Lightning Truths And Myths - Explained

                                                                                                                                                                                                                                             

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Fact 1

Telkom Lines Are made from copper.

Fact 2

Telkom Lines will be struck by Lightning

Fact 3

Telkom Lines crisscross our country like Veins on your body

Fact 4

It does not need to Rain for lightning to strike.

Fact 5

It does not need to be cloudy above you for your Telkom lines to be struck by lightning.

Fact 5

Telkom lines as far as 60km away from you can carry the overvoltage to your PABX/Modem/Fax and damage it.

Fact 6

Lightning protection known as KP10 will not protect you from a low voltage such as 300volt on the Telkom line but this voltage can and will damage your PABX/Modem/Fax.

Fact 7

Damage to your PABX/Modem/Fax may not be evident immediately but can manifest itself even after 2 to three months, because components damaged may still work, but will fail eventually.

Fact 8

Lightning Protection will only minimise or lessen the damage done by a lightning strike.

 

Fiction

You are protected against Lightning Damage because you have lightning protection Installed.

 

Lightning - can you afford to ignore it?

Today, computers and computer-based equipment are used extensively in virtually every sector of industry and commerce - as well as hospitals, government facilities, laboratories and banking.

Whether a company operates a local area network, automated factory equipment, a sophisticated building security system, or even a small telephone exchange, it depends totally on that system to operate efficiently.

However, many organisations ignore the single biggest threat to their systems - voltage surges caused by lightning and electrical switching events.

Main power supplies and data communications lines are highly susceptible to surge voltages and the result is usually a total systems failure.

Apart from the enormous cost involved in replacing damaged equipment, consider other expenses that are difficult to quantify: severe disruption to your operations - data loss, downtime, loss of fax machine and telephone, inconvenience to your staff and your customers. But the situation can be avoided.

What happens

Lightning activity near to a building can cause voltage surges (transient overvoltage). These brief but significant increases in voltage on mains power supplies or data communication lines can be conducted into the electronic circuitry of computers and other sensitive electronic equipment. This results in: data loss, loss of fax and phone, system disruption, physical damage to equipment (either immediate or later through component degradation) and costly downtime. Electrical switching events can cause the same problems although chiefly affecting mains power supply.

Is existing protection not adequate?

A conventional lightning protection system will protect only the building structure, not its electronic contents. Equally, uninterruptible power supplies alone cannot protect a computer system against the large voltage surges caused by the secondary effects of lightning. These can be up to 6000 V (3000 A). Indeed, UPSs themselves need protecting from the effects of voltage surges.

Impact assessment of a lightning strike to a business site

http://www.engnet.co.za/tips/electrical/lightning/Ele_Lightning_1.jpe

An exercise seldom undertaken by the management of small and large business alike in Southern Africa is the impact assessment of a lightning strike to the business premises. The cost implications of down-sizing, outsourcing, franchising, brand-building, employee motivation and globalisation on the internet top the agenda at the Monday morning management meeting. The negative impact of equipment theft, warehouse fires, bad debts and other potential business-damaging events are well understood and insured against. With so many important issues to address, it is not surprising that the almost obscure event of a direct lightning strike to your business premises is largely ignored...until it happens, that is! The truth of the matter is that to a business, the damage that a lightning strike is able to inflict could be crippling in a multitude of unforeseen ways. The good news is that it is largely preventable. This article will outline the importance of conducting a simple impact assessment and investigate methods of preventing damage to the assets vital to your business.

Like any good business decision, the first thing that is necessary is to identify the risk and put a well thought out plan into place to achieve the desired results.

This could be done using the following steps:

  • Quantify the risk of a lightning strike to your business premises
  • Identify vital equipment which could be damaged in the event of such a strike
  • Accurately estimate the impact in terms of both cost and image that downtime due to a lightning strike could have on your business
  • Develop and implement a strategy to limit the impact of such a strike
  • Schedule a future reassessment to ensure that your strategy keeps pace with the growth of your company and maintenance is not neglected

We shall now look at how each step of the impact assessment is performed.

