Evaluation of lightning and earthing practice in Hong Kong

Pao Yue-kong Library Electronic Theses Database

Evaluation of lightning and earthing practice in Hong Kong

 

Author: Lau, Kim-man
Title: Evaluation of lightning and earthing practice in Hong Kong
Degree: M.Sc.
Year: 2001
Subject: Lightning -- Protection
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Building Services Engineering
Pages: 1 v. (various pagings) : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1597783
URI: http://theses.lib.polyu.edu.hk/handle/200/630
Abstract: The aim of this report is to emphasized the significance of lightning protection, earthing and bonding systems although they are relative small item in a building. A survey is conducted on different types of buildings to observe the local practices and common problems, hence, to suggest possible improvements and to encourage good practices on design, installation, inspection and maintenance to be applied in the future. Increasing utilization of the early streamer emission (ESE) together with coaxial cable of lightning protection design in Hong Kong has been noted. It offers a new concept on lightning protection and provides a more simple, cost effective and flexible system design than conventional design. But the increasing risk of side flash due to reduced number of down conductors in a high rise building should be considered. In addition, the use of a coaxial cable as the down conductor should be avoided because of possible insulation breakdown and side flashing at the top of the cable. Instead, the building reinforced steel bar is recommended. Common problems such as high earth resistance and separate "clean earth" requirement for telecommunication installation of building are discussed, and possible solutions are verified. Significant improvements on earth resistance are observed by using the building foundation pilling as the earth electrode or soil chemical treatment. Equipotential bonding between main earth termination, functional earth termination and lightning earth termination must be maintained to reduce the risk of equipment damage and life hazards. As extensive supplementary bonding is required according to the Codes of Practice. Practical testing is suggested to minimize the supplementary bonding. And the selection of the size of supplementary bonding conductor according to regulation is verified. Since there will not be immediately danger when lightning conductors or bonding conductors are being removed, testing and maintenance on these system are always ignored. Poor practices such as outstanding testing record, insufficient commissioning and lack of routine maintenance are found in most buildings. As a result, protection to occupants and property within these buildings is not ensured.

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