Vacuum Breaker, Switchgear Testing, ISO Phase Bus
Within a substation, there are many types of apparatus that require high voltage testing. Tests include withstand/proof testing, insulation resistance (IR) measurement, hipot leakage current testing, partial discharge, and tan delta, among others. Some tests require AC voltage, some require DC, and some can use either. Most HV testing of electrical substation apparatus is done with AC voltage, although many use DC since the hipots are smaller, lighter, and less expensive than AC. AC is the preferred technical method since most of the tests performed are overvoltage withstand tests. Switchgear, reclosers, vacuum bottles, etc. are tested to make sure they hold the overvoltage. DC leakage current readings tell little about the integrity of the equipment under normal AC operating conditions. Users should check the maintenance manuals of their gear and refer to the pertinent IEEE/ANSI/etc. standards for the recommended testing methods.
Testing iso-phase bus (IPB) or the bus work within switchgear cabinets, often many in parallel, is normally an AC withstand test where the test voltage is applied from bus to ground and held for 60 seconds. The insulators holding the bus off of ground are either good or defective. If the test voltage holds for 60 seconds with no arcing, the bus duct and its insulators are deemed good. IEEE and other standards exist that define the test voltages required, and the maintenance manuals from product vendors list the test voltages based on the nameplate voltage rating of the gear. AC field tests after installation and during service are usually performed at 75% of the factory test voltage.
High Voltage, Inc. manufacturers a complete line of AC and DC hipots for testing substation electrical apparatus and iso-phase bus. One of our most popular units for vacuum interrupters within switchgear or reclosers is the PFT-503CM(F), a 50 kV at 3 kVA 1-piece AC hipot with an integrated output cable. HVI offers outstanding after-sales service, support, and application knowledge to ensure customers select and deploy the right equipment in the field or in factories.