SDHLT 02976 monitoring, control and protection of interconnected power systems

U lf Häger • Christian RehtanzN ikolai Voropai Editors Monitoring, Control and Protection of Interconnected Power Systems TRƯỞNG -DH HÀNG HAI \ IẺĨ NAM TÁI LIỆU THƯ VIỆN ringer... effor

Power Systems

F o r f u r t h e r v o lu m e s :

h t l p : / / w w w s p r i n g e r c o m / s c r i c s / 4 6 2 2

U lf Häger • Christian Rehtanz

N ikolai Voropai

Editors

Monitoring, Control and

Protection of Interconnected Power Systems

TRƯỞNG -DH HÀNG HAI \ IẺĨ NAM

TÁI LIỆU THƯ VIỆN

ringer

L ib rary o f C o n g re ss C o n tro l N u m b er; 2 0 1 4 9 3 1 9 9 9

© S p rin g er-V e rla g B erlin H e id elb erg 20 1 4

T h is w ork is su b jec t to co p y rig h t All rig h ts are re serv ed by the P u b lish e r, w h e th er the w h o le o r part o f

th e m aterial is c o n ce rn e d , sp ecifically the rig h ts o f tra n sla tio n , re p rin tin g , reuse o f illu stra tio n s, rec ita tio n , b ro a d c astin g , re p ro d u c tio n on m ic ro film s o r in an y o th e r p h y sica l w ay a n d tra n sm issio n or

in fo rm a tio n sto ra g e an d re triev a l, e le c tro n ic a d a p ta tio n , c o m p u te r so ftw a re , o r by s im ila r o r d issim ilar

m eth o d o lo g y no w k n o w n o r h e re afte r d e v elo p ed E x e m p te d fro m this legal re ser^ 'a tio n a re b rie f

e x c e rp ts in c o n n e c tio n w ith re v ie w s o r s ch o la rly a n aly sis o r m a te ria l su p p lied s p e c ific a lly fo r the

p u rp o se o f b ein g e n te re d a n d e x e c u te d on a c o m p u te r sy stem , fo r e x c lu siv e use by the p u rc h a s e r o f the

w o rk D u p lic a tio n o f th is p u b lic a tio n o r p a rts th e re o f is p e rm itte d on ly u n d e r th e p ro v isio n s o f

th e C o p y rig h t L aw o f the P u b lish e r’s lo c a tio n , in its cu rre n t v e rsio n , and p e rm is sio n for use m ust alw ay s be o b ta in e d fro m S p rin g er P e rm issio n s fo r use m ay be o b ta in e d th ro u g h R ig h ts L in k at the

C o p y rig h t C le aran c e C en ter V io la tio n s are liab le to p ro se cu tio n u n d e r th e re sp ec tiv e C o p y rig h t Law

T h e use o f g e n eral d e sc rip tiv e n am es, re g is te re d n am es, tra d e m a rk s, serv ice m a rk s , e tc in this

p u b lic a tio n d o e s not im p ly , e v en in the a b se n c e o f a specific sta te m e n t, that such n a m e s a re ex em p t fro m the re le v a n t p ro te c tiv e law s and re g u la tio n s and th e re fo re free fo r g en eral use.

W h ile the ad v ic e and in fo rm a tio n in th is b o o k a re b e lie v ed to be true a n d a c c u ra te at the d ate o f

p u b lic a tio n , n e ith e r the a u th o rs n o r the e d ito rs n o r Ihe p u b lis h e r c an acc e p t an y legal re s p o n sib ility for

a n y e rro rs o r o m issio n s th at m a y be m ade T h e p u b lis h e r m ak es no w a rra n ty , e x p re ss o r im p lie d , w ith

re sp ec t lo the m aterial c o n ta in e d h erein

P rin ted o n a cid -fre e p a p er

S p rin g e r is p art o f S p rin g e r S c ie n c e + B u sin e ss M ed ia (w w w s p rin g e r.c o m )

T o effectively support the aims o f these changes, the transm ission systems have

to be regulated because they are a natural monopoly Planning and operation o f modern transmission systems b ec om e more and more com plex for the following reasons:

• The location o f generation sites depends on the availability o f renewable energies and not on the location o f the major customers

• The nature o f renewable energy sources creates a substantial volatility in the transmission network

• Dispatchable pow er sources are replaced by stochastic generation patterns which need com plex and sophisticated prediction tools

• The acceptance for new transm ission lines by the public is a major barrier for the adequate expansion o f the transmission system

• The key for the successful transformation from fossil fuels/nuclear generation to renewable energies is a powerful transmission system tailored to its needs

I he contin uous growth o f interconnected transmission systems is an immense challenge because it leads to the most com plex technical system ever built by engineers Although the frontiers for the size o f future interconnected systems are continuously expandin g there is a conjecture concerning the optimal size o f a transm ission system This conjecture cannot be confirmed without looking into the details o f monitoring, control and protection o f interconnected power systems keeping the above m entioned paradigm changes in mind

The expansion o f the existing interconnected electric pow er transmission systems offers significant advantages with respect to operational security, inte­gration o f renewable energy, as well as energy trading On the other hand, the com plexity o f operational problem s significantly increases and hence large R & D

efforts are urgently required in order to make I'ull use of recent technological innovations with respect to new power system com ponents like wide area nu'ni- toring, control, and protection equipment, as well as ad vanced network contri>llers such as flexible AC transmission systems (FACTvS) and H V D C systems Furthermore, power system disturbances may result in major bla ckouts if m oni­toring, operation, and control o f interconnected power systems is not based on efficient and innovative information technologies The objectives o f the l'P7 project Intelligent Coordination o f Operation and Emergency Control of F-U and Russian Power Grids (IC OEU R ) sponsored by the EU com m ission are directly linked to the aspects o f a secure and econom ic operation o f large interconnected power transm ission systems, the integration o f renewable energy pow er genera­tion and the efficient system handling under em ergency conditions.

To achieve these objectives, a clo.se and trustful cooperation between many experts with a wide range o f expertise is an important prerequisite for creating a large impact on the future developm ent o f interconnected pow er systems Leading experts in all the relevant fields successfully com pleted the IC O EUR project It is most w elcom e that the important results and insights obtained in this successful project are docum ente d in this book It supports the dissemination efforts o f the ICOEUR research consortium in order to adopt the accom plished results co n ­cerning innovative monitoring, simulation and control concepts, experience with tools and equipment, and the im plementation o f the results

This book offers a systematic approach in looking for the optimal size of a large interconnected system from a technical point o f view A suitable basis for tackling the related problems is a well-defined basis consisting o f system models and systematic description o f relevant dynam ic phenomena This leads to a holistic simulation approach indispensable for the thorough understanding o f the future energy system Monitoring aspects ba.sed on state estimation and wide area monitoring deal with the reliable and com plete assessment o f the current opera­tional state o f the pow er system Without detailed knowledge o f the actual system state, a secure and econom ic operation is unthinkable Since the first efforts in the 1960s o f the last century much technological process significantly contributes to new effective solutions for the secure assessment o f the current system state

