Protection Functions - ABB RED615 Product Manual

Line Differential Protection and Control
RED615
Product version: 1.1
continued
Measurement
Transient disturbance recorder
Three-phase current measurement
Current sequence components
Differential current measurement
Bias current measurement
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= Included
3. Protection functions
The IED offers two-stage phase-segregated
line differential protection, phase overcurrent
protection, negative phase-sequence overcur-
rent protection and circuit-breaker failure
protection.
The line differential protection function
includes a stabilized low stage and an in-
stantaneous high stage. The stabilized low
stage provides a fast clearance of faults while
remaining stable with high currents passing
Fig. 1 Protection function overview of standard configuration A

through the protected zone increasing errors
on current measuring. Second harmonic re-
straint prevents the low stage from operating
due to the differential current caused by the
energization of the power transformer. The
high stage provides a very fast clearance of
severe faults with a high differential current
regardless of their harmonics.
The operating time characteristic for the
low stage can be selected to be either defi-
nite time or inverse definite time. The direct
inter-trip function ensures that both ends are
always tripped, independent of the fault cur-
rent contribution.
1MRS756500 A
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ABB