IEEE C37.118.1-2011 pdf free download – IEEE Standard for Synchrophasor Measurements for Power Systems.
Several details of the synchrophasor definition shall be emphasized. All measurements are on a common time base and related to a common frequency, so the phase angle measurements are directly comparable. Differences in the actual frequency are included in the phase angle estimation. The synchrophasor estimate also includes the effects of all other signal contributions such as oscillations and local frequency swings. Synchrophasors are functions of time and will change from one value to the next unless the signal is a pure sinusoid at nominal system frequency. A precise time reference (clock) is required to provide the UTC time to determine the phase angle φ .
4.3 Measurement time synchronization The PMU shall be capable of receiving time from a reliable and accurate source, such as the Global Positioning System (GPS), that can provide time traceable to UTC with sufficient accuracy to keep the total vector error (TVE), the frequency error (FE), and the rate of change of frequency (ROCOF) error (RFE) within the required limits. All measurements shall be synchronized to UTC time with accuracy sufficient to meet the requirements of this standard. Note that a time error of 1 µs corresponds to a synchrophasor phase error of 0.022 degrees for a 60 Hz system and 0.018 degrees for a 50 Hz system. A phase error of 0.57 degrees (0.01 radian) will by itself cause 1% TVE as defined in Equation (12). This corresponds to a time error of ±26 μs for a 60 Hz system and ±31 μs for a 50 Hz system. A time source FE of 0.083 MHz in a 60 Hz system or 0.1 MHz in a 50 Hz system will cause the maximum allowed steady-state FE of 0.005 Hz. Similarly, a time source with a varying frequency will cause a corresponding error in ROCOF (the relationship is not as direct as those above). A time source that reliably provides time, frequency, and frequency stability at least 10 times better than these values corresponding to 1% TVE is highly recommended.
The time source shall also provide an indication of traceability to UTC and leap second changes. For each measurement, the PMU shall assign a time tag that includes the time and time quality at the time of measurement. The time tag shall accurately resolve time of measurement to at least 1 μs within a specified 100 year period. The time status shall include time quality that clearly indicates traceability to UTC, time accuracy, and leap second status. Time and time quality for reporting and recording shall be derived from the PMU time tag and converted to the format and content as required.
5. Synchrophasor measurement requirements and compliance verification
5.1 Synchrophasor estimation A PMU shall calculate and be capable of reporting synchrophasor estimates as defined and described in Clause 4 The estimates shall include single phase or positive sequence synchrophasors, or both. Provision shall be made for the user selection of the measured values. Measurement accuracy, reporting times, and evaluation criteria are given in this clause. Note that measurements are actually estimates of a certain value; the terms measurement and estimate are used somewhat interchangeably in this standard.IEEE C37.118.1 pdf download.