ABB Distribution Protection Unit 1500R
11-11
Maintenance and Testing
9/99
website:www.abb.com/papd
5.
In this case, I
2
is determined in the relays as follows:
I
2
= 1/3 (Ia + a
2
I
b
+ aIc)
where:
a = 1
120
a
2
= 1
-120
since Ic = 0, then
I
2
= 1/3 (Ia + (1
-
120
)
Ib)
= 1/3 (12
0
+ (1
-120) (12
180
)
= 1/3 (12
0
+ 12
60
)
= 1/3 (20.7 30
°)
∴
I
2
= 6.9
30
°
therefore, we are at approximately 2x pickup.
6.
The relay should trip between 14.3 and 16.3 seconds (from the Extremely Inverse Curve, Figure 1-6) and only
the NEGATIVE SEQUENCE LED should light.
Negative Sequence Testing
Follow these steps to test the 46 (Insc>) function:
1.
Disable all instantaneous functions - 50P-1 (3I>>1), 50P-2(3I>>2), 50P-3 (3I>>3).
2.
Raise the 51P (3I>) Pickup setting to 12A to prevent a 51P (3I>) operation during this test.
3.
Set the 46 (Insc>) function according to the following values:
•
Curve:
Extremely Inverse
•
Pickup:
3.5A
•
Time Dial:
5.0
4.
Apply the following currents as shown in Figure 11-3:
•
Ia (L1) = 12 A
0°
•
Ib (L2) = 12 A
180°
•
Ic (L3) = 0
This phase-to-phase fault simulation will produce a two per unit negative-sequence current, 6.9A I
2
, (12A x 58%
= 6.9A), in the DPU1500R.
•
In = 0
)
)
