Sparks Electrical News March 2021

CONTRACTORS’ CORNER

6

WORKING KNOWLEDGE WITH TERRY MACKENZIE HOY

E lectric fences are everywhere. They are used for security, for stock control, for game fences… they are very effective. I was in Kenya, next to Lake Naivasha, and we were out on a jetty admiring the sunset. After a time, we heard somebody calling us. It was a park ranger. He shouted that we had to come back to the shore. We did and asked why. He told us that hippos were coming out of the lake and might attack us. Huh? So, we walked towards a shore side restaurant. On the way there was a low single strand electric fence, no more than half a metre high. We asked what it was for. “To keep the hippos away.” We laughed. At the restaurant we sat at a table on the outside deck and ordered drinks. It soon became dark, and looking towards the lake we saw a shape of some- thing on the shore. A sort of black shape about the size of a shipping container, only not as high. Then it sprang into focus. It was a hippo. A huge hippo. And yes… it did not walk beyond the line of the small elec- tric fence. Electric fences consist of the following components: a battery, a fence energizer, insulators, fence posts, HT cable and a fencing conductor. The battery keeps the fence energized when the power is off and is used for storage if the fence is operated from a solar cell. The HT cable connects the energizer to the fencing con- ductor. The fencing conductor can be wire (normally stainless steel or galvanized wire) or nylon cord into which has been woven a thin metallic conductor. This is quite a handy idea since you can join two cords by tying them together. If you want to camouflage the cord you can spray it various camo colours (grey and white work well). Energizers apply a high voltage to the fence, normally as a series of pulses. The installation as a whole is governed by various SANS codes of practice which limit the power and Electric fences. And hippos…

Helping the South African power grid brave thunderstorms

voltage that can be delivered to the fence so that people or animals are repelled by the fence and not electrocuted. It is worth noting that connecting the 220 V supply from the local power supply to a fence will result in prosecution on serious charges if a per- son is injured or even just shocked by it. The kit for a simple electric fence (say 50 m long) will cost about R10 000 including the battery. A fence installed will be double this. It is possible to make your own electric fence (but before I continue, all that follows is entirely at the risk of the person who undertakes such a pro- ject). First, the battery. Any battery will do. A golf cart bat- tery rated at 12 V will work fine. It need be rated at no more than 10 amp hour. It should be supplied with a charger which connects to the mains or a solar pow- er charger with a regulator, both rated at 30 W. You can make the energizer as follows: Obtain a motor car ignition coil from a scrap yard and a 12 V interval repeating timer from a parts shop (such as Electro- mechanica). Wire up the timer so it switches the bat- tery to the coil at about a four second interval with an ‘on time’ of about 1 second. You can use car engine HT ignition cable to connect to the fence conductor. You can make the fence conductor by wrapping stain- less steel wire around a nylon cord. Insulators can be made from any spare plastic – they don’t have to have all the bumps and fins of the commercial insula- tors, however, I recommend you buy these, it’s much less of a hassle. Unfortunately, electric fence installations are very ugly. The current installations seem to scream, “I’m an electric fence!” which is perhaps comforting to some people who need a feeling of security. To many others, the electric fences are ugly and lend a drab, industrialised look to what would otherwise be beau- tiful. A pity.

S outh Africa is the leading services destination, regional manufacturing hub and the most indus- trialised country in Africa. This makes it imperative to be supported by access to reliable power. To maintain availability and reliability of power supply across the country’s power network of more than 31 000 km requires consistent efforts by utilities and the use of innovative solutions. Cli- mate and geography can pose crucial challenges in such situations. Experts predict an increase in the number and severity of thunderstorms in South Africa due to climate change and global warming. Also, the landscape of South Africa is dotted with moun- tains and high plateaus. Transmission line towers installed in such terrain and height have higher chances of being struck by lightning, causing failure of critical equipment in the power network and leading to a blackout. Experts predict an increase in the number and severity of thunder- storms in South Africa due to climate change and global warming. To protect South Africa’s power network from such risks, an innovative solution can now be applied – Hitachi ABB Power Grids line surge arrester (LSA) Pexlink. Surge arresters are the primary protection device for critical equipment in the electrical net- work from over-voltages caused by switching operations or natural atmospheric events. They

protect the equipment from serious damage that can lead to costly downtime, expensive equipment failure and potentially harm per- sonnel. For utilities, this translates into pro- tection of key equipment like transformers and improved transmission line availability. The advantage of the PEXLINK solution to the utility is to improve the outage rate of the transmission line by installing LSAs on selected towers along the transmission line. The selection of towers for installation of the LSAs is done through simulation stud- ies to achieve optimal performance of the line LSAs. In case of a back flashover, part of the lightning current in the affected tower is shunted through the LSA(s). The LSAs in the towers in the immediate vicinity then act as the next layers of protection, shunting the current from the phase to the ground. These multiple layers of protection enable a con- stant, uninterrupted power supply from the utility to the consumer. Pexlink also eliminates the need for in- vestment in additional infrastructure to in- crease the reliability of the grid, like instal- lation of redundant transmission lines. In South Africa, this means the conservation of the ecology and biodiversity. The possibility to monitor surge arrest- ers makes predictive maintenance of surge arresters possible, as well as analysis of transmission line events. Hitachi ABB Power Grids Excount-II includes these monitoring features while ensuring safe operation of the grid. The Excount-II is a unique monitoring system that provides the utility with safe and effective monitoring of LSAs using remote reading for maximum personnel safety. With these solutions, South Africa’s transmission system is made more ro- bust against lightning-induced blackouts, thereby enabling a constant reliable sup- ply of power to consumers from bulk and distributed renewable energy sources, enabling consumers across the region to benefit from sustainable energy.

