I. Pre-Test Preparation Techniques

First, collect the cable ledger, installation drawings, and historical fault records to clarify the cable model, length, routing, and joint locations, avoiding blind probing. Before operation, fully discharge the cable, confirm complete power-off at both ends, and set up a safety warning zone. Based on the fault type (open circuit, ground fault, short circuit, flashover), preliminarily select the test mode while checking the secure connections of the instruments, high-voltage leads, and grounding lines, eliminating any equipment malfunctions.

II. Coarse Measurement and Positioning Techniques

Prioritize the use of the pulse reflection method for rough distance measurement, adjust the instrument's sampling frequency and range to ensure the waveform is fully displayed on the interface. Conduct multiple tests and take the average to minimize single reading errors. If it is a high-resistance flashover fault, switch to the flashover testing method, gradually increase the test voltage, observe waveform changes, and record the approximate fault distance. Compare with the normal phase waveform of the same line to quickly distinguish between fault waves and interference waves.

III. Precision Pointing Techniques

Based on the rough distance measurement, conduct a step-by-step inspection along the cable path. When using the acoustic-magnetic synchronous method, place the sensor tightly against the ground, focusing on monitoring cable joints, turns, and areas around manhole covers. Use the tapping method in conjunction, applying pulse signals at estimated locations to distinguish the discharge sounds of fault points from ambient noise. In areas with multiple parallel cables, ensure phase differentiation to prevent misjudging faults in adjacent lines.

IV. Interference Elimination Techniques

During testing, stay away from strong electromagnetic equipment such as large motors, frequency converters, and high-voltage cabinets. When necessary, shorten the test leads and ensure proper shielding and grounding. For outdoor operations, avoid rainy or windy weather to prevent surface water accumulation and lead oscillations that may cause waveform distortion. If waveform anomalies occur, check whether the grounding is reliable and whether the connections are secure. Switch to a different filter setting to eliminate interference from noise.

V. Targeted Techniques for Different Faults

Low-resistance grounding/short-circuit fault: Directly use the low-voltage pulse method, with intuitive waveforms and fast readings; open-circuit fault: Focus on observing the open-circuit reflection wave and verify the full-length data; high-resistance flashover fault: Control the voltage rise rate to avoid excessive voltage damaging the cable, repeatedly compare waveforms to pinpoint the fault zone. For aged or multi-joint cables, segmental retesting is required to exclude false faults at joints.

VI. Conclusion and Data Retention

After positioning, conduct a retest to verify and confirm the fault location is accurate. Remove the wiring according to specifications, discharge any residual power from the instruments, and organize the cables and equipment. Fully document the fault type, test waveforms, positioning distance, and environmental conditions, then archive the records for future maintenance and reference in case of further repairs.