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Interconnected Power SystemsInterconnected Power SystemsInterconnected Power SystemsInterconnected Power Systems

Blackouts and Restoration ExperienceBlackouts and Restoration ExperienceBlackouts and Restoration ExperienceBlackouts and Restoration Experience

By Professor Saifur Rahman

CIGRE Conference on Electrical Power Engineering

Amman, JordanAmman, Jordan

3 September 20073 September 2007

Advanced Research InstituteVirginia Polytechnic Inst & State University, U.S.A.

www.ari.vt.edu

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Outline

� Interconnections

� HVDC: an interconnection technology

� Examples of large interconnected systems

� European power systems

� United States power grids

� Mediterranean Ring Project

� Blackouts and Outage Management

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World electric power generation

� By 2030, electric power consumption is expected to double.

Source: Energy Information Administration/ International Energy Outlook 2007

Expansion of electric power grid

� Interconnections are designed to permit the transfer of electrical

energy from one part of the network to another.

� Interconnecting separated grids will:

� allow diversity in power supply options

� offer more choices and competitive pricing

� improve reliability of electric service

� Due to the fast growth in electric power demand, rapid expansion of

the electric power grid will be necessary.

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Asynchronous connection in European countries

Large interconnected AC networks in Europe and surrounding areas

� One grid in Western Europe

� One in Eastern Europe

� One in the Nordic countries

� One on each island

Source: W. Breuer et al, “Role of HVDC and FACTS in future power systems”, in Proc. The CEPSI 2004,

Shanghai.

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Interconnections of various AC networks

Limitations of an AC tie between two AC networks

� Connecting two systems with different AC frequencies (50/60Hz)

� Frequency variation between two networks (± 0.1 Hz)

� Voltage instability

� Oscillation instability

� Blackout risks due to cascading effects

HVDC can provide links between two power grids.

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HVDC

The HVDC (High Voltage Direct Current) is used to:

� transmit electricity over long distances

� interconnect separate power systems

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HVDC: how it works?

In a HVDC system,

• Electricity taken from one point in a 3-phase AC network,

• Converted to DC in a converter station

• Transmitted to the receiving point by an overhead line or cable

• Converted back to AC in another converter station

• Injected into the receiving AC network.

Typically, an HVDC transmission has a rated power of more than 100 MW and many are in the 1,000 - 3,000 MW range.

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HVDC station layout

Source: ABB (www.abb.com/cawp/GAD02181/4CDB350022CD837FC1256DB20029FEAD.aspx)

This is a typical layout of a HVDC converter station for 500 - 600 MW

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Advantages of HVDC

HVDC allows a number of systems to operate asynchronously.

HVDC will

� Contain any major disturbance

� Provide simpler and more controllable systems

� Provide connection for two systems with different standards

� Minimize effects of blackouts and cascading failures

� Maintains local political & technical control

• think it works.

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Source: ABB – HVDC Classic Reference List: Thyristor valve projects and converter station upgrades

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Current and planned HVDC links in Europe

Source: ABB (www.abb.si/cawp/GAD02181/C1256D71001E0037C1256C13002FD1C6.aspx)

The Scandinavia - Northern Europe interconnections

Estlink (350MW) Estonia-Finland, 2006

Fenno-Skan (500MW)Finland-Sweden, 1989

Troll Offshore (84MW)HVDC Light, 2005

Valhall offshore (78MW)HVDC Light, 2009

English Channel (160MW)UK-France, 1961

Sapei-Italy (1000 MW)2008-09

Sardinia-Italy (200MW)1967

Italy-Greece (500MW)2001

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The NorNed HVDC Link

The 580 km-long NorNed link will be the longest underwater

high voltage cable in the world, connecting Norway and

The Netherlands.

Main Data

Commissioning year: 2007

Power rating: 700 MW

AC Voltage: 300kV (Feda), 400kV (Eemshaven)

DC Voltage: 450 kV

Length: 2x580 km

Project development costs: EUR 495 million

Main reason for HVDC: Length of sea cable and non

synchronous AC systems

Source: ABB (www.abb.com/cawp/gad02181/09264cb2d17c4cc6c1256d8800402659.aspx)

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Land terminal @ Eemshaven, The Netherlands

Source: ABB - the NorNed HVDC project

Eemshaven converter station, The Netherlands, in Mar 2007

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Land terminal @ Feda, Norway

Source: ABB - the NorNed HVDC project

Feda converter station, Norway, in March 2007

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Converter stations @ Skagerrak

Source: ABB - the Skagerrak HVDC project

Feda converter station, Norway, in March 2007

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Converter station, Germany

Source: ABB - the Baltic Cable HVDC project

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North American electrical interconnection

High-voltage electrical transmission lines in North America are divided

into three separate grids (plus one).

