Distribution networks in Germany Lecture at the Universidad de Chile 20.04.2005 Prof.-Dr.-Ing. E. Handschin edmund.hands

1. Distribution networks in GermanyLecture at the Universidad de Chile 20.04.2005 Prof.-Dr.-Ing. E. Handschinedmund.handschin@udo.edu

2. Basic data of the German electricity network • Decentralised power supply • Supply reliability • Communication networks for the power supply • Powerline in low tension networks • Operating state diagnostic • Conclusion, Outlook Content

3. Basic data of the German electricity network German Extra-High Voltage Network Control areas 1 EnBW Transportnetze AG 2 E.ON Netz GmbH 3 RWE Net AG 4 Vattenfall Europe Transmission GmbH

4. Cables and overhead lines age pattern of the equipment age pattern of the cables

5. Distribution networks in Germany Electricity network operators approx. 900 mains supply operators

6. Average electricity bill of a three-person-household per month in € (Source VDEW)

7. Power capacity 2002 till 2030 Replacement of Investment Water Wind Other thermal Oil Natural Gas Hard Coal Lignite Uranium ? installed power in Germany

8. Technologies of DECS ~ ~ ~ ~ Decentralised Energy Conversion Systems natural and bio-gas regenerative Gasmotor Gasturbine Stirlingmotor Photovoltaic Wind energy Hydro Fuel Cell Microturbine ... 100 kW • ... 2000 kW • .. 2000 kW • • ... 250 kW • ... 200 kW • ... 250 kW ... 2000 h/a • • ... 3000 h/a ... 5000 h/a • • ... 8000 h/a • ... 8000 h/a • ... 8000 h/a DC DC DC DC DC AC AC AC AC AC

9. Characteristics of dispersed generation plants

10. Contribution of the renewable energies to power generation 1990 – 2004(source:BMU) Hydropower Wind power Biomass Photovoltaic [TWh] 60 50 40 30 20 10 0 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2004 2003

11. Present Structure of Electric Power Systems Problems: • Flexibility of generation and distribution • Operating costs • Approval of projects • Supply quality • Developing countries Large power plants supply all customers Power plants 110/220/380 kV 10/20 kV 0,4 kV Household Industry

12. Centralized / Decentralized Electric Power Systems Advantages: Dispersed generation Energy storage Power quality + Intelligent communication systems + Decentralised energy management systems = Storage Industry Power Quality Household Metering Solar Storage 110 kV 10/20 kV Fuel Cell Combined cycle plant The Electric Power Network of the Future 0,4 kV Wind

13. The Distribution Grid Structure in Comparison Today ~ WEC 10 kV 10 kV 0,4 kV ~ PV ~ PV Tomorrow Yesterday ~ 10 kV 10 kV WEC 10 kV 10 kV Electricity Heat/Cold IT Water FC ~ 0,4 kV 0,4 kV ~ ~ ~ PV PV FC ~ ~ FC FC ~ ~ PV FC

14. Need for Action Definition of supplementary supply conditions Technical + Economical + legal = Integration Integration of DG in the Distribution Network + Superposition of perturbations, in particular for f > 2,5 kHz + Installed Protection must be re-designed + Liberalization + Ancillary Services + ... Individual Integration Fixed Integration Spectral Network Impedance Certification Distribution Capacity Network Protection

15. Extended connecting conditionsspectral grid impedance I Grid impedance at PCC 1 h UN h PCC Z 1 h ZN h UN 10 kV 0,4 kV h ZT h h ZÜ1 ZÜ2 Transformer h Z = f ( ZN, ZT, ZI, ZÜ, x, t, h ) 1 Cable / overhead line CK h ZÜ4 System-capacities Measurement at PCC 1 1 h PCC Z PCC Point of Common Coupling 1 h h I M UN h IV h h ZI I Um Household supply connection with inverter, load and source of interference External AC-Source

