Earthing and lightning protection — testing, duties and intervals

Protective earthing and the lightning protection system are the two cheapest safeguards in a company and the two most often neglected, because they cannot be seen. Both are subject to periodic testing — measurement of earthing and lightning protection resistance is carried out every five years, and electrical installations after reconstruction or likewise every five years. The report is among the first documents an inspector asks for.

What protective earthing is

Any metal part of a machine, cabinet or installation that is not normally live can become dangerous if the insulation fails. Protective earthing is a conductive connection linking those metal parts to earth so that, in the event of a fault, the current finds a low-resistance path to earth — and not through the body of the person who touched the machine.

Both effects matter equally. First, the potential of the enclosure stays close to earth potential, so the touch voltage remains below the dangerous threshold. Second, the fault current is large enough to trip the protective device (fuse, circuit breaker or residual current device) and disconnect the circuit within a fraction of a second.

If the earth resistance is too high, neither happens. The machine stays live, nothing trips, and the next person to touch it completes the circuit through their own body.

What a lightning protection system is

A lightning protection system has three parts working as a chain: an air termination system on the roof, down conductors running along the façade, and an earth electrode in the ground. Its job is not to prevent a lightning strike but to receive it and lead it to earth along a controlled path, away from the structure, the electrical installations and the people inside.

The chain is only as strong as its weakest link. A broken down conductor, a corroded joint at ground level, or an earth electrode that has over the years lost contact with the moist soil layer turns the installation into decoration. That is precisely why the resistance is measured separately for the lightning protection system and together with the functional earthing — to establish whether the electrode still has an effective connection to earth.

For lightning protection earth electrodes, the Macedonian standard MKS N.B4.801:2000 gives a specific reference: the minimum electrode lengths need not be applied where a shorter length still achieves an earth electrode spreading resistance below 10 Ω.

Why they are tested

Earthing and lightning protection give no warning when they fail. A device that stops working is noticed the same day; earthing with resistance outside the permitted limits does not show itself until the moment of a fault. The most common causes of deterioration are predictable:

• corrosion of the electrode and the joints, particularly in acidic soil and industrial environments;
• drying and freezing of the soil, which makes the soil's resistivity vary through the year;
• mechanical damage during construction work, trenching, new foundations or car park surfaces;
• extension of the installation — a new machine, a new distribution board, a new hall not tied into the existing equipotential bonding system;
• alterations carried out by someone unfamiliar with the original scheme.

That is why the regulation treats reconstruction as an equal trigger alongside the expiry of the interval: electrical installation testing is carried out after reconstruction or every five years.

At what intervals — by parameter

The frequency is set out in Annex 1 to the Rulebook on the use of electrical installations and equipment (Official Gazette of RM no. 140/2010, amended by Official Gazette of RM no. 54/2011), adopted under the Technical Inspection Act (Official Gazette of RM no. 88/2008).

Rulebook 140/2010 applies to installations for the generation, transformation, transmission and distribution of electricity, to metering installations, to electrical devices and products rated at 380 V or above with a power greater than 1,000 W, and to products for generating electricity at 220 V to 1,000 V (Article 3). It does not apply to electrical products and devices for use in explosive atmospheres, in the chemical industry and in mining.

For facilities not covered by this rulebook, the frequency derives from the manufacturer's instructions, technical regulations and standards, and from the act adopted by the employer under Article 33 of the Occupational Safety and Health Act.

Explosive atmospheres, the chemical industry and mining

The exclusion does not mean there is no obligation there — the regime is set by the regulation for the activity itself, which ties the interval to the risk assessment rather than to a fixed table.

For mineral extraction by drilling, a plan for systematic inspection, maintenance and testing of mechanical and electrical equipment is required, drawn up by a competent person, with records kept in order; equipment in a zone where fire or explosion is possible must be suitable for that zone and have protective devices and interlock systems (Official Gazette of RM no. 163/2011, Annex, Part A, items 3.1 and 4.1). Surface and underground extraction is governed by a separate rulebook. For chemical agents, the employer takes technical and organisational measures under the regulations on equipment and protective systems for potentially explosive atmospheres (Official Gazette of RM no. 46/2010, Article 7).

