DESIGNING WITH SOLAR POWER FREE EBOOK DOWNLOAD LINKS


Review
'A highly readable and valuable source book on BIPV for a wide audience' Dr Clive Weatherby, Head of Technology, Solar Century --This text refers to an alternate Hardcover edition.

Product Description
Designing with Solar Power is the reult of international collaborative research and development work carried out within the remit of the International Energy Agency's Photovoltaic Power Systems Programme (IEA PVPS), where world-wide and interdisciplinary expert experience on building-integrated photovoltaics has been brought together to provide state-of-the-art information on technology and design issues. 

This book's mission is to inspire building professionals to think about photovoltics as an energy-producing building material, and to incorporate this energy source whenever possible. Hundreds of photos, diagrams and charts demonstrate the fundamentals of photovoltaics, the hurdles to be faced, experience to date, and overall, its enormous potential. 

More than twenty international case studies demonstrate the learning curve that has accompanied the early years of building-integrated photovoltaics.

HISTORY OF SCADA (Supervisory Control and Data Acquisition)

Electric power systems as we know them began developing in the early 20th century. Initially, generating plants were associated only with local loads that typically consisted of lighting and electric transportation.

If anything in the system failed — generating plant, power lines, or connections — the lights would quite literally be “out.” Customers had not yet learned to depend on electricity being nearly 100% reliable, so outages, whether routine or emergency, were taken as a matter of course.

As reliance on electric power grew, so did the need to find ways to improve reliability. Generating stations and power lines were interconnected to provide redundancy, and higher voltages were used for longer distance transportation of electricity.

Points where power lines came together or where voltages were transformed came to be known as “substations.” Substations often employed protective devices to allow system failures to be isolated so that faults would not bring down the entire system, and operating personnel were often stationed at these important points in the electrical system so that they could monitor and quickly respond to any problems that might arise. They would communicate with central system dispatchers by any means available — often by telephone — to keep them apprised of the condition of the system. Such “manned” substations were normative throughout the first half of the 20th century.

As the demands for reliable electric power became greater and as labor became a more significant part of the cost of providing electric power, technologies known as “supervisory control and data acquisition,” or SCADA for short, were developed to allow remote monitoring and even control of key system parameters. SCADA systems began to reduce and even eliminate the need for personnel to be on-hand at substations.

Early SCADA systems provided remote indication and control of substation parameters using technology borrowed from automatic telephone switching systems. As early as 1932, Automatic Electric was advertising “remote-control” products based on its successful line of “Strowger” telephone switching apparatus.

Another example (used as late as the 1960s) was an early Westinghouse REDAC system that used telephone-type electromechanical relay equipment at both ends of a conventional twisted-pair telephone circuit.

Data rates on these early systems were slow. Data were sent in the same manner as rotary-dial telephone commands at 10 bps, so only a limited amount of information could be passed using this technology.

Early SCADA systems were built on the notion of replicating remote controls, lamps, and analog indications at the functional equivalent of pushbuttons, often placed on a mapboard for easy operator interface. The SCADA masters simply replicated, point for point, control circuits connected to the remote (slave) unit.

During the same time frame as SCADA systems were developing, a second technology — remote teleprinting, or “Teletype” — was coming of age, and by the 1960s had gone through several generations of development.
The invention of a second device — the “modem” (MOdulator/DEModulator) — allowed digital information to be sent over wire pairs that had been engineered to only carry the electronic equivalent of human voice communication.

With the introduction of digital electronics it was possible to use faster data streams to provide remote indication and control of system parameters. This marriage of Teletype technology with digital electronics gave birth to remote terminal units (RTUs), which were typically built with discrete solid-state electronics and could provide remote indication and control of both discrete events and analog voltage and current quantities.

Beginning also in the late 1960s and early 1970s, technology leaders began exploring the use of small computers (minicomputers at that time) in substations to provide advanced functional and communication capability. But early application of computers in electric substations met with industry resistance because of perceived and real reliability issues.

The introduction of the microprocessor with the Intel 4004 in 1971 opened the door for increasing sophistication in RTU design that is still continuing today. Traditional point-oriented RTUs that reported discrete events and analog quantities could be built in a fraction of the physical size required by previous discrete designs.

More intelligence could be introduced into the device to increase its functionality. For the first time RTUs could be built to report quantities in engineering units rather than as raw binary values. One early design developed at Northern States Power Company in 1972 used the Intel 4004 as the basis for a standardized environmental data acquisition and retrieval (SEDAR) system that collected, logged, and reported environmental information in engineering units using only 4 kilobytes of program memory and 512 nibbles (half-bytes) of data memory.

While the microprocessor offered the potential for greatly increased functionality at lower cost, the industry also demanded very high reliability and long service life measured in decades, conditions that were difficult to achieve with early devices. Thus the industry was slow to accept the use of microprocessor technology in mission-critical applications.

By the late 1970s and early 1980s, integrated microprocessorbased devices were introduced, and these came to be known as intelligent electronic devices, or IEDs.

Early IEDs simply replicated the functionality of their predecessors — remotely reporting and controlling contact closures and analog quantities using proprietary communication protocols. Increasingly, IEDs are also being used to convert data into engineering unit values in the field and to participate in field-based local control algorithms. Many IEDs are being built with programmable logic controller (PLC) capability and, indeed, PLCs are being used as RTUs and IEDs to the point that the distinction between these different types of smart field devices is rapidly blurring.

Early SCADA communication protocols were usually proprietary and were also often kept secret from the industry. A trend beginning in the mid-1980s has been to minimize the number of proprietary
communication practices and to drive field practices toward open, standards-based specifications.

Two noteworthy pieces of work in this respect are the International Electrotechnical Commission (IEC) 870- 5 family of standards and the IEC 61850 standard. The IEC 870-5 work represents the pinnacle of the traditional point-list-oriented SCADA protocols, while the IEC 61850 standard is the first of an emerging approach to networkable, object-oriented SCADA protocols based on work started in the mid-1980s by the Electric Power Research Institute (EPRI) that became known as the Utility Communication Architecture (UCA).

LIVE TANK AND DEAD TANK CIRCUIT BREAKER COMPARISON TUTORIALS

Dead Tank Circuit Breakers
Circuit breakers are available as live-tank or dead-tank designs. Dead-tank designs put the interrupter in a grounded metal enclosure.

Interrupter maintenance is at ground level and seismic withstand is improved vs. the live-tank designs. Bushings are used for line and load connections which permit installation of bushing current transformers for relaying and metering at a nominal cost.

The dead-tank breaker does require additional insulating oil or gas to provide the insulation between the interrupter and the grounded tank enclosure.

Live Tank Circuit Breakers
Live-tank circuit breakers consist of an interrupter chamber that is mounted on insulators and is at line potential. This approach allows a modular design as interrupters can be connected in series to operate at higher voltage levels.

Operation of the contacts is usually through an insulated operating rod or rotation of a porcelain insulator assembly by an operator at ground level. This design minimizes the quantity of oil or gas used for interrupting the arc as no additional quantity is required for insulation of a dead-tank enclosure.

The design also readily adapts to the addition of pre-insertion resistors or grading capacitors when they are required. Seismic capability requires special consideration due to the high center of gravity of the interrupting chamber assembly.

