Building electrical systems and industrial power distribution

Abstract

The utilization of energy resources is considered one of the most challenging tasks, while finding the most optimal, proper, and efficient ways to effectively use these important resources is an essential ingredient of sustainable development. In any electrical system, power must be transferred from the service equipment to the lights, machines, electrical motors, equipment, appliances, and electrical outlets. Regardless of the wiring methods used, the electricity carrying conductors and cables fall into one of two categories: feeders or branch-circuit conductors. Important aspects of the electrical system design involve building electrical service, service entrance, branch circuits, feeders, panel-boards, switchboards, switchgears, and load centers, and the calculations and sizing of their associate equipment and devices, as well as the protection devices and conductors. Panel-boards, switchboards, feeders and branch circuits, and associated fittings and devices are important components of the power distribution inside the buildings, industrial, and commercial facilities. Cables are usually contained in raceways, conduits, ducts, or cable trays, protecting them from mechanical damage and influences of other cables. In addition to structural requirements, when designing cable tray systems, the electrical requirements must also be carefully considered, as well as to be complaint to the specifications and requirements of the codes and standards. Often the design information is presented in the form of cabling diagrams, an important communication tool between designer, engineers, and technicians. In order to properly develop cabling diagrams requires in-depth understanding of the NEC, codes and standards regarding branch circuits, feeders, loading receptacles and outlets, switching requirements, and specifications, etc. This chapter is exploring the characteristics of electrical service, feeders, and branch circuits. It introduces the design elements, code and standard requirements, and specifications for service entrance, and inside the utility metering practices. An important aspect of the electrical and industrial power system design involve the calculation and design of branch circuits and feeders to supply various loads in a given occupancy and facility. The general purpose of a conduit, duct, or a raceway is to provide a clear and protected pathway for a cable, or for smaller conduits (inner ducts). Advances in cable technologies, costs of repairing sensitive cable materials or to replace the cables as needed have driven preferences for protective conduits over direct cable burial into the ground or walls. In industrial facilities, the electricity is supplied to the loads from the load centers, containing the equipment necessary to protect and control the power flow and the loads. There exist different load center types, with their selection based primarily on the electrical requirements and installation environment. Load centers are housed in metal enclosures to protect enclosed equipment, nearby objects and personnel in the event of equipment malfunctions. Load centers supplying large motors and smaller load centers are referred to as switchgears, while smaller load centers specialized to supply small to midsize electrical motors are called motor control centers (MCCs). Load centers incorporate switches, circuit breakers, fuses, and disconnect devices to route power and in the event of faults, to isolate electric circuit sections. Switchgears have three basic functions: (a) protection and safety, (b) electrical isolation to permit work and testing, and (c) local or remote circuit switching. Developments in switchgear design have led to the introduction of network support for monitoring, control, and advanced diagnostic capabilities, loading and a host of other operational parameters. This chapter will introduce the most common and important aspects associated with panel-boards, switchboards, service, feeders, branch circuits, raceways, and cable trays. After completing this chapter, the readers are able to identify the feeder and branch circuit sections of power distribution, describe the branch circuits, feeders, and their characteristics and functions, conduits, and raceways are able to calculate them using requirements and appropriate specifications of codes and standards, size branch circuits and feeders in accordance with such specifications and requirements, and finally use the codes to size feeder conductors and cables.