15kVA-transformer single-phase-transformer power-distribution-transformer oil-immersed-transformer small-single-phase-transformer Wishpower pole-mounted-transformer 167kVA-distribution unit transformer-manufacturer box-transformer distribution-cabinet-transformer pad-mounted-transformer urban-power-transformer customized-transformer-supplier aPowerTransformerCostHowMuch 25kVA-transformer rural-utility-transformer oil-filled-transformer transformer-substation prefabricated-power-station modular-transformer-unit smart-grid power-distribution-system transformer-cost power-equipment custom-transformer 50kVA-transformer compact-distribution-transformer electric-utility-equipment PowerTransformers