Basler BE1-CDS220, Instruction Manual

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3-4 Input And Output Functions BE1-CDS220
Sidebar 3-1. Determining the Transformer Connection Parameters
Wye and Autotransformer Windings. The transformer connection for a CT input circuit that is
connected to either a wye or autotransformer winding should be classified as a wye winding.
Delta Transformer Windings. The transformer connection for a CT input circuit that is connected to a
delta winding could be classified as one of two delta connections: Delta IA-IB (DAB), or Delta IA-IC
(DAC). A delta configuration is defined by the currents that flow in the primary phases connected to
the delta. The wye-winding phase connections are used as the point of reference since the current
that flows in the wye winding is the same as the current in the wye side primary phases. Figure 3-3
(left) shows an example of a transformer with a DAB connection. Figure 3-3 (right) shows an example
of the same transformer with the phases reconnected to provide a DAC connection. If there is no wye
winding to use as reference, as is the case with a delta/delta transformer, the definition of the delta
configuration is not important.
B
C
A
b
c
a
D2837-22.vsd
12-22-98
IA=Ia-Ic
IB=Ib-Ia
IA=Ic-Ib
B
A
C
b
a
c
D2837-21.vsd
12-21-98
IC=Ic-Ia
IB=Ib-Ic
IA=Ia-Ib
Figure 3-3. DAB Delta (left) and DAC Delta (right)
With the appropriate CT and transformer connection information, the relay can automatically determine
the correct compensation required. Table 3-2 provides a listing of all acceptable combinations of CT and
transformer connection settings and the compensation that the BE1-CDS220 will apply. The
recommended settings for each configuration are highlighted in Bold. Figure 3-3 provides details on how
to choose the correct CT and transformer connections to describe the application. If a combination of
connection settings is entered that results in an invalid condition, the relay will give an error message
when the settings are validated on Exit/Save Yes.