Switchgear And Protection — Winter 2024

Define: 1) Pick up 2) Reach 3) Energizing quantities. .

Explain state different abnormalities occurred in power system.

Explain basic tripping circuit with appropriate diagram.

What is protective relay? Explain its function in an electrical system.

Classify the different types of relay.

Explain essential qualities of protective relaying.

Two relays R1 and R2 are connected in two sections of a feeder as shown in Fig. CTs are of ratio 200/1 A. The fault current is 2000A. The plug setting of relay R1 is 100% and R2 is 125%. The operating time characteristics of the relays is as given in Table The time multiplier setting of the relay R1 is 0.2. The time grading scheme has a discriminative time margin of 0.5s between the relays. Find the actual operating times of R1and R2.What is the time multiplier setting (TMS) of R2. PSM 2 3.6 5 8 10 Operating 10 6 3.9 3.15 2.8 2.1 time (sec)

Define PSM and TMS with reference to IDMT relay.

What is back up protection and why is it needed? Also explain different type of backup protection

What is the effect of fault resistance on the reach of various distance relays? Which relay is the most affected and which the least affected?.

Discuss zone of protection.

What factors cause spill current on external fault in case of transformer differential protection?

Draw R-Xdiagrams for the following distance relays. (i) Impedance relay (ii) Mho relay (iii) Reactance relay1

State different types of over current relays.

What are the drawbacks, if any, of over-current relays?

Describe simple differential protection of 3-phase delta-star type transformer.

Draw a neat sketch of an induction disc relay and discuss its operating principle.

Discuss the protection employed against loss of excitation of an alternator?

Describe in brief the different abnormalities and fault that occurs in three phase Induction motor.

What do you mean by ratio correction factor in CTs? Derive an expression for the same.

State advantages of Numerical relay.

Explain different arc quenching methods used in circuit breakers.

Explain CT burden. How is it specified?

Draw block diagram of numerical relay.

Discuss difference between Measuring CT and Protective CT in detail.