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

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

List of device numbers and acronyms BY Alphabetical

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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


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


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

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

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

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

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

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

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

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

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

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

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


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

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

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

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


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


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


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


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

or circuit being protected.

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


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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


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

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

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


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

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


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

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

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

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

RESERVED FOR FUTURE APPLICATION - 16

RESERVED FOR FUTURE APPLICATION - 11

(USBR assigned – Control Power Transformer).

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

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

RESERVED FOR FUTURE APPLICATION. - 61

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

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

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

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

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

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

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

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

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


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


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

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

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

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

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

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

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

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

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

Types of Electrical Testing Equipment Instruments Uses and Its Definition

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

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

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

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

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

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

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

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

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

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

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

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

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

WHAT IS Electrical Power System Quality With Terms and Definitions

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

What is..

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

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

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


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

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

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


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

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


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

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

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

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

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

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

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

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

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

Nuclear Power Plant Advantages and Disadvantages

What Are Advantage and Disadvantages of Nuclear Power Plant

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

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


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

Free Download The Danger of Nuclear Power Plant

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

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


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

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

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

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

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

How Does Electric Tractions Works? Question and Answer

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

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

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

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

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

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

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

Question and Answer of Electric Traction

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

Transformer Built In Protection and Cooling Tutorials

Protection Devices Built In For Safe Operation of A Transformer

Conservator

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

Breather

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

Temperature Gauge

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

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

Pipes

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

Important Facts About Transmission and Distribution Transformer

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

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

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

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

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

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

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

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

9. Transformer is used to change the valuesof voltage.

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

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

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

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

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

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

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

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

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

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

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

Cooling Of Transformer

Natural Cooling

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

Natural Oil Cooling

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

Oil Blast Cooling

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

Force Water Cooling

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

Force Air Cooling

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

is a scarcity of water.

Power Transformer Tutorials Links

Tutorials on Electrical Power Factor Correction

All About Power Factor Links

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

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

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

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

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

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

Power Factor Question and Answer

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

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

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

All About Electrical Distribution and Power Transformer Tutorials

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

Transformer Classification

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

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

The Testing of the Transformer

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

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

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

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

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

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

All About Electrical and Electronics Measurement Facts and Tutorials

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

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

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

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

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

Damping provides braking action on a meter pointer.

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

Moving coil instruments are used in DC circuits only.

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

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

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

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

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

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

Meter accuracy is determined by full scale deflection.

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

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

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

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

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

Eddy current damping methods is common in moving coil instruments.

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

A moving iron type instrument has a nonlinear scale.

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

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

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

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

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

A wattmeter can measure AC as well as DC power.

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

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

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

Meggar is an instrument to measure insulation resistance.

The cell used in a potentiometer is a lead accumulator.

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

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

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

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

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

A multimeter consists of voltmeter, current meter and ohmmeter.

Sensitivity of a voltmeter is expressed as Ohms/Volt.

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

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

weight ration and third is its frequency range is low.

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

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

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

All About Electromagnetic Induction Facts and Tutorials

Key Facts of Electromagnetic Induction

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

A Degaussing is the process of the demagnetizing metallic part.

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

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

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

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

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

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

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

The coupling coefficient denotes the degree of magnetic linkage.

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

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

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

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

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

Leakage factor is more than unity.

