Restrictions on the performance of medium voltage arresters due to automatic disconnector

Distribution surge arresters, when degraded or submitted to discharge currents above their withstanding limits, may present problems to work properly, compromising the safety of the equipments they should protect. In this case, the arrester´s automatic disconnector should actuate, disengaging it from the network and indicating the necessity of the arrester replacement. The problem is that these disconnectors present a random actuation, sometimes bursting in normal operation conditions, others, not actuating when necessary. This behavior may be extremely detrimental to the network, as it may indicate the removal of good arresters or, on the other hand, allow the immovability of defective ones. This paper presents an study on the behavior of automatic disconnectors, in field and laboratory, and suggestions for the improvement of these components.