REASONS FOR SUBSTATION GROUNDING

The substation grounding system is an essential part of the overall electrical system. The proper grounding of a substation is important for the following two reasons:

1. It provides a means of dissipating electric current into the earth without exceeding the operating limits of the equipment
2. It provides a safe environment to protect personnel in the vicinity of grounded facilities from the dangers of electric shock under fault conditions

The grounding system includes all of the interconnected grounding facilities in the substation area, including the ground grid, overhead ground wires, neutral conductors, underground cables, foundations, deep well, etc. The ground grid consists of horizontal interconnected bare conductors (mat) and ground rods.

The design of the ground grid to control voltage levels to safe values should consider the total grounding system to provide a safe system at an economical cost. The following information is mainly concerned with personnel safety.

The information regarding the grounding system resistance, grid current, and ground potential rise can also be used to determine if the operating limits of the equipment will be exceeded.

Safe grounding requires the interaction of two grounding systems:
1. The intentional ground, consisting of grounding systems buried at some depth below the earth’s surface
2. The accidental ground, temporarily established by a person exposed to a potential gradient in the vicinity of a grounded facility

It is often assumed that any grounded object can be safely touched. A low substation ground resistance is not, in itself, a guarantee of safety.

There is no simple relation between the resistance of the grounding system as a whole and the maximum shock current to which a person might be exposed. A substation with relatively low ground resistance might be dangerous, while another substation with very high ground resistance might be safe or could be made safe by careful design.

There are many parameters that have an effect on the voltages in and around the substation area. Since voltages are site-dependent, it is impossible to design one grounding system that is acceptable for all locations.

The grid current, fault duration, soil resistivity, surface material, and the size and shape of the grid all have a substantial effect on the voltages in and around the substation area. If the geometry, location of ground electrodes, local soil characteristics, and other factors contribute to an excessive potential gradient at the earth surface, the grounding system may be inadequate from a safety aspect
despite its capacity to carry the fault current in magnitudes and durations permitted by protective relays.

During typical ground fault conditions, unless proper precautions are taken in design, the maximum potential gradients along the earth surface may be of sufficient magnitude to endanger a person in the area. Moreover, hazardous voltages may develop between grounded structures or equipment frames and the nearby earth.

The circumstances that make human electric shock accidents possible are:
• Relatively high fault current to ground in relation to the area of the grounding system and its resistance to remote earth
• Soil resistivity and distribution of ground currents such that high potential gradients may occur at points at the earth surface
• Presence of a person at such a point, time, and position that the body is bridging two points of high potential difference
• Absence of sufficient contact resistance or other series resistance to limit current through the body to a safe value under the above circumstances
• Duration of the fault and body contact and, hence, of the flow of current through a human body for a sufficient time to cause harm at the given current intensity

The relative infrequency of accidents is due largely to the low probability of coincidence of the above unfavorable conditions. To provide a safe condition for personnel within and around the substation area, the grounding system design limits the potential difference a person can come in contact with to safe levels. IEEE Std. 80, IEEE Guide for Safety in AC Substation Grounding [1], provides general information about substation grounding and the specific design equations necessary to design a safe substation grounding system. 

POWER CIRCUIT BREAKERS ON POWERS SYSTEM TUTORIALS

A circuit breaker is defined as “a mechanical switching device capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying and breaking for a specified time, and breaking currents under specified abnormal circuit conditions such as a short circuit” (IEEE Std. C37.100-1992).

Circuit breakers are generally classified according to the interrupting medium used to cool and elongate the electrical arc permitting interruption. The types are:
• Air magnetic
• Oil
• Air blast
• Vacuum
• SF6 gas

Air magnetic circuit breakers are limited to older switchgear and have generally been replaced by
vacuum or SF6 for switchgear applications. Vacuum is used for switchgear applications and some outdoor breakers, generally 38 kV class and below. Air blast breakers, used for high voltages ( ≥ 765 kV), are no longer manufactured and have been replaced by breakers using SF6 technology.

Oil circuit breakers have been widely used in the utility industry in the past but have been replaced by other breaker technologies for newer installations. Two designs exist — bulk oil (dead-tank designs) dominant in the U.S.; and oil minimum breaker technology (live-tank design).

Bulk oil circuit breakers were designed as single-tank or three-tank mechanisms; generally, at higher voltages, three-tank designs were dominant. Oil circuit breakers were large and required significant foundations to support the weight and impact loads occurring during operation.

Environmental concerns forcing the necessity of oil retention systems, maintenance costs, and the development of the SF6 gas circuit breaker have led to the gradual replacement of the oil circuit breaker for new installations.

Oil circuit breaker development has been relatively static for many years. The design of the interrupter employs the arc caused when the contacts are parted and the breaker starts to operate. The electrical arc generates hydrogen gas due to the decomposition of the insulating mineral oil.

The interrupter is designed to use the gas as a cooling mechanism to cool the arc and to use the pressure to elongate the arc through a grid (arc chutes), allowing extinguishing of the arc when the current passes through zero.

Vacuum circuit breakers use an interrupter that is a small cylinder enclosing the moving contacts under a high vacuum. When the contacts part, an arc is formed from contact erosion. The arc products are immediately forced to and deposited on a metallic shield surrounding the contacts. Without anything to sustain the arc, it is quickly extinguished.

Vacuum circuit breakers are widely employed for metal-clad switchgear up to 38 kV class. The small size of the breaker allows vertically stacked installations of breakers in a two-high configuration within one vertical section of switchgear, permitting significant savings in space and material compared to earlier designs employing air magnetic technology.
When used in outdoor circuit breaker designs, the vacuum cylinder is housed in a metal cabinet or oil-filled tank for dead tank construction popular in the U.S. Market.

Gas circuit breakers generally employ SF6 (sulfur hexaflouride) as an interrupting and sometimes as an insulating medium. In “single puffer” mechanisms, the interrupter is designed to compress the gas during the opening stroke and use the compressed gas as a transfer mechanism to cool the arc and to elongate the arc through a grid (arc chutes), allowing extinguishing of the arc when the current passes through zero.

In other designs, the arc heats the SF6 gas and the resulting pressure is used for elongating and interrupting the arc. Some older two-pressure SF6 breakers employed a pump to provide the highpressure SF6 gas for arc interruption.

Gas circuit breakers typically operate at pressures between six and seven atmospheres. The dielectric strength of SF6 gas reduces significantly at lower pressures, normally as a result of lower ambient temperatures. Monitoring of the density of the SF6 gas is critical and some designs will block operation of the circuit breaker in the event of low gas density.

POWER SUBSTATION BUS AND SWITCHING CONFIGURATION TYPES AND TUTORIALS

There are six types of substation bus/switching arrangements commonly used in air insulated substations:
1. Single bus
2. Double bus, double breaker
3. Main and transfer (inspection) bus
4. Double bus, single breaker
5. Ring bus
6. Breaker and a half

Single Bus

-One main bus with all circuits connected directly to the bus.
-Very low reliability.
-A single failure to the main bus or any circuit section between its circuit breaker and the main bus will cause an outage of the entire system.
-Maintenance of the bus would require the outage of the total system, use of standby generation, or switching to adjacent station, if available.

