EECE 887 Distribution System Engineering CHAPTER 1 Power Delivery Systems

Kansas State University SUBSYSTEMS F Generation F Transmission F Subtransmission F Distribution

Kansas State University Billions of Dollars F Generation -- 40% F Transmission -- 20% F Distribution -- 20%

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

Kansas State University Hierarchical Structure Source: Willis

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

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

Kansas State University Distribution Service Transformer

Kansas State University Service Transformer Schematic Source: Gonen

Kansas State University Reliability Statistics Source: Willis

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

Kansas State University Further Observations F 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 Further Observations F 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 Dendrillic Configuration Source: Willis

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

Kansas State University F Underground feeder get-away to prevent congestion of wires F 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 Secondary System F Close to customers at utilization voltage F Radial F Feeds 1 to 12 customers (4 to 6 is more common)

Kansas State University Distribution Secondary Source: Willis

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