Electrical Engineering Blog

Electronics: A Systems Approach - 4th Edition

2011-11-25T00:28:00.001-08:00

The fourth edition of Electronics: A Systems Approach is an outstanding introduction to this fast-moving, important field. Fully updated, it covers the latest changes and developments in the world of electronics. It continues to use Neil Storey’s well-respected systems approach, firstly explaining the overall concepts to build students' confidence and understanding, before looking at the more detailed analysis that follows. This allows the student to contextualise what the system is designed to achieve, before tackling the intricacies of the individual components. The book also offers an integrated treatment of analogue and digital electronics, highlighting and exploring the common ground between the two fields. This fourth edition represents a significant update and a major expansion of previous material, and now provides a comprehensive introduction to basic electrical engineering circuits and components in addition to a detailed treatment of electronic systems. This extended coverage permits the book to be used as a stand-alone text for introductory courses in both Electronics and Electrical Engineering.
This enables a college tyro to contextualise what a appurtenance is done to achieve, before traffic with a intricacies from a particular elements. The book offers an incorporated diagnosis compared with analogue as good as digital consumer electronics, highlighting as good as exploring a many renouned belligerent between your dual areas. This 4th book represents a estimable refurbish along with a vital expansion of before material, and now reserve a extensive intro to elemental electrical architectural circuits as good as components and a minute pill of digital systems. This enlarged coverage enables a book to turn used like a stand-alone textual calm for opening courses within both Consumer wiring and Electric Engineering

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All About Vertical Antennas

2011-11-24T23:57:00.001-08:00

The Arrl Antenna Book (19th Ed./Bk. this is the book for you. Amazon.com: The Arrl Antenna Book (19th Ed./Bk&CD-ROM. . Contents. Searches: buy cheap ebook reader All About Vertical Antennas, free ebooks reading All About Vertical Antennas, free ebook textbooks All About Vertical Antennas, adult. Antennas – American Radio Relay League | ARRL – The national. Carr Buy the Book Today! Antenna Toolkit by Joe Carr, Buy the Book Today! All about Antennas – Vertical, Beams, Dipoles, Wire CD | eBay All about Antennas – Vertical, Beams, Dipoles, Wire CD. Amateur Radio Antenna Projects IK-STIC 2 vertical, all band, antenna,. The MWA Antenna Book start by reading The ARRL Antenna Book and then move on to Smith’s Standard Broadcast Antenna Systems.. Practical Antenna Handbook by Joseph J. All the information you need to design your own. ARRL Antenna Book – DX Engineering – Antennas, Antenna Systems and. The ARRL Antenna Book (15th edition), ARRL, 1988,. Vertical Antenna Parts

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Electric car battery catches fire after crash test

2011-11-20T06:48:00.001-08:00

A Chevrolet Volt that caught fire three weeks after its lithium-ion battery was damaged in a government crash test has regulators taking a harder look at the safety of electric car batteries, federal officials said Friday. Based on testing so far, however, regulators believe the batteries are safe and do not pose a greater fire risk than gasoline-powered engines, a National Highway Traffic Safety Administration official told The Associated Press. The official requested anonymity in order to speak freely. The car that caught fire was tested May 12 by an agency contractor at a Wisconsin facility using a relatively new side-impact test intended to replicate crashing into a pole or a tree, the official said. Three weeks later, while the car was parked at the test facility, it caught fire and set several nearby vehicles on fire. A NHTSA investigation concluded the crash test damaged the battery, which later led to the fire. Lithium-ion batteries, which are used in a vast array of consumer electronics, have a history of sometimes catching fire when damaged.
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Download Machine Learning and Systems Engineering (Lecture Notes in Electrical Engineering)

2011-11-20T06:12:00.001-08:00

Robotics and Intelligent Systems Lecture Notes Free. Learning and Systems Engineering (Repost) Machine Learning and Systems Engineering (Lecture Notes in Electrical. Learning and Systems Engineering (Lecture Notes in Electrical Engineering) ebook Machine Learning and Systems Engineering (Lecture Notes in Electrical Engineering) book. Lecture Notes; Simulation of Electric Machine and Drive Systems using. Amouzegar, Sio-Iong Ao Download Machine. Electrical Engineering Notes – World Colleges Information | World. Downloads Machine Learning and Systems Engineering (Lecture Notes. Electrical power system engineering and. Downloads India, a Lifescape: Butterflies of Peninsular India e-book . . Fundamentals of Electrical Engineering and. ELECTRICAL MACHINES NOTES Notes. Amazon.com: Trends in Intelligent Systems and Computer Engineering (Lecture Notes in Electrical. J. and Identification, Machine Learning in Control, Neural Networks based Control Systems. Ross Quinlan – C4.5: Programs for Machine Learning Free. Lecture Notes on Optimization; Machine Learning, Neural and Statistical. of Electrical Engineering. Power System Analysis Lecture Notes on Electrical System
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Tutorial - Electric Power Transfer Capability : Concepts, Applications, Sensitivity and Uncertainty