Since the single bus arrangement is low in reliability, it is not recommended for heavily loaded substations or substations having a high availability requirement. Reliability of this arrangement can be improved by the addition of a bus tiebreaker to minimize the effect of a main bus failure.

Double Bus, Double Breaker

-Very high level of reliability by having two separate breakers available to each
circuit.
-Maintenance of a bus or a circuit breaker in this arrangement can be accomplished without interrupting either of the circuits.

A double bus, double breaker scheme is a high-cost arrangement, since each line has two breakers and requires a larger area for the substation to accommodate the additional equipment. This is especially true in a low profile configuration. The protection scheme is also more involved than a single bus scheme.

Main and Transfer Bus

-All circuits are connected between a main (operating) bus and a transfer bus (also referred to as an inspection bus).
-Reliability of this system is not very high. However, with the transfer bus available during maintenance, de-energizing of the circuit can be avoided. Some systems are operated with the transfer bus normally de-energized.

A shortcoming of this scheme is that if the main bus is taken out of service, even though the circuits can remain energized through the transfer bus and its associated switches, there would be no relay protection for the circuits. Depending on the system arrangement, this concern can be minimized through the use of circuit protection devices (reclosure or fuses) on the lines outside the substation.

This arrangement is slightly more expensive than the single bus arrangement, but does provide more flexibility during maintenance. Protection of this scheme is similar to that of the single bus arrangement. The area required for a low profile substation with a main and transfer bus scheme is also greater than that of the single bus, due to the additional switches and bus.

Ring Bus

All breakers are arranged in a ring with circuits tapped between breakers. For a failure on a circuit, the two adjacent breakers will trip without affecting the rest of the system.

A single bus failure will only affect the adjacent breakers and allow the rest of the system to remain energized. A breaker failure or breakers that fail to trip will require adjacent breakers to be tripped to isolate the fault.

Maintenance on a circuit breaker in this scheme can be accomplished without interrupting any circuit, including the two circuits adjacent to the breaker being maintained. The breaker to be maintained is taken out of service by tripping the breaker, then opening its isolation switches. Since the other breakers adjacent to the breaker being maintained are in service, they will continue to supply the circuits.

In order to gain the highest reliability with a ring bus scheme, load and source circuits should be alternated when connecting to the scheme. Arranging the scheme in this manner will minimize the potential for the loss of the supply to the ring bus due to a breaker failure.

Relaying is more complex in this scheme than some previously identified. Since there is only one bus in this scheme, the area required to develop this scheme is less than some of the previously discussed schemes. However, expansion of a ring bus is limited, due to the practical arrangement of circuits.

Breaker-and-a-Half

The breaker-and-a-half scheme can be developed from a ring bus arrangement as the number of circuits increases. In this scheme, each circuit is between two circuit breakers, and there are two main buses.

The failure of a circuit will trip the two adjacent breakers and not interrupt any other circuit. With the three breaker arrangement for each bay, a center breaker failure will cause the loss of the two adjacent circuits. However, a breaker failure of the breaker adjacent to the bus will only interrupt one circuit.

Maintenance of a breaker on this scheme can be performed without an outage to any circuit. Furthermore, either bus can be taken out of service with no interruption to the service. This is one of the most reliable arrangements, and it can continue to be expanded as required.

Relaying is more involved than some schemes previously discussed. This scheme will require more area and is costly due to the additional components.

OVERCURRENT PROTECTION TRIPPING METHODS ON POWER SYSTEM TUTORIALS

The substation circuit-breaker tripping power may be from either a d-c or an a-c source. A d-c tripping source is usually obtained from a tripping batttery, but may also be obtained from a station service battery or a charged capacitor.

The a-c tripping source is obtained from current transformers located in the circuit to be protected.

DC Battery Trip
When properly and adequately maintained, the battery offers the most reliable tripping source. It requires no auxiliary tripping devices, and uses single-contact relays that directly energize a single trip coil in the breaker.

A battery trip supply is not affected by the power-circuit voltage and current conditions during time of faults, and therefore is considered the best source for all types of protective relay tripping. An additional advantage is that only one battery is required for each substation location and it may be used for other equipment; e.g., highvoltage breaker trip circuits and ground switches.

A tripping battery is usually the most economical source of power for tripping a number of breakers. When only one or two breakers are involved, however, it may be more economical to use a-c current or capacitor trip.

Long service can be obtained from batteries when they receive proper maintenance and when they are kept fully charged and the electrolyte is maintained at the proper level and density. When lead acid batteries are subjected to extremely low ambient temperatures, their output is considerably
reduced.

In outdoor unit substations, this necessitates larger ampere-hour capacities. For substations in outlying locations where periodic maintenance is difficult, such as many single-circuit substation applications, other types of tripping sources may be more satisfactory.

Capacitor Trip
An a-c potential source is required for charging the capacitors used in the capacitor trip unit. This source may be either a control power transformer or a potential transformer connected where voltage is normally present.

A control power transformer is usually used because it is required for a-c closing of the circuit breakers. Capacitor trip uses the same standard single-closing contact relays as d-c battery trip.

A separate capacitor trip unit is required for each breaker in the substation. The charging time for the unit is approximately 0.04 second and any failure in the charging source for a period longer than 30 seconds renders the trip inoperative.

This time must be factored into time-delay settings of relays. The capacitor trip unit can be used only with low energy tripping devices such as the impact trip device used on modern breaker operating mechanisms.

Due to the limited amount of energy available from this device, the breaker must be well maintained to assure successful operation. This unit provides tripping potential independent of the magnitude of fault current, which makes it particularly applicable on lightly loaded, high impedance circuits where a-c current trip cannot be used and a battery cannot be justified.

AC Current Trip
If adequate current is always available during fault conditions, the current transformers in the protected circuit provide a reliable source of tripping energy which is obtained directly from the faulted circuit. The tripping may be either instantaneous or time delay in operation; but in all cases, it is applicable only to overcurrent protection.

The trip circuit is more complex than for d-c tripping because three trip circuits, complete with individual trip coils and auxiliary devices, are required for each breaker for overcurrent tripping. A potential trip coil is also required for each breaker for normal switching operations.

This permits manual tripping of the breaker by means of the breaker control switch. The three trip coils are normally connected in each phase circuit, rather than two phase coils and one residual coil.

This is because adequate trip current may not be available under all ground-fault conditions – e.g., when a ground fault occurs at some distance out on the feeder so that there is sufficient neutral impedance to limit the fault current to a value insufficient to cause tripping, or when applied to a system grounded through a neutral impedance.

A residual relay, which trips the breaker by means of a potential trip coil, is used to provide ground fault protection under conditions such as these. A minimum of three or four amperes CT secondary current is required to energize the three-ampere current-trip coils used for this method of tripping.

The use of 0.5- to 4.0-ampere range time-overcurrent relays is not recommended because they are more sensitive than the a-c trip coils.

A-c current trip may be by means of reactor trip (circuit closing relays) or auxiliary relay trip (circuit-opening relays). The reactor trip method is usually recommended because of its simplicity and because it uses the more standard type overcurrent relays.

