Basler Electric BE1-50/51B-240 - Manual (Page 32)

24 9252000790 Rev B
Time Overcurrent Characteristics
Nine inverse time functions and one fixed (definite) time function can be selected at the front panel. Curve
types are identified by a letter designator. Available curve types are short inverse (S), long inverse (L),
definite time (D), moderately inverse (M), inverse (I), very inverse (V), extremely inverse (E), BS142
inverse, (B), and BS142 extremely inverse (C).
Inverse Time Functions
Characteristic curves for the inverse and definite time functions are defined by the following equation:
K BD
C M
AD
T
N T
+ +
−
=
Where: T
T
= time to trip in seconds
D = time dial setting
M = multiple of pickup setting
A, B, C, N, K = constants for the particular curve
Characteristic Curve Groups
Either GE IAC or Westinghouse CO characteristic curve groups are selected through switch SW3-3.
(Refer to Figure 5 for the location of SW3.)
Characteristic Curve Constants
Table 4 and Table 5 list the time characteristic curve constants used by the relay. Constants have been
selected to conform to the characteristics of electromechanical relays over a range of pickup multiples
from 1.3 to 40. Values of the constants are provided for use in PC relay setting applications. Timing
accuracy is
±1 cycle ±2% of time to trip.
Table 4. Time Characteristic Curve Constants with Switch SW3-3 Open (Off)
Curve
Type
Similar To
Figure
Number
Constants
BE A B C N K R
S CO-2 A-2 0.2663 0.03393 1.000 1.2969 0.028 0.500
L CO-5 A-3 5.6143 2.18592 1.000 1.0000 0.028 15.750
D CO-6 A-4 0.4794 0.21359 1.000 1.5625 0.028 0.875
M CO-7 A-5 0.3022 0.12840 1.000 0.5000 0.028 1.750
I CO-8 A-6 8.9341 0.17966 1.000 2.0938 0.028 9.000
V CO-9 A-7 5.4678 0.10814 1.000 2.0469 0.028 5.500
E CO-11 A-8 7.7624 0.02758 1.000 2.0938 0.028 7.750
B BS142-B
∗ A-9 1.4636 0.00000 1.000 1.0469 0.028 3.250
C BS142-C
∗ A-10 8.2506 0.00000 1.000 2.0469 0.028 8.000
F None† None 0.0000 1.00000 0.000 0.0000 0.000 1.000
∗ Curves B and C are defined in British Standard BS142 and IEC 255-4 (International
Electrotechnical Commission).
† Fixed time from 0.1 to 9.9 seconds.
Characteristic Curves BE1-50/51B-240