Transcript The US Electrical Grid - Montana State University

The U.S. Electrical Grid
Design
Function
Issues
Electricity Grid:
•The
‘traditional model’ of electric power
generation and delivery :
•Based on construction of large, centrally
located power plants
•Power
•Hubs
plants located on hubs
near major electrical load centers
•Ultimate
Grid Purpose = Deliver power
from generation source to users.
Some Factors that influence
Power Plant siting
•
Location of load centers –vs- Availability of fuel
resources
•
Need for a cooling water source
•
•
Fundamental for operation of conventional fossil fuel plants
Environmental considerations
•
•
•
Larger influence than ever
Global Climate Change, Endangered Species Act,
Wilderness areas, Ocean Health, etc.
Carbon Footprint Concerns
More power plant siting factors
•
•
Geographical/Economic
considerations

Plant located close to coal mines to minimize the cost of
shipping coal… (A Local Issue?!)

Hydro plants in dams at water source, may be far from
cities
Social, political considerations

View-shed, Public demand/acceptance

Political clout and will.

Special Interests Pro/Con
Grid infrastructure

Transmission systems

High-voltage to minimize electrical losses

138 kV to 765 kV, most A/C

Carry electricity from the power plants

Transmit from source to user, a few miles to thousands of miles

Electrical Substations

Substation transformers "step down" the transmission
voltages

Switchgear and circuit breakers to protect the
transformers and the transmission system from
electrical failures on the distribution lines.

Distribution systems

Lower-voltage

Draw electricity from the transmission lines

More Transformers located along the
distribution lines further step down the
voltage to 120 V or 240 V for household use.

Distribute electricity to individual
customers.

Circuit breakers located on distribution lines
isolate electrical problems (e.g. short circuits
caused by downed power lines).
Grid Architecture and Function

The transmission system is central trunk
of the electricity grid.

Thousands of distribution systems branch
off from this central trunk

Distribution systems fork and diverge into
tens of thousands of feeder lines reaching
into homes, buildings, and industries.

Power flow to the distribution systems
determined by the power flow through
the transmission systems.
Grid Architecture and Function

Most references to “power grid" really mean the
transmission system.

Grid nomenclature accurate: Transmission lines
run from power plants to load centers and from
transmission line to transmission line

Redundant system helps ensure smooth flow of
power

If a transmission line is taken out of service in one
part of the power grid, the power can usually be
rerouted through other power lines to continue
delivering power to customers.
Grid Architecture and Function

Grid permits power from many power plants to be "pooled" in
the transmission system

Each distribution system draws from this pool

Networked system helps achieve a high reliability for power
delivery because any one power plant that shuts down will
only constitute a fraction of the power being delivered by the
grid.

Networked system permits a diversity of power sources

Coal

Nuclear

Natural gas

Oil

Renewable energy sources
Energy Flow
U.S. Power Grids

No "national power grid" in the United
States: Actually there are 3 main power
grids:
•
The Eastern Interconnected System, or the
Eastern Interconnect
•
The Western Interconnected System, or the
Western Interconnect
•
The Texas Interconnected System, or the
Texas Interconnect.
The 10 North American Electric Reliability
Council (NERC) regions
1.
ECAR — East Central Area Reliability Coordination Agreement
2.
ERCOT — Electric Reliability Council of Texas
3.
FRCC — Florida Reliability Coordinating Council
4.
MAAC — Mid-Atlantic Area Council
5.
MAIN — Mid-America Interconnected Network
6.
MAPP — Mid-Continent Area Power Pool
7.
NPCC — Northeast Power Coordinating Council
8.
SERC — Southeastern Electric Reliability Council
9.
SPP — Southwest Power Pool
10.
WSCC — Western Systems Coordinating Council
U.S. Power Grid Operations
Controlling the Grid

Electricity is generated as it is used.

There is very little ability to store electricity.

Because of this instantaneous nature, the
electric power system must constantly be
adjusted to ensure that the generation of power
matches the consumption of power.

On continental U.S. power grids, roughly 150
Control Area Operators serve this function by
using computerized control centers to dispatch
generators as needed.
Grid Operation

Responsibility for electric grids has traditionally rested with
electric utilities

Control Area Operators run the grid within their control areas

Each utility has responsibility for the operation of the electrical
grid within its service area
Grid Operation, cont.

Some states have moved to pass the control of the
grids to independent system operators, or ISOs.
 Utility control of the grid has been viewed as a
conflict of interest.
 California ISO controls the transmission grid for
California.
 ISOs also exist in Texas and New England.

