Electricity

 Aims – To understand the process of providing Electricity to buildings.  Objectives  To understand how Electricity is Generated.  To investigate how Electricity is supplied.  To explore the supply and distribution of Electricity to a domestic building.

 Michael Faraday – (1791 – 1867).  The man who is recognised for his work in Electricity.  1821 – he started working on electromagnetism and converting electrical energy into motive force.  1831 – discovered the induction of electric currents, and built the first dynamo.  Today we rely heavily on the supply of electricity to our homes and businesses, for both light and power.

 We all rely on electricity to provide us with power around our homes.  Televisions, play stations, x box 360’s, computers, lights, kettles, toasters, fridges, freezers, washing machines, computers, radios etc, all require electricity to work.  How would we manage without electricity?

 Electricity is produced throughout the UK by power stations, from the following sources.  Gas – 39%  Coal – 33%  Nuclear – 19%  Renewable - 4%  Hydroelectric – 1%  Imported - 2%  Oil – 1%  (based on figures published in 2004)

accessed 09/03/2011

accessed 09/03/2011

 If we could find an alternative method of producing electricity without using fossil fuels.  We could greatly reduce the amount of CO 2 being pumped into the atmosphere.  This would help to greatly reduce the Greenhouse effect.  Nobody is saying we can not use electricity, we just need to find an alternative to Fossil Fuels.  What happens when we run out of Fossil Fuels?

 By incorporating electricity generating features onto domestic properties, not only does this help the environment, but it can also benefit the householder in terms of cost, for example lower bills.  Incorporating some form of renewable energy device on a home, can help to pay for itself, and any excess electricity produced will be bought by the National Grid.  At present many people pay at least £1000 per year on Gas and Electricity. Accessed 10/03/2011

 Electricity is produced at 25 (kilovolt) kv – three phase supply, at each power station.  It is then fed through step up transformers to increase the voltage to 132kv or 400kv, before it is connected to the National Grid.  Power is then fed through to our Towns and Cities by overhead power lines, before being stepped down to or 33kv.  Power is then stepped down to 11kv, and supplied by underground cable to substations.  From these substations the voltage is then lowered to 415 volt, three phase supply, and 240 volt single phase supply for both commercial and domestic use.

 There are a variety of different overhead cables, predominately most cables used are aluminium which is seen as a cheaper alternative to copper when transporting electricity over large distances  Individual strands of wire 2 – 4mm in diameter are used, these are then layered to form each cable.  Each layer alternates the direction of twist of each layer or wires.  Cable sizes range from 5 – 40mm in Diameter.

 Electricity is normally supplied to domestic property via underground cables.  These cables need to be buried at a safe depth, which when under a road should be 750mm, and for open ground 450mm.  In remote areas the supply may be by overhead cables.  Each system requires a safe earthing system.  And every installation will also include a meter.  All electrical equipment up to and including the Meter, is the responsibility of the electrical supplier.

 To carry electrical currents underground safely, armoured cable is required. The inner cores are multi cored, with protective layers covered in an protective wire coating to help prevent any current leakage from accidental damage. A final plastic coating will help prevent any ingress of water.  The cost of supplying electricity underground is more expensive than using an overhead system, mainly due to the cost of the electrical cable, and the installation costs associated.

 Bradley Marsh, 28, was working for Dwyer Engineering Services Ltd when the incident took place on 12 June He was digging a trench to create a drainage system during the construction of a retirement home in Tovil, Maidstone. The principal contractor at the site had warned that there were underground electrical cables at the site, but Dwyer did not contact the electricity supplier for drawings to identify the location of the cables.  Mr Marsh was using a jackhammer when he struck an 11,000-volt cable and suffered 62 percent burns to his upper body, face, neck and arms. He spent six weeks in hospital and has undergone numerous skin grafts. Doctors have told him that he will never be able to work again owing to his injuries. The HSE found that the firm did not have a cable supervisor on site and no system was in place to identify underground cables. It was also discovered that Mr Marsh had not been trained to dig within 500mm of live cables.

Earthing arrangement for underground cables

 Conclusion  Electricity is carried throughout the country using High Voltage cables.  These cables can either be overhead or underground.  The health and Safety with high voltage cables needs to be carefully managed.  Electrical power is stepped down to 240 volt for domestic property.  Small businesses will use a 415 volt supply.