Compact Substation Types: European Kiosk vs American Box Type
A compact substation is bought as one package: medium voltage switchgear, a distribution transformer and the low voltage panel, wired and routine tested in a single enclosure that arrives on a base frame. The first decision is not the kVA rating. It is which family of enclosure you are specifying, because that fixes the MV connection style, the clearance you leave on site, and what the utility will accept at commissioning.
Two families cover most enquiries, usually named after the markets that shaped them: the European type kiosk and the American box type. They are not interchangeable, and a quotation written for one cannot be turned into the other by changing the transformer inside it.
What both types have in common
In both designs the transformer, the MV switching device and the LV board leave the factory assembled, wired and tested as a package rather than as three separate purchases. Site civil work shrinks, protection settings are coordinated by one supplier, and the unit is lifted onto its foundation in one operation.
- One enclosure, one set of drawings, one delivery
- Factory wiring and routine tests before shipment
- A single point of responsibility for protection coordination
Both are prefabricated assemblies and are designed to comply with IEC 62271-202 as applicable to the order, with the transformer inside designed to comply with IEC 60076.
European type: the metal-enclosed kiosk
The European type is a small building in steel or concrete, normally divided into three compartments: MV switchgear, transformer, and LV distribution. Access is from the front, through doors sized for the equipment, and larger units are walk-in so that maintenance can be done inside rather than in the rain.
The defining feature is the MV arrangement. A European kiosk almost always contains a ring main unit, so the MV cable enters from below, loops through the switchgear and continues to the next substation on the ring. Two cables per way, switching on both, and an earthing switch that can be closed for work on the cable. That is what makes the design suit a distribution network with several substations fed in series, which is how most 11 kV, 22 kV and 33 kV networks in Europe, the Middle East, Asia and Africa are built. See the European type compact substations we build for that arrangement.
The cost of the kiosk is not only the enclosure. It is a structure, so it needs a concrete plinth, a door swing kept clear, and a paint system that survives the site rather than one that chalkes over in a coastal yard.
American box type: pad-mounted and tamper resistant
The American box type is a low profile steel enclosure bolted to a concrete pad, with no walk-in space at all. Everything is reached from outside through doors that lock with a utility padlock bar. The design assumes the public walks past it: it stands in parking areas, along streets, in residential compounds, and it has to be tamper resistant rather than merely closed.
The MV side is radial, not ring main. Cable is terminated in loadbreak elbows onto a dead-front arrangement, so live parts are not exposed when a door is opened. Inside, the transformer and usually a small LV compartment share the box, and the LV service leaves underground through a duct. This is the pattern that dominates North America and much of the 60 Hz export market, and it is why our American box type substations are built around dead-front MV hardware and locked enclosures.
The differences that decide the order
| Aspect | European type kiosk | American box type |
|---|---|---|
| Enclosure | Steel or concrete kiosk, often walk-in | Low profile steel box on a pad, no walk-in |
| MV switching | Ring main unit, two cables per way | Radial feed, loadbreak elbows, dead-front |
| Access | Front doors, space to work inside | Locked doors from outside, padlock bar |
| Public exposure | Normally fenced or in a plant area | Designed to stand in public areas |
| LV panel | Own compartment, room for many ways | Small compartment, limited ways |
| Foundation | Concrete plinth with door clearance | Flat concrete pad, cable trench on one side |
| Typical markets | Europe, Middle East, Asia, Africa, 50 Hz | North America and 60 Hz export designs |
How to choose between them
Four questions normally settle it before any technical comparison starts.
- Does the utility require ring main switching? If yes, it is a European kiosk; a pad-mounted box cannot express a ring.
- Does the public have access to the unit? If yes, prefer the pad-mounted box and its locked, dead-front construction.
- Must maintenance happen indoors, or is the site remote and hot? A walk-in kiosk earns its civil work there.
- Is the supply 60 Hz on an ANSI-based standard? Then enclosure, elbows and transformer follow that standard, not IEC.
There is a fifth, less obvious test: whether the LV panel physically fits. Outgoing current sets the busbar and the number of ways, and it comes from the transformer rating and the LV voltage:
I = S / (√3 × V), with S in VA and V the line-to-line LV voltage.
For a 1,000 kVA transformer at 400 V that is 1,000,000 / (1.732 × 400) = 1,443 A. A board at that rating needs several 400 A to 630 A ways plus a main incomer, and it does not fit the small LV compartment of a pad-mounted box. The LV requirement alone then pushes the design to a kiosk, even where the MV network would have taken a pad-mounted unit.
Where the choice is still open, compare the two against the same load list rather than against catalogue text. The compact substation range is organised by enclosure family for that comparison, and the capacity selection guide covers the sizing step before it.
What to state in the enquiry
A quotation is only as good as the input. These are the items that change the design, not just the price:
- Voltage ratio, for example 22 kV to 400/230 V, and the frequency
- Transformer rating and the cooling class required at that rating
- MV arrangement: ring main, radial, number of ways, and whether an RMU is needed
- LV outgoing ways and their current ratings, plus metering requirements
- IP rating and the corrosion class for the site
- Maximum ambient temperature and site altitude
- The utility or national standard the assembly must satisfy
- Site access for delivery, and whether a crane can reach the foundation
Standard delivery is 30 days and the warranty is 2 years. If the site is coastal, say so at enquiry stage, because enclosure finish and IP rating are decided early.
Questions buyers ask
What is the difference between European and American type compact substations?
The European type is a kiosk, often walk-in, built around a ring main unit with two MV cables per way and a separate LV compartment. The American box type is a low profile pad-mounted enclosure with radial MV feed through loadbreak elbows and locked doors, built to stand in public areas.
Which type is cheaper?
They are not directly comparable, because the cost sits in different places. The pad-mounted box saves civil work and enclosure volume but needs utility-compliant MV hardware. The kiosk needs a plinth and more steel, and in exchange carries a larger LV panel and gives indoor access. Compare both against the same load list and utility requirements.
Can an American box type be supplied for 50 Hz?
The enclosure can, but the equipment inside cannot be carried over unchanged. Transformer core and winding design, and the MV and LV devices, all follow the system frequency and the local standard. State which frequency and utility standard apply, and the assembly is designed to comply with them as applicable to the order.
Does a compact substation need a concrete foundation?
Yes, in both families. The kiosk needs a plinth with a clear door swing and usually a cable trench. The pad-mounted box needs a flat pad with the cable trench on the service side. The foundation drawing is issued with the approval drawings, so the civil contractor can review it before the plinth is poured.
How much capacity can go into one enclosure?
It depends on what fits and what can be shipped, so it is confirmed per project. The transformer inside is drawn from the distribution ranges we build for pad-mounted and oil immersed units. Send the rating and the LV way count and we will confirm what fits in one box.
Send us the specification
Rating, primary and secondary voltage, frequency, quantity and the application. We answer within one working day.
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