Different kinds of power transformers are necessary to facilitate the transmission of electricity on different scales. Electricity is generated at electric power plants, and in order for that electricity to become usable by homes and businesses, it must be distributed at appropriate voltages. These voltages vary based on the application of the electricity. When power is first generated at a power plant, it is directed to a high voltage transformer that distributes the electricity to high voltage transmission lines. From those lines the electricity is distributed to other, small transformers, which in turn distribute the electricity to large-scale users of electricity.
These users include industrial operations, large institutions like colleges, large office buildings and many other examples. Those same transformers also distribute electricity to the power lines that are visible along city streets. From there the electricity is distributed to many small, low voltage transformers that distribute electricity in appropriate voltages to residences.
High voltage transformers are built to handle elevated amounts of electrical energy in the range of 600 to 5,000 volts, although custom voltage transformers are available as well. A type of instrument transformer, high voltage transformers are often used for metering and protection in high-voltage circuits and in electrostatic industrial and scientific applications. Because they have the ability to step up primary voltage to a very high voltage, they are often also referred to as power transformers.
High voltage transformers are designed to present negligible load to the supply being measured and to have a precise voltage ratio to accurately step down high voltage. This capability is helpful when equipment, such as that for metering or protective relay, needs to operate at a lower potential.
Due to the high voltage and frequency that it must handle, a high voltage transformer has a significantly different core geometry, winding techniques, and insulation methods than ordinary transformers. For example, factors such as the volts/turn ratings of the secondary wire, insulating material dissipation and corona level must be carefully considered.