9424200996 82-1
BE1-11m Time Curve Characteristics
82 • Time Curve Characteristics
This chapter provides time curve information for the inverse overcurrent (51), under/overvoltage (27/59),
and thermal curve (49TC) functions of the BE1-11m.
Inverse Overcurrent (51)
General
The inverse overcurrent (51) time curves provided by the BE1-11m closely emulate most of the common
electromechanical, induction-disk, overcurrent protection systems sold in North America. To further
improve proper BE1-11m 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
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.
Twenty-two inverse time functions, one fixed time function, one 46 time function, one programmable time
function, and four Table Curve functions can be selected. Characteristic curves for the inverse and
definite time functions are defined by the following equations and comply with IEEE Std C37.112 - 1996 -
IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays.
=
+ +
Equation 82-1
=
|
1|
Equation 82-2
T
T
= Time to trip when M ≥ 1
T
R
= Time to reset if BE1-11m 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.
* Timing range is one second times the Time Dial setting when the F (fixed) curve is selected.
Table 82-1 lists time characteristic curve constants. See the figures after the tables for graphs of the
characteristics.
Table 82-1. 51 Time Characteristic Curve Constants
Curve
Selection
Curve Name
Trip Characteristic Constants
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