Abstract
高壓架空配電線發生接地故障，若為被覆線，或裸銅線斷落於高阻抗地面 ，故障電流偏低，傳統的過電流電驛、接地過流電驛無法動作隔離故障者 ，稱為高阻抗故障。人畜誤觸斷落地面的導線，常引起感電事故，或因故 障時的火花釀成火災。為此，本論文旨在發展高阻抗故障的偵測方法，並 試製故障偵測器。主要成果如下：（1）改良既有的七項演算法：利用統 計學的信賴區間理論，自動設定偵測標置，經數值測試，改良後的演算法 ，偵測準確度大幅提高。（2）提出新的演算法（稱為低階偶次諧波變異 量故障偵測法）：以低階偶次諧波（二、四、六次諧波）為偵測指標，依 據指標的變異值呈卡方分佈，設計新演算法。並利用信賴區間理論自動設 定標置。經數值測試，驗證新法優於前述改良後的七項演算法。（3）與 台電公司共同進行三次高阻抗人工故障試驗：試驗包括電容器動作、負載 開關切換、高阻抗人工故障及測試本研究所發展的高阻抗故障偵測器。 （4）研製偵測器：經現場測試，偵測率尚稱理想。（5）改良低階偶次諧 波變異量故障偵測法使之兼具偵測極高阻抗故障的功能：修改上述本研究 提出的低階偶次諧波變異量故障偵測法，使之另具備偵測極高阻抗故障的 功能。經數值測試，可有效偵測極高阻抗故障。 The 11.4KV covered conductor fallen on the ground or the 11.4KV bare conductor fallen on the high resistance ground can cause the high impedance fault ( HIF ). Because their fault current is low, the conventional overcurrent ( CO ) and low energy overcurrent ( LCO ) relays have difficulty in detecting the fault . This 11.4KV conductor on the ground may cause fire hazard or human accident. Our research studies the detection algorithms to detect the HIF. The major contributions of our research are：（1） We design a relay setting scheme to improve seven well-known detection algorithms developed by previous researchers, and test the scheme numerically. The test results show that our scheme can enhance the detection accuracy significantly. （2） We propose a new detection algorithm which detects the HIF on basis of the summed variance of the second, fourth and sixth harmonics of feeder current. Combined with our automatic relay setting scheme, this new algorithm is generally superior, in terms of detection accuracy, to the above well- known seven algorithms. 3） We conduct the staged HIF three times, jointly with the Taiwan Power （Taipower） engineers, to test the HIF detector developed in this research. The field testing items include the switching of feeder capacitors, the switching of a load break switch for a normally loaded lateral, and the HIF.]4） The testing results of the detector are satisfactory. （5） We further modify the above lower-order harmonics variance detection algorithm so that the algorithm can detect not only the HIF but also the very high impedance fault whose fault current approaches zero.