Substation Transformers
These ruggedized transformers are ideal for substation yards and power distribution line-ups.
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)
- 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.
Same Day Quotes
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: 300–5000 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: 69–230 kV
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.
Get a Quote in Minutes
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 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 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 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 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
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 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
Cooling Class
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.
Close Coupling
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.
Remanufactured
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.
Returns & Exchanges
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.
American Made
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.