The development and application of voltage summation method with voltage transformers for determining ratio errors in power frequency

Abstract

The ratio error of a standard voltage transformer must be determined by metrological method. This article introduces and illustrates the principles of series-parallel summation method in 1954, and the bilateral series summation method in 1988 along with the bilateral series summation method with series type voltage transformers in 2006 and 2008. Benefited from the improvement of voltage summation circuits and facilities the errors of voltage ratios at 1000 kV/√3 and below have been derived in this way. The uncertainties of all ratios at and below 1000 kV/√3 are less than 4×10−5 (P=95%). For eliminating the errors caused by imperfect shielding and proximity effect, the theory of response superposition with a three ports network was presented and realized in 2012 on voltage summation operation. The results obtained by response superposition method were satisfactory. For instance, the uncertainty at ratio 500kV/√3 over 100V/√3 decreased from 15×10−6 to 7×10−6 (P=95%).