This standard gives guidance on writing the technical specification for the procurement of static a.c. and d.c. high power convertors for use in electricity generating stations (power stations). This Guide for procurement is not applicable to equipment for use in the nuclear reactor plant area of nuclear power stations. Other possible applications of such equipment have not been considered in the preparation of this Guide. This Guide covers each type of power convertor, i.e. rectifier, inverter, static excitation system, conversion of a.c. to a.c./d.c. to d.c. and switching, for the purpose of changing and/or controlling one or more characteristics. This type of equipment is used for many applications such as motor drives and actuators, e.g. variable frequency starting equipment, a.c. and d.c. power supplies for computers and instrumentation, in chemical process plant, e.g. rectifiers for electrolysis in hydrogen production, in mechanical plant, e.g. electrostatic precipitators, etc. For additional, or specific, requirements for batteries, battery chargers or uninterruptible power supplies (UPS) refer to the relevant guides in this series. The equipment covered by this Guide is defined by its function rather than design type. Therefore, the guidance to the specification is stated in performance terms rather than being specified by a detailed description of the equipment to be supplied. This Guide indicates to potential purchasers how their specification should be prepared so that: - the equipment type and capacity interfaces correctly with other elements of the systems; - predicted performance is achieved; - ancillary equipment is properly sized; - reliability, availability and safety requirements are achieved; - proper consideration is given to the evaluation process and the quality measures to be applied. This Guide does not determine the type of specification (e.g. detailed, performance, functional) or the extent of supply for any given contract which is