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Surge Protection Devices
Operating voltage ( Uc)
The purpose of the SPD is to protect modern electronic equipment connected to telecommunications and signalling networks with nominal system voltages up to 1 000 V (r.m.s.) a.c. and 1 500 V d.c.
These systems may be exposed to the effects of lightning and power line faults, either through direct contact or induction. These effects may subject the system to overvoltages or overcurrents or both, whose levels are sufficiently high to harm the system.
SPDs are intended to provide protection against overvoltages and overcurrents caused by lightning and power line faults.
The maximum continuous operating voltage (MCOV) Uc is the r.m.s voltage which may be applied continuously to the SPD.
The maximum discharge current (Imax), applicable to Class C/II SPD, is the maximum impulse current 8/20 μs a surge protector can withstand without destruction .The nominal discharge current (In) is the level of impulse current a surge protector Class B or Class C can withstand repeatedly (15 surges) without destruction.
Impulse current – Iimp:
The impulse current (Iimp), used in Class I test applicable to Class B SPDs, is the maximum impulse 10/350 μs current a surge protector can withstand without destruction. This test simulates the effect, on AC power surge protectors, of a direct lightning strike on an installation.
This parameter is used only for Class III test, applicable to Class C SPD and consists of the injection of a combination wave (1.2/50 μs in open circuit - 8/20 μs in short circuit).
This is the maximum voltage on the surge protector output when subjected to an impulse current equivalent to its nominal discharge current (In). Therefore, this parameter characterizes the performance of the SPD in limiting the transient overvoltage across its terminal in order to protect the equipment.
These systems may be exposed to the effects of lightning and power line faults, either through direct contact or induction. These effects may subject the system to overvoltages or overcurrents or both, whose levels are sufficiently high to harm the system.
SPDs are intended to provide protection against overvoltages and overcurrents caused by lightning and power line faults.
The maximum continuous operating voltage (MCOV) Uc is the r.m.s voltage which may be applied continuously to the SPD.
The maximum discharge current (Imax), applicable to Class C/II SPD, is the maximum impulse current 8/20 μs a surge protector can withstand without destruction .The nominal discharge current (In) is the level of impulse current a surge protector Class B or Class C can withstand repeatedly (15 surges) without destruction.
Impulse current – Iimp:The impulse current (Iimp), used in Class I test applicable to Class B SPDs, is the maximum impulse 10/350 μs current a surge protector can withstand without destruction. This test simulates the effect, on AC power surge protectors, of a direct lightning strike on an installation.
This parameter is used only for Class III test, applicable to Class C SPD and consists of the injection of a combination wave (1.2/50 μs in open circuit - 8/20 μs in short circuit).
This is the maximum voltage on the surge protector output when subjected to an impulse current equivalent to its nominal discharge current (In). Therefore, this parameter characterizes the performance of the SPD in limiting the transient overvoltage across its terminal in order to protect the equipment.
