Transient suppression is a common technique for reducing or mitigating transient voltages. A Transient Voltage Surge Suppressor (TVSS) is like a very fast switch. It is the most common type of power conditioning equipment.
TVSSs have been around in their current form for many years. The basic concept of a TVSS is to either limit the peak transient voltage through absorption, or divert the energy to another path. TVSSs are available in many different sizes and are typically one of three different technologies. These are gas discharge tubes, silicon avalanche diodes, and metal oxide varistors.
For protection inside facilities, the most common technology is metal oxide varistors, or MOV. These can be purchased in sizes ranging from stand alone products for receptacles to large systems for panel or service entrance applications. For lightning protection use equipment that conforms to ANSI and UL guidelines only. The IEEE Emerald book provides additional information regarding the use and installation of lightning surge arrestors.