1 Answer

Protection by fuses is generally not used beyond 100 A .

Like 0 like Dislike 0 dislike

Related questions

Answer : The delay fuses are used for the protection of motors.

Answer : H.R.C. fuses provide best protection against short-circuits.

Description : The material used in liquid fuses is  (1) SF6 (3) carbon tetra chloride (2) distilled water (4) transformer oil

Answer : The material used in liquid fuses is  carbon tetra chloride

Description : A relay used for protection of motors against overload is :  (A) Impedance relay (B) Electromagnetic attraction type (C) Thermal relay (D) Buchholz's relay

Answer : A relay used for protection of motors against overload is : Thermal relay

Description : A negative sequence relay is used for protection of  (1) Generator (3) Motor (2) Transformer (4) Long Transmission lines

Answer : A negative sequence relay is used for protection of Generator 

Description : For protection of rotating machines against lightning surges _______ is used.  (1) lightning arrester (2) capacitor (3) combination of lightning arrester and capacitor (4) lightning conductor and arrester

Answer : For protection of rotating machines against lightning surges combination of lightning arrester and capacitor is used. 

Description : Surge absorbers are used for protection against

Answer : Surge absorbers are used for protection against low voltage high frequency oscillations

Answer : The inverse definite mean time relays are used for over current and earth fault protection of transformer against internal short-circuits.

Answer : The single phasing relays are used for the protection of three phase motors.

Answer : Discrimination between main and back up protection is provided by the use of relays which are slow.

Description : Blind spot is a point in the zones of protection where

Answer : Blind spot is a point in the zones of protection where No protection is available.

Description : Reactance relay is normally preferred for protection against

Answer : Reactance relay is normally preferred for protection against earth faults

Answer : A fuse in a motor circuit provides protection against short-circuit and overload.

Answer : Overfluxing protection is recommended for generator transformer of the power plant.

Answer : Over voltage protection is recommended for hydro-electric generators, steam turbine generators, gas turbine generators.

Answer : For the protection of power station buildings against direct strokes the requirements are interception, conduction and dissipation.

Answer : A thermal protection switch can protect against overload.

Description : Primary and Backup Protection

Answer : Primary and Backup Protection  B,D,G,I are the primary protection. A,C,H,J are the backup protection. About 90% of faults are clear by Primary Protection. So ... ordinated backup (primary is at various station  and backup is at control room with computer)

Description : Explain in detail over-voltage protection.

Answer : Over-voltage protection: Over-voltage protection to the thyristor is provided using: i) R-C Snubber circuit ii) Non-linear resistor Thyrector A) Snubber Circuit: It is basically a ... returns to its high resistance state. Thyrector is normally placed across the supply terminals.

Description : Fuse wire protection system is usually not used beyond: a. 10A b. 25A c. 50A d. 100A  

Answer : Fuse wire protection system is usually not used beyond: a. 10A b. 25A c. 50A d. 100A  

Description : Explain the “Differential Protection Scheme” used for alternators with neat labeled diagram.

Answer : Differential Protection Scheme for Alternator: Figure shows the differential protection provided to 3 phase alternator. Here identical CTs are placed on both sides of 3 phase alternator and ... causing its operation. Relay sends trip signal to the CB, thereby alternator circuit is tripped.

Description :  For the protection of parallel feeders fed from one end, the relays used are: A) non-directional relays at the source-end and directional relays at the load-end B) non-directional relays at both the ... at the source-end and non-directional at the load-end D) directional relays at both the ends

Answer : For the protection of parallel feeders fed from one end, the relays used are: non-directional relays at the source-end and directional relays at the load-end

Description : The type of backup protection scheme widely used in the field is (A) Relay backup (B) Breaker backup (C) Remote backup (D) Auxiliary backup

Answer : The type of backup protection scheme widely used in the field is Remote backup 

Description : Protection of transformer from all types of faults is by using (A) over current relay (B) differential relay (C) distance relay (D) Buchholz relay

Description : Departmentation by time is one of the oldest forms of departmentation, generally used at lower levels of the organization. Which of the following is not an advantage of departmentation ... results in improved coordination and communication (d) It results in a continuous cycle without interruption

Answer : (c) It mostly results in improved coordination and communication  

Description : Kick fuses are used across relay coils to prevent relay operation during   (a) Heavy external faults (b) Inrush current of transformer when they are energised (c) Line to ground faults (d) Bolted faults  

Description : Explain with neat sketch, the Pilot wire protection scheme applied to transmission line.

Answer : Pilot Wire Protection scheme of Transmission Line : Figure shows the single line diagram of Merz price voltage balance system for pilot wire protection of three phase transmission line. ... through the relay, which gives trip signal to the circuit breaker for protection of transmission line.

Description : Explain differential protection scheme for busbars with neat sketch.

Answer : Differential Protection Scheme for Bus bar:  Under normal conditions, the sum of the currents entering the bus bar zone is equal to those leaving it and no current flows through the relay ... of these currents will flow through the relay coil causing opening of circuit breaker of bus-bar.

Description : Discuss in brief the principle of distance protection and state four advantages of distance protection scheme.

Answer : Advantages: 1. System is economical 2. High speed of interruption 3. Suitable for very long and high voltage transmission lines. 4. No problem of pilot wires.

Description : State two requirements of transmission line protection. 

Answer : Requirements of Transmission Line Protection: 1) Faults on lines should be quickly detected to initiate actions to maintain system stability. 2) For very long lines the protection system must be capable ... backup protection in the event of failure of circuit breaker (nearest to fault) to operate.

