This article is the first of a series in the selection of electrical cables.
Cable selection is an important part of electrical installation design. Selecting the correct size of cable could lower initial cost, lower operating cost, better voltage regulation notwithstanding the safety factor.
The primary objective of earthing (or grounding as referred to in North American standards) is safety, to reduce risks to both human life and installations. The principles of electrical earthing are agreed upon internationally, though in practice, there are differences as to how these principles are best achieved.
Electrical systems were not always earthed. The first systems were unearthed ones with no earth reference at all. Even though such systems still exist in specific areas, they are the exceptions rather than the rule and by and large, some form of earthing is adopted for all power systems.
IEC 60079-0 specifies the general requirements for construction, testing and marking of electrical apparatus and Ex components intended for use in explosive gas atmospheres.
Unless modified by one of the parts in the IEC 60079 series, electrical apparatus complying with this standard is intended for use in hazardous areas in which explosive gas atmospheres, caused by mixtures of air and gases, vapours or mists, exist under normal atmospheric conditions of
The requirements for Electrical apparatus for explosive gas atmospheres have been detailed in the IEC 60079 series.
This article, an extract from IEC 60079-10, will be the first of a series of articles discussing the requirements for explosive gas atmosphere electrical installations. To understand better the requirements for hazardous areas installations, IEC 60079-10 provides the classification of explosive atmospheres.
The objective of IEC 60079-10, Classification of hazardous areas, is to set out the essential criteria against which the risk of ignition can be assessed, and to give guidance on the design and control parameters which can be used in order to reduce this risk.
The IEC 60364 (Electrical Installations of Buildings) and the ANSI/NFPA 70 (NEC) are the bases for most national wiring rules throughout the world.
The NEC evolved along with the growth of electrical systems in North America more than 100 years ago to establish a uniform level of safety, while the development of IEC 60364 documents ensued in 1969 for reasons of harmonization of electrical installation rules to facilitate trade among European countries.
IEC 50529 applies to the classification of protection provided by enclosures for electrical equipment with a rated voltage not exceeding 72.5kV.While this system is suitable for use with most type sof electrical equipment, the manufacturer of the equipment should still be consulted to determine the degree of protection available and the parts of equipment to which the stated degree of protection applies.