The basic components of a transformer are the windings, the core, the insulation and the outer casing. In the same circuit, to meet the requirements of measurement and relay protection, a circuit often needs a lot of current transformers. In order to save materials and reduce investment, a high-voltage current transformer is often equipped with independent irons that are not magnetically connected to each other. The core ring and the secondary winding share a primary winding. In this way, a plurality of current transformers having the same ratio and different levels of accuracy can be formed. The electrical measurement requires high accuracy of the current transformer, and the impact of the instrument is small when the short circuit is short. Therefore, the core of the current transformer for measurement is easily saturated in the short circuit of the primary circuit to limit the increase of the secondary current. The core of the current transformer for relay protection should not be saturated in the event of a primary current short circuit, so that the secondary current can be increased in proportion to the primary short-circuit current to meet the requirements of protection sensitivity. In order to adapt to the change of primary current and reduce the product specifications, the primary windings are often divided into several groups. By switching the wiring to change the series and parallel connection of the primary windings, various current ratios can be obtained.
The single-turn type through-type transformer itself is equipped with a single copper tube or a copper rod as a primary winding; the bus-type transformer does not have a primary winding itself, but a gap that passes through the primary winding in the iron core, and a busbar during construction. Pass through the gap as a primary winding.
2. Structure type of current transformer
(1) Sleeve type current transformer (2) Oil-filled current transformer
(3) Capacitive current transformer (4) SF6 gas insulated inverted current transformer
(5) Through-wall epoxy current transformer