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62
NV10P - Manual - 01 - 2015
CHARACTERISTICS
Average overvoltage (59avg)
Preface
The protection has an adjustable threshold and defi nite time characteristic.
Enabling or disabling is provided by means ThySetter.
For inputs from sensors versions, the type of measurement of line voltages and phase voltages may
be select.
Operation and settings
The fundamental component of the three input voltages is measured and the arithmetic mean of the
values of
U
L1
,
U
L2
,
U
L3
phase voltages (versions with inputs from sensors) or
U
12
,
U
23
,
U
31
phase-to-
phase voltages (versions with inputs from inductive VTs) is calculated on the values acquired every
0.2 seconds in a time interval of ten minutes with updates every three seconds on a sliding window
of 10 minutes (200 values ) as indicated below:
The RMS voltages are acquired every 0.2 seconds;
Separately for each phase, the acquired values are aggregated to 10 minutes (600 s) performing
the square root of the arithmetic mean of the last 600/0, 2 = 3000 values squared. The aggregation
of 10 minutes is updated every 3 s.
In response to a step change of the input voltage U (with voltage initially already stabilized), the volt-
age
U
m
has a transitional trend with square-law as shown in the following fi gure.
The pickup time depends on reference conditions
[1]
Each of three voltages is compared with the setting values.
The start and trip logic may be selected
OR
or
AND
; with
OR
selection, a start is issued when at
least one of the three voltages overcomes the adjustable threshold (START); after expiry of the as-
sociated operate time a trip command is issued; if instead the average voltages drops below the
threshold, the element it is restored.
With
AND
selection, a start is issued when all the three average voltages overcomes the adjustable
threshold; after expiry of the associated operate time a trip command is issued; if instead the aver-
age voltages drops below the threshold, the element it is restored.
The operating logic (AND or OR) is adjustable inside the
Set \ Profi le A(or B) \ Average overvoltage-
59Uavg \ Common confi guration
menu by means the
Logic59Uavg
parameter
;
the allowed settings
are
OR
(at least one voltage larger than threshold) or
And
(all three voltage must be larger than
threshold).
Note 1 The pickup time depends on the initial and fi nal value of the input voltage; e.g. with a setting of threshold equal to 1.10 Un:
- with initial value 0 and fi nal value 1.1 Uavg> def (1.1x1.1 = 1.21 Un) the pickup time is 498 s
- with initial value 0.9 Uavg>def (0.9x1.1 = 0.99 Un) and fi nal value 1.1 Uavg>def (1.1x1.1 = 1.21 Un) the pickup time is 285 s
•
•
U
m
=
3000
i=1
¥
3000
1
(
U
i
)
2
U
m
=
3000
i=1
¥
3000
1
(
U
i
)
2
Ten minutes RMS voltage (59Uavg)
200
100
100
200
300
400
500
600
U
Um
0.1
0.3
0.5
0.7
0.9
1.1
1.3
Ten minutes RMS voltage (59Uavg)
200
100
100
200
300
400
500
600
U
Um
0.1
0.3
0.5
0.7
0.9
1.1
1.3
General operation time characteristic for the average overvoltage element - 59Uavg
U
avg
t
Uavg
>
def
U
avg
>
def
t
TRIP
General operation time characteristic for the average overvoltage element - 59Uavg
U
avg
t
Uavg
>
def
U
avg
>
def
t
TRIP
