ABB Relion 670 Series Applications Manual page 451

1MRK 511 401-UEN Rev. K
The setting of the minimum current detector,
unsymmetrical current that might flow on the non faulty line, when the breaker at remote end
has opened. At the same time it should be set below the minimum load current transfer during
normal operations that the line can be subjected to. By default,
The pick-up timer
value used to release the function. The timer is by default set to 200 ms, which is judged to be
enough to avoid unwanted release of the function (avoid unwanted trip).
16.4 Scheme communication logic for residual overcurrent
protection ECPSCH
16.4.1 Identification
Function description
Scheme communication logic for
residual overcurrent protection
16.4.2 Application
To achieve fast fault clearance of earth faults on the part of the line not covered by the
instantaneous step of the residual overcurrent protection, the directional residual overcurrent
protection can be supported with a logic that uses communication channels.
One communication channel is used in each direction, which can transmit an on/off signal if
required. The performance and security of this function is directly related to the transmission
channel speed and security against false or lost signals.
In the directional scheme, information of the fault current direction must be transmitted to
the other line end.
With directional comparison in permissive schemes, a short operate time of the protection
including a channel transmission time, can be achieved. This short operate time enables rapid
autoreclosing function after the fault clearance.
During a single-phase reclosing cycle, the autoreclosing device must block the directional
comparison earth-fault communication scheme.
The communication logic module enables blocking as well as permissive under/overreaching
schemes. The logic can also be supported by additional logic for weak-end infeed and current
reversal, included in the Current reversal and weak-end infeed logic for residual overcurrent
protection (ECRWPSCH) function.
Metallic communication paths adversely affected by fault generated noise may not be suitable
for conventional permissive schemes that rely on signal transmitted during a protected line
fault. With power line carrier, for example, the communication signal may be attenuated by the
fault, especially when the fault is close to the line end, thereby disabling the communication
channel.
To overcome the lower dependability in permissive schemes, an unblocking function can be
used. Use this function at older, less reliable, power line carrier (PLC) communication, where
the signal has to be sent through the primary fault. The unblocking function uses a guard
signal CRG, which must always be present, even when no CR signal is received. The absence of
the CRG signal during the security time is used as a CR signal. This also enables a permissive
Bay control REC670
Application manual
tLowCurr determine the window needed for pick-up of the minimum current
IEC 61850
identification
ECPSCH
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MinCurr , should be set higher than the
MinCurr is set to 5% of IBase .
IEC 60617 ANSI/IEEE C37.2
identification device number
- 85
Section 16
Scheme communication
IP14711-1 v2
M14882-1 v2
M13919-3 v6
445