Hipot (high potential) testing is a critical procedure used to verify the insulation integrity of electrical components and products. Whether you’re dealing with cables, industrial equipment, or consumer electronics, this dielectric withstand test ensures safety and compliance by detecting insulation breakdowns.
What is Hipot Testing?
Definition
Hipot testing, short for “high potential testing,” is a high-voltage test that verifies whether the insulation of an electrical device can withstand operating and surge voltages without allowing current to flow to ground or between components. It is often referred to as:
- Dielectric Withstand Test
- Overvoltage Test
- Dielectric Strength Test
Standards Perspective
Depending on the standard you’re using (e.g., IEC, UL, IEEE), the definition may vary slightly:
- Test between live parts and grounded accessible metal
- Test between primary circuits and protective earth
But all standards agree: the test aims to ensure user safety by confirming the effectiveness of insulation.
Hipot Test Equipment Components
A complete Hipot test setup may include:
- Hipot tester with AC or DC output
- Voltage ramp control (manual or auto)
- Current/leakage detection meter
- High-voltage leads for connection to line and neutral
- Ground lead for connecting chassis or return path
- Adapter boxes for products with standard line cords
Optional features:
- Ground continuity check
- Slow ramp mode for sensitive components
- Fail-safe auto shutdown
How to Perform Hipot Testing: Step-by-Step
1. Prepare the Device Under Test (DUT)
- Disconnect the DUT from the power source.
- Identify accessible conductive parts and ground points.
- Short-circuit line and neutral if applicable.
2. Connect the Hipot Tester
- Connect the high-voltage terminal to the shorted line and neutral.
- Connect the return/ground terminal to the chassis or exposed metal parts.
3. Start the Test
- Set the appropriate voltage based on product rating and standard.
- Ramp voltage gradually (manual or auto ramp).
- Monitor current flow.
- Hold the test voltage for 1 to 60 seconds, depending on application.
4. Evaluate the Results
- Pass: Current leakage remains within acceptable limits (typically <1 mA).
- Fail: Breakdown occurs (usually >20 mA current) or insulation arc detected.
5. Post-Test Safety
- Discharge residual voltage.
- Remove test leads.
- Document test results.
Real-World Testing Examples
Industrial Heating Element
- Hipot applied at 2 kV AC.
- Leakage: ~627 µA (normal due to capacitive reactance).
- No breakdown = PASS.
LED Lamp with Line Cord
- Connected via adapter box.
- Ground continuity confirmed (resistance < 1 Ω).
- Leakage: ~589 µA.
- No breakdown = PASS.
Arcing Demo with Spheres
- Visualizes insulation breakdown using air gap.
- Failure occurred at ~2200 V with >20 mA current.
- Shows what a dielectric failure looks like.
How to Calculate Hipot Test Voltage
AC Hipot
Use 1.414 × RMS value of rated voltage.
DC Hipot
Use: DC Test Voltage = 1.414 × (2 × rated voltage + 1000 V) Or per IEEE: 0.65 × (3.4 × rated voltage + 1700 V)
Always consult standards for exact voltage/time combinations.
Tips for Safe and Reliable Hipot Testing
- Use clear labels and signs during testing.
- Train personnel on proper connection techniques.
- Never touch the DUT during a high-voltage test.
- Monitor both voltage and leakage current.
- Use safety interlocks and emergency stop if available.
Conclusion
Hipot testing is essential for electrical safety and compliance. Whether you’re verifying a cable spool or testing a consumer device, understanding the principles behind the test helps ensure that your products are safe and reliable. By following a systematic approach and using the right equipment, you can confidently perform this critical quality control measure.