Transcript Electrical Power Generation, Transmission, Storage and Utilization

Electrical Power Generation,
Transmission, Storage and
Utilization
Ray Findlay
IEEE 2002 President
McMaster University, Canada
[email protected]
Robert K.Green, President &
CEO of UtiliCorp United
• “The utility of the future is multinational,
carries its expertise into emerging parallel
businesses, has the flexibility and
willingness to unbundle, adapts readily to
new structures and concepts, goes beyond
its traditional borders to grow, and is an
expert manager of risk.”
What’s in the Future?
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Global power
Privatization
Consolidation
Deregulation
Free market competition
Emphasis on capital, investment strategy
and economics, including cost reduction
Technical Requirements
• Generation: need the lowest cost generation
available to meet demand
There are many factors involved in this process,
complicated, not only by technical
considerations, but also by political
considerations:
Environmental considerations
Maintenance and operating costs
Inefficiencies as a result of transmission
Regulatory issues
Some Elements of the Competitive
Power Market
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Energy network owners - transmission
Energy traders
Energy brokers
Mechanisms for exchange
Wholesale energy pricing
Cost of energy trading
Energy service providers - distribution
Retail operations - supply
Marketing services
Challenges
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Aging infrastructure
Maintenance & scheduling
Power Quality & harmonic distortion
Advances in machine & drive design
Reducing transmission loss
System complexity
Networked generation distribution
Business VS engineering decision-making
Educational issues
Opportunities
• Generation asset management
• Efforts to optimize utilization of generation
facilities according to market demand
• Incentive to increase efficiencies of power plants
and systems
• Incentive to rationalize maintenance schedules to
minimize downtime
• Improvement of communications among
suppliers, and of monitoring systems
Transmission/Network Grids, A Problem
• Unbundling the transmission grid from both the
generation and delivery creates a problem - by
definition it must be a monopoly.
• Need to ensure open access
• Need for regulation and oversight
• Need for maintenance & development of more
capability as required
• Danger of fragmentation, congestion, tariffs,
scheduling difficulties, etc.
The Retail Environment
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Role of the retailer
One, two, how many bills?
Wholesale versus retail
Large customers versus small customers
Multiple service opportunities: gas,
electricity, water, financial services (credit)
• Methods of pricing for retail delivery
– fixed term pricing
– spot market pricing
– regulated, capped or open access pricing
Control
• With large, multi-connected systems inter-tying
substantial areas of the globe, communication
and control become problems
• Dedicated communication lines
• Internet operation and control
• DC generation/conversion transmission versus
AC generation and transmission
CoGeneration
• Issue of small plants
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Methane
Wind power
Solar power
Tidal power
• Interconnections as a virtual plant
• Control issues
• Specialized components
Power Quality
• Harmonics
• Distortion: power electronic loads, adjustable
speed drives & switch-mode power supplies
• Electromagnetic compatibility
• Component magnetics: machines, transformers,
ACSR, etc.
• Power factor: displacement power factor versus
true power factor
Power Factor
Displacement power factor:
PFd = Cos (/VfIf)
True power factor:
PFt = P/(VrmsIrms)
For 100% THD on current, the maximum true
power factor will be about 0.71
Measuring Power Quality
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Total harmonic distortion Irms/I1
True power factor
Communications influence Gw2Ii2/Irms
Crest factor Vpeak/Vrms
• There are several other special purpose
power quality indices.
Harmonic Sources
• Saturable devices include electrical machines,
transformers, some transmission conductors, and
fluorescent lights with magnetic ballasting
• Power electronic (switching) loads include switch-mode
power supplies, PWM converters, voltage source
converters, fluorescent lighting with electronic
ballasting, computers, etc.
• Although not strictly a source, a resonant system can
exacerbate harmonics - systems containing both
capacitance and inductance. An example is an inductive
load with power factor correction.
Voltage Sags in a Multisource
Environment
• Motor starting, transformer energizing,
faults and load switching can all lead to
voltage sag.
• Normal clearing time for a fault is 2 or 3
cycles
• Clearing for a motor start can take 10 cycles
• For a load switch/transformer energize, it
can take 25 - 50 cycles
Voltage Sag Mitigation
Strategies
• Reduce the number of faults. This can be
accomplished by upgrading equipment
• Improve the system. Loads susceptible to faults
should be multi-sourced. Use high-impedance
grounding with )Y transformers to reduce the
effects of a single phase to ground fault
• Interface between system and load - installed
additional equipment. Dynamic voltage restorer.