So "every five years" is not an automatic answer there — the interval is set per facility, according to the zoning, the type of equipment and the risk assessment. If you do not know which regime your plant falls under, resolve that before ordering a measurement.

What exactly is measured

Testing is not a single figure but a set of measurements that together give a picture:

• earth electrode spreading resistance — how easily current passes from the electrode into the soil;
• continuity of the protective conductor and of the main and supplementary equipotential bonding conductors, by measuring electrical resistance — this verifies whether the connection physically exists along its whole length;
• insulation resistance of low-voltage conductors and cables — showing whether the insulation has aged, absorbed moisture or been mechanically damaged;
• fault loop resistance — whether the protective device will actually trip within the required time;
• correct operation of residual current devices (RCDs) — including the tripping time;
• touch and step voltage — inside and around the installation;
• lightning protection system resistance, measured separately and in combination with the functional earthing.

Measurements are taken with instruments intended for the purpose and with traceable calibration. Opusproekt works with METREL SMARTEC MI 2124, MI 2123 and MI 2120 for earthing and insulation. Technical inspection and periodic testing of lightning protection systems, protective earthing and low-voltage electrical installations fall within the scope of our accreditation IT-127 to MKS EN ISO/IEC 17020:2012, Type A. The full list is given on the equipment page.

What the report must contain

The results of the testing and the technical inspection are brought together by the independent legal entity in a report stating unambiguously whether the essential safety requirements for the equipment, given in the standards and technical specifications to which it was manufactured, have been met (Article 16 of Rulebook 140/2010). The same article gives rise to the following duties:

• where the report is positive, the independent legal entity marks the installation or equipment with its own mark, indelibly, with a clearly indicated date of performance; the location of the mark is described in the technical documentation;
• where the report is negative, the independent legal entity must notify the State Technical Inspectorate;
• the reports are retained by the user and handed over to the Inspectorate, and to the new independent legal entity in the event of a change;
• the form of the reports is set by the national standards transposing the European standards.

Where deviations or risks to safe operation are identified, the independent legal entity draws up a list of measures to be implemented to remedy them; the list is retained both by the user and by the independent legal entity (Article 17). The report is delivered to the user within seven days of the activities being carried out (Article 12).

For equipment with a registration number issued by the Inspectorate, a record sheet is also kept, containing the technical inspections and testing carried out with dates, recorded changes or reconstructions, instances where electrical or non-electrical protection operated, relocations, the schedule of periodic testing and all interventions affecting safety; the sheet is updated until the equipment is taken out of service (Article 18).

The first thing the inspector asks for

The rulebook is explicit: documentation of the inspections and testing carried out should be continuously available to the State Technical Inspectorate (Article 7). Not "to be submitted later" — available at the moment of the inspection.

To that is added the obligation under the Occupational Safety and Health Act: the employer keeps records of the inspections carried out on work equipment, and those records contain all technical documents, instruments, reports, findings and opinions (Article 37). If no such records exist, the offence is a standalone one — a fine of EUR 200 to 300 in denar equivalent for a micro and small employer that is a legal entity, EUR 300 to 400 for a medium one and EUR 400 to 600 for a large one (Article 56).

If the periodic inspections and testing of the working environment and equipment have not been carried out at all, the fine is higher: EUR 500 to 1,000 for a micro and small employer that is a legal entity, EUR 1,000 to 2,000 for a medium one and EUR 3,000 to 4,000 for a large one (Article 58). Payment within eight days of the offence payment order means half the amount (Article 54).

How we can help

Opusproekt tests protective earthing and lightning protection systems under accreditation IT-127, together with measurements of insulation resistance, continuity and residual current protection. If you do not know when the previous report expired or whether the new hall is covered by the existing system, simply send us the address of the building and a brief description. Request a quote or look at the related service for testing of work equipment and machinery.

This article is informational and does not replace professional advice. Regulations change — last updated: August 2026.