GPS Synchronized Power System Phase Angle Measurements

Robert E. Wilson, Patrick S. Sterlina

Abstract:	Before a major new 500 kv transmission line was placed in service between Oregon and the San Francisco, Cali- fornia area, a series of high-voltage short circuit tests were preformed 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 equ- ipment for the measurement and analysis of key power system quantities. Before the testing, the authors installed two GPS syn- chronized phasor measurement units (PM&). The PMUs use GPS to globally synchronize the measure- ment of the state vector of the power system, the com- plex voltages of substation busses. Complex voltage means the magnitude and the relative phase angles of substation voltages. GPS provides the global time refer- ence marker for phase angle measurement. One elec- trical degree of the 60 Hertz waveform equals about 46 microseconds. Across short transmission lines (less than 50 km), measurements may need to be made to 0.1 elec- trical degree, which translates to clock synchronizations of roughly 5 microseconds. 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.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	1149 - 1155
Cite this article:	Wilson, Robert E., Sterlina, Patrick S., "GPS Synchronized Power System Phase Angle Measurements," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 1149-1155.
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