Differential Protection - ABB Relion 650 series RET650 Product Manual

ABB
Transformer protection RET650
Product version: 1.1

4. Differential protection

Transformer differential protection
T2WPDIF/T3WPDIF
The Transformer differential protection, two-
winding (T2WPDIF) and Transformer
differential protection, three-winding
(T3WPDIF) are provided with internal CT
ratio matching and vector group
compensation and settable, zero sequence
current elimination.
The function can be provided with two or
three-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.
Two-winding applications
two-winding
power
xx05000048.vsd
transformer
IEC05000048 V1 EN
Three-winding applications
three-winding
power
transformer with
all three
windings
connected
xx05000052.vsd
IEC05000052 V1 EN
three-winding
power
transformer with
xx05000049.vsd
unconnected
IEC05000049 V1 EN
delta tertiary
winding
Figure 4. CT group arrangement for
differential protection and
other protections
The setting facilities cover for applications of
the differential protection to all types of
power transformers and auto-transformers
with or without load tap changer as well as
for shunt reactors or and local feeders within
1MRK 504 127-BEN -
Issued: February 2011
the station. An adaptive stabilizing feature is
included for heavy through-faults.
Stabilization is included for inrush currents as
well as for overexcitation condition. Adaptive
stabilization is also included for system
recovery inrush and CT saturation for
external faults. A high set unrestrained
differential current protection is included for
a very high speed tripping at a high internal
fault currents.
An innovative sensitive differential protection
feature, based on the theory of symmetrical
components, offers the best possible
coverage for power transformer winding turn-
to-turn faults.
Restricted earth fault protection
REFPDIF
Restricted earth fault protection, low
impedance REFPDIF
Restricted earth-fault protection, low-
impedance function (REFPDIF) can be used
on all directly or low-impedance earthed
windings. The REFPDIF function can provide
higher sensitivity (down to 5%) and higher
speed as it measures each winding
individually and thus does not need inrush
stabilization.
The low-impedance function is a percentage
biased function with an additional zero
sequence current directional comparison
criterion. This gives excellent sensitivity and
stability for through faults. The function
allows use of different CT ratios and
magnetizing characteristics on the phase and
neutral CT cores and mixing with other
functions and protection IEDs on the same
cores.
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
turn ratio and similar magnetizing
characteristics. It utilizes an external
summation of the currents in the
interconnected CTs and a series resistor and a
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