 

Quantifying the risk to your building

 

Fortunately, a fair amount of academic research has been undertaken in this field so that it becomes possible to put a number to your likelihood of being the victim of lightning damage. Lightning damage may occur either as a result of a direct lightning strike to the building or, more subtly and more commonly, as a result of the induced effects of a lightning strike some distance away. Lightning which strikes kilometres away may cause damaging electrical surges which travel long distances on power and telecommunications lines. Although a proper detailed risk analysis* is outside of the scope of this article, there are some simple calculations which may be performed and basic reasoning which may be employed. Firstly, look up the lightning ground-flash density (LGD) of your area. Lightning ground flash density is simply a number which represents the average number of direct lightning strikes to a square kilometre of your area in one year. The LGD for Johannesburg is approximately 7 strikes/square km/year while Durban and Cape Town drop down to approximately 3 and 1 strikes/square km/year respectively, indicating a significantly lower risk in these two areas. The next step is to investigate the geography of your area and use the rules outlined in the standards (SABS IEC 91024-1) to work out what percentage of those strikes to your area are likely to terminate on your building and what percentage are likely to cause induced surges which may damage equipment connected to power or telecommunications cables in your office. Should the standards be too technical or if you simply don’t have the time or inclination, earthing and lightning protection companies will perform the service at relatively inexpensive rates or even free of charge as it leads to further business for them. Quantifying the risk will allow you to make an educated financial decision about the lightning protection measures which need to be employed in your business.

 

Adding up the cost of lightning damage

 

Once the lightning risk has been determined, the next step is to calculate the costs should lightning damage occur. These costs may be split into two types, direct and indirect costs:

Direct costs are incurred when lightning damages equipment, buildings and causes lost productivity. Common equipment fatalities in the business environment include:

  • computers and peripheral equipment such as scanners and printers
  • modems
  • network equipment
  • fax machines
  • alarm systems
  • electric fence energisers
  • CCTV cameras and equipment
  • electric gate motors
  • intercom systems
  • telephones
  • PABX’s
  • Specialised electronic equipment unique to your type of business

Additional direct costs include:

  • Repairs to damaged wiring and building superstructure
  • Lost productivity resulting in lost income

A commonly heard response during this exercise is "My insurance will pay so it is of no real concern to me." This is only true in some cases as most insurers now state in their contract that they will only cover the eventuality of lightning damage provided that adequate lightning protection systems were in place. Lost productivity is also a direct cost which few businesses are covered for. The figure you have arrived at for your business represents an estimate of the immediate cost which you will probably incur every X years where X is the result of your lightning risk analysis outlined above. Not so easy to quantify, however, are the indirect costs.

Indirect costs represent losses to the business in ways which are not so easy to put a figure to. Some of these may include:

  • Downtime of the phone and PABX system - most businesses rely heavily on their incoming phone lines as a source of new business and client contact. Phone downtime loses customers and damages service reputations.
  • Downtime of computer systems and networks - once again, if your emails go unanswered, your website is unavailable and your staff are sitting helplessly behind blank screens, customers and reputations are lost
  • Lost data - a massive hidden cost to any company operating computers (who isn’t?). Not only is the information lost but if no adequate back-up strategy is in place, months or even years of work may be lost as well.
  • Lost productivity may also be classed as an indirect cost as late deliveries also ruin reputations. If you operate expensive imported machines where spares and repair expertise are not freely available, your company should be especially wary of this point
  • Breach of office security - When the electric fence, CCTV cameras, electric gates and alarm system are out of action, your premises are exposed to a high security risk
  • Health - although rare when compared to the frequent damage of sensitive electronics, lightning strikes sometimes claim human victims which is unforgivable when it is easily preventable.

 

Developing and implementing a lightning protection strategy

 

If the preceding steps have been investigated, you should have a decent idea of the impact of the lightning threat on your business. The next step is to analyse what you know and put a simple but effective strategy into place in order to deal with the threat. Such a strategy is proposed below:

