Views:71 Author:Site Editor Publish Time: 2019-08-06 Origin:Site
Earthing refers to the neutral point of power system and electrical devices, the exposed conductive part of electrical equipment and the device's external conductive part connected to the earth through conductors. It is realized by connecting metal wires with earthing devices. Among them, protection earthing, working earthing, lightning earthing, shielding earthing, static electricity protection ground and so on are commonly used.
The safe earthing of the chassis is to form a good conductive connection between the metal parts (cabinet shell, operating table shell, etc.) which are not normally charged in the system and the ground in order to protect the equipment and personal safety. The reason is that the power supply of the grounding system is strong power supply (380, 220 or 110V). Usually the case is not charged. When faults occur (such as mainframe power failure or other faults) resulting in short circuit between the power supply wire and the conductive metal parts such as the shell, these metal parts or the shell will form charged bodies. There will be a high potential difference between the charged body and the ground without good earthing. If people touch these charged bodies accidentally, they will create danger through personal formation pathways. Therefore, a good connection must be made between the metal housing and the ground. In addition, the protection earthing can also prevent the accumulation of static electricity.
Working earthing is designed to make the system and the instruments connected with it reliable and ensure the accuracy of measurement and control. It is divided into machine logic earthing, signal circuit earthing, shielding earthing, and intrinsically safe earthing in petrochemical and other explosion-proof systems.
Lightning protection earthing is a earth system to prevent damage caused by lightning attack (direct strike, induction or line introduction). There are often signal (weak current) lightning protection ground and power (strong electricity) lightning protection ground. The reason for this distinction is not only that the earthing resistance is different, but also that in engineering practice, the signal earthing protection is often attached to the signal independently, and the power supply lightning protection is constructed separately.
As a part of lightning protection measures, lightning earthing is used to introduce lightning current into the earth.The lightning protection of buildings and electrical equipment mainly uses lightning arresters (including lightning rods, lightning belts, lightning arresters and lightning eliminating devices, etc.) to connect one end with the protected equipment and the other end with ground devices. When a direct lightning strike occurs, the lightning arrester directs the lightning to itself, and the lightning current enters the earth through its lighting conductor and grounding device.
This is an effective measure to eliminate the harm of electromagnetic field to human body. It is also an effective measure to prevent electromagnetic interference. High frequency technology has been widely used in electric heating, medical treatment, radio broadcasting, communication, television and navigation, radar, etc. The radiation energy absorbed by human body under the action of electromagnetic field will have biological effects. This can cause harm to the human body, such as a slight tremor of fingers, skin scratches, visual impairment, etc. A shielding device is installed on the outer shell of the equipment which generates magnetic field, and the shielding body is grounded. This can reduce the intensity of electromagnetic field outside the shield and achieve the purpose of reducing or eliminating the harm of electromagnetic field to human body. It can also protect the equipment in the shielded earthing body from the interference of external electromagnetic field.
In order to prevent the harm of static electricity, the most important part of static electricity protection is to release it.
Earthing is an electrical safety measure to ensure the personal safety and normal operation of electrical equipment. Earthing devices introduce leakage current, static charge and lightning current which may be generated on electrical equipment and other production equipment into the underground. This avoids personal electric shock and possible accidents such as fire and explosion.