Analysis Of The Deformation Detecting Test Of Power Transformer Winding And Its Simulation Technology

The failure of transformer is often caused by near-by short pass. To find out the deformation in the winding after near-by short pass, fall cover checking is frequently applied. But due to the influence of the transformer structure, this method can not find out the deformation of the inner coil. In this paper, firstly Short Circuit Impedance Method (SCI), Low Voltage Impulse Method (LVI) and Frequency Response Analysis Method (FRA) are compared for the validity in Deformation Detecting Test for transformer winding. SCI is easier and better to represent the test result. But it is not sensitive to small deformation. LVI is very sensitive but is not good at anti-interference in field test. The analysis based on its test results still depends on the experts' abundant experience. FRA is good at anti-interference. The application of the poles subsection technology in frequency domain helps to find new characteristic quantities in frequency domain such as related coefficient of frequency spectrum and root-mean-square distance after subsection. Secondly, this paper analyzed the factors which could affect both SCI and FRA, and then make the test result repeatable. The relation between deformation in different part of transformer and the frequency response characteristics is simulated by PSPICE. The simulation results show that the inductance has a great influence on the low-frequency characteristics. The length wise direction capacitance would change the resonance frequency and had a great influence on the high-frequency characteristics. But it would have a smaller influence on the low-frequency characteristics. This influence is symmetrical compared the head end capacitance and the end capacitance. The capacitance over the ground would not change the resonance frequency remarkable but it would change the amplitude where is not the resonance frequency. Thirdly, this paper gave the method to calculate the short circuit current and calibrate the mechanical destabilization ability of transformer. Based on the consideration of short circuit current, anti-short pass ability of transformer and the mutual verification of deformation detecting test methods, Synthetic Judgment Method is put forward.