2011-09-18T06:24:00.000-07:00

0.1 Report and project information
0.2 Acknowledgements
1 Introduction
    1.1 Summary
    1.2 General motivation
    1.3 A simplified transfer capability calculation
    1.4 AC load flow example using calculator
        1.4.1 Getting started on the calculator
        1.4.2 Quickly computing changes to transfer capability
        1.4.3 Transfer capability depends on assumptions
        1.4.4 Interactions between transfers
        1.4.5 6 bus system
        1.4.6 39 bus system
        1.4.7 NYISO 3357 bus system
        1.4.8 Concluding comments
    1.5 DC load flow example
2 Transfer capability
    2.1 Purpose of transfer capability computations
        2.1.1 Transfer capability and power system security
        2.1.2 Transfer capability and market forecasting
        2.1.3 Transfer capability and electricity markets
    2.2 Bilateral markets
    2.3 Overview of transfer capability computation
    2.4 Generic transfer capability
    2.5 Continuation methods
    2.6 Optimal power flow approaches
    2.7 Linear methods
3 Sensitivity of transfer capability
    3.1 Explanations of sensitivity
    3.2 Sensitivities in DC load flow
    3.3 Estimating interactions between transfers
    3.4 Fast formula for sensitivity and 3357 bus example
4 Applications
    4.1 Available transfer capability
    4.2 The economics of power markets and the Poolco model
    4.3 Nodal prices/Poolco
    4.4 Planning
    4.5 Market redispatch
    4.6 Summary of paper by Corniere et al.
    4.7 Background survey of security and optimization
5 Quantifying transmission reliability margin
    5.1 TRM and ATC
    5.2 Quantifying TRM with a formula
    5.3 Sources of uncertainty
    5.4 Simulation test results
    5.5 Probabilistic transfer capacity
    5.6 Conclusions
6 Uncertainty, probabilistic modeling and optimization
    6.1 Temperature uncertainty and load response modeling
    6.2 Sample calculation in IEEE 39 bus system
    6.3 Extensions to flowgates and general random injection variation
    6.4 Background on probability distributions
    6.5 Probability of transmission congestion in flowgates
    6.6 Numerical Example
    6.7 Maximizing probabilistic power transfers
    6.8 Numerical Example
    6.9 Stochastic optimal power flow
References

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Electricity and Magnetism

2011-09-17T22:57:00.000-07:00

This book will help you get beyond memorizing electricity-related formulas, rules, and procedures so you can understand the topic at a deep level deep enough to teach it with confidence and comfort. By covering the basics of static electricity, current electricity, and magnetism, the book develops a scientific model showing that electricity and magnetism are really the same phenomenon in different forms. A bonus feature: access to interactive software that you can download from the NSTA Web site. The software will help you investigate electrical circuits from simple to complex without having to buy a lot of expensive materials (or risking electrocution!). Electricity and Magnetism is the fifth title in the award-winning NSTA Press Stop Faking It! Series. As author Bill Robertson writes, The book you have in your hands is not a textbook. It is, however, designed to help you get science at a level you never thought possible, and also to bring you to the point where tackling more traditional science resources won t be a terrifying, lump-in-your-throat, I-don t-think-I ll-survive experience. Robertson serves as your friendly guide, one with a comforting knack for anticipating fears, meeting information needs, and entertaining as he edifies.

Book title: Electricity and Magnetism
By: Benjamin crowell
Publisher: N S T A
Pages: 161
Language: English
Edition: 2004
ISBN: 0873552369
Book type: PDF
File size: 2,0 MB
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Voltage Stability Toolbox

2011-09-17T22:46:00.000-07:00

Voltage instability and collapse have become an increasing concern in planning, operation, and control of electric power systems. In order to understand the phenomena and mechanics of voltage instability,a powerful and user-friendly analysis tool is very helpful. Voltage Stability Toolbox (VST) developed at the Center for Electric Power Engineering, Drexel University combines proven computational and analytical capabilities of bifurcation theory and symbolic mplementation and graphical representation capabilities of MATLAB and its Toolboxes. It can be used to analyze voltage stability problem and provide intuitive information for power system planning, operation, and control.

Voltage Stability Toolbox, developed at Center for Electric Power Engineering, Drexel University is a powerful software for studying the phenomena and mechanics of voltage instability. The computational and analytical capabilities of bifurcation theory, and symbolic/graphical representation capabilities of MATLAB combined lead to proven tool for analyzing voltage stability problem and providing intuitive information for power system planning, operation, and control.

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Electrical Studies For Trades 4th Edition

2011-07-31T23:59:00.000-07:00

ELECTRICAL STUDIES FOR TRADES, 4th EDITION is ideal for current and future service technicians in fields such as air conditioning and refrigeration, construction, and facilities management who require practical knowledge of electricity.

This book begins with an overview of basic electricity concepts rather than introducing complex mathematical calculations. From this starting point, readers proceed directly to must know information, including how to determine wire sizes and make a variety of common switch connections. Different types of electrical power panels are also examined in detail. Discussion of general wiring practices and circuit protectors, as well as an introduction to transformers and three phase and single phase motors, rounds out the comprehensive coverage.

Delmar Cengage (April 27, 2009) | ISBN : 1435469828 | English | 608 pages | PDF | 10MB

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EquationsPro 7.0

2011-06-06T19:07:00.000-07:00

EquationsPro is a chemical engineering,mathematical and chemistry program. Software suitable for chemistry,chemical engineering students and professionals. Solves 500+ chemical/electrical/civil/mechcanical engineering,design,distillation, physics, and mathematical equations. Contains 200+ unit conversions. Solve for matrices, triangles, finance, geometry,area/surface/volume,statistics and many other mathematical problems and equations. Solve and plot graphs using the Zgraphs program.
EquationsPro is a free to try software. You can free download and try it for an evaluation period.

Filesize 6,5 MB

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Field Excitation

2011-04-02T06:04:00.000-07:00

For a constant load, the power factor of a synchronous motor can be varied from a leading value to a lagging value by adjusting the DC field excitation (Figure 9). Field excitation can be adjusted so that PF = 1 (Figure 9a). With a constant load on the motor, when the field excitation is increased, the counter EMF (VG) increases. The esult is a change in phase between stator current (I) and terminal voltage (Vt), so that the motor operates at a leading power factor (Figure 9b). Vp in Figure 9 is the voltage drop in the stator winding’s due to the impedance of the windings and is 90° out of phase with the stator current. If we reduce field excitation, the motor will operate at a lagging power factor (Figure 9c). Note that torque angle, α, also varies as field excitation is adjusted to change power factor.

Figure 9. Synchronous Motor Field Excitation

Synchronous motors are used to accommodate large loads and to improve the power factor of transformers in large industrial complexes.

Summary
The important information in this chapter is summarized below.

