Rockwell Automation 1407-CGCM Combination Generator Control Module - Manual (Page 165)

Rockwell Automation Publication 1407-UM001G-EN-P - April 2013
165
Appendix
A
Time Over-current Characteristic Curves
General The CGCM unit time over-current protection function provides time/current
characteristic curves that closely emulate most of the common electromechanical,
induction disk relays manufactured in North America. To further improve relay
coordination, selection of integrated reset or instantaneous reset characteristics is
also provided.
Curve Specifications Timing Accuracy (all 51 functions) within ±5% or ±1½ cycles (F/R response) or
-1½ +3 cycles (A response), whichever is greater for time dial settings of D greater
than 0.1 and multiples of 2…40 times the pickup setting but not over 150 A for
5 A CT units or 30 A for 1 A CT units.
Sixteen inverse time functions and one fixed time function can be selected.
Characteristic curves for the inverse and definite time functions are defined by
the following equations.
Figure 41 - Equation 1
Figure 42 - Equation 2
– TT = Time to trip when M = 1
– TR = Time to reset if relay is set for integrating reset when
M < 1. Otherwise, reset is 50 ms or less
– D =T IME DIAL setting (0.0…9.9)
– M = Multiple of PICKUP setting (0…40)
– A, B, C, N, K = Constants for the particular curve
– R = Constant defining the reset time.
These equations comply with IEEE Standard C37.112-1996.
The 51P and 51N Time Characteristic Curve Constants table lists the time
characteristic curve constants.
T
T
A D 
M
N
C –
------------------ B D K +  + =
T
R
R D 
M
2
1 –
------------------- =