An overview of Large Power Transformer - physical characteristics, costs and pricing
An overview of Large Power Transformer – physical characteristics, costs and pricing (photo courtesy of the ABB Facebook Page – depicts an ABB engineer working atop an ABB Transformer)

Tailored to customers’ specifications

An LPT (Large Power Transformer) is a large, custom-built piece of equipment that is a critical component of the bulk transmission grid. Because LPTs are very expensive and tailored to customers’ specifications, they are usually neither interchangeable with each other nor produced for extensive spare inventories.

According to an industry source, approximately 1.3 transformers are produced for each transformer design.

Figure 1 illustrates a standard core-type LPT and its major internal components. Although LPTs come in a wide variety of sizes and configurations, they consist of two main active parts:

  1. The core, which is made of high-permeability, grain-oriented, silicon electrical steel, layered in pieces; and
  2. Windings, which are made of copper conductors wound around the core, providing electrical input and output.

Two basic configurations of core and windings exist: the core form and the shell form.

ABB's TrafoStar design
Figure 1 – The ABB’s TrafoStar design used for core type transformers has a circular shaped core limb, surrounded by concentrically arranged, cylinder shaped windings.

In the usual shell-type power transformer, both primary and secondary are on one leg and are surrounded by the core, whereas in a core-type power transformer, cylindrical windings cover the core legs. Shell form LPTs typically use more electrical steel for the core and are more resilient to short-circuit in the transmission systems and are frequently used in industrial applications.

The core and windings are contained in a rectangular, mechanical frame called the “tank.”

Other parts include transformer bushings, which connect LPTs to transmission lines, as well as tap changers, power cable connectors, gas-operated relays, thermometers, relief devices, dehydrating breathers, oil level indicators, and other controls.

Power transformer costs and pricing vary by manufacturer, by market condition, and by location of the manufacturing facility.

In 2010, the approximate cost of an LPT with an MVA rating between 75 MVA and 500 MVA was estimated to range from $2 to $7.5 million in the United States. However, these estimates were Free on Board (FOB) factory costs, exclusive of transportation, installation, and other associated expenses, which generally add 25 to 30 percent to the total cost (see Table 1 below).

Raw materials, particularly copper and electrical steel, are a significant factor in power transformer prices.

Transportation is also an important element of the total LPT cost, because an LPT can weigh as much as 410 tons (820,000 lb) and often requires long-distance transport.

Estimated Magnitude of Large Power Transformers in 2011
Table 1 – Estimated Magnitude of Large Power Transformers in 2011

Note: Prices are FOB factory and do not include taxes, transportation, special features and accessories, special testing (short-circuit, etc.), insulating oil, field installation, and/or optional services. The total installed cost is estimated to be about 25–30 percent higher.

Source: NERC Special Report: Spare Equipment Database System, 2011

LPTs require substantial capital and a long-lead time (in excess of six months) to manufacture, and its production requires large crane capacities, ample floor space, and adequate testing and drying equipment.

Large Power transformers and shunt reactors (VIDEO)

Cant see this video? Click here to watch it on Youtube.


Reference: Large power transformers and the U.S. Electric Grid – Infrastructure Security and Energy Restoration Office of Electricity Delivery and Energy Reliability U.S. Department of Energy

About Author //


Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears.Professional in AutoCAD programming and web-design.Present on


  1. Ramiro Gutierrez
    Jun 27, 2015

    Great articule

  2. Bruce Miller
    Jun 25, 2015

    You have not addressed toroids, nor Jakob’s ladder voltage multipliers? Large current switching FET’s ? In conjunction with HVDC long distance transmission? Also would like to hear something on Hysteresis and heat losses in transformers and Capacitive pf phase corrections?more on Electrical Storage systems for Solar Wave Wind Tidal renewable systems?

  3. Bruce Miller
    Jun 25, 2015

    Can higher frequencies and higher voltages (consistent with recent materials advances) help us arrive at smaller, lighter, more efficient transformers? Can recent solid state advances do away with some transformers entirely? Will a Solar / LED D.C. world for lighting alone ever replace the current very wasteful 120 volt/incandescent systems in common use? Will super capacitors capable of very much higher voltages ever replace the Li battery systems in electric cars?

  4. Win Oo
    Jan 08, 2014

    We are doing in this kind of power transmission business in Myanmar. So that I am looking forward to coordinate to do this industry business in Myanmar together for long terms.

  5. Win Oo
    Jan 08, 2014

    We would like to be a member of yours.

  6. komichi
    Jan 05, 2014

    Dear EDVARD; Thank you very very much our teacher; really you you help many engineers; students; tech; …etc around the world with your publications; you are doing a GREAT work; again i thank you our friend; and i wish that the new year 2014 will bring to you what you are wishing and wht you hope.

  7. Sheikh Basheer Ahmed
    Jan 03, 2014

    Good informative publication … Thankyou.

    Dec 31, 2013


Leave a Comment

Tell us what you're thinking... we care about your opinion!
and oh, not to forget - if you want a picture to show with your comment, go get a free Gravatar!