Question: Give the analytical reason for justifying the use of rated voltage in MVA breaking capacity ratings of the circuit breaker?
Answer: The MVA breaking capacity of the circuit breaker is the product of short-circuit current (A) and normal rated service voltage. At a glance, one might think the use of rated voltage rating is unjustified.
During a short circuit, the voltage across breaker contacts is very small, furthermore, the voltage is absorbed by the distributed impedance due to which potential can’t be measured during the fault.
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