In view o f the aforementioned increasing volatility due to renewable gen e ra­tion, the dynam ic control o f interconnected power systems is o f increasing importance These control aspects are based on new operational equipm ent such as FACTS and H V D C as well as modern information technologies such as multiagent control systems Dynamic control intrinsically is related to system stability and the as.sociated protection techniques The reliable assessment o f a stable operating point with respect to voltage and frequency is a great challenge for modern information systems Interesting contributions have been achieved based on neural network approaches and artificial intelligence techniques A lthough being p o w ­erful, all these methods have limits and suitable methods are required for stabi­lizing the pow er system under em ergency conditions Under-frequency load shedding is a suitable method to guarantee a stable system state even under extrem e conditions All these methodological approaches lead to an important

an s w e r to the at'orementioneci conjecture related to possible limits of future

in te rconnecle d transmission systems The close interaction between energy and infvirmation technologies is under all circumstances an imporlanl prerequisite for successlully tackling the future challenges

This book is a com prehensive description o f all aspects related to modern

p o w e r transmission systems As it is the result o f a fruitful cooperation under the FP7 program o f the European Com m ission in collaboration with the Russian Federal Agency for Science and Innovation, it is an impressive contribution across national boundaries based on a successful cooperation between scientists and entiineers May this book be an important reference for all those responsible for the future electric energy transm ission systems

This hook has arisen out o f the results o f the jo in t research project Intelligent

C oordin ation o f Operation and Em ergency Control o f EU and Russian Power Grids (IC O E U R ) with partners from Europe and Russia We express our deepest thank to the European Com mission (under the 7th Framework Program) and the Russian Federal Agency o f Science and Innovation for supporting this work.The editors would like to thank all authors from the ICOEUR project for their very valuable contributions to this book Furthermore, a special thanks is given to Sven Christian Miiller, Hanno Georg and Prof Christian Wietfeld from TU Dortm und University for their contribution to Chap 19 supported by the Germ an Research Foundation DFG as part o f research unit F O R I5 I 1 "Protection and Control System s for Reliable and Secure Operation o f Electrical Transm ission System s"

W e express a special gratitude to Prof Edmund Handschin for providing his very valuable support to the ICOEUR project Also we would like to thank all

m em bers o f the ICOEUR stakeholder com mittee for discussions and practical advices on project results

The challengin g task o f writing and editing this book was made possible by the excellent cooperation o f the team o f authors together with a num ber o f colleagues ani.1 friends O ur sincere thanks to all contributors, proofreaders, the publisher and our families for m aking this book project happen

P art I In trodu ction

1 R eq uirem en ts for M on itorin g, C ontrol and O p e r a tio n 3

Christian Rehtanz, Nikolai Voropai and Ulf Häger 1.1 I n tro d u c tio n 3

1.2 Large-Scale Interconnected Power S y s t e m s 5

1.2.1 General Characteristics o f I P S / U P S 3

1.2.2 E N TSO -E C E 8

1.2.3 Interface Tie Lines Between E N TSO -E and I P S / U P S 9

1.3 Requirements and Innovation for Future Interconnected Pow er S y s te m s 10

1.3.1 Concept o f O p tim al Interconnection o f Large-Scale Power S y s t e m s 12

1.3.2 State Estim ation o f Large-Scale Interconnected S y s t e m s 13

1.3.3 Protection F unctions Securing Stable Operation of Interconnected N e t w o r k s 13

1.4 Structure o f the B o o k 16

R e f e r e n c e s 17

Part II S ystem M odel and D y n a m ic P henom ena 2 Load Flow and D ynam ic M o d e l 21

André Seack, Johannes S chw ippe, Ulf Häger and Daniil Panasetsky 2.1 h itr o d u c t i o n 21

2.2 Aggregated Network M o d e l 21

2.2.1 Aggregation o f Detailed Network N o d e s 22

2.2.2 Aggregation o f Transmissio n L ines 24

2.2.3 Allocation o f l.o ad and G e n e ra tio n 27

2.2.4 Unit C o m m i t m e n t 28

2.2.3 Dynamic M o d e l 29

2.3 Validation o f the Network M o d e l 30

2.4 C o n c l u s i o n s 32

R e f e r e n c e s 32

P o w er System D ynam ic P h e n o m e n a 3.5 Enrico Gaglioti and Adriano laria 3.1 I n tro d u c tio n 35

3.2 C l a s s ific atio n 36

3.3 Main C oncerns for Large Interconnected Power System s 37

3.4 Relevant Parameters for Transient and Small Signal Stability 38

3.5 Assessment M e th o d s 41

3.6 Improvement M eth o d s 42

R e f e r e n c e s 50

P art III M on itorin g o f In terconn ected Pow er S ystem s 4 M on itorin g T e ch n o lo g ies 53

Kay Görner Ettore Bompard, Tao Huang and Michael Kleemann 4.1 I n tro d u c tio n 53

4.2 C om m unication Exchange O v er T SO I n t e r c o n n e c t io n s 54

4.3 Hierarchy o f Control Centers in Power S y s te m s 55

4.4 Data C om m unication N e t w o r k 57

4 4 1 C om m unication Network in Control C e n t e r s 57

4.4.2 C om m unication Between Data Acquisition Units in Substations and Control C e n t e r s 58

4.4.3 P ro to c o ls 59

4.4.4 Peer to Peer Com m unications for Data Transmission O p t i i n i z a t i o n 61

4.5 Com parison o f Local Protection Devices, Wide Area Monitoring System and S C A D A /E M S for Detection o f Power System S ta te s 61

4.6 C o n c l u s i o n s 63

R e f e r e n c e s 64

5 W id e A rea M on itorin g S y s t e m 65

Tadeja Babnik, Kay G örner and Bojan Mahkovec 5.1 In tro d u c tio n 65

5.2 W A M S O v e r v ie w 66

5.2.1 Large Scale W A M S C o n c e p t 68

5.3 Phasor M easurem ent U n i t s 69

5.4 Phasor Data C o n c e n t r a t o r 70

5.4.1 Real-Time Data Exchange R e q u irem e n ts 70

5.4.2 Detection and Protection F u n ctio n s 71

5.4.3 Data S t o r a g e 73

5.4.4 Data V i s u a l i z a t i o n 74

5.5 W A M S E x p e r i e n c e s 74

5.5.1 Exam ple I: Un-D am ped Low-F requency O s c illa tio n 77

5.5.2 Exam ple 2: Recording o f Synchronization o f Turkish Power System with the Interconnected Power Systems o f Continental E u r o p e 79

