GE 845 Instruction Manual page 416

CONTROL
IMPORTANT:
IMPORTANT: Once
4–312
Path:
Setpoints > Control > Synchrocheck 1
Setpoints\Control\Synchrocheck 1
Item Name
Function
Bus Volts Input
Line Volts Input
Max Freq Difference
Max Angle Difference
Max Volt Difference
Max Freq Hysteresis
Dead Source Perm
Live Bus Volts Min
Live Line Volts Min
Dead Bus Volts Max
Dead Line Volts Max
Block
Relays
Events
Targets
Sync 1
The selection of "Aux VT Connection" under
determines the voltage used for synchrocheck as derived from the three-phase voltages
available on the relay. For example, if the Aux VT Connection is selected as Vab, and the
three-phase VTs are connected in "Wye", the relay computes delta voltage Vab as well, and
uses it for Synchrocheck.
The Synchrocheck cannot be performed if the three-phase VTs are Delta connected,
and the Wye single voltage input is selected under "Aux VT connection". "Wye"
voltages cannot be calculated from Delta connected VTs.
Once the Synchrocheck function is programmed, it will perform a voltage input
selection check, to determine that these voltage magnitudes are not different by more
than 5% of each other. This check depends only on the settings entered for phase and
auxiliary VTs under Setpoints/System/Voltage Sensing menu. If the difference between
the both selected voltage inputs by calculation is bigger than 5%, the Synchrocheck
will not work.
For example, the phase VT can be set to Wye connection with secondary voltage of
66.4V. The Aux. VT can be connected between phase A to B with the secondary voltage
set to 115V. Then, one of the Synchrocheck inputs can be set as the V
from the Wye connected phase VTs, and the other output can be the Aux. VT with
voltage V . Since the difference between the computed V
ab
setting is 0%, the Synchrocheck will work. However, if this difference is bigger than 5%,
the Synchrocheck will not work.
FUNCTION
Range: Disabled, Enabled
Default: Disabled
Value
Disabled
Ph VT Bnk1 J2
Ax VT Bnk1 J2
0.20
20
2000
0.05
Disabled
0.80
0.80
0.20
0.20
Off
Disabled
Enabled
Self Reset
Setpoints > System > Voltage Sensing
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
Unit
Hz
°
V
Hz
x VT
x VT
x VT
x VT
voltage derived
ab
input and the Aux. VT
ab