Power Transmission and Distribution - Siemens

Bottlenecks in Transmission Systems 

Large Blackouts World-wide 

Part 1: Reasons & Countermeasures … 

Part 2: Grid Enhancement with HVDC and FACTS 

…Lessonslearned ! 

Dietmar Retzmann 

Power Transmission and Distribution 

s 

High Voltage


Large Blackouts 2003 - Contents 

High Voltage 

1. Overview 

2. The US Blackout - Timeline 

3. Bottlenecks in UCTE ? 

4. Blackouts in Europe - and some others 

5. Blackout Prevention & Grid Enhancement 

5.0 Introduction 

5.1 Directing of Power Flow 

5.2 Avoidance of Loop Flows 

5.3 Prevention of Voltage Collapse 

5.4 Large Power Systems – Stability Problems & Solutions 

5.5 Blackout Prevention – Need of Investments 

Part 

1 

Part 

2 

6. HVDC & FACTS - Summary of Features 

7. Appendix - Documentation 

PTD H 1TM / Re 11-2005 2


High Voltage 

1. Overview 

Part 1 

PTD H 1TM / Re 11-2005 3


Reasons for high Probability of large Blackouts 

High Voltage 

• Systems too complex to 

be tested properly 

(Protection, Controls) 

• Insufficient Investments 

into the System (heavily 

loaded Network 

Elements) 

• Lack in Maintenance 

• Insufficient Training 

• Human Errors 

Expected 

Actual 

Source: 

PTD H 1TM / Re 11-2005 4


High Voltage 

The Situation: 

The Worlds largest Blackout 

in the US - and a similar 

Event in Europe ! 

PTD H 1TM / Re 11-2005 5


High Voltage 

2. 

The US Blackout - 

Timeline 

PTD H 1TM / Re 11-2005 6


High Voltage 

Analyzing the U.S./Canada Blackout 8-14-2003 

Initial Conditions before noon: 

• Reactive Power and Voltage Problems 

• Loop Flows across several States 

The following Blackout Summary (Sequence of Events) was reported 

by U.S. DOE on Sept. 12, 2003 and published on the Web. Additional 

Comments from other Sources are indicated. 

The Documents are embedded in the Appendix. The Web-Links are: 

Blackout Summary - Timeline 

http://www.energy.gov/engine/doe/files/dynamic/1282003113351_BlackoutSummary.pdf 

US-Canada Task Force Final Reports 

http://www.nrcan-rncan.gc.ca/media/docs/final/BlackoutFinal.pdf 

http://www.nerc.com/~filez/blackout.html 

but no major ones 

Additional Information is given on the 

European Blackouts and some Others 

PTD H 1TM / Re 11-2005 7


The US-Canada Blackout - from 12 to 4 PM 

High Voltage 

4 hrs. – a very long Time 

the “Result” 

How it “started” 

Now in Details - the Sequence of 

Events … 

Source: Blackout Summary, U.S./Canada 

Power Outage Task Force 9-12-2003 

PTD H 1TM / Re 11-2005 8


Event 4 – plus a major Computer Failure at 2:14 

High Voltage 

Reported Reasons: 

Brush-Fire under the Line 

(Source: U.S. DOE Timeline 09-12- 

2003) 

Starting around 2:14, FirstEnergy 

lost a number of EMS functions 

including Primary & Backup 

Server Computer 

(Source: EURELECTRIC 06-2004) 



PTD H 1TM / Re 11-2005 9


Events 5-7: from now on – a critical Situation 

High Voltage 

Outage of Line (5) was not 

reported to the Dispatching Center 

Line (6) contacted a tree* and tripped 

*Source: NERC-Technical 

Analysis 07-2004 



PTD H 1TM / Re 11-2005 10


Event 8 … and the decisive Event 9 

High Voltage 

Wrong Protection Relay Operation 

This was the main “Trigger” of 

the final Blackout Sequence 

(Source: EURELECTRIC 06-2004) 



PTD H 1TM / Re 11-2005 11


Events 10-12: 

Begin of Voltage Decline 

High Voltage 

4.09 PM: “Point of no Return” 

(Source: ITC 08-2003 – “Blackout”) 



PTD H 1TM / Re 11-2005 12


Events 13-18: 

“Severe Voltage Depression” 

