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Power vs. distribution transformers
Both step voltage up or down, but they are different products, built in different factories and bought in different ways. Knowing where the line falls helps you look in the right places.
The short answer
Distribution transformers serve end customers at the edge of the grid: pole-mounted units on residential streets, pad-mounted units outside commercial buildings. Power transformers sit higher in the system, at substations and generating plants, where they move power between transmission and sub-transmission voltages or connect a plant to the grid.
There is no single industry-wide cutoff, but distribution transformers are typically below about 10 MVA, and power transformers cover the range above that, up to well over 1,000 MVA.
Rating and voltage
Distribution transformers usually take a primary voltage in the medium-voltage range and step it down to the voltages used in homes and buildings. Power transformers work at transmission voltages and carry much larger loads. Their MVA rating is often stated at several cooling stages, such as ONAN, ONAF and ODAF.
Higher voltages require higher insulation levels, so BIL requirements are much greater for power transformers.
Design and manufacturing
Distribution transformers are largely standardized and built in volume. Many buyers order the same design repeatedly, and some are held in stock by suppliers.
Power transformers are engineered to order. Impedance, vector group, tap changers (OLTC or DETC), cooling, sound level and footprint are set for each project. Large units are tested individually at the factory, often with the buyer's engineers present for the factory acceptance test. They are also very heavy, which makes transport a significant part of the project.
How sourcing differs
Distribution transformers are usually bought through distributors, framework agreements or direct from high-volume manufacturers. Shortages show up as longer quotes, but there are many suppliers.
Power transformers come from a much smaller group of factories, and each order competes for a production slot. When those slots are booked years ahead, the options are a new order, a released slot or an existing unit. See large and medium power transformers and lead times and prices.
Units in between
Substation transformers in the low tens of MVA, and pad-mounted units used at solar and storage collector systems, sit near the boundary. They may come from either type of factory. When a project needs units in this range, it is worth checking both channels.
Which one do you need?
If your project connects at transmission voltage, or needs more than a few MVA at one point, you are probably looking for a power transformer or a GSU. If you are unsure, send us your single-line diagram and we will tell you what to look for. Start a search.
Sources
FAQ
Common questions
Where is the line between power and distribution transformers?
There is no single cut-off, but power transformers generally carry higher ratings and voltages and serve transmission and substations, while distribution transformers step voltage down for end users.
Why does the distinction matter when sourcing?
The two are made by different factories, on different schedules, and are sold through different channels, so the search looks different for each.
Do you source distribution transformers?
Our focus is substation-class equipment, including pad-mount units on larger projects. Tell us what you need and we'll say whether it fits our search.
Tell us what you need.
A 15-minute call is usually enough to scope a search.
Contact details coming soon