How to properly use a cable fault tester to quickly and accurately locate cable faults has long been a challenge for many. For years, fault detection has relied heavily on experience, making it difficult for new operators to effectively identify cable faults. Drawing on over a decade of accumulated expertise, our company has continuously upgraded and improved the cable fault tester, resulting in this user-friendly device that delivers precise fault distance measurement.
Before troubleshooting, we should first obtain detailed information from the staff about the cable conditions, such as whether adjacent cables are energized and in operation, the insulation status of the cable, and determine whether it is a high-resistance or low-resistance fault.
The cable fault tester consists of three main parts.
1. Distance measurement main unit;
2. Fault location;
3. High-voltage pulse generator and related accessories.
There are two methods for measuring faults using a distance meter:
1. Use the low-voltage pulse method: connect the red clip to the faulty phase and the black clip to the normal phase or the grounded armor. First, measure and save the data from the faulty phase, then measure and save the data from the normal phase, and compare the waveforms. For open-circuit faults or low-resistance faults under 100 ohms, the fault location can be identified by waveform comparison. However, for high-resistance faults, only the total cable length can be determined.
(1) Set the sampling method: pulse method
(2) Set cable length: Select an appropriate length between 50 m and 60 km.
(3) Set the cable wave velocity: four common types are built-in; if a special type is required, simply enter the wave velocity directly.
After setting up, click the start button to begin testing. The cable length will be automatically calculated, and you can also use the left and right keys for fine-tuning the length calculation.
2. High-voltage flashover method: Use a high-voltage pulse generator to puncture the fault point, causing it to discharge and produce rhythmic discharge sounds, ideally discharging once every 3 to 5 seconds. There are two types of high-voltage pulse generators: one is a split-type unit consisting of a control box, voltage booster section, high-voltage capacitor, and sphere gap; the other integrates the control, voltage boosting, capacitor, and sphere gap into a single unit. Today we are using an integrated high-voltage generator, which will be used as an example for demonstration. When operating the high-voltage pulse generator, personal safety must be strictly observed, and the following steps should be followed precisely.
1. Grounding: In addition to connecting the faulty phase to the high-voltage output, both the normal phase and the armor must be grounded. The high-voltage pulse generator has two grounding points: one for high-voltage ground and another for equipment ground. The high-voltage ground should be connected via a separate grounding rod, which must be properly grounded with a depth of approximately 50 cm; if the soil is too dry, water should be added. The equipment ground should be connected to the grounding point on the armor. The faulty phase should be left suspended and connected to the red high-voltage output cable, maintaining a safety distance of at least 20 cm from the normal phase and surrounding areas.
2. The grounding wire of the discharge rod is connected to the armor.
3. The other end of the cable should also be inspected, with the connection between the cable and equipment disconnected and left suspended, maintaining a safe distance of more than 20 centimeters, and the armor grounded.
4. Connect the distance meter to the sampling box, and place the sampling box parallel to the high-voltage ground wire with a spacing of approximately 3 centimeters. Adjust the distance according to the sampling signal to obtain an analyzable magnetic waveform. If the sampled waveform is incomplete or not fully formed, there are two possible reasons: first, the high-resistance fault has not yet broken down at the fault point, thus failing to generate an echo; second, poor grounding produces an echo, but it is too weak to be clearly detected. We need to systematically identify and resolve each issue.
5. After connecting the test leads, we begin increasing the voltage to perform flashover distance measurement.
⑴ Check whether the voltage adjustment knob is in the starting position.
(2) Adjust the sphere gap to approximately 2–3 mm.
(3) Turn on the power switch and slowly increase the voltage by adjusting the knob. Monitor the device’s voltage and current meters until discharge occurs, maintaining a discharge frequency of once every 3 to 5 seconds.
If the voltage cannot rise beyond a few kilovolts and the current meter continues to slowly increase, with normal current around 2–3 A, we should stop increasing the voltage and slightly widen the sphere gap. If the current does not decrease, turn off the power supply, discharge using a discharge rod, and then check whether the sphere gap is still within normal range.
Another phenomenon occurs when the voltage rises to around 15 kV but no discharge happens; in this case, the gap between the spheres should be appropriately reduced.
(4) The high-voltage pulse generator has started discharging; we need to turn on the distance meter to sample the flashover and analyze the fault location.
First, set the sampling method: Flashover method
Then click the “Start” button to begin measurement. The waveform will automatically refresh each time a flashover occurs. If the amplitude change of the waveform is small and not obvious with each flashover, adjust the gain knob on the distance meter to enhance the sampling signal. Under normal conditions, the waveform peak should appear as a sharp spike. If the spike turns into a square wave, it indicates that the gain is set too high and should be reduced appropriately. If the waveform remains unclear, adjust the spacing between the sampling box and the high-voltage ground wire accordingly.
For certain high-resistance faults, breakdown and flashover discharge are less likely to occur, resulting in delayed secondary reflection waveforms and an overestimated test distance. Therefore, the fault location is determined by setting the cursor on the later waveforms. For difficult-to-analyze test waveforms, as long as the subsequent waveforms follow a regular pattern with approximately equal intervals between them, the earlier waveforms can be ignored, and the fault distance can be directly determined using the later waveforms.
HV HIPOT specializes in manufacturing cable fault testers and has many years of experience in the power industry. Our products are of top quality, and we warmly welcome customers to visit and purchase.
Post time: Jul-29-2026