Omicron CP TD12 - Page 37

OMICRON 37
Power transformers
Dielectric measurements on a two-winding power transformer usually include all 3 insulations C
HL
, C
H
and C
L
. To measure C
HL
and C
H
, the HV output of the CP TD12/15 is connected to the HV-side and IN A
to the LV-side (see Figure 5-3 on page 37). To prevent induced currents, all bushings of the HV-side are
shortened, the same applies to the LV-side. The ground of the transformer and the ground of the
CP TD12/15 are connected.
Figure 5-3: CP TD12/15 connected to a two-winding transformer for the measurement of C
HL
and C
H
With this setup 3 configurations are available (see Table 5-1 below). C
HL
and C
H
can be measured
without reconnecting.
IN B is not connected, so the modes GSTg-A and GSTg-(A+B) give the same result as it makes no
difference whether the current over IN B is guarded or measured.
Table 5-1: Modes available with a measurement setup as seen in Figure 5-3
Mode IN A Ground Result
UST-A Measured Guarded C
HL
GSTg-A or GSTg-(A+B) Guarded Measured C
H
GSTg-B Measured Measured C
HL
+ C
H
LV
HV
C
HL
C
L
C
H
IN A
IN B
HV output
Measurement
ground