Ground fault circuit breakers for heat tracing

Abstract

This paper investigates the history of ground fault protection requirements and traces the technical advances in ground fault protection equipment in relation to electrical heat tracing. Electrical heat tracing presents a special challenge since the grounded metal braid places significant capacitance on the load side of the protection device. Various testing procedures have been established for ground fault circuit breakers, both personnel and equipment protection. These tests have been applied to circuits with capacitance equaling maximum typical capacitance seen in electrical heat tracing circuits. Two manufacturer's breakers and two manufacturer's electronic controls were tested. Eight different tests were run, including relay chatter, EFT (electrical fast transient), high inrush and radiofrequency interference. The tests show significant immunity to all extreme tests and provide both a sense of confidence and knowledge that nuisance tripping has largely been solved by technical innovation. The test procedures are discussed with relation to the typical electrical heat tracing load characteristics. Using ground fault detection equipment has become an acceptable form of monitoring for electrical heat tracing systems. This method of monitoring is briefly discussed. The paper puts in perspective the characteristics of electrical heat tracing with respect to ground fault protection equipment and helps the practitioner select and use this equipment with a greater understanding of its strengths and weaknesses. It also provides a summary method of trouble shooting EPD systems.