5.5.3 Exam ple 3: Hydro Power Plant Outage in Turkey 81

5.6 C o n c l u s i o n s 82

R e f e r e n c e s 82

6 D i s t r i b u t e d S ta te E s t i m a t i o n 83

Irina Kolosok, Elena Korkina and Oleg Soukhanov 6.1 I n tro d u c tio n 83

6.2 State Estimation with Phasor Measurem ent U n i t s 84

6.3 The EPS State Estimation Problem and Solution Methods Based on Test E q u a t i o n s 85

6.3.1 Decomposition Methods for State Estimation o f Large-Scale Power S y s t e m s 87

6.3.2 Decom position o f the SE Problem with the Test liquations Method and PMU D a t a 88

6.3.3 Calculation E x a m p l e 93

6.4 Distributed Hierarchical SE o f Large Power Systems on Basis o f the Functional Modeling M e th o d 95

6.4.1 Description o f Distributed Hierarchical FM A l g o r i t h m 96

6.4.2 Solution M e t h o d s 100

6.4.3 Illustrative E x a m p l e 101

6.5 Outlook and C o n clu sio n s 104

R e f e r e n c e s I (15 7 D y n a m i c S t a t e E s t i m a t i o n 107

A nna Glazunova 7.1 In tro d u c tio n 107

7.2 Background I n f o r m a t i o n 108

7.3 M o d e lin g 108

7.3.1 Dynamic M o d e l 108

7.3.2 Model of M easurem ent D a t a 109

7.3.3 Kalman Filter 109

7.3.4 Objective Function o f Dynamic State Estimation 110

7.4 Applications o f Dynamic State l-stim ation I l l 7.4.1 Filtering o f Random Measurem ent l i r r o r s I l l

7.4.2 F o r e c a s t i n g

7.5 Numerical R e s u l t s

7.5.1 Test S y s t e m

7.5.2 Database C rea tio n

7.5.3 Kalman Filter T u n i n g

7.5.4 Filtering o f Random E r r o r s

7.5.5 Forecasting the State Vector C o m p o n e n t s

7.6 C o n c lu s io n s

R e f e r e n c e s

In ter-T S O S olution s for M on itorin g and S tate E stim ation 125 A n n a Mutule Karlis Brinkis, Oleg Kochukov and Kay Görner 8.1 I n tro d u c tio n 125

8.2 Test Case for Inter-TSO Network Monitoring and State E s tim a ti o n 126

8.2.1 Selection Reason o f the 330 and 750 kV Electrical Ring N e t w o r k 126

8.2.2 Modeling Schem e o f the Baltic Electrical Ring 127 8.2.3 Analysis o f Interconnection Points in Electrical R i n g 129

8.3 Prototype o f State E stim a tio n 130

8.3.1 Prototype D e s c r i p t i o n 130

8.3.2 Distributed State E stim ation 131

8.3.3 Dynamic State E s t i m a t i o n 132

8.4 Testing the Efficiency o f the Suggested Algorithm for Distributed State E s t i m a t i o n 133

8.4.1 Testing o f Sim ulator E f f i c i e n c y 134

8.4.2 Com parison o f Calculated Power Flow and V oltage Values in O T S E N K A Software with SC A D A M easurem ents in Electrical R i n g 134

8.5 C o n c l u s i o n s 138

R e f e r e n c e s I 39 P art IV C ontrol o f In terconn ected P ow er S ystem s 9 T ech n o lo g ies for th e C ontrol o f Interconn ected P o w er S y s te m s 143

A n g elo L ’Abbate and Ulf Häger 9.1 In tro d u c tio n 143

9.2 Control Technologies: P S T s 144

114 116 116 116 117

118

119

123 123

9.3 Control Technologies: EXACTS 146

9.3.1 Shunt C o n t r o l l e r s 149

9.3.2 Series C o n t ro l l e r s 152

9.3.3 Com bined C o n t ro ll e r s 154

9.4 Control Technologies: H V D C 158

9.5 Reliability and Availability o f FACTS and H V D C 165

9.6 C o n c l u s i o n s 167

R e f e r e n c e s 167

10 C o o r d i n a t e d P o w e r Flow C o n t r o l 171

Ulf Hiiger 10.1 In tro d u c tio n 171

10.2 Multi-agent System Structure for Distributed Coordination of P F C 172

10.2.1 C om m unication M o d e l 173

10.2.2 Principle C om m unic ation A m ong A g e n t s 173

10.2.3 C om m unic ation R u l e s 175

10.2.4 Assigning the S e n s itiv ity 175

10.2.5 Assigning the Direction o f I m p a c t 177

10.2.6 Distributed C o o r d i n a t i o n 178

10.2.7 Control of P F C s 178

10.3 Com parison Between O PF and Agents C o o rdina tion 179

10.3.1 PST Devices in the New England Test S y s t e m 179

10.3.2 Test Case S c e n a r i o s 180

10.3.3 Reference M e t h o d 181

10.3.4 Results E v a l u a t i o n 182

10.3.5 C o n c l u s i o n s 185

10.4 Large Scale Interconnection 186

10.4.1 Requirements for the C om m unic ation S y s t e m 188

10.4.2 Simulation Scenario with P S T 189

10.4.3 Simulation Scenario with T C P A R 191

10.5 Summary and C o n clu sio n s 191

R e f e r e n c e s 192

11 C o n t ro l o f I n te r c o n n e c t e d N e t w o r k s 195

Ettore Bompard and Tao Huang 11.1 In tro d u c tio n 195

11.2 M o tiv a tio n 195

1 1.3 Interconnected Power Grids as a Multiple-Layered System 198

11.4 TSOs as Interacting A g e n t s 201

I 1.5 Interacting Decision Making in Transm ission Systems: An Illustrative Eixample 203

11.6 C o n c l u s i o n s 212

R e f e r e n c e s 212

12 D istrib u ted O p tim ization o f In tercon n ection s 215

O leg Voitov, Lembit Krumrn and Oleg Soukhanov 12.1 In tro d u c tio n 215

12.2 O v e r v ie w 216

12.3 Definitions and T e r m s 218

I 2.4 Formulation o f the Current Flow Optimization Problem with Decomposition in Electrical N e t w o r k s 218

12.5 A lgorithm for Optimization o f Operating Conditions in the Electrical Network with Decomposition M ethods 220

12.6 Description o f Algorithms for Solving the Problem o f Current Flow Optimization on the Basis o f D e c o m p o s it io n 221

12.6.1 Formulation o f the Current Flow Optimization P r o b l e m 221

12.6.2 Decomposition Algorithm with Functional Characteristics Only Considering Equality C o n s t r a i n t s 223

12.6.3 Decomposition A lgorithm with Equivalent Characteristics Considering Only Equality C o n s t r a i n t s 224

12.6.4 Decomposition Algorithm with Functional Characteristics that Considers Equality and Inequality C o n s t r a i n t s 226

12.6.5 Decomposition Algorithm with Equivalent Characteristics that Considers Equality and Inequality C o n s t r a i n t s 227

12.7 Formulation o f the Short-Term Optimization P ro b le m 229

12 7 1 Algorithm for Solving the Short-Term O ptim ization Problem W ithout D e c o m p o s i t i o n 230

12.7.2 Algorithm for Solving the Short-Term O ptim ization Problem with D e c o m p o s it io n 230

12.7.3 After-Effect Function for Correction o f the Short-Term O p t i m i z a t i o n 233

12.8 Numerical R e s u l t s 234

12.9 C o n c lu sio n 236

R e f e r e n c e s 237

P a rt V S tab ility and P rotection T ech n iq u es in In tercon n ected P o w er S ystem s 13 P ro tec tio n T e c h n o lo g ie s 241

