High Voltage Bridge Cable Fault Locator
Murray bridge fault locator with a built-in 15 kV constant-current source, for cable sheath faults, high-resistance breakdowns and low-insulation defects.
- Locates faults, burns through fault points and runs DC withstand tests in one unit
- High test voltage and current with strong interference rejection, stable in the field
- Four-terminal measurement removes lead-resistance error
- Compact and light at 11.5 kg or less; test circuit isolated from the HV source for safe operation
Overview
The HUAC high voltage bridge cable fault locator is based on the Murray bridge principle. It locates outer sheath faults on high-voltage cables, breakdown points in installed power cables, and defects that have not broken down but show low insulation resistance. Cable manufacturers also use it to locate defects in cable at the factory.
A switch-mode power supply forms a high-voltage constant-current source with an open-circuit voltage of −15 kV and a short-circuit current of 30 mA. A high-sensitivity amplifier and galvanometer indicate bridge balance together with a ratio potentiometer, and the whole bridge floats at high potential. The test lead is a purpose-designed two-core high-voltage rubber cable, and four-terminal measurement removes the error that lead resistance would otherwise add. Front-panel controls stay at ground potential, and the bridge is operated through an insulated rod.
The constant-current source and the bridge are built into one portable industrial plastic case, so the instrument combines high test voltage with low weight, simple operation and safe use.
Faults it is suited to
- High-resistance breakdowns in installed cable, especially linear high-resistance faults that are hard to burn down to low resistance, such as breakdowns at cable joints.
- Flashover faults. After breakdown the constant-current source sustains the arc, so a stable current flows through the bridge and the bridge stays sensitive enough to balance.
- Defects that have not broken down but show low insulation resistance, for example a cable that measures low on an insulation tester but does not fail at operating voltage.
Who uses it
- Cable test and repair teams at utilities and large industrial power users. Most breakdowns can be pre-located quickly with the bridge, then confirmed with HUAC DT series TDR fault locators and DL series pinpointers for faster, more reliable location.
- Smaller utilities and mid-sized plants with a limited cable network, known routes and few faults a year. A full reflection-method kit costs more and needs experienced operators. The bridge locator costs less, is simple to use and covers day-to-day needs.
- Cable manufacturers, to locate breakdown points in cable at the factory. With an optional digital capacitance meter it can also find open conductors. It is light enough to take to customer sites for fault location service.
Technical specifications
| Output | |
|---|---|
| Test voltage | Negative, 0 – 15, continuously adjustable kV |
| Maximum current | 30 mA |
| Burn-through voltage | Negative, 0 – 15, continuously adjustable kV |
| Burn-through current | 30 mA |
| Measurement | |
| Ratio accuracy | ± (0.2% · L ± 1) m |
| Interference rejection | > 100 V AC |
| Other functions | Zero-position start |
| General | |
| Power supply | 220 V AC ±10%, 50 Hz |
| Dimensions (L × W × H) | 450 × 330 × 320 mm |
| Weight | ≤ 11.5 kg |
Specifications may change without notice. Contact us for the latest datasheet.
Applications
Scope of supply
| High voltage bridge cable fault locator | × 1 |
| Discharge rod with ground lead | × 1 set |
| Dedicated ground lead | × 1 |
| Power cord | × 1 |
| Dedicated shorting lead | × 1 |
| Spare 9 V battery | × 1 |
| User manual | × 1 |
| Certificate of conformity | × 1 |
| Packing list | × 1 |
Downloads
The datasheet and user manual for this instrument are sent on request, usually within one business day.
Frequently asked questions
What types of cable fault can the bridge locator find?
It locates outer sheath faults on high-voltage cables, high-resistance breakdowns in installed cable (including linear high-resistance faults at joints that are hard to burn down), flashover faults, and defects that have not broken down but show low insulation resistance.
How does the Murray bridge method work with a constant-current source?
The built-in source delivers up to 15 kV and 30 mA at constant current. When the fault breaks down, the source sustains the arc, so a stable current flows through the bridge. You balance the bridge with the ratio potentiometer and read the fault position as a percentage of cable length. Four-terminal measurement removes the error caused by lead resistance.
How accurate is the fault distance?
The ratio accuracy is ± (0.2% · L ± 1) m, where L is the cable length. Use the bridge to pre-locate the fault, then pinpoint the exact spot before excavation.
Do I still need a TDR fault locator and a pinpointer?
Professional cable test teams use the bridge together with HUAC DT series TDR fault locators and DL series pinpointers, so each method covers the others' weak points. Smaller utilities and plants with short cables and known routes often use the bridge locator on its own for day-to-day faults.
Can cable manufacturers use it in the factory?
Yes. It locates breakdown points in finished cable at the factory, and with an optional digital capacitance meter it can also find open conductors. At 11.5 kg or less, it is easy to take to customer sites for fault location service.
How is the operator protected from high voltage?
The bridge floats at high potential while the front-panel controls stay at ground potential, and the bridge is operated through an insulated rod. The test circuit is isolated from the HV source, the output only starts from the zero position, and a discharge rod with ground lead is supplied as standard.
What power supply does it need?
The standard unit runs on 220 V AC ±10%, 50 Hz. If your sites use a different supply, tell us when you request a quote.
Have another question? Ask our application engineers.
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