1) The wiring of current transformers should adhere to the series connection principle: that is, the primary winding should be connected in series with the circuit being measured, while the secondary winding should be connected in series with all instrument loads

2) Choose appropriate variations according to the magnitude of the current being measured, otherwise the error will increase. At the same time, one end of the secondary side must be grounded to prevent high voltage from the primary side from entering the low voltage secondary side in case of insulation damage, causing personal and equipment accidents

3) The secondary side must not be allowed to be open-circuited. Once open-circuited, the primary side current I1 will all become magnetizing current, causing a sudden increase in φm and E2, resulting in excessive saturation magnetization of the iron core, severe heating, and even coil burnout; at the same time, after the magnetic circuit is excessively saturated and magnetized, the error will increase. When the current transformer is working normally, the secondary side is approximately short-circuited. If it is suddenly open-circuited, the excitation electromotive force will suddenly change from a very small value to a very large value, and the magnetic flux in the iron core will exhibit a severely saturated flat-topped waveform. Therefore, the secondary side winding will induce a very high spike waveform when the magnetic flux passes through zero, with values reaching thousands or even tens of thousands of volts, endangering the safety of personnel and the insulation performance of the instrument.

In addition, an open circuit on the primary side can cause the secondary side voltage to reach several hundred volts, which can result in electric shock accidents if touched. Therefore, the secondary side of the current transformer is equipped with a short-circuit switch to prevent an open circuit on the primary side. During use, if the secondary side is open, the circuit load should be immediately removed, and then the equipment should be shut down for handling. It can only be used again after everything is properly handled.

4) To meet the needs of devices such as measuring instruments, relay protection, circuit breaker failure judgment, and fault filtering, 2 to 8 current transformers with secondary windings are installed in circuits including generators, transformers, outgoing lines, bus sectionalizers, busbar circuit breakers, and bypass circuit breakers. For high-current grounding systems, they are generally configured in three phases; for low-current grounding systems, they are configured in two or three phases according to specific requirements

5) The installation location of protective current transformers should be set to minimize the non-protected area of the main protection device. For example, if there are two sets of current transformers and the location allows, they should be installed on both sides of the circuit breaker, so that the circuit breaker is within the cross-protection range

6) To prevent busbar faults caused by flashover of the bushing of pillar-type current transformers, the current transformers are usually arranged on the outgoing line side of the circuit breaker or on the transformer side

7) To mitigate damage during internal faults in the generator, the current transformer used for automatically adjusting the excitation device should be arranged on the outgoing line side of the generator stator winding. To facilitate analysis and detect internal faults before the generator is connected to the system, the current transformer used for measuring instruments should be installed on the neutral point side of the generator.