Switchgear And Protection — Summer 2025

Explain the terms Sensitivity and selectivity with respect to their use in the protective relaying field.

Explain Plug setting and time setting of Over current relay.

Discuss the working principle of an induction disc relay. Also derive an expression for the torque produced by it.

What are the drawbacks of a simple differential scheme?

Explain reverse power relay.

What do you mean by Earth Leakage Protection? Explain Earth leakage protection for single phase load.

Why are over current relays not used for primary protection of EHV lines?

Explain principle of simple Impedance relay. Also draw characteristic.

Explain the need of a three steps distance protection of a transmission line.

With schematic, explain protection from phase fault and ground fault inside the three phase induction motor.

Explain the inrush phenomenon in transformers.

What are incipient faults? Discuss in detail the type of protection provided in transformer to cater to such type of faults

Explain rotor earth fault protection for the generator with a diagram.

What are the effect of single phasing on the Induction Motor?

In relation to circuit breaker arc interruption, explain the recovery rate theory and energy balance theory.

Explain the basic schematic of differential protection of bus-bars. Explain its behavior with reference to internal and external faults.

Explain the concept of adaptive relaying.

Explain Making capacity & Breaking Capacity of Circuit Breakers.

What is meant by loss of excitation in a generator? What protection is used against it?

Why is SF6 a nearly ideal medium for arc interruption?

Discuss the difference between the measuring CT and protecting CT.

Draw and explain the general block diagram of numerical relay

Compare Reactance relay & MHO relay.

Explain the principle of percentage biased differential protection with harmonic restraint.

Explain construction and working of Minimum Oil Circuit Breaker (MOCB).