An International comparison of voltage-transformer calibrations to 350 kv

IN JUNE 1960, the Hydro-Electric Power Commission of Ontario inquired whether the United States National Bureau of Standards (NBS) in Washington could measure for them the ratio and phase-angle errors of a 350-kv voltage transformer then being built to their order. This request was also made at about the same time of the National Research Council of Canada (NRC) in Ottawa. Neither laboratory had, at that time, made calibration measurements on instrument transformers at this voltage level, but both had given the problem considerable thought; and it appeared that the request by Ontario Hydro afforded a unique opportunity not only to examine some of the problems involved in voltage-ratio measurements at 350 kv, but also to compare measurement results between the two national laboratories.