High Voltage 

Loss of 3.4 GW 

Generation 

Source: Blackout Summary, 

U.S./Canada Power Outage Task 

Force 9-12-2003 

PTD H 1TM / Re 11-2005 13

High Voltage 


Consequences of Event 18: “Giant Loop-Flow”, 

Severe Voltage & Frequency Deviations (up & down) 

Source: Blackout 

Summary, U.S./Canada 

Power Outage Task Force 

9-12-2003 

PTD H 1TM / Re 11-2005 14


Event 18 in the ITC-Analysis: 

30 s to Blackout 

High Voltage 

Giant Loop 

Flow 2.8 GW 



PTD H 1TM / Re 11-2005 15


Events 23-26: 

Increasing Generation Outages 

High Voltage 

Loss of 1.9 GW 

Generation 



PTD H 1TM / Re 11-2005 16


Events 33-35: 

Cascading Blackout 

High Voltage 

out 

Source: Blackout 

Summary, U.S./Canada 

Power Outage Task Force 

9-12-2003 

PTD H 1TM / Re 11-2005 17


Finally, at 4:13 - 

a very Large Blackout 

High Voltage 



PTD H 1TM / Re 11-2005 18


The worlds largest Blackout – up to now 

High Voltage 

Approximately 50 million People in 7 States were 

out of Supply for hours or days. In spite of an 

initially suspected Terror act, there was a high 

Degree of Discipline everywhere. 

A total Amount of 62 GW Customer Loads was 

lost (this corresponds to half of the installed 

Generation Capacity in Germany) of which 49 GW 

have been reconnected within 16 hours. 

PTD H 1TM / Re 11-2005 19


The Blackout Area - a “Daylight” View 

High Voltage 

Source: Cigré Paris Session 2004 

PTD H 1TM / Re 11-2005 20


The Blackout – some more “Daylight”Views 

High Voltage 

Source: Web/Google 

PTD H 1TM / Re 11-2005 21


The Blackout – some more “Daylight”Views 

High Voltage 


PTD H 1TM / Re 11-2005 22


The Blackout Area - a “Night Light” View 

High Voltage 

“modified” Satellite Photo 

Some of the Reasons were: 

Overloads and Loop Flows 

Leading to Voltage Collapse 

A view on the 8-14-2003 Event 

PTD H 1TM / Re 11-2005 23


The Area of the Blackout - the “real” Photos 

High Voltage 

Blackout: a large Area is out of Supply 

Québec´s HVDCs assist 

for Power Supply and 

System Restoration 

However, some Islands still have local Supply 

Before the Blackout 

Source: EPRI 2003 

PTD H 1TM / Re 11-2005 24


The Blackout: some more “Nightlight” Views 

High Voltage 


PTD H 1TM / Re 11-2005 25


The Blackout: some more “Nightlight” Views 

High Voltage 


PTD H 1TM / Re 11-2005 26


Ontario Perspective: the Cascade in MW and kV 

High Voltage 

MW 

kV 


PTD H 1TM / Re 11-2005 27


Loop Flows in Ontario – from 16:09 to 16:12 

High Voltage 

Giant Loop Flows 

Source: VDN/ETG Fachtagung 10-11 Feb. 2004 Jena, Germany 

PTD H 1TM / Re 11-2005 28

High Voltage 


Frequency Scan at New York – from 16:10:34 to 

16:11:39 

∆ f = + 3.2 / - 1.5 Hz ≈ 5 Hz in 18 s 

Generators don’t 

like such 

Frequency 

“Excursions” - 

for HVDC & 

FACTS: there are 

no Problems 

PTD H 1TM / Re 11-2005 29


Voltage Recordings from EPRI/PEAC at 4:11 

High Voltage 

Voltage at 0.6 pu for 1s 

PTD H 1TM / Re 11-2005 30


Ontario – Summary of Events and GWs 

High Voltage 


PTD H 1TM / Re 11-2005 31

High Voltage 


The Final Report - Direct Causes and 

Contributing Factors 

Source: US-Canada Blackout Final Report April 2004 

PTD H 1TM / Re 11-2005 32

High Voltage 


The Blackout: Conclusions and Recommendations 

-an Excerpt 

3T: Trees - Tools - Training 

System Enhancement & Elimination of Bottlenecks 

● 

● 

On-Line Monitoring and Real-Time Security Assessment 

Increase of Reserve Capacity 

Source: US-Canada Blackout Final Report April 2004 

PTD H 1TM / Re 11-2005 33


Lack of Investments – Example Protection 

High Voltage 

Conventional Relays (not digital) lead to unselective 

Tripping under high Load Conditions 

X/Ohm 

100 

50 

× 

× 

50 100 

Conventional Tripping 

Characteristic 

Load Blocking 

(T-Bone) 

