Lightning and Surge Protection

Lightning protection

Historic England recommends that lightning protection is considered for all churches, and tall or prominent historic buildings. However there is no system that will give absolute protection, and the significance of a building needs to be balanced against providing an acceptable level of protection.

Historic England's guidelines are:

• A risk assessment should be carried out
• Proper consultation with the appropriate authorities or denominational bodies is essential
• Archaeological supervision of ground-disturbing work may be needed
• A tower-only system is likely to provide acceptable protection in most cases
• The aesthetic appearance of the lightning protection system needs to be carefully considered
• Systems need to be professionally designed, installed and maintained

Historic England's Lightning protection guidance provides advice on the design, installation and maintenance of lightning protection systems. The guidance includes briefing on the British Standard European Norm BS EN 62305, risk assessments and what is relevant for historic buildings.

There is also a section on Surge Protection Devices (SPDs).

Lightning protection is specialist work and requires expert design and installation.

Surge protection

Electric surges are frequently the cause of damage and failure to systems containing electronic components.

Surges are generated when there is:

• A direct lighting strike
• An indirect lighting strike near the electrical installation
• A local switching operation in the power supply network, the switching of nearby high loads (like lifts or air conditioning equipment) or the tripping of protective devices

Direct lightning strikes cause massive destruction and often fires. Indirect strikes contain less energy than direct but can still result in the failure of data servers, heating controls, safety systems such as fire and intruder alarms, and the building power supply itself.

An external lightning protection system is important. It protects people, property and against mechanical destruction and fire. However part of the current from a strike still flows into the building via the main earth bar (MEB) even though the rest is discharged to earth via the earth terminations.

Indirect lightning strikes, although the transient overvoltage is lower, can also cause a lot of damage. Such surge events include remote strikes to overhead lines or strikes near to the building or installation via the incoming electrical supply.

Equipment can be protected with surge protection devices (SPDs) or arresters. The types of surge arrester are as follows and a comprehensive protection system will include all three types:

• Type 1 - These should be installed as close to the electrical supply intake position. Type 1 SPD are used to use to protect other electrical or electronic services such as telephone, DSL (Digital Subscriber Lines) and broadband cable networks. This type is not enough to protect downstream devices such as distribution boards, machinery and computer equipment. They are capable of discharging any surge at least once.
• Type 2 - These are installed at each distribution board. Type 2 are used to prevent the spread of overvoltage within the electrical installation and protect each circuit load. They are capable of discharging a surge only once.
• Type 3 - These are used to supplement type 2 and are installed in parallel with, and used to protect, sensitive loads such as computers, printers and fire alarm panels. This type of SPD can be installed as part of a power strip thus protecting a number of local devices at once.

Specialist advice should be sought about selecting SPDs and their installation from a qualified electrical contractor and a member of ATLAS, or a chartered electrical engineer (see Lightning Protection guidance). The installation of SPDs must be undertaken by a qualified electrical contractor.

Learn more

View the 2020 webinar: Buildings at risk: lightning protection for historic buildings and churches

Lightning strikes to historic buildings can cause serious damage. This webinar looks at the development of lightning protection standards, the cause and effect of lightning strikes and how to apply the new British Standards to listed and heritage buildings. The presentation also looks at the individual components that make up a lightning protection system and how they work.

For the best webinar experience please use Google Chrome browser or download Adobe Connect.