AC Motor Types Summary

In a split-phase motor, a starting winding is utilized. This winding has a higher resistance and lower reactance than the main winding. When the same voltage (VT) is applied to the starting and main windings, the current in the main winding lags behind the current of the starting winding. The angle between the two windings is enough phase difference to provide a rotating magnetic field to produce a starting torque.
A synchronous motor is not a self-starting motor because torque is only developed when running at synchronous speed.
A synchronous motor may be started by a DC motor on a common shaft or by a squirrel-cage winding imbedded in the face of the rotor poles.
Keeping the same load, when the field excitation is increased on a synchronous motor, the motor operates at a leading power factor. If we reduce field excitation, the motor will operate at a lagging power factor.
The induction motor is the most commonly used AC motor in industrial applications because of its simplicity, rugged construction, and relatively low manufacturing costs.
Single-phase motors are used for very small commercial applications such as household appliances and buffers.
Synchronous motors are used to accommodate large loads and to improve the power factor of transformers in large industrial complexes.

Synchronous Motors

2011-04-02T05:50:00.000-07:00

Synchronous motors are like induction motors in that they both have stator windings that produce a rotating magnetic field. Unlike an induction motor, the synchronous motor is excited by an external DC source and, herefore, requires slip rings and brushes to provide current to the rotor. In the synchronous motor, the rotor locks into step with the rotating magnetic field and rotates at synchronous speed. If the synchronous motor is loaded to the point where the rotor is pulled out of step with the rotating magnetic field, no torque is developed, and the motor will stop. A synchronous motor is not a self-starting motor because torque is only developed when running at synchronous speed; therefore, the motor needs some type of device to bring the rotor to synchronous speed. Synchronous motors use a wound rotor. This type of rotor contains coils of wire placed in the rotor slots. Slip rings and brushes are used to supply current to the rotor.

Starting a Synchronous Motor
A synchronous motor may be started by a DC motor on a common shaft. When the motor is brought to synchronous speed, AC current is applied to the stator windings. The DC motor now acts as a DC generator and supplies DC field excitation to the rotor of the synchronous motor. The load may now be placed on the synchronous motor. Synchronous motors are more often started by means of a squirrel-cage winding embedded in the face of the rotor poles. The motor is then started as an induction motor and brought to ~95% of synchronous speed, at which time direct current is applied, and the motor begins to pull into synchronism. The torque required to pull the motor into synchronism is called the pull-in torque.
As we already know, the synchronous motor rotor is locked into step with the rotating magnetic field and must continue to operate at synchronous speed for all loads. During no-load conditions, the center lines of a pole of the rotating magnetic field and the DC field pole coincide (Figure 8a). As load is applied to the motor, there is a backward shift of the rotor pole, relative to the stator pole (Figure 8b). There is no change in speed. The angle between the rotor and stator poles is called the torque angle (α).

Figure 8. Torque Angle

If the mechanical load on the motor is increased to the point where the rotor is pulled out of Figure 8 Torque Angle synchronism (α≅90º), the motor will stop. The maximum value of torque that a motor can develop without losing synchronism is called its pull-out torque.

Single-Phase AC Induction Motors

2011-04-01T07:14:00.000-07:00

Figur 6. Split-Phase Motor

If two stator windings of unequal impedance are spaced 90 electrical degrees apart and connected in parallel to a single-phase source, the field produced will appear to rotate. This is called phase splitting.

In a split-phase motor, a starting winding is utilized. This winding has a higher resistance and lower reactance than the main winding (Figure 6). When the same voltage VT is applied to the starting and main windings, the current in the main winding (IM) lags behind the current of the starting winding IS (Figure 6). The angle between the two windings is enough phase difference to provide a rotating magnetic field to produce a starting torque. When the motor reaches 70 to 80% of synchronous speed, a centrifugal switch on the motor shaft opens and disconnects the starting winding. Single-phase motors are used for very small commercial applications such as household
appliances and buffers.

Induction Motor

2011-04-01T07:04:00.000-07:00

Previous explanations of the operation of an AC motor dealt with induction motors. The induction motor is the most commonly used AC motor in industrial applications because of its simplicity, rugged construction, and relatively low manufacturing costs. The reason that the induction motor has these characteristics is because the rotor is a self-contained unit, with no external connections. This type of motor derives its name from the fact that AC currents are induced into the rotor by a rotating magnetic field.

The induction motor rotor (Figure ) is made of a laminated cylinder with slots in its surface. The windings in the slots are one of two types. The most commonly used is the "squirrel-cage" rotor. This rotor is made of heavy copper bars that are connected at each end by a metal ring made of copper or brass. No insulation is required between the core and the bars because of the low voltages induced into the rotor bars. The size of the air gap between the rotor bars and stator windings necessary to obtain the maximum field strength is small.

AC Motor Theory Summary

2011-03-31T08:09:00.000-07:00

A magnetic field is produced in an AC motor through the action of the threephase voltage that is applied. Each of the three phases is 120° from the other phases. From one instant to the next, the magnetic fields combine to produce a magnetic field whose position shifts through a certain angle. At the end of one cycle of alternating current, the magnetic field will have shifted through 360°, or one revolution.
Torque in an AC motor is developed through interactions with the rotor and the rotating magnetic field. The rotating magnetic field cuts the bars of the rotor and induces a current in them due to generator action. This induced current will produce a magnetic field around the conductors of the rotor, which will try to line up with the magnetic field of the stator. Slip is the percentage difference between the speed of the rotor and the speed of the rotating magnetic field.
In an AC induction motor, as slip increases from zero to ~10%, the torque increases linearly. As the load and slip are increased beyond full-load torque, the torque will reach a maximum value at about 25% slip. If load is increased beyond this point, the motor will stall and come to a rapid stop. The typical induction motor breakdown torque varies from 200 to 300% of full-load torque. Starting torque is the value of torque at 100% slip and is normally 150 to 200% of full-load torque.

Torque

2011-03-10T09:52:00.000-08:00

The torque of an AC induction motor is dependent upon the strength of the interacting rotor and stator fields and the phase relationship between them. Torque can be calculated by using Equation

T = K Φ IR cos θR

where

T= torque (lb-ft)re
K = constant
Φ = stator magnetic flux
IR = rotor current (A)
cos θR = power factor of rotor

During normal operation, K, Φ, and cos θR are, for all intents and purposes, constant, so that torque is directly proportional to the rotor current. Rotor current increases in almost direct proportion to slip.