Sammis-Star: unselective Trip 

Load Flow – Steady State 

R/Ohm 

The Solution … 

Digital Protection: T-Bone- or MHO-Characteristic with 

incorporated Load Blocking 

PTD H 1TM / Re 11-2005 34

High Voltage 


What can actually be done ? Are other large 

Systems in the World Safe ? 

• Improvement of System Protection and Enhancement of 

Communication and Monitoring with IT (EMS & DSM) 

• Review of Generator and Load Trip Strategy (Under-Voltage 

and Under-Frequency Trip Levels and Times) 

• Use of FACTS & HVDC for Reactive-Power Compensation, 

Power-Flow Control and Prevention of Voltage Collapse 

• Active Damping of Power Oscillations with FACTS & HVDC 

• Possibly more HVDC in the interconnected US-Canada Areas: 

HVDC is a Firewall against cascading events (Voltage Collapse 

and Frequency decline): Québec was not affected ! 

• Increase of Reserve Capacity (HVDC, new Generations) 

Task Forces were “looking into” their 

own Systems all over the World 

PTD H 1TM / Re 11-2005 35

High Voltage 


Québec Canada was not affected – Why ? 

The Reasons are very clear: 

• Québec´s major Interconnections to the affected Areas are DC- 

Links 

• These DC-Links are like a Firewall against Cascading Events 

• They split the System at the right Point on the right Time, 

whenever required 

• Therefore, Québec was “saved” 

• Furthermore, the DCs assisted the US-System Restoration by 

means of “Power Injection” 

PTD H 1TM / Re 11-2005 36


High Voltage 

3. 

Bottlenecks 

… in UCTE ? 

PTD H 1TM / Re 11-2005 37

UCTE – The Control Areas 


High Voltage 

PTD H 1TM / Re 11-2005 38

The UCTE Structures – in Details 


High Voltage 

This all seems to be very well organized and regulated … 

Zone 1 & 2 “resynchronized” since 10-10-2004 

PTD H 1TM / Re 11-2005 39


Interconnection Spain-France: a weak Link 

High Voltage 

Understanding 

UCTE … 

Waiting for a new 400 kV Line ? 

…or using FACTS and HVDC? 

“Strong Lines” … 

only in IPS/UPS ! 

In UCTE, Load Flow is 

decisive for System Stability 

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

System unstable in Case of Power Reversal 

PTD H 1TM / Re 11-2005 40


The Risk: Inter-Area Oscillations in UCTE 

High Voltage 

An Example: 

Trip of 900 MW Power Station 

in Spain 

∆ f [mHz] 

15 

5 

-5 

-15 

-25 

-35 

-45 

-55 

-65 

Frequency 

Spain 

Active Power France-Germany 

(one 400-kV 

system) 

Frequency & Power 

Poland 

Germany 

(border to France) 

(border to France) 

P [MW] 

0 

-100 

-200 

-300 

-400 

-500 

-75 

-600 

0 3 

6 9 

12 

15 

t [s] 

Signals: simulated & measured by WAMS 

Mode 1: f = 0.21 Hz, Damping ζ = -3.7 % 

Source: CIGRE Report 38-113, Paris Session 2000 

PTD H 1TM / Re 11-2005 41


UCTE: it is a large synchronous System 

High Voltage 

The Interconnection France-Spain – a critical Bottleneck 

UCTE Synchronous Interconnections: 

Inter-Area Oscillations with Magnitudes up to 

1000 MW 

Damping Measures necessary 

…the 1 st Step for 

System Extension 

The Interconnection 

CENTREL to UCPTE 


PTD H 1TM / Re 11-2005 42

High Voltage 


TEN Studies on the dynamic Behavior of the 

UCTE Network for Stability Improvement 

Loss of Stability and Trip of Interconnection Lines 

∆f [mHz] 

Spain Poland 

No Damping Measures 

20 

20 

Germany 

“selected” 

PSS in CENTREL 

A 

B 

20 

Optimization in Spain only 

C 

20 

Load outage in Spain (500 MW) 

Optimization in CENTREL & Spain 

40 

…only ! 

