Preliminary
9.2 UST Ungrounded Specimen Test
The UST configuration is used for measurements between two terminals of a test specimen that
are not grounded or that can be removed from ground. In the UST configuration, current flowing in
the insulation between the voltage lead and the measuring lead of the instrument is measured and
current flowing to ground is not measured.
The below statements are to be taken as an example for transformers, a lot of different objects,
such as CTs, PTs, switch gear, insulators, capacitors, bushings, motors or generators can be
measured.
In the example below you measure the capacitance and dissipation factor between high-voltage
winding (HV) and low-voltage winding (LV), C = C
HL
.
Measurement of capacitance between high-voltage winding (HV) and low-voltage winding (LV),
insulated from ground.
In the case of two low-voltage windings, either the individual capacitances or their sum can be
measured via inputs A and B by setting the selector switch accordingly.
90315-1.2 Instruction Manual CAPO
Page 74 of 117
UST A