Inductor: Learn the Purpose, Cost, and Lead Time to Procure

By / May 29, 2020 / 2 minutes of reading
Inductor
Current limiting inductor
Table Of Contents

Purpose of inductor

An inductor prevents sudden change in current magnitude. It is installed in substations to:

  • Limit ground fault current entering the power system through transformer neutral. Read more.
Neutral ground inductor to limit ground fault current
Neutral ground inductor to limit ground fault current
  • Limit in-rush currents associated with the energization of capacitor banks.
Current limiting inductors in a substation - used to limit inrush current from switching capacitors.
Current limiting inductors in a substation – used to limit inrush current from switching capacitors. Image credit: FirstEnergy – Toledo Edison – Midway substation.
  • Limit all variations of fault current 3-ph, L-G, L-L-G, etc. when tied in series on a line.
Current limiting series reactor
Current limiting series reactor. Image credit: Trench Group
230kV air core reactors
230kV air-core reactors shown here. It limits the fault current contribution from one bus section to the other. Because the electromagnetic field is unconfined, they are strategically installed in a triangle pattern to cancel out the stray magnetic fields. Image credit: WAPA – Mead substation.
  • On extremely long EHV transmission lines, the Ferranti effect is prominent. An inductor tapped off the t-line negates this effect (the leading vars generated on the long line is consumed by a shunt inductor.)

Cost of inductor:

  • 15kV 800A neutral air core inductor (1 unit): ~$5,000
  • 15kV 450A series air core inductor (3 units): ~$15,000
  • 34kV 1000A series air core inductor (3 units): ~$60,000
  • 138kV 600A series air core inductor (3 units): ~$60,000
  • 345kV 120,000KVAR shunt air core inductor (3 units): ~$150,000

Lead time to procure inductor:

  • ~20 weeks for medium voltage units
  • ~30 weeks for HV & EHV units

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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Inductor: Learn the Purpose, Cost, and Lead Time to Procure 1

Substation Major Equipment

It’s only stupid-simple, let’s begin.

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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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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What’s the purpose of a conventional power transformer?
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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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