Selection electrical equipment

There are many advantages to selecting electrical equipment with higher energy efficiency, such as reduced electrical losses, less heating in electrical room, cost beneficial in long term... 

Correct selection of heating equipment and zoning of electrical equipment to reduce the chance of an ignition source arising. 

All electrical protective equipment (e.g., circuit breakers, fuses, bus bars, and motor starters) is rated for maximum short circuit currents by NEMA standards. Proper selection of equipment must be based on available short circuit currents. 

In areas where electrical equipment is exposed to contaminants, the selection of equipment whose contacts are oil-immersed or hermetically sealed can increase reliability and equipment life. Similarly, providing environmentally-controlled equipment rooms can greatly increase equipment life at locations where contaminants are prevalent. In offshore and other areas exposed to salt, type 316 stainless steel is often preferred over types 303 and 304, which will pit with time. Likewise, in similar locations, equipment fabricated from galvanized steel will corrode much more rapidly than equipment hot-dip galvanized after fabrication. 

Distances are recommended for zoning of electrical equipment, separation of storage from buildings etc. Distances are also proposed (on the basis of experience) to minimize the escalation or effects on site of fire, explosion, toxic relea.se or similar incident. Selected sources of information are summarized in Table 11.6. A typical example is given in Table 11.8 subject to the requirement of Table 11.7. 

PM 82 The selection, installation and maintenance of electrical equipment for use in and around buildings... 

OSHA Requirements. OSHA requirements state that one of three options must be fulfilled regarding the selection of electrical equipment for locations classified as hazardous (7). 

The team s expertise should be compatible with the kind of audit to be conducted. Audits of certain programs may require the selection of specialists in electrical equipment, pressure vessels, maintenance, motor fleet activities, and other fields. Line managers of other units are excellent members of audit teams. They bring a different background to spot weaknesses. In addition, participation is a learning experience for the manager and increases the involvement of those responsible for results. It may also be helpful to have a previous auditor of the unit as one member of the audit team. 

Financial considerations -selecting explosion protected electrical equipment... 

Electrical service should be provided in the normal fashion in accordance with local building and electrical codes. Clean space service requires no special treatment, and should provide a 25-50 A surplus over worst-case processing demands, to allow for additional electrical equipment and source power fluctuations. Fixture types, sealable outlets, and hard-wiring of processing equipment should be selected and carried out in accordance with industry standards and electrical codes. ° ... 

In either case, the surface temperature must not exceed the ignition temperature of the gases or vapors. To minimize the cost of using special electrical equipment, the electrical equipment is selected in such a way that the higher the likelihood of forming a flammable mixture in an area, the lower should be the risk of causing ignition by the electrical equipment. 

Some of these documents have become obsolete or little used, e.g. BS229, BS1259, Electrical Installations in Flammable Atmospheres (from ICI) whilst others have been up-dated several times. New standards have also been introduced. A similar situation exists with the international standards pertaining to the selection of equipment for hazardous areas, many more references could be quoted. 

In the European and UK standards the term Zone is used for hazardous areas, whereas the term Division is used in the USA. In practice the end result of selecting appropriate equipment for a Zone or Division is usually very similar. There are a few subtle differences, especially when selecting electric motors. The zonal definitions vary in wording from one document to another but the essential elements are as follows. 

The book includes summaries of the necessary theories behind the design of systems together with practical guidance on selecting most types of electrical equipment and systems that are normally encountered with offshore production platforms, drilling rigs, onshore gas plants, pipelines, liquefied natural gas plants, pipeline pumping stations, refineries and chemical plants. 

Area classification is employed to identify locations where electrical equipment could provide a source of ignition to flammable liquids and gases/vapours that may be present. It is also used to prevent dust explosions. Area classification is necessary for selecting and installing safer electrical and instrumentation equipment, and its review is very important for revamp projects as it may influence site selection and also project cost. In some cases it may require a change in electrical area classification for existing facilities and hence require replacement of some electrical and instrumentation equipment. 

The selection of the electrical equipment can play a major part in negotiating the price paid for electricity for the plant. The zinc cellhouse is a major consumer of electricity and may be the most important load on the distribution grid in the area. The characteristics of the rectifiers that affect the performance of the grid must be controlled much more closely than would be demanded of a minor consumer. 

The powertrain configuration is identical for both the friction hoist and the Blair hoist, see Figure 5. The main transformers consist of two series coimected transformer phase-shifting vector groups Illdl 1 and YyO. All electrical equipment of the powertrain is selected with about 10% margin on a calculated load trip, both RMS and peak values. 

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