Substation main equipments

Gas Insulated Swichgear ( GIS) - GENERAL EARTHING INFORMATION

Earthing and return current conductors

Earthing conductors

Earthing conductors interconnect the GIS enclosure at numerous points with the earthing net (multipoint earthing). Being a component of the earthing system they effectively help to avoid dangerous touch voltages during a short circuit, and to keep HF transient overvoltages on a sufficiently low level during normal service. To meet these requirements they shall have low impedances at 50/60 Hz as well as in the HF range.

SF6 gas (Part 1)

• Since 1960, SF6 has been used as arc quenching and insulating medium for high and medium voltage switchgear systems. The favourable electrotechnical, chemical and physical characteristics of the gas have considerably influenced the development of the switchgear technology. SF6 is an alternative to other conventional insulating and quenching media such as e.g. oil, and air. The use of SF6 gas considerably increases, in some applications, the efficient utilisation of resources in energy transmission and distribution with respect to technology, finances and personnel [1]. At the same time SF6 in comparison to oil reduces the risk of hazard (e.g. fire, explosion) to personnel and environment. An overall evaluation considering all ecological, economic, safety and technological aspects has proven that SF6 is still an excellent choice as insulating medium [2]. The existing SF6 technology in the field of energy transmission and