D 

t [s] 


PTD H 1TM / Re 11-2005 43


High Voltage 

Experience with the 2 nd Step for System Extension 

UCTE synchronous Extension: 

Increased Inter-Area Oscillations 

Again: Damping Measures necessary 

However: who should do it and 

pay for the Investments ? 

Zone 1 

Operation Experience in 2005 with 

Zones 1 & 2 Resynchronization 

Zone 2 

Sources: UCTE & Measurements with WAMS, 5-2005 

PTD H 1TM / Re 11-2005 44


High Voltage 

4. Blackouts in Europe 

… similar Events and 

Root Causes 

PTD H 1TM / Re 11-2005 45

High Voltage 


At first - an Overview on the 2003 Events 

Great Britain (August 28): 

• 1 Transformer out of service due to Buchholz Alarm and 

a wrong Protection Relay Setting. However, only a 

limited Area (South London) was affected 

Denmark-Sweden (September 23): 

• A large Collapse in the Synchronous Area due to 

Power Station Outages in Combination with a double 

Busbar Fault (storms and wrong “construction”) 

Italy (September 28): 

• Outage of 2 major Transmission Lines; Overload on the __ 

remaining Lines – Full Blackout – very similar to the US- 

Canada Event 

PTD H 1TM / Re 11-2005 46

High Voltage 


Blackout in London – Sequence of Events 

Transmission System in South London 

3 

1 

2 

1 Transformer Buchholz Alarm 

Loss of Supply for 410,000 Customers in South London 

© Crown Copyright, National Grid Transco EL273384 

2 Disconnection of the first 275 kV Cable Section to isolate the Transformer 

3 Wrong Protection Setting ( Disconnection of the 2nd Cable Section 

Source: NGC Investigation Report 10-10-2003 

PTD H 1TM / Re 11-2005 47


High Voltage 

Denmark - Sweden: The Sequence of Events 

2 

23.9.03 

3 

Oskarshamm 

1 

1 

2 

3 

12.30 Outage of NPP 

1200 MW (faulty Valve) 

12.35 Double Busbar Fault 

Outage of 2 NPP 1800 MW 

The Consequences: Power Oscillations, Load-Shedding, 

Voltage Collapse - Restoration of the System at 19.05 

Source: EURELECTRIC External Reports 2003 

PTD H 1TM / Re 11-2005 48


High Voltage 

Horred Substation: The double Busbar Fault 

2 12.35 Double Busbar Fault 

Wrong Construction of Disconnectors: Fault between phases T & R of Bus B & A 

Source: Svenska Kraftnät 07-2004 

PTD H 1TM / Re 11-2005 49


Denmark-Sweden: The Result - Blackout 

High Voltage 

The Blackout Area is quite large ! 


PTD H 1TM / Re 11-2005 50

High Voltage 


6 Weeks after the US Blackout - a large Blackout 

in Italy … 

... the Risk for a Spread of Disturbance 

to UCTE was high 

Europe needs 

Enhancements, too 

From “White Night” to 

“Black Night” 

Source: VDN/ETG Fachtagung 10.-11.-2-2004 Jena, Germany 

PTD H 1TM / Re 11-2005 51


Italy: From “White Night” to “Black Night” 

High Voltage 

Due to Country-Wide Celebration 

of the “White Night” in Italy, a more 

increased Power Import of 6.7 GW 

was observed during Saturday 

Night, 9-27-2003 

“scheduled” Power Transfer from the Neighbors to Italy: 

6.4 GW out of 27 GW * Consumption: 24 % is too high ! 

*Source: EURELECTRIC Task Force Final Report 06-2004 

PTD H 1TM / Re 11-2005 52


Blackout in Italy - very close to the US Event 

High Voltage 

20 min. after the 1 st Line Trip: 

Loss of a 2 nd Line … and then a 

very fast cascading Sequence 

Outage of two inner-Swiss 400 kV Lines 

Overload on two 400 kV Lines from 

France to Italy and Trip of both 

Full Blackout in Italy, 9-28-2003, 

early in the Morning. Approximately 

50 Mill. People have been without 

Electricity Supply. Luckily, this 

happened on a Sunday. 

