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Voltage Transformers

Voltage transformers on the other hand carry full system voltage but no significant current.  They have a fine wire of many turns on the primary winding (very high resistance and inductance) connected between the phase conductor and earth, and a secondary winding of only a few turns.

The full system voltage phase to earth is applied to the primary winding and the number of turns in the primary is arranged such that the voltage at the secondary terminals is 110 volts.

The current in the primary winding is extremely small because of the high impedance and the secondary current is therefore very low. Voltage transformers produce manageable voltages and very low currents which enable the system voltages to be accurately measured. Voltage transformers do not carry fault current and therefore do not have the same problems as current transformers.


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