Satellites for power system applications

With the launch of GPS satellites, extremely accurate timing signals are now available all round the world and for a variety of purposes. By installing low-cost receivers in power system substations, synchronised pulsing is available for applications such as time tagging of data collected by any power system monitor. This article describes how the system works. The techniques discussed for phasor measurement are particularly applicable to the interconnected high-voltage transmission system where high-speed data communication links already exist and control centres have been installed for data processing and network optimisation. The provision of phasor measurements, by the modification of existing data-acquisition hardware to control the sampling with GPS derived signals and to interface the equipment into existing communication channels, is probably comparable in cost to a protection relay, although the additional security provided by adding phasor measurements to the state estimator already incorporated in the EMS will need to be evaluated for each utility