In-situ calibration of high voltage three-phase transformer loss measuring systems

The application of a computer-controlled current-comparator-based load loss standard to the in-situ calibration of two different types of high voltage three-phase transformer loss measuring systems at SMIT Transformers is described. The load loss standard simulates a high voltage inductive load at power frequencies which can provide load currents up to 2000 A at any power factor with a resolution of 1/spl times/10/sup -6/, and at test voltages up to 200 kV. It basically provides a known and stable power loss or reference power, determined by the test voltage and the power factor setting, to the transformer loss measuring system, such that its accuracy can be characterized over different voltage, current, and power factor ranges.