Richard Evert of the Earthing and Lightning Protection Association (ELPA) looks at various lightning protection systems and lightning surge protection measures. What’s new?
Knowledge, awareness and cost
In most aspects of our society, how we do things and the tools we use determine how difficult it is to get things done. Our knowledge, ability to understand our needs, tolerance, and expectations influence our motivation to question the way we do things.
Lightning protection is no different. A catastrophic lightning event where a person is permanently injured, business production is disrupted, or electronic equipment is damaged could lead to considerable financial loss, instantly increasing the desire for knowledge about lightning protection.
A lightning protection system (LPS) diverts direct lightning strikes safely to ground, minimising the threat to humans and avoiding production disruption and damage to electrical and electronic equipment. Lightning surge protection measures (SPM) control overvoltages from indirect lightning strikes.
New concepts in standards
Standards explaining best practices for lightning protection manage risk and cannot be deployed as regulatory standards.
New concepts are introduced into standards when they improve the effectiveness of fulfilling the purpose of the standard.
The IEC 62305 standards published in 2024 introduced three significant changes regarding lightning current flow in the external LPS part of an LPS:
Isolated LPS: The isolated LPS has no physical contact with the structure to be protected. This LPS prevents any dangerous lightning currents that could ignite the flammable or explosive contents and destroy the structure. The concept of an isolated LP" is not new and has been adopted across South Africa for many years to protect thatch roof structures.
Attached LPS: An attached LPS that has physical contact with the structure being protected.
Electrically insulated LPS: An attached LPS that has no electrical contact with the structure being protected. The standard does not dictate the insulation level of the external LPS component.
New products: LPS insulated conductors
Electrically insulated conductors are well understood. In South Africa, power transformers with bushings that manage voltages in excess of 440 kV are common on the 765 kV extra high voltage (EHV) networks. Electrically insulated conductors will fail when the critical breakdown voltage of the insulation is reached.
An electrically insulated LPS component has better insulating characteristics than air. It is used in areas where the required air separation distance for the standard LPS component cannot be achieved.
The voltage on the insulated LPS component is dependent on the lightning peak current, the surge impedance of the conductor bonding this component to ground and the installed earth resistance. Considering a common 10 kA lightning strike (highly probable), rise time of 5 microseconds, and an earth resistance of 10 Ohms, it will be possible to experience upwards of 200 kV on the insulated LPS component every time it operates.
Increased use may lead to accelerated ageing and insulation deterioration, which in turn would reduce the insulation effectiveness of the component.
No international standard for these components has yet been published.
New perspectives on old clauses in standards
Awareness of the meaning of concepts in standards is vital to appropriately using standards. It is natural, in a country where we have 11 official languages, that words can be misinterpreted. Subsequent controversial debates amongst laymen can contribute to further uncertainty and misinterpretation.
Lightning SPM and internal LPS
The purpose of an internal LPS is often misunderstood. It addresses dangerous voltages produced by the external LPS. It exists with an external LPS and does not address indirect lightning events.
Indirect lightning does not strike the structure or the external LPS. The lightning protection designer must identify the threat of indirect lightning and include suitable lightning SPMs in the lightning protection scheme design.
The surge protection design adopted in both the internal LPS and the lightning SPM falls outside the scope of work the electrician is responsible for (SANS 10142-1).
Maximum earth resistance of an LPS: The induced voltages from an external LPS during a direct lightning strike will depend on the magnitude of the lightning peak current and the earth resistance of the external LPS. A legislated maximum allowable earth resistance value has no relevance in the successful operation of an internal LPS.
A good designer will always insist on having soil resistivity values. After designing an optimal earth electrode in the available space, they will then complete the internal LPS design. Future maintenance will require that the design earth resistance value must be maintained at all times.
New technology and economic decisions
New technologies in lightning protection are more difficult to validate than those adopted in industries where the primary element (such as electricity in an electrical installation) has a high probability of being present during testing.
The most common struggle facing every risk manager is available reliable statistics by which to make sound economic decisions. It is our duty as ELPA to contribute to and support the development of reliable statistical databases that help those vested property stakeholders make the best decisions for their assets and the safety of the people on their premises.