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

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

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

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

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

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

Current Electricity Flow of Electrons Engineering Tutorials

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

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

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

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

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

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

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

All About Electrical Relays, Principles, Classification and Requirements

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

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

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

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

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

All About Electrolysis and Batteries Facts and Tutorials

1. The two main defects of the primary cells are local action and polarization.
2. Local action in the primary cell can be rectified by amalgamating the zinc electrode with mercury.
3. One factor affecting voltages of the primary cell is the types of plates and electrolyte.
4. Distilled or approved water is used in electrolytes because it prevents or slows down local action.
5. In electroplating, the positive electrode is called the anode.
6. The mass of an ion liberated at an electrode is directly proportional to the quantity of electricity which passes through the electrolyte. This statement is associated with laws of electrolysis.
7. The mass of material deposited over an electrode is proportional to quantity of electricity and electro chemical equivalent.
8. The condition of a secondary cell can be determined by the terminal voltage and strength of the electrolyte.
9. Nickle-cadium dry cell is becoming popular in power supplies for electronic calculators because it is rechargeable.
10. One advantage of a secondary cell is that it can be recharged.
11. Cell are connected in parallel to increase the current capacity.
12. Cells are connected in series to increase voltage output.
13. To obtain a high voltage of about 1.9 volts from a dry cell on would use magnesium cell.
14. While charging a battery, charge the battery in an airy room, remove the vent plugs during charging, keep flames etc. away from the battery and keep the charging current rate not more that 3 to 6 amperes.
15. If the internal resistance of a discharged battery is more it is not desirable to leave a lead storage battery in a discharged state for a long time mainly because plates will become sulphated.
16. To keep the terminals of a lead acid storage battery free from corrosion, it si advisable to keep the electrolyte level low.
17. If a sixty ampere hours battery has sixty seven ampere discharge rate, it will provide a current of six amperes for ten hours.
18. The ampere hour capacity of battery depends on the area of the plates.
19. Electrolyte of a storage battery is formed by adding suphuric acid to water.
20. Other types of accumulators besides the lead acid type are nickle cadmium batteries.
21. Electro-chemical equivalent is mass of the element liberated per unit of quantity of hydrogen.
22. Impurities in an electrolyte can cause an internal short circuit condition called local action.
23. The action of a dry cell is to change chemical action to electrical energy.
24. Polarization in dry cell can be got rid of by chemical means.
25. Gassing occurs in the process of charging an accurnuiator.

Terms used in Electrolysis

Anode
The plate or electrode through which the current enters the electrolyte or it may be defined as the plate or electrode connected to the positive terminal of supply.

Anions
The ions having negative charge are known as anions.

Atom
An atom is the smallest particle of matter which takes part in a chemical action.

Atomic weight
The atomic weight of an element is the relative weight of its atom compared with that of an atom of hydrogen. The atomic weight of H atom is taken as unity.

Cathode
The plate or electrode through which the current leaving the electrolyte or the plates connected to the negative terminal of supply mains.

Cations
The ions having positive charge are known as cations.

Chemical equivalent
The chemical equivalent of an element is the mass which is chemically equivalent to a unit mass of hydrogen.

Ions
When the current is passed through electrolyte, the electrolyte gets chemically decomposed, molecules of the electrolyte splits up into two parts known an ions.

Molecule
The molecule is the smallest particle of any substance which is capable of separate existence in a chemical form.

Valency
The valency of an element is the number of hydrogen atoms with which it will combine or with which it will replace in a compound.

Things You Should Know About Direct Current Generator Tutorials

The Definition
We know that Direct Current Generator is a machine which converts the mechanical energy into electrical energy. The generator is usually driven by a steam  engine or a diesel engine or an electric motor which are called prime movers.

The Principle
The principle of Direct Current Generator is it works on the principle of Faraday's Laws of electromagnetic induction. According to this law the conductors or armature are rotated in the magnetic field and electro magnetic force is induced in these conductors which is collected from the commutators fitted on the shaft of armature.

The Loop
The simple loop of a Direct Current Generator when the plane of the coil is at right angles to the lines of flux, the flux linked with the coil is maximum but the rate of change of flux linkage is minimum. As coil continues to rotate further, the rate of change of flux linkage increases, till it attains maximum value of 90 degree to 180 degree, the flux linked with the coil gradually increases resulting in decrease in induced electro motive force till it reduces to zero at 180 degree. A reversal of the trend occurs during next half revolution. For unidirectional current, the ends of the coil are connected commutation whose function is to reverse the connections to the rotating coil through fixed brushes and to collect the electro motive in one direction.

Four Reasons for failure of a generator to build voltage:
1.Defective contact of brushes with conmmutator due to dirt, insufficient pressure, tight brushes, dirty or rough commutators or projecting intersegment micas.
2. High resistance or open circuit in the shunt field circuit, faulty contact or burnt resistance in shunt regulators.
3. Loss of residual magnetism.
4. Reverse field connection or reversed speed.

