Setting parameter selected value for both Solution 1
(wye conected CT)
Selected value for both Solution 2
(delta connected CT)
LocationOLTC1 Not Used Not Used
Other parameters Not relevant for this application.
Use default value.
Not relevant for this application.
Use default value.
1)
To compensate for delta connected CTs.
2)
Zero-sequence current is already removed by connecting main CTs in delta.
Wye-wye connected power transformer with load tap changer and
tertiary not loaded delta winding
SEMOD167854-305 v2
Single line diagrams for two possible solutions for such type of power transformer with
all relevant application data are given in figure 56. It shall be noted that this example is
applicable for protection of autotransformer with not loaded tertiary delta winding as
well.
CT 500/5
Wye
31.5/31.5/(10.5) MVA
110±11×1.5% /36.75/(10.5) kV
YNyn0(d5)
CT 200/1
Wye
CT 500/5
in Delta
(DAB)
31.5/31.5/(10.5) MVA
110±11×1.5% /36.75/(10.5) kV
YNyn0(d5)
CT 200/1
in Delta
(DAB)
en06000558_ansi.vsd
ANSI06000558 V1 EN-US
Figure 56: Two differential protection solutions for wye-wye connected
transformer.
For this particular power transformer the 110 kV side phase-to-ground no-load voltages
are exactly in phase with the 36.75 kV side phase-to-ground no-load voltages. Thus,
when external phase angle shift compensation is done by connecting main CTs in delta,
both set of CTs must be identically connected (that is, either both DAC or both DAB as
1MRK 502 071-UUS A Section 7
Differential protection
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062 151
Application manual
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