IEC Standard Voltages (Edition 5.0)

This document establishes the fundamental voltage levels used in electrical power supply systems and equipment designed for alternating and direct current operation. It defines a set of standardized voltages to ensure compatibility and interoperability among electrical devices across different regions and applications. The scope covers low voltage systems typically used in general industrial and commercial settings, as well as specific medium voltage ranges essential for distribution networks. By providing a unified framework for voltage ratings, the standard supports the design, manufacturing, and operation of electrical machinery and components. It addresses nominal voltages for both three-phase and single-phase systems, including considerations for frequency variations where applicable. The content serves as a reference for engineers and manufacturers to align their product specifications with global requirements. Adherence to these defined levels helps prevent system failures and facilitates the exchange of electrical equipment between different countries and grids. This specification remains a cornerstone for safety and efficiency in electrical infrastructure development worldwide.