16. Extended connecting conditionsspectral Grid impedance Compatibility level for U Mathematical result Impedance characteristic curve at PCC measurement Individual Compatibility level Individual compatibility level Current characteristic curve Inverter Connection Spectral Grid-impedance characteristic curve as basic connection condition

17. Voltage scheduling Usoll,UW= 10,6 kV Usoll,UW= 10,2 kV U= 10,9 kV U= 10,6 kV U= 9,7 kV U= 9,4 kV feeding: P= 4,3 MW Q= 2,1 MVar load: PL= 4,3 MW QL= 2,1 MVar • Main operators are obliged to supply customers in the LV-grid with supply voltage in interval Un-10% < U< Un+ 10% (DIN IEC 38). • Voltage control for MV- and LV-grids takes place centrally at the power substation (PS). • Problems for voltage control in grids with distributing poles (dp) with high load and feeding • voltage decrease for the right distributing pole • voltage increase for the left distributing pole load flow voltage drop

18. Short circuit power MV- unit short-circuit power high voltage bus MV- unit G G G G • Dimensioning of the dynamic short circuit power considers only the contribution of the feeding grid. • At the 100 % level of the dynamic strength determined by the feeding network increased risk in the direct vicinity of the substation. G G G G

19. Islanding Þ Lost of the MV-Grid because of failures or unbalanced Power K01 K03 • Failure ONT Disconnection 10 kV Grid • Maintenance 10 kV / 0,4 kV Disconnection K02 K04 ~ DG in grid coupled Mode Consequences of islanding in grid coupled operation Islanding can occur in grid coupled operation Þ NO zero voltage operation warranted Þ short-term feeding of short circuits Þ High thermal load of inverters and other Þ Lost of the LV-Grid at service entrance Grid components box because of failures Þ Voltage procrastination in case of Þ Operational disconnection at local grid single-phase connection Þ transformer by the power company Lost of the selective protection (error location)

20. System Configuration

21. PowerlineSource: http://www.its05.de/html/powerline.html Voltage inhouse

22. Distributed Hierachical Energy Management System visualization coordination visualization visualization coordination coordination visualization visualization coordination coordination MT3 FC3 PV3 FC: fuel cell WT: wind turbine PV: photovoltaic MT: micro turbine WT1 PV2 PV1 MT2 WT2 FC1 MT1 FC2 WT3

23. Asymmetry • Asymmetry • Unbalanced allocation of 1-phase loads, as well as the operation of 2-phase loads stress transformers and grids asymmetric. • Asymmetric operation of the grid can have different effects • unbalanced transformer load, -losses, -hum • Motors are running unbalanced • high losses  • short durability • abrasion of bearings • undefined reactive current compensation (Costs)

24. Summarising of single devices to classes, which are characterised by same lifetime-cycles • Statistical model of aging- and innovation processes • Evaluation of expected failure rates • Long-term prediction of maintenance and replacement • Comparison of different maintenance and replacement strategies Maintenance and replacement strategies of distribution networks

25. Requirement Maintenance Renewal Modelling of aging processes Maximum age Aging process influenced by maintenance measures Maintenance and replacement strategy (chronological or budget) History of maintenance and replacement of each class Simulator routine planned unplanned Failure rates Replacement Maintenance and renewal strategies of distribution networks

26. Replacement and failure rate [1/a] Period of rising replacement requirement in case of strategy “2% per year” failure rate > 2% 0,03 0,02 2% replacement per year 0,01 failure rate per year 0 0 1 2 3 4 5 6 7 9 10 8 Year 2,5% replacement per year failure rate per year Influence of different replacement strategies

27. CONCLUSIONS • Currently there is only limited experience with dispersed generation (DG) within the distribution network • A high penetration of dispersed generation requires detailed investigations, concentrating on protection devices and power quality; existing distribution networks were planned under different operating conditions • Increasing penetration of DG leads to new requirements of the network operation • Economic operation of virtual power plants needs a new energy management system (Multi agent real-time system) • The virtual power plant characterizes the future vision of distribution systems • Maintenance and replacement strategies have to be optimized to reduce distribution network costs