Description : List two limitations of Differential-Protection scheme for transformer.

Answer : Limitations of Differential Protection Scheme of Transformer:  1) Due to the magnetization characteristics of the CTs used, the ratio errors change with respect to the circulating currents.  2) ... & improper operation.  5) Inrush of magnetizing current may lead to inadvertent operation.

Description : Explain differential protection of busbar.

Answer : Differential protection Scheme for bus bar: Under normal conditions the sum of the currents entering the bus bar zone is equal to those leaving it and no current flows through the relay ... . The difference of these currents will flow through the relay coil causing opening of circuit breaker.

Description : Explain over-current protection of transformer.

Answer : Over-Current Protection of Transformer: Simple over-current & earth fault protection of transformer against external shortcircuit and excessive overloads is shown in the above figure. The ... trip command to the circuit breaker and the transformer is disconnected from load or fault.

Description : Explain negative phase sequence protection of alternator.

Answer : Negative phase sequence protection of alternator: Unbalanced loading on alternator mainly causes the negative sequence currents which generate the negative sequence components of magnetic fields. These fields ... components due to unbalance and operates the relay which further operates CB.

Description : Explain fault bus protection scheme.

Answer : Fault bus protection of busbar: In this scheme, the substation is so designed that every fault on the bus bar is converted to earth fault. Under normal operating conditions, there is no current flowing ... This results in operation of relay to actuate trip coil of CB to trip the circuit.

Description : Explain distance protection of transmission line with neat sketch diagram.

Answer : Distance protection of Transmission line: Distance protection scheme uses impedance relay. The relay operation is based on the impedance (or distance) between the relay and point of fault. Figure shows ... than ZL and impedance relay operates which operates the CB and line is protected.

Description : Write down limitation of differential protection of transformer.

Answer : Limitations of differential protection of transformer: 1) Due to the magnetization characteristics of the CTs used, the ratio errors change with respect to the circulating currents. 2) The pilot wires ... current (higher imbalance) due to which accuracy of sensing & operation is decreased. 

Description : How can we use CT and PT for protection purpose?

Answer : CT and PT for Protection purpose: Current transformer (CT) and Potential transformer (PT) are instrument transformers, which are used in conjunction with protective relays for protection purpose. The CT ... from the healthy part. In this way the CT and PT can be used for protection purpose.

Description : For complete protection of a three-phase line: A) three Phase relays and three Earth fault relays are required B) three Phase relays and two Earth fault relays are required C) two Phase relays and two Earth fault relays are required D) two Phase relays and one Earth fault relay are required

Answer : For complete protection of a three-phase line: two Phase relays and one Earth fault relay are required

Description : Which type of protection is provided on a generator to protect against stator insulation failure? A) Differential protection B) Overcurrent relay C) Thermocouple actuated alarm D) Reverse power relay

Answer : Which type of protection is provided on a generator to protect against stator insulation failure? A) Differential protection B) Overcurrent relay C) Thermocouple actuated alarm D) Reverse power relay 

Description : A loss of excitation protection scheme for large generating unit employs A) under frequency relays B) offset Mho relay C) reactance relay D) percentage differential relay

Answer : A loss of excitation protection scheme for large generating unit employs offset Mho relay

Description : For complete protection ofa 3— phase line: (1) Three phase and three—earth fault relays are required (2) Three phase and two—earth fault relays are required (3) Two phase and two—earth fault relays are required (4) Two phase and one-earth fault relays are required

Answer : For complete protection ofa 3— phase line: Two phase and one-earth fault relays are required

Description : In order to quench the are quickly and also optimize the dimensions generally   (a) Air blast C.B. is preferred (b) Oil C.B. is preferred (c) SF6 C.B. is preferred (d) Minimum oil C.B. is preferred  

Answer : In order to quench the are quickly and also optimize the dimensions generally SF6 C.B. is preferred

Description : The modern consensus regarding the sending of disciplinary cases to the principal's office is that Options: A) It should be used only when other means have failed B) It is generally ... D) It is generally advisable since the principal is ultimately responsible for the discipline in his school

Answer : A) It should be used only when other means have failed 

Description : Leadership is not magnetic personality--that can just as well be a glib tongue. It is not "making friends and influencing people"--that is flattery. Leadership is lifting a person's vision to ... to a higher standard, the building of a personality beyond its normal limitations. - Peter Drucker quote

Description : "Unless you are willing to drench yourself in your work beyond the capacity of the average man, you are just not cut out for positions at the top." - J.C. Penny

Description : As a teacher you should not demand your pupils which is beyond their stage of growth. If you do so, it only causes Options: A) Frustrations B) Frustrations, Heighten Tension And Nervousness C) Encouragement For More Learning D) Both (B)And (C 

Answer : B) Frustrations, Heighten Tension And Nervousness 

Description : Suppose you are an ambitious teacher. You have high ideals for classroom teaching but your hard-labour goes in vain. The reason is that the student's result is not satisfactory. The reason of this ... own level C) Individual differences among the students D) The teaching has no access to students

Answer : Individual differences among the students

Description : In plant studies, many species of angiosperms lack secondary growth and therefore do not become woody. They are generally called by which of the following? a) trees b) bines c) herbs d) none of the above

Answer : ANSWER: C -- HERBS

Description : Attitude, once established Options: A) Generally continue to exist even if they do not provides satisfaction for one's motives B) Can be changed relatively easily by introducing ... effectively by intellectual appeal than by emotional appeal D) Are often maintained through selective perception

Answer : D) Are often maintained through selective perception

← Prev Question Next Question →
Ask a Question
Choose topic