Isolation of electricity

Polyethylene is used mainly for packing and for the isolation of electrical cables polyethylene is one of the plastics which is least permeable to water vapour. Actually, numerous applications have been found for this product. Polyethylene has even been used to slow down neutrons in nuclear reactors ... 

Ensure the complete electrical isolation of electrical equipment and power supplies. Enclose all power supplies in a manner that makes accidental contact with power circuits impossible. In every experimental setup, including temporary ones, employ suitable barriers or enclosures to protect against accidental contact with electrical circuits. 

The isolation of an electrical circuit involves more than switching off the current in that the circuit is made dead and cannot be accidentally re-energized. It, therefore, creates a barrier between the equipment and the electrical supply which only an authorized person should be able to remove. When it is intended to carry out work, such as mechanical maintenance or a cleaning operation on plant or machinery, isolation of electrical equipment will be required to ensure safety during the work process. Isolators should always be locked off when work is to be done on electrical equipment. 

Isolation of electrical supplies throughout a building (service risers) can be achieved by ensuring that the risers are fire resistant enclosures, thus should a fire start the secondary hazard (such as the production of smoke) is contained within the enclosure and will not have an adverse effect upon those escaping. 

Details of the removal or isolation of electrical, gas and other services, including drains... 

Oxidation of Silicon. Silicon dioxide [7631-86-9] Si02, is a basic component of IC fabrication. Si02 layers are commonly used as selective masks against the implantation or diffusion of dopants into silicon. Si02 is also used to isolate one device from another. It is a component of MOS devices, and provides electrical isolation of multilevel metalliza tion stmctures (12). A comparison of Si and Si02 properties is shown in Table 1. 

Fig. 10-5 Protection measure by separation of electrical operational equipment that is connected to the cathodically protected object via the housing, with an FI protection circuit leakage current circuit breaker (see Ref. 14) Tj and isolating transformers (see Ref. 15).

Efforts are made in the construction of new, large tank farms to achieve electrical isolation of buried and cathodically protected fuel installations from all... 

On stretches of electric line, according to Ref. 12, filling tracks without overhead conductors are usually isolated from the rest of the rail network with insulating joints in order to keep the rail currents flowing to the tank installation as... 

The above has been isolated from all sources of electrical and mechanical power... 

Bee.iusa the nitrogen pressure was unreliable, it was difficult to maintain a pressure of 0.5 inch water gauge in the metal cabinet. Workers complained that the safety switch kept isolating the electricity supply, so an electrician reduced the setpoint first to 0.25-inch and then to zero, thus effeciocly bypassing the switch. The setpoint could not be seen unless the cover of the switch was removed and the electrician told no one what he had done. The workers though I lie wa,s a good electrician who had prevented spurious trips. Solvent and air leaked into the cabinet, as ilready described, and the next time the electricity supply was switched there was an explosion. 

The basic reasons for grounding an electrical supply system are to limit the electrical potential difference (voltage) between all uninsulated conductive equipment in the area to provide isolation of faults in the system and to limit overvoltage on the system under various conditions. In the case of a grounded system it is essential to ground at each separately derived voltage level. 

Before entry is allowed into a vessel or other confined space, the vessel should be isolated from sources of hazardous material by slip-plating or physically disconnecting all pipelines and by isolating all supplies of electricity, preferably by disconnecting the cables. On the whole, these precautions seem to be followed. Accidents as the result of a failure to isolate are less common than those resulting from a failure to remove hazardous materials or from their deliberate reintroduction as described in Sections 11.1 and 11.2. However, the following are typical of the accidents that have occurred. 

H. Moissan (Paris) isolation of the element fluorine and development of the electric furnace. 

All electrical systems must be provided with protection equipment, the purpose of which is to isolate faulty electrical equipment from the electrical supply system as rapidly as possible. This can be achieved by use of devices which respond directly to the current flowing (e.g. fuses), or by protective relays which respond to fault current flow and are used to initiate the tripping of other devices (e.g. circuit breakers). 

So that only the faulty equipment is isolated from the supply, the protective devices provided throughout a power system must discriminate between faulty and healthy equipment. This discrimination of protective equipment is a key element in the design of electrical systems and the selection of protection devices for use within them. Each electrical system must be provided with an adequate number of suitably rated disconnecting devices located correctly throughout the power system. These must be so arranged that only appropriate devices operate to remove the faulty equipment from the supply. 

Previous considerations have shown that the interface between two conducting phases is characterised by an unequal distribution of electrical charge which gives rise to an electrical double layer and to an electrical potential diflFerence. This can be illustrated by considering the transport of charge (metal ions or electrons) that occurs immediately an isolated metal is immersed in a solution of its cations ... 

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