� The Eastern Interconnection

� The Western Interconnection

� The Texas Interconnection

� Hydro-Quebec

The Western Interconnection is tied to the Eastern Interconnection through

six HVDC transmission facilities. The Texas Interconnect has two HVDC

connections to the Eastern Interconnection.

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Benefits of Interconnection

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Western-Eastern HVDC tie

Eastern-TexasHVDC tie

Hydro-QuebecHVDC tie

Source: NERC

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Regional Reliability Councils

FRCC: Florida Reliability Coordinating Council

MRO: Midwest Reliability Organization

NPCC: Northeast Power Coordinating Council

RFC: Reliability First Corporation

SERC: SERC Reliability Corporation

SPP: Southwest Power Pool, Inc.

TRE: Texas Regional Entity

WECC: Western Electricity Coordinating Council

Overall reliability planning and coordination of the interconnected

power systems are the responsibility of NERC - North American

Electric Reliability Corporation.

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Generating capacity and reserve margin (2006)

CAISO56,347 MW(RM 12%)

MISO137,232 MW(RM 18%)

ISO-NE30,895 MW(RM 10%)NYISO

39,704 MW(RM 17%)

PJM164,634 MW(RM 14%)

Southeast299,712 MW(RM 27%)

Southwest45,459 MW(RM 24%)

SPP45,950 MW(RM 9%)

Northwest57,120 MW(RM 42%)

TexasS: 70,756 MW(RM 14%)

Total: 947.81 GW

Source: Federal Energy Regulatory Commission (FERC)

The North America Blackouts 2003

� The 2003 blackouts in the US

and Canada was limited to

the synchronous areas only.

� The Quebec grid which is tied

to the neighboring systems by

both AC and DC links was not

affected.

Source: www.nativevillage.org/Editorials/august_2003_blackout.htm

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Mediterranean Ring - Concept

The goal of the ongoing Mediterranean Ring project is to provide

interconnection of electric power transmission grids among the

countries and regions that encircle the Mediterranean Sea.

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Mediterranean Ring Project

The objectives of such interconnections include:

1) Increase energy security

2) Defer new power plants

3) Balance electric power demand across the region

4) Reduce reserve margin in each country

Source: Hitz C. Breck, “Progress of the Mediterranean Ring”, Middle East Energy, August 2005

Spain

Turkey

Algeria

Libya

Egypt

Syria

Tunisia

400-500kV220kV90-150kV

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Blackouts and outage management

Typical US utility practices

The North America Blackouts 2003

� The 2003 blackouts in the US

and Canada was limited to

the synchronous areas only.

� The Quebec grid which is tied

to the neighboring systems by

both AC and DC links was not

affected.

Source: www.nativevillage.org/Editorials/august_2003_blackout.htm

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Basic outage management functions

@ Dominion Virginia Power (DOM)

• Handle outage calls from customer

• Dispatch crews to restore service

• Keep a written record

• Presumes that the over-current protection is properly

coordinated

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Trouble call flow-chart @ DOM

Work management system

A call from a customer

Trouble calls are entered into TRS

TRS stores all trouble calls and analyzes according to area, trouble type and device hierarchy and creates work requests

Trouble reporting system (TRS)

Mobile server

Mobile data dispatch (MDD) station

MDD receives work requests from the mainframe Work requests and status are

sent to and from the MDT

Mobile dispatch terminal (MDT)

Crews send work request status to the server and receive new work requests.

Source: Dominion Power

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Online outage reporting

Source: Dominion Power

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GIS for outage management

GIS display of electricity outages in

the Dominion Power’s area

Source: Dominion Power

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Mobile data dispatch (MDD) for quick restoration

� Computers installed in trucks and restoration vehicles

� Crews have up-to-date status of outages and receive real-time dispatch

� Operating centers share the same information and can inform customers

of progress and time estimates

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Thank you for your attention

Saifur Rahman

srahman@vt.edu

Professor and Director

Virginia Tech - Advanced Research Institute (VT-ARI)

4300 Wilson Blvd Ste 750, Arlington, VA

www.ari.vt.edu