9424200996 14-3
BE1-11m Inverse Overcurrent (51) Protection
Curve coefficients are entered on the Inverse Overcurrent (51) settings screen in BESTCOMSPlus.
Programmable curve coefficients can be entered only when the P curve is chosen for the protection
element from the Curve drop-down menu.
Table Curves
BESTCOMSPlus is used to set the 51 element Table Curves (T1, T2, T3, and T4). Using the Settings
Explorer within BESTCOMSPlus, open the Protection, Current, Table Curve (1, 2, 3, or 4) tree branch and
select the table curve to be modified. Refer to Figure 14-1. A minimum of 2 and maximum of 40 points
can be entered for any one T curve. When you are satisfied with the values chosen, select Save Curve.
Use the Settings Explorer to browse to the 51-x element you wish to program and use the drop-down
menu under Curve to select T1, T2, T3, or T4.
Table curves can be entered regardless of the curve chosen for the protection element. However, the
table curve will not be enabled until T1, T2, T3, or T4 is selected as the curve for the protective element.
Figure 14-1. Inverse Overcurrent Table Curve
46 Curve
The 46 curve is a special curve designed to emulate the I
2
t withstand ratings of motors using what is
frequently referred to as the motor’s K factor. Do not confuse the 46 curve with the I2 mode. The 46 curve
was designed for use with the I2 mode. However, in actuality, the 46 curve can be selected for use with
any mode of the inverse overcurrent element as well.
To use the 46 curve, the user should determine the K factor of the motor and the continuous (I
2
)
2
t rating
of the motor (supplied by the manufacturer) and use this to set the time dial and pickup for the 46 curve
by the process described in the Time Curve Characteristics chapter. The K factor is the time the motor
can withstand 1 per unit I
2
where 1 pu is the BE1-11m setting for nominal current.
Pickup and Trip
The Pickup output occurs first, followed by the Trip output.
Pickup
The Pickup output becomes true when the measured current increases above the current threshold
established by the Pickup setting. In BESTlogicPlus, the Pickup output can be connected to other logic
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