Basler Electric BE1-51/27R - Manual (Page 8)

2 9137200999 Rev F
Operating Characteristics at Reduced Voltages
BE1-51/27R relays adjust the operating parameters based on system voltage. The sensitivity of the relay
is increased as the system voltage drops. This provides a means of discriminating between load and fault
conditions.
A decrease of the sensed voltage to a point between 100 percent and 25 percent of nominal results in a
proportional decrease in the time overcurrent pickup point. Thus, at 50 percent nominal voltage, the time
overcurrent relay will pickup at 50 percent of the setting (TAP + Calibration). At voltages above 100
percent nominal, the pickup will be the same as the setting. At voltages below 25 percent of nominal, the
pickup will be 25 percent of the setting. Note that the BE1-51/27R is designed to trip at currents less than
the setting if the voltage is depressed.
The timing characteristics of the BE1-51/27R continue to operate on multiples of pickup basis. Pickup
refers not to the setting, but to the operating point as adjusted for voltage. Thus, with a setting of 5.0
amperes, and system voltage of 50 percent, a current of 5.0 amperes represents 2 times pickup. For a
given fault current magnitude, the relay will trip faster at reduced voltage, because the multiples of pickup
increases.
Table 1 shows the timing characteristics at normal and reduced voltages. The curve is B4 and the time
dial is five. The pickup is five amperes. Tables 2 and 3 show the timing characteristics for multiples of
setting as it relates to multiples of pickup with the BE1-51/27R at 25 percent voltage.
Table 1. Timing, Characteristic Curve B4, with BE1-51/27R at 100% and 50% Voltages
Fault
Current
System
Voltage Effective
Pickup
Multiples of
Pickup
Approximate Trip
Time
4.25 A 100% 5.0 A <1.0 No Trip
4.25 A 50% 2.5 A 1.7 1.499 s
4.25 A 0% 1.25 A 3.4 0.507 s
7.50 A 100% 5.0 A 1.5 1.873 s
7.50 A 50% 2.5 A 3.0 0.772 s
7.50 A 0% 1.25 A 6.0 0.474 s
15.00 A 100% 5.0 A 3.0 0.772 s
15.00 A 50% 2.5 A 6.0 0.474 s
15.00 A 0% 1.25 A 12.0 0.355 s
Table 2. Timing, Curve B4, BE1-51/27R at 25% Voltage (00 to 10 Time Dial Settings)
Multiple of
Setting
Multiple of
Pickup
Time Dial Setting (Seconds)
00 01 02 03 05 07 10
0.38 1.50 0.604 0.856 1.111 1.370 1.873 2.384 3.142
0.43 1.70 0.480 0.688 0.899 1.104 1.499 1.930 2.504
0.50 2.00 0.382 0.539 0.705 0.866 1.194 1.517 1.994
0.55 2.20 0.344 0.484 0.633 0.775 1.063 1.349 1.780
0.63 2.50 0.300 0.419 0.548 0.663 0.918 1.168 1.542
0.68 2.70 0.278 0.387 0.508 0.620 0.850 1.073 1.420
0.75 3.00 0.250 0.354 0.461 0.561 0.772 0.977 1.284
0.88 3.50 0.218 0.308 0.403 0.494 0.672 0.855 1.127
1.00 4.00 0.202 0.281 0.360 0.445 0.602 0.772 1.016
1.13 4.50 0.186 0.261 0.334 0.410 0.557 0.709 0.936
1.25 5.00 0.176 0.243 0.308 0.377 0.506 0.649 0.831
Introduction BE1-51/27R