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.

下面以故障點電阻為依據簡述一下測試方法：

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

(1)當故障點電阻等于無窮大時，用低壓脈沖法測量容易找到斷路故障，一般來說，純粹性斷路故障不常見到，通常斷路故障為相對地或相間高阻故障或者相對地或相間低阻故障并存。(2)當故障點電阻等于零時，用低壓脈沖法測量短路故障容易找到，但實際工作中遇到這種故障很少。(3)當故障點電阻大于零小于100Ω時，用低壓脈沖法測量容易找到低阻故障。(4)閃絡故障可用直閃法測量，這種故障一般存在于接頭內部，故障點電阻大于100Ω，但數值變化較大，每次測量不確定。(5)高阻故障可用沖閃法測量，故障點電阻大于100Ω且數值確定。一般當測試電流大于15mA，測試波形具有重復性以及可以相重疊，同時一個波形有一個發射、三個反射且脈沖幅度逐漸減弱時，所測的距離為故障點到測試端的距離；否則為故障點到電纜測試對端的距離。

(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、結束語電纜故障測試技術水平的提高，應針對不同的故障性質采取不同的方法，還要不斷引進新技術、新設備，同時也要在新設備上摸索經驗，開發新的功能。如現采用的發音頻信號給電纜，在故障點接收信號的測試技術，以及利用T16/910電纜故障測試儀的SDC系列高智能電纜故障閃測儀對故障點的準確定位。這些設備可以使其測量誤差控制在幾十厘米以內，直接找到故障點進行處理，提高了故障測尋的效率。

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、故障的類型電力電纜由于機械損傷、絕緣老化、施工質量低、過電壓、絕緣油流失等都會發生故障。根據故障性質可分為低電阻接地或短路故障、高電阻接地或短路故障、斷線故障、斷線并接地故障和閃絡性故障。

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、故障的判斷方法確定電纜故障類型的方法是用兆歐表在線路一端測量各相的絕緣電阻。一般根據以下情況確定故障類型：(1)當搖測電纜一芯或幾芯對地絕緣電阻，或芯與芯之間絕緣電阻低于100Ω時，為低電阻接地或短路故障。(2)當搖測電纜一芯或幾芯對地絕緣電阻，或芯與芯之間絕緣電阻低于正常值很多，但高于100Ω時，為高電阻接地故障。(3)當搖測電纜一芯或幾芯對地絕緣電阻較高或正常，應進行導體連續性試驗，檢查南京橋架是否有斷線，若有即為斷線故障。(4)當搖測電纜有一芯或幾芯導體不連續，且經電阻接地時，為斷線并接地故障。(5)閃絡性故障多發生于預防性耐壓試驗，發生部位大多在電纜終端和中間接頭。閃絡有時會連續多次發生，每次間隔幾秒幾分鐘。

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.