Ten Reasons for sparking and Bad Bommutations:
1. Overload
2. Projecting intersegment micas.
3. Earth fault on armature
4. Armature short circuit
5. Incorrect brush position
6. Wrong grade of brushes
7. Reversed interpole coils
8. Brushes not properly bedded
9. Brushes not equally spaced
10. Worn Brushes

Question and answer about D.C. Generator
1. The armature of a DC generator is laminated to reduce eddy current loss.
2. In a shunt generator the voltage built up is generally restricted by the saturation of iron.
3. Copper loss in DC generators varies with load.
4. Full load efficiency of the generators is 92.51 percent.
5. Shunt generators are preferred for parallel operations.
6. In DC generator the ripples in the direct electro motive force generated are reduced by using commutator with large number of segments.
7. The functions of an interpole is to neutralize crossfield of armature reaction and obtain ideal commutation.
8. Equalizer connection are required when paralleling two compound generators.
9. A simple method of increasing the voltage of DC generator is to increase the speed of rotation.
10. In the commutation process it is the current which is getting reversed.

25 Tips You Need To Know About Current Electricity Engineering

1. The curve representing Ohm's law in linear.
2. The condition in Ohm's Law is that the temperature should remain constant.
3. The Ohm's Law can be applied with certain reservations to electrolytes.
4. The presence of an electric current is made known by the effects produced.
5. An electric current can neither be seen nor touched.
6. Three important effects produced by the presence of a current heating, magnetic and electric shock.
7. Thermistor has negative coefficient of resistance.
8. International ohm is defined in terms of resistance of a column of mercury.
9. Resistors commonly used in power circuits are wire wound resistors.
10. When current flows through a heater coil it glows but the supply wiring does not glow because the resistance of heater coil is more than that of supply wires.
11. If the voltage applied across an electric press is reduced by 50 percent, the power consumed by the press will be reduced by is 25 percent.
12. In a parallel circuit the potential difference across the resistance is always constant.
13. In a series circuit the current is constant.
14. Voltage applied across a circuit acts as a force.
15. The resistance of carbon filament in carbon-filament lamps increases when its temperature is decreased.
16. The heating effect of current has an undesirable side effect in a vacuum cleaner.
17. When current flows in a conductor, the heat is produced because of inter atomic collision.
18. The temperature coefficient of a conductor is defined as the increase in resistance per ohm pwer degree centigrade.
19. The value of Joule's mechanical equivalent of heat,is equal of 4.2 Joules per calorie.
20. It was experimentally found by James Precott Joule that the heat produced in a current carrying conductor is proportional to the square of current.
21. The resistance of a conductor increases when its temperature is increased.
22. The specific resistance, depends upon the nature of the material of the conductor only.
23. Resistance of a conductor increases when its length increases.
24. The resistance of conductor is the hindrance by which the conductor opposes the flow of the current.
25. The minimum requirements to cause the flow of current are a voltage source and a conductor

Transmission and Distribution Lines Key Facts and Tutorials

Key Facts and Tutorials On Electrical and Distribution Lines

1. The economical section of a feeder can be obtain by applying Kelvin's law.
2. There should be be no break in the neutral, which is usually earthed at the supply end, of a two wire Alternating Current distribution system because excess current protection would be affected.
3. In actual practice the potential at the two feeding points is unequal. To calculate the voltage drop, the difference in potential is converted into ampere metres and the moments of the lower feeding point start from this initial value.
4. Uniformly loaded distribution fed at equal potential from both ends is treated like the distributor because the voltage drop is exactly halved.
5. Voltage drop in a uniformly loaded distributor fed at once end is calculated by assuming the whole of the load concentrated at middle point.
6. For Alternating current distribution the power factor of the load has to be taken into consideration and the calculations become cumbersome. The approximate method which gives results with in plus or minus five percent of the actual voltage drop involves calculating the centre of gravity of the load, resistance and reactance per double run and average power factor.
7. To determine the distribution of load at the point of minimum potential, the moments in ampere metres about of the feeding points must be equal to the moment in ampere metres about the other feeding point.
8.At the point of minimal potential in a distributor fed from both ends, the load at the point is supplied from right and left hand feeding points.
9. With point loads in a distributor fed at both ends, in order to determine the maximum voltages drop it is necessary to know the point of minimum voltage.
10. For a three wire Direct Current distributor fed at one end, if the total voltage drop in the neutral is positive it is added to the positive drop and deducted from the negative drop.

