TITRE PRESENTATION 11

21/04/23

2

TECHNO-ECONOMIC ASPECTS OF POWER SYSTEMS

Ronnie BelmansStijn ColeDirk Van Hertem

PRESENTATION TITLE 3

• Lesson 1: Liberalization• Lesson 2: Players, Functions and Tasks• Lesson 3: Markets• Lesson 4: Present generation park• Lesson 5: Future generation park• Lesson 6: Introduction to power systems• Lesson 7: Power system analysis and control• Lesson 8: Power system dynamics and security• Lesson 9: Future grid technologies: FACTS and HVDC• Lesson 10: Distributed generation

OVERVIEW

OUTLINEINTRODUCTION TO POWER SYSTEMS

• Power systems• Grid structure• Grid elements• New investments in the grid

• Tasks of the TSO• Grid operation issues

THE GRID OF TODAY

• Transmission network• To transport the electric

power from the point of generation to the load centers

• All above a certain voltage

• (Subtransmission)• Distribution network

• To distribute the electric power among the consumers

• Below a certain voltage

STRUCTURE OF THE POWER GRIDWHAT’S THE DIFFERENCE?

• Transmission system• Higher voltage (typical at least 110 kV and higher)• Power injection by generation and import, large consumers• Interconnected internationally• Meshed nature-Redundancy

• (Subtransmission system)• Between transmission system and distribution system• Connection of large industrial users and cities• Open loop/partly meshed

• Distribution system• 400 V to some ten of kV• Industry, commercial and residential areas • Radial

INDUSTRIAL NETWORK (HAASRODE)

• Transformer: 70 kV/10kV, 20 MVA

UCTE

EXAMPLE: MAP OF THE IBERIAN TRANSMISSION SYSTEM

TRANSPORT OF ELECTRIC POWER

• Electric power P [MW]• Alternating current S [MVA]

• Two ways to increase the transported power• Increase current I

• Larger conductor cross-section• Increase voltage U

• More insulation

• Two ways to transport electricity• Alternating current (AC)• Direct current (DC)

P or S = U * I

PROBLEM FACED BY ELECTRICITY PIONEERS AC OR DC?

• Direct Current DC• Generator built by W. von Siemens and Z.Gramme

• Low line voltage, and consequently limitation to size of the system

• Alternating current AC• Introduced by Nikola Tesla and Westinghouse

• Transformer invented by Tesla allows increasing the line voltage

• Allows transmitting large amounts of electricity over long distances

TRANSFORMER

AC TRANSMISSION SYSTEM

• Frequency of 50 or 60Hz• Current changes direction 100 or 120 times a

sec• Active AND reactive power in the same line

• 3 phase system• Line voltages can be easily and economically

transformed up and down• AC current does not use the whole conductor

• Skin effect• AC conductors have larger diameters than adequate DC

SWITCHYARD

DC TRANSMISSION SYSTEM

• Only active power• Current flows in one direction• Conductor cross-sections fully used• Low transmission losses

• Requires DC-AC converters to control the voltage level• Expensive

• Switching of higher voltage DC more difficult

AC VS DC

• Advantages of AC • Cheaper transformation between voltages• Easy to switch off• Less equipment needed• Known and reliable technology• More economical in general• Rotating field

• Advantages of DC• Long distance transmission

• Higher investment costs offset by lower losses• on 1000 km line, 5% for DC opposed to 20% for AC

• Undersea and underground transmission• No reactive power problem

• Connection of separate power systems• With different frequencies (Japan,South-America)• Different control area, i.e. UCTE with Nordel and UK

COST OF TRANSMISSION LINEFUNCTION OF VOLTAGE LEVEL

LINES AND CABLES

• Overhead transmission lines• Economical

• However, visual pollution• Widely used in transmission over large distances

• Underground cables• More expensive than lines

• 5 to 25 times higher capital costs for 380kV• Underground, thus invisible to the public

• Ground above the cable can be still used• However, maintenance costs are significant

• Widely used in urban areas

OVERHEAD LINE

TRANSMISSION CAPACITY UPGRADE

• AC overhead• New line• Refurbishing• New conductor

types

• AC underground• Conventional cables• GILs• HTS

• Evaluation: different points of view• Technical• Economical• Regulatory• Environmental

OVERHEAD AC TRANSMISSIONNEW LINE

• Advantages• Widely used in transmission over large distances• Most economical (especially in rural areas)• Well-known technology

Best choice from techno-economic point of view

Classic approach to network reinforcement

OVERHEAD AC TRANSMISSIONNEW LINE

• Environmental aspects• Visual impact• Vegetation• Population• Town planning• Cultural heritage• Natural site and landscape

OVERHEAD AC TRANSMISSIONNEW LINE

• Social and political issues• Concern about health effects• Not popular → heavy resistance

• NIMBY• NIMTO• BANANA• CAVE• NOPE

• Regulatory• Permit process up to 15 years

OVERHEAD AC TRANSMISSIONNEW LINE

Conclusion

• Best from techno-economic point of view

• Worst from environmental, social & political point of view

• Very difficult to construct new lines in industrialized countries

alternatives needed!

