| Frequency Range |
Typically 0.1 Hz – 0.01 Hz (ultra-low frequency) |
Power frequency (50/60 Hz) or intermediate frequency (up to several kHz) |
| Core Principle |
Uses sinusoidal or square-wave voltage at ultra-low frequency to simulate long-term electrical stress on insulation; detects defects such as voids, cracks, or moisture |
Applies high AC voltage (higher than rated voltage) for a short duration to verify insulation withstand capacity; focuses on "breakdown prevention" |
| Primary Application |
Large capacitive loads: Power cables (XLPE, EPR), transformers, capacitors, and high-capacitance electrical equipment |
General electrical equipment: Motors, generators, switchgear, circuit breakers, and low-capacitance components |
| Equipment Characteristics |
Low output current, high voltage capability, compact size, and low power consumption (suitable for on-site testing) |
High output current, moderate voltage range (typically up to 100 kV), larger size, and higher power consumption (mostly laboratory/workshop use) |
| Testing Duration |
Long duration: 15 – 60 minutes (simulates long-term insulation aging) |
Short duration: 1 – 5 minutes (quick verification of insulation integrity) |
| Insulation Impact |
Minimal damage: Low frequency reduces dielectric heating, suitable for fragile or aged insulation |
Moderate damage risk: Higher frequency may cause dielectric loss and heating, not ideal for sensitive insulation |
| Defect Detection Capability |
Strong at identifying hidden, long-term defects (e.g., gradual insulation degradation, moisture penetration) |
Superior at detecting obvious, critical defects (e.g., severe cracks, insulation breakdown risks) |
| Cost & Portability |
Higher cost, high portability (lightweight, easy to transport for on-site work) |
Lower cost, poor portability (heavy, requires fixed installation) |
