ABB RET670 Product Manual page 10

Transformer protection RET670
Customized
Product version: 1.2
Two-winding applications
two-winding power
transformer
xx05000048.vsd
IEC05000048 V1 EN
two-winding power
transformer with
unconnected delta
xx05000049.vsd
tertiary winding
IEC05000049 V1 EN
two-winding power
transformer with two
circuit breakers on
xx05000050.vsd
one side
IEC05000050 V1 EN
two-winding power
transformer with two
circuit breakers and
two CT-sets on both
sides
xx05000051.vsd
IEC05000051 V1 EN
Three-winding applications
three-winding power
transformer with all
three windings
connected
xx05000052.vsd
IEC05000052 V1 EN
10
1MRK 504 117-BEN D
three-winding power
transformer with two
circuit breakers and
two CT-sets on one
side
xx05000053.vsd
IEC05000053 V1 EN
Autotransformer with
two circuit breakers
and two CT-sets on
two out of three sides
xx05000057.vsd
IEC05000057 V1 EN
Figure 1. 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.By introducing the load tap
changer position, the differential protection pick-
up can be set to optimum sensitivity thus
covering internal faults with low fault level.
Stabilization is included for inrush and
overexcitation currents respectively. 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.
Included is an innovative sensitive differential
protection element based on the theory of
symmetrical components. This element offers the
best possible coverage of power transformer
windings turn to turn faults.
1Ph High impedance differential protection
HZPDIF
The 1Ph High impedance differential protection
(HZPDIF) function can be used when the involved
CT cores have the same turns ratio and similar
magnetizing characteristics. It utilizes an external
CT current summation by wiring, a series resistor,
ABB