A Microcomputer Based Data Acquisition System for High Impedance Fault Analysis

Investigation of High Impedance Faults has long held a high priority at Pennsylvania Power & Light Company (PP& L). The Ratio Ground Relay has been developed in conjunction with Westinghouse Electric Corporation´s Advanced Systems Technology and Relay Instrument Divisions under PP&L sponsorship. As part of the research, six feeders were digitally modeled [1], one feeder was modeled on an analog computer [2], and staged fault tests [3] were conducted to gain data and observe relay operations under controlled conditions. Thorough development and analysis of the applicability of a new relaying technique requires long-term field testing. To ensure that the devices are performing according to design specifications, they must be monitored. This paper describes the analysis of four such monitoring schemes and discusses the unique application of commercially available home microcomputer equipment within the substation environment to automatically sample, record and transmit circuit data to a host microcomputer. It also describes the computer configuration, programming, and data transfer to the corporate mainframe computer. The Ratio Ground Relay and a conventional Ground Overcurrent Relay have been installed on one feeder from each of six substations to evaluate their performance during normal distribution system daily operation. The development of this unique microcomputer application is discussed in detail.