GE 745 Instruction Manual page 181

CHAPTER 5: SETPOINTS
5.6.11.3 Volts per Hertz
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VOLTS PER
HERTZ 1
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
PATH: SETPOINTS
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The volts per hertz element uses the ratio of the actual measured voltage at the voltage
terminal and the measured system frequency. For example, a measured phases-to-phase
voltage of 120 volts at 60 Hz, results in a ratio of 2 V/Hz. For 115% overload, the setting of
the volts per hertz minimum pickup would be 2.3 V/Hz.
The element has a linear reset characteristic. The reset time can be programmed to match
the cooling characteristic of the protected equipment. The element will fully reset after the
VOLTS-PER-HERTZ RESET
instantaneous element with no intentional delay, as a definite time element, or as an
inverse timed element.
• MINIMUM OPERATING VOLTAGE: Enter the minimum value of voltage (in terms of
nominal VT secondary voltage) required to allow the volts per hertz 1 element to
operate.
• VOLTS-PER-HERTZ 1 PICKUP: Enter the volts per hertz value (in V/Hz) above which the
volts per hertz 1 element will pickup and start the delay timer.
• VOLTS-PER-HERTZ 1 SHAPE: Select the curve shape to be used for the volts per hertz 1
element. The inverse volts per hertz curve shapes are shown below.
• VOLTS-PER-HERTZ 1 DELAY: Enter the time that the volts per hertz value must remain
above the pickup level before the element operates.
• VOLTS-PER-HERTZ 1 RESET: Enter the time that the volts per hertz value must remain
below the pickup level before the element resets.
The curve for the inverse curve 1 shape is derived from the formula:
S4 ELEMENTS OVEREXCITATION

VOLTS-PER-HERTZ 1
FUNCTION: Disabled
VOLTS-PER-HERTZ
RLYS (1-8): --------
VOLTS-PER-HERTZ 1
TARGET: Self-Reset
MINIMUM OPERATING
VOLTAGE: 0.10 x VT
VOLTS-PER-HERTZ 1
PICKUP: 2.36 V/Hz
VOLTS-PER-HERTZ 1
SHAPE: Definite Time
VOLTS-PER-HERTZ 1
DELAY: 2.00 s
VOLTS-PER-HERTZ 1
RESET: 0.0 s
VOLTS-PER-HERTZ 1
BLOCK: Disabled
value. The volts per hertz function can be used as an
D
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T when
=
2
V F ⁄
 
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1
–
 
Pickup
S4 ELEMENTS
VOLTS PER HERTZ 1(2)

Range: Enabled, Disabled
Range: 1 to 8
Range: Self-Reset, Latched, None
Range: 0.10 to 0.99 x VT in steps of
0.01
Range: 1.00 to 4.00 V/Hz in steps of
0.01
Range: Definite Time, Inv Curve 1, Inv
Curve 2, Inv Curve 3
Range: 0.00 to 600.00 s in steps of 0.01
Range: 0.0 to 6000.0 s in steps of 0.1
Range: Logc Inpt 1 to 16, Virt Inpt 1 to
16, Output Rly 2 to 8, SelfTest
Rly, Vir Outpt 1 to 5, Disabled
V
-- -
> Pickup
F
(EQ 5.12)
5–85