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

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 – three transformers and one spare shown.

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

On distribution transformers, when equipped, the load tap changer keeps the secondary voltage constant as the load increases or decreases.

Transformer are also designed for special applications such as phase shifting transformer (pushes more power on a t-line by varying power-angle $\sin\delta$ – learn more), HVDC converter transformer, SVC transformer, grounding zig-zag transformer etc.

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.

Small power transformer with LTC ~10MVA or lower: ~ $600,000
Medium power transformer with LTC ~50MVA or lower: ~$1,400,000
Large power transformer ~300MVA or lower: ~ $3,500,000
Large phase shifting speciality transformer: ~$5,000,000

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.

What’s the purpose of a conventional power transformer?

Transform voltage only

Transform voltage and current

Transform power, voltage, and current

For which event should a surge arrester operate? Check all that apply.

Lightning strike

Temporary overvoltage

Phase-to-ground short-circuit

Switching surge

A transformer develops an internal fault. Which device would you install on the transformer high-side to interrupt fault current?

Circuit breaker

Either a breaker or a circuit switcher

Circuit switcher

Disconnect switch

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?

Power transformer

Ideal transformer

Voltage transformer

Current transformer

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?

Install capacitor bank

Voltage regulator

Harmonic filter bank

Which combination of devices would you use to implement power line carrier?

Wave trap, capacitor voltage transformer and line tuner

Wave trap and line tuner

Wavetrap, capacitor coupled voltage transformer, and line tuner

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?

Add current limiting fuses in series on the switchgear

Buy new transformer with higher impedance (%Z)

Add inductor in the transformer neutral

Add series inductors

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The average score is 41%