Setting Guidelines - ABB REC670 Applications Manual

Section 15
Scheme communication
15.4.3
446
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 scheme to
operate when the line fault blocks the signal transmission. Set the tSecurity to 35
ms.

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: Off or On.
SchemeType: This parameter can be set to Off , Intertrip, Permissive UR,
Permissive OR or Blocking.
1MRK 511 401-UEN A
M13920-4 v7
Bay control REC670 2.2 IEC
Application manual