Design of Capacity Loss Tester of Power Transformer

摘要

A capacity loss tester for no-load and with-load testing of power transformer has been developed. The tester has the ability of sampling the three-phase voltage and current simultaneously. Programmable counter array (PCA) unit in MPU, which captures zero-crossing of signal by the function of positive and negative edge trigger, is applied to the average phase detection of zero-crossing in bi-direction, in order to acquire the phase difference and period accurately. In terms of software, synchronism sampling method based on real-time parameter self-optimizing is adopted to minimize period truncation error, and the measuring accuracy is improved. The capacity of the power transformer is discriminated by table-look-up method in software, corresponding to different load loss. The testing result is converted from the value under testing temperature to the value under the condition of reference temperature (75°C).