GE PACSystems RX3i User Manual page 65

Reconstructed Variables
Relay Open/Relay Close Operation
GFK-2749
If a PTn/CTn control bit is set, the corresponding voltage/current is measured and the
PSM system can use it. If cleared, the variable is not measured and the PSM module will
try to reconstruct the missing samples from the other measured variables. The following
table explains which variable in which measured system configuration can be
reconstructed.
Dependence of reconstructed variable on measured variables
Variable
GRIDx In
GRID In
GRIDx Vac/Vab
GRIDx Ib/Ic
In the three-phase Delta mode when only two voltages/currents are required to be
measured (non-measured variable can be reconstructed), the two available channels can
be used for an independent single voltage and/or current measurement
Note: If the PSM system will be used for generator synchronization with a Delta system
it is required that in both grids, the channels of non-measured voltage and current
are left unused so that these variables can be reconstructed.
The Relay Open/Relay Close bits (%Q16 / %Q32) control the PSM's Sync controller
function. The PSM can close the Sync contacts only if no ANSI alarm has been detected.
The PSM opens the Sync contacts immediately (i.e. without waiting for the PLC to issue
the 1-0 bit combination) if any of the ANSI alarms has been detected. It is recommended
that after a successful Sync relay connection, the PLC sets those two bits to either a 0-0
or 1-1 (no action) state. Then, after an sync relay disconnection unintentional (e.g. due to
some ANSI alarm) the PSM will not be able to close the Sync contacts without PLC
intervention.
Relay Open (%Q16)
0
0
1
1
Chapter 3 Configuration and Data Transfer
Missing Neutral in a 3-phase WYE connection if all phase currents are
measured
Missing Neutral in a 3-WIRE single phase system
Missing (common phase) voltage in a 3-phase DELTA system (default is
Vac)
Missing (common phase) current in a 3-phase DELTA system (default is
Ib)
Relay Close (%Q32)
0
1
0
1
Conditions
PSM Action
No action
Closes Sync contacts
Opens Sync contacts
No action
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