How to install and regulate current transformers

1. The metal frame on which the current transformer is installed (such as the busbar frame in the distribution cabinet) must be solid, and the exposed metal part of the transformer shell must be reliably grounded.

2. Wire correctly according to the diagram in the instruction manual. The numerical markings on both ends of the wire should be clear, and the marking range should meet the requirements of the rules.
3. The same group of current transformers should be installed in the same direction to ensure that the positive direction of the primary and secondary circuit currents of the current transformer group is the same, and the nameplate should be as easy to observe as possible.

4. Open circuit is not allowed on the secondary side of the current transformer. When only one secondary loop is used for the secondary round transformer, the other secondary loop should be short-circuited reliably.

5. The secondary circuit conductor or cable should use copper wire. The cross-section of the current transformer line wire should not be less than 2.5mm2, and the voltage transformer loop wire cross-section should not be less than 1.5mm2.

6. The first row at the outlet of the current transformer should select a dedicated current terminal. The secondary winding not used by the current transformer should be short-circuited and grounded on the wiring board.

7. The secondary circuit conductors in the disc and cabinet should not have joints, and there should be no joints in the middle of control cables or conductors. If a joint is necessary, a stronger terminal should be used for the transition connection.
8. The polarity of the current transformer cannot be reversed, and the phase difference and phase difference should meet the requirements of the design and regulations. For the transformer wiring of differential protection, the current phasor diagram of both arms must be measured before putting it into operation to check the correctness of the wiring.

9. The secondary circuit wires should be arranged neatly and beautifully. The connecting screws between the wires and the electrical components and terminal blocks should not be loose. The distance between the wires and the clamping points should comply with the requirements of this rule.

10. The insulation of the secondary circuit to the ground should be good, and the voltage circuit and the current circuit should not be mixed.

11. The current and voltage circuits should be grounded at the secondary side outlet of the transformer. (Note: The secondary side of the low-voltage current transformer cannot be grounded. Since the insulation levels of the wires, energy meters and transformers used in the low-voltage metering device are the same, the maximum voltage they can withstand is basically the same; when other secondary windings are grounded, the entire device The insulation level of the primary circuit is reduced, which can easily damage the insulation weakness of the energy meter or transformer (such as induced lightning strikes). In order to reduce the damage caused by lightning strikes, it is best not to ground the secondary side.)

12. The current transformer should be installed in the complete distribution cabinet. This kind of current transformer is not installed on the body. Finally, check whether the installation wiring is correct.