Is Fault Location Killing Our Cable Systems?

Power outages caused by faults in underground cable systems can be difficult to locate, however it is always advantageous for a utility to restore power within a short time-frame in order to maintain a high level of customer satisfaction, system performance, and profitability. Although there are different ways to determine the location of a fault within a length of underground cable, a common methodology used by electric utilities involves the use of a voltage pulse unit known to many in the industry as a ‘thumper.’ As a derivative of a system wide cable reliability program, based on a condition assessment comparable to cable and accessory manufactures' quality control standards, one of the largest utilities in North America set forth a field experiment to help quantify the damage to cable insulation caused by fault location thumping. This paper provides insight into the harmful effects of field applied ‘thumping’ and offers recommendations on how utility operations managers can minimize their risk of repeat outages, increase customer satisfaction while maximizing safety, efficiency and reliability.