What ACCORD stated about Lighting Protection System!!!
10.11 Lighting Protection
10.11.1 General
Lightning Protection shall be provided for in accordance with the following:
10.11.1.1 New building shall have protection against lightning depending on the probability of a stroke and acceptable risk levels. Steps shall be taken for an objective assessment of the risk and of the magnitude of the consequences of lightning strikes following BNBC Part 8, section 2.9. The marginal Risk Index shall be 40. Structures higher than 53 m (174 ft) require protection in all cases.
10.11.1.2 A complete lightning protection system shall consist of air termination network, down conductors and earth termination.
10.11.1.3 A lighting protection system shall be required for existing construction if the marginal Risk Index is 40 or greater and the structure is higher than 53 m (174 ft)
10.11.2 Air Termination Network
The air termination network is that part which is intended to intercept lightning discharges. It consists of vertical and horizontal conductors arranged to protect the required area. No part of the roof should be more than 9m (30 ft) from the nearest horizontal conductor except that an additional 0.3 m (1 ft) may be added for each 0.3m (1 ft) or part thereof by which the part to be protected is below the nearest conductor.
10.11.3 Down Conductor
10.11.3.1 The down conductor is the conductor which runs from the air termination to the earth termination. A building with a base area not exceeding 100 m2(1,076 ft2) shall be provided with one down conductor. For a large building there shall be one down conductor for the first 100m2(1,076 ft2) plus a further one for every 300m2 or part thereof in excess of the first 100 m2 (1,076 ft2). Alternatively, for a larger building one down conductor may be provided for every 30m (100 ft) of perimeter. The number chosen can be the smaller of the numbers given by these alternative methods of calculation.
10.11.3.2 The material used for lightning conductors must be aluminum or copper. The criterion for design is to keep the resistance from air termination to earth to a minimum.
10.11.4 Earth Termination
10.11.4.1 The earth termination is that part which discharges the current into the general mass of the earth. The total resistance of an electrode for a lightning protection system must not exceed 10 ohms.
10.11.4.2 The lightning protection system ground terminals shall be bonded to the building or structure grounding electrode system.
10.11.4.3 Recommended dimensions for various components of lightning arrester are given in Table 4.6. Larger conductors should however be used if the system is unlikely to receive regular inspection and maintenance.
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