Temporary electrical supplies

Provision and Use of Work Equipment Regulations 1998 and ACoP L22 Electricity at Work Regulations 1989 Lov/Voltage Electricity (Safety) Regulations 1989 Electrical Equipment (Safety) Regulations 1994 

Temporary electrical supplies to sites must be planned to take into account foreseen load requirements, environmental conditions, progress of work and the compatibility and maintenance requirements of the equipment. The competence of electrical subcontractors must be established before contracting, and before they begin work. 

The temporary installation should be certified before bringing it into use. Locked supply cabinets should form part of the system. 

Offices, stores, drying rooms and canteen will be regarded as permanent installations, and therefore the current lEE Wiring Regulations will apply to them. 

When work on live systems is foreseen, a permit-to-work system or other suitable control system should be used. Operatives must not be allowed to work alone on live systems. Only competent electricians should be authorised to instal or modify temporary supplies certification should be provided to cover the modifications made to the premises and the circuits. 

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The value of having one contractor to control the progress of the work can be seen where there are several contractors on a site at different periods. Progress can suddenly come to a halt if a key contractor does not comply with an agreement. For example, if the electrical sub-contractor does not provide a temporary electrical supply, there may be no light and power, causing other contractors to be delayed. 

Temporary electrical supplies provided on construction sites can save many man hours of labour by providing the energy required for fixed and portable tools and lighting which speeds up the completion of a project. However, construction sites are dangerous places and the temporary electrical supply which is installed... 

Temporary electrical supplies on construction sites can save many person-hours of labour by providing energy for fixed and portable tools and... 

Care must also be taken in terms of routing cables and the provision of temporary electrical supplies to ensure that they are kept free from water and plant/ vehicle movements. 

Equipment enclosures to be kept free of moisture by use of desiccant bags or anti-condensation heaters connected to a temporary electrical supply, with where appropriate periodic checks of insulation resistance... 

Have arrangements been made or co-ordinated for temporary electric supplies ... 

The mechanical contractor is usually also responsible for providing adequate pressurized water supply, drainage (with special provisions for low-level areas of the closed-loop water system), bypasses, an electrical supply (typically 110 V, 1 phase, but also 3 phase where temporary pumps are required), HVAC system air purge vents, as well as other facilities, such as site access, toilets, security, and equipment handling systems. 

In modem sprinkler systems (shown diagrammatically in Figure 4.2.10) water is supplied at pressure from tire town mains which charges a pressure tank. When a sprinkler head mptures, the loss of water pressure in the supply pipe triggers the alarm valve. The alarm is actuated by the alarm valve either by diverting part of tire water flow to a hydraulic gong or by actuating an electrical alarm. The pressure tank acts as a buffer to absorb any water hammer effects and to provide a temporary water supply if the mains flow is intermpted. 

At the initial planning stage and as soon as the maximum demand has been assessed, negotiations with the electricity supply company should start so as to ensure the supply will be available when required. In some cases the electricity supply company may have to obtain wayleaves for an overhead line to supply the site and this can take months. For the larger sites, with a substantial demand, the supply company may have to supply at high voltage and will then require a site location for a temporary substation. When it is known that a permanent substation will be required to supply the development, it will sometimes be economic to build and equip the substation first and use it to supply the site. 

Self-contained, man-portable Al-air alkaline batteries are widely used in battlefield applications and remote military locations. The battery units initially come with dry alkali contained in the cells, and water can be added when electrical power is desired. The modules can provide temporary electrical power for mobile shelters, command and control communications centers, and field medical facilities. The man-portable Al-air batteries can act as power supplies for unmanned vehicles. Specific details on the components used in the self-contained, man-portable Al-air battery are shown in Figure 6.3. Such a battery was designed and developed about 15 years ago for UAVs and UUWVs and is capable of providing a nominal power of 1.6 kW and a peak power of 4 kW. But, the next generation of such a battery with high-quality alloy is expected to have a peak power exceeding 5 kW. 

Both temporary and permanent electrical supply installations should be installed in accordance with the latest addition of BS 7671 (lEE Wiring Regulations and the Electricity at Work Regulations 1989). Installations, particularly if of a temporary nature, for example in construction works, must be inspected regularly and tested at intervals no greater than those specified by the installation company. It should be noted that if temporary installations are in position for a greater period than 3 months on a construction site then they should be subject to test in line with HSE guidance every 3 months or when they have been altered. 

Telephones/intercom Protection equipment Electrical controls, inst. meters Lighting and small power Temporary supplies Elec, hace heating Generator AVR... 

Indirect cost. Indirect cost includes a large list of varied supporting equipment, utilities, and land for the modular major equipment cost method proposed herein. These items are commonly called offsites, which include cost of such items as roadways, land, buildings, warehouses, spare parts, maintenance shops, and electric power and water utilities. In addition to offsites, the indirect cost also includes the field-erection equipment, such as erection cranes, temporary construction buildings, welding supplies, and trucks. All of these items are necessities for the major equipment modules. 

We have already determined that the chloride ion is a catalyst to corrosion (Section 3.2.3). As it is negatively charged we can use the electrochemical process to repel the chloride ion from the steel surface and move it towards an external anode. This process, called electrochemical chloride extraction (ECE), desalination or chloride removal, uses a temporary anode and a higher electrical power density than CP, but is otherwise similar (Figure 7.1). Preparation in terms of concrete repair, power supplies etc are similar to those for impressed current cathodic protection except that the power supply is temporary and may be from a temporary source such as a generator. The output is larger, up to 50 V and 2 A-m. ... 

No mains electricity Ok Ok Ok Only possible with alternative power supply Ok Ok with temporary power ICCP requires permanent power... 

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