Hi Pot Test
Is Hi-Pot destructive?
Not inherently; IEEE classifies DC Hi-Pot as a 'Type 1 Destructive Withstand Test' only when applied at levels that degrade insulation. Below specific thresholds, it is safe for repeated testing.
How is leakage current threshold determined?
For production lines, leakage is typically 5–30 mA; for type tests, up to 100 mA. Failure occurs if current exceeds the configured threshold or arcing is detected.
What is the difference between Hi-Pot and Continuity Test?
Hi-Pot verifies no current flow (good isolation) at high voltage; Continuity verifies easy current flow between points at low voltage.
A Hi-Pot Test (High Potential Test), also known as a Dielectric Withstand Test, applies a voltage significantly higher than the equipment's rated operating voltage across its insulation system to verify dielectric strength and ensure no current flows between insulated points or to ground. It measures leakage current (typically in microamperes to milliamperes) to confirm the insulation can withstand over-voltage transients without breakdown.
On the shop floor, Hi-Pot testing is used for new equipment validation, such as motors, cables, PCBs, and EV traction systems, to certify safety compliance with UL and IEC standards. In routine maintenance, it is performed on rotating electric machines and older PILC cables to test ground conditions of insulation, with test voltage calculated as 1.7 × (2E + 1000) V for DC or (2 × Rated Voltage) + 1000 V for AC. Results are logged in CMMS systems like ServiceGrid as a preventive maintenance task with pass/fail thresholds for leakage current, triggering alerts if insulation degradation is detected.
Hidden Defects in Extruded Dielectric Cables: DC Hi-Pot may fail to locate defects in modern extruded cables while unknowingly triggering failure mechanisms that cause subsequent in-service failures.
Insulation Degradation from Over-Stressing: Repeated Hi-Pot tests at excessive voltage levels physically stress the insulation structure, reducing lifetime and causing premature breakdown.
Arcing/High Leakage Current: Failure occurs if absent spacers, damaged wires, or moisture allow current to bridge gaps between electronics and casing, leading to immediate arcing or shock hazards.