Sekundäärieristys

Sekundäärieristys, also known as double insulation, is a type of electrical safety protection used in electrical appliances. It is a method of protection that relies on two independent layers of insulation between the user and hazardous live parts. The first layer is the basic insulation, which is designed to prevent electric shock under normal operating conditions. The second layer is supplementary insulation, which is added to ensure that even if the basic insulation fails, the user will still be protected from electric shock.

Appliances with secondary insulation are typically marked with a square symbol inside another square. This symbol indicates that the appliance is double insulated and does not require an earth connection for safety. The absence of an earth wire is a common characteristic of secondary insulated equipment, as the earth connection is primarily for fault protection when only basic insulation is present.

The design principle of secondary insulation is to provide a level of safety equivalent to that achieved by earthing. This is particularly useful for appliances that are used in environments where an earth connection might be unreliable or impractical, such as in bathrooms or outdoors. The use of materials with high dielectric strength and robust construction are crucial for effective secondary insulation. Regular inspection and maintenance are still recommended to ensure the integrity of both insulation layers.