A n n a A restova and Andrey G robovoy 13.1 In tro d u c tio n 241

13.2 Local Protection S ystem s 242

13.3 Wide-Area Protection S y s t e m s 243

13.3.1 Fault Clearance R e l a y s 244

13.3.2 W ide-Area Out-of-Step P r o t e c t i o n 245

13.3.3 W ide-Area Oscillation D am p i n g 247

13.3.4 Adaptive P r o t e c t i o n 249

13.3.5 Adaptive S elf-H e alin g 250

13.4 C o n c lu s io n s 251

R e f e r e n c e s 2 5 1 14 D y n am ic S e cu rity A sse ssm e n t a n d Risk E s t i m a t i o n 255

Antans Sauhats, Evgenijs Kucajevs, Dmitrijs Antonovs and Rom ans Petrichenko 14.1 In tro d u c tio n 255

14.2 Risks in Power Systems, Sources and C o n s eq u en c es 256

14.2.1 Control o f a Power System in Terms of Its S e c u r i t y 258

14.2.2 Losses During Emergency S i t u a t i o n s 260

14.2.3 Probability o f Failures and Disturbances in the Power S y s t e m 261

14.3 Mathematical Determination (Definition) o f R i s k 262

14.3.1 Probabilistic A p p r o a c h 263

14.3.2 Deterministic Approach (N — I Criterion and Its L a c k s ) 265

14.4 W ays o f Risks M a n a g e m en t 266

14.4.1 Automatic Control A c t i o n s 266

14.4.2 Reserves for Power Balance M a i n t e n a n c e 267

14.4.3 Algorithms o f Automatic Under-Frequency Load S h e d d i n g 268

14.4.4 Power System S e p a r a t i o n 269

14.5 A Monte-Carlo Method as Tool for Risk Indicator C a lcu latio n 269

14.6 Exam ple o f Risk A s s e s s m e n t 272

14.6.1 Synthesis o f the Loss F-unction 272

14.6.2 Electric Power Supply o f C i t i e s 275

14.6.3 Power Supply Interruption and L o s s e s 275

14.7 C o n c lu s io n s 277

R e f e r e n c e s 278

15 C o n t a i n m e n t o f D i s t u r b a n c e s 281

Xiao-Ping Zhang, Xuefeng Bai and Jingchao Deng 15.1 In tro d u c tio n 281

15.2 Strategy for Interconnection o f Bulk Power S y stem s 282

15.3 Strategy for Preventive Control of Grid iin h a n c e m e n t 2S3 15.3.1 Strengthening o f the Interconnected G r i d s 2S3

15.3.2 Preventive Control for Security E n h a n c e m e n t 283

15.3.3 Application o f H V D C and PACTS for Preventive C o n t ro l 284

15.4 Strategy for Emergency Control o f Grid E in h a n c e m e n t 286

15.4.1 Pre p ro c essin g 288

15.4.2 Security A s s e s s m e n t 288

15.4.3 P o s t - p r o c e s s i n g 289

15.5 Strategy for Remedial Control o f Grid E n h a n c e m e n t 289

15.6 Strategy for Control Implementation o f Grid Enhancement 292 15.7 Case S t u d y 293

15.7.1 Emergency Control S t u d y 294

15.7.2 Impacts o f FACTS on Disturbance Contain m ent 295

15.7.3 Impacts o f VSC-FIVDC on Disturbance C o n t a i n m e n t 299

15.8 C o n c lu s io n s 300

R e f e r e n c e s 301

16 W i d e A re a P r o t e c t i o n 303

Christian Rehtanz Nikolai Voropai Ulf Häger Dmitry Efimov Daniil Panasetsky, A lexander Domyshev and Alexey Osak 16.1 I n tro d u c tio n 303

16.2 Protection System M o d e l i n g 305

16.3 Out-of-Step Prevention and E l i m i n a t i o n 307

16.3.1 Schem e o f Interrelation Between States and Control A c t i o n s 309

16.3.2 Criteria for Actions o f SOSPPS S t a g e s 310

16.3.3 Related P r o b l e m s 311

16.3.4 Case S t u d i e s 312

16.4 Distributed Protection System Against Voltage Collapse 315

16.4.1 Voltage Instability M e c h a n is tn 316

16.4.2 New System Protection P hilosophy 316

16.4.3 Multi-Agent Control S y s te m s 317

16.4.4 Multi-Agent Control System I m p le m e n ta tio n 321

16.4.5 Test S y s t e m 323

16.4.6 Voltage Stability C o n t ro l 324

16.5 C o n c l u s i o n s 331

R e f e r e n c e s 331

17 I n t e r f a c e P r o t e c t i o n 333

Lazar Bizumic, Rachid Cherkaoui and U lf Häger 17.1 In tro d u c tio n 333

17.2 Network M o d e l 334

17.3 Simulation and Control T o o l s 334

17.4 Simulation, Control Actions and R e s u l t s 33,5 17.4.1 AC Interconnection 33.5 17.4.2 HVDC I n te r c o n n e c t io n 340

17.5 C o n c l u s i o n s 346

R e f e r e n c e s 347

18 U n d e r - F r e q u e n c y L o a d S h e d d i n g S y s t e m 349

Vladimir Chuvychin Antans Sauhats, Vadims Strelkovs and Eduards Antonovs 1<S.1 I n tro d u c tio n 349

18.2 Theoretical B ackground 350

18.2.1 Hazards o f Under-Frequency O p e ratio n 351

18.2.2 Main Parameters Influencing the Character o f Frequency B e h a v i o r 352

18.2.3 Frequency Actuated Load Shedding as the Mean for Preventing Deep Frequency D e c l i n e 352

18.2.4 Main Parameters o f Under-Frequency Load Shedding S y s t e m 354

18.2.5 Maximal Capacity o f a Load in the Load Shedding S y s t e m 355

18.2.6 Frequency Rate-of-C hange as Additional Factor for l.oad S h e d d i n g 356

18.3 The Goal o f Analysis o f Frequency Behavior During Em ergency Situation in the Power S y ste m 356

18.4 Analysis o f Frequency Behavior for Different Algorithms of U F T S 358

18.4.1 Frequency Behavior in E N TSO -E During Operation o f U F L S 358

18.4.2 Frequency Behavior in the Power System of the Baltic States During Operation o f U I - L S 360

18.4.3 Frequency Behavior o f Joint Power System Operation with UFLS and Power Deficiency at the Baltic State S i d e 361

