Thytronic NC20 User Manual

82
82
NC2 0 - Manual - 01 - 2015
FUNCTION CHARACTERISTICS
Phase overcurrent - 50/51 RMS
Preface
One alarm and one operation threshold, independently adjustable (I>
AL
, I>) with adjustable delay
(t>
AL
, t>).
The fi rst one, useful for alert approaching to the capacitor overvoltage, have a defi nite time char-
acteristic.
The operation threshold may be programmed with defi nite or inverse time according the IEC and
ANSI/IEEE standard, as well as with CAPACITOR curve (optimum compliance to ANSI and IEC stan-
dards).
A reset time can be set (t
>RES
) useful to reduce the clearing time for intermittent faults.
The fi rst alarm threshold may be inhibited by start of the operation threshold (I>).
Operation and settings
Each phase RMS current (including up to eleventh harmonic) 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 restored.
The fi rst threshold (I>) may be programmed with defi nite or inverse time according the following
characteristic curves:
Standard Inverse Time (IEC 255-3/BS142 type A or SIT): t = 0.14 · t>
inv
/ [(I
RMS
/I>
inv
)
0.02
- 1]
Very Inverse Time (IEC 255-3/BS142 type B or VIT): t = 13.5 · t>
inv
/ [(I
RMS
/I>
inv
) - 1]
Extremely Inverse Time (IEC 255-3/BS142 type C or EIT): t = 80 · t>
inv
/ [(I
RMS
/I>
inv
)
2
- 1]
Moderately Inverse (ANSI/IEEE type MI): t = t>
inv
· {0.01 / [(I
RMS
/I>
inv
)
0.02
- 1] + 0.023}
Very Inverse (ANSI/IEEE type VI): t = t>
inv
· {3.922 / [(I
RMS
/I>
inv
)
2
- 1] + 0.098}
Extremely Inverse (ANSI/IEEE type EI): t = t>
inv
· {5.64 / [(I
RMS
/I>
inv
)
2
- 1] + 0.024}
CAPACITOR: t = t>
inv
· {50000 / [1.1 · (I
RMS
/I>
inv
)
17
-1]} + 0.1
Where:
t: operate time
I
RMS
: RMS input current
I>
inv
: threshold setting
t>
inv
: operate time setting
The alarm threshold (I>
AL
) has defi nite time characteristic.
For all inverse time characteristics, following data applies:
Asymptotic reference value (minimum pickup value): 1.1 I>
inv
Minimum operate time: 0.1 s
Range where the equation is valid:
[1]
1.1 ≤ I
RMS
/I>
inv
≤ 20
If I>
inv
pickup ≥ 2.5 I
n
, the upper limit is 50 I
n
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>AL Enableand/or
I> Enable parameters inside the Set \ Profi le A(or B) \ Phase overcurrent-50/51 RMS \ I>AL Element
(I> Element) \ Setpoints menus.
The fi rst overcurrent element can be programmed with defi nite or inverse time characteristic by
setting the I>Curve parameter (DEFINITE, IEC/BS A, IEC/BS B, IEC/BS C, ANSI/IEE MI,
ANSI/IEE VI, ANSI/IEE EI, CAPACITOR) available inside the Set \ Profi le A(or B) \ Phase over-
current-50/51 RMS \ I> Element \ Setpoints menu.
The operation of I>AL element may be inhibited by:
The start of the fi rst element (I>) by setting ON the Disable I>AL by start I> (I>ALdisbyI>) parame-
ters available inside the Set \ Profi le A(or B)\ Phase overcurrent-50/51 RMS \ I> Element \ Setpoints
menu.
The start of second and/or third element (I>>, I>>>) of the fundamental frequency phase overcurrent by set-
ting ON the Disable I>AL by start I> (I>ALdisbyI>>, I>ALdisbyI>>>) parameters available inside
the Set \ Profi le A(or B) \ Phase overcurrent-50/51 Fundamental \I>> Element, (I>> Element) \ Setpoints
menus
Note 1 When the input value is more than 20 times the set point , the operate time is limited to the value corresponding to 20 times the set point
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t-int-F50-51.ai
I
RMS
I>
t>
AL
t>
I>
AL
t
TRIP
General operation time characteristic for the phase overcurrent elements - 50/51 RMS

Thytronic NC20 Specifications

General

Brand	Thytronic
Model	NC20
Category	Power distribution unit
Language	English