Power System Protection MCQs Part 14

Power System Protection MCQs Part 14

Arc in circuit breakers can be extinguished using which of following method

Arc in circuit breakers can be extinguished using which of following method:

1. High resistance method
2. Low resistance method
3. Both of these
4. None of these

Correct answer: 3. Both of these

Explanation:

• High resistance method: This method involves process during which arc resistance is made to increase with time so that current is reduced to a value insufficient to maintain the arc. As a result of this arc is interrupted.
• Low resistance: Low resistance method also sometimes referred as current zero method is the one during which arc resistance is kept low until current is zero where the arc extinguishes naturally and is prevented from restriking rather of the rising voltage across the contacts.  Low resistance method is valid of AC circuit breakers only

Earthing screen provides protection to substation against

Earthing screen provides protection to substation against:

1. Direct lightning strokes
2. Indirect lightning strokes
3. Both of these
4. None of these

Correct answer: 1. Direct lightning strokes

The making capacity of a circuit breaker is expressed mathematically as

The making capacity of a circuit breaker is expressed mathematically as

1. 2.55 x Symmetrical breaking capacity
2. √2 x Symmetrical breaking capacity
3. √3 x Symmetrical breaking capacity
4. √4 x Symmetrical breaking capacity

Correct answer: 1. 2.55 x symmetrical breaking capacity

Which of the following circuit breaker has highest noise produced when operated under fault conditions

Which of the following circuit breaker has highest noise produced when operated under fault conditions:

1. Air blast circuit breaker
2. Oil circuit breaker
3. Vaccum circuit breaker
4. SF6 circuit breaker

Correct answer: 1. Air blast circuit breaker

Breaking capacity of SF6 circuit breaker is not affected by

Breaking capacity of SF6 circuit breaker is not affected by:

1. Pollution
2. Atmospheric pressure
3. Weather and moisture
4. All of these

Correct answer: 4. All of these