CIGRE – Comité Chileno · System Enhancement & Elimination of Bottlenecks ... bottlenecks are well known. Looking into details … Waiting for a new 400 kV Line ? # $ ' Source:

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Reliabilty of the Electrical Systems

Elimination of Bottlenecks in Transmission Systems using FACTS and HVDC

Mario Lemes – Siemens Brazil

Dietmar Retzmann – Siemens Germany

The Blackout – A spread of Cascading Events 

A brief Summary of the RoutCauses: 

n  Lack of Investments into the Grids (high CostPressure for the AssetOwners due to Deregulation), leading to Bottlenecks in Transmission 

n  Need for more Regulatory Works (Rules, Gridcode etc.) for the Operation of Transmission Systems and Power Plants in Case of Cascading Events 

n  Weak Points in the Energy and Demand Side Management  EMS, DSM

The Final Report - Direct Causes and Contributing Factors

Source: USCanada Blackout Final Report April 2004

The Blackout: Conclusions and Recommendations - an Excerpt

Source: USCanada Blackout Final Report April 2004 

3T: Trees   Tools   Training 

System Enhancement & Elimination of Bottlenecks 

●  OnLine Monitoring and RealTime Security Assessment ●  Increase of Reserve Capacity

What can be done ? Are other large Systems in the World Safe ?

n  Enhancement of Communication and Monitoring with IT (EMS & DSM) 

n  Review of Generator and Load Trip Strategy (UnderVoltage and UnderFrequency Trip Levels and Times) 

n  Use of FACTS for ReactivePower Compensation, PowerFlow Control and Prevention of Voltage Collapse 

n  Active Damping of Power Oscillations with FACTS & HVDC 

n  Possibly more HVDC in the interconnected USCanada Areas: HVDC is a Barrier against cascading events (Voltage Collapse and Frequency decline): Quebec was not affected ! 

n  Increase of Reserve Capacity (HVDC, new Generations) 

Task Forces are “ looking into”  their Systems  all over the World

Quebec Canada was not affected – Why ?

The Reasons are very clear: 

n  Québecs major Interconnections to the affected Areas are DCLinks 

n  These DCLinks are like Barriers against Cascading Events 

n  They split the Systems at the right Point in the right Time, only if necessary 

n  Hence, Quebec was “ saved”  

n  In addition, for the USSystem Restoration, the DCs assisted by “ Power Injection”

Spain-France Interconnections: A weak Link

“ Stable”  Power Flow: 1500  2000 MW. Stability Limit: 0 MW. 

System unstable in Case of Power Reversal. 

However, in UCTE, bottlenecks are well known. Looking into details … 

Waiting for a new 400 kV Line ?

Summary of Root Causes for Italian Blackout

Source: UCTE Interim Report 27.10.2003 

Source: UCTE Interim Report 27.10.2003

Blackout in Italy: Conclusions 

Summary: Ø There is congestion in the UCTE System Ø Too high phase angle difference between UCTE main grid and Italy Ø Voltage collapse in Italy Ø Loss of generation Ø Blackout in Italy 

Evaluation of Countermeasures: Ø Avoidance of Congestion Ø System Enhancement 

by means of: Ø Studies 

Source: UCTE Interim Report 27.10.2003

System Enhancement - How to use HVDC & FACTS

U U 1 1  U U 2 2 

U U 1 1  U U 2 2 

Parallel Compensation 

X X 

X X 

Series Compensation 

G ~  G ~ 

, , δ 1  , , δ 2 

sin ( sin (δ 1  δ 2 ) 

LoadF low Control 

P P 

P P  = =

Elimination of Bottlenecks in Transmission – Prevention of Overloads and Outages

Source: National Transmission Grid Study; U.S. DOE 05/2002 

Load Displacement (by Impedance Control) 

Short Circuit Current Limitation for Connection of new Power Plants 

The FACTS & HVDC “ Application Guide”  

Load Management by PowerFlow Control

Avoidance of Loop-Flows by means of Power-Flow Control

360 km 

400 MW 

Loads 

Loads 

3 ~ 

Power Flow Controller 

3 ~ 

Restoration of the initial Power Flow 

200 MW 

… Quite Easy 

A  B

UCTE: Load-Flow Improvement with FACTS/HVDC

DE  CZ 

Uncontrolled LoadFlow 

DE 

Power Flow Controller 

CZ Control of LoadFlow 

Benefits: Directing of LoadFlow 

Basis for Power Purchase Contracts

Voltage Collapse – without and with Reactive-Power Compensation

No Reactive Power Support 

Voltage remains low 

Reactive Power Support 

Voltage recovers

Voltage Collapse - How to explain it

n During the Fault, the Induction Machines Slip increases 

n This is like a Starting Conduction: high Currents 5 x I nominal 

n High Reaction Power Consumption decreases the Recovery   Voltage 

n ReactivePower Compensation is essential 

The Solution: SVC + MSC. Option: STATCOM. However, the 

required Reaction Time is  only  100 ms =

Voltage Collapse – What are the “Parameters” ?

Fault Duration: here 150 ms 

Initial Recovery Voltage ~ Σ S Machines 

SCC System 

SCC System + 5 x 

Very High Reactive Power Consumption

A Study Example: SVC Muldersvlei, RSA

No SVC  Voltage Collapse leads to Protection Trip and System Blackout 

With SVC  System recovers* 

The test Case : AC System with large Induction Machine Loads 

Fault Duration: 150 ms* 

* In this Simulation (RTDS), both Fault duration & Machine Rating have been selected to “ hit”  the Stability Limit → “ Slow Recovery”

Classification of Stability Problems in Power Systems 

Overview about basic physical Problems, which are related to a high loading of Transmission Systems by Transport of electrical Energy. 

