Siemens 7SJ82 Manual page 988

Capacitor Bank Protection
7.4 Current-Unbalance Protection for Capacitors, 3-Phase
In this example, the phase current is determined using the following assumptions and data:
•
1-phase rated capacitance of the capacitor bank: 2.81 μF
•
Phase-to-ground voltage of the fundamental component of the capacitor bank: 249.1 kV
•
Current per phase: I
2e) Capacitance of a Can during an Element Fault
To do this, the capacitance of an individual C-element will be determined first:
•
Capacitance of a C-element:
•
Capacitance of a can during an element fault:
C = 19.456 μF
K,1EF
2f) Capacitance in the Quarter of the H Connection during an Element Fault
Consider 2 special conditions:
•
Cross-linking and therefore the parallel connection of 2 cans, refer to
•
Current transformer is not in the center of the levels
Therefore, the following calculation must be performed for the upper (C1) and lower quarter (C3).
[dw4tlkbnk-120314-01, 1, en_US]
Figure 7-13
988
= V ⋅ ωC = 249.1 kV ⋅ 2π ⋅ 50 Hz ⋅ 2.81 μF = 219.9 A
C Ph. fund.
Quarters of the Capacitor Bank
Figure 7-11
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017