GE C70, Instruction Manual

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9-2 C70 Capacitor Bank Protection and Control System GE Multilin
9.1 ARRANGEMENT OF SHUNT CAPACITOR BANKS 9 APPLICATION OF SETTINGS
9
Figure 9–2: INTERNALLY FUSED SHUNT CAPACITOR BANK AND CAPACITOR UNIT
9.1.4 FUSELESS CAPACITORS
Fuseless capacitor bank are typically the most prevalent designs. The capacitor units for fuseless capacitor banks are con-
nected in series strings between phase and neutral. The higher the bank voltage, the more capacitor elements in series.
The expected failure of the capacitor unit element is a short circuit, where the remaining capacitor elements will absorb the
additional voltage. For example, if there are 6 capacitor units in series and each unit has 8 element groups in series there is
a total of 48 element groups in the string. If one capacitor element fails, this element is shorted and the voltage across the
remaining elements is 48 / 47 of the previous value, or about 2% higher. The capacitor bank remains in service; however,
successive failures of elements would aggravate the problem and eventually lead to the removal of the bank.
The fuseless design is usually applied for applications at or above 34.5 kV where each string has more than ten elements
in series to ensure the remaining elements do not exceed 110% rating if an element in the string shorts.
Figure 9–3: FUSELESS SHUNT CAPACITOR BANK AND SERIES STRING
9.1.5 UNFUSED CAPACITORS
Contrary to the fuseless configuration, where the units are connected in series, the unfused shunt capacitor bank uses a
series or parallel connection of the capacitor units. The unfused approach would normally be used on banks below 34.5 kV,
where series strings of capacitor units are not practical, or on higher voltage banks with modest parallel energy. This design
does not require as many capacitor units in parallel as an externally fused bank.
phase
A
phase
B
phase
C
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