High Voltage (HV) Cable Testing Procedure

High-voltage cables (typically 1kV and above) require rigorous testing to ensure insulation integrity, proper installation, and long-term reliability. Below is a comprehensive step-by-step testing procedure based on IEC 60502, IEEE 400, and IEC 60840 standards.

1. Safety Precautions

✔ De-energize and isolate cable
✔ Verify proper grounding
✔ Use appropriate PPE (gloves, arc flash suit)
✔ Maintain safe clearance distances

2. Visual Inspection

• Check for physical damage to insulation/sheath

• Verify proper cable termination and sealing

• Inspect for oil leaks (in fluid-filled cables)

• Confirm proper cable support and bending radius

3. Insulation Resistance Test (Megger Test)

Purpose: Verify insulation integrity
Test Voltage:

• 1-5kV cables: 2.5kV DC

• 6-35kV cables: 5kV DC

• 35kV cables: 10kV DC

Procedure:

1. Disconnect both ends of cable

2. Apply test voltage for 1 minute

3. Measure insulation resistance

Acceptance Criteria:

• New cables: >1000 MΩ/km

• Service-aged cables: >1 MΩ (minimum)

4. DC Hi-Pot Test (For New Cables)

Purpose: Verify insulation strength
Test Voltage:

• XLPE cables: 4 × U₀ (e.g., 22kV for 11kV cable)

• PILC cables: 3 × U₀

Procedure:

1. Apply DC voltage in steps (typically 25%, 50%, 75%, 100%)

2. Hold final voltage for 15 minutes

3. Monitor leakage current

Acceptance Criteria:

• No breakdown

• Leakage current stabilizes (<1 mA/km typical)

5. VLF (Very Low Frequency) Test (For Aged Cables)

Purpose: AC testing alternative (0.1Hz instead of 50/60Hz)
Test Voltage: 1.5-2 × U₀
Duration: 15-60 minutes

Advantages:

• Less damaging to aged insulation

• Better at detecting water trees in XLPE

6. Tan Delta (Dissipation Factor) Test

Purpose: Measure insulation aging
Test Method:

• Apply AC voltage (0.5-2 × U₀)

• Measure dielectric losses

Acceptance Criteria:

• New XLPE: <0.1%

• Aged XLPE: <1% (investigate if >2%)

7. Partial Discharge (PD) Test

Purpose: Detect insulation defects
Test Voltage: U₀ or higher
Acceptance Criteria:

• New cables: <10 pC

• Service-aged: <50 pC

8. Time Domain Reflectometry (TDR)

Purpose: Locate cable faults
Method:

• Send pulse through cable

• Analyze reflections to find faults

9. Sheath Integrity Test

Purpose: Check metallic sheath condition
Test Voltage: 1kV DC
Acceptance: >1 MΩ

10. Commissioning Tests

✔ Phase rotation verification
✔ Thermal imaging of terminations
✔ Final documentation review

Testing Frequency

Common Faults Detected

• Insulation degradation (via Tan Delta)

• Water trees (via VLF Tan Delta)

• Shield/Sheath damage (via Sheath Test)

• Termination faults (via Thermal Imaging)

• The above content is published by demiks, please specify, demiks is a substation equipment manufacturer, specializing in the production of high-voltage tester, transformer tester, circuit breaker test equipment, relay tester, SF6 gas analyser, cable fault tester and other products, if you have power test testing needs, please feel free to contact demiks power science and technology limited company or send an email! Give us: contact@demikspower.com