1. Fault test methods in the past, the instruments and equipment used were qf1-a cable detector, Dlg-1 flash tester, Pathfinder and fault locator. Before the 1970s, the widely used cable fault test method was the electric bridge method, including resistance bridge method, capacitance bridge method and high voltage bridge method. This test method has large error and can not measure some types of faults. Therefore, at present, the very popular test method is flash method, which includes flash and direct flash, and the commonly used flash method is flash method. The flash test has high precision and simple operation. The equipment is mainly composed of two parts: high voltage generator and current pulse meter. The high voltage generator is used to generate DC high voltage or impulse high voltage, which is applied to the fault cable to force the fault point to discharge and generate reflected signal. The current pulse meter is used to pick up the reflected signal to measure the fault distance or directly measure the open circuit, short circuit or low resistance fault with low-voltage pulse.

下面以故障点电阻为依据简述一下测试方法：

The following is a brief description of the test method based on the fault point resistance:

(1)当故障点电阻等于无穷大时，用低压脉冲法测量容易找到断路故障，一般来说，纯粹性断路故障不常见到，通常断路故障为相对地或相间高阻故障或者相对地或相间低阻故障并存。(2)当故障点电阻等于零时，用低压脉冲法测量短路故障容易找到，但实际工作中遇到这种故障很少。(3)当故障点电阻大于零小于100Ω时，用低压脉冲法测量容易找到低阻故障。(4)闪络故障可用直闪法测量，这种故障一般存在于接头内部，故障点电阻大于100Ω，但数值变化较大，每次测量不确定。(5)高阻故障可用冲闪法测量，故障点电阻大于100Ω且数值确定。一般当测试电流大于15mA，测试波形具有重复性以及可以相重叠，同时一个波形有一个发射、三个反射且脉冲幅度逐渐减弱时，所测的距离为故障点到测试端的距离；否则为故障点到电缆测试对端的距离。

(1) When the resistance at the fault point is equal to infinity, it is easy to find the open circuit fault by measuring with the low-voltage pulse method. Generally speaking, pure open circuit fault is not often seen. Usually, the open circuit fault is a phase to ground or phase to phase high resistance fault or the coexistence of phase to ground or phase to phase low resistance fault. (2) When the resistance at the fault point is equal to zero, the short-circuit fault measured by low-voltage pulse method is easy to find, but this fault is rarely encountered in practical work. (3) When the resistance at the fault point is greater than zero and less than 100 Ω, it is easy to find the low resistance fault by measuring with low voltage pulse method. (4) The flashover fault can be measured by direct flashover method. This fault generally exists in the connector. The resistance at the fault point is greater than 100 Ω, but the value changes greatly, and each measurement is uncertain. (5) High resistance fault can be measured by impulse flashover method. The resistance at the fault point is greater than 100 Ω and the value is determined. Generally, when the test current is greater than 15mA, the test waveform has repeatability and can overlap, and one waveform has one emission and three reflections, and the pulse amplitude gradually decreases, the measured distance is the distance from the fault point to the test end; Otherwise, it is the distance from the fault point to the opposite end of the cable test.

2、结束语电缆故障测试技术水平的提高，应针对不同的故障性质采取不同的方法，还要不断引进新技术、新设备，同时也要在新设备上摸索经验，开发新的功能。如现采用的发音频信号给电缆，在故障点接收信号的测试技术，以及利用T16/910电缆故障测试仪的SDC系列高智能电缆故障闪测仪对故障点的准确定位。这些设备可以使其测量误差控制在几十厘米以内，直接找到故障点进行处理，提高了故障测寻的效率。

2. Conclusion to improve the technical level of cable fault testing, we should adopt different methods according to different fault properties, and constantly introduce new technologies and equipment. At the same time, we should also explore experience and develop new functions on new equipment. For example, the test technology of using the pronunciation frequency signal to the cable and receiving the signal at the fault point, as well as the accurate positioning of the fault point by using the SDC series high intelligent cable fault flash tester of T16 / 910 cable fault tester. These devices can control the measurement error within tens of centimeters, directly find the fault point for processing, and improve the efficiency of fault detection.

3、故障的类型电力电缆由于机械损伤、绝缘老化、施工质量低、过电压、绝缘油流失等都会发生故障。根据故障性质可分为低电阻接地或短路故障、高电阻接地或短路故障、断线故障、断线并接地故障和闪络性故障。

3. Type of fault power cable will fail due to mechanical damage, insulation aging, low construction quality, overvoltage, loss of insulating oil, etc. According to the nature of the fault, it can be divided into low resistance grounding or short circuit fault, high resistance grounding or short circuit fault, wire break fault, wire break and grounding fault and flashover fault.

4、故障的判断方法确定电缆故障类型的方法是用兆欧表在线路一端测量各相的绝缘电阻。一般根据以下情况确定故障类型：(1)当摇测电缆一芯或几芯对地绝缘电阻，或芯与芯之间绝缘电阻低于100Ω时，为低电阻接地或短路故障。(2)当摇测电缆一芯或几芯对地绝缘电阻，或芯与芯之间绝缘电阻低于正常值很多，但高于100Ω时，为高电阻接地故障。(3)当摇测电缆一芯或几芯对地绝缘电阻较高或正常，应进行导体连续性试验，检查南京桥架是否有断线，若有即为断线故障。(4)当摇测电缆有一芯或几芯导体不连续，且经电阻接地时，为断线并接地故障。(5)闪络性故障多发生于预防性耐压试验，发生部位大多在电缆终端和中间接头。闪络有时会连续多次发生，每次间隔几秒至几分钟。

4. The method to determine the type of cable fault is to measure the insulation resistance of each phase at one end of the line with a megger. The fault type is generally determined according to the following conditions: (1) when the insulation resistance of one or several cores of the cable to the ground is measured by shaking, or the insulation resistance between cores is less than 100 Ω, it is a low resistance grounding or short-circuit fault. (2) When the insulation resistance of one or several cores of the cable to the ground is measured by shaking, or the insulation resistance between cores is much lower than the normal value but higher than 100 Ω, it is a high resistance grounding fault. (3) When the insulation resistance of one or more cores of the telemetry cable to the ground is high or normal, a conductor continuity test shall be carried out to check whether there is a wire break in Nanjing bridge. If so, it is a wire break fault. (4) When one or more core conductors of the telemetry cable are discontinuous and grounded through resistance, it is a broken wire and grounding fault. (5) Flashover faults often occur in preventive voltage withstand tests, mostly at cable terminals and intermediate joints. Flashover sometimes occurs several times in a row, with an interval of a few seconds to a few minutes.