The change in torque with respect to slip (Figure) shows that, as slip increases from zero to ~10%, the torque increases linearly. As the load and slip are increased beyond full-load torque, the torque will reach a maximum value at about 25% slip. The maximum value of torque is called the breakdown torque of the motor. If load is increased beyond this point, the motor will stall and come to a rapid stop. The typical induction motor breakdown torque varies from 200 to 300% of full load torque. Starting torque is the value of torque at 100% slip and is normally 150 to 200% of full-load torque. As the rotor accelerates, torque will increase to breakdown torque and then decrease to the value required to carry the load on the motor at a constant speed, usually between 0-10%.

Slip

2011-03-08T06:25:00.000-08:00

It is virtually impossible for the rotor of an AC induction motor to turn at the same speed as that of the rotating magnetic field. If the speed of the rotor were the same as that of the stator, no relative motion between them would exist, and there would be no induced EMF in the rotor. (Recall from earlier modules that relative motion between a conductor and a magnetic field is needed to induce a current.) Without this induced EMF, there would be no interaction of fields to produce motion. The rotor must, therefore, rotate at some speed less than that of the stator if relative motion is to exist between the two.

The percentage difference between the speed of the rotor and the speed of the rotating magnetic field is called slip. The smaller the percentage, the closer the rotor speed is to the rotating magnetic field speed. Percent slip can be found by using Equation

where
NS = synchronous speed (rpm)
NR = rotor speed (rpm)

The speed of the rotating magnetic field or synchronous speed of a motor can be found by using Equation

where
Ns = speed of rotating field (rpm)
f = frequency of rotor current (Hz)
P = total number of poles

Torque Production

2011-03-07T20:34:00.000-08:00

When alternating current is applied Figure Induction Motor to the stator windings of an AC induction motor, a rotating magnetic field is developed. The rotating magnetic field cuts the bars of the rotor and induces a current in them due to generator action. The direction of this current flow can be found using the left-hand rule for generators.

This induced current will produce a magnetic field, opposite in polarity of the stator field, around the conductors of the rotor, which will try to line up with the magnetic field of the stator. Since the stator field is rotating continuously, the rotor cannot line up with, or lock onto, the stator field and, therefore, must follow behind it (Figure).

EnCalcEU 5.3

2011-03-06T06:23:00.000-08:00

EnCalcEU calculates the cost of electricity, allowing both the real cost based on meter readings and forward prediction based on the readings and elapsed time. The results can be saved to results and history log files for later analysis. The program can cope with different charging rates for electricity at different times of the day, alternative rates based on a preset threshold, varying tax rates plus fixed charges and discounts enabling most charging models to be handled. It also calculates the amount of CO2 generated. EnCalcEU is part of the JSutils group of software utilities which have a theme of energy conservation. Requires a registration code (free for personal non commercial use).

Installation is simple just unzip the installer from the downloaded file, double click on the installer and follow the on screen instructions (when selected, desktop shortcuts are installed for all users). As well as installing the program this will also install the help pages. EnCalcEU can be safely installed over previous installations. Start the program and enter the registration code to start using EnCalcEU. To keep the electricity data prior to upgrade do not allow the configuration file to be overwritten when prompted. Existing history files will be backed up on upgrade, see log files for more information.

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AC Motor Theory

2011-03-05T07:40:00.000-08:00

AC motors are widely used to drive machinery for a wide variety of applications. To understand how these motors operate, a knowledge of the basic theory of operation of AC motors is necessary.

Principles of Operation
The principle of operation for all AC motors relies on the interaction of a revolving magnetic field created in the stator by AC current, with an opposing magnetic field either induced on the rotor or provided by a separate DC current source. The resulting interaction produces usable torque, which can be coupled to desired loads throughout the facility in a convenient manner. Prior to the discussion of specific types of AC motors, some common terms and principles must be introduced.

Rotating Field
Before discussing how a rotating magnetic field will cause a motor rotor to turn, we must first find out how a rotating magnetic field is produced. Figure 1 illustrates a three-phase stator to which a three-phase AC current is supplied.
The windings are connected in wye. The two windings in each phase are wound in the same direction. At any instant in time, the magnetic field generated by one particular phase will depend on the current through that phase. If the current through that phase is zero, the resulting magnetic field is zero. If the current is at a maximum value, the resulting field is at a maximum value. Since the currents in the three windings are 120° out of phase, the magnetic fields produced will also be 120° out of phase. The three magnetic fields will combine to produce one field, which will act upon the rotor. In an AC induction motor, a magnetic field is induced in the rotor opposite in polarity of the magnetic field in the stator. Therefore, as the magnetic field rotates in the stator, the rotor also rotates to maintain its alignment with the stator’s magnetic field. The remainder of this chapter’s discussion deals with AC induction motors.

Facility Elements and Protection Requirements

2011-01-10T08:36:00.000-08:00

1. Generic C4ISR facility elements

To support its mission of gathering, processing, and transmitting information, the Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) facility contains as a minimum ten distinguishable elements. These are the structure or housing; electrical power generation and distribution [both alternating current (ac) and direct current (dc)]; non-electrical utilities; heating, ventilation, and air-conditioning (HVAC); an earth electrode; lightning protection; communications systems; computer and data processing systems; control and security systems; and personnel support systems.

a. Requirements. In general, C4ISR facility elements must conform to the requirements commonly encountered in commercial construction. However, because of their unique mission, the C4ISR facility elements must also accommodate several specialized requirements not found in commercial buildings or in military administration and support buildings. These specialized requirements impose restrictions on the configuration and installation of grounding networks and on bonding practices that are not common in routine construction. Fixed land-based C4ISR facilities range from small structures performing dedicated missions with few pieces of equipment to large complexes performing varied jobs involving many different kinds of signal and data processing equipment.

