Effects of stray capacitances on high voltage current transformers

This paper evaluates the effect of stray capacitances between primary and secondary windings on current transformers (CT) used in high voltage networks. Ground potential at all windings is the typical configuration during laboratory calibration. However, in service, the primary winding is at high voltage potential. The variation of current errors between both working conditions is evaluated for a set of CTs. A calibration system was developed that measures the transformer errors under nominal voltage operation, and experimental results on different type of transformers are presented.