Sparks Electrical News September 2021

EARTHING, LIGHTNING AND SURGE PROTECTION

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The different types of lightning

strike travels in the air between them.

enced from high objects where the lightning flash travels from the ground object to the cloud. Dam- age does result from this discharge. This type of lightning makes up approximately 10% of strikes Beaded Lightning Is rather unusual in that beaded lightning persists for some seconds, and then appears to break up into a string of luminous fragments that gradually fade. Very rare. Ball Lightning A very unusual brush discharge reported as a lumi- nous spherical or pear shaped body with a blurred outline. It normally causes no harm. Very rare.

Cloud to Ground This is where lightning travels from the cloud to the ground. These strikes usually cause the most damage, the type we often call “forked” lightning. Usually multiple strikes occur along the same path. This type of lightning makes up approximately 80% of strikes. Cloud-to-Cloud An impressive display of flashes, accompanied by little rain or no thunder. 80% of all lightning is inter- or intra-cloud.

Bolts from the Blue One of the most dangerous types of cloud-to- ground lightning are bolts from the blue. A "Bolt from the Blue" is a cloud-to-ground lightning flash that typically: • Comes out of the back side of the cloud. • Travels a relatively large distance in clear air away from the storm cloud. • Then angles down and strikes the ground. These lightning flashes have been documented to travel more than 40 km away from the cloud. Intercloud The least common is the strike between the positive and negative charges within separate clouds when the

Intracloud Lightning Intra-cloud is the most common form of lightning. It appears as a flash within the cloud occurring between the positive and negative charges that are within the same thunder cloud. Due to it causing very little dan- ger or damage, not a lot of research has been carried out on it in comparison to cloud to ground. Triggered Lightning Lightning which has been triggered directly by human activity.

Ground to Cloud Not very common but may normally be experi-

Enquiries: www.lectrotech.co.za

Keeping telecommunications online with surge protection

Webb Industries, a division of Jasco Trading, is a leading supplier of imported and locally manufactured RF ancillary products in the tel- ecommunications and data networking industries. Webb offers turnkey telecommunications solutions for data network infrastructure, support- ing both copper and fibre networks, in-building coverage enhancement consisting of distributed antenna solutions, site specific installation kit services as well as a range of mast and tower offerings. Webb was established in 1973 as a mast and rigging company, and until 1976 specialised in self-supporting poles, guyed lattice and self-sup- porting structures. In 1983 Webb was acquired by Jasco and started co- operating with Jasco International, which was at that time involved in the military telecoms market. In 1985 Webb and Jasco International merged. The company has over forty years of experience in cable assembly practices and supplies low intermodulation cable and connector as- semblies to meet high operating specifications required in demanding communications applications. Webb also supplies various makes of lightning protection and grounding options to safeguard sophisticated communication equipment deployed in harsh environmental condi- tions, as well as world-class range of coaxial cables and connectors for low loss corrugated copper, low loss foil and braid, semi-rigid and stand- ard braided; and jumper cables compliant with IP68 specifications. A solid partnership – Webb and Dehn Webb partners with the world's leading data and telecommunications ancillary product vendors to deliver the best quality components and ensure that your network operates optimally. Partners include Com- ba, Eupen, Laird, Telegärtner, Times Microwave Systems and mWave amongst others. Lightning and surge protection is indispensable for protecting human lives, preventing fires and avoiding cost-intensive outages of networked systems. When it comes to protection, Dehn has been the partner of choice for the last five years for ac/dc surge and lightning protection

solutions as well as safety equipment. Supplied by Webb, DEHNvap modular prewired combined arresters protect the 230/400 V power supply of cell sites, can be universally used for TN-S and TT systems, and are specifically designed for mobile communication applications. When using combined arresters, energy coordination with system and equipment technology is an important criterion. For this reason, Dehn has extensively tested DEHNvap in its test laboratory to ensure its coordination with the integrated input cir- cuits of power supply units. The DEHNvap range includes: • DEHNvap CSP 1P 50 S FM: Prewired combined arrester, energy- coordinated with power supply systems for cell sites in new compact 2 standard DIN module design. • DEHNvap CSP 3P 100 S FM: Prewired combined arrester, energy- coordinated with power supply systems for cell sites in new compact 4 standard DIN module design. • DEHNvap CSP 1P 255 FM : Plug-in, prewired combined arrester, energy-coordinated with power supply systems for cell sites in 2 standard DIN module design. • DEHNvap CSP 3P 100 FM : Plug-in, prewired combined arrester, energy-coordinated with power supply systems for cell sites in 8 standard DIN module design. Webb is proud to be premiering its new brand image this November – Sparks Electrical News will bring the news to you first. The importance of surge protection in the lightning pro- tection arena In order to understand the need for surge protection, it is important to understand how lightning causes damage. The sources of lightning damage can be quite different, therefore different protection techniques may be required to protect different items. There are two areas of concern when evaluating a building or struc-

ture, namely the structure itself, and all incoming cables, meaning IT equip- ment as well as power. From this, the four sources of damage are derived, as per the following possibilities: • Having a lightning strike directly to the building. • A strike near the building. • A strike directly to an incoming line. • A strike near the incoming line. Nearby strikes cause surges: in striking neighbouring buildings, surrounding objects or areas next to incoming lines, the lightning current coming down generates a magnetic field, which is cast over the structure or lines. This mag- netic field generates an induced current on the incoming line, or on cables inside the structure. To prevent resulting damage to electrical equipment, surge protective devices (SPD) are recommended to reduce the induced ef- fects of lightning. To prevent burning or mechanical damage, lightning rods are installed, also known as external lightning protection. By installing external protection, users protect against structural damage, but this will not necessarily prevent electronic equipment from being dam- aged (for example TVs, Internet routers and appliances such as kettles, fridg- es, microwaves and so on). Therefore, in order to protect equipment, surge protective devices are needed as well. The calculation from the SANS 62305-2 standard to evaluate the risks are as follows: • The area to be considered for direct strikes is a radius around the structure, which is three times the height of the structure. • The area to be considered for surges is a radius of 500 metres around the structure, and can be up to two kilometres away in both directions for incoming lines. The risk of resultant surges therefore exceeds that of direct lightning strikes, meaning that the correct installation of surge protection devices is extreme- ly important. Other benefits of surge arresters include the minimising of switching surges coming from the grid. This is a relevant topic when seen against the background of recent load shedding from the South African grid.

Enquiries: +27 (0)11 719 0000

SPARKS ELECTRICAL NEWS

SEPTEMBER 2021