Simulation test of transformer short-circuit impedance based on equivalent model at different frequencies

Abstract

A distribution transformer is one of the most important equipments in the power grid, and its operational status is directly related to the security and stability of the entire power system. The performance of transformer windings determines the service life of the transformer. It is of great significance to evaluate the performance of transformer windings accurately, reliably, and effectively after the short-circuit test of the transformer. Aiming at the problem that the natural vibration frequency of the transformer measured before and after the short circuit may not be the same under the impact of the short circuit of the transformer, this paper puts forward the evaluation method for the performance evaluation of the winding of the transformer after the short circuit test and adopts the method of combining the analytic hierarchy process with the fuzzy evaluation method to quantitatively obtain the score for the performance evaluation of the winding. And that evaluation language is given according to the score. Finally, the evaluation of the transformer winding performance after the short-circuit test is realized. The evaluation results show that this method can effectively get the performance index of the transformer winding, without the need for hanging cover inspection, and solve the subjectivity of human eye observation to objectively, accurately, and quantitatively describe the performance state of the transformer winding. The method is favorable for power grid monitoring and maintenance personnel to accurately evaluate the operation stability of the transformer and has very positive significance for improving the short-circuit impact resistance of the transformer and ensuring the safety and stability of the operation of a power system.

Revisited Concept of Three-Phase Transformers’ Short-Circuit Resistances in Light of the Institute of Electric and Electronics Engineers (IEEE) Standard C57.110-2018

“…according to the load losses (P ccN ) and secondary current (I sN ) nominal values, determined after performing a short-circuit test at the industrial frequency (50-60 Hz) [33][34][35][36] or, by any of the procedures described in references [37][38][39][40][41][42][43][44]. The nominal short-circuit resistance (R ccN ) defined by Equation ( 2) is a parameter independent of the frequency of the winding current harmonics and has the same values in each phase of the three-phase transformers.…”

Load Losses and Short-Circuit Resistances of Distribution Transformers According to IEEE Standard C57.110

“…References [31][32][33][34][35] establish different methods for determining a transformer's shortcircuit impedances, but none specifies expressions for the short-circuit resistances as a function of the harmonic frequencies.…”

Simulation Analysis of Transformer Short Circuit Fault

“…In transformer accidents, the probability of occurrence is high, and the transformer short circuit accident poses a greater threat to the equipment, especially the short circuit fault on the low-voltage side of the transformer [2]. This article elaborates on the cause analysis and handling methods after the short circuit faul [3].…”