GIS or Gas-Insulated Switchgear is an electrically powered device utilized in various high-voltage power stations and substations. Its body is enclosed by solid metal and includes equipments like circuit breakers, switches and disconnectors. The GIS chamber is usually filled with an inert gas, Sulfur Hexafluoride (SF6), which has insulation properties.
The GIS switchgear filled with an insulated gas, SF6, protects the distribution and supply of electrical power when necessary. The breaker contacts are closed normally.
During a failure in the electrical system, these breakers get disconnected, forming an arc between them. These movements of breakers allow the high-pressure SF6 to enter the chamber while the arc is occurring. The characteristics of SF6 gas help the arc to get extinguished.
As the arc extinguishes, the pressure of the SF6 gas also decreases, and it is stored in a low-pressure tank and then in a high-pressure tank when it is ready for reuse. The insulation of SF6 makes GIS much more reliable for medium and high-voltage powered substations.6
The usual test procedures according to IEC are as follows:
GIS testing involves the following procedures:
After GIS testing, a report is generated based on the issues identified.
During GIS testing, it is mandatory to perform a voltage withstand test according to IEC’s standards. Laxmi Associates has experience of more than 15years in testing, with a large team of engineers and technicians.
GIS is designed to be reliable and compact with the working principle based on SF6. To fully utilize the functions of GIS, proper testing must be done. It ensures the reliability and security of the equipment. Moreover, the estimated service life of a gas-insulated switchgear is approximately 35 – 50 years, during which its insulation system has to withstand all voltage loads without maintenance; therefore, it should be tested regularly.
Electrical Substations are classified into several types depending on various factors:
Based on insulation
Based on services rendered
The different types of Switchgear available commonly are: