ABB Relion 670 Series Applications Manual page 399

1MRK 511 358-UUS A
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, 85) 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 scheme to operate when
the line fault blocks the signal transmission. Set the
14.4.3 Setting guidelines
The parameters for the scheme communication logic for residual overcurrent protection function
are set via the local HMI or PCM600.
The following settings can be done for the scheme communication logic for residual overcurrent
protection function:
Operation : Disabled or Enabled .
SchemeType : This parameter can be set to Off , Intertrip , Permissive UR , Permissive OR or
Blocking .
tCoord : Delay time for trip from ECPSCH (85) function. For Permissive under/overreaching
schemes, this timer shall be set to at least 20 ms plus maximum reset time of the communication
channel as a security margin. For Blocking scheme, the setting should be > maximum signal
transmission time +10 ms.
Unblock : Select Off if unblocking scheme with no alarm for loss of guard is used. Set to Restart if
unblocking scheme with alarm for loss of guard is used.
14.5 Current reversal and weak-end infeed logic for residual
overcurrent protection ECRWPSCH (85)
14.5.1 Identification
Function description
Current reversal and weak-end
infeed logic for residual overcurrent
protection
Application manual
tSecurity to 35 ms.
IEC 61850 IEC 60617
identification identification
ECRWPSCH -
Scheme communication
ANSI/IEEE C37.2
device number
85
Section 14
M13920-4 v6
IP14365-1 v4
M14883-1 v2
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