CHAPTER 7: COMMANDS AND TARGETS COMMANDS MENUN60 NETWORK STABILITY AND SYNCHROPHASOR MEASUREMENT SYSTEM – INSTRUCTION MANUAL 7-57Figure 7-1: PMU one-shot FlexLogic operands7.1.5.1 Testing accuracy of the PMUThe one-shot feature is used to test accuracy of the synchrophasor measurement. GPS-synchronized tests sets perform asimilar function to PMUs; instead of measuring the phasor from physical signals with respect to the externally providedtime reference, they produce the physical signals with respect to the externally provided time reference, given the desiredphasor values. Therefore the GPS-synchronized test sets cannot be automatically assumed more accurate than the PMUsunder test. This calls for a method to verify both the measuring device (PMU) and the source of signal (test set).With reference to the following figure, the one-shot feature can be configured to trigger a high-accuracy scope to captureboth the time reference signal (rising edge of the 1 pps signal of the IRIG-B time reference) and the measured waveform.The high-accuracy high-sampling rate record of the two signals captured by the scope can be processed using digitaltools to verify the magnitude and phase angle with respect to the time reference signal. As both the time reference and themeasured signals are raw inputs to the PMU under test, their independently captured record, processed using third-partysoftware, is a good reference point for accuracy calculations. Such a record proves useful when discussing the test results,and can be retained as a part of the testing documentation.Figure 7-2: Using the PMU one-shot feature to test synchrophasor measurement accuracy7.1.5.2 Collecting synchronized measurements ad hocThe one-shot feature can be used for ad hoc collection of synchronized measurements in the network. Two or more PMUscan be pre-scheduled to freeze their measurements at the same time. When frozen, the measurements can be collectedusing the EnerVista software or a protocol client.
