Composition and function of the medium voltage earthing switch
What is an earthing switch?
The earthing switch is a mechanical earthing device to release the static electricity of the equipment and circuit to be repaired and to ensure the personal safety of the maintenance personnel in the case of power failure. It can withstand a current for a certain period of time under abnormal conditions (such as short circuit) but does not pass through load current under normal conditions. It is usually part of the disconnecting switch.
An earthing switch is a mechanical switching device used to intentionally earthing a loop.
Earthing switch in abnormal conditions (such as short circuit), can bear the specified rated short circuit current and the corresponding peak current in the specified time; however, under normal working conditions, it is not required to carry rated current.
Composition of the earthing switch
Earthing switches and disconnecting switches are often used in combination with one device. At this point, in addition to the main contact, the disconnecting switch also has an earthing switch for earthing one end of the disconnecting switch after the disconnecting. The main contact and the earthing switch are usually mechanically interlocked in such a way that the earthing switch cannot be closed when the disconnecting switch is closed and the main contact cannot be closed when the earthing switch is closed.
The earthing switch can be divided into two types: open type and closed type. The conductive system of the former is exposed to an earthing switch similar to an isolation switch in the atmosphere, while the conductive system of the latter is enclosed in a charge of SF. Or oil, etc.
The earthing switch needs to switch on and off the short-circuit current and must have a certain short-circuit switching ability and dynamic and thermal stability. But it does not need to break the load current and short circuit current, so there is no arc extinguishing device. The lower end of the knife is usually connected to the earthing point by a current transformer. The current transformer can give signals for relay protection.
All kinds of earthing switches have unipolar, bipolar and tripolar points. Unipole is used in neutral earthed systems only, bipolar and tripole are used in neutral unearthinged systems and share a single operating mechanism for operation.
The function of the earthing switch
(1) Normal working earthing during line maintenance. When the circuit breaker needs to be repaired, the circuit breaker is in the opening position, and the disconnecting switches on both sides are open and in the opening state. The earthing switch is closed for normal working earthing. To ensure the safety of equipment and maintenance personnel.
(2) Applicable to electrostatic and electromagnetic induction current. In two or more common towers or adjacent parallel arrangement of overhead transmission lines, when a line or several times of power failure, due to the electromagnetic induction and electrostatic induction between it and adjacent live lines, in the circuit of power failure will produce induced voltage and induced current. An earthing switch for such a line.
(3) Turn off the short circuit current. For earthing switches having rated short-circuit switching current, they shall be able to switch on and off at any applied voltage including their rated voltage and at any current including their rated short-circuit switching current. The rated short-circuit closing current of the earthing switch is equal to the rated peak tolerance current.
Professional MV earthing switch supplier and manufacturer
Zhejiang JGGY Electrical Co.,Ltd (jggyelectrical.com), JGGY Electrical was established in 2007, specializing in the manufacture, sales and service of mv earthing switch and other medium voltage electrical products. JGGY Electrical mainly specializes for 6~42kV medium voltage electric (outdoor and indoor): load break switch, disconnector, cutout fuse, surge arrester, vacuum circuit breaker.
Our technical expertise, comprehensive product portfolio and long-term rich experience are helping many customers in need to solve their power problems. We're happy to help at any time. Whether you need application product advice or technical assistance, our global service team is committed to providing you with the right support. For more technical information about medium voltage earthing switch, feel free to contact us, send an email to sales@jggyelectrical.com.
