Overvoltage Protectors—A Novel Concept for Dealing With Overbuilt Distribution Circuits

This paper deals with a simple solution to a problem that has plagued overbuilt distribution circuits for decades-namely, protection for sustained overvoltage events. When two overhead circuits of different voltages exist on the same poles, the possibility exists that contact between the two circuits will occur. When this takes place, damage and failures occur to utility equipment on the lower voltage circuit and to customers´ end use equipment served from the lower voltage circuit. Traditional approaches have met with limited success largely due to their high costs or operational difficulties. The author´s preferred solution utilizes polymer housed station class arresters on the lower voltage circuit to limit the resulting overvoltage. They are intended to be employed in an expendable mode (i.e., they need to be replaced following a sustained overvoltage event). A field trial was arranged to demonstrate the effectiveness of the approach. This trial proved to be quite successful and cost effective, leading to the deployment of many more station class arresters for this function on the Dominion distribution system. A screening technique was devised to aid in applying the solution to a range of distribution voltage combinations and breaker/recloser clearing times.