Power Automation and Protection Division
I.L. 40-201.9
REL 352 Version 1.00
K-5
K
A
P
P
E
N
D
I
X
.
IKEY
i
i
Figure 4. Square Wave Duration - 50 Hz
50 Hz
Where r = IKEY/IT [rms]
i.e. IKEY = 0.1,
IT = 1 A
IKEY time = t (r) *1000
IT computation
IT = C0xI0+C1xI1+C2xI2
Example:
Applying balanced 3-phase fault of
1A rms requires C1=1 to obtain IT
of 1A rms
I< t(r) >I
f : = 50
r:
0 0.05..1
2
⋅
,
=
t r
( )
:
1
2 f
⋅
----------
r
2
-------
asin
f
π
⋅
----------------------
=
i:
0..48
=
X
i
:
i
π
24
------
⋅
sin
=
y
i
:
i.
π
24
------
π
6
---
+
sin
=
r
t(r)•1000
0
10
0.05
9.77
0.1
9.55
0.15
9.32
0.2
9.1
0.25
8.87
0.3
8.64
0.35
8.41
0.4
8.17
0.45
7.94
0.5
7.7
0.55
7.46
0.6
7.21
0.65
6.96
0.7
6.7
0.75
6.44
0.8
6.17
0.85
5.9
0.9
5.61
0.95
5.31
1
5
1.05
4.67
1.1
4.33
1.15
3.95
1.2
3.55
1.25
3.1
1.3
2.58
1.35
1.93
1.4
0.9
>>
<<[msec]
