Chapter 1 - 7SR45 Description of Operation
©2018 Siemens Protection Devices Limited Chapter 1 Page 29 of 48
Table 3-5
Constants for operating and reset curve characteristics
Operating time
Reset time
Curve type
K
α
P
A
B
R
n
IEC-NI
0.14
0.02
----
----
----
9.7
2
IEC-VI
13.5
1.0
----
----
----
43.2
2
IEC-EI
80
2.0
----
----
----
58.2
2
IEC-LTI
120
1.0
----
----
----
80
2
IEEE/ANSI - MI
----
----
0.02
0.0515
0.114
4.85
2
IEEE/ANSI - VI
----
----
2.0
19.61
0.491
21.6
2
IEEE/ANSI - EI
----
----
2.0
28.2
0.1217
29.1
2
Where,
I - Fault current Magnitude
Is - Pickup setting
Tm - Time multiplier
Table 3-6
Time Delayed Derived Earth Fault Protection (51N-n)
Parameters
Description
Default
Value
Min
Max
Step Change
Gn 51N-n Element 51N-n Block
Disabled
-
-
-
Gn 51N-n Setting
Pick-up current
0.5xI
n
0.1xI
n
0.8xI
n
0.01
Gn 51N-n Char
Characteristics
IEC NI
-
-
-
Gn 51N-n Time
Mult
Time Multiplier
(other than DTL)
1
0.01
10
0.01
Gn 51N-n Delay
Delay
(Applicable only for
DTL)
5 s
0 s
15 s
0.01
Gn 51N-n Min
Operate
Minimum Operate
Time
0 s
0 s
20 s
0.01
Gn 51N-n
Follower DTL
Follower DTL
0 s
0 s
20 s
0.01
Gn 51N-n Reset
Reset
0 s
0 s
60, IEC/
ANSI
DECAY
1