How Does a Lightning Protection System Work?

There is an old axiom, which states that ‘lightning never strikes the same place twice’.

Where this expression comes from is hard to determine, although it is quite safe to state that it is wrong.

Why is it wrong?

Ask the Blackpool Tower.

Home of the iconic Tower Ballroom this 19th century structure has been hit more than once. The most significant strike happened as recently as July 2016.

So if such iconic buildings can be struck, repeatedly as it turns out why don’t we hear more about it in the news?

The simple response is that they have well designed and maintained lightning protection systems.

In very simple terms a lightning conductor (or rod) is often a copper based alloy mounted at the highest point of a structure and then connected to a grounding point via heavy-duty conductor cables. While this passive approach to lightning protection provides an effective means of preventing excess damage to a structure, the risk of damage to electrical and electronic devices can remain a threat.

Although buildings with a steel frame do seem to fare better during a lightning strike, the risk of fire still remains. This is because loft spaces and wall insulation can begin to burn and it is not until there is a sufficient build up of heat that a fire alarm will sound. The main reason that steel framed buildings fare slightly better that those without is because the steels act as conductors to the ground.

Having a steel frame will not guarantee safety though, as pointed out above the risk of fire remains. To this end, it is always going to be good practice to install some form of lightning protection system:

Passive systems are relatively inexpensive to install and with regular inspect/maintenance can easily last the life of the building they are installed on.

A financial benefit of a passive system is there is little to wrong, the lightning conductor itself is a sturdy unit as you can imagine. The grounding points are equally robust so it is the conductor cables that require the closest inspection. The conductor cables need to be of low impedance to work efficiently and reduce the risk of damage to electronic devices.

Some structures are fitted with an external wire mesh, or Faraday cage which, can further reduce the risk of harm to not only the structure of the building but also the contents and occupants. The Faraday cage works by distributing the electrical charge around the exterior of the cage, so the massive charge from the lightning leaves the interior of the ‘cage’ unharmed.

The principal of the Faraday cage was adapted by Dr Austin Richards to create a Faraday suit. From this point he used a Tesla coil to create a show called Dr Megavolt.

Addressing The Equality Act With DDA Handrails

DDA Handrails Equality Act

National statistics show that there are over 11 million adults with a long-term illness. They form a significant percentage of UK consumers so making retail premises and public buildings accessible is critical for business as well as a legal requirement.

Reading the Equality Act 2010 (DDA) shows that businesses and public services must take reasonable steps to remove any physical barriers that make access difficult for the less abled.

What qualifies as reasonable?

The DDA doesn’t actually define what is reasonable and it is all down to the individual businesses to judge what is actually reasonable. Retailers should find out how effective, how practical and the cost of it as well. Ultimately though, only a court can decide what is, and what is not reasonable and companies who have a lot of financial resources are expected to do a lot more when compared to those who don’t have a lot of money.

Planning Tips

DDA Handrails Access

An access audit evaluates the accessibility of your building and it follows the less able visitor’s path of travel. It also covers their arrival and their entry into the premises. When you do conduct an access audit, businesses can then work to identify what they need to try and change in order to make it accessible. Large premises may have a lot of issues that they need to resolve and they need to split these into short, medium and long term sections with priorities.

A key point to take into consideration is the overall height of the handrail and whether a second, lower rail will need to be included. Then there is the consideration of the distance from the wall or partition required for the rail to be of use. After all, if the rail is placed too close to a wall the potential for injury grows.

The DDA standard for handrail height is calculated from the pitch line of the surface of the flight of steps or ramp and should be between 900mm and 1000mm. The clearance from the adjacent wall to the handrail should be between 60mm and 75mm but should not project more than 100mm into surface width of steps, landings or ramps.

Although this may seem obvious to someone familiar with DDA handrail design it is all too easy to overlook. When retrofitting an access-way it is key to take into consideration just how much space the handrails will use in relation to the purpose of the access.

The final step of the initial planning should allow for a minimum of 300mm extension at both the top and bottom nosing of the a flight or flights of steps or a ramped access, while not protruding into an access route.

During the planning phase of a new build consideration should be given to the profile of any ramps to be installed. The maximum angle and height per ramp advised for a hand-propelled wheelchair is a 4.8º angle (1:12) and 500mm with an advised width of 1500mm.

