GPS SYNCHRONIZED POWER-SYSTEM PHASE-ANGLE MEASUREMENTS

Before a major new 500 kV transmission line was placed in service betw een Oregon and the San Francisco, California area, a series of high-vo ltage short circuit tests were performed on the transmission system. T he short circuit faults produced a brief 'delta function' shock to the regional power system. This paper discusses the use of Global Positio ning System (GPS) synchronized equipment for the measurement and analy sis of key power system quantities. Before the testing, the authors in stalled two GPS synchronized phasor measurement units (PMUs). The PMUs use GPS to globally synchronize the measurement of the state vector o f the power system, the complex voltages of substation busses. Complex voltage means the magnitude and the relative phase angles of substati on voltages. GPS provides the global time reference marker for phase a ngle measurement. One electrical degree of the 60 Hz waveform equals a bout 46 mus. Across short transmission lines (less than 50 km), measur ements may need to be made to 0.1 electrical degree, which translates to clock synchronizations of roughly 5 mus. The PMUs recorded the dyna mic response of the power system phase angles when the northern Califo rnia power grid was excited by the artificial short circuits. Power sy stem planning engineers perform detailed computer generated simulation s of the dynamic response of the power system to naturally occurring s hort circuits, e.g. faults caused by lightning. The computer simulatio ns use models of transmission lines, transformers, circuit breakers, a nd other high voltage components. This work will compare computer simu lations of the same event with field measurements.