Alternatively, to improve stability, an 81 element can be used as a starter for the 81R elements. In this case the
81R elements could be inhibited until the frequency varies by an abnormal amount; as indicated by the
picking-up of the 81 element.
Where a high rate of frequency change has been detected, indicating a large generated power to load imbal-
ance, it may be preferable to shed 2 or more load groups at the same time without waiting for the relative
underfrequency levels to be reached.
Settings Menu
Functions > Function Config
Parameter Range Settings
Default Gn1 Gn2 Gn3 Gn4
81R Frequency RoCof Enabled
Disabled
Disabled
Functions > Protection > 81R > Gn 81R-n
Parameter Range Settings
Default Gn1 Gn2 Gn3 Gn4
Element Enabled
Disabled
Disabled
Setting 0.05 to 10 Hz/s, Δ 0.05 Hz 0.1 Hz/s
Direction Both
Positive
Negative
Both
Delay (DTL) 0 to 20 s Δ 0.01 s
20 to 100 s Δ 0.1 s
100 to 1000 s Δ 1 s
0 s
IEC 61850 Functional Information Mapping
A81RPFRC*.Mod
Information
81R Frequency Rocof Enabled (Function Config) x 0 1 1
Element Disabled 1 x 0 0
Element Inhibited x x 1 0
A81RPFRC*.Mod.stVal 5 5 2 1
Device Annunciation ON/TRUE: 1
OFF/FALSE: 0
Irrelevant: x
IEC 61850 Value ON: 1
BLOCKED: 2
TEST: 3
TEST/BLOCKED: 4
OFF: 5
5.28.5
5.28.6
Protection and Automation Functions
5.28 81R Frequency Protection – "df/dt"
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 353
C53000-G7040-C014-1, Edition 11.2019
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