Digital Underground Cable Fault Locator Acoustic Magnetic Pinpointer for

The XHDD503B Digital Underground Cable Fault Locator and 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 completes the precise positioning of the cable fault point within the rough measurement range and collects the acoustic and magnetic time difference, integrating positioning technology and path-assisted testing to provide multiple test modes and rich, diverse prompt information for efficient and accurate cable fault location.

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, 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 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 ambient noise, it often brings great difficulties to less experienced operators. The acoustic-magnetic synchronization method effectively avoids these problems.

The instrument's pinpointing mode is the acoustic and magnetic mode: it automatically displays the sound and magnetic field signal waveforms and automatically calculates the time difference of the acoustic and magnetic signals. It 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 soil coverings (such as under cement and stone slabs) the high-frequency components dominate, while on beach or soil coverings the low-frequency components dominate.

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 clearly defined; if the drawing data is incomplete, the path should be detected and marked. According to the distance-measurement results and considering the cable-head reel margin and terrain, the fault point location is roughly determined, generally within (coarse 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 pinpointing probe sensor to the sensor socket and the earphone to the earphone socket. In the selected area, place the sensor flat on the ground directly above the cable, pointing in the direction of cable laying, select the acoustic-magnetic synchronization mode, and observe the waveform while listening with the earphones. A recommended starting principle is low threshold, large gain and high volume. When the sound and the sound / magnetic waveforms are heard and seen, move the sensor probe every 1–2 m and monitor more than 2 discharge cycles at each point. Keep moving forward until the sound and waveform can no longer be heard or seen and the time difference changes from large to small and back to large; then go back to re-position. When re-positioning, increase the threshold, reduce the gain and lower the volume, and find the point where the sound and waveform are the largest together with the point where the time difference is the smallest — the overlap of the two is the fault point.