Cable fault tester is the “stethoscope” and “locator” in power system operation and maintenance



It is specially used to quickly locate faults such as breaks, short circuits, grounding (leakage), and high-resistance flashover in power cables or communication cables.

Simply put, its working logic usually follows the process of “first distance measurement (rough measurement), then pinpointing (precise measurement)”.

The following is a detailed analysis of the core principles, composition structure, and operation points of the cable fault tester:

⚙️ Core Working Principles

The cable fault tester is not a single technology but a combination of multiple technologies. Depending on the type of fault, the following principles are mainly used:

Pulse Reflection Method (Low Voltage Pulse Method / Radar Method)

Applicable scenarios: Low-resistance faults (short circuits), open-circuit (break) faults.

Principle: Transmit a low-voltage electrical pulse into the cable. When the pulse encounters an impedance mismatch point (such as a break or short circuit point), a reflected wave is generated. The instrument calculates the fault distance by measuring the time difference between the transmitted wave and the reflected wave

L=v×ΔT/2.

High Voltage Flashover Method (Impulse Flashover Method / Direct Flashover Method)

Applicable scenarios: High-resistance faults (such as damaged insulation but not completely short-circuited), flashover faults.

Principle: For high-resistance faults, low-voltage pulses cannot produce obvious reflections. In this case, a high-voltage generator is used to apply high voltage to break down and discharge the fault point, forming an instantaneous short circuit and generating a current traveling wave. The instrument captures this waveform to calculate the distance.

Acoustic-Magnetic Synchronization Method (Precise Pinpointing)

Applicable scenarios: Precise positioning on the ground at the site after distance measurement.

Principle: When the high-voltage pulse breaks down the fault point, it produces “sound (vibration)” and “electromagnetic waves”. The pinpointing instrument simultaneously receives these two signals. Using the time difference between the extremely fast propagation of electromagnetic waves and the slower propagation of sound waves, it searches on the ground for the point where the sound is loudest and synchronized with the electromagnetic signal. The point directly below this location is the fault point.