Capacitor Bank: Learn the Purpose, Cost, and Lead Time to Procure

Capacitor bank
Capacitors in an outdoor rack

Purpose of capacitor bank

Capacitors consume active power and release reactive power. They also present a low impedance to harmonics; in other words, they attract harmonic frequencies. Thus, they are installed in substations to:

  • Correct power factor, consequently minimizes voltage drop at the load end, by injecting reactive volt-amp a.k.a. VARs.
Capacitor bank
Capacitor bank implemented at extra-high-voltage. Image credit: Mead substation – Western Area Power
  • Minimize voltage fluctuations, typically generated near industrial facilities, using harmonic filter banks – improving power quality in the process.
  • Capacitors are an integral piece of Flexible AC Transmission (FACT) device. Some of the FACT devices are:
    1. Static Var Compensator: Used to provide reactive power support (either consume VARS using inductors or release VARs using capacitors – each device plugged into the circuit using thyristor valves) and to filter out harmonics
    2. Series capacitors on high voltage transmission line: Used to maximize power flow on the line by consuming lagging VARs, improve the steady-state and dynamic stability of the power system (by preventing the generators from operating at the maximum allowable power angle. Learn more)
Capacitor Bank: Learn the Purpose, Cost, and Lead Time to Procure 1
Static VAR Compensator. It’s not one piece of equipment, it’s a combination of inductors, capacitors, power electronics, switching devices, transformer, etc. Image credit: Alstom Grid.
Thyristor Controller Series Capacitor
Thyristor Controlled Series Capacitor. Image credit: Alstom grid.

Cost of capacitor bank

Cost depends on the MVAR rating and whether it is an indoor or outdoor unit.

  • 12kV 4MVAR capacitor in a metal-clad switchgear: ~$70,000
  • 34.5kV 10.8MVAR capacitor in a metal-clad switchgear: ~$170,000
  • 69kV 14.4MVAR capacitor fuseless outdoor type: ~$75,000
  • 138kV 65MVAR capacitor fuseless outdoor type: ~$180,000
  • 230kV 100MVAR capacitor fuseless outdoor type: ~$250,000
  • 345kV 150MVAR capacitor fuseless outdoor type: ~$400,000
  • 500kV 230MVAR capacitor fuseless outdoor type: ~$700,000

Lead time to procure capacitor bank

~25 weeks

Information on cost and lead time is for your general knowledge only. Contact vendor with your equipment specifications for actual figures.

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Capacitor Bank: Learn the Purpose, Cost, and Lead Time to Procure 2

Substation Major Equipment

It’s only stupid-simple, let’s begin.

What’s the purpose of a conventional power transformer?
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You are building an interconnect station, tying wind farm generation to the power grid. At the substation, the sources are tied through a tie-breaker. Which device would you install to make sure the sources are synchronized?
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In a distribution substation, the available ground-fault current on the low side of the step-down transformer is excessive, over-dutying the switching equipment. What is your cost-effective solution to reducing the fault current?
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Which combination of devices would you use to implement power line carrier?
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A transformer develops an internal fault. Which device would you install on the transformer high-side to interrupt fault current?
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For which event should a surge arrester operate? Check all that apply.
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An industrial facility is plagued with voltage flicker (due to harmonics) and poor power factor at the service entrance. Which device would you install to fix both issues?
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Your score is

The average score is 40%

Aleen Mohammed

Aleen Mohammed

Registered Professional Engineer | MSEE
Skillset: Substation Design | Power System Studies | Arc Flash Study
DISCLAIMER: ALL VIEWS EXPRESSED IN THIS ARTICLE ARE MINE ALONE.

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