POWER TRANSFORMER ELECTRICAL PROTECTION TYPES TUTORIALS

Fuse
Power fuses have been used for many years to provide transformer fault protection. Generally it is recommended that transformers sized larger than 10 MVA be protected with more sensitive devices such as the differential relay discussed later in this section.

Fuses provide a low maintenance, economical solution for protection. Protection and control devices, circuit breakers, and station batteries are not required.

There are some drawbacks. Fuses provide limited protection for some internal transformer faults. A fuse is also a single phase device. Certain system faults may only operate one fuse. This will result in single phase service to connected three phase customers.

Fuse selection criteria include: adequate interrupting capability, calculating load currents during peak and emergency conditions, performing coordination studies that include source and low side protection equipment, and expected transformer size and winding configuration (ANSI=IEEE, 1985).

Overcurrent Protection
Overcurrent relays generally provide the same level of protection as power fuses. Higher sensitivity and fault clearing times can be achieved in some instances by using an overcurrent relay connected to measure residual current.

This application allows pick up settings to be lower than expected maximum load current. It is also possible to apply an instantaneous overcurrent relay set to respond only to faults within the first 75% of the transformer.

This solution, for which careful fault current calculations are needed, does not require coordination with low side protective devices. Overcurrent relays do not have the same maintenance and cost advantages found with power fuses.

Protection and control devices, circuit breakers, and station batteries are required. The overcurrent relays are a small part of the total cost and when this alternative is chosen, differential relays are generally added to enhance transformer protection. In this instance, the overcurrent relays will provide backup protection for the differentials.

Differential Protection
The most widely accepted device for transformer protection is called a restrained differential relay. This relay compares current values flowing into and out of the transformer windings.

To assure protection under varying conditions, the main protection element has a multislope restrained characteristic. The initial slope ensures sensitivity for internal faults while allowing for up to 15% mismatch when the power transformer is at the limit of its tap range (if supplied with a load tap changer). At currents above rated transformer capacity, extra errors may be gradually introduced as a result of CT saturation.

However, misoperation of the differential element is possible during transformer energization. High inrush currents may occur, depending on the point on wave of switching as well as the magnetic state of the transformer core. Since the inrush current flows only in the energized winding, differential current results.

The use of traditional second harmonic restraint to block the relay during inrush conditions may result in a significant slowing of the relay during heavy internal faults due to the possible presence of second harmonics as a result of saturation of the line current transformers.

To overcome this, some relays use a waveform recognition technique to detect the inrush condition. The differential current waveform associated with magnetizing inrush is characterized by a period of each cycle where its magnitude is very small.

By measuring the time of this period of low current, an inrush condition can be identified. The detection of inrush current in the differential current is used to inhibit that phase of the low set restrained differential algorithm.

Overexcitation
Overexcitation can also be caused by an increase in system voltage or a reduction in frequency. It follows, therefore, that transformers can withstand an increase in voltage with a corresponding increase in frequency but not an increase in voltage with a decrease in frequency.

Operation cannot be sustained when the ratio of voltage to frequency exceeds more than a small amount. Protection against overflux conditions does not require high-speed tripping. In fact, instantaneous tripping is undesirable, as it would cause tripping for transient system disturbances, which are not damaging to the transformer.

An alarm is triggered at a lower level than the trip setting and is used to initiate corrective action. The alarm has a definite time delay, while the trip characteristic generally has a choice of definite time delay or inverse time characteristic.

ELECTRICITY AND ELECTRONICS FUNDAMENTAL FREE E-BOOK DOWNLOAD LINKS


A great book for beginners and expert alike. Electricity and Electronic fundamentals is a must in your collection of E-Books on the said topic of Electrical and Electronics Engineering.

An introductory text, Electricity and Electronics Fundamentals, delineates key concepts in electricity using a simplified approach that enhances learning. Mathematical calculations are kept to the very minimum and concepts are demonstrated through application examples and illustrations. 

The books span of topics includes vital information on direct current electronics, alternating current electricity and semiconductor devices as well as electronic circuits, digital electronics, computers and microprocessors, electronic communications, and electronic power control. 

Supplementary appendices provide a glossary and section on electrical safety along with an explanation of soldering techniques. 

EDDY CURRENTS AND EDDY CURRENT LOSS ON POWER SYSTEM TUTORIALS AND LINKS

Eddy currents also known as called Foucault currents are induced currents present in a conductors, wherein its direction is in opposition with the change in flux that generated them. When a conductor is exposed to a magnetic field that is dynamic (changing due to relative motion), Eddy currents will be present, as circulating flow of electrons, or a current, within the body of the conductor.

 These circulating eddies of current create induced magnetic fields that oppose the change of the original magnetic field due to Lenz's law, causing repulsive or drag forces between the conductor and the magnet. 

When a conductor moves relative to the field generated by a source, electromotive forces (EMFs) can be generated around loops within the conductor. These EMFs acting on the resistivity of the material generate a current around the loop, in accordance with Faraday's law of induction.

These currents dissipate energy, and create a magnetic field that tends to oppose the changes in the field.

For more information about Eddy currents, below are useful links related to the topic.

What Is An Eddy Current?
An eddy current is the current is induced in little swirls ("eddies") on a large conductor (picture a sheet of copper). If a large conductive metal plate is moved through a magnetic field which intersects perpendicularly to the sheet, the magnetic field will induce small "rings" of current which will actually create internal magnetic fields opposing the change. Read more...

What Are Eddy Current Losses?
The cores of power transformers are generally made of soft iron or steel. Because iron and steel are good conductors; a current can be induced into the core when the core is subjected to a moving magnetic field. Thus, unless special precautions are taken, large circulating currents will be induced into the core of the transformer. These currents are called as eddy currents. Read more...

Eddy Currents Explanation Video 



Simplified High-Accuracy Calculation of Eddy-Current Losses in Round-Wire Windings
It has recently been shown that the most commonly used methods for calculating high-frequency eddy-current loss in round-wire windings can have substantial error, exceeding 60%. Previous work includes a formula based on a parametric set of finite-element analysis (FEA) simulations that gives proximityeffect loss for a large range of frequencies, using the parameters from a lookup table based on winding geometry. Read more...

Eddy Currents on Solenoids
A phenomenon caused by the rate of change in an induced magnetic field. The relative motion causes a circulating flow of electrons or current within the conductor, leading to efficiency loss. Learn more about eddy current loss in the class "Solenoids 235" below. Read more...


INSULATION COORDINATION PRINCIPLES TUTORIALS

General outline of the insulation coordination procedure:

The procedure for insulation coordination consists of
a) Determination of voltage stresses
b) Selection of the insulation strength to achieve the desired probability of failure

The voltage stresses can be reduced by the application of surge-protective devices, switching device insertion resistors and controlled closing, shield wires, improved grounding, etc.

System transient analyses that include the selection and location of the overvoltage limiting devices are performed to determine the amplitude, waveshape, and duration of system voltage stresses.

The overvoltage stress may be characterized either by

— The maximum crest values, or
— A statistical distribution of crest values, or
— A statistical overvoltage value [this is an overvoltage generated by a specific event on the system (lightning discharge, line energization, reclosing, etc.), with a crest value that has a 2% probability of being exceeded].

