Why should one end of the current transformer be grounded?

why should one end of the current transformer be grounded? It is difficult to explain it in a short time, so let's give you some popular science!

(1) Secondary windings of current transformers and voltage transformers

The secondary windings of current transformers and voltage transformers must be grounded during operation to prevent high voltage from entering low voltage through the transformer after the transformer insulation is broken down, thereby injuring instruments and operators. Grounding the secondary point of the transformer will not affect the normal operation of the equipment and will also ensure the safety of personnel and equipment.

To ensure safety, the secondary side of the current transformer must be grounded to protect people and equipment when there is a high voltage danger on the secondary side of the current transformer.

(2) What is the function of a current transformer?

During the production process, the operating conditions of each primary device in the system are monitored to ensure the safe operation of the power system. Current transformers usually convert the large current of the primary circuit into a proportional secondary current, and finally output the secondary side small current to the secondary instrument, relay protection, and automatic device for use. Therefore, the current transformer is the AC current source of electrical control, regulation, measurement and protection components, and is also the hub for the connection between the electrical secondary circuit and the primary circuit.

(3) Why does the current transformer need to be grounded?

It is to ensure safety, firstly, equipment safety and secondly, personal safety. Because there is distributed capacitance between the primary winding and the secondary winding of the current transformer and between the secondary winding and the ground. Then the voltage division of this distributed capacitance causes the secondary winding to generate a higher voltage to the ground. In addition, if the insulation between the primary winding and the secondary winding is damaged for some reason, 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 current transformer must be grounded, and the secondary circuit has one and only one grounding point. Multiple grounding points are not allowed.

(4) Why can’t the secondary side of the current transformer be open-circuited?

Because the secondary circuit of the current transformer is open, the secondary current disappears, and the demagnetization effect also disappears, which will cause the magnetic density in the iron core to be very high. Because the number of turns of the secondary winding is much larger than that of the primary winding, once the secondary circuit is open, a very high voltage will appear, sometimes up to thousands of volts, which not only endangers the secondary equipment, but also endangers personal safety.