The symbol of surge backup protector is usually expressed as "SCB". In system drawings, the symbol of surge backup protector (SCB) usually appears together with surge protector (SPD) to provide additional protection. The main function of surge backup protector is to provide backup protection when surge protector fails to prevent equipment from being damaged by overvoltage and surge.
The functions and differences of surge protector (SPD) and surge backup protector (SCB) in the system are as follows:
Surge protector (SPD): Mainly used to limit overvoltage and discharge surge current, usually connected in parallel with the protected equipment. When overvoltage occurs, SPD can play the role of shunting and voltage limiting to prevent excessive current and voltage from damaging the equipment.
Surge backup protector (SCB): As a front-end series device of surge protector, when SPD fails, SCB provides backup protection to prevent equipment from being damaged by overvoltage and surge. SCB is often referred to as a surge backup protection device or external disconnector.
In system drawings, the representation of surge protectors and surge backup protectors is also different:
Surge Protector (SPD): In weak current system diagrams, the power surge protector symbol is parallel, while the signal surge protector symbol is series.
Surge Backup Protector (SCB): Usually appears with SPD, represented by the "SCB" symbol, to provide additional protection functions.