GE C70, Instruction Manual

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GE Multilin C70 Capacitor Bank Protection and Control System 9-1
9 APPLICATION OF SETTINGS 9.1 ARRANGEMENT OF SHUNT CAPACITOR BANKS
9
9 APPLICATION OF SETTINGS 9.1ARRANGEMENT OF SHUNT CAPACITOR BANKS 9.1.1 OVERVIEW
The appropriate protection is dependent on the capacitor bank type, configuration, CTs and VTs location and connections.
IEEE Standard C37.99-2000:
Guide for Protection of Shunt Capacitor Banks specifies methods used for protecting different
types of banks.
There are four types of arrangements and individual capacitors connections used to form a capacitor bank.
• Externally fused capacitors.
• Internally fused capacitors.
• Fuseless capacitors.
• Unfused capacitors.
These arrangements are described in the following sections.
9.1.2 EXTERNALLY FUSED CAPACITORS
An individual fuse, externally mounted between the capacitor unit and the capacitor bank fuse bus, protects each capacitor
unit. The capacitor unit can be designed for a relatively high voltage since the external fuse is capable of interrupting a high-
voltage fault. However, the kvar rating of the individual capacitor unit is usually smaller because a minimum number of par-
allel units are required to limit the voltage rise on remaining units and thus allow the bank to remain in service with a capac-
itor can out of service. A capacitor bank using fused capacitors is configured using one or more series groups of parallel-
connected capacitor units per-phase, as shown below.
Figure 9–1: EXTERNALLY FUSED SHUNT CAPACITOR BANK AND CAPACITOR UNIT
9.1.3 INTERNALLY FUSED CAPACITORS
Each capacitor element is fused inside the capacitor unit. A simplified fuse is a piece of wire sized to melt under the fault
current, and encapsulated in a wrapper able to withstand the heat produced by the arc during the current interruption. Upon
the capacitor failure, the fuse removes the affected element only. The other elements, connected in parallel in the same
group, remain in service but with a slightly higher voltage across them.
The following figure illustrates a typical capacitor bank utilizing internally fused capacitor units. In general, banks employing
internally fused capacitor units are configured with fewer capacitor units in parallel, and more series groups of units than are
used in banks employing externally fused capacitor units. The capacitor units are built larger because the entire unit is not
expected to fail.
phase
A
phase
B
phase
C
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