Читать книгу Practical Power Plant Engineering - Zark Bedalov - Страница 58

An industrial plant of this magnitude will have approximately 400–500 motors and electrical feeders. Obviously, we cannot extract all these motors and feeders from the flow diagrams, but as the design progresses, and the major equipment is procured, the number of motors and drives generally increases and the load grows. Having gone through the load investigation and the load placement within the plant, we have finally arrived at a point of drawing an overall plant diagram, the key one‐line diagram as shown in Figure 2.7. We will call the feeders drawn above the 13.8 kV drawing line as the incomers and those below the line will be called the plant feeders.

Now we can assign the loads (MW) to each area of the plant and to specific MCCs, separated by different voltage categories, MV and LV. The presentation of the diagram is relatively simplistic, made for the book only. A more comprehensive drawing would be required if prepared for the real project.

Figure 2.7 Key one‐line diagram.

The main 13.8 kV switchgear for the aforementioned project will require about 11 feeder breakers to feed various 4.16 kV and 480 V load centers, three incomers, and a bus tie breaker for a total of 16 breaker and switchgear cells. You will note that the 480 V load centers are looped together to two 13.8 kV breakers from either side of the 13.8 kV bus to enhance reliability of supply of the load centers.