Siemens ISGS SG8158-00 - Manual (Page 63)

Appendix A: Trip Curves & Equations
Siemens Energy & Automation, Inc. 57
Table A.2 Under/Overvoltage Coefficients
Equation A.5 Overvoltage Equation
Equation A.6 Undervoltage Equation
Over/Undervoltage Coefficients
Curve Type Des. A 1 B 1 N 1 t
r
Inverse 0.51 -1.75 0.50 ---
Mod. Inverse 0.51 -0.45 0.50 ---
Very Inverse 0.51 1.75 0.50 ---
The A, B, and N coefficients are for the standard relay formula
T = time to trip, in seconds
v = measured input voltage
v
F
= pickup value (tap setting)
= multiple of pickup setting
D = time dial setting, 0.1 to 9.9 in steps of 0.1
A, B, N
= constants for inverse curves
For1.01
v
v
p
----- 1.5: T
AD
v
vp
----- 


 N
1 –
------------------------- BD + = ≤ ≤
For
v
v
p
----- 1.5: T
AD
1.5 ) (
N
1
–
-------------------------- BD + = >
 
 
 
v
vp ------
 
 
 
T = time to trip, in seconds
v = measured input voltage
v
F
= pickup value (tap setting)
= multiple of pickup setting
D = time dial setting, 0.1 to 9.9 in steps of 0.1
A, B, N
= constants for inverse curves
For 0.5
v
v
p
----- 1.5: T
AD
v
vp
----- 


 N
1
–
------------------------- BD + = ≤ ≤
For
v
v
p
----- 0.5:
T
AD
1.5 ) (
N
1
–
-------------------------- BD + = ≤
 
 
 
v
vp
------
 
 
 
Figure A.11 Moderately Inverse Overvoltage Curve
Figure A.12 Moderately Inverse Undervoltage Curve
Multiples of Pickup
T
ime to T
rip (Seconds)
T
ime Dial
1000
100
10
1
0.1
9.9
5.0
2.0
1.0
0.5
0.2
0.1
1 1.1 1.2 1.3 1.4 1.5 1.6
Multiples of Pickup
T
ime to T
rip (Seconds)
T
ime Dial
1000
100
10
1
0.1
9.9
5.0
2.0
1.0
0.5
0.2
0.1
0.4 0.5 0.6 0.7 0.8 0.9 1.0
A
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