OVERHEAD AC TRANSMISSION ADDING/REPLACING CONDUCTORS

• Increased ampacity• Without supplementary environmental impact• Within existing right-of-way

• Equip second circuit• No new towers needed cost effective

• Heavier conductors• Tower and foundation modifications may be needed →

very high cost

new conductor types

OVERHEAD AC TRANSMISSIONNEW CONDUCTOR TYPES

• Material properties• Composite core• Surrounded by aluminium(-zirconium)• Increased strenght and reduced weight• Increased ampacity

• Economics• Significantly higher cost• No tower modifications needed

• Regulatory• Outdated standards state maximum

conductor temperature independent of conductor type

• Other drawbacks• New technology → limited experience e.g.: no data on expected lifetime available• Higher operating temp losses increase

AC CABLES

• AC cables vs. overhead lines• Technical

• Almost no maintenance needed• Repair more difficult • Technical difficulties at high voltages• Limited distance

• Economical• 5 to 25 times higher capital costs (€/MVA)• Although cost differences have narrowed• Repair costs are significant

AC CABLES

• AC cables vs. overhead lines• Environmental

• Invisibility

• Dangers: oil spill, poisonous SF6 arcing by-products

• Social & political• Less right-of-way needed• Permitting takes less time• Less concern for health risks (although electromagnetic

fields are higher)• Ground above the cable can still be used

• Widely used in urban areas

AC CABLES

• Classic• Paper insulated, oil-filled• XLPE

• New types• Higher voltages• Lower losses• More expensive

AC CABLESNEW TYPES

• Gas Insulated Cables (SF6)• Higher voltages due to better insulation• Suited to bulk transmission• C lower suitable for long distances• Complex placement (many joints)• Arcing by-products hazardous for environment• Considered for future tunnel connections (e.g. in the Alps)

• Temperature protection• Operating very close to limits• Belgium: Tihange - Avernas

AC CABLESNEW TYPES

• High Temperature Superconducting• No conduction losses at cryogenic temperatures• Cooling losses• Cooling and cooling equipment expensive• Reduced dimensions• Environmentally friendly• Could prove economic for specific cases• R&D needed

AC CABLES VS DC CABLES

Source: ABB

CABLES

TASKS OF THE TSO

• Transmission System Operator TSO• Operates the grid

• Constant monitoring of system conditions • Frequency control (active power)• Voltage management (reactive power)

• Administrates the settlement of unbalances• Access Responsible Parties (ARP) need to balance their

productions and consumption• TSO takes actions if ARP deviates from the schedule• TSO charges the ARP for the incurred costs

“To keep the lights on”

ARP

I/E I/E

~ ~ ~Grids

Production

Consumer

ARP1 ARPN

Import/ Export

FREQUENCY CONTROL

TASKS OF THE TSO

• Frequency control• Primary frequency control

• Compensate for short-term unbalances at local level• Stabilize frequency within acceptable range around set point

• Secondary and tertiary frequency control• Control the load-generation balance at the programmed

export-import• Contribute to bringing the frequency back to its set point• Relieve the primary control reserve after an incident

• Scheduled (set point) frequency (time control)• Laufenburg control centre in Switzerland• To account for the Synchronous Time deviations

• 50.01 or 49.99 Hz for the whole day

TASKS OF THE TSO

• Reactive power management and voltage control• Primary voltage control

• Excitation of generators • Capacitors• SVCs (Static Var Compensators)

• Secondary voltage control• Zonal coordination of the voltage and reactive power control• Maintains the required voltage level at a key node

• Tertiary voltage control• Optimization of the reactive power distribution

• Based on real-time measurements• Device settings adjustment

TASKS OF THE TSO

• Constant monitoring of system conditions• State estimation

• To get best possible picture of system conditions• Find a best-fit load flow• Based on metered values (imperfect measurements)

• Contingency analysis• N-1 security rule

• One accident cannot bring the system in danger• Redundancy

FROM NATIONAL TO INTERNATIONAL GRID

SYNCHRONOUS AREAS IN EUROPE

• UCTE• Established in 1951 as UCPTE, 9 control zones, currently 27

• 23 countries, 33 TSOs, 620 GW installed capacity, 295 TWh exchanges• Full synchronous operation of its members in 1958• absorbed many “smaller” initiatives along the way

• CENTREL, SUDEL, COMELEC• 450 mln. people, annual electricity consumption 2500 TWh.

• Nordel• F,SWE,NO,DK (part)

• UKTSOA• UK

• ATSOI• Ireland

• UPS/IPS• Ex Commonwealth of Independent States

SYNCHRONOUS AREAS (1) WHY CREATE SYNCHRONOUS AREAS ?• Increase grid reliability and mutual support

• Improved system frequency control to minimize major disturbances

• Mutual support in case of emergencies • Sharing reserve capacities

• Facilitate functioning of the electricity market• non-discriminatory domestic and cross-border access to the grid• No need for synchronous area as such, also possible with dc links

Example of direct benefits• Zone of 15 GW production capacity loses its largest unit 1 GW

• Isolated: needs to develop 1 GW in less than 5s to avoid collapse• As a part of UCTE it needs to develop its share of the two largest UCTE unit,

and thus x% of 3GW, in 15-30s.

