Section 6 Differential protection
6.1 Transformer differential protection
6.1.1 Functionality
Transformer differential protection, three-winding T3WPDIF is provided with
internal CT ratio matching and vector group compensation and settable zero sequence
current elimination.
The function can be provided with -phase sets of current inputs. All current inputs are
provided with percentage bias restraint features, making the IED suitable for two- or
three-winding transformer arrangements.
Three-winding applications
IEC05000052 V1 EN
three-winding power
transformer with all
three windings
connected
IEC05000049 V1 EN
three-winding power
transformer with
unconnected delta
tertiary winding
Figure 29: CT group arrangement
for differential
protection and other
protections
The setting facilities cover the application of the differential protection to all types of
power transformers and auto-transformers with or without load tap changer as well as
shunt reactors and local feeders within the station. An adaptive stabilizing feature is
included for heavy through-faults.
Stabilization is included for inrush and overexcitation currents respectively, cross-
blocking is also available. Adaptive stabilization is also included for system recovery
inrush and CT saturation during external faults. A high set unrestrained differential
current protection element is included for a very high speed tripping at a high internal
fault currents.
1MRK 502 048-UEN A Section 6
Differential protection
81
Technical manual
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