Performance of on-line fault distance monitor for distribution cable circuits

The causes for fault registrations in primary cable circuits include cable punctures either by age related deterioration or lightning or dig-ins, splice failures, arrester failures, elbow and related accessory failures, and transformer failures. The fault distribution by type is highly variable-dependent upon all parameters. But most are cable failures and are adjudged permanent-not temporary. Faulted circuit indicators (FCI) are mounted in or on enclosures to identify the location of the failed cable section. They respond to the fault current flux in the cable prior to the circuit interruption, or to loss of voltage. A single fault distance monitor (FDM) is used to monitor a complete circuit and provide a distance to the fault site. A typical circuit {e.g. loop, radial, etc.} encompasses 5 to 10 junction points. This paper describes the characteristics and comparative performance of this new device usable to speed the circuit restoration.