Special Small Service Installations (SSSI) refer to electrical installations that supply power to specific types of equipment or appliances, such as lighting, heating, ventilation, air conditioning, or security systems. These installations are generally smaller in scale and less complex than other types of electrical installations, such as large power systems or industrial installations.

Examples of SSSI include installations for small commercial premises, residential buildings, and small-scale industrial or manufacturing operations. These installations typically require less power and fewer components than larger ones but still require careful design, installation, and maintenance to ensure safe and reliable operation.

SSSI must comply with relevant electrical safety standards and regulations, including the Wiring Regulations, which provide guidance on the design, installation, and testing of electrical installations. They may also require certification by a qualified electrician or electrical contractor.

Overall, SSSI is an essential part of the electrical infrastructure of buildings and facilities, and proper design and installation can help ensure the safety and efficiency of these systems.