FANOX SIA-B, Installation & Commissioning Manual, Page: 12 / 32

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4.1. IEC60255-151 Curves
The SIA-B relay complies with the curves shown in standard IEC 60255-151:
•
Inverse Curve
•
Very Inverse Curve
•
Extremely Inverse Curve
•
Long time Inverse Curve
There is a general mathematical equation that defines thetime in seconds as a function of the
current:
K D B
Q V
D A
t
P
  



adjusted
I
I
V

Parameters A P Q B K
Long time Inverse 120 1 1 0 0
Ext. Inverse 80 2 1 0 0
Very Inverse 13,5 1 1 0 0
Inverse 0,14 0,02 1 0 0
The curve can move from its axis using the D time selection device, which the user can adjust.
I
adjusted
is the initial operating current, set by the user.
4.2. IEEE Curves
The IEEE curves follow the following mathematical equation:
 














 
B
V
A
TD t
P
1
adjusted
I
I
V

And we have the following curves:
•
Inverse Curve
•
Very Inverse Curve
•
Extremely Inverse Curve
Which relate to the parameters figuring in the following table:
Parameters A P B
Ext. Inverse 28,2 2 0,1217
Very Inverse 19,61 2 0,491
Inverse 0,0515 0,02 0,114