Sparks Electrical News January 2015

14 earthing, lightning and surge protection

Lightning safety for shelters

EVERY year, lightning strikes result in property damage and sometimes the death of people and animals. Severe lightning injuries and fatali- ties are reported annually from all over the world, especially on golf courses, making shelters vital to protect golf- ers from the effects of lightning. The points below are not limited to shelters on golf courses, but are equally ap- plicable to hiking shelters, and other exposed areas. These shelters must not only protect from storms and rain, but also from the effects of a lightning strike. There is no question that shelters must be equipped with a lightning protection system, as golf course operators have a high duty of care towards their mem- bers and golfers. These shelters should not be located in exposed locations; for example, on hilltops, at the edge of woodland, or under single trees. Shelters are only lightning-proof if: • They are equipped with adequate lightning protection. • Conductive systems, such as electri- cal cables, are included in the equi- potential bonding; and • Suitable measures for preventing touch voltages have been taken. Lightning protection Frequently, a lightning protection system is simply a lightning rod. The function of a lightning rod is to inter- cept lightning and to safely conduct it to the ground to prevent dangerous sparking, thus protecting the structure from fire andmechanical destruction.

Generally, the lightning protection systemof a shelter consists of a rooftop air-termination system (air-termination conductor and/or rod), wall-mounted down conductor (down-conductor wire) and earth-termination system, commonly called earth rods. The formation of a high lightning voltage in the ground, also referred to as potential gradient area, also presents a risk to persons in the shelter. This voltage may be applied to the feet of a person standing on the ground. It is therefore also called step voltage. Moreover, persons must maintain an adequate safety distance to the light- ning rod to prevent dangerous touch voltages. Effective lightning protectionmeas- ures that protect golfers and hikers from the effects of a lightning strike can be implemented in shelters with a relatively low effort. Apart from techni- cal measures, it is equally important to knowwhat to do during thunder- storms. In the event of an impending thunderstorm, seek shelter immedi- ately and stay there until the thunder or lightning has ended. The additional considerations are based on commonly used wood shelters. Prevention of touch voltages To prevent dangerous high touch volt- ages, an adequate safety distance must be maintained between the lightning rod and the persons in the shelter. In a shelter of about 3 x 3 m, with an eaves height also of 3 m, a safety distance of at least 15 cm is required.

integration of a finely meshed metal grid; for example a reinforced steel mat, laid in concrete or a mesh earth electrode, with a mesh size smaller than1 x 1m, laiddirectly in theground below the shelter floor. To ensure a long service life of this metal grid, it is advisable to use 10 mm round con- ductors made of V4A stainless steel. These round conductors should be installed 0.1 mbelow the ground surface at intervals of 1 x 1 m andmust be connected with adequate clamps on all cross points and down conductors. Conclusion In general, persons must stay in shelters for about 30 minutes after they hear the last rumble of thunder. Only then is the thunder cell far enough away. Shelters on golf courses or hiking trails require both a lightning rod and adequate measures to reduce the risk of impermis- sibly high touch and step voltages. As described above, these measures can be implemented by simple means. Enquiries: +27 11 704 1487

near the wall construction, to ensure maximumwall thickness. Another possibility tomaintain the safety distance required to protect shelters in case of a lightning strike is to use highly insulating lightning rods. This is essential for shelters that are smaller than those described above. Prevention of step voltages Dangerous high step voltages, as a result of strikes into the lightning rod of a shelter or nearby lightning strikes, must be prevented. To this end, there are two options: 1. Prevention of dangerous step volt- ages by insulating the ground. This means that the floor must be made of a 5 cm asphalt layer. As an alterna- tive, a wooden floor can be used, if it maintains a sufficient distance from the ground to ensure adequate ven- tilation and that the wooden floor remains dry. 2. Prevention of step voltages by means of potential control. Another method of insulating the floor involves the

If the shelter has a minimumheight of about 3 m, the safety distance to the rooftop lightning rod (air-termination conductor or rod) is already main- tained. However, it is more difficult to keep an adequate distance to the outer walls. Therefore the wall/wall construction where the lightning rod (down-conductor wire) is conducted to the groundmust have an adequate wall thickness. To connect the lightning rod with the ground, earth rods (metal rods of a defined lengthmade of material appropriate to the local conditions) are commonly used. On each down conductor, the earth rods are vertically buried in the ground at a depth of about 6 to 9 m, depending on the type of ground. Log-structured shelters usually have this wall thickness. However, the situation is different when it comes to sheds with thin wooden walls. In this case, the down conductors must be installed directly at the outer edges,

