This article explains in detail what a gas insulated switchgear is, how it works, and what voltage types are available in industries. First of all what is GIS? The answer that electricians can widely say is that the switchgear that are filled with SF6 gas is called GIS. But is that the definition?
What is Gas insulated switchgear?
Gas insulated switchgear is a metal closed type switchgear that acts as an insulator between live parts and soil metal casing with sulfur hexafluoride (SF6) gas. High voltage equipment is housed in a gas tight container filled with a degassing gas called SF6.
What are GIS systems are available?
These GIS switchgear are available in voltage ranges from 12 kV to 800 kV.
Medium voltage GIS are available up to 52 kV. Its pressure of SF6 gas must below 2.5 bar. Medium voltage GIS system has vacuum circuit breaker as the interrupting medium and SF6 gas as the main insulation. The substation using the SF6 gas for both insulation and interruption are also available in medium voltage. One is designed to act as an insulator and the other as an interrupter to equipment.
This Medium voltage system is covered in standard IEC 62271-107. Standard of High voltage GIS for class above 52 kV are covered in IEC 62271-108. Click here to know IEC 62271-100: 2017 Standard of High-voltage switchgear and control-gear.
What are components of gas insulated substation?
The principal gas insulated components for a sub-station are bus-bar, disconnector or isolator, circuit breaker, current transformer, and earth switch. Gas insulated switchgear is a major component in a substation. The supplementary of gas insulated components required for a sub-station are terminations, voltage transformer, and surge and lighting arrester.
Gas Insulated Switchgear
The assembly of such system at a substation is defined as a GIMES by the IEC. This Gas Insulated Metal Enclosed Substation technology has now been well established for almost thirty years.
HV GIS for 725 kV and 800kV voltages are basically two pressure systems where vacuum interference is not available in this high voltage range. Modular components are assembled with each other to form the desired arrangement for a section or a bay in Gas Insulated Substations.
Gas Insulated Metal Enclosed Switchgear(GIMES) Constructional Arrangements
Gas insulated switchgear are well designed in various constructional arrangements, you can read read it below:
Electrical circuit elements like a single pole circuit breaker, a disconnector, a current transformer are assembled in is a Isolated single phase gas insulated module. Once this module of three circuits connected, one by one is a form of three phase bay or section. To configure this method need more section width than others.
This configuration is designed to reduce bay width, it is a new module features with connected three phase elements in individual enclosure. Three poles circuit breaker, three pole isolator, three phase current transformer are forming a three phase module for the element.
The hybrid system is developed to achieve an optimal techno commercial solution. The configuration is an appropriate combination of isolated single phase and three phase elements module. Unlike the other configurations, this hybrid system is intended to saving space of bay with its commercial. The Hybrid GIS module is a popular and commercial one which is designed to shrink substation size.
Three phase module systems are basically Compact GIS systems. But, it has more functional element in single enclosure. Single enclosure assembled with three pole circuit breaker, three phase current transformer and other circuit elements. This configuration helps to reduce the depth of the bay.
The Highly Integrated Systems (HIS) is a configuration that invented in 21st century. It is a design that single unit metal connected with GIS. HIS system provides a complete solution for outdoor substation, and the system got high rate on it. There will be no assembling, So, as installation.
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