b. Facility characteristics. Regardless of the specific mission, land-based C4ISR facilities have certain characteristics that make them unique relative to administrative and support facilities. For example, in addition to commercial power, they commonly contain extensive on-site power generation capabilities for both emergency backup and power conditioning. Effective protection against electrical faults within this combined power system must be established. Also, because much of the information processed by the facilities is classified, TEMPEST measures must be taken to protect against unauthorized interception. In many locations, lightning presents a serious threat of damage to the sensitive equipment and protection must be provided. Hardness against disruption and damage from electromagnetic pulses (EMP) produced by nuclear blasts is also required in many facilities. Further, because of the amount of electronic data processing, transmission, and reception equipment in the facilities, there are many opportunities for electromagnetic interference (EMI) to occur. Integral to reliable operation of the C4ISR facility in this electromagnetic (EM) "environment" is the establishment of electrical fault protection networks and lightning discharge paths, the installation of interference control and surge suppression devices, and the implementation of EM shields between sensitive receptors and troublesome EM sources. Grounding and bonding are essential elements of these protective measures.

2. Element descriptions

Following are the descriptions of some common elements found in commercial and administrative facilities as well as in C4ISR facilities. For example, all facilities have structural, utility, HVAC, and personnel support elements. Other facilities may contain a number of the remaining elements.

a. Structure. The structure provides physical support, security, and weather protection for equipment and personnel. The structure is an element common to all facilities, yet it is the most varied. The size, configuration, material, and construction are rarely the same in any two C4ISR facilities.

(1) Wood, stone, glass, or concrete, which are essentially transparent to EM energy, provide little shielding to EMI and EMP threats.
(2) Structures containing steel reinforcing bars or steel superstructures offer some degree of EM protection. Other structures that have walls containing wire mesh, corrugated metal panels, aluminum siding, or solid metal foils or sheets offer still more protection against the transmission of EM energy into or out of the facility. Generally, as the metal content of the structure increases, so does the available EM protection. However, this protection depends heavily upon the electrical continuity (bonding) and topology of the structure. For example, structures which are completely enclosed by well-bonded steel sheets or plates with adequately treated apertures may provide over 100 decibels (dB) of protection from a few kilohertz to several gigahertz. On the other hand, open metallic construction may actually enhance coupling at frequencies where the members exhibit resonant lengths.
(3) Where TEMPEST or EMP protection is required, the structure of the C4ISR facility typically incorporates continuously bonded metal sheets in exterior walls or around rooms or clusters of rooms to provide a zonal barrier to prevent disruptive or compromising coupling of EM energy between internal equipment and the external environment. To maintain the shielding integrity of these EM barriers, all seams must be made electrically tight and all penetrations must be constructed and maintained to prevent unintended coupling of energy through the barrier. These penetrations include those required for personnel access, HVAC support, and signal and power transmission.

(4) For underground facilities, the housing typically consists of large interconnected metal rooms. The rock and earth overburden provides some degree of attenuation to EM energy; however, for complete EMP and TEMPEST protection, the added metal enclosures are necessary.
(5) The C4ISR facilities associated with the generation and transmission of high power radio frequency (RF) signals (e.g., long range radar installations or those providing high satellite linkages) commonly incorporate continuous RF shielding to control EMI to internal equipment. Similar requirements also exist in those facilities near commercial broadcast facilities or other RF-generating sources.
(6) Steel structural members offer many parallel conducting paths between various points within the facility and between these points and earth. These structural support members are frequently in direct contact with soil and can provide a low impedance path to earth. Because of the large cross-sectional areas of steel superstructural members, the net impedance between points is frequently less than that provided by lightning down conductors and electrical grounding conductors. For this reason, crossbonding between lightning down conductors and structural members is required to control flashover.

(7) Throughout the typical existing C4ISR facility, structural members are in frequent electrical contact with other facility elements either through intentional grounding or inadvertent grounding as a result of normal construction and installation practices. In general, structural members do not provide either adequate EM shielding or reliable power safety grounding. On the other hand, with proper bonding of structural members and with proper control of stray power return currents, the structure can be used to effectively augment grounding networks within the facility.
(8) The particular grounding and bonding requirements and constraints imposed on C4ISR structures are summarized in table 2-1.

b. Electric power generation and distribution. The power system is a network of electrical equipment, conductors, and distribution panels located throughout the C4ISR facility. The purposes of this network are to:

