Alternating Current (AC) Hi-Pot Testing, is a test that is conducted on electrical equipment to determine its ability to withstand high voltage without breaking down. also known as Dielectric Withstanding Voltage (DWV) or High Voltage (HV) testing. One such equipment that requires this type of testing is a Switchgear Circuit Breaker, which is used to control and protect electrical power systems.
The routine AC overvoltage or hi-pot testing of medium voltage switchgear circuit breaker insulation systems is strongly recommended based on typical
failure modes, the inability of a lower voltage megger insulation test to always identify the problem area, the low cost for the test equipment, the low
cost to repair a failure, and finally and most important, the potential hazard to operating personnel who rack the breaker into the cubicle while standing
in front of it, which energizes approximately one-half of the breaker. AC testing is preferred over direct current (DC) because of the equipment's physical geometries
. Switchgear circuit breakers have very little capacitance and, consequently, AC hi-pot sets can be very small in size and capacity and relatively inexpensive. Insulation failures are usually the result of surface tracking; thus they can be repaired easily. Because the consequence of a test failure is relatively minor, electricians can perform the testing when they overhaul the breaker. By comparison, the DC hi-pot testing of medium voltage motors and medium to large generators is normally performed by highly trained engineers or technicians and often witnessed by a supervisor or engineer because of the high cost of failure.
Wuhan Huayi Electric power company provides different models and types of AC hi-pot test equipment, which can meet all kinds of test requirements for switchgear circuit breaker. The common type is using a test transformer and voltage controller, which is cheaper and durable.