Cable Fault Tester is a comprehensive instrument specifically used to detect and locate fault points in power cables and communication cables. It is vividly called the "physical examination instrument" for cables or the "stethoscope" for power systems.
It is mainly used to quickly identify and precisely locate faults (such as short circuits, broken wires, insulation aging, etc.) when cable lines encounter obstacles, thereby significantly reducing power outage repair time.
⚙️ Core Functions and Working Principles
Modern cable fault testers typically adopt a "three-step" strategy to lock onto faults: fault distance measurement (pre-location) -> path detection -> precise pinpointing.
Fault distance measurement (pre-location): Determine the approximate length from the test end to the fault point.
Low-voltage pulse reflection method: Transmit low-voltage pulses into the cable. When they encounter a fault point (such as a broken wire or low-resistance short circuit), reflections are generated. The instrument calculates the distance by measuring the time difference between the transmitted and reflected pulses, combined with the wave speed.
High-voltage flashover method (impulse flash method/direct flash method): For high-resistance or flashover faults, apply high voltage to cause the fault point to break down and generate an arc, capturing the traveling wave reflection at the moment of breakdown to measure distance.
Secondary pulse/multiple pulse method (modern mainstream): While the high voltage breaks down the fault point, automatically transmit low-voltage pulses for comparison. By comparing the waveform differences before and after breakdown, it can extremely intuitively and precisely lock onto the fault point, with strong anti-interference capability.
Path detection: If the underground route of the cable is unknown, the instrument works with a path detector to use electromagnetic induction to detect the cable's burial path and depth, avoiding blind excavation.
Precise pinpointing: Within the approximate range of the distance measurement (usually within tens of meters), precisely find the surface location of the fault point.
Acoustic-magnetic synchronization method (most common): Use high voltage to cause periodic discharge at the fault point, producing "pop" sound waves and electromagnetic waves. The pinpointing instrument receives both signals. When the probe moves to the position where the discharge sound is loudest and the time difference between acoustic and magnetic signals is minimal, the fault point is directly below.
Step voltage method: Suitable for direct-buried cables with damaged outer sheath or low-resistance grounding faults. It locks onto the fault point by measuring the voltage difference on the ground surface.
