ABB Relion 670 Series Product Manual page 21

Line differential protection RED670 2.0
Product version: 2.0
power transformers and cables. Under the condition that there
are no in-line or tap (shunt) power transformers within the zone
of protection, it offers a phase-segregated fundamental
frequency current based differential protection with high
sensitivity and provides phase selection information for single-
pole tripping.
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IEC05000039 V3 EN
Figure 6. Example of application on a conventional two-terminal line
The six-terminal versions are used for conventional two-
terminal lines with 1½ circuit breaker arrangements in both
ends, as well as multi-terminal lines with up to five terminals.
IED
Comm. Channel
IEC05000040 V2 EN
Figure 7. Example of application on a three-terminal line with 1½ breaker arrangements
The current differential algorithm provides high sensitivity for
internal faults and it has excellent stability for external faults.
Current samples from all CTs are exchanged between the IEDs
in the line ends (master-master mode) or sent to one IED
(master-slave mode) for evaluation.
A restrained dual biased slope evaluation is made where the
bias current is the highest phase current in any line end, giving a
secure through-fault stability even with heavily saturated CTs.
In addition to the restrained evaluation, an unrestrained
(instantaneous) high differential current setting can be used for
fast tripping of internal faults with very high currents.
A special feature with this function is that applications with
small power transformers (rated current less than 50% of the
Line differential protection 3 or 6 CT sets, with in-zone
transformers LT3CPDIF, LT6CPDIF
Two two-winding power transformers or one three-winding
power transformer can be included in the line differential
protection zone. Both two- and three-winding transformers are
ABB
Protected zone
Communication channel
Protected zone
Comm. Channel
Comm. Channel
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The three-terminal version is used for conventional two-terminal
lines with or without a 1½ circuit breaker arrangement in one
end, as well as three-terminal lines with single breaker
arrangements at all terminals.
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IEC05000039-3-en.vsd
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IEC05000040_2_en.vsd
differential current setting
as shunt power transformers), without measurements of
currents in the tap, can be handled. The normal load current is
considered to be negligible, and special measures must be
taken in the event of a short circuit on the LV side of the
transformer. In this application, the tripping of the differential
protection can be time-delayed for low differential currents to
achieve coordination with downstream overcurrent IEDs. The
local protection of the small tap power transformer is given the
time needed to disconnect the faulty transformer.
A line charging current compensation provides increased
sensitivity of line differential protection.
correctly represented with vector group compensations made
in the algorithm. The function includes 2
restraint and zero-sequence current elimination. The phase-
segregated differential protection with single-pole tripping is
usually not possible in such applications.
1MRK505310-BEN C
IdMin ) connected as line taps (that is,
nd th
and 5 harmonic
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