Analysis Of Phasor Measurment Units Operation Under Various Grid Conditions

At the present, phasor measurement units (PMU) are widely used in systems for monitoring and analyzing the state of electrical grid. Phasor technologies allow you to solve a number of problems related to the accuracy of perception and processing of information, bandwidth, performance, etc. PMU can significantly reduce the network congestion, when transmitting the most complete information in automated control systems. However, any measuring device has measurement errors that negatively affect the quality of the information received. Measurement errors often cause inaccuracies or latency in the transmission of information to other devices. Therefore, it is necessary to analyze the distribution of the PMU measurement error. As shown in [1], the main sources of PMU error are signal sensors and an algorithms for obtaining estimates of current and voltage vectors. Voltage and current transformers (VT and CT) used to feed raw data to the PMU usually have problem concerning saturation of steel core, the maximum amplitude error of measurement class transformers is 1%, protection class transformers are 10%, and the maximum phase error is 6 mrad (9 mrad for CT). VT and CT are the main source of errors for PMU [1]. In this paper, the analysis of the functioning of the PMU in case of connecting the PMU to various CT and VT is carried out. Operation errors are compared with signals from measuring CT and CT for PACS‘s purposes and more accurate sensors. The accuracy of the operation is evaluated with connecting to optical CT (TV). The greatest interest is caused by the influence of the magnetic saturation of the measuring CT on the estimation of the PMU error. PMUs operate in a network where various disturbances, including short circuits, are possible. At the same time, the short-circuit current significantly exceeds the current range at which the specified and certified accuracy of the PMU is realized. In addition, measuring current transformers have residual magnetization, which also leads to an increase the PMU errors. The paper considers the dependence of the accuracy of the PMU readings on various factors, such as the parameters of the network mode, the level of the short-circuit current, its nature (taking into account the aperiodic component), the accuracy class of the CT (VT), the location of the PMU in the secondary circuit at the power facility, various perturbations that cause a change in the state of the magnetic system of measuring CT.