GPS synchronized power system phase angle measurements

Abstract

AbstractBefore a major new 500 kV transmission line was placed in service between Oregon and the San Francisco, California area, a series of high‐voltage short circuit tests were performed on the transmission system. The short circuit faults produced a brief ‘delta function’ shock to the regional power system. This paper discusses the use of Global Positioning System (GPS) synchronized equipment for the measurement and analysis of key power system quantities.Before the testing, the authors installed two GPS synchronized phasor measurement units (PMUs). The PMUs use GPS to globally synchronize the measurement of the state vector of the power system, the complex voltages of substation busses. Complex voltage means the magnitude and the relative phase angles of substation voltages. GPS provides the global time reference marker for phase angle measurement. One electrical degree of the 60 Hz waveform equals about 46 μs. Across short transmission lines (less than 50 km), measurements may need to be made to 0.1 electrical degree, which translates to clock synchronizations of roughly 5 μs.The PMUs recorded the dynamic response of the power system phase angles when the northern California power grid was excited by the artificial short circuits. Power system planning engineers perform detailed computer generated simulations of the dynamic response of the power system to naturally occurring short circuits, e.g. faults caused by lightning. The computer simulations use models of transmission lines, transformers, circuit breakers, and other high voltage components. This work will compare computer simulations of the same event with field measurements.