System Setup and Setpoints – 4
4–79
Time Delay
— A Time Delay can be applied to
delay the 81R ROCOF (Bus Voltage) function output.
The time delay and magnitude settings of the 81R
should be based on simulation studies.
Negative Sequence Voltage Inhibit
— The function
uses the negative sequence voltage to block the
81R.
Increasing ROCOF
— The Increasing ROCOF (Bus
Voltage) can be selected as either Enable or Disable.
When the Increasing ROCOF is selected to Disable,
the 81R function detects the rate of change of
frequency of the motor bus voltage in the decreasing
direction only, and the 81R function is blocked to
detect the increasing direction. When the Increasing
ROCOF is selected to Enable, the 81R function
detects the rate of change of frequency of the motor
bus voltage in both the increasing and decreasing
directions.
I/O Selection
— The I/O Selection
button opens
the
81R ROCOF (
Bus Voltage)
I/O Selection Dialog
Screen (Figure 4-85)
that allows any input or the
Fuse Loss (FL) function to be selected to block the
81R #1(2) Function. The 81R #1(2) Function can
also be used to activate a selected output when it
times out.
Save/Cancel
— The Save selection saves the 81R
#1(2) ROCOF (Bus Voltage) Function Dialog Screen
settings either to an open file or to the target MBTS.
Cancel, returns the user to the previous open screen.
81R (Rate Of Change Of Frequency)
(BUS VOLTAGE)
Path:
System/Setup/Setpoints/81R
Figure 4-84 displays the settings for the
81R #1
ROCOF (Bus Voltage) function. The settings for the
81R #2 ROCOF (Bus Voltage) are the same as the
81R #1.
NOTE
: Bus VT configuration must be set to
Three-Phase to enable the 81R ROCOF
Function.
Enable/Disable
— The top right corner of the display
includes a command button that will disable or
enable the function. This selection allows the
81R
#1
ROCOF (Bus Voltage) to be disabled (or enabled)
independent from the
81R #2.
Pickup
—
The 81R Rate of Change of Frequency
(ROCOF) Bus Voltage function is used to detect
the rate of change of the frequency of the motor bus
as it decays. When the bus is disconnected from
the original source the frequency begins to decrease
and the longer the bus is disconnected the faster
the frequency changes. This function is used to
recognize that the ROCOF has exceeded the Pickup
setting.
This function is typically used for load shedding. If
a load that is causing the frequency to change
quickly can be disconnected, then a transfer may
still be possible. The 81R Function is automatically
disabled during unbalanced faults and other
disturbances.
Summary of Contents for M-4272
Page 1: ...Instruction Book Book 1 of 2 M 4272 Motor Bus Transfer System ...
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Page 200: ...System Setup and Setpoints 4 4 89 Figure 4 93 ISSLogic Function Dialog Screen ...
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Page 214: ...Declaration of Conformity Appendix I I 1 IAppendix I Declaration of Conformity ...
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