国内外金属氧化物避雷器的在线监测方法主要有以下几种：

On-line monitoring method of metal oxide surge arrester at home and abroad mainly has the following kinds: 

(1)全电流法[3]

(1) the current method [3] 

在电网电压不变的条件下，金属氧化物避雷器全电流中的容性分量变化不大，全电流的增加知识由阻性电流增加造成的。因此监测全电流的变化，在一定程度上能获知阻性电流的变化。但是，正常状况下，金属氧化物避雷器的全电流的容性电流分量远大于阻性电流分量，两者基波又成90°相位差，这就使得测出的全电流有效值或平均值常主要取决于容性泄漏电流分量。即使阻性电流增加一倍，全电流也无明显差别，因此这种方法监测的灵敏度很低，只有在严重受潮、严重老化或绝缘显著恶化的情况下才能表现出明显变化。

Under the condition of power grid voltage constant, capacitive component of metal oxide surge arrester all current changed little, the whole current the increase of knowledge caused by impedance current increase. So monitoring the current change, to a certain extent, can learn the change of impedance current. But, under normal conditions, the whole current of metal oxide surge arrester of capacitive current component is greater than resistance current component, the fundamental wave and 90 ° phase difference, this makes the measure of the leakage current to RMS or average often depends mainly on capacitive current component. Even resistance current double, there was no evident difference all current, so monitoring the sensitivity of this method is very low, only in serious be affected with damp be affected with damp, aging or insulation significant deterioration can show obvious change. 

(2)阻性电流三次谐波法

(2) impedance current harmonic method three times 

阻性电流三次谐波法是将全电流经带通滤波器检出三次谐波分量，根据MOA的总阻性电流与三次谐波阻性分量的一定比例关系来得到阻性电流峰值。由于各厂生产的阀片以及同厂生产的不同规格的阀片的特性不尽相同，导致三次谐波峰值Irx3与阻性电流峰值Irx间的函数关系不一样，而且Irx与Irx3的函数关系又随阀片的老化而变化的；MOA端电压（母线电压）中的谐波含量也对测量结果产生直接影响；此外，也无法反应MOA表面污秽、受潮的情况。因此，三次谐波法既不具通用性，也不能比较客观地反应MOA的实际运行工况。其优点是只需取MOA的总泄漏电流，不需要参考电压，比较方便。但当系统中含谐波分量较大时，则电容电流也将含三次谐波，使测量存在误差，容易造成误判。

Impedance current harmonic method is three times the total electricity flows through band-pass filter detection three harmonic component, according to three times the total resistance of earth-sized current and harmonic impedance component proportion relationship to get resistance current peak. Because GeChang production of valve plates, and with the factory production of different specifications of the different characteristics of the valve plate, lead to three peak Irx3 and harmonic impedance function relation between the peak current Irx are different, and the function relation between Irx and Irx3 and changes along with the aging of the valve; Harmonic content in the voltage of the earth-sized (bus voltage) also direct influence on the measured results; In addition, there is no reaction earth-sized surface filth, be affected with damp be affected with damp. Therefore, three harmonic method is neither generality, also cannot compare objectively reaction earth-sized actual operation condition. Its advantage is just take the total leakage current of earth-sized, don't need a reference voltage, more convenient. But when the system contains the harmonic component is bigger, the capacitive current will also contain three harmonic, make the measurement error, easy to cause miscarriage. 

(3)基波电流法

(3) the fundamental wave current method 

基波电流法是通过测量阻性基波电流变化来判断MOA的运行状况，这主要是从检测结果不受电网谐波电压的影响的角度考虑的。

Fundamental wave current method is determined by measuring the impedance of fundamental wave current changes to determine earth-sized running status, the main from the test result is not affected by power grid harmonic voltage of the point of view. 

(4)补偿法

(4) compensation method 

由于金属氧化物避雷器的劣化主要反映在阻性电流的增大，如果将流经避雷器总电流中的容性电流平衡掉，直接监测其阻性电流的变化就可以反映MOA的劣化状况。该方法比全电流法更灵敏。但当电网电压含有谐波时，难以克服容性谐波电流对测量的影响、电压互感器相移的影响，容性分量无法完全补偿掉。

Due to deterioration of metal oxide surge arrester is mainly reflected in the increase of impedance current, if the total current through the arrester the capacitive current balance, monitor the change of its resistance current directly can reflect the degradation of earth-sized condition. This method is more sensitive than the current method. But when grid voltage containing harmonic, difficult to overcome capacitive harmonic current to measure the effect of voltage transformer, the influence of the phase shift, capacitive component cannot fully compensated. 

(5)数字谐波法

(5) the digital harmonic method 

数字谐波法是将稳态或暂态的波形信号转换为离散化的数字量，采用软件傅里叶变换分离各次谐波电压和电流，以计算出阻性电流各次分量，该方法的特点是以软带硬。数字谐波法与常规的补偿法相比，对总泄漏电流、基波阻性电流的测量结果是一致的，当电压中含有高次谐波时，数字谐波法更能准确灵敏地反映阻性电流中的高次谐波分量，同时降低了硬件设计的复杂度，增加系统设计的灵活性。目前，我局安装并投入运行的避雷器在线监测装置都采用此监测方法。

Digital harmonic method is to steady state or transient waveform signal conversion for discretization of the digital quantity, separation by software Fourier transform every harmonic voltage and current, to calculate the resistance current of every component, the characteristics of this method is based on soft hard. Digital harmonic method compared with conventional compensation method, the total leakage current, wave impedance measurement result is consistent with the current, when the voltage contains higher harmonic, sensitive digital harmonic method is more accurate to reflect the higher harmonic impedance current component, at the same time reduce the complexity of hardware design, increase the flexibility of the system design. At present, our installation and commissioning of arrester on-line monitoring device is the monitoring method.