Power Transformer: Learn the Purpose, Cost, and Lead Time to Procure

Substation Equipment / By / Last Updated on
Power Transformer
Power Transformer
Table Of Contents

Purpose of transformer

Transformers are designed to do one of the following:

  • Step-up voltage; consequently step-down current – enables long-distance transmission by reducing I^2\times R copper losses. Step-ups are found near generating stations.
Step up transformers at a generating station
Step up transformers at a generating station – three transformers and one spare shown.
Step up transformer at the base of a wind turbine.
Step up transformer at the base of a wind turbine. Each turbine gets its own. Image credit: Patrick Finnegan – CC.
  • Step-down voltage; consequently step-up current – enables distribution of power to customers at a safe voltage magnitude. Step-downs are found near load centers and in sub-transmission systems.
Step down transformers at a distribution station
Step down transformers at a distribution station
  • On distribution transformers, when equipped, the load tap changer keeps the secondary voltage constant as the load increases or decreases.
  • The transformer is also designed for special applications such as
    • phase-shifting transformer (pushes more power on the transmission line by varying power-angle \sin\delta – learn more)
    • HVDC converter transformer
    • Static Var Compensator (SVC) transformer (VARs generated by capacitive and inductive elements at medium voltage, you still need a transformer to step-up when tying these elements to the high-voltage grid)
    • grounding zig-zag transformer (provide a path for zero-sequence current in an ungrounded system)
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Cost of transformer

The cost of a power transformer varies significantly based on BIL rating, MVA rating, core design, guaranteed losses requirement, tank design, etc. The prices listed below are for a standard design transformer (i.e., standard sound – core type transformer).

  • Small power transformer with LTC – 10MVA or lower: ~ $600,000
  • Medium power transformer with LTC – 10MVA to 50MVA: ~$800,000
  • Large power transformer with LTC – 50MVA to 100MVA: ~$1,500,000
  • Large power transformer – 100MVA or larger: ~ $2,500,000
  • Specialty phase shifting transformer – 100MVA+: ~$4,000,000
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Lead time to procure transformer

~ 1 year, regardless of MVA rating.

Information on cost and lead-time are rough estimates — contact vendor with your equipment specifications for actual figures.

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

Substation Major Equipment

It’s only stupid-simple, let’s begin.

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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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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For which event should a surge arrester operate? Check all that apply.
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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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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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What’s the purpose of a conventional power transformer?
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Aleen Mohammed

Aleen Mohammed

Registered Professional Engineer | MSEE
Skillset: Substation Design | Power System Studies | Arc Flash Study

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