Main Important Specifications of Surge Protector

Some specifications will define a surge protector for AC mains and some communication protection.

Clamping voltage — better known as the let-through voltage. This specifies what voltage will cause the metal oxide varistors (MOVs) inside a protector to conduct electricity to the ground line.[1] A lower clamping voltage indicates better protection, but a shorter life expectancy. The lowest three levels of protection defined in the UL rating are 330 V, 400 V and 500 V. The standard let-through voltage for 120 V AC devices is 330 volts.[2]

Joules — this number defines how much energy the surge protector can absorb without failure. A higher number indicates greater protection and longer life expectancy because the device will divert more energy elsewhere and will absorb less energy. More joules conducting the same surge current means a reduced clamping voltage. Generally, 200 joules is undersized protection since harmful spikes are significantly larger than this. Better protectors exceed 1000 joules and 40,000 amperes. If properly installed, for every joule absorbed by a protector, another 4 or 30 joules may be dissipated harmlessly into ground.

Response time — Surge protectors don't kick in immediately; a slight delay exists. The longer the response time the longer the connected equipment will be exposed to the surge. However, surges don't happen immediately either. Surges usually take around a few microseconds to reach their peak voltage and a surge protector with a nanosecond response time would kick in fast enough to suppress the most damaging portion of the spike. [3]

Standards — The surge protector may meet IEC 61643-1, EN 61643-11 and 21 , Telcordia Technologies Technical Reference TR-NWT-001011, ANSI / IEEE C62.xx, or UL1449. Each standard defines different protector characteristics, test vectors, or operational purpose. For example, to pass UL1449 a protector has to remain functional after a series of 22 test surges. The protector can safely fail later tests, including sustained overvoltage. [4] EN 62305 and ANSI / IEEE C62.xx define what spikes a protector might be expected to divert. EN 61643-11 and 21 specify both the products performance and safety requirements. IEC only writes standards and does not certify any product to meet those standards. IEC Standards are used by members of the CB Scheme to test and certify products for compliance. None of those standards say a protector will provide proper protection. Each standard defines what a protector should do or might accomplish.