3. Tests with High Alternating Voltages

HVAC test voltages represent the stress of insulations by operational alternating voltages (50 or 60 Hz) and temporary over-voltages. For that reason they are the most important test voltages and applied for all kinds of withstand tests, lifetime tests and dielectric or partial discharges (PD) measurements. After the detailed description of HVAC voltage generation, the requirements of HVAC test voltages and the interaction between test system and test object are investigated. Measuring systems for HVAC test voltages are mainly based on capacitive voltage dividers and peak voltmeters, but for measurements during HVAC tests with an expected voltage drop, with harmonics or fast voltage changes, digital recorders become more and more necessary. The chapter is closed with a section on procedures for HVAC breakdown and withstand tests, dry, wet as well as pollution tests, long duration or lifetime testing. Examples for HVAC tests on cables, gas-insulated switchgear, power and instrument transformers are given.