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Study on Compensation Transformer Current Differential Protection

Author: WuYing
Tutor: JinEnShu
School: Tohoku Electric Power University
Course: Proceedings of the
Keywords: Compensated differential protection Magnetizing inrush Ridge Estimate Saturation Sliding window iteration DFT detection
CLC: TM407
Type: Master's thesis
Year: 2011
Downloads: 48
Quote: 0
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Abstract


The traditional differential protection is the ratio of braking and second harmonic restraint differential protection method . Inrush current , over-excitation current transformer saturation are the main cause differential protection malfunction . These types of phenomena in the final analysis are of core saturation caused . When the excitation current surge , while the second harmonic restraint to some extent played latching , however, still not perfect. Electromagnetic transformer will gradually be replaced by the electronic transformer do something saturation phenomenon , the subject at the same time conform to the current grid trends , the study contains only the saturation of the transformer differential protection , the magnetizing branch current compensation to the difference in the flow , rather than using any kind of surge atresia way improved differential protection scheme . As excitation current substituting assumed known magnetization curve of the transformer in the case when the detected transformer saturation , due to the poor flow at this time of the excitation current is large , the difference at this time flows into the magnetization curve , the saturated magnetic moment after t chain calculation , and then the time t of the magnetic chain substituting back to the magnetization curve , the excitation current of the time t , and this current compensation to a differential circuit , so that reliable protection action . The entire protection programs need to address two key issues : the transformer windings parameter identification and transformer saturation transient singular point detection . Resistance and leakage inductance of the transformer on both sides can only be measured by short-circuiting experiments and commonly used least squares estimation only recognition system transient transformer winding parameters . This article first introduced the ridge estimation method to solve the steady state identification equation pathological issues , simulation results show that the valuation error is less than 1% . Contrast singular point detection method based on the final iteration sliding window Fourier method , the method is simple in principle , a small amount of calculation , fast data updating , anti-interference ability , to meet the saturated transient singular point detection real-time requirements . Finally , through the EMTP simulation software and the dynamic simulation experiments to verify the correctness of the proposed program .

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CLC: > Industrial Technology > Electrotechnical > Transformers, converters and reactors > General issues > Maintenance,repair
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