Apparatus and method for detecting resistive leakage current in surge arrester

A surge arrester resistive leakage current detector, comprising:

• a leakage current detecting unit (10) being connected between a system bus and a ground line to detect digital data for a total leakage current (IT) flowing through a surge arrester (1) to which a voltage has been applied through the system bus and including a current transformer installed between the surge arrester and the ground line and an A/D converter that samples, in a predetermined amplified period, the analog total leakage current (IT) detected by the current transformer to thereby detect the digital data for the total leakage current (IT);
• a reference point detecting unit (20) to detect a time when a voltage is 0V based on a characteristic pattern shown in the total leakage current (IT) when the applied voltage applied to the surge arrester is 0V since the applied system voltage is not detected and to select the time as a reference point;
• a resistive leakage current calculating unit (31) to calculate a resistive leakage current (IR) by adding a term, which is in phase with a virtual applied voltage which is 0V at the reference point, of a Fourier series of the total leakage current (IT) for one period starting at the reference point, wherein the resistive leakage current calculating unit sequentially performs rearranging the one-period total leakage current to start at the reference point, obtaining a Fourier series by Fourier-transforming the rearranged one-period total leakage current, and calculating the resistive leakage current by adding the term of the Fourier series which is in phase with the voltage which is 0V at the reference point;
• and
• a reference point verifying/correcting unit (32) to correct the reference point until the calculated resistive leakage current (IR) shows a characteristic pattern of the resistive leakage current (IR) according to non-linear resistance characteristics of the surge arrester (1) and to repeat the resistive leakage current calculating and to determine that the resistive leakage current (IR) calculated based on the corrected reference point is the resistive leakage current (1), wherein the reference point verifying/correcting unit verifies the of the surge arrester accuracy of the reference point and, if the reference point is determined to be inaccurate as a result of the verification, corrects the reference point so that the resistive leakage current calculating unit recalculates the resistive leakage current according to the corrected reference point, and if the reference point is determined to be accurate, the resistive leakage current calculated according to the reference point determined to be accurate is determined to be the resistive leakage current of the surge arrester.