18.4.4 Frequency Behavior o f Joint Power System Operation with UFLS and Power Deficiency at the E N TSO -E S i d e 363

18.4.5 Simulation o f Joint Power System with Weak Intersystem T i e s 363

18.5 C o n c l u s i o n s 366

R e f e r e n c e s 367

Part VI Integrated System

19 C om p reh en sive Sim u lation F ram ew ork for Pow er

S ystem O p e r a tio n 3 7 1

Sven Christian Müller, Hanno Georg and Christian Wietfeid

19.1 In tro d u c tio n 37119.2 M o tiv a tio n 37219.3 Related W o r k 37319.3.1 Simulation o f Dynamic Power System O p eratio n 37319.3.2 Simulation o f Com m unication N e t w o r k s 37419.3.3 Distributed C om puter Simulation S y s t e m s 37419.3.4 Integrated Simulation o f Power Systems

and ICT N e t w o r k s 37519.4 Hybrid Simulation D e s i g n 37619.4.1 C om m unication Architecture M o d e l 37619.4.2 Power System Architecture M o d e l 37819.4.3 Integration Concept for ICT and Power System s 37919.5 Simulation R e s u l t s 38119.6 Outlook and D is cussion 38419.6.1 Future D evelopments and E x t e n s i o n s 38519.6.2 S um m ary and C o n c l u s i o n 386

R e f e r e n c e s 388

I n d e x 389

Part I

Introduction

With large scale deployment o f renewable generation throughout Europe, in particular large scale wind farms and future solar pow er plants, interstate inter­connections are of growing importance to secure energy supply They optim ize the utilization o f energy sources within larger areas, promote electricity trading between different regions, and meet the requirem ents o f economic development IPS/UPS can achieve similar benefits (so called system effects), by initiating joint operation with E N TSO -E using interstate interconnections.

The m ajor benefits that motivate TSOs to build up interconnections to neigh­boring transm ission systems are:

• O ptimization of the use o f installed capacities

• Reliability improvements reducing the economic cost o f power outages

• Improved control o f system frequency to minimize major disturbances

• Sharing reserve capacities and reducing the level o f reserves required

• Providing mutual support for the interconnected systems in case o f emergency

• linproved energy market conditions in better integrated large scale systems

• Facilitating large scale integration o f renewable energies due to higher flexi­bility o f the interstate network operations

Due to the fact that both systems o f Europe and Russia alone and especially with interconnections are second to none in the world in terms o f the scale and distance o f the interconnection and num ber o f countries involved, strong R&D and innovations are urgently required along with the recent development o f technol­ogies Presently, there are numerous enlargement projects o f EN TSO -I: and IPS/ UPS under consideration and investigation:

• interconnection o f T urkey was recently established

• interconnection to northern Africa (Tunisia, Libya, Morocco, etc.),

T he realization o f an interconnection o f bulk power systems, which differ in their technical characteristics, is not trivial and its technical and economical erificiency depends on the chosen technology as well as its impact on system operational security Currently there are multiple transmission technologies with miscellaneous technical properties available: i.e cost eliicient and well proven H V A C technolo­gies, with the disadvantage o f direct disturbance extension between interconnected systems or more sophisticated H V D C transmission systems with better cm trolla- bility but high investments In order to improve system stability, to con rol load flow, to facilitate electricity trading and to optim ize the utilization oi energy re.sources in interconnected power systems Flexible AC transm ission Systems (FA CTS) and H V D C as well as other innovative com pensation o r control devices can be used Due to that com plexity as a first step the technically and economically optimal realization o f future large scale interconnected pow er systems have to be investigated regarding interconnection technologies The beneficial integration of appropriately selected technologies is a precondition for the future d ev e lo fm e n t of large scale interconnected power systems

However, bulk power grids may en counte r m ajo r blackouts, often w t h ca ta­strophic consequences for system and consumers Some o f such severe b a c k o u ts occurred for instance in Europe and Russia in 2003, 2005 and 2006, respectively

A m ong the main factors leading to occurrence and developm ent o f such em e r­gencies, researchers call com plication in operating conditions o f the power grids

and their control in a tnarket environm ent as well as insufficient coordination of control at an interstate level The latter particularly manifested itself during the

2006 liuropean blackout Therefore the possible future extension o f pow er system interconnections requires elaborating methods for tnonitoring, control and opera­tion of large scale systems and especially for the support o f their interconnections Besides, the possible future interconnection between the Pan-European and Rus­sian electricity transmission systems would be greatly simplified if c o m m on/ com patible software tools, hard ware equipm ent and operational procedures are adopted by all TSO s involved The jo in t develo pm ent o f these tools and equipment will promote their adoption The presentation o f recent develo pm ents and their prototypically demonstration is the major goal o f this book The operability o f the results is demonstrated based on extensive network simulations using realistic network data

1.2 Large-Scale Interconnected Power Systems

All investigations in this book are related to real pow er system requirements As exam ples the interconnected power systems o f Europe (EN T S O -E ) and Russia (IPS/UPS) are considered

1.2.1 General Characteristics o f IPS/UPS

The Interconnected Power Systems/Unified Power System s (IPS/UPS) is a power union presently com prising synchronously operated power systems o f 14 co u n ­tries: Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Mongolia, Russia, Tajikistan, Ukraine, and Uzbekistan belonging to the C om m onw ealth o f Inde­pendent States (CIS) and Estonia, Georgia, Latvia, Lithuania as unbelonging th the CIS, The system is actually based on the former USSR Unified Power Systems originated in the mid 1950s o f the last century and being continuously developed over the last 50 years

Synchronous operation o f the power systems o f these countries is coordinated

by the Electric Power Council o f the CIS (EPC CIS), Within the framew'ork o f the

E PC CIS the C om m ission on Operational-Technological Coordination o f parallel operation of the pow er systems o f the CIS and Baltic countries (C O TC ) establishes recotnmendatory principles o f technical interaction and develops corresponding docum ents

The cooperation o f the Baltic power systems with the pow er systems o f the CIS coimtries is perform ed within the framew ork of the BR E LL -C om m ittee estab­lished on the base o f multilateral international agreement between T S O 's o f Belarus, Russia, Estonia, Latvia and Lithuania signed in 2002,

F i g 1.1 S tru c tu re o f in te r c o n n e c te d p o w e r s y s te m ( I l’.S /U P S ) o f R u s s ia a n d its n e ig h b o rin g

c o u n tr ie s

At the moment, with 335 G W o f installed capacity IPS/U PS annually supplies about 1,200 T W h to more than 280 million consumers This is the world’s most geographically extended pow er system, spanning over 8 time zones Such vast territory impedes certain specific features o f the pow er system:

• C om prises o f internally almost balanced regional pow er systems interconnected

in most o f the cases by congested links;

• Extensive use o f long-distance extra high voltage transm ission lines (up to 1,150 kV);

• U.se o f automatic em ergency control systems (in certain cases the N-l criterion

is only satisfied with the automatic em ergency control system);

• All power systems com posin g IPS/UPS are structurally allocated to 14 power regions (see Fig 1.1):

- 6 IPS in Russia (North-West, Centre, Middle Volga, South, Ural, and Siberia),

- Baltic States (Estonia, Latvia, and Lithuania);

- Ukraine and Moldova;

- Central Asia (Kirghizstan, Tajikistan, and Uzbekistan);

- 5 individual powers systems o f other countries (Azerbaijan, Belarus, Georgia, Kazakhstan, Mongolia)

In addition to l-ig 1.1 IPS/UPS has weak cross-border AC interconnections with Norway Turkey Iran Afghanistan and China.

