eece 887 distribution system engineering chapter 1 power delivery systems
TRANSCRIPT
EECE 887 Distribution EECE 887 Distribution System EngineeringSystem Engineering
CHAPTER 1 CHAPTER 1
Power Delivery SystemsPower Delivery Systems
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SUBSYSTEMS
GenerationTransmissionSubtransmissionDistribution
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Billions of Dollars
Generation -- 40%Transmission -- 20%Distribution -- 20%
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MISSION
Reach every customerMeet demands of customersSupply reliable powerProvide fluctuation free voltage Provide power with low harmonicsKeep cost low
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Hierarchical Structure
Source: Willis
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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
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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
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Distribution Service Transformer
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Service Transformer Schematic
Source: Gonen
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Reliability Statistics
Source: Willis
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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
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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.
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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
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Dendrillic Configuration
Source: Willis
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Components of Distribution System (Primary side)
Primary trunkMain branches
– Trunk and main branches are usually three-phase
Switches– Normally Closed (NC)– Normally Open (NO)– NO switches are closed during emergencies
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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)
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Secondary System
Close to customers at utilization voltage
RadialFeeds 1 to 12 customers (4 to 6
is more common)
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Distribution Secondary
Source: Willis
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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