  • Get a reputable and qualified consultant to check the earthing system of your premises. The earthing system is vital to both general electrical safety and the correct operation of lightning surge protectors. Many companies will do this testing free of charge in exchange for the contract to supply earthing or surge protection equipment.
  • Install decent surge protection on all of your valuable equipment. Something to note about surge protection devices is that, like any product, you get the poor quality, badly designed and the decent products. Finding out which is which may be difficult but asking for properly tested, SABS approved equipment is a good start. Another good strategy is to ask for advice from the technical department of a number of companies and compare the different answers. You could also contact the local university, the SABS or the CSIR or equivalent bodies and ask the advice of the electrical engineering departments. This technique will help you to isolate the competent companies. In general, the cost of installing decent surge protection will be a fraction of the cost of the equipment being protected and should be viewed as a vital form of physical insurance. Remember, most insurance companies will not cover equipment damaged by a lightning strike unless lightning protection devices are installed.
  • If the risk analysis indicates that the expected number of direct lightning strikes is high due to your geographical situation, you should also consider installing an external lightning protection system if one is not already installed. This system comprises a series of interconnected conductors running from your buildings roof, down the walls and into an earthing system. An external system of this type is designed to divert the lightning currents safely to earth on the outside of the building and prevents damage to the superstructure, dangerous side-flashes and touch-potentials inside the building and minimises the risk of damage to equipment. An external lightning protection system is not a substitute for surge protection devices but is rather an additional and vital level of protection which complements the operation of the surge protection and decreases the overall risk of lightning damage to your building as the path of the lightning current is controlled and diverted directly to earth.
  • Finally, a maintenance strategy should be put into place to check that the earthing system and surge protection devices remain in good working order. Earthing systems degrade with time due to corrosion, theft (they comprise mostly copper!) and accidental disconnection during non-related electrical work. They should be checked on a regular basis. Surge protection devices degrade with use like any other physical product and should be maintained and replaced accordingly. Some products have failure indicators built in which visibly indicate failure. Maintenance strategy should include the checking of all surge protection devices after big storms, checking the devices and the earthing system after the summer lightning season and possibly the replacement of all surge protection every 1-3 years regardless of visible condition.

 

Conclusions

 

The negative effects of direct and indirect lightning strikes to a business can be minimised. In fact a lightning strike is one of the only forms of natural disaster in which no damage to person or property is necessary, provided the correct technology and strategy are employed beforehand. At the end of the day, the risk of damage must be weighed up against the cost of installing and maintaining a lightning protection system and each business requires a unique strategy to combat this threat.

 

 

 

Common mistakes

The most common mistake made in lightning and surge protection is to believe that if a building has external protection or a mast, the equipment inside the building is safe. This is not true. The external lightning protection is only there to protect the building and to provide a convenient path for the lightning current to be dissipated into the earth.

It has been well documented that direct lightning strikes are responsible for a small percentage of damage to electronic equipment. In excess of 90% of the damage occurs due to indirect effects.

When lightning hits a tree or structure, a powerful electromagnetic force is set up due to the fast rise time of the flow of lightning current. This electromagnetic force than couples into any inductive loop that may be in the vicinity of the strike. A CCTV system in a building that is interconnected with coaxial cable for video signal and a power cable from a power supply constitutes an inductive loop. When lightning energy is present, this loop will absorb energy from the strike and try to find a path to earth. If no protection devices are present that provide a path for the lightning energy to bypass the electronic equipment, damage could occur.

THE FACTS ARE :

  • It is a fact that the Highveld region of South Africa and Lesotho have amongst the highest lightning strikes per square km per annum in the world.
  • On average every square km of South African Highveld and Natal receives 7 direct lightning strikes per annum.
  • The facts are a direct or indirect lightning strike within a 1,5km radius of your home or office can generate as much as 120 million volts and up to 180 000 Amps, sending lethal surges ripping through power cables and telephone lines. The core temperature of a lightning strike is as high as 20 000 deg C or five times as hot as the surface of the sun.
  • Statistics prove that as much as 80% of problems on electronic equipment are associated, directly or indirectly, with lightning and overvoltage surges.

samap

 

FREQUENTLY ASKED QUESTIONS

By installing a mast or external lightning protection on my building will it be sufficient to prevent damage to equipment inside my building?

No, as the electromagnetic effects and induction will still cause damage to equipment within the building. In actual fact, if you install external lightning protection, you will actually require lightning current arresters and surge arresters to be able to withstand the induced energy. Lightning striking up to 1km away can cause damage to sensitive electrical and electronic equipment.

How often can I expect a direct strike to my house?

