POWER GENERATION&DISTRIBUTION

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1 POWER GENERATION&DISTRIBUTION Assistant Professor Suna BOLAT Office: ee 106 Phone:

2 Electric power system overview

3 Electric Power System Generation Transmission & Distribution Consumption

4 Generation and Consumption Konsumenten Produzenten The frequency increases Konsumenten Produzenten The frequency decreases Relationship between generation and consumption Source: ETRANS 19 September 2012 Electric Power Systems

5 Distributed / Decentralized Generation Centralized Generation Big power plants Transmission Distribution Consumption Distributed / Decentralized Generation (DG) Small power plants close to the consumers Wind, Photovoltaic, fuel cells, micro turbines, small CHP,... Often renewable primary energy sources Often private owners (households, small companies, ) Many DGs in Denmark, Netherlands, Finland,

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7 Decentralized Generation From: Centralisation and decentralisation in strategic municipal energy planning in Denmark Karl Sperling, Frede Hvelplund, Brian Vad Mathiesen, Energy Policy Volume 39, Issue

8 Connected Grids Advantages: Higher reliability of supply in overall network Exchange of energy internationally. Coupling: Synchronously (via 3-phase AC connections) Asynchronously (via HVDC connections)

9 TRANSMISSION&DISTRIBUTION

10 High Voltage Grid Long Distance Transmission (Country, Continent) Import/Export Infeed from large power plants 110 kv, 230 kv, 400 kv AC, power lines and cables HVDC Medium Voltage Grid Regional (sub-)transmission (Bigger cities, cantons) 10 kv, 30 kv, 50 kv AC, power lines and cables Low Voltage Grid Distribution to end consumers (homes, offices, ) 230/400 V Transformations in sub-stations

11 Overhead line 3-phase systems

12 Singal phase systems Double single phase system

13 Power cable

14 Gas insulated line (transmission)

15 Transmission&distribution

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17 Grid structures single lines are not sufficient to enable a reliable supply of electricity. A grid of power lines is needed through which the energy can be transported on alternative paths in the event of a line outage. This is referred to as redundancy. In order to provide a high degree of power availability, power grids should be operational under the following two system conditions: under normal operation: when all components, including power stations, transformers, and lines work properly, and under outage operation: when a defined number of operating components have failed.

18 Examples of grids with different security levels N-0 secure N-1 secure

19 Distribution grid

20 High&medium voltage distribution grid Voltage levels: Medium voltage: kv High voltage: kv Extra high voltage: kv Distribution in Europe: 20 kv Turkey: 34.5 kv Cypus:?

21 High&medium voltage distribution grid Radial grid s s s s

22 High&medium voltage distribution grid Ring grid s 500 kw cos =0,8 500 m 400 m 630 kva cos =0,6 10 kv 800 m 600 m 500 m 380 kw 500 kva 36 A

23 High&medium voltage distribution grid Meshed grid ~

24 Low voltage distribution grid 380 (220 1-φ) 400 (231 1-φ) 415 V (240 1-φ) V Energy is usually delivered by underground cables

25 Low voltage distribution

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28 Network operation characteristics 1. NETWORK VOLTAGE: determined according to the load and area Low voltage: 380, 415, 500, 600 V Medium voltage: 3, 6, 10, 15, 20, 34.5 kv High voltage: 66, 154, 220, 380 kv

29 Network operation characteristics 2. NETWORK FREQUENCY f = 50 Hz 3. NUMBER OF PHASE CONDUCTORS 3-phase 4. NUMBER OF LINES High voltage: 3 wires Low voltage: power consumers; 3 wires composite consumers (lighting and power); 4 wires

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31 Network calculations Thermal considerations Mechanical withstand Economical considerations (loss) Voltage drop Withstand to short circuit currents

32 Thermal considerations Maximum operating temperature Cross-sectional area of a conductor is determined by the Tables giving the current carrying capability

33 Current carrying capacity table for copper Size mm 2 Number of loaded conductors and type of insulation Two PVC Three PVC Two XLPE Three XLPE

34 Mechanical considerations In tables, minimum cross-sectional area for conductors is given according to the mechanical strength

35 Economical considerations Power loss during energy delivery will decrease with the increase in cross-sectional area but the cost will increase! total cost Installation cost q e loss cost Cross-sectional area

36 Voltage drop In low voltage networks, cross-sectional area of conductors are determined with regard to VOLTAGE DROP!! After that, all the other conditions are cross-checked. Type of installations Lighting circuits A low-voltage service connection from a LV 3% 5% public power distribution network Consumers MV/LV substation supplied from a public distribution MV system 6% 8% Other uses (heating and power)

37 Short circuit current In high voltage networks, cross-sectional area of conductors are determined with regard to SHORT CIRCUIT CURRENT!! After that, all the other conditions are cross-checked.