GE 845 Instruction Manual page 417

CHAPTER 4: SETPOINTS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
BUS VOLTS INPUT
Range: Ph VT Bnk1-J2, Ax VT Bnk1-J2, Ph VT Bnk2-K2, Ax VT Bnk2-K2
Default: Ph VT Bnk1-J2
The setting provides selection of the Bus Volts input; either three-phase voltages from
the three-phase VTs connected to the relay, or a single voltage from the Auxiliary VT also
connected to the relay Aux VT input. The setup of these VTs is outlined under the
SYSTEM/VOLTAGE SENSING menu.
LINE VOLTS INPUT
Range: Ph VT Bnk1-J2, Ax VT Bnk1-J2, Ph VT Bnk2-K2, Ax VT Bnk2-K2
Default: Ax VT Bnk1-J2
The setting provides selection of the Line Volts input; either three-phase voltages from
the three-phase VTs connected to the relay, or a single voltage from the Auxiliary VT also
connected to the relay Aux VT input. The setup of these VTs is outlined under SYSTEM/
VOLTAGE SENSING menu.
MAX FREQ DIFFERENCE
Range: 0.01 to 5.00 Hz in steps of 0.01 Hz
Default: 0.20 Hz
The setting selects the maximum frequency difference in 'Hz' between the two sources.
A frequency difference between the two input voltage systems below this value is within
the permissible limit for synchronism.
MAX ANGLE DIFFERENCE
Range: 1 to 100° in steps of 1°
Default: 20°
The setpoint selects the maximum angular difference in degrees between the two
sources. An angular difference between the two input voltage phasors below this value
is within the permissible limit for synchronism.
MAX VOLT DIFFERENCE
Range: 10 to 600000 V in steps of 1 V
Default: 2000 V
The setpoint selects the maximum primary voltage difference in volts between the two
sources. A primary voltage magnitude difference between the two input voltages below
this value is within the permissible limit for synchronism.
MAX FREQUENCY HYSTERESIS
Range: 0.01 to 0.10 Hz in steps of 0.01 Hz
Default: 0.05 Hz
The setpoint specifies the required hysteresis for the maximum frequency difference
condition. The condition becomes satisfied when the frequency difference becomes
lower than SYNC1 MAX FREQ DIFFERENCE. Once the Synchrocheck element has
operated, the frequency difference must increase above the SYNC1 MAX FREQ
DIFFERENCE + SYNC1 MAX FREQ HYSTERESIS sum to drop out (assuming the other two
conditions, voltage and angle, remain satisfied).
CONTROL
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