AC Power Distribution Systems and Standards


AC Power Distribution Systems and Standards


AC Power Distribution Systems and Standards
AC Power Distribution Systems and Standards

    The best distribution system is one that will, cost-effectively and safely, supply adequate electric service to both present and future probable loads. The function of the electric power distribution system in a building or an installation site is to receive power at one or more supply points and to deliver it to the individual lamps, motors and all other electrically operated devices. The importance of the distribution system to the function of a building makes it almost imperative that the best system be designed and installed. In order to design the best distribution system, the system design engineer must have information concerning the loads and a knowledge of the various types of distribution systems that are applicable. The various categories of buildings have many specific design challenges, but certain basic principles are common to all. Such principles, if followed, will provide a soundly executed design.


The basic principles or factors requiring consideration during design of the power distribution system include:

• Functions of structure, present and future

• Life and flexibility of structure

• Locations of service entrance and distribution equipment, locations and characteristics of loads, locations of unit substations

• Demand and diversity factors of loads

• Sources of power; including normal, standby and emergency

• Continuity and quality of power available and required

• Energy efficiency and management

• Distribution and utilization voltages

• Bus and/or cable feeders

• Distribution equipment and motor control

• Power and lighting panelboards and motor control centers

• Types of lighting systems

• Installation methods

• Power monitoring systems

• Electric utility requirements

Rules of Thumb for Maintenance and Reliability Engineers


Modern Electric Power Technologies

    Several new factors to consider in modern power distribution systems result from two relatively recent changes. The first recent change is utility deregulation. The traditional dependence on the utility for problem analysis, energy conservation measurements and techniques, and a simplified cost structure for electricity has changed. The second change is less obvious to the designer yet will have an impact on the types of equipment and systems being designed. It is the diminishing quantity of qualified building electrical operators, maintenance departments and facility engineers.

    Modern electric power technologies may be of use to the designer and building owner in addressing these new challenges. The advent of micro- processor devices (smart devices) 2 into power distribution equipment has expanded facility owners’ options and capabilities, allowing for automated communication of vital power system information (both energy data and system operation information) and electrical equipment control.

These technologies may be grouped as:

• Power monitoring and control

• Building management systems interfaces

• Lighting control

• Automated energy management

• Predictive diagnostics


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