7
Installation
UST and GST Standard Measuring Circuits
Capacitance and tan delta (power factor) can be measured on ungrounded test objects (UST) or
grounded test objects (GST). The common procedure in the HV laboratory is to measure as
ungrounded test object. Complete information about both test circuits and when to use them is
included in the instrument manual.
Only when test object is physically connected to ground and is not possible to disconnect, the GST
mode should be selected, for all the rest the UST mode should be used.
UST Mode
Test Object ungrounded – Power splay to ground
GST Mode – V and Ground separated
Test Object Grounded – Power supply to V
Figure 3-5 UST and GST modes
The selection between modes is done with the manual bridge in the instrument back panel.
UST Mode Selected
V and Ground Connected
GST Mode selected
V and Ground Isolated
Figure 3-6 UST and GST Selection in the 2823
Electrical connection between the V(supply) point from the back of the 2823 and the
low voltage point of the high voltage power supply is required. Missing this
connection can end in instrument damages.
