At 6-10 kV to produce supporting anadromous and one-and two secondary windings of accuracy classes 0.2, 0.5, 1 and 3. Accuracy class specifies maximum error introduced by CT in the measurement results. Transformers accuracy class 0.2, with minimum error, is used for laboratory measurements, 0.5 – for food counters, and a 3 – to power the relay coils and current technical instruments of measurement. For safe operation of the secondary winding must be grounded and should not be opened. When installing the switchgear 6-10 kV current transformers used with cast and porcelain insulation, and at a voltage of up to 1000 – with a cast, cotton and porcelain.

The operating principle of the device and the transformer action of transformer based on the phenomenon of mutual induction. If the primary winding transformer included in the network AC source, then it will take place alternating current, which will create the core of the transformer AC flux. This magnetic flux penetrating the secondary windings winding will induce an electromotive force in it (EMF). If the secondary winding shorted to a receiver of energy, under the influence of EMF on induktiruemoy this winding and a receiver of energy starts to flow current. At the same time in the primary will also load current. Thus, electrical energy, being transformed, transferred from the primary to the secondary network with a voltage, which is calculated on the receiver power incorporated into the secondary network. In order to improve magnetic coupling between primary and secondary windings are placed on their steel magnetic circuit.