Distribution System Planning and Design

Importance of Planning

In order for the industry to remain profitable the principal company must obtain the least amount of total cost of ownership. This means selecting system configurations with low cost by also accounting for cost of operation, maintenance & upgrades, and system decommissioning.

Planning is necessary to design a system for optimum performance. While ensuring supply continuity, minimizing power losses, ensuring power quality, and obtaining trouble free operation by selecting appropriate sizing equipment based on surrounding influences. 

Planning for Industrial Distribution Systems

Planning begins with assessing the predetermined energy demand for the facility. To understand what the facility would require for energy consumption prior information of other facilities projects with similar equipment and processes is a good starting point. This only provides a starting point, where a better approximation can be determined based on facility machinery and equipment. Data required to be collected for power estimation include:

· List of Connections Loads and Locations

· Pattern of Loading (process variations)

· Separating Critical Load from Non-Critical Loads

· Loads with High Harmonics

· Inclusion of Future Growth Plans

· Utility Interfacing 

        A list of load locations and pattern of equipment loading will aid in assessing the load factor, demand factor, and diversity factor. Application of these factors is crucial in accurately estimating power requirements for any facility and designing distribution systems. 

Projection of Future Growth

To plan for future distribution system a good grace period is needed to give a good head start. Five years is a nice start for distribution systems. This is due to expansion in distribution systems within a running facility can cause inconvenient operational disruptions. It might be good practice to over engineer the initial capacity by a reasonable amount to account for possible expansions. Another option is to select equipment with dual rated equipment.

        The approach above is for projects with sufficient funds to produce it. For a project with lower funds, planning for future expansion requires space and equipment for the upgraded distribution system. This is approach is done by assuming expansion and having the planning and designs already produced as if to develop the expansion.

Location of Equipment Assets

The general principle is to place distribution system equipment at a center location for loads fed to it. This is an ideal location where benefits of electrical design are: 

· Shorter Cable Routes

· Power Flow Direction Uniformity

· Lower Electrical Losses and Smaller Cabling Sizes

· Minimize Excessive Voltage Drop 

        Proper placement can result in lower cable costs and operational costs by minimizing chance of power loss. Location selecting is not always as simple as taking the shortest path to its destination. It is good to say that once components are in place it is often difficult to move them around. Correct selection during planning is crucial and must receive the a fair amount of attention.