52
52
NV10P - Manual - 01 - 2015
CHARACTERISTICS
Undervoltage - 27
Preface
Two operation thresholds, independently adjustable with adjustable delay.
The fi rst one may be programmed with defi nite or inverse time, while the second threshold operates
with defi nite time characteristic.
Each threshold may be separately enabled or disabled.
The fi rst threshold trip may be inhibited by start of the second threshold.
Operation and settings
The fundamental frequency of the input voltages (
U
L1
,
U
L2
,
U
L3
) are employed.
Each of three voltages compared with the setting values (
U
<,
U
<<). 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 goes down the adjust-
able threshold (START); with
AND
selection, a start is issued when all the three voltages go down
the adjustable threshold.
After expiry of the associated operate time (
t
U
<,
t
U
<<) a trip command is issued; if instead the volt-
ages exceed the threshold, the element is restored.
The fi rst threshold (
U
<) may be programmed with defi nite or inverse time according the following
characteristic curve:
t
=0.75
t
U<inv
/ [1-(
U
/
U
<
inv
)]
Where:
t
: operate
time
U
<
inv
: threshold
setting
t
U<inv
: operate
time
setting
For the inverse time characteristic, following data applies:
The operate time setting is referred to an input voltage equal to 1/4 of the pickup value.
Asymptotic reference value (minimum pickup value): 0.9
U
<
Minimum operate time:
0.1 s
Range where the equation is valid: 0 ≤
U
/
U
<
inv
≤ 0.9
The fi rst undervoltage element can be programmed with defi nite or inverse time characteristic by
setting the
U<Curve
parameter (
DEFINITE, INVERSE
) available inside the
Set \ Profi le A(or B) \
Undervoltage-27 \
U
< Element \ Setpoints
menu.
Each element can be enabled or disabled by setting
ON
or
OFF
the
U< Enable
parameter inside
the
Set \ Profi le A(or B) \ Undervoltage-27 \
U
< Element \ Setpoints
menu and/or the
State
parameter
inside the
Set \ Profi le A(or B) \ Undervoltage-27 \
U
<< Element \ Defi nite time
.
The operating logic (AND or OR) is adjustable inside the
Set \ Profi le A(or B) \ Undervoltage-27 \ Com-
mon confi guration
menu by means the
Logic27
parameter
;
the allowed settings are
OR
(at least
one voltage lower than threshold) or
And
(all three voltage must be lower than threshold).
The fi rst threshold trip (
U
<) may be inhibited by start of the second threshold (
U
<<) by setting
ON
the U< Disabling by U<< start (
U<disbyU<<
) parameter available inside the
Set \ Profi le A(or B) \
Undervoltage-27 \ U<< Element \ Setpoints
menu.
User can disable both 27 protection thresholds from the keyboard. During this command, the trip
output relay (U <and / or U << thresholds) are forced to reset state, the message “
27 Disabled
”
is displayed and all LEDs blink until the end of the command.
The elements can be disabled in the case of connection of the measuring inputs (TV or TV-I-NI)
downstream of the Device Interface when the DI is open.
The threshold disabling is selected by setting
ON
the
U<disbyCB_OPEN
,
U<<disbyCB_OPEN
parameters, inside the
Set \ Profi le A(or B) \ Undervoltage-27 \
U< Element (U<< Element) \ Setpoints
menu.
•
•
•
•
t-int-F27.ai
U
U
<<
U
<
0.9
U
<
t
U
<
t
t
U
<<
TRIP
General operation time characteristic for the undervoltage elements - 27
t-int-F27.ai
U
U
<<
U
<
0.9
U
<
t
U
<
t
t
U
<<
TRIP
General operation time characteristic for the undervoltage elements - 27
