Electricity earthing

An electrical earth system comprises the provision on the supply system of an earth connection to facilitate earth fault current flow, the connecting of all exposed metalwork within the installation to a common grounding terminal and the connection of this terminal to earth. For a complete installation the principal factors which need to be considered, are ... 

A program to ensure that a well-designed and effective electrical earth-grounding system and equipment bonding system is in place is an essential first step in... 

Computer hardware will require electrical earths and signal earths for intrinsic and nonintrinsic safety to be achieved. Wiring diagrams should be available as appropriate to site-specific installations. 

Any surface which is in contact with a plasma will be bombarded by electrons and ions. Since electrons escape much faster from the plasma to the surface, a sheath (a positively-charged) region is formed. The electrons are described as being more mobile. In this way a potential difference between a grounded surface and the plasma volume is maintained. This is referred to as the plasma potential (Vp). If the surface is allowed to float, i.e it is not electrically earthed, the floating surface also acquires a negative potential with respect to the plasma. Ions are accelerated across this potential and impart energy to the surface. 

In order to minimise the possible damage to a cable, and to provide a safe path for electrical earth return currents, it is necessary to specify a metallic armouring. There are several types of metallic armouring used in the oil industry, i.e. galvanised steel wires (GSWA), aluminium wires (AWA), tinned copper wire braid (TCUWB), phosphor bronze wire braid (PBWB). 

Tanks and pipes should be electrically earthed. It is necessary to equip storage tanks with steam blanketing to be used in case of fire and preferable to incorporate a high temperature alarm in the upper section of the tank to warn of fires. 

Electrical earth connections, short-circuit protections, etc. 

Tendency to form corrosive/explosive or inflammable dust during conveying. Some materials such as water sprinklers, electrical earth connection, nitrogen blanketing, may need special precautions. 

BS 2754 1976 Construction of electrical equipment for protection against electric shock BS EN 60204, Safety of machinery - Electrical equipment of machines, part 1 Specification for general requirements BS 4444 1989 Guide to electrical earth monitoring... 

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