ABB REL670 2.2 IEC, Applications Manual

Page: 291 / 908

8.7 Mho impedance supervision logic ZSMGAPC
SEMOD153841-1 v3
8.7.1 Identification
GUID-030C086A-8301-481E-BA0A-6550A9C1482E v2
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Mho Impedance supervision logic ZSMGAPC - -
8.7.2 Application
SEMOD154555-4 v3
The Mho impedance supervision logic (ZSMGAPC) includes features for fault
inception detection and high SIR detection. It also includes the functionality for
loss of potential logic as well as for the pilot channel blocking scheme.
One part of ZSMGAPC function identifies a loss of phase potential that is the
result of a long term (steady state) condition such as a blown fuse or an open
voltage transformer winding or connection. This will block all trips by the distance
protection since they are based on voltage measurement.
In the pilot channel blocking scheme a fault inception detected by a fast acting
change detector is used to send a block signal to the remote end in order to block
an overreaching zone. If the fault is later detected as a forward fault the earlier sent
blocking signal is stopped.
The blocking scheme is very dependable because it will operate for faults
anywhere on the protected line if the communication channel is out of service.
Conversely, it is less secure than permissive schemes because it will trip for
external faults within the reach of the tripping function if the communication
channel is out of service. Inadequate speed or dependability can cause spurious
tripping for external faults. Inadequate security can cause delayed tripping for
internal faults.
ZSMGAPC function also includes functionality for blocking the sample based
distance protection due to high SIR. SIR directly influences the fault voltage level
for a given voltage level, and this is the major factor that affects the severity of
CVT transients. Therefore, in cases where the SIR value is too high, further
filtering of the measured signals will be needed.
8.7.3 Setting guidelines
SEMOD174968-1 v1
SEMOD154558-7 v4
GlobalBaseSel : Selects the global base value group used by the function to define
IBase , UBase and SBase as applicable.
PilotMode : Set PilotMode to On when pilot scheme is to be used. In this mode
fault inception function will send a block signal to remote end to block the
overreaching zones, when operated.
1MRK 506 369-UEN B
Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 285
Application manual