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The following elaborates from several aspects, focusing on how to reduce the time for locating line faults and provide the fastest solution for rapid recovery of the power system, thereby minimizing production losses caused by line faults. The so-called acoustic method is to locate faults based on the discharge sound of the faulty cable, suitable for cable fault diagnosis in cable tunnels and cable trenches. This method is particularly effective for flashover discharge from the high-voltage cable core to the insulation layer. The equipment used in this method is a DC withstand voltage tester. As shown in the circuit connection, SYB is the high-voltage test transformer, C is the high-voltage capacitor, ZL is the high-voltage rectifier silicon stack, R is the current limiting resistor, Q is the discharge ball gap, and L is the cable core. When the capacitor C is charged to a certain voltage value, the ball gap discharges to the faulty cable core, causing a spark discharge sound of "crackling" at the fault point where the core discharges to the insulation layer. Then, when ambient noise is minimal, audio amplification devices such as hearing aids or medical stethoscopes are used for detection. During detection, place the pickup close to the ground and move slowly along the cable route. When the "crackling" discharge sound is loudest, that location is the fault point. Safety must be emphasized when using this method; dedicated personnel should monitor both the test equipment end and the cable end. This method has been used multiple times in the external line projects of Xingangfan Steelmaking Plant and has achieved very good results. The bridge method involves using a double-arm bridge to measure the DC resistance value of the cable core, then accurately measuring the actual cable length, and calculating the fault point based on the proportional relationship between cable length and resistance. It is suitable for directly buried or conduit cables that cannot be directly observed. For faults where the core wires are directly short-circuited or the contact resistance at the short-circuit point is less than 1Ω, the judgment error is generally not more than 3m. For faults with contact resistance greater than 1Ω, the method of applying higher voltage to burn through can be used to reduce the resistance to below 1Ω, and then this method can be applied. The measurement circuit is shown in Figure 2. First, measure the core wire RX+R, where R is the resistance of one phase (a or b) to the fault point, and R is the contact resistance at the short-circuit point. Then, from the other end of the cable, measure the resistance R(L-X)+R of the a and b core wires, where R(L-X) is the resistance of one phase (a or b) to the fault point. After measuring R1 and R2, short-circuit b and C as shown in Figure 3, and measure the DC resistance between the b and c core wires. Half of this resistance value is the resistance per phase core wire, denoted as RL. RL = RX + R(L-X). From this, the contact resistance at the fault point can be derived: R = R1 + R2 - 2RL. Therefore, the resistance values of the core wires on both sides of the fault point can be expressed as: RX = (R1 - R)/2, R(L-X) = (R2 - R)/2. Once the three values RX, R(L-X), and RL are determined, the distance X or (L-X) from the fault point to the cable end can be calculated using the proportional formula: X = (RX/RL)L, (L-X) = (R(L-X)/RL)L, where L is the total length of the cable. When using the bridge method, measurement accuracy should be ensured; the bridge connecting wires should be as short as possible, with sufficiently large diameter, and connections to the cable core should be made by crimping or soldering. All decimal places should be retained during calculations. 3. Capacitance current measurement method: During cable operation, capacitance exists between core wires and between core wires and ground. This capacitance is uniformly distributed, and the capacitance value is linearly proportional to the cable length. The capacitance current measurement method is based on this principle and is very accurate for measuring open-circuit faults in cable cores. The measurement circuit is shown in Figure 4, using a 1-2kVA single-phase voltage regulator, a 0-30V, 0.5-class AC voltmeter, and a 0-100mA, 0.5-class AC milliammeter. The resistance values of the core wires on both sides of the fault point can be expressed as: RX = (R1 - R)/2, R(L-X) = (R2 - R)/2. Once the three values RX, R(L-X), and RL are determined, the distance X or (L-X) from the fault point to the cable end can be calculated using the proportional formula: X = (RX/RL)L, (L-X) = (R(L-X)/RL)L. When using the bridge method, measurement accuracy should be ensured; the bridge connecting wires should be as short as possible, with sufficiently large diameter, and connections to the cable core should be made by crimping or soldering. All decimal places should be retained during calculations. 3. Capacitance current measurement method: During cable operation, capacitance exists between core wires and between core wires and ground. This capacitance is uniformly distributed, and the capacitance value is linearly proportional to the cable length. The capacitance current measurement method is based on this principle and is very accurate for measuring open-circuit faults in cable cores. The measurement circuit is shown in Figure 4, using a 1-2kVA single-phase voltage regulator, a 0-30V, 0.5-class AC voltmeter, and a 0-100mA, 0.5-class AC milliammeter. (1) First, measure the capacitance current of each core wire at the cable head (keeping the applied voltage equal) to obtain the values Ia, Ib, and Ic. (2) Then, measure the capacitance current of each phase core wire at the cable end, Ia', Ib', and Ic', to verify the ratio of the intact core wire to the broken core wire, and preliminarily determine the broken core. (3) According to the capacitance calculation formula C = 1/(2πfU), when the voltage U and frequency f are constant, C is proportional to I; since the frequency f of power frequency voltage is constant, as long as the applied voltage is kept constant during measurement, the ratio of capacitance currents equals the ratio of capacitances. Assume the total cable length is L, and the distance to the broken point is x, then Ia/Ic = L/x, so x = (Ic/Ia)L. 1. Determine the cable fault type - main insulation fault / outer sheath fault. To avoid bringing the wrong equipment, the detection equipment and methods for the two fault types are different; over 95% are main insulation faults. The output voltage of the locating power supply differs; for cables below 10KV, a 15KV output voltage cable fault locating power supply can be used, which is small and lightweight. For cables of 10KV and above, a 32KV output voltage cable fault locating power supply can be used, which has high energy but is heavier. 1. Use a megohmmeter (insulation resistance tester) or a multimeter to measure the insulation resistance of each phase of the faulty cable to diagnose the fault type, such as open circuit fault, high resistance fault, or low resistance fault. Understand whether the cable fault is a phase-to-phase fault or a phase-to-ground fault. 4. Use a low-voltage pulse reflection instrument to measure the waveform at the cable end to determine whether it is the fault waveform or the full cable length waveform. Use a cable path locator to determine the cable position and direction. The accuracy of the path has a significant impact on precise fault location. 1. At the cable head, use a cable fault locating power supply to discharge pulses to the faulty phase, with a reasonable output voltage to ensure breakdown discharge at the fault point. 2. Use a precise locator, preferably with acoustic-magnetic synchronization function, and listen for sounds within about 30 meters in the pre-located range. Compare the digital values; the point with the loudest sound and the smallest digital value is the fault point, and the precise range can be narrowed to within one meter, allowing excavation to reveal the fault point. Safe and convenient underground power cables are increasingly widely used, but once a cable fault occurs, it is difficult to quickly locate the exact fault point. Failure to promptly eliminate the fault and restore power often results in major losses due to power outages and production stoppages. Therefore, how to restore power in the fastest way with the lowest maintenance cost is a key issue for power supply departments when encountering cable faults.