Adaptive algorithm for identifying OLTC position and its application on UHV voltage‐regulating transformer differential protection

摘要

The voltage-regulating transformer (VRT) with on-load tap changer is specifically used to adjust the voltage on the medium-voltage side of the ultra-high voltage power transformer. In practice, during the process of on-load voltage regulation, it is difficult to acquire the tap changer's positon, which is necessary for the calculation of the VRT differential current. Therefore, a novel algorithm is proposed to identify the real-time turns ratio of the VRT, adaptively, according to the structure of the ultra-high voltage power transformer. On the basis of the real-time turns ratio, the adaptive differential current is calculated. Both theoretical analysis and simulation results indicate that the proposed algorithm can track and calculate the turns ratio accurately, thus preventing unbalanced currents during the tap-changing process. Moreover, the performance of the VRT differential protection is evaluated under inter-turn fault conditions. Simulation results verify that the proposed algorithm can overcome the disadvantages in the existing protection schemes.