Fundamentals of Electricity



Distribution Transformers

Electric power leaves the distribution substation with voltage ranging typically between 4,000 and 36,000 volts. This is still, of course, too high for most typical uses, such as homes, businesses, and even small industrial users. The device used to step this voltage down to service voltage is yet another transformer, the distribution transformer.

Distribution Transformers PictureDistribution transformers operate just like large transformers in a distribution substation. The transformer steps the voltage down to the service voltage required by the particular customer. A normal residential service utilizes two separate voltages, 120 and 240 volts. Several residential services are generally run from one distribution transformer. They are sized to meet the needs of the total load of all of the customers connected to it.

Businesses and industrial plants generally do not share transformers with other customers and require larger transformers depending on the type and amount of electrical equipment.

Large power users involving big motors such as heavy manufacturing companies frequently use service voltages higher than 240 volts to reduce the size and cost of their electrical equipment. Most industrial facilities utilize 480 volts but some may require primary line voltages due to very large motors or high energy processing needs.