1A-Power System Overview.ppt

Power Systems
Overview
SPE Intern Training
2014
Prepared by Daniel L. Kelley, P.E.

Power System
 Consists of four main parts
 Generation
 Transmission
 Distribution
 Load
 Objective: provide electric power at a reasonable cost

Power System One Line
 The power system is a large
network of multiple
generation stations,
transmission lines,
distribution lines, and
substations. In North
America the overall system is
often called the bulk electric
system (BES).
 There are many private and
public entities that own and
operate pieces of the power
system.
 Entities in Colorado include:
Xcel, WAPA, PRPA, Tri-
State, IREA, Holy Cross,
YVEA, Black Hills, and
others.

Typical System Operating
Characteristics
 60 Hz Frequency (50 Hz in Europe)
 Transmission voltages: 69 kV and above
 69 kV – 138 kV is sometimes called sub transmission
 Typical transmission voltages: 69, 115, 138, 230, 345, 500,
765 kV; these are often called high voltage (HV)
 Voltages above 765 kV are called extra high voltage (EHV)
 Distribution voltages are below 69 kV
 Typical distribution voltages: 44, 25, 13.8, 12.7, 7.6, 2.4 kV
 Distribution voltages can be specifically chosen for each
location
 Voltages below 600 V are called low voltage (LV)

Electric Generation
-Multiple Methods-
 Dispatch-able
 Coal
 Nuclear
 Hydro
 Natural Gas
 Bio Fuels
 Geo Thermal
 Not Dispatch-able
 Wind
 Solar
 Ocean Waves
Electric energy may be the only commodity created and consumed instantaneously. It is
important to have capability to feed loads on demand.
Definition of dispatch: to send (someone or something) quickly to a particular place for a
particular purpose (Merriam-Webster online dictionary)

Electric Generation in General
 Fuel is consumed to create steam
which spins a turbine. The spinning
turbine creates three phase power.
 Inverters are used in cases of wind
and solar to create a 60 Hz output
onto the electric grid. Solar cells
create DC power and wind creates a
varying frequency of power.
 Power is produced at a low voltage.
This power passes through a ‘step
up’ transformer connecting to
transmission systems.

Transmission Lines
Transmission lines can be overhead or
underground
 T-Line Considerations:
 Property permitting, easement or right of way
 Current capacity, EMF, Skin effect, noise
 Vegetation
 Public Safety
 Lightning protection
 Access for construction/maintenance
 Cost
 Environmental compliance
 Transmission line cost: $300 thousand - $2 million dollars per
mile to build overhead; $1.5-$42 million dollars per mile to
build underground
 Higher voltages of transmission lines help to reduce electric
losses between the generation and loads.

Distribution Lines
Distribution lines can be overhead or
underground
 Distribution Line Considerations:
 Property permitting, easement or right of way
 Current capacity, EMF, Skin effect, noise
 Vegetation
 Public Safety
 Lightning protection
 Access for construction/maintenance
 Cost
 Environmental compliance
 Distribution line cost: $50 - $300 thousand dollars per mile to
build overhead; $200 thousand - $1.5 million dollars per mile to
build underground
 Distribution lines in general connect between the transmission
system and the end use customer.

Transmission and Distribution Line
Circuit Model
 In many lines the resistive
portion of the model is
small and may be
neglected.
 Inductive and Capacitive
elements usually given in a
per mile unit.

Substations
 Can be considered the ‘nodes’ of the electric grid
and serve as an interconnection point between
lines, loads, and generation
 The interconnecting point in reality is a bus within
the substation
 Contain transformers to step voltage up or down
 Contain breakers and switches for fault
interruption and operation of the system
 Contain equipment for monitor and control of the
electric system
 The considerations for transmission and
distribution lines also apply to substations
 Additional considerations include power flow
capacity and system protection
 Substations will often cost $1 - $50 million dollars
or more depending on voltage and size
 Typical cost for a 115-230 kV auto transformer is
$2 - $3 million dollars; transformers are the bulk of
expense within a substation

Loads
 Main Considerations:
 Utility fault current
 Breakers and fault protection schemes must be able to
interrupt fault current from the utility connection.
 Power quality
 Power factor correction
 Harmonics
 Transients from switching

Legal Requirements for Utilities
 Public Safety
 National Electric Safety Code (NESC)
 National Electric Code (NEC)
 Regulation
 Federal Energy Regulatory Commission (FERC)
 Regulates financial aspects of the energy industry
 North American Electric Reliability Corporation (NERC)
 Develops and enforces reliability standards for the bulk electric system (BES)
 State public utility commission (PUC)
 Regulates cost of energy for consumer. Utilities must obtain permission to
increase rates before building new infrastructure.
 Industry best practice
 IEEE, ANSI, and company standards include best practice information
for application, implementation, and testing of almost any kind of
equipment or system used in the power system. These standards are a
good place to look first when addressing any topic for a new engineer.

Sub Topics of Power Systems to
Consider
 System protection for short circuits
 Physical and Cyber security of assets
 System stability and planning
 System Operation and Maintenance
 Equipment design
 Equipment, System, and Substation Control
 New technologies (e. g. wireless power
transmission)

General List of Industry Jobs
 System Planning
 Engineering and Design
 Operation
 Maintenance
 Compliance (FERC/NERC)
 System Protection
 System control and data acquisition (SCADA)
 Energy management systems (EMS)
 Energy Trading
 Permitting, Siting and Land Rights, and Public Relations
 Construction
 Finance/Legal

1A-Power System Overview.ppt

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