Table 2-1. Grounding and bonding principles for structures View

Transform, as necessary, and route commercially supplied power into the facility.
Generate appropriate on-line electrical power as required, especially during the absence of commercial power.
Switch between these two sources of electrical power.
Condition the electrical power for the critical loads being served.
Provide uninterrupted electrical power for critical equipment in all situations.
Distribute appropriate electrical power to the various equipment loads throughout the facility.
The overall facility power system includes both ac and dc subsystems. A one-line diagram of a generic ac system is illustrated by figure 2-1. It consists of a substation/transformer bank, a number of engine/generators (E/Gs), various switchgear, intermediate transformers, an uninterruptible power supply (UPS), transfer switches, and a network of conductors, disconnects, and distribution panels.
The substation/transformer bank, which can range in size from a single pad-mounted transformer
to a complete power substation, converts the incoming commercial power to the proper voltages for use at the facility. Commercial power is a primary ac power source for C4ISR installations wherever such sources are available and where operational and economic considerations permit. Independent, redundant sources are desirable. Thus, on-site electrical generators driven by diesel engines are commonly used to produce ac power as needed. The main facility switchgear is used to select one of the commercial power feeds or the generators as the primary source of facility power, to synchronize these sources, and to switch between them. In addition to having redundant feeds, this switchgear is configured with multiple buses so as to provide redundant paths to technical operational loads.
C4ISR facilities contain four types of electrical/electronic equipment to which power must be
supplied: critical technical, essential technical, non-essential loads, and emergency loads. Critical technical loads are those which must remain operational (100 percent continuity) in order for the facility
to carry out its assigned mission. Essential technical loads are those which are supportive of the assigned mission but are not required to have 100 percent continuity. Non-essential loads indirectly support the C4ISR mission. Emergency loads consist of life-safety equipment such as emergency lights, exit lights,and fire alarm and suppression systems.
The configuration of the ac power system following the main switchgear depends on the type of facility load being served. The critical and essential technical equipment loads are supplied through multiple bus switchgear and double feeds to provide redundant distribution paths. The non-essential loads are supplied through a single feed and single bus switchgear either from one bus in the main facility switchgear or directly from commercial power. In addition to the redundant distribution paths, the critical technical equipment loads are supplied through a UPS. The UPS provides continuous, high quality, uninterruptible power in all operational situations to the critical technical equipment within the facility. It consists of a rectifier bank driving a group of inverters, which generate the required ac power. Uninterruptible ac power results from paralleling the dc output of the rectifiers with a battery bank capable of carrying the critical facility load until the engine/generators are started, brought up to speed, and switched on-line. In addition, all incoming commercial and engine/generator power to critical loads is conditioned by the rectifier/battery/inverter process in normal operational situations.
The output of the UPS is routed via multiple buses and redundant feeds through breakers in the critical bus switchgear to branch distribution panels. These branch panels are located throughout the facility at critical equipment locations. The critical power is then routed through circuit breakers in each of these panels to specific pieces of equipment.
At appropriate locations in the power distribution paths, transformers and intermediate switchgear (indoor unit substations) and transfer switches may be employed. The transformers convert the ac power to the appropriate voltages and configuration (i.e., three-phase, delta or wye, or singlephase) for the loads being served. The transfer switches, which are typically automatic, switch between
two sources of power to provide continuous operation in the event of failure of one of the sources.
A typical configuration for the ac power system showing the neutral and grounding conductor
is illustrated in figure 2-2. (To simplify this figure, the redundant buses in the switchgear and the
redundant feeds are not shown.) Typically, every transformer between the ac power source and the load is a delta-primary/wye-secondary configuration, thus establishing a separately derived source at each transformer. Furthermore, the neutral is usually not run between intermediate switchgear. For example, although the neutral is usually present in the intermediate switchgear, it is usually not continued to the next successive transformer/switchgear assembly. It commonly begins at the last transformer prior to a single-phase load and is then routed with the phase conductors through the remaining switchgear and distribution panels to the loads.
The dc power system usually consists of multiple battery racks located at various places in the facility and includes dc switchgear, battery chargers, and distribution conductors. In some C4ISR facilities, individual battery racks are located near the dc loads they serve; in others, a large battery rack called the station battery serves the function of, and replaces, several individual battery racks. The dc power system supplies appropriate power for switchgear circuit breaker controls, protective and auxiliary relays, and pilot lights; for other instrumentation and control signaling and switching; and for the UPS equipment. Since the major functions of the dc loads are associated with generation, monitoring, and control of the ac power, a significant portion of the dc power system is located near the ac power switchgear.
In many facilities, there will be power conditioning centers dedicated to supplying highly filtered and protected power to data processing and other equipment demonstrated to be highly susceptible to power line transients and ground system noise. These centers commonly contain filters, terminal protection devices (TPDs), isolation transformers, voltage regulators, and overload protection. Depending upon the criticality of the equipment being served, a secondary UPS may also be provided by the power-conditioning center.
The particular grounding and bonding requirements and constraints imposed on C4ISR electric power generation and distribution are summarized in table 2-2.

c. Non-electric utilities. Non-electric utilities are the non-electrical piping used for gas, sewer, and water (both for fire fighting and normal use). In addition to these normal services, the facility will likely contain other non-electric utilities such as fire suppression, chilled water, compressed air, etc. The utility pipes providing these services are typically constructed of steel, cast iron, copper, or plastic. Some buried sewer lines may be fired clay. In older facilities, the lines enter the facility at different points and then branch out to form an interwoven tree network of pipes. Metal pipes of different non-electric utility systems are frequently mechanically bonded together to become electrically continuous along their path. For example, gas and water pipes become interconnected at hot water heaters; water and sewer pipes interconnect at sinks and appliances; all may interconnect with structural elements via mounting brackets. Through chilled water and other coolant systems, the utility piping network can become electrically interconnected with electronic equipment. The internal piping is commonly joined electrically to the external system of pipes. This electrically joined network may provide coupling paths for unwanted energy both between equipment internal to the facility and between internal equipment and the external environment, if adequate measures are not taken to disrupt the coupling path. The particular grounding and bonding requirements and constraints imposed on non-electric utilities are summarized in table 2-3.

d. Heating, ventilating and air conditioning (HVAC). HVAC is the network of equipment that regulates the internal physical environment of the facility. This system consists of the furnaces, airconditioners, heat pumps, and humidifiers that condition the air, ducts, vents, and fans that distribute the conditioned air throughout the facility

Formal Training and Qualifications

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Management should establish formal training and qualifications for qualified workers before they are permitted to perform electrical work. Refresher training is recommended at intervals not to exceed three years to provide an update on new regulations and electrical safety criteria. The training shall be on-the-job and/or classroom type. The degree of training provided shall be determined by the risk to the employee. This training shall be documented. Employees shall be trained and familiar with, but not be limited to, the following:

Safety-related work practices, including proper selection and use of PPE, that pertain to their respective job assignments.
Skills and techniques necessary to distinguish exposed live parts from other parts of electrical equipment.
Skills and techniques necessary to determine the nominal voltage of exposed live parts, clearance distances, and the corresponding voltages to which the qualified person will be exposed.
Procedures on how to perform their jobs safely and properly.
How to lockout/tagout energized electrical circuits and equipment safely.
29 CFR 1910.269(a) and 1910.332 also require training for persons other than qualified workers, if
job assignments bring them close enough to exposed parts of electrical circuits operating at 50 V or
more to ground for a hazard to exist. Other types of training recommended for electrical workers
include the following:
- National Electrical Code (NFPA 70)
- National Electrical Safety Code (ANSI C2)
- Use of personal protective grounds—29 CFR 1910.269(n), 1926.954(e), NESC Rule 445, and NFPA 70E, Part II, Ch. 2-4.
- Use of testing and measuring equipment—29 CFR 1910.269(o) and 1910.334(c)
- Work permit and work authorization procedures
- Use and care of personal protective equipment—29 CFR 1910.269(j) and 1910.335(a)
- Proper clothing required for arc blast protection—29 CFR 1910.269(l) and NFPA 70E Part II Ch. 2-3.3
- First aid and CPR—29 CFR1910.269(b) and 70E Part II, Ch. 2-1.3. Refresher training is recommended at intervals not to exceed 3 years (see OSHA Instruction CPL 2-2.53).

