Basler Electric BE1-50/51B-240 - Manual (Page 31)

9252000790 Rev B 23
Characteristic Curves
Introduction
This chapter describes and defines the instantaneous overcurrent, time overcurrent, and integrating time
reset characteristics of the BE1-50/51B-240 relay.
Instantaneous Overcurrent Characteristics
Timing
The instantaneous characteristic curves of the BE1-50/51B-240 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 12 shows the
instantaneous characteristic curves for the maximum time to trip.
Figure 12. Instantaneous Characteristic Curves
The delay of the Instantaneous (50) 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.
Pickup
The instantaneous elements of the BE1-50/51B-240 relay may be set lower than the instantaneous
element in Westinghouse CO relays and still have the same reach. This is because the BE1-50/51B-240
instantaneous elements effectively eliminate the fault current transient overreach components. When
setting the BE1-50/51B-240 instantaneous elements, calculate the symmetrical value without any adder
for transient overreach.
BE1-50/51B-240 Characteristic Curves