Integrated detection and protection schemes for high-impedance faults on distribution systems

The authors describe two integrated microcomputer-based detection and protection schemes for distribution system faults including high-impedance faults. The main objective of the two schemes is to deal with single-line-to-ground faults of feeders on a distribution substation using delta-delta connection. The first scheme, based on an innovative fault-detection algorithm, identifies a faulty feeder by measuring varied phase angles between phase currents and bus voltages. The second scheme, including several existing detection algorithms, incorporates an expert system for selecting an algorithm suitable for a given application based on their advantages. A simulation software package is built to simulate the implementation of the two schemes and their combination. Using the simulation package and feeder fault data, simulation tests are made to verify the feasibility of the schemes, the algorithms, and the system structures suggested