Open-close current transformer, everyone is familiar with it. Their main function is to convert high values to low values. Suitable for measuring instruments and relays. Generally, the secondary rated current is 5A. So why should the current transformer be grounded? =
The secondary windings of current transformers and voltage transformers should be grounded during operation to prevent the high voltage and low voltage from being connected through the transformer after the insulation of the transformer is damaged, causing damage to the instrument and the operator. The secondary grounding of the transformer not only does not affect the normal operation of the equipment, but also ensures the safety of personnel and equipment.
In order to ensure safety, it is necessary to stop the grounding of the secondary side of the current transformer to maintain the secondary side of the current transformer from high voltage hazards and ensure the safety of people and equipment.
(2) What is the function of the current transformer?
During the production process, the operating status of each equipment in the system is monitored to ensure the safe operation of the power system. The current transformer usually converts the large current of the primary circuit into a small secondary current proportional to it, and finally outputs the small secondary current to the secondary instrument, relay maintenance, and automatic installation and application. Therefore, the current transformer is the AC current source of the electrical control, conditioning, measurement and maintenance components, and it is also the contact point of the secondary circuit and the primary circuit.
(3) Why should the current transformer be grounded?
One is to ensure safety, one is equipment safety, and the other is personal safety. There are scattered capacitances between the primary winding and the secondary winding of the current transformer, and between the secondary winding and the ground. The local voltage of this scattered capacitance causes the secondary winding to produce 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 current transformer must be grounded, and the secondary circuit only needs one grounding point, not multiple grounding points.
(4) Why can’t the secondary side of the current transformer be opened?
As the secondary circuit of the current transformer is disconnected, the secondary current disappears and the demagnetization effect disappears, resulting in a high magnetic density of the iron core. Since the number of turns of the secondary winding is much greater than the number of turns of the primary winding, once the secondary side is open, there will be a good high voltage, sometimes as high as thousands of volts, so not only the secondary side is endangered Equipment, but also endangering personal safety.