GE 845 Instruction Manual page 326

PROTECTION
4–222
Signal Input to "Aux VT Bnk1-J2". If there is no voltage on the relay terminals in either case,
the per-unit V/Hz value is automatically set to "0". The per unit value is established based
on the voltage and nominal frequency power system settings as follows:
1. If the phase voltage inputs defined in the source menu are used for V/Hz operation,
then "1 pu" is the selected
Voltage 1 > Phase VT Secondary
System > Nominal Frequency
2. When the auxiliary voltage Vx is used (regarding the condition for "None" phase
voltage setting mentioned above), then the 1 pu value is the
Voltage Sensing > Ph VT Bnk1-J2 > Voltage 1-J2 > Aux. VT Secondary
the
Setpoint > System > Power System > Nominal Frequency
3. If the V/Hz source is configured with both phase and auxiliary voltages, the maximum
phase among the three voltage channels at any given point in time is the input voltage
signal for element operation, so the per-unit value is calculated as described in item 1,
see previous items. If the measured voltage of all three phase voltages is "0", then the
per-unit value becomes automatically "0" regardless of the presence of an auxiliary
voltage.
The element has a linear reset characteristic. The reset time can be programmed to match
the cooling characteristics of the protected equipment. The element will fully reset from
the trip threshold in Reset Time seconds. The V/Hz element can be used as an
instantaneous element with no intentional time delay or as a Definite or Inverse timed
element. The characteristics of the inverse curves are shown as follows.
Path: Setpoints > Protection > Group 1(6) > Voltage > Volts per Hertz 1(2)
..\Voltage\Volts per Hertz 1
Item Name
Function
Signal Input
Voltage Mode
Pickup
Curve
TD Multiplier
T Reset
Block
Output Relays
Events
Targets
V/Hertz 1
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
This setting enables the Volts per Hertz functionality.
SIGNAL INPUT
Range: Ph VT Bnk1-J2, Aux VT Bnk1-J2
Default: Ph VT Bnk1-J2
This setting specifies the input voltage used to calculate the per-unit volts-per-hertz (V/
Hz). If three phase voltages are used then set the AC Inputs to "Ph VT Bnk1-J2". To use the
V/Hz element with auxiliary voltage, set AC Inputs to "Aux VT Bnk1-J2".
Setpoint > System > Voltage Sensing > Ph VT Bnk1-J2 >
setting, divided by the
setting.
Value
Disabled
Ph VT Bnk1 J2
Phase ground
0.80
Definite Time
1.00
1.00
Off
Do Not Operate
Enabled
Sef Reset
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
Setpoint > System > Power
Setpoint > System >
setting divided by
setting.
Unit
V/Hz