Isolationsklass

Isolationsklass, eller isolationsklassificering, is a term used in electrical safety to describe the level and arrangement of insulation in electrical equipment to prevent electric shock. The classification helps define which protective measures are required during normal use, fault conditions, and maintenance. It is embedded in international and European standards and reflected in product markings and technical documentation.

The most common isolationsklasser are Class I, Class II, and Class III. Class I equipment relies on basic insulation for live parts and uses a protective earth connection to provide safety in case of insulation failure. Class II equipment uses double or reinforced insulation and does not depend on a protective earth for safety. Class III equipment is designed to operate from a safety extra-low voltage supply (SELV or PELV) and provides protection primarily through low voltage and additional isolation. Some older equipment is described as Class 0, which has basic insulation and no protective earth, a configuration that is generally considered unsafe by modern standards.

Marking and usage: Class II devices are commonly identified by the square-in-square symbol, while Class I devices may show a grounding symbol. Class III labeling is less standardized but typically indicates SELV operation. In practice, the choice of isolationsklass depends on the intended use, environmental conditions, accessibility of parts, and regulatory requirements. It informs design decisions, earthing schemes, and inspection regimes.

In Sweden and other European contexts, isolationsklass aligns with EN/IEC standards such as IEC 61140 (Protection against electric shock) and EN 60364 (Electrical installations). It remains a key concept for engineers, manufacturers, and safety professionals when evaluating and selecting electrical equipment.