GE 845 Instruction Manual page 347

CHAPTER 4: SETPOINTS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
The Rate of Change element may be set as an instantaneous element with no time delay
or as a definite time delayed element. The rate of change element has the programmable
minimum operating voltage and current thresholds to prevent undesired operation under
specific system conditions.
The settings of this function are applied to each source to produce Pickup and Trip flags.
The Frequency Rate of Change Pickup flag is asserted when the calculated frequency rate
of change of the specified source is above the PKP value, the voltage and current are
above the MINIMUM levels, and the frequency is within a certain range. The Frequency
Rate of Change Trip flag is asserted if the element stays picked up for the time defined by
the Pickup time delay. The element instantaneously drops from Pickup without operation, if
the frequency rate of change drops below 96% of the Pickup value, before the time for
operation is reached.
The minimum voltage and current thresholds select the minimum voltage and current
below which the element is blocked.
The minimum and maximum frequencies set the operating frequency range out of which
the element is blocked.
Path:
Setpoints > Protection > Group 1(6) > Frequency > Frequency Rate of Change1
..\Frequency\Freq Rate of Change 1
Item Name
Function
Signal Input
Trend
Pickup
Pickup Delay
Minimum Frequency
Maximum Frequency
Minimum Voltage
Minimum Current
Block
Relays
Events
Targets
F Rate 1
Value Unit
Disabled
Ph VT Bnk1 J2
Decreasing
0.50 Hz/sec
2.000 s
45.00 Hz
65.00 Hz
0.700 x VT
0.200 x CT
Off
Disabled
Enabled
Self Reset
PROTECTION
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