比流器飽和偵測與飽和電流修正技術之研究

Research on Techniques for Detection of Current Transformer Saturation and Correction of Saturation Current

陳嘉鴻(Chya-Hung Chen)

指導教授 ： 林穎宏

長榮大學/管理學院/經營管理研究所(博)/碩士(2007年)

https://doi.org/10.6833/CJCU.2007.00146

摘要

電力系統之輸電線故障電流常含有大量指數衰減直流成份，易造成比流器飽和而引起二次側電流扭曲，進而使數位保護電驛誤動作或動作延遲。本文提出比流器飽和偵測技術與飽和電流修正技術，在比流器飽和偵測技術中，根據比流器二次側電流於飽和開始與結束時皆有一明顯之轉折點，使用離散小波轉換以萃取特徵進而判定比流器飽和。對於所提出之比流器飽和電流修正技術，其藉由比流器無飽和時之二次側電流取樣值以估測故障電流之數學模型參數，可於比流器飽和時以波形合成方式產生電流波形以修正飽和電流。本文利用Matlab/Simulink模擬器以驗證所提出之演算法，模擬結果顯示所提演算法可正確判定比流器飽和，且可大幅降低因比流器飽和所造成之電流誤差。

關鍵字

指數衰減直流成份 ； 比流器飽和偵測 ； 比流器飽和電流修正 ； 數位保護電驛

並列摘要

The fault currents caused by transmission line faults in power system contain considerable exponentially decaying DC offset. Moreover, the CT tends to saturation due to DC offset, and the secondary current is distorted when saturation occurs. Such saturation current gives rise to mal-operation or delayed trip in digital protection relays. In this thesis, techniques for detection of CT saturation and correction for saturation current are proposed. Due to the obvious inflection points of secondary current at start and end of CT saturation, the proposed detection technique applies discrete wavelet transform to extract the features and then identifies the CT saturation. For the correction technique, the samples of unsaturated secondary current are used to estimate the parameters of mathematic model of fault current. Furthermore, the estimated parameters are utilized to synthesize the current waveform for correcting the saturated current. In this thesis, Matlab/Simulink simulator is used to verify the proposed algorithm. Simulation results show that the proposed algorithms are effective to identify CT saturation and the error of secondary current caused by CT staturation reduces significantly.

並列關鍵字

Exponentially decaying DC offset ； Detection of CT Saturation ； Correction of CT Saturation Current ； Digital Protection Relay

參考文獻

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