There are several wiring methods for current transformers:

One phase wiring: The current passing through the current coil reflects the corresponding phase current of the primary circuit, usually used in three-phase circuits with load balance, such as low-voltage power lines, for measuring current, electrical energy, or connecting load protection devices.

Two phase V-shaped connection: also known as two phase incomplete star connection, in relay protection devices, it is called two phase two relay connection and is widely used for measuring three-phase current, electrical energy, and for overcurrent relay protection. The current on the common line of the two V-shaped connections reflects the phase current of the phase that is not connected to the current transformer.

Two phase current difference wiring: In relay protection devices, this wiring is also known as two phase one relay wiring, suitable for overcurrent relay protection in three-phase three-wire circuits with ungrounded neutral points. The current value on the common line on the secondary side of the current transformer in this wiring method is three times the root of the phase current.

Three phase star connection: In this connection method, the three current coils exactly reflect the current of each phase. Widely used in i-phase four wire systems with generally unbalanced loads, as well as in three-phase three wire systems with potentially unbalanced loads, for three-phase current and energy measurement and overcurrent relay protection.

Three phase angular wiring: This wiring method is used to cooperate with three current relays to protect various short circuit faults.

Zero sequence current transformer wiring: suitable for zero sequence grounding protection. When the neutral point of the three-phase current transformer is grounded, the three-phase zero sequence current transformer wiring can be used.