PTD H 1TM / Re 11-2005 53

High Voltage 

UCTE: Sequence of Events on the 

Interconnections 


20 min. after the 1 st Line Trip: 

Loss of a 2 nd Line … and then a 

very fast cascading Sequence 

Blackout in Italy 

Timeline: Initial UCTE Press–Release 09-29-2003 

PTD H 1TM / Re 11-2005 54


Effect of System Loading on Stability Margin 

High Voltage 

The Transmission Distance of considerable Power Transfer 

of 6.7 GW from the Generation located in Central Europe to 

the Consumers in Italy led to a relatively high Phase Angle 

Difference in the stationary parallel Operation between the 

UCTE main Grid: 

‣the immediate Reconnection of the Line tripping first was not 

possible because of a steady state Phase Angle Difference higher 

than expected 

‣the cascading Line Tripping evolved into a much more severe 

Angle Stability Problem 

Source: UCTE Interim Report 10-27-2003 

PTD H 1TM / Re 11-2005 55

High Voltage 


Frequency Behavior in Italy in the Transitory 

Grid 

after the 2 nd Line Trip in CH 


PTD H 1TM / Re 11-2005 56


High Voltage 

Italy Blackout: Transient Recordings from WAMS 

f, U, Q Uchtelfangen (D) and Heviz (HU) 

20 s 

Frequency in UCTE 

2 min 

f max 

≅ + 240 mHz 

Sources: UCTE Interim Report 10-27-2003 & 

VDN/ETG Fachtagung 10-11 Feb. 2004 Jena, Germany 

1 h 

PTD H 1TM / Re 11-2005 57


High Voltage 

Lessons Learned: 

A view on the 380 kV Lukmanier Line … 

Power Systems have not been designed for “wide-Area” 

Energy Trading with daily varying Load Patterns 

… near the Tree Flashover Event 1 

A Key-Issue in many Power Systems today: 


Source: The Grids UCTE Interim are “close Report 10-27-2003 to their Limits” 

PTD H 1TM / Re 11-2005 58

High Voltage 

Summary: 

Blackout in Italy: Conclusions 


‣ There is Congestion in the UCTE System 

‣ Too high Phase Angle Difference between UCTE main Grid and Italy 

‣ Voltage Collapse in Italy 

‣ Loss of Generation 

‣ Blackout in Italy 

Evaluation of Countermeasures: 

‣ Avoidance of Congestion 

‣ System Enhancement 

by means of: 

‣ Studies and enhanced Real-Time System Control … 


PTD H 1TM / Re 11-2005 59

Example: Real-Time Control … 


High Voltage 

… provides external Network Visibility ! 


PTD H 1TM / Re 11-2005 60


High Voltage 

Further Blackouts have been reported … 

EURELECTRIC Task Force Report 6-2004: 

‣ Spain, 12-17-2001: extremely cold weather conditions (high loads) 

2 hours of emergency conditions in the Spanish Grid – saved by 500 MW load 

shedding 

‣ Denmark, 12-28-2002: loss of supply for 1 million customers 

Reasons: 2 independent protection relay errors. Supply fully recovered in 3 hours 

‣ Austria, 8-27-2003: outage of Krsko Nuclear Power Plant in Slovenia, during 

tests, 

followed by transmission line trip Hungary Croatia (welded relay contact) 

Automatic disconnection device in Austria triggered, followed by severe crossboarder 

load changes. Full system restoration within 2 hours, no loss of supply 

… and some more (Cigré 2004, Paris Session), ref. to Documentation in the 

Appendix 

Various Reasons: e.g. load-flow problems, breaker explosion (Iran) 

PTD H 1TM / Re 11-2005 61


Countermeasures against large Blackouts 

High Voltage 

• Use of Advanced System Protection Schemes 

• Enhancement of Communication & Monitoring 

• Use of FACTS and HVDC to control Load Flow 

and to prevent Voltage Collapse 

• Use of Hybrid Interconnections with HVDC and 

FACTS for Stability Improvement 

• Implementation of HVDC as Firewall against 

cascading Events 

PTD H 1TM / Re 11-2005 62

Power Transmission and Distribution - Siemens

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