The results of the transient analysis should provide voltage stresses for the following classes of overvoltage:

— Temporary overvoltage (phase-to-ground and phase-to-phase)
— Switching overvoltage (phase-to-ground and phase-to-phase)
— Lightning overvoltage (phase-to-ground and phase-to-phase)
— Longitudinal overvoltage (an instantaneous combination of switching or lightning surge and a power-frequency voltage)

To compare the overvoltages with the insulation strength, the insulation strength must be modified because of the (1) nonstandard waveshape of overvoltages and (2) nonstandard atmospheric conditions.

The dielectric strength of insulation for surges having nonstandard waveshapes is assessed by comparison to the dielectric strength as provided by standard chopped wave tests. The rules for the atmospheric correction of withstand voltages for external insulations are specified in IEEE Std 4-1995.

 For insulation coordination purposes, wet conditions are assumed and only the relative air density corresponding to the altitude needs to be taken into account.

In addition, a safety margin may be necessary based on consideration of

— Statistical nature of the test results
— Factory or field assembly of equipment
— Aging of insulation
— Accuracy of analysis
— Other unknown factors
The overall protective margin is derived from experience and further described in IEEE P1313.2.5

SWITCHING SURGES THAT AFFECT ARRESTER APPLICATION

For purposes of practical arrester application, switching surge voltages can be classiÞed according to required arrester reseal voltage capability, which depends upon the number and severity of possible surge currents discharged by the arrester and the duration of ensuing temporary overvoltages.

- Transients Where Several Sparkovers Are Permitted
These transients are usually initiated by inherent switch action and stress the surge arrester through multiple operations. The transients are repetitive in nature and may be of sufÞcient magnitude to produce sparkover many times.

The severe duty on the arrester results from the repeated follow current rather than from the energy in the surge. Heating of the gap and valve block assemblies can be excessive and hence cause arrester failure. Satisfactory performance of the surge arrester under these conditions is dominated by the capability of the switching device.

Arrester problems are best avoided through the use of switching devices that do not prestrike, restrike, or chop excessively. Alternatively, surges may be controlled by performing switching by disconnects only on de-energized systems. Some arresters may perform satisfactorily, but performance is difficult to predict.

-Transients Where Only One or Two Sparkovers Are Permitted
Operation of circuit breakers or load switches may be accompanied by rapidly decaying switching surges. Transients of this type generally stress the surge arrester through high energy dissipation requirements.

This duty can result from discharge of high-magnitude switching surges or multiple discharges of high or intermediate-level surges. The stress on the arresters is severe because, in addition to discharge of the system surge, the arrester must reseal against subsequent temporary overvoltages or normal power-frequency voltage.

In some severe applications, the surge arrester must have the ability to reseal above arrester rating
Satisfactory performance of the arrester in these conditions is typically dominated by system conditions; that is, reclosing surges are generally higher than energizing surges, and energy dissipation from long lines is greater than from short lines.

In addition, surge suppression by power circuit breaker preinsertion resistors is commonly used at EHV and generally not at HV. Switching of a transmission line and a transformer may produce more severe temporary overvoltages following the initial surge than switching without a transformer connected.

 Restriking of circuit breakers on capacitor switching or line dropping will generally produce severe duty on surge arresters.

-Transients Where Temporary Overvoltages Approach Reseal Capability of the Surge Arrester
Temporary overvoltages that are sustained for more than a few cycles are an important consideration in surge arrester application. These overvoltages should not exceed the arrester’s ability to reseal so that multiple operations of the arrester will not occur if the arrester is sparked over by an impulse or spontaneous sparkover of the arrester.

Failure to reseal would result in multiple operations with power-follow current and failure of the arrester. Successful performance of the arresters is based on assurance that the temporary overvoltages will be less than the reseal capability of the surge arrester.

Overvoltages can be controlled or influenced by system grounding, system configuration, as well as generator excitation controls in the case of load rejection. Resonance or ferroresonance conditions should be prevented by avoiding system conditions that produce the overvoltage.

VOLTAGE SURGES DURING DE-ENERGIZING MOTORS TUTORIALS

De-energizing motors can produce surges that may adversely affect motors under certain conditions, much as when the motor is de-energized before it has come up to speed (aborted starts) or when a vacuum breaker is used to do the switching. When air-magnetic switchgear is used to de-energize a motor that is running under normal operating conditions, no significant surges are produced.

This is true because the back emf of the motor after it is disconnected does not immediately go out of-phase with the source side voltage. Therefore, the recovery voltage across the breaker is not severe and restrikes do not usually occur.

However, when a breaker is tripped before the motor comes up to speed, the back emf is low and the recovery voltage can be severe. Thus, restrikes are likely to occur causing severe surges. These surges can have magnitudes above 2.7 pu with front times of 1 μs or less.

When vacuum breakers are used to switch motors, several problems can occur such as current chopping, virtual current chopping, and multiple reignitions. Current chopping is the forcing of a premature current zero by the switching device.

When the load being switched is inductive, the energy stored in the magnetic field at the time of the forcing of a current zero is converted to energy stored in an electric field. If the capacitance of the system is low, this can result in quite high surge voltages.

The surge voltage magnitude is proportional to the amount of current chopped and to the surge impedance of the circuit on the load side of the vacuum breaker. The current chopping performance of vacuum breakers has been improved by the development of new contact materials, such as chromium-copper, which chop and interrupt at lower currents.

Published data indicate that current chopping overvoltages to ground during switching of normal motor load current do not exceed 3 pu when the vacuum breaker has chromium-copper contacts.

Virtual current chopping occurs because of the ability of vacuum breakers to interrupt at high frequency current zeroes. When the first phase of a vacuum breaker opens, it is possible to get a reignition or restrike of the current in that phase. This can produce a high-frequency current oscillation in the other two phases that have yet to interrupt.

If the superposition of the high-frequency current onto the 60 Hz current results in the total current passing through zero in one of these other phases, then that phase may interrupt. This is very much like chopping the fundamental frequency component of current.

The amount of current that can be virtually chopped is larger than the amount of current that is chopped during normal load current chopping. The surges produced can be severe if a number of parallel load feeders are on-line on the same supply bus.

However, if the surge impedance upstream of the breaker is high or equal compared to the load side, the virtually chopped surges are comparable to or somewhat larger than those produced by normal current chopping. This phenomenon generally has a low probability of occurrence.

Multiple reignitions in a vacuum breaker are a relatively infrequent occurrence that may result from certain combinations of inductance and capacitance in the circuit. A vacuum breaker can interrupt on the first highfrequency oscillation current zero after the contacts have parted. Therefore, the contacts may still be close together and the dielectric withstand of this small gap may be relatively low.

If the system recovery voltage builds up fast, a reignition may occur. When the arc is reestablished, it will not extinguish until the next current zero. This may happen quite quickly because the vacuum breaker is a good interrupter at high frequency current zeroes.

When the arc is extinguished, the contact gap may still be small. Another reignition of the opposite high-frequency polarity may occur. This can be repeated. The surge voltages due to re ignitions can build up with each succeeding re ignition.

The front times of such surges can be short (steep fronts) and can damage motor turn insulation. It is the steep fronts caused by the high frequency with reignition amplification that are likely to puncture turn insulation, rather than just high voltage.