The main types of Instability Concerns are: Ø Cascading Line Tripping by Overload Ø Loss of Synchronism due to Angle Instability Ø Oscillatory Instability causing self exciting InterArea Oscillations Ø Exceeding of the allowed Frequency Range (Over and Under Frequency) 

Ø Voltage Collapse 

Source: UCTE Interim Report 27.10.2003

Alternatives of Power System Interconnections

System  1  System  2 

a) AC Interconnection: many Lines “ at the Beginning”  

c) Hybrid AC/DC Interconnection: The flexible synchronous Solution 

b) DC Interconnection: 1 Link sufficient for stable Interconnection

HVDCLDT 9 GW: TAGG 

Tomorrow: 

Power Exchange today: Western  Eastern  700 MW Western  ERCOT  200 MW Eastern  ERCOT  800 MW

US Grid: DC Energy Bridges - more in the Future ?

Eastern Interconnection 

Western Interconnection 

Power River Basin, WY  Chicago, IL 

DCLinks Today: 

TAGG  TransAmerica Generation Grid: “ Coal & Wind by Wire”  

ERCOT Los Angeles, CA 

Planning the Future 

New DCs from Canada ?

System A

AC double-link 1

1200 MW

Ac double-link 2 7

System B

200 GW Grid A 200 GW Grid B

System Stability: Comparison of AC & Hybrid Interconnection (Study for 400 kV Grids)

System A System B

AC double-link 2

DC-link 1

7 1200 MW

AC & Hybrid Interconnection - Test Results

Only AC  System instable after Fault  Hybrid AC/DC  System remains stable 

AC Link 1 

AC Link 2  AC Link 2 

DC Link 1

m With DC Solution, Interconnection Rating is determined only by the real Demand of Transmission Capacity

m With AC solution, for System Stability Reasons, AC Rating must be higher than the real Demand on Power Exchange

m Increase of Power Transfer: With DC, staging is easily possible

m With DC, the Power Exchange between the two Systems can be determined exactly by the System Operator

m DC features Voltage Control and Power Oscillation Damping

m DC is a Barrier against Stability Problems and Voltage Collapse

m DC is a Barrier against cascading Blackouts

m Predetermined mutual Support between the Systems in Emergency Situations

Benefits of DC Solution for System Interconnection

How large can a synchronous System be ? 

Effor ts, Benefits 

Interconnected Operation 

Benefits 

Efforts 

Advantages of 

Size of inter connected Gr id 

Optimum 

Effor ts, Benefits 

Interconnected Operation 

Benefits 

Efforts 

Advantages of 

Size of inter connected Gr id 

Optimum 

Interconnected Systems 

o Load Flow Problems (needs Management of Congestion) 

o Frequency Control 

o Voltage Stability 

o Oscil lation Stability 

o InterArea Oscillations 

o Blackout Risk due to cascading Effects 

o Physical Interactions between Power Systems 

When the Synchronous System is very large – Advantages diminish 

Long Distance Transmission Systems 

o  Voltage Stability 

o  Reactive Power Problems 

o  SteadyState Stability 

o  Transient Stability 

o  Subsynchronous Oscillations 

Limitations of large AC Systems

FACTS & HVDC - The Result

Influence: *

¡ low or no l l small l l l l medium l l l l l l strong

* Based on Studies & practical Experience

HVDC (B2B, LDT)

UPFC

(Unified Power Flow Controller)

SVC (Static Var Compensator)

STATCOM (Static Synchronous Compensator)

Load-Flow Control

Voltage Control: Shunt Compensation

l l l l l l

l l l l l l

FSC (Fixed Series

Compensation)

TPSC (Thyristor Protected Series Compensation)

TCSC (Thyristor Controlled Series Compensation)

Variation of the Line Impedance: Series Compensation

Voltage Quality

Stability Load Flow

Scheme Devices Principle

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¡

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¡

Impact on System Performance

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System Interconnections: The “Extended“ HVDC & FACTS Application Guide

System A 

System B 

System C 

System E 

System F 

HVDC LDT 

B2B  GPFC 

FACTS 

Voltage Power Flow 

Control of  Limitation of 

Faults  SCC 

Power Swing Damping 

Barrier x x

x TCSC

x

SVC* SVC* SCCL

x

x

x

x Barrier 

Spread of Voltage Collapse

x

x

x Risk

Risk of Spread of Voltage Collapse Barrier Barrier Risk

System D

*or STATCOM

Lessons learned: HVDC and FACTS are essential for Transmission

Need for Advanced Transmission Solutions

This is This is unavoidable unavoidable ...   but ...   but HVDC & FACTS HVDC & FACTS can support can support Recovery Recovery 

Reduction Reduction of Outage of Outage Times & Times & more more  Stability Stability 

Blackout Blackout Increasing Increasing Oscillations Oscillations 

If there is no If there is no HVDC HVDC, , no no FACTS FACTS ... ...

Intelligent Solutions for Power Transmission

Thank You for your Attention!

with HVDC & with HVDC &

FACTS from FACTS from

Siemens Siemens