Technical description
2 Protection functions
2.9 Overfrequency and
underfrequency Protection f>, f<
(81H/81L)
VM55.EN005
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Parameters of the over & underfrequency stages
f><, f>><<, f<, f<< (81H/81L):
Parameter
Value
Unit
Description
Note
Status
-
Blocked
Start
Trip
Current status of the stage
F
F
SCntr
Cumulative start counter
C
TCntr
Cumulative trip counter
C
SetGrp
1 or 2
Active setting group
Set
SGrpDI
-
DIx
VIx
LEDx
VOx
Fx
Digital signal to select the
active setting group
None
Digital input
Virtual input
LED indicator signal
Virtual output
Function key
Set
Force
Off
On
Force flag for status forcing for
test purposes. This is a
common flag for all stages and
output relays, too.
Automatically reset by a 5-
minute timeout.
Set
f
Hz
The supervised value.
fX
fXX
f<
f<<
Hz
Pick-up value
Over/under stage f><. See
Mode
Over/under stage f>><<.
Under stage f<
Under stage f<<
Set
tX
tXX
t<
t<<
s
Definite operation time
f>< stage
f>><< stage
f< stage
f<< stage
Set
Mode
>
<
Operation mode. (only for f><
and f>><<)
Overfrequency mode
Underfrequency mode
Set
LVblck
%Un
Low limit for self blocking.
This is a common setting for
all four stages.
Set
For details of setting ranges see chapter 9.3.
Set = An editable parameter (password needed)
C = Can be cleared to zero
F = Editable when force flag is on