CPC 100 V1.41
6 - 18
TRTapCheck (for OLTC)
Use the TRTapCheck test card to measure the winding resistance of the
individual taps of a power transformer’s tap changer, and to check whether the
on-load tap changer (OLTC) switches without interruption.
CPC 100 injects a constant current from the 6A DC output into the power
transformer and the current is led via the IAC/DC input for measurement.
Alternatively, the current injected from the 400A DC output is measured
internally. From this current value and the voltage measured by the V DC input
(see Figure 12), the winding resistance is calculated.
In the moment the tap is changed, the IAC/DC measuring input detects the
sudden, very short drop of the current flow. A properly working tab change
differs from a malfunctioning one, for example, an interruption during the
change, by the magnitude of the ripple and slope values. An interruption will
result in much higher ripple and slope values than a properly functioning tab
change.
The ripple and slope values are indicated at the TRTapCheck test card’s
measurement table (refer to Figure 13).
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