Basler BE1-CDS220, Instruction Manual

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BE1-CDS220 Time Overcurrent Characteristic Curves A-1
APPENDIX A • TIME OVERCURRENT
CHARACTERISTIC CURVES
GENERAL
Basler Electric inverse time overcurrent systems (ANSI Device 51) provide time/current characteristic
curves that very closely emulate most of the common electro-mechanical, induction disk relays that were
manufactured in North America. To further improve proper 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, whichever is greater,
for time dial settings of D greater than 0.1 and
multiples of 2 to 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, one fixed time
function, and one programmable time function can
be selected. Characteristic curves for the inverse
and definite time functions are defined by the
following equations and comply with IEEE
C37.112 - 1996.
K D B
C M
D A
T
N
T
+ ⋅ +
−
⋅
=
Equation A-1
1 M
D R
T
2
R
−
⋅
=
Equation A-2
T
T
= Time to trip when M
≥
1
T
R
= Time to reset if relay is set for integrating
reset when M
<
1. Otherwise, reset is 50
milliseconds or less
D = TIME DIAL setting (0.0 to 9.9)
M = Multiple of PICKUP setting (0 to 40)
A, B, C, N, K = Constants for the particular curve
R = Constant defining the reset time.
Table A-1 lists time characteristic curve constants.
See Figures A-1 through A-16 for graphs of the
characteristics.