Omicron CP TD1 - Measuring Three-Winding Transformer Insulations

OMICRON 47
Power transformers
When the CP TD1’s HV output is connected to the LV winding and IN A and IN B to HV and tertiary, the
capacitances C
HL
, C
HT
and C
L
can be measured without reconnection (see Figure 5-9 and Tables 5-4
and 5-5 below).
Figure 5-9: CP TD1 connected to a three-winding transformer for the measurement of C
HL
, C
LT
and C
L
With this setup the following 3 configurations are available:
Additionally, combinations of the different inputs are possible but as it is usually preferred to assess each
part of the insulation individually, they are less commonly used:
Table 5-4: Modes available with a measurement setup as seen in Figure 5-9
Mode IN A IN B Ground Result
UST-A Measured Guarded Guarded C
HL
UST-B Guarded Measured Guarded C
LT
GSTg-(A+B) Guarded Guarded Measured C
L
Table 5-5: Additional configurations available with a measurement setup as seen in Figure 5-9 if the
inputs are combined differently
Mode IN A IN B Ground Result
GSTg-(B) Measured Guarded Measured
C
L
+ C
HL
GSTg-(A) Guarded Measured Measured
C
L
+ C
LT
GST Measured Measured Measured
C
L
+ C
LT
+ C
HL
UST-(A+B) Measured Measured Guarded
C
HL
+ C
LT
CP TD 1
LVHV
C
HL
C
L
C
H
C
LT
C
T
C
HT
TV
IN A
IN B
HV output