What are the advantages of MOCB over a bulk oil circuit breaker?

What are the advantages of MOCB over a bulk oil circuit breaker?
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1 Answer

Answer :

• It requires lesser quantity of oil
• It requires smaller space
• There is a reduced risk of fire
• Maintenance problem are reduced
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Related questions

What are the disadvantages of MOCB over a bulk oil circuit breaker?

Description : What are the disadvantages of MOCB over a bulk oil circuit breaker?

Last Answer : o The degree of carbonization is increased due to smaller quantity of oil o There is difficulty of removing the gases from the contact space in time o The dielectric strength of the oil deteriorates rapidly due to high degree of carbonization.

What are the advantages of air blast circuit breaker over oil circuit breaker?

Description : What are the advantages of air blast circuit breaker over oil circuit breaker?

Last Answer : o The risk of fire is diminished o The arcing time is very small due to rapid buildup of dielectric strength between contacts o The arcing products are completely removed by the blast whereas oil deteriorates with successive operations

What are demerits of MOCB?

Description : What are demerits of MOCB?

Last Answer : Short contact life Frequent maintenance Possibility of explosion Larger arcing time for small currents Prone to restricts

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.

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 composite testing of a circuit breaker.

Description : Define composite testing of a circuit breaker.

Last Answer : In this method the breaker is first tested for its rated breaking capacity at a reduced voltage and afterwards for rated voltage at a low current.This method does not give a proper estimate of the breaker performance.

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.

What are the indirect methods of circuit breaker testing?

Description : What are the indirect methods of circuit breaker testing?

Last Answer : o Unit test o Synthetic test o Substitution testing o Compensation testing o Capacitance testing

What are the types of air blast circuit breaker?

Description : What are the types of air blast circuit breaker?

Last Answer : Arial-blast type Cross blast Radial-blast

What is the main problem of the circuit breaker?

Description : What is the main problem of the circuit breaker?

Last Answer : When the contacts of the breaker are separated, an arc is struck between them. This arc delays the current interruption process and also generates enormous heat which may cause damage to the system or to the breaker itself. This is the main problem.

What is circuit breaker?

Description : What is circuit breaker?

Last Answer : It is a piece of equipment used to break a circuit automatically under fault conditions. It breaks a circuit either manually or by remote control under normal conditions and under fault conditions.

The Minimum Oil Circuit Breaker (MOCB) is named because of :

Description : The Minimum Oil Circuit Breaker (MOCB) is named because of :  (A) Reduced requirement of oil (B) Reduced requirement of air (C) All of the above (D) None of the above

Last Answer : The Minimum Oil Circuit Breaker (MOCB) is named because of : Reduced requirement of oil 

What are the advantages of oil as arc quenching medium?

Description : What are the advantages of oil as arc quenching medium?

Last Answer : • It absorbs the arc energy to decompose the oil into gases, which have excellent cooling properties • It acts as an insulator and permits smaller clearance between line conductors and earthed components

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.

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.

What are the advantages of synthetic testing methods?

Description : What are the advantages of synthetic testing methods?

Last Answer : The breaker can be tested for desired transient recovery voltage and RRRV. Both test current and test voltage can be independently varied. This gives flexibility to the test The method is simple With ... capacity (MVA) of five time of that of the capacity of the test plant can be tested.

What are the demerits of using oil as an arc quenching medium?

Description : What are the demerits of using oil as an arc quenching medium?

Last Answer : • The air has relatively inferior arc quenching properties • The air blast circuit breakers are very sensitive to variations in the rate of rise of restriking voltage • Maintenance is required for the compression plant which supplies the air blast

What are the hazards imposed by oil when it is used as an arc quenching medium?

Description : What are the hazards imposed by oil when it is used as an arc quenching medium?

Last Answer : There is a risk of fire since it is inflammable. It may form an explosive mixture with arc. So oil is preferred as an arc quenching medium.

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.

State the different types of circuit breakers.

Description : State the different types of circuit breakers.

Last Answer : Air ,oil,vacuum circuit breakers.

Write the classifications of test conducted on circuit breakers.

Description : Write the classifications of test conducted on circuit breakers.

Last Answer : Type test Routine test Reliability test Commissioning test

Write the classification of circuit breakers based on the medium used for arc extinction?

Description : Write the classification of circuit breakers based on the medium used for arc extinction?

Last Answer : Air break circuit breaker Oil circuit breaker Minimum oil circuit breaker Air blast circuit breaker SF6 circuit breaker Vacuum circuit breaker

Give the consequences of short circuit.

Description : Give the consequences of short circuit.

Last Answer : Whenever a short-circuit occurs, the current flowing through the coil increases to an enormous value. If protective relays are present, a heavy current also flows through the relay coil, causing it to ... system. Also, a low voltage may be created which may damage systems connected to the supply.

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.

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

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

How does the over voltage surge affect the power system?

Description : How does the over voltage surge affect the power system?

Last Answer : The over voltage of the power system leads to insulation breakdown of the equipments. It causes the line insulation to flash over and may also damage the nearby transformer, generators and the other equipment connected to the line.

What is over fluxing protection in transformer?

Description : What is over fluxing protection in transformer?

Last Answer : If the turns ratio of the transformer is more than 1:1, there will be higher core loss and the capability of the transformer to withstand this is limited to a few minutes only. This phenomenon is called over fluxing.

What are the causes of over speed and how alternators are protected from it?

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Last Answer : Sudden loss of all or major part of the load causes over-speeding in alternators. Modern alternators are provided with mechanical centrifugal devices mounted on their driving shafts to trip the main valve of the prime mover when a dangerous over-speed occurs.

What are over and under current relays?

Description : What are over and under current relays?

Last Answer : Overcurrent relays are those that operate when the current in a line exceeds a predetermined value. (eg: Induction type non-directional/directional overcurrent relay, differential overcurrent relay)whereas ... in a circuit/line drops below a predetermined value.(eg: differential over-voltage relay)

Name the different kinds of over current relays.

Description : Name the different kinds of over current relays.

Last Answer : Induction type non-directional over current relay, Induction type directional over current relay & current differential relay.

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)

What is the difference between surge arrestor and lightning arrestor?

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

Last Answer : Lightning arrestor is installed outside and the effect of lightning is grounded, whereas surge arrestor installed inside panels comprising of resistors which consumes the energy and nullify the effect of surge.

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 reverse power relay?

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What is meant by knee point voltage?

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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?

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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?

Last Answer : Megger test equipment used to measure cable electric resistance, conductor continuity, phase identification. Contact resistance meter test instruments used to measure low resistance like relays, contactors.

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?

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What is inrush current?

Description : What is inrush current?

Last Answer : the initial value of flux is zero when the transformer is energized. The, the flux reaches a peak value in half a cycle. Since power transformers operate near the knee of the saturation curve, a flux ... the order of 8 to 30 times the full-load current. This current is known as inrush current.

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

Last Answer : The internal faults include phase faults, ground faults, inter-turn faults, tap-changer failure, and leakage oil from tank. The external faults include system phase faults, system ground faults, over loads and over fluxing.

Explain differential protection?

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Define single line diagram.

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

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

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.