Introduction, Instantaneous overcurrent characteristics, Timing – Basler Electric BE1-50/51B-230 User Manual
Page 57: Pickup, Figure a-1. instantaneous characteristic curves, Appendix a • characteristic curves
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BE1-50/51B-230/-234/-239 Characteristic Curves
A-1
APPENDIX A • CHARACTERISTIC CURVES
Introduction
This appendix describes and defines the instantaneous overcurrent, time overcurrent, and integrating
time reset characteristics of the BE1-50/51B-230, BE1-50/51B-234, and BE1-50/51B-239 relays.
Instantaneous Overcurrent Characteristics
Timing
The instantaneous characteristic curves of the BE1-50/51B-230, BE1-50/51B-234, and BE1-50/51B-239
relays are similar to standard electromechanical instantaneous units. However, the time to trip for
applications where the initial sensing current is less than 400 mA may be slightly longer. This may occur
on a very lightly loaded circuit or when the relay is providing ground protection and is connected to
measure neutral current. Figure A-1 shows the instantaneous characteristic curves for the maximum time
to trip.
Figure A-1. Instantaneous Characteristic Curves
The delay of the Instantaneous A (50-A) element can be set for no intentional delay (switch SW3-2 open)
or a fixed delay of 100 ms (SW3-2 closed). Figure 2-2 illustrates the location of SW3. The time delay of
the 50-B element is not switch-selectable and is fixed at no intentional delay.
Pickup
The instantaneous elements of the BE1-50/51B-230, BE1-50/51B-234, and BE1-50/51B-239 relays may
be set lower than the instantaneous element in IAC relays and still have the same reach. This is because
the BE1-50/51B-230, BE1-50/51B-234, and BE1-50/51B-239 instantaneous elements effectively eliminate
the fault current transient overreach components. When setting the BE1-50/51B-230, BE1-50/51B-234,
and BE1-50/51B-239 instantaneous elements, calculate the symmetrical value without any adder for
transient overreach.