Cable Fault Pinpointer | Acoustic Magnetic Synchronization Locator with Path

The XHDD503C Cable Fault Pinpointer uses the acoustic and magnetic synchronization method to determine a power cable fault point. Electronic flashover is generated by the impact discharge generator, picked up and amplified by the corresponding probe, and the precise location of the fault point is determined by auditory and visual judgment. It is a device that completes the precise positioning of the cable fault point within the rough measurement range and collects the acoustic and magnetic time difference. It integrates positioning technology, path-assisted testing and other technologies, providing multiple test modes and rich, diverse prompt information to complete cable fault location efficiently and accurately.

This pinpointing instrument is suitable for low-resistance, short-circuit, open-circuit and disconnection faults of power cables, high-frequency coaxial cables, street light cables and buried wires of various materials, cross-sections and media, as well as high-resistance leakage and high-resistance flashover faults. 

The device uses the acoustic-magnetic synchronization method to accurately determine the fault location. It is a very accurate and unique location method, based on the traditional acoustic pinpointing method with the added detection and application of electromagnetic signals.

When the high-voltage generator performs impact discharge on the faulty cable, the sound generated by the discharge at the fault point is transmitted to the ground. The sound signal is picked up by a highly sensitive probe; after amplification, a "pop" sound is heard through the headphones. The built-in probe receives the magnetic field signal in real time and, using the principle that the magnetic field propagates much faster than sound, determines the distance of the fault point by detecting the time difference between the electromagnetic signal and the sound signal. The sensor position is moved to find the point with the smallest acoustic-magnetic time difference, and the exact fault location is directly below it.

Traditional acoustic pinpointing instruments generally monitor only with earphones, or rely on meter-pointer swing to identify the discharge sound at the fault point. Since the discharge sound disappears in an instant and is not much different from the ambient noise, it often brings great difficulties to less experienced operators. The acoustic-magnetic synchronization method effectively avoids these problems of the traditional acoustic method.

The instrument is operated by touch screen or by the one-button adjustment control. The operation interface includes a waveform display area and a parameter adjustment area.

The sound channel filter has a factory default bandwidth of 100 Hz–1600 Hz. Appropriate filter parameters can be selected for different sites — for example, on hard pavement close to the fault point the high-pass filter preserves the high-frequency impact-discharge sound best, while further away or on soft soil or sand the low-pass filter is suitable. Bandpass filtering is a compromise between the two.

The acoustic and magnetic synchronization pinpointing requires a high-voltage impact signal generator working in a periodic discharge state. Wiring methods include the phase-to-armored method (preferred when there is phase-to-ground insulation damage, as discharge-sound attenuation is small), the phase-to-phase method (for a simple phase-to-phase fault without combined grounding), and the wiring method for a simple disconnection fault.

Before pinpointing, the cable path should first be clear; if drawings and data are incomplete, path detection should be carried out and marks made. Based on the distance-measurement results and considering the cable-head plate margin and terrain, the fault point location is roughly determined, generally within (distance-measurement value ± 50 m). After ensuring the fault point is penetrated and the discharge cycle of the high-voltage pulse generator is 3–5 seconds, start pinpointing directly above the cable in the selected area.

Connect the probe sensor to the sensor jack and the earphone to the headphone jack. In the selected area, place the sensor flat on the ground directly above the cable, pointing in the direction of cable laying, and select the acoustic and magnetic synchronization mode. Observe the waveform and listen with the headphones to start pinpointing. A recommended starting principle is low threshold, large gain and high volume. After hearing the sound and seeing both the sound waveform and the magnetic field waveform, move the sensing probe about every 1–2 m and monitor more than 2 discharge cycles at each point. Keep moving forward until the sound or waveform can no longer be heard or seen and the time difference value changes from large to small and then to large; then go back and re-point. When re-pointing, increase the threshold, reduce the gain and lower the volume, find the point where the sound and waveform are the largest and the point where the time difference is the smallest — the coincidence of the two points is the fault point.