ABB Relion 670 Series Applications Manual page 265
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Also See for Relion 670 Series:
- Technical manual (1432 pages) ,
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- Applications manual (944 pages)
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1MRK 511 401-UEN Rev. K
L1
L2
L3
U
L1
C
1
C
C
u
U
TapL1
C
2
C
C
u
U
N
IEC19000703 V1 EN-US
Figure 125: Units and elements arrangement in an ungrounded single WYE capacitor bank
Assume that the voltage at the filter terminal is maintained at 1 pu. The differential voltage is
calculated based on the element failure and the operated fuses. The failure of the capacitor
elements are due to the short-circuit of an element inside the unit. The failure of the unit
occurs due to the fuse operation (open-circuit). For further analysis, considering capacitor
failure has occurred in a section above the tap point of phase L1 as shown in
stored voltage ratio for calculation of differential voltage for phase L1 (USEDURATLx) is 0.5.
The capacitance values in the system are calculated by using the following equations:
•
The capacitance of a unit can be calculated as follows:
C
IECEQUATION19271 V1 EN-US
Where,
C
u
•
The capacitance of the faulty section can be calculated as follows:
C
1
IECEQUATION19273 V1 EN-US
Where,
F
is the number of failed units (F
u
•
The capacitance of a healthy section can be calculated as follows:
C
2
IECEQUATION19274 V1 EN-US
•
The capacitance of phases L1, L2, and L3 can be calculated as follows:
Bay control REC670
Application manual
C
C
C
C
C
u
u
u
u
u
u
C
C
C
C
C
u
u
u
u
u
u
N
´
P C
=
=
e
e
2
C
u
e
S
e
is the capacitance of a unit
=
-
´
(
P
F
)
C
u
u
u
=
´
=
P
C
36
C
u
u
e
© Copyright 2017 Hitachi Power Grids. All rights reserved
C
C
e
e
C
C
e
e
C
C
e
e
C
C
u
u
C
C
e
e
S
u
C
C
u
u
P
u
= 0, 1, 2, ..., 17)
u
Unbalance protection
Single Capacitor Unit
C
C
C
C
C
e
e
e
e
e
C
C
C
C
C
e
e
e
e
e
C
C
C
C
C
e
e
e
e
e
C
C
C
C
C
e
e
e
e
e
P
e
IEC19000703-1-en.vsdx
Figure
(Equation 139)
(Equation 140)
(Equation 141)
Section 10
C
e
C
e
S
e
C
e
C
e
125. The
259
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