Lightning Arrestor, while undefined but currently used throughout the industry, and Surge Arrestor are interchangeable surge protection terms. Arrestors are surge protectors but are vastly different from a Surge Suppressor i.e. Transient Voltage Surge Suppressor (TVSS). Prior to September 2009 Lightning Arrestor / Surge Arrestors and TVSS had basically the same function but were regulated by two different entities. Arrestors were evaluated under the IEEE standard C62.11 and were subjected to almost no safety testing while TVSS were evaluated under UL 1449 and rigorously safety tested.
Post September 2009, UL 1449 and 2008 NEC Article 285 require lightning arrestor / surge arrestors and TVSS for electrical systems rated under 1000 volts to follow the Surge Protective Device (SPD) requirements. These surge protectors (SPDs) are subjected to rigorous safety testing and effectively obsolescence the usage of the former terms in these applications. The term arrestor now only applies to surge protectors for electrical systems rated above 1000 volts. These arrestor applications are covered by Article 280 of the NEC.
Arrestors are typically installed on transmission lines and they divert lightning and utility switching surges to ground, clamping (or limiting) the voltage of the surge. Their function is similar to that of a hardwired SPD that is installed inside a facility. They are generally MOV-based like an SPD, but unlike an SPD they have no safety disconnectors. Their lack of safety disconnectors makes them susceptible to violent failures (i.e. explosions). This was the main reason lightning arrestor / surge arrestors under 1000V were regulated obsolete.
APT designs and manufacturers hardwired Surge Protective Devices that meet all applicable codes and standards. Contact the factory today for more information on products and training.
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