Omicron CT SB2 User Manual page 40

CT Analyzer User Manual
Measurement on a Δ (delta) winding transformer
CTs outside the delta winding
For CTs that are located in the bushing outside of the delta winding (Figure 3-12), no delta compensation
is needed.
In this case, only two parallel transformer windings are connected in series to the CT. This connection
method provides least possible influence to the measurement result for the winding resistance of the CT.
The Y winding and the remaining windings of the power transformer's delta winding are short-circuited
to avoid influence of the induced flux of the power transformer's core to the measurement.
Figure 3-12: Bushing-type CT outside the delta winding power transformer
CTs inside the delta winding
For CTs that are integrated in the delta winding of the transformer, it is not possible to read the CT ratio
directly since the delta winding acts as a voltage divider. In order to obtain the correct CT ratio, the ratio
value determined by CT Analyzer has to be corrected.
38 OMICRON