In- situ measurement of the current transformer burden in a current transformer testing system using a shunt resistor

Abstract

Both the ratio error and phase angle error of a current transformer (CT) are significantly affected by the CT burden connected in series to the secondary terminal of the CT. Thus, the precise measurement of this CT burden is required for the evaluation of the CT errors. A method for measuring the CT burden in- situ in a CT testing system (CTTS) has been developed by employing the non-reactive type shunt resistor. For the measurement of the CT burden, the shunt resistor was connected in parallel to the secondary terminal of the CT under test in the CTTS. The burden values represented by the apparent power and the power factor can be calculated from the resistance (and reactance), which was obtained by measuring the ratio error (and phase angle error) as a function of the resistance of the shunt resistor. The uncertainties in the measurements of the apparent power and the power factor for the rated burdens studied were found to be less than 2.1%. The CT burden values obtained using our method were consistent with those measured using a digital multimeter within the corresponding uncertainties.