Basler Electric BE1-87T - Manual (Page 17)

9171300990 Rev V BE1-87T General Information 1-5
Specifications
The BE1-87T relay is available in either single-phase or three-phase configurations and with the following
features and capabilities.
Current Sensing Inputs The unit is designed to operate from the secondary of current
transformers rated at either 1 A or 5 A. Frequency range is ±5 Hz of
nominal.
Maximum Current Per Input
1 Ampere CT Units 4 A continuous; 50 A or 50 X tap (whichever is less) for 1 second.
5 Ampere CT Units 20 A continuous; 250 A or 50 X tap (whichever is less) for 1
second.
For ratings other than one second, the rating may be calculated as:
Where:
t is the time (in seconds) that the current flows
K = 50 A or 50 X tap, whichever is less (1 Amp CT Units), or
K = 250 A or 50 X tap, whichever is less (5 Amp CT Models)
Current Sensing Burden Less than 0.02 ohm per phase.
Tap Setting Control (Scaling) Front panel rotary switches, labeled INPUT, permit scaling the
sensed input current (or tap setting) over the range of:
1 Ampere CT Units 0.4 to 1.78 in 0.02 A increments.
5 Ampere CT Units 2.0 to 8.9 A, in 0.1 A increments.
Restrained Output
Pickup Range Front panel thumbwheel switches adjust pickup of the restrained
output as a percentage of the through current. The range is 15 to
60% of the operating current in 5% increments.
Pickup Accuracy ± 6% of pickup ±100 mA (5 Ampere Units) or ±20 mA (1 Ampere
units).
Minimum Pickup 0.35 ±6% of tap setting. Refer to Table 1-1 and Figure 1-2. Table 1-1
provides calculated intersection points of the slope characteristic
and the minimum pickup (in multiples of tap) as shown in Figure
1-2. The calculation was derived from the formula:
For example:
The relay operates when the per unit difference current (operating
current) is above the 0.35 pu or the slope line in Figure 1-2.
Calculation examples are found in Section 5.
I K
t
=
Maximum I
Minimum Pickup
Percent of Slope
Restraint
=
Minimum Pickup
Percent of Slope =
=
0.35
20
1.75
%