Transcript Lecture 1 Slides

EECE 887 Distribution
System Engineering
CHAPTER 1
Power Delivery Systems
SUBSYSTEMS
 Generation
 Transmission
 Subtransmission
 Distribution
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Billions of Dollars
 Generation
-- 40%
 Transmission -- 20%
 Distribution -- 20%
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MISSION
 Reach
every customer
 Meet demands of customers
 Supply reliable power
 Provide fluctuation free voltage
 Provide power with low
harmonics
 Keep 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
trunk
 Main 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
 Radial
 Feeds 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
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