SYNCHRONOUS AREAS (2) CHALLENGES

• Coordination and control of the power flows• Interdependency of power flows• Interconnected systems share benefits and problems

• Problems on top of the above• Often different standards applied in control zones

TECHNICAL STANDARDS DIFFERENCES

• Exact same line can have different capacities• Different interpretation of frequency control• Different operational standards

Source:IAEW

SYNCHRONOUS AREAS (3) OPERATIONAL HANDBOOK (UCTE)

“Stronger interconnections require common and consistent understanding of grid operation and control and security in terms of fixed technical standards and

procedures”

• Result of discussion between all TSO’s involved • Successor of past technical and organizational rules

and recommendations• Unification and formalization of standards

• To make the best possible use of benefits of interconnected operation

• To keep the quality standards in the market environment

Operation handbook: http://www.ucte.org/publications/ophandbook/

CROSS-BORDER POWER FLOWSIN EUROPEAN GRID

• Typical power flow pattern• Countries structurally exporting or importing

• However • Unstable production strongly influences the pattern

• Wind generation

• Restrictions consist typically of several lines• What matters for the grid are individual lines flows!• This differs considerably from the physical “border

capacity”

UCTE PHYSICAL ENERGY EXCHANGES 2004 [GWH]

Source: DG COMP

LEVEL OF CONGESTION BETWEEN EU MEMBER STATES

FRANCO-BELGIAN BORDER 2001

• Unexpected flows not just ONE TIME event• More like a permanent thing

WIND POWER IS A PROBLEM

• Large wind parks problematic for the network• Unstable dispatch within a zone

• Will there be wind? Not too much?

• Unstable loop flows

• Benelux case• Positive correlation between loop flows and wind

in Germany• Up to 0.4

• Loop flows almost entirely through BE and NL

PHASE SHIFTER INVESTMENTS IN THE BENELUX IN ORDER ALLOW POWER FLOW CONTROL

1. Meeden (Nl)2. Gronau (D)3. Kinrooi (B)4. Kinrooi (B)5. Zandvliet (B)6. Monceau (B)

6

2

4

3

5

1

HOW DANGEROUS CAN UNEXPECTED FLOWS BE?

• Unannounced wind power in the north Germany• Actual event - Monday 27 Oct. 2003, 18h00 - 20h00

• Very heavily loaded D-NL border• 4550 MW total physical flows in the direction of NL

• 2380 MW more than scheduled

• Loss of N-1 security on 2 cross-border lines• Loss of N-1 security on phase shifting transformer

• Gronau (charged at 1250 MW) • Risk for the blackout in Benelux

UNANNOUNCED WIND POWER IN THE NORTH D SCHEDULED POWER EXCHANGES

B NL

D

CENTREL

RWE

ELIA TENNET CEPS

CZ

MVM

H

SEPS

SK

PSE

PL

A APG

CH

ETRANS

I

TERNA

ELESSLO

HEP

HR BiH

F RTE

E

REE

P

REN

PSE

ELES

North

South

- 1017 - 2967

- 504

+3903 +3126

+677

+2614

- 5380 - 452

646

2169

2150

798

1815

4669

118

3022

1704

575

481

120

401

667

173

532

1525GB

DC link 752

- 3068- 980

- 426

+3846

+2560

UNANNOUNCED WIND POWER IN THE NORTH D SCHEDULED POWER EXCHANGES VS PHYSICAL POWER FLOWS

B NL

D

CENTREL

RWE

ELIA TENNET CEPS

CZ

MVM

H

SEPS

SK

PSE

PL

A APG

CH

ETRANS

I

TERNA

ELESSLO

HEP

HR BiH

F RTE

E

REE

P

REN

PSE

ELES

North

South

- 1017 - 2967

- 504

+3903 +3126

+677

+2614

- 5380 - 452

646

2169

2150

798

1815

4669

118

3022

1704

575

481

120

401

667

173

532

1525GB

DC link 752

4553

342

2875

1267

28

817

1485

505

8461189

1421

- 3068- 980

- 426

+3846

+2560

UNANNOUNCED WIND POWER IN THE NORTH DDIFFERENCE BETWEEN PHYSICAL AND PROGRAMMED FLOWS

B NL

D

CENTREL

RWE

ELIATENNET CEPS

CZ

MVM

H

SEPS

SK

PSE

PL

A

APGCH

ETRANS

I

TERNA

ELESSLO

HEP

HR BiH

F

RTE

E

REE

P

REN

PSE

ELES

North

South

2384

147

150

22832320

1492

1307

4327

437

729

92

CUMULATIVE WIND POWER INSTALLED CAPACITY2005

WIND POWER INSTALLED IN EUROPE BY END OF 2005

SHARE OF DAILY WIND POWER IN RESPECTIVE DAILY PEAK DEMAND IN E.ON-GRID (GERMANY).

CONCLUSIONS

• Grid operation becomes more complex• Due to the market based flows• Caused by wind energy• Controlling frequency and voltage by active

and reactive power