Though old acquaintance be forgot … Mark Palmer, Western Cape Electrical Inspection Authority (WCAEIA)

enforcement when it comes to errant Registered Persons and electrical contractors. I amhopeful that, with support from the electrical contracting environment, these persons may not need to face these enforcement measures. From the legitimate contractors’perspec- tive, however, I am also hopeful that Registered Persons will support the active regulating of this industry. More importantly, I hope that Registered Person will contact me to discuss re-alignment training, which promotes a better understanding of the law as well as the correct interpretation and application of relevant standards. Enquiries: mark@geia.co.za

AS we begin a new year, I amoptimistic (for the first time in a long time) about the future of the electrical industry in this country. I believe that in 2015 the effective policing of electrical installa- tions that was originally envisaged by the legisla- tors – and which I actively upheld inmy previous activities as an approved inspection authority (AIA) – will be actively enforced and bring about a cleaner, safer industry. Over the past fewweeks, I have had some fruit- ful discussions with the Department of Labour and other industry role players and I am encour- aged that my repeated calls for the contracting industry, in particular, to work with policing agen- cies will no longer be falling on deaf ears. For a long time now, I have appealed to the Department of Labour to send a clear message to electrical contractors that there is, firstly, a mini- mum safety standard to which existing electrical installations must comply; and, secondly, that there is an absolute standard for new, altered or temporary installations. This is now of critical importance as it has become increasingly appar- ent that the electrical industry has continued to fall into decline insofar as compliance with SANS 10142-1 is concerned. This decline has been exac- erbated by the pressure exerted by uninformed consumers who look for the best price – and often find that the cheapest price comes from the less than scrupulous contracting environment. Fair play contractors As long as we take effective policing out of play, registered‘fair play contractors’will continue to suffer the economic consequences of this indus- try’s declining standards; and consumers (albeit that many of them are the instigators here) will continue to be on the receiving end of illegal and often dangerous electrical installations. I believe that the major contributing factor to the decline in standards – especially where

detail in future columns but, in the meantime, I advise Registered Persons to apply their minds to what would be determined as the actions of a “reasonable man”when applying general safety principles to electrical installations. As I return to the‘fray’, I hope that my endeav- ours in the AIA environment over the last 15 years or so will bear some fruit – especially with regards to Registered Persons. It has been very clear that, due to a lack of ongoing relevant training, many Registered Persons have lost touch with SANS 10142-1 and need to be re-acquainted with this standard. The Department of Labour has given its com- mitment that in 2015 it will be more stringent with

BLITZDUCTOR SP is a pluggable, multipole, universal surge arrester for use as a terminal block system inmeasuring and control circuits, bus, alarm and telecommunication systems. The surge arresters combine a permanently high impulse current discharge capacity with an extremely low voltage protection level for reliable protection of terminal equipment against light- ning effects and surges resulting from switching operations. To ensure safe operation, the arrester provides protection against vibration effects and shock loads up to a 30-fold acceleration of gravity. The function optimised design of the arrester ensures both quick and easy replacement of SPDmodules which house all relevant protection elements. Up to four lines can be connected on two levels mak- ing the arresters especially suitable for terminal block systems as lines of a pair belonging to each Certificates of Compliance are issued for existing installations – is that the principle of“reasonably safe”as referenced in the Electrical Installation Regulations is not fully understood. Many contractors do not grasp the fundamental principle that the Electrical Installation Regula- tions are subordinate to the Occupational Health and Safety Act of 1993 (the Act) where this exact terminology is not used. The principle of“rea- sonableness”is more clearly defined in the Act under the definition of that which is“reasonably practicable”. This concept is – and always has been – used in applying the“reasonable man”test when matters are decided in court. I will discuss the“reasonable man”test inmore

Pluggable DIN rail mounted surge arresters

other are connected on top of one another, over a width of 12 mm. The protectionmodules feature a fail-safe function. If an SPD is de- stroyed by means of a lightning or overvoltage incident exceeding the device specification, this generally causes a short circuit or an interrup- tion of the signal line. In both cases further over-voltages are inter- rupted and short-circuited. Thus, the overvoltage cannot damage the

systembeing protected. The signal on the line is also interrupted and the system fails. By simply removing the protectionmodule, the make- before-break switch contact in the BXT base part ensures no interruption of the signal transmission and the BSP type base interrupts the signal when it is removed. In both cases, after a new protec-

tionmodule has been plugged in, surge protection is restored again. A wide range of accessories, for example for la- belling, earthing of unused lines or easy testing of lines, completes the product range andmakes the Blitzductor SP arrester particularly user-friendly. Enquiries: +27 11 792 1303

sparks

january 2015

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