This part of IEC 62271 specifies requirements for gas-insulated metal-enclosed switchgear in which the insulation is obtained, at least partly, by an insulating gas or gas mixture other than air at atmospheric pressure, for direct current of rated voltages of 100 kV and above, for indoor and outdoor installation. This document includes rules for service conditions, ratings, design, and construction requirements. Test requirements are defined and criteria to proof for passing type and routine tests in this document for development and manufacturing of DC switchgear. For the purpose of this technical specification, the terms “GIS” and “switchgear” are used for “gas-insulated metal-enclosed systems”. The Technical Specification IEC TS 62271-5 defines common specification requirements for high-voltage direct current (DC) switchgear and controlgear covering both types of air insulated (AIS) and gas insulated (GIS) equipment of DC substations.