Voltage transformer - definition
Voltage transformer - definition
The voltage transformer is an electromagnetic device used in the electric power industry for the proportional conversion of the high voltage in the power grid to a lower voltage that is safe for measurement, protection and control systems. Its main function is to provide galvanic isolation between the high voltage circuits and the low voltage secondary circuits, while allowing the primary voltage value to be accurately represented on a reduced scale.
The operation of a voltage transformer is based on the principle of voltage transformation in the ferromagnetic core, just as in a classical transformer. The mains voltage flows in the primary winding, while a proportional voltage is induced in the secondary winding, according to the established transformer. Typical secondary voltages are standardised, most often 100 V or 110 V, which facilitates integration with measuring devices and protection relays.
Depending on the application, voltage transformers can be manufactured as dry, oil, gas (SF₆) or capacitive, especially for very high voltages. The design and parameters of these devices must ensure high voltage reproduction accuracy and resistance to disturbances and overloads. The accuracy classes of the transformers are defined in standards and their selection depends on the requirements of the specific application, e.g. whether it is a precise measurement or only the detection of fault conditions.
Due to its functions, the voltage transformer is an indispensable component of power protection and automation systems, enabling safe voltage monitoring in transmission and distribution networks, both in high-voltage substations and in industrial installations.
Voltmeters for use with a voltage transformer
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