Ownership of the transmission and distribution
systems may be retained by the utilities or be passed
off to independent transmission companies
("TransCos"), in which case the utility effectively
becomes a distribution company ("DisCo").
Electric Control Area Operators —
Continental United States, 1998.
U.S. Grid Interconnections

The Eastern and Western Interconnects
have limited interconnections with each
other

Texas Interconnect is only linked with the
others via direct current lines.

Both the Western and Texas Interconnects
are linked with Mexico

Eastern and Western Interconnects are
strongly interconnected with Canada.

All electric utilities in the mainland
United States are connected with at least
one other utility via these power grids.
Hawaii and Alaska grid systems

Much different than those on the U.S.
mainland.

Alaska grid system connects only
Anchorage, Fairbanks, and the Kenai
Peninsula

The rest of AK depends on small diesel
generators, or minigrids

Hawaii depends on minigrids to serve
each island's inhabitants.
Electrical generation sources
divided into three categories
• Baseload power plants, which are run all the time to
meet minimum power needs
Nuclear plants are nearly always operated as baseload plants because they are most stable at full power.
•
•
Peaking power plants, which are run only to meet the
power needs at maximum load (known as "peak load“
or “cyclilng”)
•
•
Peaking plants are generally the most expensive plants to operate. In many cases, these are small, older coal- or oil-fired
plants, although gas turbines can also be used as peaking plants.
Intermediate power plants, which fall between the
two and are used to meet intermediate power loads.

Intermediate plants are well-suited to changing power loads (called "load following"); gas turbines can be used as
intermediate plants.

E.G. Basin Creek 50 MW NG Plant near Butte, Dave Gates Generating Station east of Anaconda
Existing Grid Designed Around
Large Centralized Power Plants

Premise of the Design of our electric power industry:



Large, centralized power plants could achieve economies of scale that
would make them the least expensive source of electricity.
This principle not necessarily still accepted

Small, efficient gas turbines can produce inexpensive electricity on a
relatively small scale.

Distributed generation from renewables may play increased role
Siting, permitting, and construction delays and costs for large-scale
power plants have made them less competitive.
A little history:
1980’s Power Crunch

Around 1985, electric utilities began to anticipate increased
competition

Companies looked to cut costs and avoid debt that would make them
uncompetitive

Large power plants involving investments of billions of dollars viewed
as unacceptable risks

Utilities avoided new power plant investments

Demand-side management programs (programs to encourage energy
efficiency and load reduction) became popular as one alternative to
power plant construction.

By the time wholesale electricity competition began in the United
States in 1996, utility investment in power plants had slowed
considerably.

Wholesale competition changed the way utilities operate

With restructuring imminent, electric utilities also reduced their
investments in demand-side management because these investments
seemed counter to their goals.
Electric Restructuring

Electric restructuring; California and several other states.

California 1996

Montana Deregulation in 1997

Some states with low rates were reluctant to pursue restructuring.

Efforts to establish restructuring on a federal level were not successful.

Uncertainty in the industry dragged on, further discouraging utility investments.

Load growths in the range of 3% per year also created little incentive to build new
power plants

In the Northeast, the option of importing inexpensive hydropower from Canada was
a simple and inexpensive solution to growing power needs.

Lack of generation growth led to tight electricity supplies in the United States,
particularly in California, circa 2000.
A drop in hydropower production in the Pacific Northwest contributed to these tight
electricity supplies.


NEW investments in Electrical Generation now occurring.

Wind, Solar, taking the lead
Power Quality and Reliability
Issues

Power quality is a concern for today's power grid
and the loads it serves.

Computer equipment, in particular, is sensitive to
power quality problems

High power quality is important to many
commercial and industrial firms and the average
homeowner.

Renewables do not always provide best power
quality due to fluctuating nature
Some Power Quality Problems
•
Decaying oscillatory voltages — The voltage deviation gradually dampens,
like a ringing bell. This is caused by banks of capacitors being switched in by
the utility.
•
Commutation notches — These appear as notches taken out of the voltage
wave. They are caused by momentary short circuits in the circuitry that
generates the wave.
•
Harmonic voltage waveform distortions — These occur when voltage waves
of a different frequency—some multiple of the standard frequency of 60
cycles per second—are present to such an extent that they distort the shape
of the voltage waveform.
•
Harmonic voltages — These can also be present at very high frequencies to
the extent that they cause equipment to overheat and interfere with the
performance of sensitive electronic equipment.
Power
Quality

The most severe power quality problem is voltage surge
caused by a lightning strike.

