Electrical installations protection

National Electrical Code, No. 70, National Fire Protection Association, Boston, Mass., 1993 Electrical Installations in Chemical Plants, No. 497A, 1992. Electrical Safety Practices, Monograph Nos. 110—113, Instmment Society of America, Research Triangle Park, N.C., 1965—1972 Electrical Safety Abstracts, 4th ed., 1972. 

In other designs, a diffused siUcon sensor is mounted in a meter body that is designed to permit caUbration, convenient installation in pressure systems and electrical circuits, protection against overload, protection from weather, isolation from corrosive or conductive process fluids, and in some cases to meet standards requirements, eg, of Factory Mutual. A typical process pressure meter body is shown in Figure 10. Pressure measurement from 0—746 Pa (0—3 in. H2O) to 0—69 MPa (0—10,000 psi) is available for process temperatures in the range —40 to 125°C. Differential pressure- and absolute pressure-measuring meter bodies are also available. As transmitters, the output of these devices is typically 4—20 m A dc with 25-V-dc supply voltage. 

NFPA 497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 1997 edition. National Fire Protection Association, Quincy, MA. 

Max. rated voltage of 24 V Electrical installation of loadcarrying compartment to be dust-protected (at least IP54 or equivalent) or in case of Compatibility Group (see Table 14.9) flame-proof Ex d (at least IP65 or equivalent)... 

Flammable and Combustible Liquids Code Standard for the Installation and Use of Stationary Combustion Engines and Turbines National Electrical Code Recommended Practice on Static Electricity Lightning Protection Code... 

NFPA-325 Guide to Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solids, (1994 ed.), NFPA-321 Basic Classification of Flammable and Combustible Liquids (1991 ed.), NFPA-497A, Classification of Class 1 Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas (1992 ed.), and NFPA-497B, Classification of Class II Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas (1991 ed.), National Fire Protection Association, Quincy, MA. 

If a continuous metallic structure is immersed in an electrolyte, e.g. placed in the sea or sea-bed or buried in the soil, stray direct currents from nearby electric installations of which parts are not insulated from the soil may flow to and from the structure. At points where the stray current enters the immersed structure the potential will be lowered and electrical protection (cathodic protection) or partial electrical protection will occur. At points where the stray current leaves the immersed structure the potential will become more positive and corrosion may occur with serious consequences. 

AMD 1 Electrical apparatus for use in the presence of combustible dust. Part 1 Electrical apparatus protected by enclosures - Selection, installation and maintenance (AMD 10763) dated October 1999. Inc.Cor.l(10856)Part.s/s BS 6467-1 1985 and BS 6467-2 1988, remain current... 

National Fire Protection Association (NFPA), NFPA 497A. Classification of Class I Hazardous Locations for Electrical Installation in Chemical Process Areas. NFPA, Quincy, MA, 1992. 

National Electrical Code,No. 70, National Fire Protection Association, Boston, Mass., 1993 Electrical Installations in Chemical Plants, No. 497A, 1992. 

Due to the quite different structures of industrial plants equipped with electrical installations, there are different probabilities for the existence of potentially explosive atmospheres formed by gas-air, vapour-air or dust-air mixtures. With respect to economical reasons, the types of explosion protection for electrical apparatus and systems will depend strongly on the explosion risk at the installation point. It is very unusual to construct and build all explosion protected electrical apparatus in such a manner that they can operate permanently in a surrounding hazardous atmosphere with combustible gases, vapours and dusts in air. The common way is to classify different areas in industrial plants according to the probability for the existence of a hazardous atmosphere and to establish adequate types of explosion protection. In other words, industrial plants with potentially explosive atmospheres are divided and classified into zones. ... 

A certain problem of electrical installations with a high degree of ingress protection against solid foreign bodies and water is the exchange of internal... 

NFPA 497 (2004) Recommended practice for the classification of flammable liquids, gases or vapors and of hazardous (classified) locations for electrical installations in chemical process areas. (National Fire Protection Association). 

NFPA 497. Recommended Practice for the Classifications of Liquids, Gases or Vapors and of Hazardous Locations for Electrical Installations National Fire Protection Association Quicy, MA, USA, 1997 Edition. 

Electrical Equipment Protection. Equipment must be constantly protected against excessively high currents from short circuits or faulty operation. Circuit breakers which open the circuit automatically on overload are sized and installed throughout the entire distribution system, including both primary and secondary systems. The design philosophy is to confine the interruption to the piece of equipment or circuit at fault, thereby avoiding interruption of an entire plant. 

Artificial ventilation for the protection of analyser(s) houses. Recommendations for inspection and maintenance of electrical installation in hazardous areas (other than mines). 

The provision of a safe eiectrical system is fundamental to the whole concept of using eiectricity in and around buildings safely. The electrical installation as a whoie must be protected against overload and short-circuit damage, and the peopie using the instaiiation must be protected against electric shock. 

Earthing is the connection of the exposed conductive parts of an electrical installation to the main protective earthing terminal of the installation. 

A conduit is a tube, channei or pipe in which insuiated conductors are contained. The conduit, in effect, repiaces the PVC outer sheath of a cable, providing mechanicai protection for the insuiated conductors. A conduit instaiiation can be rewired easiiy or aitered at any time, and this flexibility, coupled with mechanical protection, makes conduit installations popular for commercial and industrial applications. There are three types of conduit used in electrical installation work steel, PVC and flexible. 

All electrical installations and installed equipment must be safe to use and free from the dangers of electric shock, but some installations or locations require special consideration because of the inherent dangers of the installed conditions. The danger may arise because of the corrosive or explosive nature of the atmosphere, because the installation must be used in damp or low-temperature conditions or because there is a need to provide additional mechanical protection for the electrical system. Part 7 of the lET Regulations deals with these special installations or locations. In this section we will consider some of the installations which require special consideration. 

The protection provided by insulating the live parts of the electrical installation is called ... 

Briefly explain why an electrical installation needs protective devices. 

The NICEIC is an independent consumer safety organization, set up to protect users of electricity against the hazards of unsafe electrical installations... 

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