Why should one end of the CT be grounded?

The secondary winding of current transformer and voltage transformer should be grounded during operation, so as to prevent the high voltage from entering the low voltage through the transformer in series after the insulation of the transformer is broken down, injuring the instrument and operation personnel. The secondary point grounding of the transformer will not affect the normal operation of the equipment, but also ensure the safety of personnel and equipment.
To ensure safety, the secondary side of the CURRENT transformer must be grounded to protect the human body and equipment when the secondary side of the current transformer is in high voltage danger.

Current transformer action

In the process of production, we monitor the running status of each equipment in the system to ensure the safe operation of the power system.
The current transformer usually transforms the large current of the primary circuit into the secondary small current which is directly proportional to it, and finally outputs the secondary small current to the secondary instrument, relay protection and automatic device for use.
Therefore, current transformer is the ac current source of electrical control, regulation, measurement and protection components, and also the hub of the connection between the secondary circuit and the primary circuit.

Why cannot the secondary side of the CT be open?
Because the secondary circuit of the CT is open, the secondary current will disappear, and the demagnetization will also disappear, resulting in high magnetic density in the core.
And because the number of winding turns on the secondary side is much larger than the number of winding turns on the primary side, so once the secondary side is open, there will be a good high voltage, sometimes up to thousands of volts, so it not only endangers the secondary side equipment, but also endangers personal safety.

Why should current transformers be grounded?

It is to ensure safety, one is equipment safety, two is personal safety.
There are distributed capacitors between primary winding and secondary winding of ct and between secondary winding and ground.
The voltage divider of this distributed capacitance causes the secondary winding to generate a higher voltage to the ground.
In addition, the insulation between the primary winding and the secondary winding is damaged due to some reasons, so the high voltage of the primary circuit will be directly added to the secondary circuit, which is very harmful to the secondary equipment and personal safety.

Therefore, the secondary side of the CT must be grounded, and the secondary loop has only one ground point. Multiple ground points are not allowed.