This application note discusses the nature of the threat to electronic instrumentation and communications networks posed by voltage surges induced by lightning or other causes.
The practical application of surge protection devices (SPDs) designed to prevent damage from such sources is described. It is the intention to discuss suitable techniques to protect electronic circuits and equipment from high voltages and surge currents induced by lightning and other forms of transients.
The need for surge protection
Most process control or telemetry installations are interconnected by power and signal cables which run on trays, in ducting or via overhead poles. Lightning strikes, static discharges and induction from power cabling are typical sources of transient voltages which can be coupled into signal cables and hence transmitted to electronic equipment. Field transmitters, computer terminals, etc, containing low-power semiconductor devices can be damaged by over voltages of only tens of volts. The longer the cables, the more frequent the occurrence of high voltage transients through shifts in ground potential, so devices controlling or monitoring events in remote locations are more likely to suffer from over voltages and consequent component failures. Significant damage can also be found in equipment connected by relatively short cables if the circuits or components are particularly sensitive – as is the case for computer data communication ports.
As an illustration, consider the effects of a lightning strike to a building housing control and telemetry equipment, of which the fabric is protected from a direct strike by lightning conductors and ground rods. The conductor carries the very large strike current to ground where the charge transfer is dissipated into the mass of the earth.
The effect of this current is to elevate the reference potential at the building. For example, if the strike current is 100 kA and the conductor/ground impedance is 10 Ω, then the potential above ground is 1 million volts. Exposed metalwork within the building is bonded to the same reference potential and so only small voltage differences exist that pose little risk to personnel.
However, consider a field transmitter pole-mounted away from the control building but connected to the telemetry electronics by signal cabling. Most transmitters incorporate some level of isolation from structural earth, typically 500 V. This level of isolation now has to withstand the transient voltage between the new building reference potential and its local earth potential. Many transmitters can be destroyed in this way, even though the actual lightning strike was to a protected building.
Readers wishing to find out more about surge protection devices and strategies can view the full application note at: http://instrumentation.co.za/+C13509
Unpacking the technoeconomic case for cleaner power in wastewater plants Schneider Electric South Africa
Electrical Power & Protection
Behind every reliable wastewater plant is an electrical system exposed to the effects of harmonics, voltage distortion and overloaded networks caused by fleets of variable speed drives on pumps and aerators.Together, they steadily drive up maintenance demands and elevate the risk of failure.
Read more...Energy strategy as a competitive advantage for African businesses
Electrical Power & Protection
Energy is no longer simply something that businesses consume. When managed effectively, it becomes a controllable asset that supports resilience and efficiency and sets the foundation for long-term competitiveness.
Read more...World’s fastest 14 bit arbitrary waveform generator Vepac Electronics
Electrical Power & Protection
The ARB Rider AWG-700 from Vepac is the world’s fastest 14 bit arbitrary waveform generator, with a 20 GS/s real-time update rate and 14 bit vertical resolution.
Read more...Transformers for mining house in Botswana ACTOM Electrical Machines
Electrical Power & Protection
LH Marthinusen is completing the manufacture of two 30 MVA transformers for a mining house in Botswana.
Read more...Rethinking power for Africa’s data centres Schneider Electric South Africa
Electrical Power & Protection
Africa’s digital economy is scaling faster than its power systems. If it wants resilient, competitive and sustainable data centres, the starting point must be a grid-to-chip architecture rather than a genset-first mentality.
Read more...The growing decentralisation of power grids
Electrical Power & Protection
The decentralisation of power generation is changing how national grids function. For electrical engineers, several new challenges and opportunities are on the horizon.
Read more...Custom mini substations for Zambian copper mine
Electrical Power & Protection
Recent orders to supply seventeen specially engineered mini substations for an underground copper mine in Zambia reinforces Trafo Power Solution’s track record in delivering customised electrical solutons for challenging environments.
Read more...Unifying building information into a sea of insight Schneider Electric South Africa
Electrical Power & Protection
Facility managers realise that in order to gain the most from building automation, they can longer deploy and operate technologies in isolation. Modern, integrated building management solutions address this challenge by bringing data from multiple sources and dispersed locations like HVAC, lighting, access control, lifts, generators, field devices, energy and
Read more...Smart power solutions for a low-carbon future ABB South Africa
Electrical Power & Protection
As the world marked Earth Day 2026, ABB is highlighting the role of low-voltage smart power solutions in improving energy efficiency, reducing emissions and enabling more sustainable infrastructure.
While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.
printer friendly version