Limitation of high transmission voltage
a. Increased cost of line support
For high transmission voltage, the insulation required between the conductors and the earthed tower is more. This increases the cost of line supports.
b. High towers:
For high transmission voltage, the clearance between conductors and groundo should be more. Therefore, higher lower is required.
c. Longer cross arms:
FOr higher transmission voltage, distance between the conductors should be more. Therefore, longer arms are required.

All About Magnetism and Electromagnetism How It Works

All About Magnetism and Electromagnetism How it works Tutorials
Magnet
A magnet is a substance that attracts pieces of iron. The phenomenon by which this attraction takes place is called magnetism.

Magnets are two types
Natural Magnets
The natural magnets are those iron ores which are obtained from mine and have the property of attracting iron pieces naturally.

Artificial magnets
The artificial magnets are those which are created by artificial means. An artificial magnet can be further divided into two types are temporary magnets and permanent magnets.

Temporary magnets
A temporary magnet is that in which magnetism remains temporarily. If a wire is wound on a soft iron piece and direct current is passed through the wire, then soft iron piece becomes a temporary magnet. It is because the iron piece will retain magnetism so long as the current is flowing.

A Permanent magnets are made from steel which is in general harder than soft iron apart from steel, alloys like cobalt steel, tungsten steel, etc. are also used as permanent magnets. These are used in Direct current machines to create magnetic flux, electrical instruments, moving coil loudspeaker etc.

Properties of Magnet
1. A magnet always attracts iron and its alloys
2. The magnet has two poles and when it is freely suspended it comes to rest pointing north and south directions. The end which points towards north is known as North-pole and the other which points toward south is known as South-Pole. The attracting power of the magnet is concentrated around two points one each at end ends.
3. Like poles repel and unlike poles attact each other.
4. If a magnet is broken into pieces, each pieces becomes and independent magnet.
5. A magnet can import its properties to any magnetic material.

Magnetic effect of electric current
When and electric current flows through a conductor, a magnetic field is set up all along the length of the conductor. In this connection following are the important points worth noting.
1. The magnetic lines of force are circular in a plane perpendicular to the current.
2. The field near the conductor is stronger and becomes weaker as we go away from the conductor.
3. The magnetic field becomes stronger if current is increased and vice-versa.
4. The direction of the field is reversed it current is reversed.

Facts of Magnetism and Electromagnetism
1. A magnet is a piece of iron or other magnetic material which can attract small pieces of thesematerial towards it.
2. A freely suspended magnet always rests in north south direction.
3. A natural magnet is called lodestone.
4. A magnet is able to attract nickel, cobalt and steel.
5. Externally, magnetic line of force travels north to south.
6. A material commonly used for shielding or screening magnetism is soft iron.
7. Magnetism is the property of certain materials of attracting small iron pieces toward them.
8. The magnetism that remains in a magnet after the magentising force has been removed is called its residual.
9. Iron becomes magnetized by induction when it is near to one end of a magnet.
10. Magnetic lines of force are called flux.

Current Interrupter Tutorials

Current Interrupter Tutorials Facts, Definitions, Uses Etc.

Circuit Breaker
An electromagnetic device that opens a circuit automatically when current exceeds a predermined value. It is capable of interrupting large values of fault power MVA resulting from the faults on the power system. It consists of current carrying contacts called electrodes which, under predetermined conditions, separate to interrupt the circuit. An arc is struck between them when the contacts are separated. This arc is extinquished either by lengthening the arc, cooling the arc, or splitting the arc. Due to this, the arc resistance increases resulting in the system voltage becoming unable to maintain the arc and the arc gets extinguised.

