Measurement current transformer (or current transformer measurement winding. In the normal operating current range, to measure, metering and other devices to provide information on the current of the grid.
Protection current transformer (or current transformer protection winding. In the grid fault state, to the relay protection and other devices to provide grid fault current information.
Second, according to the insulation medium
Dry current transformer: by the ordinary insulating material through the paint impregnation treatment as insulation.
Cast current transformer: epoxy resin or other resin mixed material cast molded current transformer.
Oil-immersed current transformer: insulating paper and insulating oil as insulation, generally outdoor type. At present, our country in various voltage levels are commonly used.
Gas-insulated current transformer: the main insulation consists of gas.
Three, according to the principle of current conversion
Electromagnetic current transformer: according to the principle of electromagnetic induction to realize the current transformer.
Optoelectronic current transformer: through the photoelectric conversion principle to realize the current transformer, is still under development.
Four, according to the installation method
Through current transformer: used to pass through the screen or wall current transformer.
Pillar current transformer: installed in the plane or pillar, and do a primary circuit conductor pillar with the current transformer.
Sleeve type current transformer: there is no primary conductor and primary insulation, directly set in the insulated sleeve of a current transformer.
Bus type current transformer: there is no primary conductor but have a primary insulation, directly set on the busbar to use a current transformer.
1, three-phase completely star-shaped wiring can accurately reflect the real current in each of the three phases. This method is used in high-current grounding system to protect the line of three-phase short circuit, two-phase short circuit and single-phase grounding short circuit.
2, two-phase two-relay incomplete star wiring can accurately reflect the true current of the two phases. This method is used in 6 ~ 10kV neutral point is not grounded in the small current grounding system to protect the line of three-phase short circuit and two-phase short circuit.
3, two-phase differential connection reflects the two-phase differential current. The wiring is used in 6~10kV neutral point not grounded small current grounding system, the protection line of the three-phase short circuit, two-phase short circuit, small-capacity motor protection, small-capacity transformer protection.
4, single-phase wiring in the three-phase current balance, single-phase current can be used to reflect the three-phase current value, mainly used for measuring circuit.
5, two-phase three-relay completely star wiring, the current flowing into the third relay is Ij = Iu + Iw = - Iv. This wiring is used in high-current grounding system, the protection of three-phase and two-phase short-circuit circuit line.