Signal Line Surge Protectors Can Be Selected Based On Two Factors
1) Selecting the Voltage Protection Level (UP)
The UP value should not exceed the impulse withstand voltage rating of the protected equipment. The UP requirement requires good coordination between the surge protective device and the insulation of the protected equipment.
In low-voltage power supply and distribution systems, all equipment must have a certain surge withstand capability, known as impulse overvoltage withstand capability. When impulse overvoltage withstand values for various equipment in 220/380V three-phase systems are unavailable, the specifications specified in IEC 60664-1 and GB 50057-1994 (2000 edition) may be used.
2) Selecting the Nominal Discharge Current In (Inrush Current Capacity)
The peak current flowing through a surge protector, 8/20 μs current waveform. This is used for Class II classification testing of surge protection device and as a preconditioning measure for Class I and Class II classification testing of SPDs.
In is the maximum peak impulse current that the SPD can withstand a specified number of times (generally 20) with a specified waveform (8/20 μs) without substantial damage.