Because some vacuum circuit breakers and interrupters may create high voltages by chopping, prestrikes, or restrikes, some manufacturers have equipped vacuum switchgear with surge limiting arresters on the switchgear bus or on the load side of each outgoing interrupter. For protection of switched machines, the arresters should be on the machine circuit rather than on the bus.

MOTOR SURGE PROTECTION STRATEGIES TUTORIALS

If one or more of the following surge protective elements exist for a particular motor application, the need for additional surge protection may not be necessary. Some of these listed elements will be effective for reducing stress on the groundwall insulation and some will be effective for protecting the turn insulation.

Some of the elements will be effective for motor starting surges while others will be effective in limiting stress from lightning surges and system switching surges. For a particular machine installation a quantitative evaluation such as is presented in this guide is required to determine whether protective coordination with the insulation withstand is achieved.

a) Effective shielding from lightning strokes to overhead lines supplying the building or plant can
reduce the probability of a lightning surge overstress.

b) Gapless metal-oxide surge arresters at the motor terminals can limit the magnitude of voltage stress without creating a steep-front as caused by sparkover of a gapped arrester.

c) Surge capacitors at the motor terminals. (NOTE—Three-phase capacitors have failed much more frequently than single-phase capacitors); capacitor internal inductance plus the inductance of leads as long as one meter can isolate the capacitor from the motor during steep-front starting surges, and may not be effective in wavefront sloping. Surge arrester lead length is not as critical when machine protective arresters are applied together with short lead length capacitors, because the capacitors will lengthen the rise time applied to the arrester lead inductance.

d) Low grounding resistance at the motor-starting switchgear, in the order of one-fifth of the phase
mode surge impedance, Zc+, of the motor supply cable. (Table 6 lists Zc+ for large and small sizes of 5 kV cable: triplexed shielded in tray, triplexed unshielded in conduit, belted unshielded in tray, and single phase unshielded in tray. This list indicates that for usual cable surge impedances, Zc+ will vary between 7 to 70 Ω. Low grounding resistance, to be effective, should be in the order of  1.5 Ω for low Zc+ constructions, and less than 15 Ω for high Zc+ constructions).

e) Interconnected bonds to ground between the motor frame, the surge arrester, and the surge capacitor.

f) Motor supply cables individually shielded with outer jackets that effectively isolate the shields from the raceway, and the shields bonded at only one end (only at the motor end) to the metallic raceway and to the motor frame and to a low impedance ground or earthing system. (This shield bonding configuration can reduce the surge at the motor by as much as 60% compared to bonding the shields at both ends).

The surge arrester should be selected to limit the magnitude of the surge voltage to a value less than the motor insulation surge withstands, BIL. The steepness of the surge wavefront at the motor terminals is influenced by two time constants: at the supply end by the effect of system inductance, grounding resistance, and motor cable impedance; at the motor end by cable impedance and motor capacitance.

Surge capacitors at the motor increase the time constant and lengthen the time to crest, reducing the steepness of the surge voltage wavefront. As the surge voltage wavefront travels through the winding, the surge voltage between adjacent turns of the same phase will be less for a wavefront having a longer rise time.

The surge arrester should be selected to limit the magnitude of the surge voltage to a value less than the motor insulation surge withstands, BIL. The steepness of the surge wavefront at the motor terminals is influenced by two time constants: at the supply end by the effect of system inductance, grounding resistance, and motor cable impedance; at the motor end by cable impedance and motor capacitance.

Surge capacitors at the motor increase the time constant and lengthen the time to crest, reducing the steepness of the surge voltage wavefront. As the surge voltage wavefront travels through the winding, the surge voltage between adjacent turns of the same phase will be less for a wavefront having a longer rise time.

ELECTROSTATIC VOLTMETERS TUTORIALS AND REFERENCE LINKS


Electrostatic Voltmeter or sometimes called Surface DC Voltmeter are instruments that measure voltage even without the actual transfer of electric charge. These devices can measure voltages through close proximities of the probe, to the measured quantities.

This device is an answer to the uncertainty principle problem of measuring data. When measuring voltage distribution on a dielectric surface, any measurement technique that requires charge transfer, no matter how small, will modify or destroy the actual data. Thus Electrostatic Voltmeters may come in handy.

Below are links on the topic Electrostatic Voltmeters to help you understand more on the topic.

Using Electrostatic Voltmeters
Static problems are challenging to solve because static dissipaters, such as ionizing strings or static bars, should be located to treat the side of the film with static. An electrostatic voltmeter provides detailed information on the location, the amount, and the polarity of static. Specifically, an electrostatic voltmeter can verify which side of a film has static, and it can reveal when a film has suffered static discharges in previous operations. Read more...

How To Use an Electrostatic Voltmeter
Measuring static is important so we can understand the problem, identify possible solutions, and assess the feasibility and effectiveness of our alternatives. There are at least three different types of instruments that we can use to measure static: an electrostatic fieldmeter, the workhorse for diagnosing static problems; a Coulomb meter, which measures charge on objects or film samples that fit within a Faraday cup; and a non-contacting electrostatic voltmeter, which measures the surface potential of a film. Read more...

HANDBOOK OF ELECTRIC MOTORS FREE EBOOK DOWNLOAD LINK


Reviews

it is the most comprehensive electric motor handbook available currently, extensively covering all types of motors … . Recommended for upper level undergraduates, graduates, researchers and practitioners.
- E-Streams, Vol. 7, No. 12, December 2004

Its strong point is that is contains a fantastic wealth of design information on all kinds of motors…It gives the reader a very good understanding of a broad range of modern motor technology…Anyone who designs or works with motors of all types would definitely find this book to be an excellent handbook and guide for understanding the details of motor design and being able to choose the correct motor for a given application.
- IEEE Electrical Insulation Magazine, Vol. 21, No. 3, May/June 2005

Product Description
Presenting current issues in electric motor design, installation, application, and performance, this second edition serves as the most authoritative and reliable guide to electric motor utilization and assessment in the commercial and industrial sectors.

Covering topics ranging from motor energy and efficiency to computer-aided design and equipment selection, this reference assists professionals in all aspects of electric motor maintenance, repair, and optimization.

It has been expanded by more than 40 percent to explore the most influential technologies in the field including electronic controls, superconducting generators, recent analytical tools, new computing capabilities, and special purpose motors.

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BASIC ELECTRICAL ENGINEERING FREE EBOOK DOWNLOAD LINK


A good book that covers the following topics:

Concept of e.m.f., p,d.; and Current Resistance; Effect of Temperature on Resistance. Resistance temperature Coefficient; Insulation Resistance; S.I. Units of Work; Power and Energy Conversion of Energy from One Form to Another in Electrical; Mechanical and Thermal Systems. Batteries and Cells; Their Types; Current Capacity and Cell Ratings; Charging and Discharging of Batteries; Series and Parallel Battery Connections; Maintenance Procedure. Classification of Electric Networks; Ohm's Law; Kirchhoff"™s Laws and Their Applications for Networks Solutions Simplification of Networks Using Series and Parallel Combinations and Star-Delta Transformation; Superposition Theorem; Thevenin's Theorem; Norton's Theorem and Maximum Power Transfer Theorem

LIGHTNING ARRESTER - WHAT IS LIGHTNING ARRESTER AND HOW LIGHTNING ARRESTER WORKS?


