89
NC2 0 - Manual - 01 - 2015
FUNCTION CHARACTERISTICS
Phase overcurrent - 50/51 Fundamental
Preface
Two operation thresholds, independently adjustable (I>>, I>>>) with adjustable delay
(t>>, t>>>) and defi nite time characteristic.
For each threshold a reset time can be set (t
>>RES
, t
>>>RES
) useful to reduce the clearing time for
intermittent faults.
The second threshold trip may be inhibited by start of the third threshold (I>>>).
Operation and settings
Each phase fundamental frequency current is compared with the setting value. Currents above the
associated pickup value are detected and a start is issued. After expiry of the associated operate
time a trip command is issued; if instead the current drops below the threshold, the element is re-
stored.
For all defi nite time elements the upper limit for measuring is 50 I
n
.
All overcurrent elements can be enabled or disabled by setting ON or OFF the I>> Enable and/or
I>>> Enable parameters inside the Set \ Profi le A(or B) \ Phase overcurrent-50/51 Fundamental \
I>> Element (I>>> Element) \ Setpoints menus.
The trip of I>> element may be inhibited by the start of the third element (I>>>) by set-
ting ON the Disable I>> by start I>>> (I>disbyI>>>) parameter available inside the
Set \ Profi le A(or B) \ Phase overcurrent-50/51 Fundamental \ I>>> Element \ Setpoints menu.
The trip of I>
AL
(RMS) element may be inhibited by the start of the second and/or third element
(I>>, I>>>) of the fundamental frequency phase overcurrent by setting ON the Disable I>
AL
by start I>>
and/or Disable I>
AL
by start I>>> (I>ALdisbyI>>, I>ALdisbyI>>>) parameter available inside the
Set \ Profi le A(or B) \ Phase overcurrent-50/51 Fundamental \ I>> Element (I>>> Element) \ Setpoints
menu. Similarly, the operation of I> (RMS) element may be inhibited by the start of the second and/or
third element (I>>, I>>>) of the fundamental frequency phase overcurrent by setting ON the Dis-
able I> by start I>> and/or I>>> (I>disbyI>>, I>disbyI>>>) parameters available inside the
Set \ Profi le A(or B) \ Phase overcurrent-50/51 Fundamental \ I>> Element (I>>> Element) \ Setpoints
menus.
An adjustable reset time delay is provided for every threshold (t
>>RES
, t
>>>RES
).
Each overcurrent element can produce the Breaker Failure output if the I>> BF and/or I>>>
BF parameters are set to ON. The parameters are available inside the Set \ Profi le A(or B) \ Phase
overcurrent-50/51 Fundamental \ I>> Element (I>>> Element) \ Setpoints menus.
[1]
Note 1 The common settings concerning the Breaker failure protection are adjustable inside the Breaker Failure - BF menu.
t-int-F50-51F.ai
I
I>> I>>>
t>>
t>>>
t
TRIP
General operation time characteristic for the phase overcurrent elements - 50/51 Fundamental
Timers-F50-51.ai
I> Start
I> Trip
t
>
t
>
RESET
INPUT
t
>RES
t
>RES
t
>RES
t
I> element phase overcurrent timers - 50/51
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