In the first part, main components of Gas Insulated Metal/Enclosed High Voltage Substation are described together with caracteristics of gas 𝑆𝐹6. Descibed componets are: Current Transformers, Voltage Transformers, 𝑆𝐹6 Circuit Breakers, Busbars, Surge Arresters and Power Transformers. Cross sections with marked parts are shown for each component. Furthermore, operation pinciples and technical caracteristics of mentioned components have been described. 𝑆𝐹6 Circuit Breakers are described through elaboration of Circuit Breakers choices, quenching of electric arc and drive mechanism. In recent times there has been development of gas insulated transformers which contain all advantages of gas insulated metal-enclosed 𝑆𝐹6 substations with which they are easily merged. In the last part, comparison regarding economical aspects and tehnical characteristics of air insulated substations and metal-enclosed gas insulated substations has been carried out. There 58 is a constant increase in application of GIS technology because of its cost effectiveness (low cost drive, long continuance), reliability, space compactness, environmental friendliness and personnel safety.