This CIGRE Green Book provides the entire know-how about switches in a high voltage system. The switching equipment includes circuit breakers, vacuum interrupters, disconnecting switches, and earthing switches used in AC & DC transmission and distribution systems. The Green book describes different switching equipments and their roles in the power systems. It explains the fundamental switching behaviors in power systems targeted for practitioners and students and joining electrical industries. The Green book also covers fundamental specific subjects including DC circuit breakers, controlled switching, fault current limiting devices and future technologies. Like all Green books, this book covers the cumulative understanding of numerous experts in the CIGRE study committee. It offers the approved and outstanding practical knowledge of CIGRE Study committee A3 and was collected by Dr. Hiroki Ito.