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FUNCTION CHARACTERISTICS
303
—
Overfrequency - 81O
Preface
The protection is available in the XMR-V, XMR-P, XMR-D and XMR-T versions.
Two operation thresholds, independently adjustable with adjustable delay are provided.
Each threshold may be separately enabled or disabled.
The first threshold trip may be inhibited by start of the second threshold.
Operation and settings
The frequency, acquired from
U
12
,
U
23
,
U
31
phase-to-phase input voltages
[1]
is compared with the
setting values; a start is issued when the frequency overcomes the adjustable threshold (START);
after expiry of the associated operate time a trip command is issued; if instead the frequency drops
below the threshold, the element is restored.
When the frequency value is out of the lock range, it is fixed to the upper or lower limit (20 Hz or 60 Hz).
Both elements operate with definite time characteristic.
Each element can be enabled or disabled by setting
ON
or
OFF
the
State
parameter inside the
Set
\ Profile A (or B) \ Overfrequency-81O \
f
> Element (or
f
>> Element \ Definite time
menu.
The overfrequency protection is enabled only when the maximum of the phase-to-neutral input vol-
tages
U
LMAX
=max(
U
L1
,
U
L2
,
U
L3
) overcomes 0.2
U
n
for a
tfEN
adjustable time.
Setting of the
tfEN
value is available inside the
Set \ Base
menu with “level 1” session.
The first threshold trip (
f
>) may be inhibited by start of the second threshold (
f
>>) by setting
ON
the
f> Disabling by f>> start (
f>disbyf>>
) parameter available inside the
Set \ Profile A (or B) \ Overfre-
quency-81O \ f>> Element \ Setpoints
menu
.
Breaker failure (BF)
Each thresholds (f>, If>>) can be associated to BF (H) and BF (L) protection by activating the relative
parameter in the matrices “Selection of function tripping for BF (H)” or “Selection of function tripping
for BF (L)” in relevant
BF
menus
[2]
:
• Set \ Profile A (or B) \ Breaker failure - BF side H
• Set \ Profile A (or B) \ Breaker failure - BF side L
Note 1 The frequency can also be measured on the three phase-to-phase voltages (calculated vectorially)
Note 2 The common settings concerning the Breaker failure protection are adjustable inside the
Breaker Failure - BF
menu.
f
t
f
>>
def
f
>
def
t
fdef>>
t
fdef>
General operation time characteristic for the overfrequency elements - 81O
TRIP
all-F81O.ai
Logic diagram concerning the overfrequency elements - 81O
f
f
ON=inhibit
2nd Pickup Element
1st Pickup Element
Block1
Block1
Block1
&
Block1
State
f >disby f >>
f
>
def
t
f>def
State
f
>>
def
t
f>>def
f > inhibition
f
> Start
f
> Trip
f
>> Start
f
>> Start
f
>> Trip
Timers-F81.ai
t
fEN
81O-81U Enable
81O-81U disabled
81O-81U disabled
81O-81U enabled
0.20
U
n
Max (
U
L1
,
U
L2
,
U
L3
)
t
Overfrequency & underfrequency enable timer
XMR-D EQUIPMENT MANUAL
Ed. 2.9 - 02/2021