Hitachi 670 Series Application Manual page 36

Section 4
Analog and binary signal transfer for line differential protection
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IEC04000209 V2 EN-US
Figure 27:
An alternative with two two-winding transformers in the protected zone is shown in Figure 28.
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IEC04000210 V2 EN-US
Figure 28:
An alternative with one three-winding transformer in the protected zone is shown in Figure 29.
Observe that in this case, the three-winding power transformer is seen by the differential protection
as two separate power transformers, A and B, which have one common winding on the HV side.
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IEC04000211 V2 EN-US
Figure 29:
30
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One two–winding transformer in the protected zone
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Two two–winding transformers in the protected zone
A
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One three–winding transformer in the protected zone
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Protected zone
Protected zone
A B
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Protected zone
B
1MRK505382-UEN Rev. K
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IEC04000209-2-en.vsdx
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IEC04000210-2-en.vsdx
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IEC04000211-2-en.vsdx
Communication set-up, 670/650 series
Application Guide