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Testing Lightning Conductors and Earth Electrodes.

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I am just curious. A local church is having its lightning protection system inspected and tested any A.N. Other. It is an old Norman church with a tall tower.


The downleads are copper and have no disconnection points above the earth electrodes. I have seen inspection joints on other buildings so that the earth electrodes can be independently electrically tested.


How is testing carried out when the downleads are continuous please?


Thanks in advance.


Z.

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  • Former Community Member
    0 Former Community Member
    The test requirement is to ascertain the overall ohmic resistance of the system - ie less than 10 Ohms. You can test each electrode individually (and you need test clamps for that purpose) and calculate the overall resistance  - or you can test the overall system resistance (but you need to be clear that any bonding to the MET has been isolated (and any other fortuitous connections to say roof air handling plant, cold water tank up or down feeds, lift rails etc)


    Generally, you would expect to see simple test clamps on a system that has no further below ground interconnections between simple driven electrodes (perimeter ring tape for example - or connection to the facility foundation slab)


    In most cases, it would be usual to test on a fall of potential method or Wenner method- some systems may have a deliberate remote electrode position (up to 90m away) from interconnected systems to assist with this (usually several electrodes to allow a near, middle and far condition on a 4 wire instrument)


    Loop (or clamp) testing may tell you something, but not necessarily what you want to know


    Regards


    OMS
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  • Former Community Member
    0 Former Community Member
    The test requirement is to ascertain the overall ohmic resistance of the system - ie less than 10 Ohms. You can test each electrode individually (and you need test clamps for that purpose) and calculate the overall resistance  - or you can test the overall system resistance (but you need to be clear that any bonding to the MET has been isolated (and any other fortuitous connections to say roof air handling plant, cold water tank up or down feeds, lift rails etc)


    Generally, you would expect to see simple test clamps on a system that has no further below ground interconnections between simple driven electrodes (perimeter ring tape for example - or connection to the facility foundation slab)


    In most cases, it would be usual to test on a fall of potential method or Wenner method- some systems may have a deliberate remote electrode position (up to 90m away) from interconnected systems to assist with this (usually several electrodes to allow a near, middle and far condition on a 4 wire instrument)


    Loop (or clamp) testing may tell you something, but not necessarily what you want to know


    Regards


    OMS
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