WESTERN INTERCONNECTION TRANSMISSION · PDF fileDynamic Line Rating Systems ... Balancing...

1WESTERN INTERCONNECTION TRANSMISSION TECHNOLGOY FORUM

1

The Latest in the MIT “Future of…” Studies

Recognizing the growing importance of energy issues

and MIT’s role as an honest broker, MIT faculty have

undertaken a series of in-depth multidisciplinary studies.

Previous studies have focused on energy supply

technologies; our focus is on energy delivery – the

electric grid. Also, unlike other “Future of…” studies, we

do not focus on carbon constraints.

WESTERN INTERCONNECTION TRANSMISSION TECHNOLGOY FORUM 2

http://web.mit.edu/mitei/research/studies/report-natural-gas.pdf

http://web.mit.edu/mitei/research/studies/report-natural-gas.pdf

New Technologies Offer Great Opportunities

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Control Centers:

Improved System State Estimation Phase Angle Monitoring/Alarms Improved System Simulation Models Oscillation Detection New System Control Approaches

Transmission and Substations:

Phasor Measurement Units (PMUs) Flexible AC Transmission Systems (FACTS) New Sensor Technologies High Voltage DC Lines Superconducting Lines Fault Current Limiters Dynamic Line Rating Systems Energy Storage

Distribution and Customers:

Distribution Management Systems Outage Management Systems Volt/VAR Optimization Conservation Voltage Reduction Automated Fault Detection, Isolation, &

Restoration Advanced Metering Systems Microgrids

WESTERN INTERCONNECTION TRANSMISSION TECHNOLGOY FORUM

Outline

Some system trends

Transmission line technologies

Solid state control technologies

PMU and synchrophasor systems

Balancing area topologies

Renewable (wind) integration issues


The U.S. Grid Performs Well

Losses have fallen over time, are in line with other nations’

Reliability also seems in line with other developed countries

Performance data are very weak


U.S. Transmission and Distribution Losses 1926-2009

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

1926

1931

1936

1941

1946

1951

1956

1961

1966

1971

1976

1981

1986

1991

1996

2001

2006

T&

D L

osse

s (

% o

f To

tal G

en

era

tio

n)

Year

Transmission Investment in New England

Source: ISO New England Transmission Project List, through October 2013v Update.


Payments to Maintain Reliability

Reliability Agreements ended in June 2010

Source: ISO New England Transmission Project List, through October 2013 Update.


$0

$50

$100

$150

$200

$250

$300

$350

$400

2005 2006 2007 2008 2009 2010 2011 2012

Dollars in millions

Regional Total Reliability Payments

Reliability Agreements NCPC

Congestion Costs

Source: ISO New England Transmission Project List, through October 2013 Update.


0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

$0

$50

$100

$150

$200

$250

$300

2005 2006 2007 2008 2009 2010 2011 2012

Dollars in millions

Congestion Costs Congestion as % of Energy Market

“Peakier” Load Duration Curves Raise Cost

Air conditioning, shift away from industrial load have reduced capacity utilization.

Electric vehicles charged in late pm could make this worse.

Moving charging, other loads off peak could flatten curve and lower cost.

But most current demand response programs focus on emergencies, not load leveling.

Dynamic pricing would help smooth demand peakiness.


Three Constraints of Transmission Lines


Renewables’ Effect on System Inertia

System inertia necessary to ride through

transients

Inertia provided by large rotating masses of

conventional generators

Solar provides no system inertia

Wind provides inertia but no recovery


AC Lines

Three conductor bundles (3 phases)

Length limited by stability margin

Compensating devices required to maintain

voltage stability

AC cables severely length limited

Charging currents, resonance


High Temperature Superconducting Cable

Liquid nitrogen: 65 K (–208o C)

Demonstrated by LIPA in 2008:

138 kV ac,

574 MVA

600 m

Increase capacity of existing cables

Possible fault current limiter

Allows increased line loading


Installation of the First Phase Conductor


From Maguire et. al., “Installation and Testing Results of Long Island Transmission Level HTS Cable,” IEEE Trans. Applied Superconductivity, vol. 10, no. 3, June 2000.

