Transformers and Substations Handbook 2014

prevent hazardous sparking inside the building or structure. This is achieved by means of equipotential bonding or a safety distance between the components of the lightning protection system and other conductive elements inside the building or structure. Surge and lightning protection for electrical and electronic systems A lightning protection system, according to International Electro- technical Commission (IEC) 62305-3, protects persons and mate- rial assets of value in the buildings. It does not protect the elec- trical and electronic systems, but it is precisely such systems – in the form of building management, telecommunications, control and security systems – that are rapidly becoming common in all areas of residential and functional buildings. Whilst owners or operators place high demands on the permanent availability and reliability of these systems, few developers seem to appreciate the fact that they are critically susceptible to externally and inter- nally generated voltage transients and surges, especially those produced by lightning. Lightning up to a kilometre away can cause damage to sensitive electrical and electronic equipment. At these distances, the in- duced voltages can be as high as 200 V per metre of cable, which is more than enough to cause damage to equipment. Even equip- ment connected via cabling within a building can be damaged as a result of the high electromagnetic induction that occurs under lightning conditions. Lightning damage falls into two main categories; primary and secondary effects. Primary effects are those resulting from direct lightning strikes, which are a major cause of fire, instant destruction of property, electrocution injury and death. Even though it is one of the most common natural phenomena known to man, there has been no practical method developed to prevent lightning strikes or to avoid damage caused by a direct hit. The most prevalent technology for dealing with lightning is to divert the strike energy to a properly grounded lightning rod or cabling system. The external lightning protection on a building is only there to act as a preferential point of strike and offers a con- trolled discharge path to earth, thus preventing structural damage to the building. A common misconception is that if the building has external lightning protection, or if there is a high mast in the area, the equipment will not be damaged. It must be borne in mind that a single earth-termination system for all the various electrical To ensure uninterrupted supply, substations and overhead line networks must be maintained.

Transformers + Substations Handbook: 2014

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