Timetagging and Delays in Phasor Measurement Systems

2013. — 9 c.Direct estimation of phasors from power signals is a concept that grew out of computer relaying in the 1980’s. The construction of a stand-alone Phasor Measurement Unit (PMU) in 1988 was made possible by the introduction of relatively high-power microprocessors for the high computational burden, and the Global Position System (GPS) for precise timing. Phasor measurement systems are now extensively deployed worldwide with applications only beginning to be developed. The most established use is data acquisition for event and system analysis. Real-time monitoring is also widely used, and at least a few control applications have been developed [2]. Each application has particular measurement process and overall system requirements. These include accuracy, resolution, reporting rate, and reporting delay as well as signal selections. This paper investigates the delay, or latency, in measurement and reporting, from the time the AC system is at a particular value until the data representing that value is available for use. The elements of delay in a phasor measurement system are broken down and described, and measured results in an operational system are presented. The terms latency and delay are used interchangeably, though usually refers to the overall effect.