• Improve the load equipment
Power Acceptability
• To ascertain power acceptability we can
use power acceptability curves that
measure the sensitivity of the load against
voltage sags or over-voltages. The curves
are logarithmic for time duration to
recovery against change in voltage.
• Rectifier loads are particularly sensitive
to voltage sags
DeRegulation & Generators
• Particular utilities have standard requirements (called
grid codes) for generators before the generator can
connect to the grid.
• However, between utilities there is, as yet, no
consistency among the grid codes used.
• Once requirements in a utility are established they may
be historical and may revolve around the weakest link in
the utility system.
• This may cause problems for some units that may be
required to conform to the weakest link grid codes.
(Extreme frequency deviations, extreme VAR limits,
etc.)
Resulting Problems
• Result is inconsistent standards in delivery
• May result in more expensive units to meet the codes
• In some areas of operation can lead to extreme
anomalies in operation, for example may never
operate in the leading PF range.
• Difficulties in matching overall system requirements
to generator capacity.
• Although the machines may be capable of producing
the power they may be penalized for not operating in
the extremes - hence leading to more expensive
power.
New Technologies
• To develop a rational maintenance schedule we need to
make us of new technologies, for example monitoring
partial discharges of the stator windings of generators.
• Some insulation materials have predictable partial
discharge behaviour which may make it possible to
determine the state of the winding, as well as the
specific aging mechanism.
• By keeping a record of PD activity it is then possible to
develop a rational maintenance schedule.
• This type of monitoring can be set up as an intelligent
system to warn of impending winding failure.
Partial Discharge Tests
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Pulse peak magnitude
Pulse polarity
Repetition rate
Phase location
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Plotted results:
Pulse height analysis
Pulse phase analysis
Trends
From these plots we can determine:
• The overall degradation of the stator winding
• The partial discharge activity: the maximum
magnitude of pulses with a particular repetition
rate
• The trend of partial discharge activity which
yields the progression of insulation aging
• Analysis of the pulse phase plot can pinpoint the
location of the activity - slot or endwinding
• Pulse patterns reveal the nature of the partial
discharge activity, including the predominant
sources.
Winding Deterioration Factors
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Voltage switches and variations
Operating conditions
Fluctuations in load
Mean operating voltage level
Winding temperature
Humidity
Aging
Winding displacement in slot - fit
Web-Based Monitoring and Control
• The web presents an opportunity for system automation
and control.
• For large deregulated systems information transfer
plays a large part in determining success.
• This gives rise to the concept of an on-line System
Control and Data Acquisition System (SCADA) .
• When combined with an interactive energy
management system, we have an effective operating
system over long distances and between systems.
• To take advantage of this possibility will require
substantive changes in individual SCADAs, as well as a
very cooperative approach to selecting standards
An ACSR Conductor
current direction
longitudinal flux
current in steel core
current in aluminum wires
circular fulx
54 aluminum conductors in three layers
19 steel conductors, two layers over a single wire
COOLTEMP
M
HT
RC
EM
Predicts conductor behaviour over the life time by
introducing statistical distribution of system loads,
ambient temperature, and rise of conductor surface
over ambient
Conductor dimensions
Complex Layer’s
Current
COOLTEMP
Electromagnetic
Model
Heat transfer
Model
Mag. Field Strength
Complex
Permeability
Data
Radial Conduction
Model
Layer’s
temperature
Pretensioning
variables
Stringing variables
Mechanical Model
Running-out variables
Annealing
Avg.
aluminium
temp.
Creep
Avg.steel
temp.
Steel Stress
current
Sag
Aluminium
Stress
Horizontal Tension
I total
Loop inductance
I total
j(I +I +I + koI )k ln[Do/(Do-d)]
s i m o
j(I +I +I + kiI )k ln[(Do-d)/Dm]
s i m o
j(Is+Ii +koI
m )k ln[Dm/(Dm-d)]
j(Is+Ii +kiI
m)k ln[(Dm-d)/Di]
j(I s+koIi )k ln[Di/(Di-d)]
j(I +kiI )k ln[(Di-d)/Ds]
s i
Cicular inductances
Resistances
Longitudinal inductances
d
Electromagnetic
Model