There are two basic voltage surge that may cause damage to the system and its corresponding equipment and apparatus. These are:

1. Switching Surge
2. Lightning Surge

Switching Surge - These are voltage abnormalities that are caused by changes in the operating state of the power system, that involves switching (literally) of breakers, disconnect switches, and other switch gears. It happens as trapped energy are released during the event.

Lightning Surge - These are voltage abnormalities caused by the phenomenon of lightning. Damaged may be experienced through direct stroke or hit, or by induced voltages. Lightning are harmful, and runs in millions of voltages, which makes the equipment vulnerable without protection.

The risk of having your equipment exposed to both of these abnormalities can be greatly reduced with the application of surge arresters. Not to be confused, surge arresters refers to devices which could protect from the aforementioned abnormalities.

Lightning arresters on the other hand are specifically named protection device, designed more for lightning protection, but in itself is capable enough to protect it from switching surge.

Below are selected article links to help you understand further what is a lightning arrester and how lightning arrester works:

WHY WORRY ABOUT LIGHTNING?
It is unfortunate, but a fact of life, that computers, computer related products and process control equipment found in premises data communications environments can be damaged by high-voltage surges and spikes. Such power surges and spikes are most often caused by lightning strikes. These causes may include direct contact with power/lightning circuits, static buildup on cables and components, high energy transients coupled into equipment from cables in close proximity, potential differences between grounds to which different equipment’s are connected, miswired systems and even human equipment users who have accumulated large static electricity charge build-ups on their clothing. Read more...

WHAT IS A LIGHTNING ARRESTER?
A lightning/surge arrester is a device that protects structures from electrical damage by intercepting lightning surges and diverting them to the ground. Lightning arresters are connected directly to the ground via low resistance cables, although they are generally mounted on high buildings or other structures in order to attract electricity. Read more...


How do Lightning Arresters Protect Power Systems?
Although Lightning Rods are devices that divert lightning surges to ground, they are simple conductive terminals that are always at ground potential and are never energized. Read more...


Lightning Arresters A Guide to Selection and Application 
Surge protection has been a primary concern when connecting devices and equipment to  low-, medium-, or high-voltage electrical systems.  As the use of products and equipment with components and insulation systems vulnerable to voltage surges and spikes continues to increase, the requirement for surge arresters to protect against the effects due to lightning strikes, switching phenomenon, etc., continues to increase as well.
Read more...

Analysis and Design Selection of Lightning Arrester for Distribution Substation
Distribution substations feed power to the actual consumers through distributors and service lines. The main equipments are generators and transformers. To protected these equipment and for stability purpose, over voltages and over currents protection are important to consider. Lightning is  one of the most serious causes of over voltage. If the power equipment especially at outdoor substation are not protected, the over voltage will cause burning of insulation. Lightning arrester can protect the damages of equipment. Read more...

HOW TO LOCATE FAULTS ON POWER CABLE INSTALLATION TUTORIALS


In electric power distribution systems, a wide variety of cable faults can occur. The problem may be in a communication circuit or in a power circuit, either in the low- or medium-voltage class.

Regardless of the class of equipment involved or the type of fault, the one common problem is to determine the location of the fault so that repairs can be made.

The vast majority of cable faults encountered in an electric power distribution system occur between conductor and ground. Most fault-locating techniques are made with the circuit deenergized.

In ungrounded or high-resistance grounded, low-voltage systems, however, the occurrence of a single line-to-ground fault will not result in automatic circuit interruption; therefore, the process of locating the fault may be carried out by special procedures with the circuit energized.

Once a line-to-ground fault has occurred, the resistance of the fault path can range from almost zero up to millions of ohms. The fault resistance has a bearing on the method used to locate the failure.

In general, a low-resistance fault can be located more readily than one of high resistance. In some cases, the fault resistance can be reduced by the application of voltage sufficiently high to cause the fault to break down as the excessive current causes the insulation to carbonize.

A wide variety of commercially available equipment and a number of different approaches can be used to locate cable faults.  The method used to locate a cable fault depends on the following:
a) Nature of fault
b) Type and voltage rating of cable
c) Value of rapid location of faults
d) Frequency of faults
e) Experience and capability of personnel

Megohmmeter Instrument Test
When the fault resistance is sufÞciently low that it can be detected with a megohmmeter, the cable can be sectionalized and each section tested to determine which contains the fault. This procedure may require that the cable be opened in a number of locations before the fault is isolated to one replaceable section. This could, therefore, involve considerable time and expense, and might result in additional splices. Since splices are often the weakest part of a cable circuit, this method of fault locating may introduce additional failures at a subsequent time.

Conductor Resistance Measurement
This method consists of measuring the resistance of the conductor from the test location to the point of fault by using either the Varley loop or the Murray loop test. Once the resistance of the conductor to the point of fault has been measured, it can be translated into distance by using handbook values of resistance per unit length for the size and conductor material involved, correcting for temperature as required.

Capacitor Discharge
This method consists of applying a high-voltage and high-current impulse to the faulted cable. A high-voltage capacitor is charged by a relatively low-current capacity source such as that used for high-potential testing. The capacitor is then discharged across an air gap or by a timed closing contact into the cable. The repeated discharging of the capacitor provides a periodic pulsing of the faulted cable. The maximum impulse voltage should not exceed 50% of the allowable dc cable test voltage since voltage doubling can occur at open circuit ends. Where the cable is accessible, or the fault is located at an accessible position, the fault may be located simply by sound.

Tone Signal
A tone signal may be used on energized circuits. A Þxed-frequency signal, generally in the audio frequency range, is imposed on the faulted cable. The cable route is then traced by means of a detector, which consists of a pickup coil, receiver, and a head set or visual display, to the point where the signal leaves the conductor and enters the ground return path.

This class of equipment has its primary application in the low-voltage Þeld and is frequently used for fault location on energized ungrounded circuits. On systems over 600 V, the use of a tone signal for fault location is generally unsatisfactory because of the relatively large capacitance of the cable circuit.

Radar System
A short-duration, low-energy pulse is imposed on the faulted cable and the time required for propagation to and return from the point of fault is monitored on an oscilloscope. The time is then translated into distance to locate the fault. Although this equipment has been available for a number of years, its major application in the power field has been on long-distance, high-voltage lines.

ELECTRIC POWER SYSTEM: A CONCEPTUAL INTRODUCTION FREE EBOOK DOWNLOAD LINKS

A clear explanation of the technology for producing and delivering electricity

Electric Power Systems explains and illustrates how the electric grid works in a clear, straightforward style that makes highly technical material accessible. It begins with a thorough discussion of the underlying physical concepts of electricity, circuits, and complex power that serves as a foundation for more advanced material. 

Readers are then introduced to the main components of electric power systems, including generators, motors and other appliances, and transmission and distribution equipment such as power lines, transformers, and circuit breakers. The author explains how a whole power system is managed and coordinated, analyzed mathematically, and kept stable and reliable.

Recognizing the economic and environmental implications of electric energy production and public concern over disruptions of service, this book exposes the challenges of producing and delivering electricity to help inform public policy decisions. Its discussions of complex concepts such as reactive power balance, load flow, and stability analysis, for example, offer deep insight into the complexity of electric grid operation and demonstrate how and why physics constrains economics and politics.

