1. Purpose of Leakage Test of High Voltage Tester

• Measures insulation resistance (IR) between plates

• Detects dielectric breakdown or contamination

• Verifies capacitor health in:

• Power factor correction banks

• HVDC systems

• Pulse power applications

2. Key Standards

3. Test Methods

A) Insulation Resistance (IR) Test

Equipment:

• 5kV/10kV Megohmmeter (e.g., Megger MIT515)

Procedure:

1. Discharge capacitor fully (critical safety step!)

2. Apply DC test voltage (typically 1kV per μF, max 10kV)

3. Measure leakage current after 1 minute

4. Calculate IR:

   $$\mathrm{<span\; style="font-size:\; 18px;">I</span>}\mathrm{<span\; style="font-size:\; 18px;">R</span>}<span\; style="font-size:\; 18px;">=</span>\frac{\text{<span style="font-size: 18px;">Test Voltage</span>}}{\text{<span style="font-size: 18px;">Leakage Current</span>}}$$IR=Leakage CurrentTest Voltage

Acceptance Criteria:

B) Self-Discharge Test

1. Charge to rated DC voltage

2. Disconnect power

3. Measure voltage decay over time

• Healthy cap: <10% drop in 10 mins

• Faulty cap: Rapid voltage collapse

C) Tan Delta (Dissipation Factor) Test

• Uses LCR meter or HV bridge

• Measures dielectric losses at operating frequency

• Warning threshold: DF >0.5% for film capacitors

4. Recommended Testers

5. Step-by-Step Testing Procedure

1. Safety First

• Verify capacitor is discharged (use grounding stick)

• Wear HV-rated gloves (>Class 00)

2. Connection

• Connect HV lead to capacitor terminal

• Ground case/frame (for wet capacitors)

3. Ramp Voltage

• Increase voltage at 500V/sec to avoid surges

4. Leakage Measurement

• Record current at 80% of rated voltage

• Stabilization time: 60 sec

5. Discharge

• Use bleeder resistor (10kΩ/kV)

6. Interpretation of Results

Failure Modes Detected:

• Electrolyte drying (in electrolytics)

• Partial discharge (in film caps)

• Internal shorts

7. Special Cases

A) AC Capacitors

• Test at 2 × rated Vrms for 60 sec

• Max leakage: 0.1 mA per μF

B) Pulse Capacitors

• Requires dV/dt testing

• Check IR before/after pulse cycling

8. Safety Protocol

✔ Double discharge (initial + verify with voltmeter)
✔ Barricade work area during HV testing
✔ Two-person rule for >5kV tests

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