Cast Resin Dry-Type Transformer

It follows the installation position and the fire-protection conditions. A dry-type unit is solid-insulated and indoor, can be placed directly at the load centre, and needs no oil pit, oil sump or oil fire-protection system, which favours damp environments and underground substations; its low-temperature limit in service is −5 °C. An oil-immersed unit can be installed outdoors, goes down to −25 °C, and at the same capacity has lower no-load loss and usually a lower unit price. Most transformers inside a prefabricated power module are dry-type, precisely because no oil pit is provided inside the module.

Voltage, capacity steps, mounting dimensions and low-voltage terminals are identical; the difference sits in no-load loss — at 630 kVA it falls step by step from 1340 W at SC(ZB)10 to 965 W at SC(ZB)13. Load loss drops once, at SC(ZB)13, from 5960 W to 5365 W, and does not move again. No-load loss is consumed all year without a break while load loss follows the load factor, so a higher generation pays back sooner where annual utilisation hours are low. SCB14 and SCB18 are two later generations whose values are confirmed per project. Send the annual running hours, the average load factor and the tariff and the break-even generation can be calculated.

Not as a continuous duty. That margin is the short-time capability with forced-air cooling in service, and it is typically used for transfers during maintenance, seasonal peaks, or temporary duty when a transformer in parallel is out of service. Continuous full-load operation should be sized on rated capacity; do not use the overload capability to reduce the capacity chosen. The permitted duration depends on winding temperature rise, ambient temperature and the load curve, and is calculated against project conditions.

No. Solid insulation takes up no moisture, the transformer operates at 100% humidity, and it can be put into service after a shutdown with no pre-drying. The difference against an oil-immersed unit shows most clearly on seasonally idle installations, standby transformers and coastal projects.

Separate 8.0% impedance rows exist at 1600, 2000 and 2500 kVA, for cases where the short-circuit current on the low-voltage side has to be brought down — usually where the breaking capacity of the low-voltage switchgear or the dynamic strength of the busbar is the limit. The price is higher load loss (1600 kVA goes from 11730 W to 12960 W) and poorer voltage regulation. Check the expected low-voltage short-circuit current and the switchgear ratings before choosing them.

On selection-stage estimates: no-load loss rises by about 10%, load loss by about 6% and weight by about 100 kg; where the tap changer is arranged at the side the lateral dimension grows by about 650 mm, and where it is arranged at the front the frontal dimension grows by about 750 mm. The two directions are alternatives and the choice bears directly on the clear aisle width inside the module or the substation, so it belongs in the layout drawing stage. Final dimensions follow the configuration.

Yes. Where the transformer travels with the module, the prefabricated power module line takes on the enclosure, the internal arrangement, the foundation fixing and the ventilation design, and the transformer leaves the works as equipment inside it; entry and exit directions, cable support levels and the clear width of maintenance aisles are all settled once at the layout drawing stage, leaving only the connection on site. Supply of the transformer on its own is equally possible.

Against the sound level for the chosen capacity and loss generation: at 630 kVA it is 49 dB for SC(ZB)10–11 and 46 dB for SC(ZB)12–13. That is the sound pressure level of the equipment itself; the level actually reaching the site boundary or a sensitive receiver also depends on installation position, room acoustics and distance attenuation, and is calculated separately per project. Fan noise is added on top once the fans are running.