Although this survival guide includes mathematical equations and formulas, it discusses their meaning in plain English and does not assume any prior familiarity with particular notations or technical jargon. Additional features include:
* A glossary of symbols, units, abbreviations, and acronyms
* Illustrations that help readers visualize processes and better understand complex concepts
* Detailed analysis of a case study, including a Web reference to the case, enabling readers to test the consequences of manipulating various parameters

With its clear discussion of how electric grids work, Electric Power Systems is appropriate for a broad readership of professionals, undergraduate and graduate students, government agency managers, environmental advocates, and consumers.

FUNDAMENTALS OF ELECTRIC CIRCUITS FREE EBOOK DOWNLOAD LINK


Alexander and Sadiku's Fundamentals of Electric Circuits continues in the spirit of its successful previous editions, with the objective of presenting circuit analysis in a manner that is clearer, more interesting, and easier to understand than other, more traditional texts.

 Students are introduced to the sound, six-step problem solving methodology in chapter one, and are consistently made to apply and practice these steps in practice problems and homework problems throughout the text.

A balance of theory, worked examples and extended examples, practice problems, and real-world applications, combined with over 350 new homework problems for the fourth edition and robust media offerings, renders the fourth edition the most comprehensive and student-friendly approach to linear circuit analysis.

This is a very fine book. It explains the concepts very clearly and maybe used for signals too, when studying fourier and laplace transforms. The authors do a superb job and make challenging concepts sound easy for the student. Extremely organized and well prepared book.

About the Author
Dr. Charles K. Alexander (Athens, OH) is a Professor of Electrical Engineering and Computer Science at the University of Ohio and served as the President and CEO of the IEEE from 1996-1999.

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AMERICAN ELECTRICAN'S HANDBOOK FREE EBOOK DOWNLOAD LINK


The most popular electricians' handbook for the past 95 years has been completely updated to provide the latest NEC and NESC rules and standards, and new references to solar power, photovoltaics, induction lighting, and more. Providing all the information you'll need to design, maintain, and operate systems and equipment, American Electricians' Handbook is the key to tackling even the most complex jobs with complete confidence. 

This one-stop resource focuses on systems and equipment rather than codes and calculations, making it the most practical, hands-on guide available. No matter what kind of electrical project you plan to take on, the American Electricians' Handbook is the only guide you'll need.

American Electrician's Handbook covers:

Solar power and photovoltaics
Variable- and adjustable-speed drives
Variable-speed-drive programming
Continuous load calculations
Induction lighting
New NEC and NESC rules
NEMA motor and generator standards
Voltage drops in circuits with non-unity power factors

Inside: • Fundamentals • Properties and Splicing of Conductors • Circuits and Circuit Calculations • General Electrical Equipment and Batteries • Transformers • Solid-State Devices and Circuits • Generators and Motors • Outside Distribution • Interior Wiring • Electric Lighting • Optical Fiber • Wiring and Design Tables

From the Back Cover
Keep up with developments in the electrical field with the latest edition of the "electricians' bible." Filled with practical advice and facts, the new edition of this standard reference will enable you to do your job with complete confidence. 

Revised and updated in compliance with the current National Electrical Code standards, as well as those of NEMA, the National Electrical Safety Code, American National Standards, and Underwriters Laboratory, the book shows you how to select, install, maintain, and operate all types of electrical equipment and wiring. 

Using the clear language and diagrams that have helped make the Handbook the definitive Thirteenth Edition brings you the latest data on: Advances in solid-state technology; The most up-to-date techniques for splicing conductors, plus a look at new types of building wires and cables; new information on high efficiency motors and electronic control of motors; Recently developed tools, equipment, and other products available from manufacturers; Plus information on circuits and circuit calculations, transformers, wiring tables, lamp application tables, and much more. --This text refers to an out of print or unavailable edition of this title.

THE INDUSTRIAL ELECTRONICS HANDBOOK FREE EBOOK DOWNLOAD LINKS


The field of industrial electronics covers a plethora of problems which must be solved in industrial practice. Electronic systems control many processes that begin with the control of relatively simple devices like electric motors, through more complicated devices such as robots, to the control of entire fabrication processes.

An industrial electronics engineer works with many physical phenomena as well as the sensors which are used to measure them. Thus the knowledge required by this type of engineer is not only traditional electronics but also specialized electronics, such as those required for high power applications. 

The importance of electronic circuits extends well beyond their use as a final product in that they are also important building blocks in large systems. Therefore, the industrial electronics engineer must also possess knowledge of the areas of control and mechatronics. 

Since most fabrication processes are relatively complex, there is an inherent requirement for the use of communication systems that not only link the various elements of the industrial process, but are tailor-made for the specific industrial environment.

Finally, the efficient control and supervision of factories requires the application of intelligent systems in a hierarchical structure to address the needs of all components employed in the production process. This latter need is accomplished through the use of intelligent systems such as neural networks, fuzzy systems or evolutionary methods. 

The Industrial Electronics Handbook, now in its second edition, addresses all these issues in five separate volumes which can be purchased individually or as a set: Fundamentals of Industrial Electronics, Industrial Communication Systems, Intelligent Systems, Power Electronics and Motor Drives, and Control and Mechatronics.

ELECTRICAL POWER SYSTEMS QUALITY FREE EBOOK DOWNLOAD LINK


An excellent reference on power quality. Nicely organized, starting with terms and definitions, and finishing with advice on making measurements.

Very readable, with minimal use of equations, and maximum use of sketches, drawings, and graphical data. A must have for every power quality professional
Product Description

* Basic power quality strategies and methods to protect electronic systems

* Nearly twice the size of the last edition--new chapters on distributed generation and benchmarking--over 200 pages of new material

This is a very good handbook for not only power quality professional,but also electrical engineers. With well organized chapters, it covered comprehensive knowledge of power quality and relevant experience of authors. I really hope it can be translated into Chinese and let more power quality professionals share this valuable resource.

ELECTRICAL THEORY AND TECHNOLOGY FREE EBOOK DOWNLOAD LINKS


Electrical Circuit Theory and Technology is a fully comprehensive text for courses in electrical and electronic principles, circuit theory and electrical technology. The coverage takes students from the fundamentals of the subject, to the completion of a first year degree level course.

Thus, this book is ideal for students studying engineering for the first time, and is also suitable for pre-degree vocational courses, especially where progression to higher levels of study is likely.

' Providing a complete text for first year Circuit Theory modules.'

' enablles students to grasp techniques and principles '
' Provides a new text for all students studying electrical and electronic engineering'
' This book bridges these differences by building from the basics reqired at Technician level'
'This book will also be popular with HNC/D students looking for a single comprehensive text-book.
' Ideal for students looking for progression in their studies.'
'Enables students to grasp important techniques and principles without abstruse theoretical explaination'
' A free instructors manual provides fully worked solutions for all these questions as well aas photocopiable formula sheets --This text refers to an out of print or unavailable edition of this title.

Book Description
Provides a comprehensive introduction to electrical and electronic principles for students taking undergraduate and vocationsl courses.

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