SURGE VOLTAGE ARRESTER WITH VENTSAFE FEATURE

摘要

A surge voltage arrester assembly comprises a primary gas tube surge arrester (22) and an air gap secondary arrester that provides surge protection should the gas tube become vented to atmosphere. The secondary arrester has the air gap (42) defined by a rim (45) of one of the gas tube electrodes and an opposed roughened surface (40) of a metallic cup into which the gas tube is positioned. The roughened cup surface has a coating of graphite (43) applied thereto. The electrode rim (45) may or may not be roughened and/or coated. In a three element version of the invention wherein the gas tube has two line electrodes (70, 70) and a ground electrode (72), metallic cups (80, 80) are provided at opposite ends of the gas tube to cooperate with the ground electrode for forming secondary air gaps (86, 86) for each line electrode. The cup surfaces at the secondary air gaps are roughened and graphite (83) coated. An O-ring (88) seals each secondary air gap against the entrance of contaminants.