35
Protection characteristics(general)
Protection characteristics of Electronic trip unit
The protection features of the intelligent controller include inverse time limit and timing limit. When
the fault current exceeds the inverse time limit setting value, the controller sets the time delay
protection according to the fixed time limit
Inverse time curve conforms to characteristic curve I
2
t
Overload long time delay protection characteristics
Action threshold of overload long time delay protection
<1.05I
R
：>2h No action
>1.2I
R
：<1h action
≥1.2I
R
：Delay action
I
R
Current setting range：0.4In，0.5In，0.6In，0.7In，0.8In，0.9In，0.95In，0.98In，1.0In，
Inverse time action characteristic I
2
t：t=（6/N）
2
*t
R
Setting current
multiple
Action time s
1.5I
R
16
32
64
128
192
256
320
384
480
2I
R
9
18
36
72
108
144
180
216
270
6I
R
1
2
4
8
12
16
20
24
30
Note：
N：
Fault current divided by multiple of set current I/I
R
t：
Fault action delay time
t
R
：
Long delay time setting
Allowable error of action time±10%
Short circuit short time delay protection characteristics
Action threshold of short circuit short time delay protection
<0.9Isd：No action
>1.1Isd：action
≥1.1Isd：Delay actio
Isd Current setting range：1.5I
R
，2I
R
，3I
R
，4I
R
，5I
R
，6I
R
，8I
R
，10I
R
+OFF
current
Action time
Isd<I≤8I
R
Inverse time limit
Action
characteristics
I
2
t=（8I
R
）
2
tsd
Setting time s
0.1
0.2
0.3
0.4
I≥1.1Isd
Timing limit,
minimum time is
return time
Setting time s
0.1
0.2
0.3
0.4
Minimum s
0.08
0.14
0.23
0.35
Maximum s
0.14
0.2
0.32
0.5
Note：
Isd：
Short delay current setting
I：
Fault current value
I
R
：
Long delay set point
t：
Fault action delay time
tsd：
Short time delay inverse time limit setting value
Allowable error of action time±20%
(off of time period means I
2
t off, i.e. inverse time limit is closed, which is fixed time limit;
use off of current gear to close short time delay protection function)
Debugging CDW3