Other power quality problems include:
•
Voltage sags and swells — The amplitude of the wave gets momentarily smaller or
larger because of large electrical loads such as motors switching on and off. Voltage
sags are the most commonly experienced power quality problem among electronic
and computer equipment users.
•
Impulse events —glitches, spikes, or transients; voltage deviates from the curve for
a millisecond or two (much shorter than the time for the wave to complete a cycle).
Impulse events can be isolated or can occur repeatedly and may or may not have a
pattern.
Power Quality

Other power quality problems may also be considered reliability problems
because they occur when the transmission system is not capable of meeting the
load on the system.
•
Brownouts are a persistent lowering of system voltage caused by too many
electrical loads on the transmission line.
•
Blackouts = a complete loss of power.
•
•
Unanticipated blackouts are caused by equipment failures, a downed power line, a
blown transformer, or a failed relay circuit.
•
Although normally limited by design to a small geographic area, blackouts have been
known to affect wide regions of the United States.
"Rolling" blackouts
•
intentionally imposed upon a transmission grid when the loads exceed the generation
capabilities. By blacking out a small sector of the grid for a short time, some of the load
on the grid is removed, allowing the grid to continue serving the rest of the customers.
To spread the burden among customers, the sector that is blacked out is changed every
15 minutes or so—and hence, the blackouts "roll" through the grid's service area.
Possible Future Power Solutions
METHOD 1: Use the traditional utility paradigm:


Build more power plants, update existing plants
Beef up the transmission system


Create legislation to encourage investment in both
approaches


allow power to be shipped to where it is needed.
(these actions are moving forward in many states)
These investments could be encouraged via a National
Energy Plan.
Possible Future Power Solutions
METHOD 2: Incorporate more Distributed energy (DE) resources

DE investments bring power solutions directly to user locations

Reduced need for long-distance transmission of power.

Reduce reliance on transmission and distribution systems by providing
customer-specific solutions at the point of need

Each DE system represents a relatively small investment that can
generally be installed within a short timeframe.

DE can lessen the financial risk of investment and can be more
responsive to changing load growth.
*Combinations of these two major themes are likely
*All Solutions benefit from efficiency increases
Other Power Grid Concepts

There are a variety of approaches to improving the operation
of the electricity grid, some of which involve replacing it
entirely in specific locales. All of these approaches are
motivated by power reliability and/or quality concerns, and all
incorporate Distributed Energy.
•
Minigrids
•
Power Parks
•
DC Microgrids
•
Flexible Alternating Current Transmission Systems
•
Electrical Load as a Reliability Resource

SMART GRID
Smart Grid
&
Integration
of
Renewable Energy Resources
(Portions adapted from a presentation by
SmartGrid IIT, Johdpur, India)
What is Smart Grid ?

The Smart Grid is a combination of hardware,
management and reporting software, built atop
an intelligent communications infrastructure.
 In the world of the Smart Grid, consumers and
utility companies alike have tools to manage,
monitor and respond to energy issues.
 The flow of electricity from utility to consumer
becomes a two-way conversation, saving
consumers money, energy, delivering more
transparency in terms of end-user use, and
reducing carbon emissions.
What is Smart Grid ?
Modernization of the electricity delivery system so
that it monitors, protects and automatically
optimizes the operation of its interconnected
elements – from the central and distributed
generator through the high-voltage network and
distribution system, to industrial users and
building automation systems, to energy storage
installations and to end-use consumers and their
thermostats, electric vehicles, appliances and
other household devices.
The Smart Grid in large, sits at the intersection of
Energy, IT and Telecommunication Technologies.
39
Key Elements
of Smart Grid

Transmission Optimization

Demand Side Management

Distribution Optimization

Asset Optimization
SMART GRID
IN
TRANMISSION
41
Technology Integration & Grid Management
Need
for development of Smart Grid having
features like Phasor Measurement Technique
 Wide Area Measurement (WAM)
 Flexible AC Transmission System (FACTS)
 Adoptive Islanding
 Self healing Grids
 Probabilistic and Dynamic Stability Assessment
 Distributed and autonomous Control
42
Sidebar…
A phasor measurement unit (PMU)
or synchrophasor is a device which measures the
electrical waves on an electricity grid, using a common
time source for synchronization. Time synchronization
allows synchronized real-time measurements of multiple
remote measurement points on the grid. In power
engineering, these are also commonly referred to as
synchrophasors and are considered one of the most
important measuring devices in the future of power
systems.[1] A PMU can be a dedicated device, or the
PMU function can be incorporated into a
protective relay or other device.[2]
Benefits of PMU
 Time synchronized sub-second data
 Dynamic behavior observing
 Directly
provides
the
phase
angles
(State Estimation to State Measurement)
 Improve post disturbance assessment
 High data rates and low latency due to
computation
44
SCADA Vs PMU
SCADA = supervisory control and data acquisition
PMU = Phasor Measurement Units
Open
Close
Close
Close
~
V
P
Q
Hz
Several
Seconds
to a
Minute
milli
secs
to sec
KV
MW
MVAR
Hz
Network model
State Estimator
• Traditionally developed for
accommodating old
information technology
regime (Slow
communication, data
without
time stamp)
LD&C_SCADA
• Made possible for all round
development in technologies
45
Overview of Smart Grid
46
Smart Grid in Power Sector
Transmission
•Asset
Management
•HVDC and
UHVAC etc.
Distribution
•Advance
Metering
Infrastructures
System Operations
•Asset
Management etc.
•Self Healing Grids
•WAMS
•Adaptive Islanding
etc.
47
Smart Grid
in
Distribution
Smart Grid in Distribution

