Operation Considerations and Installation Methods of Split-core Zero-sequence Current Transformers

What issues should be noted during the operation of the switch-type zero-sequence current transformers?

The switch-type zero-sequence CT current transformer is mainly used in the transformation projects of industrial and agricultural networks. The equipment is easy to install and can be powered on without dismantling the busbar. It will not affect the normal power consumption of customers, and it can save manpower, materials, and financial resources for customers' transformation projects, improving efficiency.

The current transformers should not open the secondary side during operation. Once the secondary side is open, the insulation will break down due to iron loss and high temperature, or the secondary winding voltage will rise, which will lead to the risk of high-voltage electric shock. Therefore, when replacing electric meters such as ammeters, active meters, and reactive meters, the current circuit should be short-circuited before replacing the electric meters. After adjusting the instrument, the instrument should first be connected to the secondary circuit, and then unplug the short-circuit wire to check if the instrument can operate normally.
When the insulation resistance of the secondary coil of the switch-type zero-sequence current transformers is lower than 10-20 megaohms, it should be dried and insulated before use.
If the CT current transformer makes a buzzing sound, check whether the internal iron core is loose and tighten the iron core bolts. One end of the secondary side of the switch-type zero-sequence CT current transformer and the outer casing should be grounded.
If sparks are found when removing the short circuit, it means that the high-voltage voltage transformer has been opened. Therefore, the short circuit should be shortened immediately to find that there is no open circuit in the instrument circuit before removing the short circuit again. In addition, maintenance and installation of the CT circuit should be considered to be suspended. Only after the work is completed, can the maintenance and installation be put into use.

It is reminded here that in order to ensure safety, the secondary circuit of the switch-type zero-sequence current transformers must be grounded. Otherwise, when the insulation between the primary and secondary of the current transformers is damaged, the high voltage of the primary circuit will be directly added to the secondary circuit, which will damage the secondary equipment and endanger personal safety.

Installation method of split-core zero-sequence current transformers

The installation method of the split-core current transformers is not restricted by the cable laying. The installation method is as follows:

Remove the connecting pressure pieces of "K1" and "K2" of the transformer.
Note: This item does not apply to circular transformers.
Loosen the two internal hexagonal bolts at the top of the current transformers, dismantle the transformer into two parts.
Note: For circular transformers, loosen the screws on both sides and remove them.
Install the current transformers on the cable, wipe the contact surface clean, thinly coat it with rust-proof oil, align the two parts of the current transformers and tighten the internal hexagon socket bolts (screws on both sides), the two parts must be aligned to avoid affecting performance.
Fix the connection pieces on "K1" and "K2" (no such requirement for circular transformers).
If the inner hole of the current transformers is greater than 120mm, please add a non-magnetic support when installing horizontally.

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