Health, Safety & Quality Consultancy
Lightening Protection Systems—Testing Requirements
The Electricity at Work Regulations 1989 require that Lightning Protection Systems (LPS) are tested in accordance with BS6651. This standard states that systems should be tested at maximum intervals of 12 months.
Some companies recommend that the system is tested at intervals of 11 months, meaning that over a 12 year period it will have been tested throughout every season of the year. Applying this tried and tested method will allow the effect of seasonal variations in resistance or other characteristics of the system to be taken into account.
If this check is not carried out, then vital components within the LPS, which may have suffered from corrosion and which could exhibit a high resistance, could be missed. This will have a detrimental effect on the whole LPS making it an unattractive high impedance path for the lightning current to follow.
To minimise this problem, along with the regular inspections, the correct materials should be selected in accordance with the recommendations of BS6651.
Examination is recommended to meet the requirement of BS6651. As well as a very thorough inspection, to ensure that the installation complies with the current Regulations, the following testing is required.
The value of the electrode should be measured. Previously this meant isolating the electrode from the main lightning protection conductors. This could not be carried out during any lightning activity and precautions where required when breaking the link between the electrode and the lightning conductors, since it was possible for an excessive voltage to appear across the open link, should there be a fault to earth on the electricity supply network. Clip on type impedance measuring instruments are now available for this and do not require the electrode to be disconnected.
Once measured, the value of the earth electrode should be compared with the design value, or that obtained during the previous test.