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534.4.1.4

lyledunn

I have a DNO supply into a 200A switchfuse at the origin. Nothing else connected there. A distribution cable then travels some 30m before it enters a panel board. I can’t see any technical reason why the SPD should not be located at the the panel board thereby being remote from the main intake and in contravention of this regulation. Am I missing something about this black art?

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    I guess the principle is that by putting the first SPD at the panelboard, you're not protecting the equipment downstream of that. If all you have is a simple switchfuse and cable and the chances of having to deal with lightning are remote (e.g. no LPS on the building) then I suspect it's not going to be a huge risk in practice. The regs however will be based on common principles and will have to assume the worst case where you incoming equipment really might not be able to withstand anything above 4kV (see table 443.2).

    There's also the consideration for bonding - if main bonding were connected (directly or indirectly) to the intake position rather than the panel board, then SPDs at the panel board wouldn't keep the difference between electrical installation conductors and extraneous-conductive-parts as low as it might be during a surge - which can lead to larger than necessary potential differences all over the place as the extraneous-conductive-parts wend their way through the installation.

       - Andy.

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  • 0

    I guess the principle is that by putting the first SPD at the panelboard, you're not protecting the equipment downstream of that. If all you have is a simple switchfuse and cable and the chances of having to deal with lightning are remote (e.g. no LPS on the building) then I suspect it's not going to be a huge risk in practice. The regs however will be based on common principles and will have to assume the worst case where you incoming equipment really might not be able to withstand anything above 4kV (see table 443.2).

    There's also the consideration for bonding - if main bonding were connected (directly or indirectly) to the intake position rather than the panel board, then SPDs at the panel board wouldn't keep the difference between electrical installation conductors and extraneous-conductive-parts as low as it might be during a surge - which can lead to larger than necessary potential differences all over the place as the extraneous-conductive-parts wend their way through the installation.

       - Andy.

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