Ground Fault Circuit Interrupters

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There are 2 classes of ground-fault circuit interrupters and each class has a distinct function. A Class A ground-fault circuit interrupter trips when the current to ground has a value in the range of 4 through 6 milliamperes and is used for personnel protection. A Class A ground-fault circuit interrupter is suitable for use in branch circuits. A Class B ground-fault circuit interrupter (commonly used as ground fault protection for equipment) trips when the current to ground exceeds 20 milliamperes. A Class B GFCI is not suitable for employee protection.

Ground-fault circuit protection can be used in any location, circuit, or occupancy to provide additional protection from line-to-ground shock hazards because of the use of electric hand tools.

There are four types of GFCIs used in the industry:

1. Circuit breaker type

2. Receptacle type

3. Portable type

4. Permanently mounted type.

The condition of use determines the type of GFCI selected. For example, if an electrician or maintenance person plugs an extension cord into a nonprotected GFCI receptacle, the easiest way to provide GFCI protection is to utilize a portable-type GFCI. See NEMA 280-1990, “Application Guide for Ground Fault Circuit Interrupters.”

HOW A GFCI WORKS
See Section 4.14 for ground-fault protection of equipment. GFCIs are devices that sense when current—even a small amount—passes to ground through any path other than the proper conductor. When this condition exists, the GFCI quickly opens the circuit, stopping all current flow to the circuit and to a person receiving the ground-fault shock.
Figure 2-1 shows a typical circuit arrangement of a GFCI designed to protect personnel. The incoming two-wire circuit is connected to a two-pole, shunt-trip overload circuit breaker. The loadside conductors pass through a differential coil onto the outgoing circuit. As long as the current in both load wires is within specified tolerances, the circuit functions normally. If one of the conductors comes in contact with a grounded condition or passes through a person’s body to ground, an unbalanced current is established. This unbalanced current is picked up by the differential transformer, and a current is established through the sensing circuit to energize the shunt trip of the overload circuit breaker and quickly open the main circuit. A fuse or circuit breaker cannot provide this kind of protection. The fuse or circuit breaker will trip or open the circuit only if a line-to-line or line-to-ground fault occurs that is greater than the circuit protection device rating.

Figure 2-1. GFCI-protected circuits is one way of providing protection of personnel using electric hand tools on construction sites or other locations.

A GFCI will not protect the user from line-to-line or line-to-neutral contact hazards. For example, an employee is using a double insulated drill with a metal chuck and drill bit protected by a GFCI device. If the employee drills into an energized conductor and contacts the metal chuck or drill bit, the GFCI device will not trip (unless it is the circuit the GFCI device is connected to) as it will not detect a current imbalance.

The use of GFCI's in branch circuits for other than dwelling units is defined in NEC Section 210-8(b),
for feeders in NEC Section 215-9, and for temporary wiring in Section 305-6.
Ground-fault protection for personnel shall be provided for temporary wiring installations utilized
to supply temporary power to equipment used by personnel during construction, remodeling,
maintenance, repair or demolition activities.

For temporary wiring installations;

All 120-V, single-phase, 15- and 20-A receptacle outlets that are or are not a part of the permanent wiring of the building or structure and that are in use by employees shall have GFCI protection for personnel [See 29 CFR 1926.404(b) and NEC Section 305-6(a) and (b)] or an assured equipment grounding program (See Section 8.2).
GFCI protection or an assured equipment grounding program (See Section 8.2) for all other receptacles to protect against electrical shocks and hazards. [See NEC 305-6(a) and (b)].
Receptacles on a two-wire, single-phase portable or vehicle-mounted generator rated not more than 5 kW, where the circuit conductors of the generator are insulated from the generator frame and all other grounded surfaces, need not be protected with GFCIs. (See Figure 2-2 and Section 6.4). Portable GFCIs shall be trip tested according to the manufacturers instructions.

Occupational Safety and Health Administration (OSHA)

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Management is responsible to provide a workplace that is free from recognized hazards that might cause injury, illness, or death and to comply with the specific safety and health standards issued by Federal, state, and local authorities, especially the Occupational Safety and Health Administration (OSHA). Management expects all of its employees to comply with these regulations as well as the DOE requirements formulated for the health and safety of employees. Prevention of injury and illness requires the efforts of all and is a goal well worth achieving.

MANAGEMENT RESPONSIBILITIES
To ensure safety and protection of employees, management has the following responsibilities:

Ensure that employees are provided a workplace that is free from recognized hazards.
Ensure that employees performing electrical work are trained and qualified (see Section 2.8).
Ensure that approved, maintained, and tested personal protective equipment and clothing is provided, available, and used properly.
Establish, implement, and maintain procedures and practices that will ensure safe conduct of electrical work.
Keep and maintain records as required.

EMPLOYEE RESPONSIBILITIES
Employees are responsible to comply with occupational safety and health regulations and standards that apply to their own actions and conduct, including immediate reporting to management of unsafe and unhealthful conditions.

REVIEWS/INSPECTIONS
All modifications to existing facility and projects and new facilities should be subject to inspection by the authority having jurisdiction or their authorized designee to verify compliance with the codes and standards in effect on the date that such work was approved by a final design review. If the installation involves a hazard to life, equipment, or property, current standards and codes should be used to mitigate the hazard.

