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.
14.4.3 Setting guidelines
M13920-4 v6
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
.
tCoord
: Delay time for trip from ECPSCH 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
IP14365-1 v4
14.5.1 Identification
M14883-1 v2
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Current reversal and weak-end
infeed logic for residual overcurrent
protection
ECRWPSCH - 85
Section 14 1MRK 511 358-UEN A
Scheme communication
352
Application manual
To Next Page
Loading...
