【正文】 ghting, and auxiliary systems include: 1) Magnitudes, quality, characteristics, demand, and coincidence or diversity of loads and load factors 2) Service, distribution, and utilization voltages and voltage regulation 3) Flexibility and provisions for expansion 2 4) Reliability and continuity 5) Safety of personnel and property 6) Initial and maintained cost 7) Operation and maintenance 8) Fault current and system coordination 9) Power sources 10) Distribution systems 11) Legally required and optional standby/emergency power systems 12) Energy conservation, demand, and control 13) Conformance with regulatory requirements 14) Special requirements of the site related to: seismic requirements, altitude, sound levels, security, exposure to physical elements, fire hazards, hazardous locations, and power conditioning and uninterruptible power supply (UPS) systems Safety Safety of life and preservation of property are two of the most important factors in the design of the electric system. This is especially true in mercial buildings because of public occupancy, thoroughfare, and high occupancy density. In many mercial buildings, the systems operating staff have very limited technical capabilities and may not have any specific electrical training. Various codes provide rules and regulations as minimum safeguards of life and property. The electrical design engineer may often provide greater safeguards than outlined in the codes according to his or her best judgment, while also giving consideration to utilization and economics. Personnel safety may be divided into two categories: 1) Safety for maintenance and operating personnel 2) Safety for the general public Safety for maintenance and operating personnel is achieved through the proper design and selection of equipment with regard to enclosures, keyinterlocking, circuit breaker and fuseinterrupting capacity, the use of highspeed fault detection and circuitopening devices, clearances, grounding methods, and identification of equipment. Safety for the general public requires that all circuitmaking and circuitbreaking equipment, as well as other electrical apparatus, be isolated from casual contact. This is achieved by using deadfront equipment, locked rooms and enclosures, proper grounding, limiting of fault levels, installation of barriers and other isolation (including special ventilating grills), proper clearances, adequate insulation, and similar provisions outlined in this remended practice. Circuit protection is a fundamental safety requirement of all electric systems. Adequate interrupting capacities are required in services, feeders, and branch circuits. Selective, automatic isolation of faulted circuits represents good engineering practice. Fault protection, which is covered in Chapter 9, should be designed and coordinated throughout the system. Physical protection of equipment from damage or tampering, and exposure of unprotected equipment to electrical, chemical, and mechanical damage is necessary. Design Considerations Electrical equipment usually occupies a relatively s