Voltage transformer is an instrument transformer has the following two functions-Adapting the value of MV voltage on the primary to the characteristics of metering or protection devices by supplying a secondary voltage that is proportional and lower in value.Isolating power circuits from the metering and/or protection circuit.
Why secondary of voltage transformer should not kept open
Composition of voltage/potential transformer
primary winding, a magnetic core, one or several secondary windings, with everything encapsulated in an insulating resin.
Types of voltage/potential transformer
According to connection-phase/phase: primary connected between two phases, phase/earth: primary connected between a phase and the earth.