Four questions that come up in every selection meeting, answered with criteria rather than adjectives.
The difference between these models is loss level, and loss ends up on the electricity bill. No-load loss is fixed the moment the unit is energised — 8,760 hours a year. Load loss rises with the square of the load, so it follows your actual load curve.
The arithmetic: annual loss energy ≈ no-load loss × 8,760 h + load loss × equivalent full-load hours, multiplied by the local tariff. A model with lower no-load loss costs more at the front and pays back on lightly loaded duty — night-heavy loads, PV back-feed, rural feeders. For continuous full-load duty the picture reverses.
For tenders scored on efficiency, the grade is judged against GB 20052 using measured values in a third-party report, not catalogue figures. Every unit ships with its routine test report.
Conclusion: optimise total life-cycle cost, not the highest efficiency class. Give us your annual operating hours and tariff and we will price the five-year difference across three models. Related: oil-immersed S11/S13/S20/S22
The first question is not kVA, it is where the unit will stand.
1. Location. Basement, intermediate floor, occupied building: dry type. Dedicated substation room or outdoors: oil-immersed. 2. Fire requirements. Dry type is oil-free and flame retardant, which is easier to approve. 3. Rating versus cost. The larger the rating, the stronger the cost advantage of oil-immersed. 4. Overload and cooling. Oil-immersed handles overload better; dry type is air-cooled, so ventilation must be calculated for enclosed rooms. 5. Maintenance. Dry type is essentially maintenance-free; oil-immersed needs periodic oil and insulation checks.
The classic mistake is choosing oil-immersed on price, then failing fire approval for a basement — the redesign costs far more than the difference. Related: dry-type SCB10–SCB18 · oil-immersed
Re-labelling a 50 Hz drawing for a 60 Hz market is the most common way to fail. Higher frequency raises core loss and temperature rise, so flux density and turns must be recalculated.
1. Frequency and rated voltage. Single 60 Hz or dual 50/60 Hz; LV side at 0.4 kV, 0.48 kV or the local standard. 2. Insulation class and temperature rise. Keep margin at 60 Hz and write both into the technical agreement — "to national standard" is not enough. 3. Standard and test scope. IEC 60076 or ANSI C57, routine test items, and whether third-party witnessing is required — all before quotation.
Three items that get missed: nameplate content and position, seaworthy packing, and the document set (datasheet, test report, packing list, O&M manual). Related: 60 Hz export builds
When a substation does not fit on site, it is almost never the equipment. 1. Foundation and level. Flatness, cast-in openings and trench direction against the general arrangement. 2. Cable entry. Top, bottom or side entry determines internal layout. 3. Operating and maintenance access. Door swing to 90° with clear passage — check walls and pipe racks. 4. Earthing. Grid entry point, resistance value, equipotential bonding of enclosure and cubicles. 5. Ventilation and lifting. Louvre area for enclosed rooms, lifting points and crane radius.
Write all five into the technical agreement; it is cheaper than fixing them on site. Related: European / American compact substations
Send the single-line diagram, rating and voltage. We reply with a configuration and a price.
Send project details →