Fault Conditions

Whenever something comes in contact with energized circuits and provides a path to ground or another phase, this is a fault condition. Most often these fault conditions are caused by tree limbs and/or animals such as birds and squirrels. In most cases utilities will employ an automatic breaker to momentarily de-energize the circuit to allow the tree or animal to clear itself from the line. The length and number of times the line is de-energized depends upon the standards at the utility. If the fault does not clear itself, the line will be de-energized via a fuse of other disconnect. This usually will mean an extended outage for all of the customers behind the fuse/disconnect.

By properly applying breakers, long duration outages can be avoided and reliability increased. However, in some cases it may be more appropriate to fuse problem circuits to de-energize prior to the operation of a breaker. This will mean fewer people are impacted by the momentary interruption but reliability is decreased.

With the increased saturation of microprocessors, this may actually result in a higher satisfaction level with the power. This type of coordination must be used carefully in order to maintain minimum reliability levels.