The VLF hipot test method and AC resonant test are essential and common test methods for maintenance, safety, and performance of power equipment. We can learn the difference between them through below points.
1. Test principle and Test frequency.
VLF hipot test Frequency: 0.1Hz (or 0.02- 1Hz), analog power frequency, but very long period.
VLF hipot test Principle: Detect dielectric loss and partial discharge by applying ultra-low frequency voltage, suitable for medium and low voltage cables (≤35 kV)
AC resonant test Frequency: 30-300 Hz (close to power frequency 50/60 Hz).
AC resonant test Principle: The reactor is used to compensate the capacitive reactance of the cable, generate high voltage resonance, and achieve high voltage test of large capacity cables (≥110 kV).
2. Application scenario comparison
|
|
VLF hipot test |
AC resonant test |
|
Type of cable |
≤35 kV) |
≥110 kV |
|
Test purpose |
Insulation defect detection, aging evaluation |
Handover test, compressive strength verification |
|
Portable |
≤80 kg |
≥500 kg |
|
standard |
IEEE 400.2,IEC 60502 |
IEC 60840,GB/T 3048.8 |
3. Selection suggestion
Preferred VLF:
Cable inspection, rush repair, or space-limited scenarios below 35 kV.
Preferred resonance:
High voltage cable factory test, GIS terminal connection test.