According to OSHA, under the Department of Labor (DOL), there are specific rules that apply to all installations and others that apply retroactively to installations installed after certain dates. Requirements listed in Table 2-1 are applicable to all electrical installations regardless of the date that they were designed and installed. All electrical systems and pieces of equipment that were installed after March 15, 1972, shall comply with all the requirements of 29 CFR 1910.302 through 1910.308, and not just the requirements listed in Table 2-1.
All major replacements, modifications, repairs, or rehabilitation performed after March 15, 1972, on electrical systems and equipment installed before March 15,1972, are required to comply with all the requirements of 29 CFR 1910.302 to 1910.308. OSHA considers major replacements, modifications, or rehabilitation to be work similar to that involved when a new building or facility is built, a new addition is built, or an entire floor is renovated.
A revision to 29 CFR 1910, Subpart S, was implemented and became effective April 16, 1981, which contained revised parts of 29 CFR 1910.302 through 1910.308 that apply to electrical systems and equipment installed after April 1, 1981.

Table 2-1. OSHA regulations that apply to all installations, regardless of the time they were designed or installed.

Table 2.1.

See Table 2-2 for a list of the sections and regulations that apply to electrical installations and equipment installed after April 16, 1981.
Table 2-2. OSHA regulations that apply to those electrical installations only if they were designed and installed after April 16, 1981.

Table. 2.2.

Safety Watch Responsibilities And Qualifications

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SAFETY WATCH RESPONSIBILITIES AND QUALIFICATIONS
The responsibilities and qualifications of personnel for sites that require the use of a safety watch are as follows:

Trained in cardiopulmonary resuscitation (CPR);
Thorough knowledge of the locations of emergency-shutdown push buttons and power disconnects in their operations;
Thorough knowledge of the specific working procedures to be followed and the work to be done;
Specific responsibilities include monitoring the work area for unsafe conditions or work practices and taking necessary action to ensure abatement of the unsafe condition or work practice, deenergizing equipment and alerting emergency-rescue personnel as conditions warrant, maintaining visual and audible contact with personnel performing the work, and removal of injured personnel, if possible; and
The safety watch should have no other duties that preclude observing and rendering aid if necessary.

BASIC SAFEGUARDS
To protect employees from some of the electrical hazards at industrial sites, Federal regulations limit the performance of electrical work to qualified and competent personnel. Specifically, the law requires that only a qualified person or someone working under the direct supervision of a qualified person may perform any repair, installation, or testing of electrical equipment. See Section 2.8 and the definitions of “Qualified Employee” or “Qualified Person” in Appendix B.

One of the best ways to prevent electrical accidents at industrial sites is to be aware of electrical dangers in the workplace. Once hazards have been identified, they must be pointed out and proper steps taken by a qualified person.

The following, where used, will improve the safety of the workplace:

Maintain good housekeeping and cleanliness.
Identify and diminish potential hazards.
Anticipate problems.
Resist pressure to “hurry up.”
Plan and analyze for safety in each step of a project.
Document work.
Use properly rated test equipment and verify its condition and operation before and after use.
Know and practice applicable emergency procedures.
Become qualified in cardiopulmonary resuscitation (CPR) and first aid and maintain current certifications.
Wear appropriate personal protective equipment (PPE).
Refer to system drawings and perform system walkdowns.
Electrical equipment should be maintained in accordance with the manufactures instructions.

Approval of Electrical Equipment

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Approval of Electrical Equipment

All electrical equipment, components, and conductors shall be approved for their intended uses, as
follows:

If equipment is of a kind that no nationally recognized testing laboratory (NRTL) accepts, certifies, lists, labels, or determines to be safe, it may be inspected or tested by another Federal agency or by a state, municipal, or other local authority responsible for enforcing the National Electrical Code (NEC), and found to comply with the provisions of the NEC. (See NEC Section 110-3.)
Equipment can be approved if it is built, designed, and tested according to specific nationally recognized standards such as UL 508 or one of the ANSI C series and is determined by the AHJ to be safe for its intended use.
If a particular piece of equipment is of a type not included in 1 or 2 above, the equipment shall be evaluated by the AHJ. If the equipment is approved by the AHJ, there shall be documentation of the evaluation and approval on file for this equipment. Simply stated, if any electrical system component is of a kind that any NRTL accepts, certifies, lists, or labels, then only NRTL accepted, certified, listed, or labeled components can be used. A nonlisted, nonlabeled, noncertified component may be used if it is of a kind that no NRTL covers, and then it shall be tested or inspected by the local authority responsible for enforcing the Code. For example, this would apply to custom made equipment. The custom made equipment should be built in accordance with a design approved by the AHJ.
Components or installations in aircraft, water craft, and railroads are exempt from the above approval requirements per 29 CFR 1910.302(a)(2)(i).

See 29 CFR 1910.399 for a detailed description of OSHA information for accepting electrical equipment and wiring methods that are not approved by an NRTL.

CODES, STANDARDS, AND REGULATIONS
Workers who perform electrical or electronic work, where applicable, shall comply with relevant DOE Orders and should comply with the current revision of the following codes and standards.

1. Standards published by the National Fire Protection. Association (NFPA)

a. National Electrical Code (NEC), NFPA 70
b. Electrical Safety Requirements for Employee Workplaces, NFPA 70E.
2. National Electrical Safety Code, ANSI C2.
3. All relevent state and local requirements.
The standards and performance specifications from the following organizations are recommended
and should be observed when applicable:
1. Institute of Electrical and Electronics Engineers (IEEE)
2. National Electrical Manufacturers Association (NEMA)
3. American National Standards Institute (ANSI)
4. American Society for Testing and Materials (ASTM)
5. National Fire Protection Association (NFPA)
6. Underwriters Laboratory, Inc. (UL)
7. Factory Mutual Engineering Corporation (FMEC)
8. Other Nationally Recognized Testing Laboratories recognized by OSHA on a limited basis.

Where no clear applicable code or standard provides adequate guidance or when questions regarding workmanship, judgment, or conflicting criteria arise, personnel safety protection shall be the primary consideration. Therefore, where there are conflicts between the mandatory requirements of the above codes, standards, and regulations, the requirements that address the particular hazard and provide the greater safety shall govern.