ing electromagnetic radiation. That includes biological effects, so as to develop medical X-ray devices, airport X-rays, medical MRI scanners, and anything that a scientist could find. Then it was all repeated, again and again. Meantime, other applications were developed and the first cellphone came about in 1983. But it was then called a car phone and was about the size of a modern laptop, but about 10 times as thick. After that first generation of phones, which worked with ‘spacial cells,’ later generations became smaller and better. There was a second generation, or 2G, followed by 3G, as even newer ideas occurred to the developers. South Africa’s first cellphone small enough to be carried clipped to one’s belt came on the scene just before the dawn of the 21 st century. But they were aimed at senior businesspeople and the wealthy elite. Nobody could imagine then that in due course schoolchildren and the piz- za delivery man would own cell phones, but now South Africa has one of the world’s highest cell phone penetration figures. The rapid world demand for this great idea spurred on the developers. They figured out how to send text mes- sages, with South Africa being one of the world’s first to do this. Then they found out how to send pictures, then small video clips. This meant that developers had to come up with a new generation of phones, which could send messages, then images, so they created a 3rd-generation, 3G, then 4G. The target was to send even more data and longer video. This target was 5G, but an interim step was called LTE (Long Term Evolution), or ‘trying to achieve the 5G target’. What is 5G? The latest generation of what a phone can do is 5G. A 5G system is going to be about a 10-fold improvement on the 4G system. So, what does this mean? The three big differences are; improved speed, bandwidth and latency. The ‘latency’ is the speed of your phone’s response to a signal. This means that in a video game you can shoot down space invaders faster be- cause the reaction time between your phone and the system is faster. Oh great! But there are other implications, like ordering a pizza to be delivered to your house by drone, which lands in your backyard next to your garden chair. The improved 5G system will allow for the faster reaction time and high data flow rate required to control the drone, and for the drone to use GPS to navigate and land accurately. To achieve this, the 5G will need many more signal anten- nae. The simple physics reason is that the higher frequencies required for the high data transmission do not travel very far, so one needs more antennae to cover any given area. But the antennae will be much smaller than before and can fit on a lamp post, rather than needing a large tower. More antennas also allow for more accurate positioning, like guiding you to the front door of a restaurant. However, to achieve the higher data transmission WHAT DOES 5G MEAN FOR OUR LIVES (AND ELECTRICAL CONTRACTORS)?

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and also the positional accuracy, it is necessary to use higher frequencies. But higher frequencies do not penetrate very far into anything, so you need more antennae spread around, but at relatively low power. The term ‘high frequency’ can sound scary and some people have taken fright. There have been accusations that the new high frequencies could cause cancer, but they are so low powered that you cannot get more than about 1% of the dose limit that is classified as a ‘safe’ dose by the International Agency for Research on Cancer (IARC) a division of the WHO. By the way, IARC clas- sifies coffee and pickles as potential carcinogens in the same category as 5G electromagnetic radiation. 5G and electricity For all the benefits that 5G is expected to bring, its impact on smart cities, smart technologies, and even just its deployment will offer electrical contractors a lot of job opportunities. It will not only improve the efficiency of contractors who increasingly rely on mobile devices for productivity, but will also provide a great influx of new work to do in installing new cells and maintaining them. From improved lighting performance to more responsive building operations, 5G should introduce cutting-edge capabilities in the smart tech world. One of the main reasons for this? Greater sensor density – one of the most critical aspects of a smarter future. While 4G towers will remain, 5G is going to rely mainly on ‘smart cells.’ So how are we going to really maximise the potential of 5G? These small cells may need to be installed by the hundreds of thousands. By raising the number of sensors and transmitters, smart cities will have better functionality, better data-gathering capabilities, and a more powerful network overall. Back in 2016, a survey found that 51% of electricians with at least 10 years of experience preferred working on high-tech installations. This was up from just 24% in 2015. Working on more complex systems doesn’t just present chal- lenges that allow electricians to improve their craft, it also invites collabora- tion. On a commercial job site implementing a high-tech system, experienced electricians can mentor young electricians and apprentices, lessening the skills gap and even bringing new ideas to the forefront. Today, electricians who install these high-tech systems have to be almost as knowledgeable as the engineers who design them. The arrival and full implementation of 5G is new. But rest assured, it will make our world better, our lives better and for the electrical contractor, offer further opportunities for work.

Sources: Dr Kelvin Kemm, www.bbrief.co.za; www.ecmag.com; www.blog.cityelectricsupply.com

Enquiries: www.hitachiabb-powergrids.com.

SPARKS ELECTRICAL NEWS

MARCH 2021