequency may change. After detecting the fault, the relay operates to complete the trip circuit which results in the opening of the circuit breaker and isolating the faulty circuit.