Under what circumstances are insulators required for the fixed installation of grounding bars?
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In distribution rooms, cabinet areas, and the field, many grounding bars are typically installed; some of these grounding bars are fixed directly to the steel profiles, while others are fixed to those profiles after being equipped with insulators. I noticed that the grounding bars inside some distribution cabinets and enclosures are equipped with insulators; this is likely done to meet the requirements of the working ground, in order to prevent the enclosure from becoming accidentally charged and causing current to flow into the components being used (thus providing isolation from the protective ground). Is the same principle applied to the grounding bars installed in the distribution room, cabinet rooms, and on-site as well? Is the protective ground directly fixed to the steel profiles, while the working ground is fixed to the steel profiles after being fitted with insulators? Could you experts please advise me if this understanding is correct? Thank you!
In electrical and electronic systems, a grounding bar (also known as a ground strip or ground bus) is a metal bar used to collectively connect various grounding wires. Whether insulators are required for the fixed installation of grounding bars usually depends on the type of grounding system and the design requirements. 1. Protective grounding (PE): The purpose of protective grounding is to ensure that the equipment’s enclosure and other parts that can be touched by operators do not become electrically charged accidentally, thereby preventing electric shock. In this case, the grounding bar is usually fixed directly to the metal steel sections, ensuring a good electrical connection between the grounding system and the metal structure of the equipment, thereby safeguarding personal safety. 2. Functional grounding (FG) or operational grounding: Used to ensure the proper operation of electrical equipment, such as as a reference point for signal transmission or for noise suppression in electronic devices. In such cases, insulators may be required to separate the grounding bar from other metal structures, in order to prevent the grounding system from introducing interference or affecting the operating potential. 3. Mixed grounding system: Sometimes, a grounding bar may be used simultaneously for protective grounding and functional grounding. Under such circumstances, the design must be carefully planned to ensure that all relevant safety specifications are met. If the specifications require it, insulators may be needed to avoid interference or hazards caused by potential voltage differences between the working area and the protected area. Therefore, your understanding is generally correct. When designing, it is necessary to consider whether the purpose of grounding is protective grounding or functional grounding, or a combination of both. Protective covers can usually be fixed directly to metal profiles to ensure a good electrical connection ； The working area may need to be secured with insulators in order to maintain its relative independence and reduce interference. However, the specific details still need to be determined and designed in accordance with local electrical safety standards and regulations. .
The conventional protective enclosure is directly connected to the box housing; therefore, insulating the protective enclosure from the housing goes against the purpose of providing protection. For signal grounding, it is separated from the protective ground inside the cabinet; there is a separate grounding wire that connects to the grounding busbar. Therefore, it should be insulated from the enclosure, meaning it is separated from the protective ground within the cabinet, but in reality, it is still connected to the busbar.
This post was last edited by canghai5 on 2023-11-12 07:06. Thank you for your participation. I have seen cases where the protective ground connected to the enclosure of the distribution cabinet or instrument cabinet is separated from the working ground (or signal ground) inside the cabinet. What I want to understand is how to determine, in substations, cabinet rooms, and locations where installations are carried out, which type of grounding bar – one with insulators or one without them – should be used; that is, under what conditions should grounding bars with insulators be installed and under what conditions those without insulators?