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ABB Power Grids Ltd.
10.2
Capacitance C
First de-energize the transformer, then take the test tap cover off and connect the measuring equipment to
it using the test adapter, while the test power source is connected to the terminate plate of the bushing.
Tgδ
value changes in accordance with the temperature of the bushing's body and, consequently, the
1
measured value must be divided by a correction factor given in the table 3 and a curve at the figure 3. In
this case it is presupposed that the mean temperature of the bushing body is calculated according to the
formula:
2
Ta
To
T
3
where:
T is the mean temperature of the bushing body;
Ta is the temperature of the surrounding air;
To is the temperature of the oil inside the transformer.
The result is corrected to the temperature of 20
Table 3
Body temperature,
Correction factor for dielectric dissipation factor tgδ of RIP
11
and tgδ
measurements
1
1
0
C
10
20
30
40
50
60
70
80
RIP body temperature (°C)
0
C .
Correction factor for 20
Figure 3
GKSL 680205.021 RE
Rev. 2, 26.09.2019
0
C
1.20
1.00
0.85
0.77
0.75
0.75
0.82
0.90
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