>>>>>>>>>>>>>>>>>> Original Message <<<<<<<<<<<<<<<<<<
On 05/08/2003, 17:37:26, Anil Allamaneni <[email protected]> wrote
regarding Lightning Surge Characterization/Standards:
> Greetings folks,
> We have products that meet all the Surge requirements
> of NEBS GR-1089, FCC-68 and EMC 4-5. But, the same
> products are continuously failing in the field due to
> real-world lightning strikes.
> I have spoken to four other manufacturers who make
> similiar interfaces (DSL) and they all have the same
> problem : they meet the standards, but fail in the
> real world.
Do you really want to test to lightning strikes as in the real world? I
suspect that you may find the cost prohibitive. A direct strike will
literally burn out just about anything and one in the vicinity will
induce high voltages and energy into the product. Some years ago, we had
a sensor with measurement system in a field (literally). The data line
was tie wrapped to a long length of iron water pipe. When the pipe was
struck, there wasn't much left of the equipment other than a charred mess of
electronics. I doubt anything could have saved that equipment from
fatal damage. So how much energy should a device be able to withstand? If your
experience is one of frequent expensive failures, then you need to
increase the level of protection since the additional cost would be
recovered by the reduction in failures. As regards the standards, they
are not meant to protect against every single possibility – fortunately
otherwise the increased immunity levels demanded would force product
costs to rocket.
Regards,
Neil Helsby
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