Study on high precision data acquisition system for transformer test

The active power measurement in the no-load transformer test (loss measurement) is difficult because it is low power factor and includes the non-sinusoidal current. Then the problems in developing the high precision data acquisition system and the resolutions are studied. The method combining synchronous method and quasi-synchronous method is studied and used. In the active power measurement, the voltage sampling is synchronous method and the current sampling is quasi-synchronous. Two analog to digital converters (ADC) corresponding to voltage and current are used and the sample initiating signals of two ADCs are same. The hardware design also includes the signal conditioning circuit and the electromagnetic compatible design. And the software design also includes the digital and knowledge-based discrimination. The circuit card suited for PC and the algorithms for computing active power are developed. Using sampled data in several signal periods and combining the software digital filter and knowledge-based discrimination, the precision is improved and less than 0.45%. The instrument discussed in this paper is used in the field