Mention any two applications of differential relay.

Mention any two applications of differential relay.
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Answer :

Protection of generator & generator transformer unit; protection of large motors and busbars .
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Related questions

Mention any 2 applications of differential relays.

Description : Mention any 2 applications of differential relays.

Last Answer : Protection of generator and generator-transformer unit: protection of large motors and bus bars

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Description : Mention some of the applications of Directional Over-Current relays?

Last Answer : 1. Double end fed power system 2. Single end fed system of parallel feeders 3. Ring main feeder system

Explain differential protection?

Description : Explain differential protection?

Last Answer : Differential protection is based on the fact that any fault within an electrical equipment would cause the current entering it, to be different, from that leaving it. Thus, we can compare the two ... phase or both and issue a trip output if the difference exceeds a pre- determined set value.

What are the problems in bus zone differential protection?

Description : What are the problems in bus zone differential protection?

Last Answer : Large number of circuits, different current levels for different circuits for external faults. Saturation of CT cores due to dc component and ac component in short circuit currents. The saturation ... the bus makes circuit complicated. Setting of relays need a change with large load changes.

What are the problems arising in differential protection in power transformer and how are they overcome?

Description : What are the problems arising in differential protection in power transformer and how are they overcome?

Last Answer : 1. Difference in lengths of pilot wires on either sides of the relay. This is overcome by connecting adjustable resistors to pilot wires to get equipotential points on the pilot wires. 2. ... harmonic restraining unit is added to the relay which will block it when the transformer is energized.

What is biased differential bus zone reduction?

Description : What is biased differential bus zone reduction?

Last Answer : The biased beam relay is designed to respond to the differential current in terms of its fractional relation to the current flowing through the protected zone. It is essentially an over-current ... coil. The restraining coil produces a bias force in the opposite direction to the operating force.

When voltage increases then current also increases then what is the need of over voltage relay and over current relay? Can we measure over voltage and over current by measuring current only?

Description : When voltage increases then current also increases then what is the need of over voltage relay and over current relay? Can we measure over voltage and over current by measuring current only?

Last Answer : No. We can't sense the over voltage by just measuring the current only because the current increases not only for over voltages but also for under voltage (As most of the loads are non-linear in ... So, for a better protection of the system. It should have both over voltage & over current relay.

What is reverse power relay?

Description : What is reverse power relay?

Last Answer : Reverse Power flow relay are used to stop the flow of power from grid to station generator when the generating units are off.

what is Buchholz relay and the significance of it in to the transformer?

Description : what is Buchholz relay and the significance of it in to the transformer?

Last Answer : Buchholz relay is a device which is used for the protection of transformer from its internal faults, it is a gas based relay. whenever any internal fault occurs in a transformer, the Buchholz ... circuit then it stop its sound itself otherwise it trips the circuit by its own tripping mechanism.

What are the advantages of static relay over electromagnetic relay?

Description : What are the advantages of static relay over electromagnetic relay?

Last Answer : o Low power consumption as low as 1mW o No moving contacts; hence associated problems of arcing, contact bounce, erosion, replacement of contacts o No gravity effect on operation of ... testing and servicing. Can convert even non-electrical quantities to electrical in conjunction with transducers.

What is a programmable relay?

Description : What is a programmable relay?

Last Answer : A static relay may have one or more programmable units such as microprocessors or microcomputers in its circuit.

What is static relay?

Description : What is static relay?

Last Answer : It is a relay in which measurement or comparison of electrical quantities is made in a static network which is designed to give an output signal when a threshold condition is passed which operates a tripping device.

What is REF relay?

Description : What is REF relay?

Last Answer : It is restricted earth fault relay. When the fault occurs very near to the neutral point of the transformer, the voltage available to drive the earth circuit is very small, which may not be ... of the transformer is restricted to cover only around 85%. Hence the relay is called REF relay.

What are the limitations of Buchholz relay?

Description : What are the limitations of Buchholz relay?

Last Answer : (a) Only fault below the oil level are detected. (b) Mercury switch setting should be very accurate, otherwise even for vibration, there can be a false operation. (c) The relay is of slow operating type, which is unsatisfactory.

What are the types of graded used in line of radial relay feeder?

Description : What are the types of graded used in line of radial relay feeder?

Last Answer : Definite time relay and inverse-definite time relay.

What are the uses of Buchholz’s relay?

Description : What are the uses of Buchholz’s relay?

Last Answer : Bucholz relay is used to give an alarm in case of incipient( slow-developing) faults in the transformer and to connect the transformer from the supply in the event of severe internal faults. It is usually used in oil immersion transformers with a rating over 750KVA.

What are the features of directional relay?

Description : What are the features of directional relay?

Last Answer : High speed operation; high sensitivity; ability to operate at low voltages; adequate short-time thermal ratio; burden must not be excessive.

What is an under frequency relay?

Description : What is an under frequency relay?

Last Answer : An under frequency relay is one which operates when the frequency of the system (usually an alternator or transformer) falls below a certain value.

What is the need of relay coordination?

Description : What is the need of relay coordination?

Last Answer : The operation of a relay should be fast and selective, ie, it should isolate the fault in the shortest possible time causing minimum disturbance to the system. Also, if a relay fails to ... relays, faults can always be isolated quickly without serious disturbance to the rest of the system.

Define resetting time of a relay.

Description : Define resetting time of a relay.

Last Answer : It is defined as the time taken by the relay from the instant of isolating the fault to the moment when the fault is removed and the relay can be reset.

