Grounding and Bonding in Gas-Insulated Switchgear

Ensuring Safe and Reliable Power Distribution

 


Image for illustration purposes.

Gas-Insulated Switchgear (GIS) is a type of electrical equipment used in high-voltage power distribution systems. It uses a dielectric gas, typically sulfur hexafluoride (SF6), to isolate various switchgear components in grounded metal enclosures. This design provides excellent electrical insulation and arc extinguishing properties, making GIS suitable for use in confined indoor spaces where high voltages must be carried.

The working principle of GIS is based on the insulation of electrical equipment with a dielectric gas. SF6 has several advantages over other types of insulating materials, including excellent thermal and dielectric properties. By using a combination of vacuum and gas, GIS isolates live parts, making the switchgear very compact and efficient, while also offering excellent reliability and low maintenance requirements.

However, GIS requires proper grounding and bonding to ensure safe and reliable power distribution. Grounding and bonding are critical to prevent electrical shock and ensure the safe operation of the switchgear. The IEEE Standard 80/1976 provides guidelines for the design of grounding systems for GIS.

A well-designed grounding system for GIS should consider the characteristics of the combined grid-rod system, sizing of conductors and joints, and methods for calculating ground resistance. The system should also take into account the properties of concrete-encased electrodes and the use of bentonite.

In addition, the GIS enclosure should be designed to withstand fault conditions, and the potentials of the enclosure during fault conditions should be carefully considered. The use of GIS in substations requires a thorough understanding of the fundamental aspects of grounding design, including the differences between conventional and gas-insulated equipment installations.

Source: Electrical Engineering Portal