By hvhipot 
An AC voltage test equipment is a specialized device used to apply power-frequency (50Hz/60Hz) or variable-frequency AC high voltage to electrical equipment. Its core function is to simulate operational voltage stress, detect insulation defects (cracks, aging, contamination), and ensure safe operation.
I. Main Types
1.Power-Frequency Withstand Test Equipment
Components: High-voltage test transformer (steps up input voltage), voltage regulator, control unit, protective resistor, measurement system.
Output: Pure 50Hz/60Hz sine wave (up to 500kV).
Application: Factory testing of low-voltage devices, insulators, small transformers.
2.Variable-Frequency Series Resonant Test System
Principle: Adjusts frequency (30-300Hz) to achieve resonance between reactor (L) and test object capacitance (C), generating high voltage.
Advantages: Small input capacity (1/10 of traditional systems), lightweight, clean waveform. Ideal for on-site large equipment (cables, GIS).
Application: AC withstand tests for HV cables (22kV~500kV), generators, GIS.
3.Induced Voltage Test Equipment
Features: Outputs 100-400Hz to avoid transformer core saturation.
Use: Inter-turn/layer insulation testing for power transformers.
4.Partial Discharge (PD) Test System
Function: Detects internal PD signals (pC-level) under AC high voltage.
Components: HV series resonance, coupling capacitor, PD sensor, analyzer.