axiom engineering (416) 410-5967 - lightning protection system design

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Lightning Protection Systems

Types of Applications:

Lightning Warning Systems
Radio and Microwave Transmission Towers
Tank-Farms and Hazardous-Material Sites
Essential-Service Buildings (fire, police, ambulance)
Religious Buildings: Steeples and Spires
Office Buildings and Hotels
Computer and TeleCommunications Centres
Recreational Centres, Golf Courses, Sports Fields
Universities, Schools, and Playground Areas
Hospital and Military Installations
Warehouses and Hazardous-Material Factories
Residential Dwelling Units
Historic Structures

The complexity of lightning discharge phenomenon and the difficulties encountered in modeling its events make the field of lightning protection controversial. One fact that researches do agree on is that the frequency and intensity of lightning activity is increasing worldwide and we must provide ourselves with protection from its effects. Lightning theory, like nuclear physics and quantum mechanics, is founded on statistical probabilities based on empirical data collected through years of research. Fortunately, we're able to define a series of steps required for basic lightning protection that are common to most design concepts. These are:

1. Discharge Collection

A system of air terminals and intercepting conductors mounted on the roof edges and features collect the lightning strike along their conductive surfaces and concentrates the discharge along a common preferred path. When designing such collection systems, we examine the structural and cladding components of the building to determine if they can be used as collection points to reduce installation costs. At this stage of design, we can suggest minor revisions to proposed materials in order to allow their use as adequate intercepting surfaces.

2. Distribution and Conveyance of Discharge

A system of down conductors are connected to the air terminals and intercepting conductors to form a safe and electrically-continuous path for the lightning strike to be discharged to ground. These down conductors are installed in convenient paths down to grade. Like the discharge collection system, it may be possible to utilize the building's conductive structural elements to safely guide the lightning strike to ground. We examine the structural elements and their dimensional properties to minimize expenditures for your client. We also review the proposed path and locations of the down conductors for proximity to occupied spaces. A phenomenon known as side-flash or spark-over is a secondary effect that allows a discharge to jump from one conductive surface to another, causing collateral damage or personal injury and death. If we feel that there is a probability of this occuring, we can implement site-specific safety features to reduce the risk.

3. Dissipation of Discharge

The final step involved in lightning protection involves providing a system of grounding electrodes to guide the lightning strike from the down conductors away from the building and safely into Earth. It's also important to properly interconnect the lightning protection ground rods to the building's main and telecommunications ground system to eliminate the possibility of earth loops that can damage sensitive electronic equipment and electrical distribution systems. This is a very important aspect of the system and also the most variable due to the wide range of soil types - each having different electrical characteristics. Once we determine the typical nature of the soil at your proposed site, we have several grounding methods available. In some instances, it is necessary to use an earth enhancing compound to reduce the soil resistance around grounding electrodes. Loamy, shaley, and solid rock conditions each require different grounding methods for maximum effectiveness.

4. Building Services Protection

All incoming power and telecommunication lines entering the building must also be protected from voltage transients and surges that are capable of destroying distribution and computer equipment. The best way of accomplishing this is to install a cascaded protection system starting from the main service entry and proceeding to the distribution equipment and termination points. This includes telephone coaxial cabling and fibre optic installations. We'll help your client decide which system of Transient Voltage Surge Suppressors (TVSS) and Line Filters best suit his equipment and budget. See our Power Conditioning service description section for more information.

5. Lightning Warning System

The electro-magnetic nature of lightning allows us to specify electronic sensor arrays to create lightning warning systems that provide monitoring of the Lightning Hazard Level (LHL) with an adjustable range of 5-25km around the sensor array. The warning system can also be connected to alarm systems and horns to signal the possibilty of nearby lightning strikes. These systems are particularly suited for outdoor recreational and sporting activities, and around hazardous material handling yards, as well as military and fueling operations.

Some systems can be interfaced with computers to provide continuous recorded monitoring of impending storm conditions and events. A variety of configurations are available to suit your client's budget restrictions.

The lightning warning systems usually consist of a tripod sensor array mounted at roof level, with a Master Alarm Controller located in a secure room within the facility. Horns, buzzers, and indicator lights can be connected tothe system to provide remote warning of potential lightning hazards.

It's important to implement each of the first four steps to avoid potential hazards to personal safety and damage to equipment. As electronics have become miniaturized as a result of lower logic circuit voltage, they have become more sensitive to surges caused by lightning, heavy equipment use, static discharge, and switch-mode power supplies used in most computer equipment. If you're in doubt about how lightning protection may apply to your project, we can make recommendations and discuss site-specific protection techniques and equipment with you.

Click the menubar links to the left under "Services Contents" to obtain detailed information on each of the services we provide. If you'd like us to submit a Fee Proposal for your project, please go to the Fee Request Form.We look forward to working with you.

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