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Street lighting

lyledunn

A specification for street lighting requires an earth electrode at the beginning of the circuit and at the end of the circuit both having an Ra of not more than 20 ohms (Is this a common spec?.) The single phase circuit will be lifted off a DNO PME supply and supply 16 columns of galvanized steel construction.  My view would be that the columns will offer a relatively good connection with earth when considered globally. I intend to measure the arrangement using the two clamp method which we use for lightning system earthing. I would be surprised if it didn't offer something below 10 ohms.

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    20Ω is a common figure - and an electrode at the end of a run supplied by PME is a common spec. for broken PEN precautions - off the top of my head I'm not sure if it hails from the BS code of practice for Earthing or the DNO GNs).

    The posts themselves aren't always reliable as electrodes - usually the "root" of purpose made posts are normally covered in bitumastic paint and often the posts are 'planted' in bits of twinwall sleeves in urban areas - to minimise ground disturbance (esp to other services) when they eventually need replacement.

        - Andy.

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    20Ω is a common figure - and an electrode at the end of a run supplied by PME is a common spec. for broken PEN precautions - off the top of my head I'm not sure if it hails from the BS code of practice for Earthing or the DNO GNs).

    The posts themselves aren't always reliable as electrodes - usually the "root" of purpose made posts are normally covered in bitumastic paint and often the posts are 'planted' in bits of twinwall sleeves in urban areas - to minimise ground disturbance (esp to other services) when they eventually need replacement.

        - Andy.

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