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long time delay primary injection testing

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  1. KLLU26 is offline Junior Member
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    long time delay primary injection testing

    i've been testing for about 4 months now and one question i seem to keep asking (and haven't gotten a definitive answer) pertains to the recorded times of the long time delay during primary injection testing of a molded case square d circuit breaker.

    while testing A phase, at X current we would record roughly 60 seconds.

    B phase would drop to around 35-40 seconds,

    C phase would be similar.

    now i am familiar with the fact that as the breaker heats up the trip time will decrease, so my question is about the value that we record. in my mind under a normal load the breaker will be warmer, obviously, so during an overload the breaker would most likely trip around the 35-40 second mark. so why would we record and expect our values to be around 60 seconds from a cold test? i think it would be more accurate to record and expect the 35-40 second reading in a real world situation.

    is this just part of the manufacturers specification or NETA standards?

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