liach power system regulates the active power balance with or without fre­quency dexiation correction, with or without autotnatic systems The UPS o f Russia controls frequency in the whole synchronous /one

North-Western IPS of Russia has a DC-link wilh Finland Another DC-link between Fsionia and Finland (ES T L IN K ) was com m issioned in Decetnber 2006

AC radial operation o f near generation is operated with Finland, too

Two scales o f nominal voltages are u.sed in the IPS/UPS: 750-330-220-1 10 kV and I 150-500-220-1 10 kV (now 1.150 kV equipment operates at 500 kV) T h e backbone network o f 2 2 0 -1 1 5 0 kV performs power transmission; while the lower voltage lines forrn distribution grids

In fact many electric ties in IPS turn out to be underloaded for a long time and their transfer capabilities are even below the litiiits determin ed by the standard margins

The European part o f R ussia's UPS including Ural, has a rather developed closed structure o f the main network It encompasses relatively weak ex tended transtnission lines between and within IPSs which cause problems o f irregular pow er fluctuations and angle stability (small signal and transient) The Asian Part

o f the UPS o f Russia is characterized by lengthier transmission lines that are mostly extended in latitudinal direction In West-Siberia they are mostly extended structure of the main network and have a chain-like structure in East Siberia and Trans-Baikalia The problem s o f irregular power fluctuations in transmission lines atid small signal and transient stability with respect to angle are also pressing here Until recently voltage stability problems arose mainly at local nodes that contained large amount of as ynchronous loads and appeared in the centers o f oscillations during emergencies

In the last decades develo pm ent o f large cities and megapolises has changed the main network structure This resulted in formation o f rather large highly m eshed zones with relatively short transmission lines between substations For such zones

I h e problem o f systetn voltage stability is getting urgent This problem was shown

by the blackout in M oscow and adjacent area in May 2005

The follow ing technical regulations are now in force in I h e synchronous area o f IPS/UPS but however, not fully confirmed by other countries than Russia:

• IPS/UPS Intergovernmental standard 1516.3-96 “ lilectrical equipm ent for a.c voltages frotn 1 to 750 kV Requirements for dielectric strength o f insulation"

!H;

• Methodical G uidelines for Power System Stability o f RE Ministry o f Energy [2|;

• Guidelines o f technical m aintenance o f Power Plants and Grids o f Russian Federation |3 |;

• IPS/L'PS Intergovernmental standard 14209-97 “ Loading guide for oil- itnmersecl pow er transform ers" [4|

I RccjiiirenuMits lor M oniuiring, C'omrol aiul OpL-ration 7

T h e transmission networks o f the E N TSO -E -C E m em bers supply electricity to about 4 5 0 million people with an annual consumption o f appro.ximately 2,500 T W h The E N T S O -E -C E system covers 23 European countries with some

2 2 0.000 km o f 400-kV- and 22()-kV-lines, thus being by far the largest

in terconnected system in Europe The annual peak load in 2006 was about

39 0 G W Eigure 1.2 gives a geographical overview about the synchronous areas o f

E N T S O -E -C E , IPS/UPS and other synchronous areas in Europe |5|

O v e r the 2nd half of the 20th century the E N TS O -E -C E interconnected system

w as designed in order to im plement principles o f solidarity and economy The

E N T S O -E -C E system develo ped progressively into the highly meshed network that provides routes for electricity from the generation in-feed to the co nsum ption and allows getting missing pow er from a neighboring control area through the available reserves o f partners Building on the essential principle o f solidarity, the reliability, adequacy and quality o f supply were continuously improved

T oday, TSO s are in charge o f managin g the security o f the operation o f their

o w n networks in a subsidiary way based on the E N TS O -E Operation Handbook Individual TSO s are responsible for procedures o f reliable operation in their control area from the planning period as in view o f the real-time conditions, with contingency and em ergency conditions The coordination between T S O s co n ­tributes to enhancing the shared solidarity to cope with operational risks inherent

to interconnected systems, to prevent disturbances, to provide assistance in the event o f failures with a view to reducing their impact and to provide re-setting strategies and coordinated actions after a collapse

However, the ENTSO-Ei interconnected system is being operated more and more at its limits Markets trigger an increase of cross-border power Hows between countries since markets by delinition aim at optimizing produced pow er depending

on short term price differences This leads to important variations o f generation patterns within the E N T S O -E -sy stem s displacing substantial am ounts o f electricity from one area to another, from 1 h to another, or even shorter

One current exam ple of cha n g in g generation patterns is due to the rapid develo pm ent o f wind generation characterized by short term predictability: within

a few hours, the production o f w in d farms can change from min imum to m axim um and conversely This can only be mastered with an adequate transmission in fra­structure and a m ore and more com plex managem ent o f the interconnected n e t­works, In reality, many E N T S O -E -C E TSOs face increasing difficulties to build new network infrastructures (lines, substations, etc.) This puts more pressure than ever before on all T SO s to be able to rely on each other via closer coordination mechanism s as those stated a m o n g ENTSO-E-standards

This is why E N T S O -E and formerly UCTE supported by the European C o m ­mission and all relevant stakeholders developed from 2002 their own "Security Package" as a set o f co m p lem en ta ry tools:

• The ENTSO-E Operation H andbook (OH) as a com pendium o f technical standards to be applied in the E N T S O -E interconnected system; OH constitutes the technical/operational reference for seamless and secure operation o f the pow er system;

• The Multilateral A greem ent (M E A ) as a cornerstone o f the legal framew ork for the security o f the E N T S O -E interconnected systems, since MEA introduces a binding contractual relation between all E N TSO -E T SO s referring to OH

• The Com pliance Monitoring and Enforcement Process (CM EP) as a recurrent ex-ante process verifying the im plementation o f the OH standards by all T SO s

as well as any measures individual T SO s have com m itted to towards the entire

T SO com m unity in cases o f tem porary non-compliance

Even if due to national legislation and regulatory frameworks as well as due to internal procedures each T S O has to follow additional rules, the EiNTSO-E Security Package remains the basic reference for security o f the interconnected system It substantially increases transparency of the fundamentals o f the T S O rules and therefore the necessary mutual confidence o f TSO s am ong themselves as well as their credibility towards stakeholders

1.2.3 Interface Tie Lines Between ENTSO-E and IPS/UPS

Several interfaces between EiNTSO-E and the IPS/UPS are still existing because o f the historical developm ent o f the system boundaries Table 1.1 (following mainly

|(i|) gives an overview about the interface lines between liNTSO-Ei CEi and IPS/ UI’S

T a b l e 1.1 E x is lin g tra n s m is s io n lin e s b e tw e e n E N T S O -B an d IP S /U P S

These transmission lines were operated as an integrated part o f IPS/Uf^S and

p o w er system " M ir ’" until 1995 when Poland, Hungary Slovakia and Czech Republic becam e synchronously interconnected to UCTE For a sy nchronous coupling o f E N TSO -E C E and IPS/UPS some o f these lines need to be refurbished and partly reconstructed

Due to their independent develo pm ent the major differences in system structure and certain operation philosophy variations exist between E N TS O -E and IPS/UPS

W hile both systems follow the ( n — 1 ¡-criteria, in IPS/UPS a wider range o f means

is used to overcom e the consequences o f disturbances (i.e pow er imbalances, grid elem en ts tripping or overloads, violations o f voltage limits, etc.): protection, re­dispatc hin g and automation actions com prising load and generation shedding

1.3 Requirements and Innovation for Future

Interconnected Power Systems

T h e considered interconnections would result in the largest p o w er system in the world, which provide a large energy market platform and integration platform for renewable energy to all participants An efficient and secure operation o f the largest electrical interconnections assumes:

• optim al choice o f network interconnection and extension technologies,

• effective control and monitoring systems and strategies,

• well defined protection functions that ensure secure operation o f all partn er networks in critical cases

of their individual technical and regulatory requirements.

