Operator`s manual

Appendix A: Trip Curves & Equations
Siemens Energy & Automation, Inc. 55
Figure A.7 Extremely Inverse Curve (SEA6)
Figure A.8 Slightly Inverse Curve (SEA7)
0.01
0.1
1
10
100
1000
11050
9.9
7.0
5.0
3.0
1.5
0.5
0.1
Multiples of Pickup
Time to Trip (Seconds)
Time Dial
0.01
0.1
1
10
100
11050
9.9
7.0
5.0
3.0
1.5
0.5
0.1
Multiples of Pickup
Time to Trip (Seconds)
Time Dial
A.3 Definite Inverse Equation
Equation A.2 The ISGS provides an emulation of the
popular CO-6 Definite Inverse characteristic. This curve is
defined by the equations shown in Equation A.3.
Equation A.3 Definite Inverse Equation
In Equation A.3, the time dial term 6.33D + 0.37 is neces-
sary to convert the time dial range defined by Westinghouse
and the range that Siemens is using.
Equation (1) is valid for values of I/Ip greater than 1.5 and
equation (2) is valid for values of I/Ip between 1.0 and 1.5
(note that the equation is undefined at I/Ip = 1.0).
Trip Characteristic
Reset Characteristic
T = time to trip, in seconds
= multiple of pickup setting
D = time dial setting, 0.1 to 9.9 in steps of 0.1
t
r
= reset constant = 1.0394
N = inverse constant = 2.54096
For
i
ip
-----
1.5
T 785
671
i
i
p
----




N
1.19–
-------------------------------
+
6.33D 0.37+
24000
-------------------------------
×=
>
For1.0
i
ip
-----
1.5:
T 785
671
i
i
p
----




N
1.19–
-------------------------------
+
6.33D 0.37+
24000
----------------------------------
×
=
<<
For
i
ip
-----
1 : T
t
r
D
i
i
p
----




N
1–
------------------------
=
<
i
i
p
-----



A
isv3o_1.bk : isv3ocrv.frm Page 55 Wednesday, August 7, 1996 10:51 AM