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 tfENadjustable 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
f
def>>
t
f
def>
General operation time characteristic for the overfrequency elements - 81O
TRIP
all-F81O.ai
Logic diagram concerning the overfrequency elements -
81O
ff
ON=inhibit
2nd Pickup Element 1st Pickup Element
Block1
Block1
Block1
&
Block1
State
f>disbyf>>
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 disabled81O-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
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