It can be several things. It is all dependent on the problem.
* Too many things on the circuit and it is trying to trip the breaker but the surge is over before it can. in layman's term: It is like trying to stick 10 pounds of crap in a 5 pound box.
* The service capacity is too much at the transformer and can not carry the load. In layman's term: It is like the little engine that coundn't.
*They have a serious problem with their service neutral. There is potential fire or electrical damage to equipment due to higher the normal voltage. In layman's term:
it is like there is potential fire or electrical damage to equipment due to higher the normal voltage.
