Open Rack Capacitor Bank Fusing

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Capacitor banks is merely a grouping of capacitors of the same rating. Shunt capacitor banks are primarily used to improve the power factor in the network. They also improve the voltage stability and reduce network losses. Improving the power factor also means a higher power transmission capability and increased control of the power flow. Today we’ll look at the available options of fusing for open rack cap banks. We’ll learn what is the best solutions for reliability and reduce power loss.

OPEN RACK CAPACITOR BANKS

Open rack capacitor banks are the only choice for shunt capacitor banks at voltages above 40kV and are usually the most economical choice at 34.5kV (compared to the metal enclosed type).

TYPES OF CAPACITOR BANK FUSING

There are 3 different fusing types of capacitors used in open rack shunt capacitor and harmonic filter banks:

Open Rack, Capacitor Bank, Fuseless, Substation

69 kV-27 Mvar, open rack Fuseless capacitor bank low profile, Substation, NY, USA

  • Externally fused type of capacitor bank design is the oldest technology. Each capacitor has an external fuse of either the exposed expulsion type or a sealed current limiting type fuse.

  • Internally fused type of capacitor was pioneered by ABB in the 1970’s, for improved reliability, compared to the older externally fused design. Each capacitor has internal fuses on each element inside the case. It is ideal for harmonic filter banks where minimal loss of capacitance is required to maintain tight tolerances of harmonic tuning.

  • Fuseless type of capacitor bank was developed by Westinghouse in the 1980’s (now ABB), as a lower cost alternative to externally and internally fused capacitor banks, and that offers better reliability than the externally fused design. There are no external or internal fuses on each capacitor unit.

The following table summarizes the pros and cons of each of the capacitor bank fusing types:

Pros and Cons, Capacitor fusing, External Fused, Internally Fused, Fuseless
Capacitor, Fuseless, Internally fused, Birdcaps

Anti-varmint birdcaps and insulating tubing on a fuseless or internally fused capacitor bank. The chance of varmint flashovers is greatly reduced.

External Fuse, Capacitor, Flashover

Birds tangled and electrocuted on an expulsion fuse of an externally fused capacitor bank, caused flashover damages, fuse mis-operations and nuisance tripping of the bank.

Should you have any questions about the design of a capacitor bank, the QVARx team is available to help. QVARx Inc, is an industry leader in the design and manufacturing of mid to high voltage capacitor and harmonic filter systems. Their products are designed and manufactured at their factory in St-Jerome, about 30 mins north from the Montreal airport.