Originally Posted by rennervision
One nanosecond seems to be the preferred standard from anything I've read. Here's just a few examples from just a few minutes of searching:
And a lot of your high quality surge protectors proclaim themselves to have a response time of < 1 nanosec.
Are you saying a response time this quick is unnecessary overkill?
I don't have the definitive answer but I do think the issue is twofold--
There are different devices used in surge protection MOV's, Silicon Avalanche Diode, Silicon Thyristor Diode, gas discharge tubes, hybrids etc. They have different characteristics, including how fast they react. Gas tubes are slower but can manage a lightning strike.
There are different sources of a surge with different characteristics-- such as an AC power line overvoltage, a direct lightning strike, or induced currents from a lightning strike.
I'm willing to wager that all SPDs using similar technology have similar rise times: all MOVs will be similar, all gas tubes similar and so on. The fact that standard testing of SPDs uses .5 and 10 microsecond rise times suggests to me that a device that begins to act a thousand times faster vs. 500 times faster is not the critical factor.
If two point of use SPDs have significantly different rise times, I would ask the manufacturer about the technology used and suitability for my purposes.
Getting back to the cable entrance device pictured in this thread--it is fairly standard for the application.
By the way lightning is DC; it may pulse but it is still DC.