Omicron CP TD12 - Two-winding transformer insulation analysis

CP TD12/15 User Manual
36 OMICRON
5.3 Two-winding transformer
The two-winding transformer is a very good example to show the different parts of insulation which can
be measured in a transformer.
A two-winding transformer with high and low voltage windings provides three different insulations which
can be measured (see Figure 5-2 below): Insulation C
HL
between the high- and the low-voltage
windings, insulation C
H
between the high-voltage winding and ground and the insulation C
L
between the
low-voltage winding and ground.
Figure 5-2: Insulations of a two-winding transformer
In case of core type transformers, insulation C
HL
is made of barriers and spacers which give it
mechanical stability and enable oil flow to cool the windings. Compared to the other insulation parts,
insulation C
HL
contains the highest amount of paper.
Insulation C
H
, insulating the high-voltage windings from the tank, mainly consists of oil. The paper
influence usually mainly comes from parts of the clamping construction.
Insulation C
L
, insulating the low-voltage windings from the core, also consists of oil and paper but there
usually is much less paper present than in the C
HL
insulation.
LV
HV
C
HL
C
L
C
H