Eccles Court Company Ltd. - Certified Specialists For Lightning Protection & Earthing
Staff in Eccles Court Company Ltd. have over 30 years experience of installing Lightning Protection systems in Ireland and we are proud of our involvement in many prestigious projects throughout the country over many years.
Our meticulous attention to detail and refusal to compromise
standards and quality are the hallmarks on which we have built our reputation.
We believe that our design and installation experts are the most experienced
in the business.
We are the only Lightning Protection installers in Ireland who are regularly
fully trained and certified by world leaders W.J.Furse
in accordance with all aspects of BS 6651: 1999 standards.
All of our site installation engineers are also qualified electricians and
are trained to evaluate flashover risk from improperly placed conductors and
make necessary corrections on site.
Our services include:
Risk Assessment
Survey
Design
Supply
Installation
Testing and Certification to BS 6651: 1999.
Just some of the many projects undertaken
by us include the following:
• Blanchardstown
Shopping Centre
• 3
Com
•
St Johns Cathedral Limerick
•
Blackrock Clinic Galway
•
Coca Cola- Ballina
•
Boston Scientific- Cork
•
Aer Rianta- Multi storey car park
•
Defence Forces Buildings. The Curragh.
•
McKee Barracks
• Ballincollig
Barracks
There are many more instances where we have provided design and expertise to many of this country’s leading consulting engineers and contractors.
We have also surveyed many old installations where lightning
protection was assumed to be adequate by the client only to discover it was
dangerously deficient. Many old churches with tall spires are examples of
this. It is a popular misconception that once a single conductor is routed
from the highest point of a structure that it will be protected from lightning
strikes.
The famous York Cathedral in England had “lightning protection”
but was badly damaged when struck by lightning several years ago. Understanding
side flashing and how to properly dissipate the massive voltages and currents
produced by a lightning discharge will explain how this type of devastation
can happen.
The most important aspect of any lightning protection installation
is that it is done in FULL accordance with all relevant aspects of BS6651:1999.
Upon the completion of any lightning protection installation, your installer
must provide you with such certification.
Understanding Lightning and how to protect
against it’s powerful effects:
Causes
Lightning is formed as a result of natural build up of electrical
charge separation in storm clouds.
How clouds form is well understood but how the cloud separates positive and
negative charge is not.
Many theories have been put forward but everyone seems to agree that in a
thunder-cloud, ice crystals become positively charged while water droplets
carry a negative charge.
The distribution of these particles normally gives rise to the build up of
a negative charge at the base of the cloud. This build-up at the cloud base
gives rise to a positive build up of charge on the ground. The ground can
be as little as 1km away from the cloud base.
This build-up continues until the voltage difference between the cloud base
and the ground becomes so great that it causes a breakdown of the air’s
resistance, thus creating a lightning discharge.
Prior to the bright flash that we see is the development of a stepped downward
leader within the cloud which moves towards the ground.
This downward movement continues in 50m steps. It is not visible to the naked
eye. When the stepped leader is near the ground, its relatively large negative
charge induces even greater amounts of positive charge on the earth beneath
it, especially on objects protruding above the earth’s surface.
Since these opposite charges attract each other, the large positive charge
attempts to join the downward moving stepped leader by forming an upward moving
streamer. The two meet and form a complete conducting path along which a massive
current attempts to flow in order to equalise the potential between cloud
and ground. This is termed the “return stroke” and is the bright
lightning flash that we see.
Can lightning strike twice in the same place?
Yes. Many tall buildings around the world are struck several times a year.
Some areas appear to be more prone to lightning than others.
Effects and Damage caused by Lightning
Lightning is nothing more than a long spark. However it is estimated that about 2,000 storms exist at any one time in the world. Every second 30 to 100 flashes are discharged to the earth. This means that 3 BILLION lightning bolts bombard the earth each year.
Lightning causes death and injury in four ways:
Direct strikes to the person.
No explanation needed here. Heart failure Brain damage
suspension of breathing, Paralysis and severe burns.
Structural or Fire Damage leading to injury or asphyxiation.
Fire can quickly develop. The resulting smoke can lead
to asphyxiation. Falling
masonry can also be an obvious hazard.
When lightning strikes a building the stroke seeks out the lowest
impedance path
to earth which is normally through the electrical wiring or water pipes.
In order to reach these metal paths the discharge must pass through some type
of
Barrier. In penetrating such barriers, explosive damage usually results. The
explosive effect can dislodge materials with considerable force sufficient
to hurl
relatively large pieces or wood many metres.
Side Flashing
The consideration to be given to the problem of side flashing
cannot be over
emphasised.
The principals of side flash can be explained by the following example.
If the lightning protection system on a structure is hit by
lightning, then the Current flowing through the system and the resistance/impedance
offered by the conductor path will determine the magnitude of the potential
difference seen by the lightning conductors with respect to true earth.
The Lightning conductors can instantaneously have a potential of magnitude
of megavolts (1,000,000V) with respect to true earth. If there is metalwork
in close proximity to the lightning conductors which are connected directly
to earth, then for the purpose of this example we can say that it is at zero
volts with respect to true earth.
If the current flowing down the lightning conductor path at the time of the discharge sees a high impedance along its route and the nearby metalwork (in this case the water tank and associated pipework) offers a lower impedance path to earth, then the discharge will flash over to the nearby metalwork, provided the magnitude of the potential difference is sufficient to breakdown the gap ‘D’.
Such a flashover could dislodge slates and masonry and even cause dry timber to ignite.
Step and Touch voltages.
In the event of a lightning stroke, a voltage gradient
builds up in the soil where the lightning discharge enters the earth. A significant
voltage gradient will exist between two points at varying distances from the
electrode.
The voltage difference across the span of a step a man takes can be lethal.
The step potential of a person is significantly lower in comparison with a
large four legged animal.
The average human step distance is just under one metre whilst the distance
between the front and back legs of an animal such as a horse or a cow is much
greater.
Current will flow through the legs of a man whilst the current flow will be
through the heart region of an animal. Animals naturally shelter under trees
during storms often with fatal results.
If a person is caught out in the open in a lightning storm, what should they do?
Preferably get into a car. If this is not an option they should crouch down
in a foetal position with both feet close together and only their feet touching
the ground.
Do NOT stand under a tree.
It could also be fatal to lie flat out on the ground. Whilst you may not be
hit
directly, step voltage as explained above could be a problem. As the voltage
gradient in the soil decreases over distance, the voltage at your feet may
be considerably higher than the voltage at your hands. A large potential difference
across a human body could be fatal.
Solution
The structure to be protected should be surveyed by a trained specialist and a design and specification in accordance with BS6651:1999 should be prepared. Only components and fittings manufactured in compliance with the above code of practice should be used during installation.
Exotic devices such as those which claim to “attract lightning” by ionisation techniques should be avoided as they do not comply with BS6651:1999
Upon completion a test certificate should be presented to the client.