Solid State Transformer Concept


Examples of Static VAR Compensators


Current injection orthogonal to

line voltage

Voltage injection orthogonal to

line current

DC vs. AC Transmission

DC lines not limited by stability considerations

Cost and losses are issues

Cost tradeoff a function of length

Converter vs. line losses

DC attractive for renewables located far from

load centers


HVDC

Requires complex and expensive converter

terminals.

Excellent for long distance transmission.

Line costs/losses less than AC

For 800 mile/6000 MW line:

765 kV ac twice as expensive as +/- 800 kV dc

Ac losses twice those of dc

Comparable cost and losses for 200 mile line


HVDC Converter Structures


Current Source Converter Terminal(CSC)

Voltage Source Converter Terminal(VSC)

AC DC

Voltage Source Converter

Greater control flexibility

Aids stability, integration of remote renewables

Permits use of solid dielectric cables

Attractive for interconnects, not generator leads

Higher losses than CSC

Currently limited power rating


VSC HVDC (cont’d)

Doesn’t require strong ac bus for

commutation.

Ideal for long cables

Underground or under water


ABB HVDC Breaker


WHAT ABOUT RENEWABLES?


But New Transmission For Renewables

Will Not Necessarily:

Reduce congestion

or

Increase reliability

24WESTERN INTERCONNECTION TRANSMISSION TECHNOLGOY

FORUM

Renewables Require New Transmission

The Challenge of Ramping Wind

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Wind output more variable than load, imperfectly predictable.

Work on better forecasting in progress.

System operators studying, implementing other changes to facilitate more wind.

Few incentives exist for flexibility today.

BPA Total Wind Generation 12/3/2009 – 12/10/2009

WESTERN INTERCONNECTION TRANSMISSION TECHNOLGOY FORUM

Another Ramping Example


Larger Balancing Areas

Real Time Contingency Analysis (RTCA)

should be expanded beyond boundaries of

BAs. Need wide area system model.

Standardization of models, e.g.,

nomenclature.

Minimize ramping requirements for wind.


USING AMI + PRICING TO LEVEL LOAD

Dynamic pricing + automated response can shift

demand, but more research on consumer behavior is

needed.

Substantial ARRA-supported, state-mandated AMI

investments provide a very important learning

opportunity.


Introduction to Synchrophasors

A network of phasor measurement units (PMUs)

situated at strategic locations throughout the

system. The data collected by the individual

PMUs are synchronized using a GPS time

stamp, making visible parameters such as phase

relationships.


How Interconnected? The 2008 Florida Blackout


PMU Data Could Warn of Blackouts

• PMUs give frequent, GPS-synchronized measures of current, voltage,

and phase angle at their locations.

• Ex-post analysis of 2003 blackout:


Benefits of a Synchrophasor Network

System diagnostics and real-time analysis

Increased transmission line capacity

Operation closer to stability limits

Determination of more accurate system

model parameters

Detection of anomalous system conditions

E.g., low frequency oscillations

Many others yet to be discovered


Synchrophasor Integration Issues

Prior to SGIG few applications or standards, and

interoperability difficult.

Data quality

Communication protocols

Security concerns

Post SGIG initiatives addressing these issues.

NASPI

Numerous IEEE standards

Communication, calibration, hardware requirements, etc.


PMU Application Challenges

Baselining – what is “normal” operation?

Turning data into actionable information

Limited application software

Communication latency in wide-area

applications

Cost/authority/maintenance

Security and proprietary concerns

Training

Employing AI to determine/take actions


Recommendations from Chapter 2

R&D efforts should be undertaken to develop:

1) The analysis tools necessary to generate

actionable information from data acquired from

PMUs, and

2) The control schemes necessary to make use of

this information by realizing the complementary

potential of PMUs, FACTS, and other hardware

devices.


Recommendations from Chapter 2 (cont’d)

NERC should continue to encourage relevant

entities to participate in PMU data-sharing

efforts necessary for the effective

development and use of PMUs and wide-area

measurement systems


“Power Outages Caused by Squirrels”


NYT Headline Sunday Sept. 1, 2013

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