Cable Path Signal Generator

Point Principle

Achieve precise fault location using the principle of acoustic-magnetic synchronous positioning. The specific implementation method is as follows:

By applying a pulse high voltage to one end of the buried power cable, a discharge arc is generated at the fault point, producing electromagnetic waves and acoustic waves—the acoustic-magnetic signals. The digital synchronous positioning instrument synchronously receives the acoustic-magnetic signals emitted by the discharge arc, and converts the time difference between the electromagnetic waves and acoustic waves received by the instrument into the straight-line distance to the fault point in digital form. At the same time, along the path where the cable is buried, the size of the fault point's discharge vibration sound is judged by the earphone based on the received acoustic waves. Above the fault point, the smaller the reading on the digital display screen, the louder the sound of the vibration wave, thereby accurately determining the precise location of the fault point.

Method: Spot-on Approach

The pinpointing process involves applying a high-voltage shock to one end of the cable to induce a discharge at the fault point. The operator holds a digital sound-magnetic synchronous pinpointing receiver and probe, positioning them near the fault point as initially measured by the cable fault tester. By receiving the arc discharge vibrations of the fault cable and the electromagnetic waves emitted by the cable, the operator determines the precise location of the cable fault based on the lower readings on the digital display and the louder sound of the vibration waves.

Upon initial power-up, the two-digit digital tubes on the surveyor's panel display the internal battery voltage of the surveyor (e.g., 8.0) as 8.0 volts; they then automatically switch to "0.0" (meters). During the switch between fixed-point/path functions, the display shows the internal battery voltage as well. During the fixed-point process, the display refreshes with each impact discharge at the starting point, as long as no vibration waves are heard. Each refresh of the display's digits indicates a normal discharge at the starting point, with the rate of blinking synchronized with the starting point's discharge cycle. During fixed-point operation, the ground probe moves forward along the path every 50 cm or so, listening for the vibration sound waves of the discharge at the fault point deep underground. Upon hearing seismic waves of a certain intensity, a numerical value is displayed. If this value is in sync with the discharge cycle and repeats, it indicates the straight-line distance from the ground sensor probe to the underground cable fault point. As the sensor probe approaches the fault point, this value decreases. Directly above the fault point, the discharge sound is loud but the displayed reading is small. When the sensor probe passes over the fault point, the displayed reading increases. At this point, slowly move the sensor probe forward and backward, observing the digital tube readings carefully. The point below where the reading is smaller and the discharge sound is louder is the fault point. The displayed value at this moment indicates the approximate burial depth of the fault point's cable.

During the pinpointing process, some irregular numbers may occasionally appear at random. These are interference from environmental noise and should be disregarded. The sound is the true signal from the fault point only when the underground vibration waves detected by the sensor probe synchronize with the high-voltage discharge (synchronizing with the refresh of the digital display). This effectively eliminates interference from environmental noise.

The theodolite should be charged as soon as the internal voltage drops below approximately 7 volts after a certain period of use. Failure to do so may result in reduced theodolite accuracy or increased noise, affecting normal operation.

Path Detection Principle

Path Detection Principle: Primarily, it uses the electromagnetic waves of the path signals radiated by cables and the directional characteristics of magnetic antennas to locate buried cables and find their paths.

Prior to implementing the cable path detection, the grounding wire at the cable's starting end must be handled: disconnect the grounding braid from the cable head's grounding system, and ensure the grounding wire of the cable to be tested is reliably grounded. At the cable's starting end, the red clip (core wire) of the path signal generator's signal output cable is clamped onto the cable's braid, while the black clip (ground wire) is clamped onto the system ground.

After powering on the path signal generator, a 15KHz current signal, modulated by audio, is applied to the cable. Path signal electromagnetic waves are emitted above the cable's path. A digital synchronous fixed-point receiver is used to capture the 15KHz electromagnetic waves emitted by the current. After amplification and demodulation, the audio signal is sent to the headphones. By judging the change in the volume of the sound heard through the headphones, the buried path of the cable can be accurately determined.