New control-system power source for meter test equipment

Abstract

This paper describes a new control-system power source for meter test equipment to provide high accuracy setting of the voltage, current, phase angle and power for both the fundamentals and harmonics. The error tests of watt-hour meters are generally carried out by comparison method with a standard watt-hour meter. However, the setting value of the test points varies according as the ratings of watt-hour meters, and thereby it is necessary to set the ratings of watt-hour meters through a standard VCT to supply a constant electric power to the standard watt-hour meter. Furthermore, since the influence due to harmonics for the watt-hour meters is examined by comparison method with the standard watt-hour meter through the VCT, it is difficult to ensure high bandwidth and high accuracy owing to the VCT frequency characteristics. The new control-system power source which the authors have developed is designed to detect the voltage, current, phase angle, power, frequency and harmonic contents of various orders and then to feed them back to the oscillator, using the detector based on the digital sampling system. Therefore, it allows a constant power to be output with high accuracy for various waveforms. The setting accuracy of the voltage, current and power for the fundamentals and harmonics of the power source is higher than 0.05%.