The Electrical discharge that occurs between earth and air, is felt by thunder and a strong light.
As per statistics, every minute, more than 1,900 lightning flashes fall out over earth's surface. The basic principle for protection of an installation against the risk of lightning strikes is to prevent the disturbing energy from reaching sensitive equipment. Two protection systems are used to eliminate or limit overvoltages: they are known as the building protection system (for the outside of buildings) and the electrical installation protection system (for the inside of buildings). The role of the building protection system is to protect it against direct lightning strokes. When the lightning current flows in a conductor, if potential differences appear between it and the frames connected to earth that are located in the vicinity, the latter can cause destructive flashovers.
As a consequence, the building protection system does not protect the electrical installation: it is therefore compulsory to provide for an electrical installation protection system. 50% of the lightning current discharged by the building protection system rises back into the earthing networks of the electrical installation (see Fig. The procedure to protect the electrical and electronic systems of a building is as follows. Identify the electrical and electronic systems and their respective points of entry into the building.
Assess the risk of lightning strike according to the geographic location, type of power supply, lightning strike density, etc. Install an additional SPD in each subdistribution board located in the vicinity of sensitive equipment (see Fig.
Surge Protection Devices (SPD) are used for electric power supply networks, telephone networks, and communication and automatic control buses. The Surge Protection Device (SPD) is a component of the electrical installation protection system.This device is connected in parallel on the power supply circuit of the loads that it has to protect (see Fig. PrincipleSPD is designed to limit transient overvoltages of atmospheric origin and divert current waves to earth, so as to limit the amplitude of this overvoltage to a value that is not hazardous for the electrical installation and electric switchgear and controlgear.


The Type 1 SPD is recommended in the specific case of service-sector and industrial buildings, protected by a lightning protection system or a meshed cage.It protects electrical installations against direct lightning strokes. Very different devices, from both a technological and usage viewpoint, are designated by this term. Even though the odds are in your favor that your boat may never be hit by lightning, if it happens it can have devastating effects. The voltages involved in lightning are so high that even materials that would normally be considered non-conductive become conductors, including the human body.
It is generally accepted that this cone of protection extends 45 degrees, all around, from the tip of the metal protrusion. Besides the prevention methods against lightning, there are also methods to safeguard public and industrial places. They are used to protect special structures: rocket launching areas, military applications and protection of high-voltage overhead lines (see Fig. Installed in each electrical switchboard, it prevents the spread of overvoltages in the electrical installations and protects the loads.
This current must always be greater than the prospective short-circuit current at the point of installation. The voltages are so massive that if they start to travel through a boat's structure - say through its mast - then meet with high resistance (for instance, the hull skin) the current discharge, in its attempt to reach ground, may simply blow a hole in the non-conductive barrier. The principle of a Faraday's cage is to provide a surrounding, well-grounded, metal structure, in which all of parts are bonded together and carry the same electrical potential. This means that if the aluminum mast of the average sailing vessel is properly bonded to the vessel's other major metal masses and is given a direct, low-resistance conductive path to ground, the entire boat should fall within the protected zone. As soon as load cells pass over the low air resistance, the electrical discharge occurs and the loop is completed.
Moreover, the flow of current through the down-conductors generates induced overvoltages in the electrical installation.
There are also SPDs adaptable to power sockets, but these devices have a low discharge capacity.


If you are in a small boat and close to shore when a thunderstorm approaches, get in and off the water immediately. A marine electrician must tie in the engines, stoves, air conditioning compressors, railings, arches etc. If the vessel has a wooden or composite mast, a marine electrician can achieve the same effect by installing a 6 to 12 inch metal spike at the top and running a heavy conductor down the mast and as directly as possible to ground, usually through the engine and propeller shaft. This type of lightning protection system is used for highly exposed buildings housing very sensitive installations such as computer rooms. For your safety and the safety of others boating with you we have updated and are republishing this article on Lightning Protection. Reference should be made in detail to the standards for lightning protection as set forth by the American Boat and Yacht Council (ABYC) and the job should be performed by a licensed marine electrician. In other words, you need to provide an unobstructed way for the lightning to dissipate its energy to ground (the water surrounding you). Again, refer to the ABYC standards and have a professional marine electrician install your lightning protection.This is not a do-it-yourself project. The voltage protection level chosen must be below the overvoltage withstand capability of the loads.
The additional benefit of a lightning protection system is that it tends to bleed off any charge build-up in the general vicinity, possibly averting a lightning strike in the first place.
In the event of lightning strokes, the voltage across the terminals of the SPD generally remains less than Up.



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