ABB REG670 Product Manual page 21

Generator protection REG670 2.2 and Injection equipment REX060,
REX061, REX062
Product version: 2.2.1
Two-winding applications
two-winding power
transformer
xx05000048.vsd
IEC05000048 V1 EN-US
two-winding power
transformer with
unconnected delta
xx05000049.vsd
tertiary winding
IEC05000049 V1 EN-US
two-winding power
transformer with two
circuit breakers and
xx05000050.vsd
two CT-sets on one
IEC05000050 V1 EN-US
side
two-winding power
transformer with two
circuit breakers and
two CT-sets on both
sides
xx05000051.vsd
IEC05000051 V1 EN-US
Three-winding applications
three-winding power
transformer with all
three windings
connected
xx05000052.vsd
IEC05000052 V1 EN-US
three-winding power
transformer with two
circuit breakers and
two CT-sets on one
side
xx05000053.vsd
IEC05000053 V1 EN-US
Autotransformer with
two circuit breakers
and two CT-sets on
two out of three sides
xx05000057.vsd
IEC05000057 V1 EN-US
Figure 4. CT group arrangement for
differential protection
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-fault
currents.By introducing the load tap changer position, the
differential protection pick-up can be set to optimum
ABB
sensitivity thus covering internal faults with low fault current
level.
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 high internal fault currents.
Included is an sensitive differential protection element based
on the theory of negative sequence current component. This
element offers the best possible coverage of power
transformer windings turn to turn faults.
High impedance differential protection, single phase HZPDIF
High impedance differential protection, single phase (HZPDIF)
functions can be used when the involved CT cores have the
same turns ratio and similar magnetizing characteristics. It
utilizes an external CT secondary current summation by
wiring. Actually all CT secondary circuits which are involved in
the differential scheme are connected in parallel. External
series resistor, and a voltage dependent resistor which are
both mounted externally to the IED, are also required.
The external resistor unit shall be ordered under IED
accessories in the Product Guide.
HZPDIF can be used to protect generator stator windings,
tee-feeders or busbars, reactors, motors, auto-transformers,
capacitor banks and so on. One such function block is used
for a high-impedance restricted earth fault protection. Three
such function blocks are used to form three-phase, phase-
segregated differential protection.
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 provides high
sensitivity and high speed tripping as it protects each winding
separately and thus does not need inrush stabilization.
The REFPDIF function is a percentage biased function with an
additional zero sequence current directional comparison
criterion. This gives excellent sensitivity and stability during
through faults.
REFPDIF can also protect autotransformers. Five currents are
measured at the most complicated configuration as shown in
Figure 5.
1MRK 502 074-BEN A
M13071-3 v13
M13047-3 v19
21