Distribution Automization

Demand Optimaization - Selective Load Control

Operation –Islanding of Micro-grids
Distribution Automization/Optimization

Managing Distribution Network Model

Outage management and AMI Integration

DMS & Advanced Switching Applications

Integrated Voltage / VAR Control
Demand Optimization
 Demand
Response – Utility
 Demand
Response – Consumer
 Demand
Response Management System
 In
Home Technology enabling

Demand Optimization
Smart Metering –

Automatic, Time of Use, Consumer Communication & Load Control

Communications : Automated Metering
Infrastructure (AMI) – LAN, WAN, HAN

DRMS (Demand Response Management)

In Home enabling technology

Demand in three category:


Immediate, Deferrable, Storable
Customer aggregation & De-aggregation required for Peak shifting
Demand Optimization: Advanced Web Portal

Energy Usage Information

Utility Communication

Consumer Enrollment in DR programs

In Home Technology- Availability & Purchase , Device Provisioning
Control Center with Service Oriented
Architecture (BUS)

Having
 GIS
(geo-spatial Information Systems),
 AMI,
 SAP (ERP),
 OMS (Outage management System),
 DMS (Distribution Management System),
 EMS (Energy Management System),
 DRMS (Demand Response management System).

Model manager synchronizes GIS data with OMS,
DMS & EMS.
Expectation of Technology & Solution
Partners

To associate and collaborate with Smart Grid players in other parts of globe

Develop local expertise to manufacture and provide support services

Development of CIM

Application Development in India Power Sector Context.
Why Smart Grid?

Integrate isolated technologies : Smart Grid enables better energy management.

Proactive management of electrical network during emergency situations.

Better demand supply / demand response management.

Better power quality

Reduce carbon emissions.

Increasing demand for energy : requires more complex and critical solution with
better energy management
Drivers of Smart Grid
Increasing demand:
 High Aggregate Technical & Non Technical,
Losses:18%-62%
 Ageing assets…transformers, feeders etc.,
 Grid to carry more power: Need for, Reliability and
greater Security
 Billing and collections: Profitability of distribution
companies
 Energy mix: Need for Renewable to reduce carbon
footprint

Implementation leads to …..

Deliver sustainable energy

Increased efficiency

Empower consumers

Improve reliability

Smart Grid
New Technologies for…..

Energy Storage to support a Resilient
Smart Grid
(Comparing & evaluating cost competitiveness of:
Compressed air, pumped hydro, ultra
capacitors, flywheels, battery tech, fuel cells.)

Smart Grid & Electric Vehicle Integration
(How can electric Vehicle optimize the use of
renewable energy resources, improve
efficiency)
Challenges Faced by Smart
Grid

Present Infrastructure is inadequate and requires augmentation to support the
growth of Smart Grids.

Most renewable resources are intermittent and can not be relied on (in its present
form)for secure energy supply

Regulatory Policies to deal with consequences of Smart Grid; like off peak, peak
tariffs and other related matters.

Grid Operation : Monitoring & control
Integration of Renewables
Net Zero – Energy / Water / Waste
 Green Community – Self Sufficient & Reliant
 Judicial Mix of various Technologies and Options for
different use



Use or Supply

Draw or Store

Storage Options
Type of Use

Heating /Cooling

Illumination / Ventilation

Machine Operations

Appliance Powering ( Computers / Printers / Copiers / Faxes)

Domestic Appliances
Integration of Renewables

Choice of Current

AC or DC

AC – DC

DC – AC

DC – DC

Switches and Disconnects

Availability of Domestic DC Appliances - Power Packs

Connectivity to Grid – Size of Plant, Distance to Consumers

Control Strategy and Methodology – availability of software
Some More Resources

http://energy.gov/oe/technology-development/smart-grid

http://www.smartgrid.gov/

http://www.usnews.com/news/energy/slideshows/10cities-adopting-smart-grid-technology