Industrial design application for power distribution over extra-long distances

Typically, large loads associated with petroleum distribution systems are located in a relatively confined plant area. Scattered distribution systems often are not of very large capacity. The combination of large industrial requirements coupled with the geographic requirements of a utility system created a challenging design. There are numerous motors sized from 150 to 450 horsepower with additional 1000 horsepower compressors. These are located on up to 12-mile long radial taps spread over a 45-mile long distribution feeder. Total load is in excess of 20 MW. Starting is a very serious consideration. Because of economics, additional transmission substations for supply are not an option. The system voltage is restricted to 25 kV. Meteorological conditions add to the complexity of the design. Lightning protection must be extensive. Additionally, ambient temperature, wind, icing and severe storms must be considered. Capacitor size and location is critical to maintain proper voltage and reasonable power factor. Protective device coordination is vital to maintaining overall system reliability. The diversity of load and location demands computer modeling. Newer, graphical interface software transforms a tremendous problem into a viable project. The procedures and design considerations are items of interest to any engineer who is involved with large scale projects, uses large horsepower motors, or who works with scattered loads.