Ground Fault

Discussion in 'General Electronics Chat' started by Jsw123, Dec 27, 2009.

  1. Jsw123

    Thread Starter Active Member

    Jun 20, 2009
    I am using a ground fault sensor in conjunction with a controller to protect from stator ground fault on a generator. I have come across several that say they are rated at 10, 20 and so on amps. (the system shuts down only when stator ground fault occurs.)

    What I am wondering is what would happen when the current is overloaded beyond what the CT switch is rated at. If you look at the diagram it will show that very high currents can flow while in many other ground fault applications, it is only small fault currents that will flow. Will the saturation cause a regular ground fault CT to be damaged?

    Do I need to consider something else for what I am doing?

    I have attached a diagram.
  2. SgtWookie


    Jul 17, 2007
    I don't know what your generator is rated for, nor your load.

    Square D used to test their breakers to 1,000% overload or more.

    I don't know what they do for testing nowadays. I don't know what other manufacturers do as far as testing, either. However, the old Square D breakers could handle it.
  3. Jsw123

    Thread Starter Active Member

    Jun 20, 2009
    It is more a question of whether the CT can take it without burning up not so much whether or not the breaker can handle it. I think it has to do with the VA rating of the CT switch.
  4. loosewire

    AAC Fanatic!

    Apr 25, 2008
    You are working around very dangerous equipment, Minimum
    O.S.H.S. Standards regulation1910.333-N.E.C.-11016 you need to stay
    away from this equipment ,let your safety supervisor deal with these problems
    if you want to continue to live. VERY DANGEROUS TO BE NEAR- DON'T
  5. 3ldon

    Active Member

    Jan 9, 2010

    I'm pretty sure OP is asking what happens to a breaker when the current grossly exceeds the rated current.
    and that depends on the current....
    On the back of the circuit breaker it will tell you what the short circuit current rating is, and most breakers are rated to 10,000 amps. this means that if I send a 10,000 amp current through the breaker, it will not explode.
    And by explode i mean send parts flying through the 16 gauge sheet metal circuit breaker panel.

    The short circuit current may indeed be that high if powered from a step down transformer of around a 100-1000KVA rating within a hundred feet or so. And I've heard stories of entire circuit breaker panels launching themselves across the room, or a bus bar bent, or vaporised, never had the chance to see it happen though :(

    In the case of a generator of a few kilowatts, the peak current available is only a few hundred amps, and only for a short amount of time, as the voltage drops so does the excitation.