In conclusion the presented results shall support the following urgent, high- iinpact functional needs, which can be regarded as improvetnents o f the current stale of the art:

• Delivery o f clear concepts of optimal interconnection o f large-scale pow er systems as o f EU and Russia

• Concepts for future oriented and sustainable grid expansion and grid enhancement

• Methods to increase observability o f large scale power system interconnections

• Better sensing, monitoring, understanding and predictability o f the power sys­tem state

• Novel control methods o f large scale interconnected transmission systems

• Innovative concepts for cooperation o f TSO s in interconnected power systems with regard to stability control issues

For each o f these pow er system functional needs, different technolo gies require

a more in-depth review, in order to have a portfolio o f different solutions to address wide issues These technologies are:

• W ide area monitoring o f power system state using P hasor M easurem ent Units (PMU)

• Real time simulators o f ultra-large pow er system interconnections

• PM U-based control applications o f large scale interconnected networks

• Coordinated planning, operation and control o f flexible pow er flow control devices

Based on the requirem ents specified above the follow in g innovations can be identified for the develo pm ent o f future interconnected p o w er systems

1.3.1 Concept o f Optimal Interconnection o f Large-Scale

Power Systems

There are several examples for successfully im plem ented interconnections between previously independent pow er systems F N TSO-H C E consists actually of

34 TSO s from 22 European countries

These TSO s are connected via AC technology and are operated with the same

frequency at 50 Hz A similar exam ple is the N O R D E L interconnection, which

was established in 1963 and com prises the pow er systems o f Denm ark, Finland, Norw ay and Sweden via AC links AC technology is well approved and requires low investments But AC transm ission leads to high losses over long distances and requires therefore expensive com pensations Disturbances in AC interconnected systems are visible in the com m on network and affect therefore all partners Alternative to H V A C technology HV DC is often used to create an intercon­nection between pow er systems Due to its technical nature HV DC allows higher operating voltages and provides higher capacity in com bination with low line losses The experience has shown that H V D C links can stabilize power systems, and in contrast to AC links they can maintain interconnected system operation during large disturbances, as happened during blackouts in USA and C anada in 14th August 2003 The H V D C links are also well approved and often used for the interconnection o f large pow er systems Exam ples for H V D C interconnections are links between E N T S O -E C E and E N T O S -E Nordic (form er N O R D E L ) or

E N T S O -E C E and E N T S O -E UK

C om positio ns o f both technologies are possible and are u.sed i.e in North

A merican electricity transm ission networks

A closer look to currently existing interconnections show s a high similarity of linked pow er systems concernin g the used transport technolo gy and network structure Almost all E N T S O -E networks use solely A C technology and only

sparely H V D C transmission system The used transmission lines have short d is­tances and the resulting grids are highly meshed.

In contrast to this, an interconnection of EU and Russian networks is an interconnection of pow er systems with significant differences The IPS/UPS net­work includes high rates of HV AC links, due to the fact that large distances have

to be covered between generation and load centers Therefore the interconnection design for such pow er systems has to consider the specific features of both networks

Anoth er motivation for new innovations is the fact that the AC technology has already reached its limits Due to this, previously m inor issues for the European

in te rconnecte d grids are now raised in their importance, i.e voltage stability problem s that previously presumed to be a problem o f weak, sparse meshed or large distance grids are considered as raising problem in the E N TS O -E C E net­work In particular, the creation o f very large synchronously interconnected electrical systems is a potential source o f stability problems, e.g with regard to inter-area oscillations

Such phenom ena, if not adequately controlled and dam ped, can cause unex­pected and cascadin g tripping o f critical cross-sections o f the system, thereafter determ ining unm eshed system operation conditions and outages, also in absence o f significant system disturbances This can be solved only by enhancem ent o f existing p o w er networks and making them more effective with regard to inter­connected operation, by means o f proper controls

Further challenges to the interconnected power grids result from new large changing p o w er flow scenarios due to liberalized electricity markets and a growing share o f renewable generation

Due to this previously adequate designed networks and interconnections are actually operated towards their limits Therefore measures for wide area grid and interciinnection enhancement are required

1.3.2 State Estimation o f Large-Scale Interconnected

Systems

State estim ation is normally applied for internal TSO control areas and considers only steady state network behavior New sources o f generation, like large-scale wind pow er penetration, and smart transm ission devices, like H V D C and FACTS, are either not consid ered at all or not m odeled adequately The current generation

o f state estim ato rs assumes steady state behavior within their calculation intervals

o f some tens o f seconds During alert or em ergency situations, when the system state changes fast, the accuracy o f state estimators deteriorates drastically In addition, inaccurate information about the state o f the neighboring systems may create a false sense o f security and hence aft'ect the efl'ectiveness o f security controls taken in case of large disturbances

M onitoring the state o f a tran.smission system is already a very coinplex task, and it is becomin g more and more com plex because o f the increasing degree o f interaction between the various T S O control areas Therefore an insight into the state o f the interconnected system is essential to maintain secure operation o f the interconnected as well as o f individual control areas The increasing num ber o f blackouts in recent years caused am ongst others through insufticient know ledge o f the interconnected system state highlights the necessity o f a new generation o f state estiination tools, which will help to solve this problem The vision o f growing interconnected systems suggest that for the first step also the fundamental step for monitoring and control o f large scale interconnected systems, new state estiination tools with consideration o f the developm ent in innovative power system m ea­surement and control technologies will give much more appropriate and accurate system state information o f its own system and the interconnected system, hence provide better basis for taking appropriate control actions against large system faults or disturbances.

