Miniature Substations South Africa
South Africa’s trusted manufacturer of mini subs and miniature substations since 1998. SANS 780 compliant, ISO 9001:2015 certified. Built in Bloemfontein for utilities, mining, renewables and industry.
Since 1998
27+ years of South African transformer manufacturing
SANS 780
Every unit built to South Africa's transformer standard
ISO 9001:2015
Certified quality management system
5 kVA – 40 MVA
Full transformer range, up to 132 kV
What is a miniature substation?
A miniature substation (also called a mini substation, mini sub or minisub) is a compact, packaged distribution unit that combines a transformer, medium-voltage switchgear and low-voltage distribution into a single weatherproof enclosure. It steps medium-voltage supply — typically 11 kV or 22 kV — down to a usable LV level for end users.
Compared with a traditional brick substation, a miniature substation is faster to install (delivered as a single unit), cheaper to commission, and easier to relocate if site requirements change. In South Africa, mini subs are the standard solution for municipal distribution networks, mine reticulation and large industrial sites.
We design every miniature substation to your specification and manufacture it at our Hamilton, Bloemfontein factory.
Above-ground mini subs
The standard configuration for municipal and utility distribution networks. IP-rated enclosures designed for SA weather conditions.
Underground mini subs
Purpose-built for mining and industrial applications where surface installation isn't practical. Custom IP ratings.
Indoor / packaged
For installation inside plant rooms, factories, data centres. Often paired with dry-type or cast-resin transformers.
For renewables
Collector-point and step-up units for solar PV and wind farms, sized for project MV ratings.
Underground mini substations
Underground miniature substations are one of our most-requested specialist products. South African mining operations rely on underground mini subs to step MV supply down for reticulation deep underground, where space is at a premium and surface installation isn’t an option.
Every underground unit is engineered for the specific mine environment — including IP rating against dust and water ingress, ventilation, corrosion protection, fire-resistant materials, and access for maintenance crews. We also build underground-style enclosures for buried installations in industrial yards, port areas, and renewable energy sites.
Typical underground mini sub specifications:
- Primary voltage: 11 kV or 22 kV
- Secondary voltage: 400 V (or to your spec)
- Capacity: typically 100 kVA to 1,000 kVA
- Enclosure: IP54 or higher; custom IP ratings on request
- Cooling: ONAN standard; ONAF available
- Compliance: SANS 780, ISO 9001:2015
Specifications
Standard build options. Every unit is engineered to spec.
| Parameter | Standard range | Custom options |
|---|---|---|
| Capacity (kVA) | 25 kVA – 5,000 kVA | Up to 5 MVA on request |
| Primary voltage | 11 kV / 22 kV | Up to 33 kV |
| Secondary voltage | 400 V | 230 V, 525 V, custom |
| Cooling type | ONAN (oil-natural air-natural) | ONAF available |
| Enclosure rating | IP54 | IP65 or higher on request |
| Installation | Outdoor (above ground) | Underground, indoor |
| Compliance | SANS 780, ISO 9001:2015 | Custom standards on request |
| Lead time | 8–12 weeks (typical) | Faster on stock units |
Applications across South Africa & SADC
Our miniature substations are installed by utilities, mines and industry across South Africa, Namibia, Botswana, Mozambique, Zambia, Zimbabwe and beyond.
Municipal distribution
City Power, Mangaung, eThekwini, Cape Town
Mining
Surface and underground reticulation
Solar PV farms
Collector points and step-up
Wind farms
Turbine and substation collector units
Industrial & manufacturing
Factories, warehouses, plants
Commercial property
Malls, mixed-use, developments
Data centres
Reliable LV distribution
Public facilities
Hospitals, universities, government
Why choose Free State Transformers as your mini substation supplier
As one of South Africa’s largest mini substation manufacturers, we combine 27 years of in-house design and manufacturing experience with full vertical control of every step — from design through testing and after-sales service.
- 27+ years of design and manufacturing experience (since 1998)
- Locally manufactured in Bloemfontein — shorter lead times than imports
- SANS 780 and ISO 9001:2015 certified
- Full in-house design, manufacture, test, and after-sales repair
- Capability from 25 kVA up to 40 MVA across the broader transformer range
- Supply across SA and SADC: Namibia, Botswana, Mozambique, Zambia, Zimbabwe, Lesotho, Eswatini, DRC
Frequently asked questions
About miniature substations and how we build them.
They’re the same thing. “Miniature substation” is the formal term used in SANS 780 and engineering specifications. “Mini sub” or “minisub” is the common shorthand used by South African electricians, contractors and procurement teams. Some specifiers also use “package substation” or “unitised substation” — also the same product.
Yes. Underground miniature substations are one of our specialist products. We build to your specific mine or site requirements, including custom IP ratings, ventilation, corrosion protection and access design. Capacity typically 100 kVA to 1,000 kVA, primary voltage 11 kV or 22 kV.
All Free State Transformers miniature substations are manufactured to SANS 780, and our quality management system is ISO 9001:2015 certified. We can also manufacture to specific customer or international standards on request.
A well-maintained miniature substation typically delivers 30 to 40 years of service. Service life depends on loading, operating environment, and the quality of routine maintenance — particularly transformer oil testing and switchgear servicing. Our service & repairs division offers transformer oil testing, switchgear maintenance and refurbishment to extend asset life.
Yes. We regularly supply miniature substations into Namibia, Botswana, Mozambique, Zambia, Zimbabwe, Lesotho, Eswatini and the DRC. We handle export documentation and can quote ex-works or delivered to your site.
Price depends on capacity (kVA), voltage class, enclosure rating, and any custom features. For a standard 500 kVA above-ground mini sub, expect a quote turnaround of 48 hours and a typical lead time of 8 to 12 weeks. Contact us with your specifications for an accurate quote.
Get a quote on a miniature substation
Tell us your capacity (kVA), primary and secondary voltage, application, and site location. We’ll come back within 48 hours with a quote and lead time.