1 Answer

Answer :

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

Related questions

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

Description : IDMT relays are used to protect the transformer against :  (A) Internal short -circuits (B) Open circuits (C) External short circuits (D) Oil leakage

Last Answer : IDMT relays are used to protect the transformer against : External short circuits

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

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

Last Answer : The relay with inverse time characteristic will operate within 5 to 10 sec.

Description : To protect the power transformer (Y-Y with neutral grounded) against fault, what type of connection do the CTs have ?

Last Answer : To protect the power transformer (Y-Y with neutral grounded) against fault, what type of connection do the CTs have ? Δ-Δ connection

Last Answer : Impedance relays are used for phase faults on long line.

Description : If the fault current is 6000 A, the relay plug setting is 150% and the CT ratio is 400/5, the plug setting multiplier will be

Last Answer : If the fault current is 6000 A, the relay plug setting is 150% and the CT ratio is 400/5, the plug setting multiplier will be 10

Description : If the % reactance upto the fault point is 20%, then the short circuit current will be

Last Answer : If the % reactance upto the fault point is 20%, then the short circuit current will be 5 times the full load current

Description : In which fault the maximum short circuit current occurs?

Last Answer : In three phase bolted fault the maximum short circuit occurs.

Description : With fault clearing time, the transient stability of a power system

Last Answer : With fault clearing time, the transient stability of a power system decreases

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

Last Answer : D

Description : Surge absorbers are used for protection against

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

Description : The inverse definite mean time relays are used for over current and earth fault protection of transformer against (a) heavy loads (b) internal short-circuits (c) external short-circuits (d) all of the above

Last Answer : (b) internal short-circuits

Description : In the induction type directional over current relay, when a short-circuit occurs in the circuit (A) power flows in reverse direction (B) power flows in normal direction (C) directional power element does not operate (D) over current element is not energized

Last Answer : In the induction type directional over current relay, when a short-circuit occurs in the circuit power flows in reverse direction

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

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

Description : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be

Last Answer : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be 10 A

Description : Which of the following is the least expensive protection for over current in low voltage system?  (A) Rewireable fuse (B) Isolator (C) Oil Circuit breaker (D) Air break circuit breaker

Last Answer : Which of the following is the least expensive protection for over current in low voltage system?  (A) Rewireable fuse (B) Isolator (C) Oil Circuit breaker (D) Air break circuit breaker

Last Answer : Thermal overload relays are used to protect the motor against overcurrent due to heavy loads.

Description : Select insulating materials for following parts : (i) Insulation between heating element and base plate of electric iron. (ii) Insulation used over copper or aluminium conductor used for making coils. (iii) Transformer bushings. (iv) Insulation between transmission line and pole.

Last Answer : Parts Insulating Materials  Insulation between heating element and base plate of electric iron. Mica Insulation used over copper or aluminium conductor used for making coils.  ... Transformer bushings Porcelain  Insulation between transmission line and pole. Porcelain

Description : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then  (A) zero sequence currents are present on both sides of the transformer  (B) ... side  (D) zero sequence currents are present on the primary side but not on the secondary side

Last Answer : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then zero sequence currents are absent on both sides of the transformer 

Last Answer : To protect most of the electrical equipment handling low power, the types of relays used are thermocouple, electronic and bimetallic.

Last Answer : Protective relays are devices that detect abnormal conditions in electrical circuits by measuring constantly the electrical quantities which differ during normal and abnormal conditions.

Last Answer : Directional relays are based on flow of power.

Description : D.C. shunt relays are made of?

Last Answer : D.C. shunt relays are made of many turns of thin wire.

Last Answer : Overload relays are of induction, solid state, thermal, electromagnetic type.

Last Answer : Relays can be designed to respond to changes in resistance, reactance or impedance voltage and current, light intensity, temperature.

Description : The operating point of a protective current transformer is near the

Last Answer : The operating point of a protective current transformer is near the Ankle point

Description : The inrush current of a transformer at no load is maximum if the supply voltage is switched on  (1) at peak voltage value (2) at zero voltage value (3) at half voltage value (4) at 0.866 time voltage value

Last Answer : At 0.866 time voltage value

Description : 3 phase 11KV to 4 10000 KVA alternator has neutral Earth through a resistance of 1 ohm the machine has current balance protection while operate upon of balance Karan exceed 18% of full load determine percentage of winding and protected against ground fault

Last Answer : Reactance relay is preferred for phase fault on short transmission line.

Last Answer : Fault diverters are basically fast switches.

Description : Which is the most common type of fault?

Last Answer : Single phase to ground fault is the most common type of fault.

Description : ln HRC fuse the time between cut-off and final current zero is called

Last Answer : ln HRC fuse the time between cut-off and final current zero is called the arcing time

Description : 3X3 inverse of matrix short trick

Last Answer : 3X3 inverse of matrix short trick

Description : For a given matrix inverse of a matrix is

Description : What is the inverse of reactance?

Last Answer : Inverse of reactance is Susceptance .Unit of Susceptance is Siemens.

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

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

Description : Reactance relay is normally preferred for protection against

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

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