ABB Relion 670 Series Applications Manual page 247

1MRK 511 401-UEN Rev. K
Table 35:
No of
fuses
operated
0
0
0
0
0
0
1
1
1
1
1
1
2
2
2
2
2
2
According to IEEE Standard C37.99-2000, a capacitor bank must be removed from the service
when the current flowing through the unit exceeds 135% of its rated current. Hence, the trip is
given after 2 elements failed in the faulty unit.
If the failure of the elements or the units results in the unbalance current of at least 1% of
IBase2, the SCUCPTOC function detects the fault.
Figure 114
the considered ungrounded double WYE connected capacitor bank.
Bay control REC670
Application manual
Unbalance current calculation for ungrounded double WYE capacitor bank element failures
No of C I
L1l UNBL1
shorted
(*C ) (A)
e
elements
0 2.00 0.00
1 2.13 4.81
2 2.33 12.03
3 2.66 23.44
4 3.33 44.86
5 5.33 97.67
0 1.33 26.58
1 1.46 21.18
2 1.66 13.11
3 2.00 0.00
4 2.66 23.44
5 4.66 81.58
0 0.66 56.52
1 0.80 49.96
2 1.00 40.87
3 1.33 26.58
4 2.00 0.00
5 4.00 64.23
shows the neutral current variation with the number of units or elements failure for
© Copyright 2017 Hitachi Power Grids. All rights reserved
I I I
P MEMUNBL1 MEML1
(A) (A) (A)
299.76 0.00 0.00
301.88 4.81 301.88
304.97 4.81 301.88
309.66 4.81 301.88
317.89 4.81 301.88
335.42 4.81 301.88
287.20 4.81 301.88
289.88 4.81 301.88
293.76 4.81 301.88
299.76 4.81 301.88
309.66 4.81 301.88
330.45 4.81 301.88
271.03 4.81 301.88
274.78 4.81 301.88
279.77 4.81 301.88
287.20 4.81 301.88
299.76 4.81 301.88
324.74 4.81 301.88
Unbalance protection
I I %I
REFUNBL1 UNBCLCL1 unit
(A) (A) (%)
0.00 0.00 0.00
4.81 0.00 117.45
4.86 7.16 142.18
4.94 18.49 180.18
5.07 39.78 245.56
5.35 92.31 385.85
4.58 22.00 112.57
4.62 16.56 131.87
4.68 8.42 159.01
4.78 4.78 200.00
4.94 18.49 270.27
5.27 76.31 415.71
4.32 52.19 128.76
4.38 45.57 150.00
4.46 36.41 180.00
4.58 22.00 225.14
4.78 4.78 300.00
5.18 59.05 450.00
Section 10
Event
Trigger
Trip
241