# Power System MCQs Part 8

Power System MCQs Part 8

## Effect of increasing gating angle in a thyristorised controlled reactor is to

Effect of increasing gating angle in a thyristorised controlled reactor is to:

1. Decrease power loss in thyristor controller
2. Decrease power loss in the reactor
3. Make current wave form less sinusoidal
4. All of these

Correct answer: 4. All of these

## SSR phenomenon is

SSR phenomenon is

1. Purely electrical
2. Purely mechanical
3. Purely hydraulic
4. Both electrical and mechanical

Correct answer: 4. Both electrical and mechanical

Explanation: SSR phenomenon or Subsynchronous resonance phenomenon is the one that involves the process of one or more of the resonant frequencies of the turbine generator shaft in thermal power units coincidence through the generator with natural resonant frequency of the electrical system with long radial transmission network with series capacitors in such a manner that there is a sustained, cyclic exchange of energy between the mechanical shaft and the electrical system.

SSR occurs whenever the natural frequency of mechanical Oscillation of the shaft of the rotor equals the difference of electrical frequency (f – f0), mechanical resonance would take place. So SSR therefore is combined electrical mechanical resonance phenomenon.

## An RLC series circuit remains predominantly inductive

An RLC series circuit remains predominantly inductive:

1. Below resonance frequency
2. Above resonance frequency
3. At resonance frequency
4. At the lower half power frequency

Correct answer: 2. Above resonance frequency

## The inertia constant H of a synchronous condenser is

The inertia constant H of a synchronous condenser is

1. Greater than that of hydro generator
2. Greater than that of turbo alternator
3. Equal to that of turbo alternator
4. None of these

Correct answer: 4. None of these

## The magnetizing-inrush-current in a transformer is rich in

The magnetizing-inrush-current in a transformer is rich in

1. 2nd harmonics
2. 3rd harmonics
3. 5th harmonics
4. 7th harmonics