Calibration of Low-Power-Factor Wattmeters with a Nonsinusoidal Current and Unbalanced Voltage

This paper considers the calibration of Low-Power-Factor wattmeters in high voltage transformer no-load and load loss tests. The value of lowest power factor calibrated is evaluated in consideration of on-site test data and ability of uncertainty evaluation. The harmonic components of both testing current and voltage are measured in the field loss measurement. By analyzing the harmonic components, a nonsinusoidal current with a percentage of 3rd, 5th, 7th harmonic wave is applied for the laboratory calibration of Low-Power-Factor wattmeter in simulation of its on-site tests. There is a voltage unbalance in the field loss measurement. Unbalanced voltage is applied for Low-Power-Factor Wattmeters in comparison with balanced situations. For higher accuracy and resolution, the calibration systems of Low-Power-Factor wattmeters are improved with a nonsinusoidal current and unbalanced voltage standard.