An average 200m2 house in Gauteng, with a lightning flash density of 5 strikes per km, can expect to be struck less than once in 250 years. The same house can expect a surge to enter via the power and telephone cables at least 5 times a year thus power and telephone line protection are strongly recommended.

By installing surge arresters in my electrical distribution board will I never have damage again?

By installing surge arresters in your electrical distribution board you are dramatically reducing your risk of suffering damage via the power only, but not eliminating the risk.

Will the surge arresters in my electrical distribution board be damaged by a direct strike?

Most probably as they are only designed to withstand induced surges of up to 40kA. A direct strike has far more energy which could destroy the surge arresters but they will still offer some protection. Due to the fact that your risk of a direct strike is so small you should worry about the regular induced surges.

If the supply voltage increases to 250 Volts, will the surge arresters protect my equipment?

No, as they are designed to protect against high energy, high voltage surges and not to operate as voltage regulators.

Once the surge arrester has disconnected can it be re-set?

No, it needs to be replaced.

If the electrical distribution board has a fault current rating of 15kA must I use 20kA surge arresters?

The kA rating of the surge arresters has nothing to do with the fault current rating of electrical distribution board. You can fit a 40kA surge arrester in a domestic board with a fault current rating of less than 5kA. In larger panels with high fault current ratings you must pre-fuse the surge arresters to co-ordinate and protect the surge arresters.

Does it help to fit 2 x surge arresters in parallel to increase the surge handling capabilities?

Not really, as the surge arresters will not conduct evenly and thus by installing 2 x 40kA surge arresters does not mean that you can handle a surge of 80kA. You may be lucky to handle a surge of 65kA.

What is the difference between a surge arrester marked 40kA (8/20) and 65kA (4/10)?

These 2 x units are actually the same but (4/10) is half the energy of (8/20) and thus the manufacturer can claim higher kA ratings. To overcome this problem all manufactures must publish their surge handling ability at (10/350) for lightning current arresters and (8/20) for surge arresters.

If I install lightning current arresters Class 1 will I get a better level of protection than using surge arresters Class 2?

No, if you install Class 1 then they must be used in conjunction with Class 2 surge arresters to offer complete protection.

If I install only plug-in type surge arresters such as the Copa SurgeGuard range will I be protected?

The Copa SurgeGuard range is typically a Class 3 arrester and in terms of SANS 10142-1:2003 they should be used in conjunction with Class 2 surge arresters installed in the electrical distribution board.

Must I unplug my computer or modem if there is lightning and I have a Copa SurgeGuard TeleFax protector installed?

No, the Copa SurgeGuard is designed to withstand induced surges and it also requires the electrical plug to be plugged in to supply the earth discharge path.

Lightning and surge protection philosophy - six point plan

http://securitysa.com/articles/Hi-Tech%20Security%20Solutions%20-%20Published%20by%20Technews/54HT39.jpg

1. Capture the lightning strike

To prevent damage to the building structure and roof-mounted equipment, an air termination network needs to be provided to capture the lightning strike at preferred points.

2. Conduct the strike to the ground safely

Downconductors, capable of carrying the lightning current, should be installed to conduct the lightning strike to ground without the possibility of flash over to extraneous metal work and electrical systems.

3. Low impedance earthing

Provision of low impedance earthing is of major importance to the efficiency of the lightning protection system. It is essential that a low impedance earth be provided to facilitate the dissipation of the lightning energy into the mass of earth as quickly as possible.

4. Eliminate earth loops and differentials

A structure may have several service earths installed that may comprise telephone, electricity supply, communications or special purpose earths. All these may be in addition to the lightning protection earths. When potential differences occur between any of the multiple earths, equipment damage is possible. By providing equipotential bonding to all earths, this problem can be eliminated.

5. Power line protection

If lightning strikes the power lines some distance from the structure, a surge will travel in both directions, including into the structure containing sensitive electronic equipment. This equipment can be protected by the installation of shunt connected surge diverters or inline surge reduction filters.

6. Telkom/Data line protection

Telephone, communications and signal cables entering a structure (overhead or underground) are subject to induced surges or direct strikes that can also damage the electronic equipment to which they are connected. The protection of such equipment by installing suitable protection devices should be considered.

Useful Info (Courtesy Of Surgetek)