How to install a zero-sequence current transformer?

1. Select the installation location
Installation location: The zero-sequence current transformer is usually installed at the neutral point of the power system to detect the zero-sequence current in the power system.
High-voltage system: When the cable is connected to the transformer at the lower port of the high-voltage switch of the high-voltage outlet cabinet, the cable must pass through the zero-sequence transformer for all three phases, and the zero-sequence transformer is secondary connected to the microcomputer or relay of the high-voltage outlet cabinet for protection.
Low-voltage system: The zero-sequence transformer can also be worn on the zero row of the low-voltage side of the transformer, and then protected by a current relay.
2. Installation of integral transformer
Installation before laying the cable: The integral zero-sequence current transformer should be installed before laying the cable, and the cable should pass through the transformer during installation.
3. Installation of open-type transformer
Remove the connecting piece: Remove the connecting pressing piece of the transformer "K1" and "K2" (there is no such requirement for circular transformers).
Loosen the bolts: Loosen and remove the two hexagon socket bolts on the top of the transformer (the circular transformer is to loosen and remove the fastening screws on both sides), and the transformer is divided into two parts.
Put on the cable: Put the transformer on the cable, wipe the contact surface clean, apply a thin layer of anti-rust oil, align the two parts of the transformer, and then screw on the hexagon socket bolts (fastening screws on both sides). The two parts of the transformer should be aligned to avoid affecting the performance.
Restore the connecting piece: Fix the connecting piece on "K1" and "K2" (there is no such requirement for the circular transformer).
Install a non-magnetic bracket: If the transformer with an inner hole >120mm is installed horizontally, please add a non-magnetic bracket.
4. Grounding wire processing
Grounding wire position: According to the position of the cable grounding point, correctly handle the grounding wire. When the cable grounding point is led out below the transformer, the grounding wire should be directly grounded; when the grounding point is led out above the transformer, the grounding wire should pass through the transformer for grounding.
Grounding wire requirements: The grounding wire must be made of copper stranded wire or tinned copper braided wire. The cross-section of the grounding wire should not be less than 25mm². The grounding end must be welded with a terminal. The relative position of the grounding wire and the zero-sequence current transformer must be properly handled. The grounding wire must be installed on the grounding copper busbar.
Installation precautions
Inner diameter selection: Ensure that the inner diameter of the selected zero-sequence current transformer is larger than the outer diameter of the cable terminal head.
Construction specifications: Try not to dismantle the zero-sequence current transformer during construction. If it must be dismantled, it must be restored to its original state after the work is completed.
Grounding wire processing: The grounding wire must be connected to the dedicated grounding copper busbar in the switch cabinet. The grounding wire must be made of copper stranded wire or tinned copper braided wire. The cross-section of the grounding wire must meet the requirements of the regulations.
Magnetic circuit closure: The magnetic circuit should be closed after the external zero-sequence CT is installed, and the zero-sequence CT primary joint screws should be tightened.
Firm installation: The zero-sequence current transformer should be installed on the bottom plate of the switch cabinet and fixed with a reliable bracket.