6.7 Mho impedance supervision logic ZSMGAPC
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Mho Impedance supervision logic ZSMGAPC - -
6.7.1 Introduction
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.
ZSMGAPC can mainly be decomposed in two different parts:
1. A fault inception detection logic
2. High SIR detection logic
6.7.2 Principle of operation
6.7.2.1 Fault inception detection
The aim for the fault inception detector is to detect quickly that a fault has occurred on
the system.
The fault inception detection detects instantaneous changes in any phase currents or
zero sequence current in combination with a change in the corresponding phase voltage
or zero sequence voltage. If the change of any phase current and corresponding phase
voltage or 3V0 and 3I0 exceeds the settings and DeltaV respectively. Delta3V0 and and
the input signal BLOCK is not activated, the output signal FLTDET is activated
indicating that a system fault has occurred.
If the setting is set to Enabled in blocking scheme and the fault inception function has
detected a system fault, a block signal BLKCHST will be issued and send to remote
end in order to block the overreaching zones. Different criteria has to be fulfilled for
sending the BLKCHST signal:
1. The setting has to be set to Enabled
2. The breaker has to be closed, that is, the input signal CBOPEN has to be deactivated
3. A reverse fault should have been detected while the carrier send signal is not
blocked, that is, input signal REVSTART is activated and input signal BLOCKCS
is not activated
1MRK505222-UUS C Section 6
Impedance protection
285
Technical reference manual
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