Basler Electric BE1-87T - Manual (Page 81)

9171300990 Rev V BE1-87T Installation 4-39
NOTE
Maximum recommended SF=0.5.
Step 17. Determine the maximum external fault multiple (I
E
).
Instantaneous (Unrestraint) Unit Setting
• For wye-connected CTs and with WYE jumpers on Analog Board #2, shown in Figure 2-
4:
I
I
T
E
F
= =
Maximum Relay Fault Current
Corresponding Tap
•
For delta-connected CTs, or with ∆ 1 or ∆ 2 jumpers on Analog Board #2, shown in Figure
2-4, (and based on a phase-to-phase fault): (Refer to Appendix A, Setting Note 3.)
I
I
T
E
F
=
3
3 ( )
HIGH TERTIARY LOW
I
E
=
=
22
6 0
3 7
.
.
I
E
=
=
35 3
2 5
24
.
( )
Step 18. Determine the unrestrained pickup level in multiples of tap (X TAP): Refer to Appendix A,
Setting Note 4.
( ) = 0.7 X TAP × I Max
E
( .)
HIGH TERTIARY LOW
I
E
not maximum I
E
not maximum X TAP = (0.7)24
= 16.8
NOTE
The restrained element will not operate due to the large 2nd harmonic
component present in the highly distorted current.
Step 19. Using the results of Step 18, set the UNRESTRAINED PICKUP LEVEL control. Referring to
the table on the BE1-87T front panel, select the tap position ( X TAP) that is higher than the
result obtained in Step 18. Therefore, for this example, select SET position P (=19 X TAP)
which is higher than the above result of 18.2 A.
Step 20. Determine the multiples of self-cooled current (I
T
): Refer to Appendix A, Setting Note 5.
Slope Setting
Where:
I
R
= relay current (from Step 4)
T = the input tap (from Step 9)
MVA
SELF COOLED
and MVA
FORCED COOLED
are given in Figure 4-35.
I
E
=
=
28 3
2 0
24
.
( )
I
I
T
T
R
=
MVA
MVA
SELF-COOLED
FORCED-COOLED
( )
( )