Globally, the threat of lightning damaging your network is very real.
In August, a lightning strike to a transmission circuit in the UK triggered events that led to a loss of power for around 1.1 million customers and caused chaos on transport networks.
In South Africa, with a ground flash density (GFD) up to 20 times higher and the lightning season underway, the road to protection planning must not be avoided.
Lightning is a threat to people and assets when the strike, or any consequence of the strike, transfers energy to the person or asset.
The energy transfer can be by way of the direct transfer of charge through the person or asset (electric current flow) or an increase in voltage, which induces subsequent currents (and voltages) that threaten the person or asset.
An effective lightning protection plan needs to be cost-effective, aesthetically inconspicuous and above all, protect people and assets to an acceptable level.
Items to take into consideration include:
• Where lightning strikes (Reference: SANS 62305 – part 1, section 5.1.2)
• What the lightning strike will pass through and possibly damage (Reference: SANS 62305 – part 1, section 5.1.2)
• What losses may occur (Reference: SANS 62305 – part 1, section 5.2)
Now review these six areas (A to F) to ensure your protection plan and measures are comprehensive.
A. There are four main physical areas of an asset to consider when implementing an effective lightning protection plan and these pertain to:
(a) Direct and indirect lightning discharges
(b) Location of the discharges
They are: (Reference: SANS 62305 – part 1, section 5.1.2)
- Flashes to the structure (direct strike);
- Flashes near the structure (indirect strike);
- Flashes to any lines connected to the structure (direct strike); and
- Flashes near any lines connected to the structure (indirect strike).
B. The second consideration is whether people or assets are a possible path for lightning current flow to ground. That is: (Reference: SANS 62305 – part 1, section 5.1.2)
(1) Can people be injured or killed, or
(2) Can assets be damaged, or
(3) Can any asset malfunction as a consequence of absorbing the lightning current?
C. The third consideration is the extent to which you can afford to implement lightning protection – quantifying affordability must also include the losses incurred for the portion for which the lightning protection was not adequate. A lightning protection plan can also include evacuation measures prior to a lightning storm such that zero loss of life and injury becomes possible.
D. Protection measures to protect people and livestock from the lightning current at structures include insulating any exposed conductive parts, constraining any voltage rise at or near the location, warning signs, early warning measures and restricting access.
E. Protection measures to reduce physical damage include diverting lightning current through controlled and isolated electrically conducting paths such that the current will not flow through the assets you are trying to protect.
That means that the plan includes measures to:
• Intercept the lightning strike itself to a controlled termination point – known as an air-termination system (ATS);
• Channel the lightning current (transfer of charge) down the structures in an insulated and isolated path towards the earth – known as a down-conductor system (DCS);
• Drain the lightning current into the earth where the lightning was trying to go in the first place – known as an earth-termination system (ETS).
The earthing aspect of lightning protection is therefore as important in a successful lightning threat management plan as the ‘above ground’ aspects.
The ATS, DCS and ETS make up the ‘lightning protection system’ (LPS).
The LPS must not, at any stage, create voltage rise within or without the structures in close proximity to the assets, and therefore all parts must have equipotential bonding and be adequately separated from the assets being protected.
F. Protection measures to avoid malfunction relate to the management of electrical and electronic signals, reducing the potential for transient rise in induced voltages and currents.
Surge protection devices (SPD) ensure reduction or constraining voltage rise but often also ensure equipotential localised conditions when there is a significant voltage rise within the structures.
Lightning is a high frequency phenomenon and therefore inductive and capacitive elements will influence the response of the implemented protection schemes.
Regulations and standards in the South African market
A lightning threat management plan must link into the electrical Certificate of Compliance that is a legislated requirement for all properties in South Africa.
The South African legislation and regulations facilitate LPS compliance with the installation safety report (ISR) and the maintenance certificate (MC) available in SABS standard SANS 10313.
LPS Installation Safety Report
The risk must be documented and the associated lightning protection level (LPL) stated. The design of the solution, whether it is complicated or extremely simple, must align with the stated LPL and the designer must be acknowledged.
The work carried out must also be documented with the materials used and the method of construction, and with the installer acknowledged.
An inspection should be part of the plan whereby the service delivered has a starting installed reference condition, with the inspector acknowledged.
Names must be acknowledged for future reference when either maintenance, refurbishment or amendments are required.
LPS Maintenance Certificate
The LPS is a system only required when lightning occurs. The owner is mostly unaware of its presence until it is required and will not know if it has deteriorated. All lightning protection systems must therefore be routinely inspected.
South African standards relevant to creating an effective lightning and earthing plan are listed below.
SANS 62305 – 4 parts – “Protection against lightning”
- General principles
- Risk management
- Physical damage to structures and life hazard
- Electrical and electronic systems within structures
Physical damage to structures and life hazard (a bridging standard linking international norms to South African conditions).
SANS 62561 – Product standard 7 parts – “Lightning protection system components”
- Requirements for connection components
- Requirements for conductors and earth electrodes (the test report is covered here)
- Requirements for isolating spark gaps (ISG)
- Requirements for conductor fasteners/holders
- Requirements for earth electrode inspection housings and earth electrode seals
- Requirements for lightning strike counters
- Requirements for earthing enhancing compounds
Africa is the lightning capital of the world with some regions in Africa experiencing the highest lightning ground flash densities in the world – according to NASA’s lightning tracking technology, which has recorded lightning strikes to the earth for the past 18 years.
These statistics have serious consequences for lightning protection designers’ plans to protect people and assets in high lightning flash regions. However, using the regulations, standards and guides outlined in this article will reduce the threat substantially. ESI
About the author
Richard Evert is the National Director of the Earthing and Lightning Protection Association (ELPA), which is supported by institutions such as Wits University, the Electrical Contractors Association of South Africa (ECA), the South African Institute of Electrical Engineers (SAIEE), the Approved Inspection Authority (AIA) and the South African Department of Labour.