Small power transformers are distribution transformers from 5 to 40 mva with a maximum service voltage of 145 kv. They are used as network transformers in distribution networks. This type of transformer is normally a 3-phase application and designed according to national and international standards. The low-voltage windings should be designed as foil or layer windings. The high-voltage windings should use layer or disc execution, including transposed conductors. Normally, the cooling type of small power transformers is onan (oil-natural, air-natural) or onaf (oilnatural, air-forced). The tapping can be designed with no-load or on-load tap changers (nltc or oltc). Bringing the energy safely to the consumer: a basic requirement applicable to all power transformers. However, every single one is unique designed according to individual factors such as voltage, power, climate, system topography, sound level and many more.