Omicron Lab CT Analyzer, User Manual

Page: 35 / 254

33
Setup and Connection
Figure 2-10 Measurement on a bushing-type CT
Note: Primary terminal H1 must be open. Otherwise the primary side is shorted
and the CT Analyzer cannot obtain proper results.
Measurement on a Y (Wye) Winding Transformer
For measurements on current transformers in Y-connected transformer
windings it has to be assured that the main impedance of the transformer does
not influence the measurement results.
The CT Analyzer has an input impedance of approx. 330k Ω . This measurement
impedance can be low enough to influence the measurement results. In order to
prevent any influence of the
CT Analyzer 's input impedance to the measurement
results, the transformer winding at the same leg should be short-circuited. Short-
circuiting the windings on all legs of the transformer is even better.
Furthermore, all bushing terminals that are not connected to the CT Analyzer
should be connected to protective earth in order to prevent influence of external
disturbances (see Figure 2-11).
H0
(Mp)
(N)
H3
(C)
(W)
H2
(B)
(V)
H1
(A)
(U)
CT
Coax measurement cables