Reasons for Grounding of The Secondary Side of Current Transformers

The reason for grounding the secondary side of current transformers is mainly based on safety considerations, which can be divided into the following points:

Protection of personal safety: There is distributed capacitance between the primary and secondary windings of the current transformer, as well as between the secondary winding and the ground. The voltage distribution of this distributed capacitor may generate a higher voltage on the secondary winding, posing a threat to personal safety. Therefore, by grounding, this part of the voltage can be introduced to the ground, reducing the potential harm to human health.

Prevent insulation damage: When the insulation between the primary and secondary windings is damaged due to certain reasons, the high voltage of the primary circuit may be directly added to the secondary circuit. In this case, secondary grounding can ensure that high voltage is introduced to the ground, preventing harm to secondary equipment and personal safety.

Prevent high voltage series connection: The grounding of the secondary side of a current transformer is actually to prevent the high voltage on the primary side inside the transformer from being connected to the secondary low voltage due to other reasons (such as insulation breakdown). This high voltage series connection may form a circuit for the silicon steel sheet (iron core) or secondary side coils, posing a threat to human safety.

Ensure equipment safety: Grounding can ensure that in the event of insulation damage, when a high voltage is connected to the secondary circuit, the current passing through the ground can clamp the secondary voltage of the transformer to the ground voltage, thereby protecting the safety of secondary instruments and other equipment.

In summary, the grounding of the secondary side of current transformers is to protect personal and equipment safety, and to prevent high voltage cascading caused by insulation damage or other reasons from causing harm to personnel and equipment. Meanwhile, grounding can also ensure that in the event of insulation damage, the current passing through the ground can clamp the secondary voltage of the transformer to the ground voltage, protecting the safety of secondary instruments and other equipment.