Omicron CP TD1, Reference Manual

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CP TD1 Reference Manual V 1.44
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In addition to the previous table , it should be taken into account that overheating
is often caused by bad contacts in the tap selector. In order to find out the reason
for high gas values, further tests have to be performed on the transformer.
Common test methods are:
• Winding resistance measurement
• O n- L oad T ap C hanger (OLTC) test
• Turns ratio measurement
• Excitation current measurement
• Measurement of leakage reactance
• Capacitance and Dissipation factor measurement
All the mentioned tests can be done with the CPC 100 + CP TD1 . This
instrument is the ideal test and analysis instrument for transformer diagnosis
with these measuring possibilities.
6.2 Capacitance and DF Measurement of Transformer
Windings
General
• The transformer must be taken out of service and completely isolated
from the power system.
• The proper grounding of the transformer tank has to be checked.
• The bushing high-voltage terminals must be isolated from the connection
lines.
• All bushing terminals of one winding group, which means A, B, C (and
Neutral) of high-voltage winding, A, B, C (and Neutral) of low-voltage