The invention belongs to electrical engineering and is used to determine such an indicator power quality as a coefficient of asymmetry (imbalance) in reverse sequence of the main frequency, which is characterized by the voltage of the reverse sequence of the main frequency The method consists in the fact that in the first stroke of operation the phase voltages A, B, C
connect to the respective input blocks input A, input B, input C, which contain serially connected blocks of galvanic isolation, scaling, frequency filtering, outputs of input blocks input A, input B, input C are connected to analog-to-digital converters ACPA, ACPV, ACPS, the outputs of which are connected to the inputs of registers RA, РВ, PC, respectively, in the second cycle connect the phase voltages A, B, C according to the input blocks input B, input C, input A, and the outputs ACPV, ACPS, ACDA – to the inputs of registers RA, RV, PC, respectively, in the third beat connect the phase voltages A, B, C to the respective input blocks input C, input A, input B, and outputs ACPS, ACPL, ACPV to the inputs of registers RA, RV, PC, respectively, in the fourth beat respectively, make up the codes of the instantaneous values of each triplet of vectors of the same name (UA1, UA2, UA3), (UB1, UB2, U B3), (UC1, UC2, UC3), the results of additions of each three are entered in the corresponding result registers РА, РРВ, РРС. These actions correct the error from the spread of the parameters measuring channels, which increases the accuracy of the measurement of the NZP OC.
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