Electrical testing services
Cable Testing
Comprehensive high-voltage cable testing to verify insulation integrity, identify degradation, and prevent costly failures before they occur.
What Is Cable Testing?
Electrical cables are the arteries of any power system — and like any critical infrastructure, they degrade over time due to age, load cycling, moisture ingress, mechanical damage, and installation defects. Cable testing is the process of applying controlled electrical stress to a cable system to evaluate the condition of its insulation and identify weaknesses before they result in a fault.
J. Wesley Services Group performs cable testing on new installations (acceptance testing) and in-service systems (maintenance testing) in accordance with NETA standards. Our technicians use industry-leading test equipment and proven methodologies to deliver accurate, documented results you can act on.
Test Methods We Perform
We apply the right test method for each cable type, voltage class, and service condition — ensuring accurate results without unnecessary stress to the insulation.
VLF (Very Low Frequency) Testing
VLF testing applies an AC voltage at 0.1 Hz to evaluate cable insulation condition. It is the preferred method for medium-voltage XLPE and EPR cables, providing a thorough assessment with significantly less stress than DC hipot testing. VLF is widely accepted for both acceptance and maintenance testing of extruded dielectric cables.
DC Hipot Testing
DC high-potential (hipot) testing applies a direct current voltage to the cable to verify insulation integrity and check for gross defects. It is commonly used on older paper-insulated lead-covered (PILC) cables and certain maintenance applications where DC testing is appropriate for the cable type and insulation system.
Insulation Resistance (Megger) Testing
Insulation resistance testing uses a megohmmeter to measure the resistance of cable insulation in megohms. It is a fast, non-destructive baseline test performed on cables of all voltage classes to detect moisture, contamination, and gross insulation breakdown. Results are compared against NETA acceptance criteria and historical trending data.
Tan Delta (Dissipation Factor) Testing
Tan delta testing measures the dielectric loss angle of cable insulation, providing a sensitive indicator of insulation aging, moisture ingress, and partial discharge activity. It is particularly effective for assessing the overall condition of medium-voltage extruded dielectric cables and is often performed in conjunction with VLF testing.
Time Domain Reflectometry (TDR)
TDR testing sends a pulse down the cable and analyzes reflections to locate splices, terminations, and faults with precision. It is used to pinpoint the location of insulation failures, open circuits, and impedance discontinuities, reducing excavation and repair time significantly.
Partial Discharge (PD) Testing
Partial discharge testing detects localized electrical discharges within cable insulation that do not fully bridge the conductor gap. PD activity is an early indicator of insulation degradation and can identify defects in splices, terminations, and the cable body before they develop into full failures.
Cable Systems We Test
- Medium-voltage XLPE and EPR insulated cables (5 kV – 35 kV)
- Paper-insulated lead-covered (PILC) cables
- Low-voltage power and control cables
- Cable splices and terminations
- Underground distribution feeders
- Industrial plant cable systems