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Alternating Current and Direct Current

A three phase...

Question

A three phase, 33 kV oil circuit breaker is rated at 1 kA, 400 MVA, 3s. The value of symmetrical breaking current will be

A

1 kA

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B

1440 A

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C

6998.18 A

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D

1.732 kA

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Solution

The correct option is C 6998.18 A
Rated MVA of circuit breaker = 400 MVA
$\sqrt{3} \times {| V_{l i n e} |}_{r a t e d}$ × symmetrical breaking current = rated MVA of C.B.

$∴$ symmetrical breaking current $= \frac{400}{\sqrt{3} \times 33}$ = 6.99818 kA = 6998.18 A

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