Overview of an automatic underground distribution fault location system

Con Edison uses power quality monitors to locate faults on its primary distribution underground network. The power quality monitors serve as the voltage and current sensors in an automatic fault location system. Fault measurements captured by the meters are downloaded automatically, integrated into a relational database, and processed for impedance calculations. The impedance calculations combined with up-to-date distribution circuit models and geographic information system data are used to build estimated fault location tables and map displays. The systems are integrated on Con Edison´s intranet and used in real-time by numerous groups within Con Edison including operations, system protection, and power quality. The system can detect and locate both single-phase faults and multi-phase faults. It sends alerts when subcycle faults and magnetizing inrush current transients are detected. For single-phase faults, the system´s accuracy regularly exceeds 80% success in estimating the fault location within 10% of the total number of the feeder structures. In 2008, the system was expanded to incorporate data from feeder relays and in 2009 it may be expanded to include data from transmission digital fault recorders. This document will present an overview of some of the parameters and practices for finding faults in place every day at Con Edison.