2–47
Application - 2
81R #2 PICKUP
________ Hz/s
81R #2 DELAY
________ Cycles
81R NEG SEQ VOLT INHIBIT
25%
81R Rate of Change of Frequency
The Rate of Change of Frequency function can be
used to detect islanding conditions. When the DG
(Dispersed Generation) is islanded, the frequency
either increases or decreases rapidly, depending
upon the generator-load mismatch. If set far from
Nominal Frequency, it may be difficult for over/
underfrequency relay functions to detect islanding.
The Rate of Change of Frequency function provides
proper detection of islanding conditions under these
circumstances.
81R #1 PICKUP
________ Hz/s
81R #1 DELAY
________ Cycles
The function also has an automatic disable feature,
to disable 81R function during unbalanced faults
and other system disturbances. This feature uses
negative sequence voltage to block 81R function.
When the measured negative sequence voltage
exceeds the inhibit setting, the function 81R is
blocked. The time delay and magnitude settings of
81R should be based on simulation studies, and
the setpoint ranges are given in Figure 2-35 below.
Save
Cancel
@ : WARNING, Function DISABLED until output selected!
(81R) - RATE OF CHANGE OF FREQUENCY
Pickup:
Delay:
0.10 Hz/S
1 Cycle
20.0 Hz/S
8160 Cycles
#1
OUTPUT
8
7
6
5
4
3
2
1
FL
6
5
4
3
2
1
Blocking Input
@
Pickup:
Delay:
0.10 Hz/S
1 Cycle
20.0 Hz/S
8160 Cycles
#2
OUTPUT
8
7
6
5
4
3
2
1
FL
6
5
4
3
2
1
Blocking Input
@
Inhibit:
0%
99%
Figure 2-35
M-3822 IPScom
®
for Windows™ Rate of Change of Frequency (81R) Setpoint Ranges
Path
: Relay Menu/Setup/Setpoints/(81R) Rate of Change of Frequency
COMMAND BUTTONS
Save
Saves all information to the relay.
Cancel
Returns the user to the previous window; any changes to the displayed information are lost.
If this function is enabled, the following settings are applicable:
Summary of Contents for M-3520
Page 1: ...Instruction Book M 3520 Intertie Protection Relay ...
Page 83: ...2 50 M 3520 Instruction Book This Page Left Intentionally Blank ...
Page 95: ...M 3520 Instruction Book 3 12 This Page Intentionally Left Blank ...
Page 133: ...M 3520 Instruction Book 5 12 This Page Intentionally Left Blank ...
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Page 213: ...D 12 M 3520 Instruction Book This Page Intentionally Left Blank ...