The special protection device for low-voltage surge protector (SSD) is an external disengagement device of the surge protector used in the low-voltage power supply system, which can withstand the expected surge current at the installation of the standby surge protector and the power frequency overcurrent caused by the failure of the surge protector, and has the characteristics of power frequency small current action.
The function of spd for lightning protection is to limit transient overvoltage. It is generally connected in parallel on the main circuit and has the property of high impedance. When TOV occurs in the circuit, it will conduct and discharge the surge current. At this time, it is the conduction mode and can be regarded as a directly grounded conductor, which can discharge the surge current in the main circuit to the grounding wire.
While the surge backup protector cannot be used alone, it must be connected in series with the surge protector against lightning and connected to the front of the SPD surge protector, which usually will not affect the normal working capacity of the surge protector against lightning, but will be quickly broken when the power frequency short-circuit current appears in the line.
There are great differences between antenna surge protector and backup protector. Surge protector is used to protect the electrical safety of the main circuit and prevent lightning current from damaging the protected electrical facilities. The backup protector is a backup protection device used to protect the surge protector from being damaged by power frequency short-circuit current and protect the surge protector from heating and fire. The backup surge protector can not cut off the power frequency short circuit protection in the power frequency surge protector itself. Therefore, both of them are very important. At the same time, neither of them can replace each other. The lightning protection measures in electrical equipment need the mutual cooperation of surge protector and backup protector.