Substation Transformers

These ruggedized transformers are ideal for substation yards and power distribution line-ups.

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Transformer Specifications

kVA: 300 – 160,000 kVA

Maddox’s liquid-filled distribution substation, and power-class substation transformers are designed, built, and tested in accordance with the highest industry standards including NEMA, ANSI C.57, DOE, and IEEE as applicable. With a range of customizable features, Maddox substations can be configured to maximize performance, minimize potential arc flash exposure, and address environmental concerns. All designs can be supplied with full or partial length air terminal chambers to make installation easy.

Voltage: up to 230 kV

Standard Features

Type II non-PCB mineral oil (ONAN)
High-grade silicon-steel core
Aluminum windings (distribution class)
On-load tap changer
Reinforced carbon steel tank
Lifting lugs
Externally clamped high & low-voltage bushings
Pressure relief valve
Pressure vacuum gauge
Liquid temp gauge
Liquid level gauge
Drain & sample valve
Schrader valve
Ground pads/lugs
Nitrogen blanket
65 degree C rise

Optional Upgrades

Environmentally friendly, high fire-point FR3 oil (KNAN)
Copper windings
On-load tap changer
Stainless steel tank
Gauges with contacts
Auxiliary control cabinet
Winding temperature indicator
Fan package (ONAN/ONAF)
Lid-mounted pressure relief device
Sudden pressure relay
Lightning arresters
55/65 degree C rise
Step-up solar & wind duty designs
Electrostatic shielding
K-rated design
Primary load-interrupter switch

Available Certifications

Maddox substation transformers are available with UL, CSA, or ETL certifications.

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Price and lead time today

3 Year Warranty

Backed by US-based support

USA Options

Made-in-America available

Power Projects of Every Size with Reliable Substations

Maddox builds substations ranging from 300 kVA to 160 MVA,
providing reliable power to projects of every size.

Distribution Substation

kVA: 300kVA–5000 kVA

Voltage: up to 35kV

Medium-voltage substations for stepping down and distributing power to facility or feeder-level loads.

Powerclass Substation

kVA: Up to 160 MVA

Voltage: 69kV–230kV

High-voltage substations for large-scale load interconnection and bulk power transformation.

Hit Your Lead Time with Stock and Custom Options

Maddox keeps substation transformers in stock for fast deliveries and builds custom ones with some of the best lead times in the industry.

Stock

Hit project deadlines with common kVA sizes and voltages, in stock and ready to ship.

Custom

Build exactly what you need with extensive transformer customizations available.

Remanufactured

Save time and money with remanufactured substations, rebuilt to like-new standards.

Projects Powered by Maddox Substations

Maddox substation transformers provide reliable power to critical projects across the United States.

Competitive pricing, always the most inventory, and exceptional after sales support. They are my "go to" option for transformers

David D.

This is my 5th order from Maddox. Always knowledgeable and helpful. Every transformer I have purchased has worked perfectly.

Jason W.

They have stock when others don't and are quick to ship and fill their orders. VERY THANKFUL we found them.

Mike A.

The transformer I ordered was delivered onsite at our project in two business days. Great service!

Jerome T.

Great company easy to deal with. Every transformer I buy will be from Maddox.

Austin M.

First time purchasing from Maddox. Was very easy and we are pleased with the results of our purchase.

Chris O.

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Fill out the form and we will get back to you as soon as possible. Our average response time during business hours is 30 minutes.

Meet Any Spec with Extensive Customizations

Meet your exact spec with customized transformers designed, built, and tested in accordance with the highest industry standards including NEMA, ANSI, DOE, and IEEE as applicable.

On-Load
Tap Changer

On-load tap changes enable you to adjust voltage without taking the transformer offline, which helps keep power steady and avoids unnecessary downtime during normal operation.

Pressure
Relief Device

Pressure relief devices release excess internal pressure if something goes wrong inside the tank, protecting the transformer from damage and improving site safety.

Fan Package
(ONAN/ONAF)

Fan packages cool the transformer based on load demands, using natural cooling under normal loads and forced-air cooling when the transformer is carrying heavier loads.

Primary Load-
Interrupter Switch

Primary load-interrupter switches give crews a safe way to disconnect and isolate the transformer under load, making maintenance easier and protecting the rest of the system.

FR3 Oil

FR3 oil is a biodegradable alternative to mineral oil that offers better fire safety, longer insulation life for extended transformer performance, and reduced environmental risk.

Gauges with
Contacts

Gauges track key transformer conditions like oil level, temperature, and pressure, sending alarms when readings move out of range so issues can be caught early.

Frequently Asked Questions

Which cooling class do Maddox substation transformers feature?

While standard substation designs feature ONAN, additional cooling classes such as ONAN/ONAF or KNAN are available upon request. Learn about transformer cooling classes here.

Can Maddox close couple substation transformers with switchgear?

Yes, Maddox can close couple metal-enclosed switchgear to a substation transformer upon request. Learn more about switchgear and close coupled designs here.

Are Maddox remanufactured substation transformers reliable?

Yes, Maddox remanufactured medium voltage dry-type transformers are tested in accordance with NEMA, ANSI, DOE, and IEEE standards as applicable. Learn about remanufactured transformers here.

Can I return or exchange a Maddox substation transformer?

Yes, substation transformers may be eligible for return or exchange within six months of shipment date. Terms and conditions apply. Learn about the Maddox return and exchange policy here.

Are Maddox substation transformers BABA compliant?

Many Maddox products are made in the USA, but not all. Our goal is to provide the majority of our products domestically, while leveraging global supply as needed. We specify “American Made” on our quotes when applicable. Maddox can also provide substations to meet “Build America, Buy America” requirements. Ask for BABA in your quote and learn more about BABA here.

Substation Transformers

Transformer Specifications

kVA: 300 – 160,000 kVA

Voltage: up to 230 kV

Standard Features

Optional Upgrades

Available Certifications

Same Day Quotes

3 Year Warranty

USA Options

Power Projects of Every Size with Reliable Substations

Distribution Substation

Powerclass Substation

Hit Your Lead Time with Stock and Custom Options

Stock

Custom

Remanufactured

Projects Powered by Maddox Substations

Get a Quote in Minutes

Meet Any Spec with Extensive Customizations

Frequently Asked Questions

Cooling Class

Close Coupling

Remanufactured

Returns & Exchanges

American Made