The need o f innovations in the field o f state estimation strengthens with the increasing im plementation o f FAC TS within grid enhancem ent measures Appropriate models o f these smart FAC TS devices and their integration in the new generation o f state estimation tools are needed to provide intelligent monitoring tools with satisfactory functionality for systein operation and security

Improved network security can be achieved through increased collaboration and exchange o f information between transm ission system operators

The new generation o f state estimators has to provide TSOs with an accurate snapshot and robust indicators o f the system state even during em ergency situa­tions The key technologies to achieve this improved estimator p erform ance are Wide Area Monitoring System (W A M S ) technology for tim e-synchronized m ea­surements com bin ed with a central data concentrato r and distributed state estimators

Progress is envisioned in three specific directions as follows:

• The methodology for distributed state estimation to be developed provides each

T SO with an accurate snapshot o f the state o f its part o f the transm ission system

in relation to the overall state o f the interconnected transmission system This methodology will be based on the mutual exchange o f system inform ation and on-line m easurem ent data between interconnected networks The exchange of tim e-synchronized phasor measurem ents between T SO control areas with mutual access by the interconnected parties will be incorporated The infor­mation exchange will be used for the modeling o f neighboring network areas in such a way that the am ount o f data to be exchanged between individual state estimators is minimized

• In comparison to the current state estimation processing principle based on steady-state models, the approach here is a fully dynam ic state estimator Dynamic p henom ena like oscillations affecting the entire system will be iden­tified online With the new system state information obtained from the dynam ic state estimator, the operators can initiate security mitigation actions The

dynam ic state estimator is able to follow the system changes during an alert or

em ergency state with much higher accuracy than that using existing technology

• The method for online parameter identification to be developed provides system operators o f systetn simulation tools with far more accurate dynam ic models and parameters for the transmission systems and their com ponents than that cu r­rently available Accurate dynam ic models and model parameters are needed for operational security assessment but also during the system operational planning stage

1.3.3 Protection Functions Securing Stable Operation

o f Interconnected Networks

The seciuity standards applied by European TSO s are based on the conventional ( n —I ¡-criterion In security analysis this implies that the security and stability of the transm ission system is evaluated for a predefined list o f events (mainly single contingencies) The use o f this well defined deterministic approach to security assessment has in the past resulted in a very high reliability o f supply for both national and transnational transmission systems

The European interconnected pow er system implements the cooperation o f

IS O s for tnaintaining frequency stability Within this cooperation all TSO s mutually provide primary reserve, which is activated automatically in case o f pow er imbalances Additionally each T SO activates secondary reserve to displace primary reserve and to control the frequency in its own control area Such c o o p ­eration exists actually only for maintaining frequency stability, which is consid­ered today as a solved problem Similar T S O cooperation in the field o f angle or voltage stability or concerning instability due to inter area oscillations does not exist, what leads to wide propagation o f such disturbances affecting neighboring intercontiecled grids

Some litnited relief is provided by locally activated protection systems, which

h a \ e very sht>rt reaction times and response to local measured parameters These allow protecting important devices or limited network areas to be affected by the disturbance Long history o f blackouts shows that although protecting their local objects protection mechanistns often aggravate small disturbance and contribute to its large propagation

History shows very clearly that most large scale blackouts occurred though the ( n — I ¡-criterion was already used in the period o f scheduling/operation planning or during a series o f several disturbances This highlights the importance o f c o m ­plementary m eth ods and mechanisms for the maintenance o f system stability I'hese might include innovative cooperation rules regarding angle and voltage stability and inter-area oscillations 7’his possible T SO cooperation requires actually not existing methods for identification of em inent stability loss In case of interconnection of large scale power systems as that o f Pan-European and Russian

networks, priority will be given to total system stability as well as to the avoidance

o f large scale blackouts affecting several power systems with interconnections between them and to the m ain te n a n c e o f each individual network reliability This requires new protection m e ch a n ism s w hich are activated systematically and pro­tect the pow er systems against im p ro p e r states Such protection systems must consider smart devices as F A C T S integrated in the protected system

Significant progress is to be m a d e in fast stability assessment m eth ods dealing with the challenge o f identification o f instable modes o f large scale p o w er systems due to improper voltage or angle d e viations as well as inter-area oscillations Realization o f such a system is possible under co m bin ed utilization o f strategic placed PMUs centralized data co llec tio n and efficient stability assessment algorithms

Protection systems securing indiv idual systems must be activated selectively, systematically and coordina ted by a central entity based on not only local but also global information T h ey have to regard partial as well as total system stability issues trying to maintain stability o f the interconnected wide area systein as wide

as possible

1.4 Structure of the Book

The book presents results ta rgeting on the required and envisioned innovations specified above

For investigating large scale interconnec te d systems, models o f the respective networks are required Such m ode ls for static and transient investigations are presented in Part 2 of this book T h ese m o d e ls are based purely on public available sources and can be used as reference cases for research purposes It has to be stated clearly that the focus is both on the internal needs o f the network d ev e lo p m en t as well as their extensions and in terco n n ectio n s with surrounding systems

A basic requirem ent for future large scale power systems is a most m odern monitoring technology beyond the n o w ad a y s state o f the art Nowadays, regional control centers get steady state es tim a tio n information o f their respective system only With increasing in te rco n n ectio n s a n d size o f the system, system wide information o f the entire inte rconnec ted system as well as dynamic infom iation is needed to prevent large scale disturbances

Therefore the d ev e lo p m e n t o f m e th o d s and tools for monitoring o f large scale pow er systems is a key req u irem e n t an d objective The com m unic ation an d data exchange between control centers as well as system state estimation based o n wide area system monitoring are innovative approaches Use will be m a d e of the latest developm ents in sy n chroniz ed w ide area measurements, in in form ation and com m unication te chnolo gy, and in system identification New d eve lopm e nts need

to privilege the interconnection co n c e p ts and technical solutions that offer flexi­bility and m in imize the im pact on the p o w e r system operational organization to permit a progressive and m o d u la r extension o f the electrical system to be

interconnected with the p an-E uropean system Proposals for innovative solutions

in this area are presented in Part 3 o f this book W id e area monitoring systems build the basis for further deve lopm e nts D istributed state estim ation and dynam ic state estimation are proposed prom ising to increase the quality o f system infor­mation significantly

Beyond the better monitoring, new control a p p ro a c h es are required The basic technologies are wide area control m e ch a n ism s w h ich help for coordinated and automated control schemes N ew control te ch n o lo g ies and control schemes are presented in Part 4 The focus is on c o o rd in ated p o w er flow control, control of interconnections and optim ization o f inte rconnections

Another required innovation for in te rco n n ecte d p o w er systems are new pro­teclion mechanisms Efficient protection functions for secure operation o f large scale systems o f EU and Russia in both isolated o pera tion m ode and intercon­nected mode are needed In this context m e thods for quantifying the operational risk and tor assessing the stability o f a large transm ission system have to be developed Strategies for keeping system stability as w'ell as for certain dis con­nection of parts o f the systems in case o f im m in en t stability loss o f internal and external interconnections have to be defined Part 5 o f this book focuses on sta­bility and protection techniques Protection te ch n o lo g ies are analyzed Dynamic security assessment and risk estim ation is investigated and the containm ent o f disturbances is discussed

References

1 IP S /tJI’.S I n te rg o v e rn m e n ta l s t a n d a r d !.“) I6 3 -9 6 , E l e c t r i c a l E q itip in e itt f o r A C V o lta g e s f r o tn

i to 7 5 0 kV R e q u ir e m e n ts f o r D i e le c tr i c S t r e n g t h o f I n s iila tio n h ttp ://w w w e p r u s s ia r u /lib /