(Fujian Institute of Metrology,Fuzhou 350003,China)
Abstract: In order to study the effects of differential circuit load for potential transformer(PT) on calibration results, two kinds of transformer test set with different principle and its calculating process are analyzed based on giving the technical requirements. The analysis results show that, differential circuit capacity of two kinds of transformer test set is equal if the current polarity indicator capacity consumed is ignored. Transformer test set additional load caused by differential circuit depends on the secondary side voltage drop of standard PT and PT under calibration. The effect of additional load is neglected when adopting double level PT with an accuracy of 0.002 to calibrate PT with an accuracy of 0.01 to 0.05.
Keywords: potential transformer; transformer test set; the differential loop; additional load