Basler Electric BE1-50/51B-241 - Manual (Page 31)

9252000792 Rev D 23
Characteristic Curves
Introduction
This chapter describes and defines the instantaneous overcurrent, time overcurrent, and integrating time
reset characteristics of the BE1-50/51B-241 relay.
Instantaneous Overcurrent Characteristics
Timing
The instantaneous characteristic curves of the BE1-50/51B-241 relay 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 13 shows the
instantaneous characteristic curves for the maximum time to trip.
Figure 13. 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 milliseconds (SW3-2 closed). Figure 5 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-241 relay may be set lower than the instantaneous
element in Westinghouse CO/COM relays and still have the same reach. This is because the
BE1-50/51B-241 instantaneous elements effectively eliminate the fault current transient overreach
components. When setting the BE1-50/51B-241 instantaneous elements, calculate the symmetrical value
without any adder for transient overreach.
BE1-50/51B-241 Characteristic Curves