South Africa is rated as one of the countries with very high lightning activity. In addition, we are also exposed to a high rate of switching transients (commonly known as surges) exacerbated by an unstable power supply grid.
Therefore, we are exposed to a heightened risk of equipment damage in both industrial and domestic environments.
The Lightning Flash Density map (https://shorturl.at/L55VJ) provides a clear picture of the annual lightning activity in South Africa, emphasising the need for proactive measures to protect our equipment.
Equipment protection
Lightning transients
Devices that protect equipment against lightning transients are classified as Type I devices. These devices typically can handle energy of up to 100kA.
Switching transients
Switching transients are more frequent and have a higher voltage intensity, but have a short duration. These transients can be generated in a number of ways, as indicated below.
• Contactors.
• Collapsing inductive loads.
• Power grid switching.
• Power grid failure.
• Component failures.
• Human error.
• Compressors.
• DC drives.
• Motors.
• Electrostatic discharge.
• N.E.M.P. (Nuclear Electro Magnetic Pulse).
• Improper grounding techniques.
The most common switching transient is loadshedding and power failures on the national grid. These cause major problems in the home, business, and industrial environments.
Type 2 devices
Devices that protect equipment against switching transients are normally classified as Type 2 devices. These devices typically can handle energy of varying currents
Type 3 devices: For sensitive equipment
Type 3 devices for the protection of sensitive devices are normally positioned as close as possible to the units requiring protection. These devices can typically handle switching transients of up to 20kA. They are typically used for mains, signal, and data protection.
What to protect?
When considering a lightning and switching protection solution, all wires used for the transmission of mains voltage, measurement and control technology, information technology, telecommunications, and transceiver applications must be considered. Should any of the total protection solutions be omitted, transients will find an unprotected gateway and damage or destroy equipment.
The only transmission lines (increasingly used for data and telecommunication transmission) that are impervious to lightning are fibre optic cables.
Earthing
Lightning and surge protection devices rely on an effective earth to divert excess energy away from protected equipment. It is important to note that all earth points must be bonded together and, in turn, bonded back to the main earth. A poor earthing system means poor or no protection.
No earthing system means no protection.
Find out more at www.drensky.co.za
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