Lightning protection system inspection and maintenance

Short answer. A lightning protection system (LPS, as defined in IEC 62305) loses effectiveness over the years through corrosion, mechanical damage, weather and lightning discharges. For that reason Part 3 of the standard calls for inspection at four points: during construction, on completion of the installation, periodically, and after alterations, repairs or a lightning strike. Table E.2 sets the maximum intervals by protection level, and every inspection ends in a report that is filed with the design.

When an LPS is inspected

Clause 7.3 of IEC 62305-3:2010 lists the occasions:

• During construction, to check what is later covered up, such as foundation earth electrodes and the connections to reinforcing steel.
• On completion of the installation, to confirm that the system matches the design.
• Periodically, at an interval that depends on the nature of the structure, corrosion conditions and the class of the LPS.
• After alterations or repairs, or whenever lightning is known to have struck the structure.

The purpose (clause 7.2) is to confirm that the LPS complies with the design, that all components are in good condition and free of corrosion, and that any services or structures added later have been bonded into the system.

What a periodic inspection checks

The standard asks for special attention to four points:

• Deterioration and corrosion of the air-termination system, conductors and connections.
• Corrosion of the earth electrodes.
• The earth-termination resistance value.
• The condition of connections, equipotential bonding and fixings.

Annex E.7 (informative) extends the list. A visual inspection looks for loose connections or accidental breaks in conductors and joints, parts weakened by corrosion (especially at ground level), visible earth connections that are intact, conductors that are properly fixed, extensions to the structure that call for additional protection, signs of damage to surge protective devices (SPDs) or blown fuses, and correct equipotential bonding of new services.

A complete inspection adds tests: electrical continuity of the parts that cannot be seen, especially those hidden in the construction, and measurement of earth resistance. Local electrodes are measured in isolation, with the test joint between the down-conductor and the electrode open. SPDs without a visual indicator are tested following the manufacturer’s guidance or test equipment. For the fundamentals of the measurement, see earth resistance: what the test measures.

Because soil resistivity changes with the seasons, Annex E.7 recommends allowing for it by measuring at different times of year. If resistance rises steadily from one inspection to the next, an improvement to the earthing system should be considered.

Intervals from Table E.2

Where the authority having jurisdiction sets no requirements of its own, Annex E.7 gives these maximum intervals between inspections, in years:

Two notes to the table complete the picture:

• Critical situations. These include structures with sensitive internal systems, office buildings, commercial buildings and places where many people may be present. They also include LPS parts under heavy stress, such as flexible bonding bands in windy locations, SPDs on pipework, or cable connections exposed to the weather.
• Structures with a hazard from explosive materials. Visual inspection every six months and electrical tests once a year. It is acceptable to run the tests on a 14 to 15 month cycle if it is useful to measure earth resistance at different times of year and see its seasonal variation. These structures have additional requirements in Annex D of the same part of the standard.

The text of Annex E.7 advises a visual inspection of the LPS at least once a year, and a complete inspection and test every two to four years. Table E.2 is what sets the maximum intervals by level: for levels III and IV it allows up to two years between visual inspections.

Annex E.7 also advises inspecting more often where the climate is severe or the environment is corrosive, and notes that building insurers or the client’s maintenance program may require a complete test every year.

These values are recommendations from the informative annex. On a specific project, the applicable local code and the maintenance plan defined by the LPS designer together with the owner take precedence.

Maintenance: how it differs from inspection

Inspection verifies; maintenance corrects and keeps the system at its design condition. Annex E.7.3 calls for a maintenance program for every LPS, with a routine checklist that allows results to be compared with earlier ones. It should include:

• Verification of all conductors and components.
• Electrical continuity of the installation.
• Measurement of the earth-termination resistance.
• Verification of the SPDs.
• Refixing of components and conductors.
• Confirmation that the effectiveness of the LPS has not dropped after extensions or changes to the structure.

If an inspection finds damage, the standard calls for repair without waiting for the next maintenance cycle (clause 7.4 and Annex E.7.3). The program should be kept up to date with the current edition of the standard and modified if the use of the building changes.

Inspection of the LEMP protection measures (SPM) for equipment (Part 4 of the standard) follows the same logic: documentation, visual inspection and measurements, with the Table E.2 intervals as a reference if the authority requires nothing else.

Records each inspection must leave

The inspector should first receive the LPS design report, with its criteria, description and drawings, and the earlier inspection and maintenance reports. On completion, the inspector writes a report that is kept with the design report and the earlier ones. According to Annex E.7.2.5, the report includes:

• General condition of the air-termination conductors and other air-termination components.
• Level of corrosion and the condition of the corrosion protection.
• Firmness of the fixing of conductors and components.
• Earth resistance measurements for the system.
• Any deviation from the requirements of the standard.
• Changes and extensions to the LPS and the structure, together with a review of the construction drawings and the design description.
• Results of the tests carried out.

Maintenance records, including corrective actions, are kept in the same file. They are used to compare trends and to review the maintenance program.

What not to do

• Do not inspect or test when a thunderstorm is threatening.
• Do not accept a visual inspection of joints that were buried or embedded in concrete: these are verified during construction and with continuity tests.
• Do not compare earth resistances measured at different times of year without considering the condition of the soil.
• Do not file the inspection without the report: without a record there is no trend to compare.

We can help with earthing

Earth resistance and continuity are part of LPS inspection and of the earthing of a substation or plant. At Tiza Group we carry out the field measurements, in Colombia or elsewhere on request, and deliver the readings and their interpretation as part of our testing and commissioning services. For a preliminary estimate of the resistance of rods or a grid, you can use our earthing resistance tool.

Guides in the same series

Structures with an explosion hazard have requirements of their own, explained in lightning protection for structures with an explosion hazard. Inspection of the internal protection measures is covered in SPM measures against LEMP, and the earthing being measured is covered in LPS earthing: type A and type B electrodes.

Related guides

• IEC 62305: lightning protection, what each part covers
• Lightning protection in areas with an explosion hazard
• SPM measures against LEMP: what they are and how they are managed
• LPS earthing: type A and type B electrodes
• Earth resistance: what the test measures, and IEEE 81

References

• IEC 62305-3:2010, Protection against lightning, Part 3: Physical damage to structures and life hazard: clause 7 (maintenance and inspection), Annex D.6 (structures with a hazard from explosive materials) and Annex E.7 (inspection and maintenance guide, Table E.2).
• IEC 62305-4:2010, Part 4: Electrical and electronic systems within structures: clause 9.3 (inspection of the SPM).

Frequently asked questions