Voltech AT5600 User Manual page 152

C H A P T E R 7 – T E S T S
Best Practice for multiple winding or large transformers.
After any HPAC, HPDC or IR test, the unit will turn off the sources, and switch in
an internal discharge resistor to remove any latent voltages on any windings used
in the test.
Any voltage present is monitored until it has decayed, then the relays opened
ready for the next test. This is defined in 9.2.3 "Voltage Present Error."
On large transformers where one winding (or a screen or core connection) are not
used in the high voltage test, then these are left floating with respect to ground.
As the controlled discharge only applies to nodes used in the test, these unused
nodes could be left in a dangerous state, especially if the UUT is large or highly
capacitive.
Hence it is always best practice to use ALL available nodes in a high pot test.
Typically, by selecting the winding to test as HI, and all others to LO.
This ensures that the whole transformer is electrically controlled during the test,
and fully discharged after. This prevents hot switching of the relays in the AT
which can potentially cause damage on the subsequent tests if floating voltages
are left.
Please also see
AT dotNET Editor manual (98-125 2.5.27) for specific advice on programming the
test
10.2.12 for test accuracy specification
.
AT5600 User Manual 98-119 issue 30
A N D T E S T C O N D I T I O N S
Page 152