JNTU B.Tech III SWITCH GEAR AND PROTECTION Previous Question Paper (March - 2024 - R16)

What is the most efficient torque-producing actuating structure for induction-type relay?

What is RRRV in circuit breakers?

Is the statement “The effect of an arc may cause the relay to underreach in distance relays” correct or wrong? Justify.

If the fault current is 2 kA, the relay setting is 50% and the CT ratio is 400/5, Calculate plug setting multiplier.

What type of relay is employed in protection scheme used for detection of loss of excitation of a very large generating unit feeding power into a grid?

Which relays has the capability of anticipating the possible major fault in a transformer?

What is meant by arcing grounds in power systems?

What are arcing grounds?

What is the time representation of standard Impulse Test Wave?

The Impulse ratios of insulators and lightning arresters should be high or low? Give reason.

What are the different types of circuit breaker when the arc quenching medium is the criterion? Mention the voltage range for which a particular types of circuit breaker are recommended.

In a 132 kV system, the reactance per phase up to the location of the circuit breaker is 5 Ω and capacitance to earth is 0.03 m F. Calculate (i) the maximum value of restriking voltage, (ii) the maximum value of RRRV, and (iii) the frequency of transient oscillation.

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

In a 132 kV system, reactance and capacitance up to the location of the circuit breaker is 5 Ω and 0.02 µF, respectively. A resistance of 500 Ω is connected across the breaker of the circuit breaker. Determine the (i) natural frequency of oscillation, (ii) damped frequency of oscillation, and (iii) critical value of resistance.

Explain stepped time-distance characteristics of three distance relaying units used for I, II and III zone of protection.

Explain why attracted armature type relays are noisy. What measures are taken to minimize the noise?

What are the merits of induction cup construction over the induction disc construction in relays?

In what way is distance protection superior to overcurrent protection for the protection of transmission lines?

What is Buchholz relay? Which equipment is protected by it? For what types of faults is it employed? Discuss its working principle.

A 5 MVA, 6.6 kV star connected generator has resistance per phase of 0.5 Ω and synchronous reactance per phase of 2 Ω. It is protected by a differential relay which operates when the out of balance current exceeds 30% of the load current. Determine what proportion of the generator winding is unprotected if the star point is grounded through a resistor of 6.5 Ω.

Draw and Explain the connection of CT secondaries for differential protection of star-delta connected power transformer.

An 11 kV, 100 MVA generator is provided with differential scheme of protection. The percentage of the generator winding to be protected against phase to ground fault is 80%. The relay is set to operate when there is 15% out of balance current. Determine the value of the resistance to be placed in the neutral to ground connection.

Explain the principal purposes of grounding.

A 132 kV, 50 Hz, 3-phase, 100 km long transmission line has a capacitance of 0.012 µF per km per phase. Determine the inductive reactance and kVA rating of the arc suppression coil suitable for the line to eliminate arcing ground phenomenon.

Explain in detail about Resistance grounding. What are the main features of resistance grounded systems?

A transmission line has a capacitance of 0.1 μF per phase. Determine the inductance of Peterson coil to neutralize the effect of capacitance of (i) complete length of line, (ii) 97% of the line, (iii) 90% length of the line. The supply frequency is 50 Hz.

Explain clearly how the rating of a lightning arrester is selected. What is the best location of a lightning arrester and why?

What is volt-time curves? What is their significance in power system studies?

With a neat diagram, explain operation of Valve type and Zinc-Oxide Lighting Arresters.

What are the External reasons of over voltage production in power systems?