HRC Fuse
High Rupturing Capacity cartridge fuse is a good interrupting device because it gives a fast fault clearing and exhibits property of cut-off. It is useful in low and medium voltage installation to provide overload and short-circuit protection. The fuse element is of copper alloyed with tin. Its characteristics vary with the type of material and the shape of fuse element. The rated current of the fuse is the current which it can carry continously without deterioration.

Switchgear
The name given to a family of devices covering a wide range of equipment concerned with switching and interrupting the currents during normal and abnormal conditions. The equipment associated with controlling, protecting, regulating and measuring also belong to the switchgear family. It includes switches, fuses, Circuit breaker, isolator, relays, Control panel, metering panels lighting arresters, Current transformer, Potential transformer, and other associated items. The circuit breakers are assited by other components of the protective scheme. A switch is used for opening and closing the circuit. Fuse is used for over-current protection. The purpose of switching and protection is served by the swithgear. A circuit breaker is the switching and interrupting device in a switchegear.

Reactors
The purpose, of reactors incorporated in circuit breakers is to limit the short-circuit current flowing to a safe value thus providing protection of instruments. The concist of large coils of high self-inductance and very low resistance. Main type of reactors are magnetically shielded reactor, and the shielded reactor.

Answer all Frequent Questions About Circuit Breaker
1. The function of protective relay in a circuit breaker is to close the contacts when the actuating quantity reaches a certain predetermined value.
2. Low voltage circuit breakers have rated voltages of less than 1000 volts.
3. When A high voltage Alternating current circuit breaker is tested for endurance, it is tested for at least 1000 opening closing operations.
4. For high voltage Alternating Current circuit breaker, the rated short circuit current is passed for 3 three second.
5. Vacuum is not a type of the contactor for circuit breaker.

Current Interrupter Tutorials

Network Theorem Kirchoff's Law Tutorials

Kirchoff's Law Facts and tutorials

Kirchoff's Current Law (KCL) 
In any electrical network. The algebraic sum of the currents meeting at a point or junction is zero. Here it is assumed that incoming current to be positive and outgoing current to be negative.

Kirchoff's Voltage Law (KVL)
The algebraic sum of the products of currents and resistance in each of the conductors in any closed path or mesh in a network plus the algebraic sum of the electromotive force in the path is zero.

Sign Conventions for Kirchoff's Law

• A rise in voltage shall be given a plus sign and fall in voltage drop shall be given a negative voltage sign.
• In a resistance if we traverse in the direction of current. It is a voltage drop. This is because the current flows from higher potential to lower potential. This is voltage drop. It is given to be a negative voltage sign.
• In a resistance if we go in the direction, opposite to direction of flow of current, we are going from lower potential to higher potential. Going from lower to higher potential means voltage rise and shall be given a positive voltage sign.
• In a battery if we go from negative voltage sign terminal of battery to positive voltage sign this is voltage rise. This shall be given a positive voltage sign.
• In a battery if we go from positive voltage sign terminal of a battery to negative voltage sign terminal, this is voltage drop. It should be given a negative voltage sign.

Method to solve circuits by kirchoff's Law

• Draw a large clear diagram of the network to be solved showing the values of all resistors and the polarity and values of all sources of electromotive force letter the nodes and number of meshes.
• Arbitrarily choose direction for the currents in each branches. There is no point in wasting time for trying to indicate the true current directions since, in the majority of the cases, it is quite impossible to tell.
• Place plus and minus signs on each resistors to indicate the direction of the potential difference across it. These potential differences must be constant with the directions of the assumed branch currents.
• Write an equation for each in the network, using Kirchoff's second law, traversing the meshes in the clock wise direction.
• Solve the resulting simultaneous equations.

Take note that, it should be noted that Kirchoff's law are applicable both direct current and alternating current. Voltage and current, However in the case of alternating current and voltages any electromotive force or self-inductance that existing across a capacitor should also be taken into account.

Free pdf file for network Theorem
The fundamental laws that govern electric circuits are the Ohm’s Law and the Kirchoff’s
Laws.