If you think you have an unsafe electrical installation you should first warn everyone to stay away from it and - if safe to do so - switch it off. You should then contact a competent person, such as an approved contractor from:

Electrical Contractors' Association (ECA)
National Association for Professional Inspectors and Testers (NAPIT)
National Inspection Council for Electrical Installation Contracting (NICEIC)
The Electrical Contractors' Association of Scotland (SELECT)
If the installation you think is unsafe is not owned by you or under your control, you should try to find out who owns it and then contact them. Electrical distribution poles, pylons and equipment should have a contact telephone number attached to them.

If you can't find out who owns or controls an electrical installation that you think is unsafe, you should contact your local authority or HSE.

When underground cables are damaged, people can be killed and injured by electric shock, electrical arcs (causing an explosion), and flames. This often results in severe burns to hands, face and body, even if protective clothing is being worn.

Damage can be caused when a cable is:

cut through by a sharp object such as the point of a tool; or
crushed by a heavy object or powerful machine.
Cables that have been previously damaged but left unreported and unrepaired can cause incidents.

The HSE booklet "Avoiding danger from underground services" gives guidance on how you can manage the risks of digging near underground cables.

The Electricity Networks Association (ENA) publication "Watch It! When digging in the vicinity of underground electric cables also provides advice".

What you need to do

If you are digging or disturbing the earth you should take care to avoid damaging underground services. Underground electrical cables can be particularly hazardous because they often look like pipes and it is impossible to tell if they are live just by looking at them.

Damage to underground electrical cables can cause fatal or severe injury and the law says you must take precautions to avoid danger.

Excavation work should be properly managed to control risks, including:

Planning the work
Using cable plans
Cable locating devices
Safe digging practices

It is advisable to use a residual current device (RCD) whenever possible but particularly in wet or damp locations, such as outdoors. An RCD rated at no more than 30 mA limits the energy in a particular type of electric shock and can save your life. However, an RCD cannot protect you from every type of electric shock, so you should still make sure that circuits are securely isolated before you work on them.

It is best to use an RCD that is incorporated into the switchboard of your installation. This means that all circuits fed from that RCD are protected by it. An RCD that is incorporated into an ordinary mains socket, or plugged into it, will protect anything attached to that socket, but it is possible that equipment may be plugged into another, unprotected socket.

RCDs should be regularly tested by pressing the 'test' button and making sure the RCD trips. Faulty or inoperative RCDs should be removed from use.

RCDs rated above 30 mA provide very limited protection against harm from an electric shock. For further guidance, see: information on RCDs.

If you use electrical equipment in particularly harsh conditions, it is worth selecting lower voltage equipment powered by a transformer with an output centre tapped to earth, or powered by a battery. Additional precautions may also be required, depending on the specific location. See Section 7 of BS7671 'Requirements for Electrical Installations, IET Wiring Regulations. Seventeenth edition' for guidance on this. For details, see: British Standards Institution.

You can do your own electrical work if you are competent to do so. Simple tasks such as wiring a plug are within the grasp of many people but more complex tasks, such as modifying an electrical installation, may not be.

It is particularly important that anyone who undertakes electrical work is able to satisfy the requirements of the Health and Safety at Work etc Act 1974 and the Electricity at Work Regulations 1989.

For work on electrical installations below 1000 volts AC, you should be able to work within the guidelines set out in BS7671 'Requirements for electrical installations. IET Wiring Regulations. Seventeenth edition'. For details, see: British Standards Institution. Other work should be carried out according to the guidelines set out in the relevant industry standard.

Those who wish to undertake electrical testing work would normally be expected to have more knowledge and be able to demonstrate competence through the successful completion of a suitable training course.

More complex electrical tasks, such as motor repair or maintenance of radio frequency heating equipment, should only be carried out by someone who has been trained to do them.

issues of competence are covered in:

Memorandum of guidance on the Electricity at Work Regulations 1989. Guidance on Regulations
Electricity at work: Safe working practices
Electrical safety at work: Resources

A person can demonstrate competence to perform electrical work if they have successfully completed an assessed training course, run by an accredited training organisation, that included the type of work being considered. As part of that course, this person should have demonstrated an ability to understand electrical theory and put this into practice.

A successfully completed electrical apprenticeship, with some post-apprenticeship experience, is a good way of demonstrating competence for general electrical work. More specialised work, such as maintenance of high-voltage switchgear or control system modification, is almost certainly likely to require additional training and experience.