Define operating time of a relay.

Description : Define operating time of a relay.

Last Answer : It is defined as the time period extending from the occurrence of the fault through the relay detecting the fault to the operation of the relay.

Mention any two disadvantage of carrier current scheme for transmission line only.

Description : Mention any two disadvantage of carrier current scheme for transmission line only.

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Mention the inductance value of the peterson’s coil.

Description : Mention the inductance value of the peterson’s coil.

Last Answer : L=1/3wc2

Mention the withstanding current in our human body.

Description : Mention the withstanding current in our human body.

Last Answer : 9mA

Mention the advantages of field tests.

Description : Mention the advantages of field tests.

Last Answer : The circuit breaker is tested under actual conditions like those that occur in the network. Special occasions like breaking of charging currents of long lines ,very short line faults ,interruption of small inductive currents etc… can be tested by direct testing only.

Mention the various tests carried out in a circuit breaker at HV labs.

Description : Mention the various tests carried out in a circuit breaker at HV labs.

Last Answer : Short circuit tests, Synthetic tests& direct tests.

Mention the short comings of Merz Price scheme of protection applied to a power transformer.

Description : Mention the short comings of Merz Price scheme of protection applied to a power transformer.

Last Answer : In a power transformer, currents in the primary and secondary are to be compared. As these two currents are usually different, the use of identical transformers will give differential current, and ... turn-ratio are used, the differential current may flow through the relay under normal condition.

In three pin plug why earth pin diameter is higher than other two pin?

Description : In three pin plug why earth pin diameter is higher than other two pin?

Last Answer : Because Current flow in the conductor is inversely proportional to the conductor diameter. So if any short circuits occur in the system first high currents bypassed in the Earthling terminal. (R=Pl/a area of the conductor increases resistance value decreases)

Give the two methods of arc interruption?

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What is the difference between surge arrestor and lightning arrestor?

Description : What is the difference between surge arrestor and lightning arrestor?

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Where are the lighting arrestors placed in distribution lines?

Description : Where are the lighting arrestors placed in distribution lines?

Last Answer : Near distribution transformers and outgoing feeders of 11kv and incoming feeder of 33kv and near power transformers in sub-stations.

What is meant by knee point voltage?

Description : What is meant by knee point voltage?

Last Answer : Knee point voltage is the voltage at which a CT gets saturated. It is one of the important factors taken into consideration for selecting a current transformer.

What is different between resistance grounding system and resistance earthing system?

Description : What is different between resistance grounding system and resistance earthing system?

Last Answer : In resistance grounding system the neutral point of the load is connected to the ground to carry the residual current in case of unbalanced conditions. Resistance earthing system is done in an electric equipment in order to protect the equipment in occurrence of fault in the system.

What is the difference between megger test equipment and contact resistance meter test instruments?

Description : What is the difference between megger test equipment and contact resistance meter test instruments?

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What is inrush current?

Description : What is inrush current?

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What are the different types of faults in a transformer?

Description : What are the different types of faults in a transformer?

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What is dielectric test of a circuit breaker?

Description : What is dielectric test of a circuit breaker?

Last Answer : It consists of overvoltage withstand test of power frequency lightning and impulse voltages.Testa are done for both internal and external insulation with switch in both open and closed conditions.

How direct tests are conducted in circuit breakers?

Description : How direct tests are conducted in circuit breakers?

Last Answer : Using a short circuit generator as the source. Using the power utility system or network as the source.

Differentiate between a fuse and a circuit breaker.

Description : Differentiate between a fuse and a circuit breaker.

Last Answer : Fuse is a low current interrupting device. It is a copper or an aluminium wire. Circuit breaker is a high current interrupting device and it act as a switch under normal operating conditions.

Define single line diagram.

Description : Define single line diagram.

Last Answer : Representation of various power system components in a single line is defined as single line diagram.

State the different types of circuit breakers.

Description : State the different types of circuit breakers.

Last Answer : Air ,oil,vacuum circuit breakers.

State the various types of unsymmetrical faults.

Description : State the various types of unsymmetrical faults.

Last Answer : Line to ground ,line to line and double line to ground faults

State the different types of faults.

Description : State the different types of faults.

Last Answer : Symmetrical faults and unsymmetrical faults and open conductor faults.

Define negative sequence component.

Description : Define negative sequence component.

Last Answer : It has 3 vectors equal in magnitude and displaced from each other by an angle 120 degrees and has the phase sequence in opposite to its original phasors.

State the significance of double line fault.

Description : State the significance of double line fault.

Last Answer : It has no zero sequence component and the positive and negative sequence networks are connected in parallel.

Define zero sequence component.

Description : Define zero sequence component.

Last Answer : They has 3 vectors having equal magnitudes and displaced from each other by an angle zero degrees.

Define positive sequence component.

Description : Define positive sequence component.

Last Answer : -has 3 vectors equal in magnitude and displaced from each other by an angle 120 degrees and having the phase sequence as original vectors.

State the three sequence components.

Description : State the three sequence components.

Last Answer : Positive sequence components, negative sequence components and zero sequence components.

What are symmetrical components?

Description : What are symmetrical components?

Last Answer : It is a mathematical tool to resolve unbalanced components into balanced components.

State the significance of single line to ground fault.

Description : State the significance of single line to ground fault.

Last Answer : In single line to ground fault all the sequence networks are connected in series. All the sequence currents are equal and the fault current magnitude is three times its sequence currents.