The handrails that run alongside the ramp must comply with the above height regulation with the 300mm extension at the top and bottom of a ramp complete with closed ends. Although on landings the maximum height can be extended to 1100mm.

DDA handrail design can easily accommodate most stair riser situations without the need for specially engineered components. Kee Access Components provide a wide range of fittings that are suitable for virtually any modification.

General Access Considerations

Access to and from premises is an important consideration. The following points should be central to planning:

  • Access solutions should respect the convenience of those who are less abled.
  • Use of space – such as when adjusting an existing space, ramp or stairwell
  • Building regulations should comply with physical adjustments.
  • The intended use of the handrail does not impede emergency access.
  • The handrail should be secured to the mounting brackets with either rivets or screws in order to prevent rotation.
  • Where handrails are joined use internal couplings (Type 514-7) to maintain continuity.
  • The handrail, mounts, couplings and adjacent surfaces should be free of anything sharp or abrasive.
  • The handrail does not impede access to doorways.

One solution is DDA Compliant Handrails. They provide a cost-effective and practical means to make a premises accessible.


What is a DDA Compliant Handrail?

DDA Compliant HandrailsHandrails provide a safe means of access for all. This is especially true for those who find it hard to climb or descend steps. If you have a wide flight of stairs then you will need to have handrails that divide this up into channels. If you have steps that are over 1800mm then it is highly recommended that you use them to divide the flight of stairs into channels that are 1000mm or less. If you have two or more risers then you need to provide a continuous handrail on either side.

DDA handrails should:

  • have a smooth surface and not cold to touch
  • be an ergonomic shape that is easy to group such as circular or oval. The diameter of the handrail should be no more than 50mm for an oval design and between 40 to 45mm for a circular design
  • be easy to see by the use of visually contrasting colours but should not be reflective
  • have a smooth finish to prevent clothing from being caught

Finish compatibility

As mentioned previously a DDA handrail design should be finished in such a way that it is smooth to the touch, while having a non-slip and not cold to touch coating. The colour of this coating should contrast the nearby walls in order to be easily recognisable by the visually impaired but not be reflective.

Fasteners used to joint the component parts of the handrail should be used in such a way as to not produce sharp of abrasive edges that could cause injury. These fasteners should be used for both stairway and ramp handrails.

DDA Access is Kee

Building Regulations and the Equality Act make it very clear that a significant percentage of the population require access to public and commercial buildings. It shouldn’t be a second thought for companies to design access this way.

Our Guide to DDA Compliant Handrails provides an in-depth look at the considerations that need to be taken when it comes to accessible handrail systems. It’s free to download here.

Early Streamer Emission (ESE) Lightning Protection Systems

In this previous article we talked about passive lightning protection systems. In the following article we will be paying more attention to active or early streamer emission (ESE) protection systems.

In very simple terms, the main difference between passive and active systems is that a passive system is a conductor that sits at the highest point of a structure and is connected to the ground terminal with a heavy-duty cable. This type of device is known by a few names such as a lightning conductor or Franklin rod.

These devices are relatively straightforward, in the crudest sense it could be described as a spike pointing skywards. The main difference with an active device is that it uses an ionization system that is activated by electromagnetic field, which is produced by the advancing storm.

An additional bonus of ESE systems is that they provide a greater protection radius than that afforded by a passive lightning conductor.

When the atmospheric conditions are ‘normal’ the device does not appear to work. It simply sits there like any other passive design. However, as a storm approaches the difference in potential between the groundside and the atmospheric side grows.

It is this difference of potential that becomes the power source for the active system.

As this build up peaks the electric field value, which is able to ionise the air around the tip and this happens at a higher speed than with a simple rod, this in turn allows an increase in voltage within the device that is higher than at ground level.

What happens next is the formation of an upward leader from corona discharges (streamers) that propagate towards the downward leader. One of these streamers will then become the upward leader and this will continuously propagate towards the downward leading, thus creating the lightning discharge path.

A distinct advantage that the active systems have over their passive brethren is that they can protect a wider area from lightning strikes. As a consequence of providing a greater area of protection, it becomes possible to use fewer active rods in order to provide the same level of defence as a passive system. An added bonus is that an active system protects not only the structure that it is mounted to, but also surrounding and open areas.

Please Note: At the time of writing, this type of lightning protection system is not part of the current British Standards BS EN 62305 Protection Against Lightning. Whilst they are used effectively in other countries, we always advise you follow best practices and adhere to the standards.