In the operation and maintenance of power cables, one type of fault gives frontline engineers the biggest headache: the high-resistance fault.
Unlike short circuits or broken conductors, these faults lack distinct characteristics; standard testing instruments often fail to detect them or provide inaccurate locations. Repeated troubleshooting attempts frequently come up empty, causing emergency repair times to drag on indefinitely. The key piece of equipment for solving this challenge is the high-voltage pulse generator—a device that is simultaneously familiar and unfamiliar to many.
Today, we will explore the high-voltage pulse generator in depth, covering everything from its operating principles to its practical applications.
Ⅰ. Why are high-impedance faults so "difficult to deal with"?
Cable faults are generally classified into two categories: low-resistance faults and high-resistance faults.
- Low-resistance faults: short circuits, ground resistance < 100 Ω, The fault point has low resistance, allowing reflected signals to be detected using the standard low-voltage pulse method; localization is relatively straightforward.
- High-resistance faults:flashover faults, resistance ranging from several hundred ohms to several hundred megohms,The insulation at the fault point has not completely broken down; low-voltage pulses cannot "penetrate" the fault, resulting in virtually no reflected waves and no clearly visible fault characteristics on the instrument.
In actual operations and maintenance, over 80% of cable faults are high-resistance faults—such as those caused by aging, moisture ingress, or localized insulation degradation—which typically manifest as high-resistance states. Relying solely on a low-voltage pulse tester to diagnose such faults is essentially like the "blind men and the elephant" scenario.
This is where a high-voltage pulse generator comes into play.
II. Core Principle of the High-Voltage Pulse Generator: Pulse Reflection Method
At its core, a high-voltage pulse generator is a controllable source of high-voltage pulse signals. Its operating logic is based on the classic pulse-reflection method.
The work process can be broken down into three steps:
- Pulse emission: The device outputs a high-voltage pulse signal to the cable under test, and the pulse propagates along the cable core at a speed approaching the speed of light.
- Reflection at the fault point: When a pulse encounters an impedance discontinuity (i.e., the fault point), a reflected wave is generated and travels back along the cable to the test end.
- Distance calculation: The instrument records the time difference between pulse transmission and the return of the reflected signal; by factoring in the wave propagation speed within the cable, the distance from the test end to the fault location can be calculated.
The key lies in the words "high pressure"——
Standard low-voltage pulses range from only a few volts to a few tens of volts; they cannot "penetrate" high-resistance fault points, and consequently, no reflection occurs. In contrast, a high-voltage pulse generator can output pulses ranging from several thousand to tens of thousands of volts, instantly breaking down the insulation at the fault point and forcing the generation of a reflected signal, thereby revealing the true nature of the high-resistance fault.
III. Three Core Functions of the High-Voltage Pulse Generator
1. High-impedance fault location — the core function
When used in conjunction with the waveform acquisition system of a cable fault tester, the high-voltage pulse generator enables preliminary localization of various high-resistance and flashover faults, narrowing the fault range down to within a few meters or tens of meters, thereby significantly reducing the workload associated with on-site excavation and inspection.
2. Flashover Test
To address concealed faults in components such as cable joints and terminations, a high-voltage pulse generator can be used to gradually increase the voltage and observe the level at which flashover discharge occurs at the fault site; this allows for both fault location and an assessment of the fault's severity.
3. Preliminary High-Voltage Withstand Test for Cables
Certain models of high-voltage pulse generators can also be used to perform DC withstand voltage tests on cables to verify their insulation integrity; this multi-functional capability reduces the amount of equipment that needs to be transported to the site.
IV. Selection Guide: Which parameters should be considered for high-voltage pulse generators?
There are many models of high-voltage pulse generators on the market; when selecting one, focus on these five key specifications:
| parameter |
Key Buying Points |
| Output voltage |
Common voltage ratings include 8kV, 16kV, and 32kV; the equipment must match the voltage rating of the cable under test. For 10kV cables, it is recommended to select a rating of 16kV or higher. |
| Pulse energy |
The higher the energy, the more complete the discharge at the fault point and the clearer the reflected signal—a factor of particular importance for long-distance cables. |
| Output method |
Supports switching between impulse high voltage and DC high voltage, offering greater practicality and adaptability to a wider range of fault types. |
| Portability |
Field operations often require carrying equipment, so factors such as weight, size, and whether a trolley case is used must be taken into account. |
| Safety Protection |
Ensure that over-voltage protection, discharge circuits, and grounding designs are robust; safety is the top priority for high-voltage equipment. |
V. Product Recommendation: Xuzhihui XHHV535-4TS+ High-Voltage Pulse Generator
The XHHV535-4TS+ is an integrated high-voltage pulse generator launched by Xi'an Xuzhihui for cables with voltage ratings of 10 kV and below.
Key features:
- Continuously adjustable output voltage (0–8 kV) meets the fault detection requirements of the vast majority of distribution network cables.
- Integrated design featuring a built-in high-voltage capacitor and discharge sphere gap; simple wiring allows for immediate use upon unpacking in the field.
- Multiple safety protections—including automatic over-voltage discharge and isolation between the control panel and the high-voltage circuit—ensure personnel safety.
- Compact and lightweight, with a dedicated portable case, enabling transport and operation by a single person.
- Highly compatible; can be paired with the full range of Xuzhihui cable fault testers and pinpointing devices to form a comprehensive fault detection solution.
Whether for the routine operation and maintenance of power companies, emergency repairs by construction crews, or practical training in vocational institutions, this equipment meets the requirements.
VII. Finally
Cable fault detection is never a task for a single piece of equipment; rather, it is a system-level operation involving a high-voltage pulse generator, a fault tester, a pinpointing device, and a cable tracer. Among these components, the high-voltage pulse generator serves as the "power source" for the entire solution—without sufficient high-voltage pulses, even the most sophisticated tester cannot capture the fault signal.
Selecting a reliable high-voltage pulse generator provides a "double safeguard" for cable fault detection: it enables you to handle not only simple low-resistance faults but also challenging high-resistance and flashover faults, ensuring that every repair operation is more efficient and precise.
If you are currently selecting cable fault detection equipment or facing difficulties in locating high-resistance faults during your work, please feel free to reach out and discuss this further.Contact us
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