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019 1 Pages:3

PART D

Answer any twofull questions, each carries 10 marks.
With the help of a neat diagram explain the working of Puffer type SF, circuit
breaker.
In a 220kV system, the reactance and capacitance up 10 the location of circuit
breaker is 8Q and 0.025uF respectively. A resistance of 600Q is connected
across the contacts of the circuit breaker. Determine the following.
a)Natural frequency of oscillation
b)Damped frequency of oscillation
c) Critical value of resistance which will give no transient oscillation.
With the help of neat diagram explain the working of a watt hour metre type
electromagnetic relay.
With the help of a neat diagram explain the working of percentage differential
protection used in transformer.
An 11kV, 10031۷۸ alternator is provided with differential protection. The
percentage of winding to be protected against phase to ground fault is 85%. The
relay is set to operate when there is 20% out of balance current. Determine the
value of the resistance to be placed in the neutral to ground connection.

With the help of a neat diagram explain the working of a surge diverter.

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