A PRECISE METHOD OF DETERMINING THE RATIO AND PHASE ANGLE ERRORS IN HIGH POTENTIAL INSTRUMENT TRANSFORMERS.

Abstract

An analysis of the available null methods indicates that difficulties are encountered with the accurate determination of  the ratio and phase angle errors of potential transformers in which voltages in excess of 30 KY are involved. The use of a high voltage condenser with a negligible loss angle has become universal. The uncertainties of the auxiliary apparatus in the different methods together with the circuit arrangement set a definite limit to the overall accuracy of the measurements.This paper describes a simple set-up which is capable of high sensitivity and accuracy of observation and derives theoretical expressions for accurate calculations. Vector diagrams are presented. for balance conditions. The factors influencing convergence and sensitivity are also considered. A brief description of the character of measuring equipment and technique employed precedes an investigation  into errors of typical single-phase and three-phase high potential transformers various load conditions and some  comparative data are also obtained.The paper concludes with a discussion of test results.