EECE 887 Distribution System Engineering

1. EECE 887 Distribution System Engineering CHAPTER 1 Power Delivery Systems

2. SUBSYSTEMS • Generation • Transmission • Subtransmission • Distribution Kansas State University

3. Billions of Dollars • Generation -- 40% • Transmission -- 20% • Distribution -- 20% Kansas State University

4. MISSION • Reach every customer • Meet demands of customers • Supply reliable power • Provide fluctuation free voltage • Provide power with low harmonics • Keep cost low Kansas State University

5. Hierarchical Structure Source: Willis Kansas State University

6. VOLTAGE LEVELS • Generation: 4 kV to 34.5 kV • Transmission: 138 kV to 1100 kV • Subtransmission: 34.5 kV to 161 kV • Distribution (Primary): 4 kV to 34.5 kV (Most common is 12.47 kV) • Distribution (Secondary): 120/240 V Kansas State University

7. OBSERVATIONS • Transformers separate the levels • Equipment size and capacity decrease as we move down into the system. However, number of equipment increases. • Net capacity increases • Reliability drops as we move closer to customers Kansas State University

8. Distribution Service Transformer Kansas State University

9. Service Transformer Schematic Source: Gonen Kansas State University

10. Reliability Statistics Source: Willis Kansas State University

11. Further Observations • Transmission Systems: • Very high capacity • Networked for high reliability • Designed to provide system stability • Subtransmission Systems: • Medium capacity • Networked for high reliability • Designed for stability as well as power delivery needs Kansas State University

12. Further Observations • Distribution Substations: • Link between transmission and distribution • 1 to 6 transformers of 5 MVA to 150 MVA (generally more than 1 for contingency) • The substation also has high and low voltage buses, circuit breakers, metering and protective equipment, and a control house. Kansas State University

13. Further Observations • Feeders: • Overhead lines mounted on wooden poles or underground cables (3 to 10 times more expensive than overhead) • Underground cables used for aesthetics and in dense urban areas. • 2 to 12 feeders per substation • 2 MVA to 30 MVA per feeder • Radial arrangement Kansas State University

14. Dendrillic Configuration Source: Willis Kansas State University

15. Components of Distribution System (Primary side) • Primary trunk • Main branches • Trunk and main branches are usually three-phase • Switches • Normally Closed (NC) • Normally Open (NO) • NO switches are closed during emergencies Kansas State University

16. Underground feeder get-away to prevent congestion of wires • Laterals • Branches off of main feeders • one or two phase • Different phases are tapped alternately to maintain balance • 10 kVA to 2 MVA • Overhead or underground (buried directly) Kansas State University

17. Secondary System • Close to customers at utilization voltage • Radial • Feeds 1 to 12 customers (4 to 6 is more common) Kansas State University

18. Distribution Secondary Source: Willis Kansas State University

19. What is Distribution System? • It consists of feeders, service transformers, and secondary system. • In some cases distribution substation is also included. • Other equipment: • Voltage regulators and tap changers to maintain voltage levels • Capacitors to compensate inductive loads Kansas State University