Distributed Generation By Roland Desouza
- 1. Experiences in Electrical Engineering Distributed Generation Aluminium Cables Roland deSouza, FIEEEP Naveed Jabbar, AMIEEEP
- 3. Origin of Electricity Networks Took place about 125 years ago Most of them comprising: Major generation plants EHV, HV, MV & LV networks Integrated, generation, transmission, distribution & supply
- 4. Distributed Generation (DG) Common characteristics are: Connected to utility MV or LV distribution network Of small rating (< 50MW) Privately owned Not centrally dispatched Not contributing to voltage / frequency control Not considered when the local grid was planned Generally based on cogeneration, renewable energy (small hydro, wave, wind, solar) or waste fuel (sewage gas, land-fill gas, bio-mass )
- 5. Typical Categories of DG ≥ 10MW Large a) ≤ 1MW but > 500kW connected to distribution system voltage ≤ 15kV b) > 1MW but ≤ 10MW connected to distribution system voltage ≤ 15kV Mid-sized a) ≤ 500kW connected to distribution system voltage ≤ 15kV b) ≤ 1MW connected to distribution system voltage ≤ 15kV Small ≤ 10kW Micro Rating DG Classification
- 6. Advantages & Benefits Among the many are Reduction in transmission/distribution losses Reduction in loading of transmission/distribution networks Avoided carbon emissions from reduced losses Avoided carbon emissions: better utilization of fuel & renewable energy Reduction in electricity wheeling charges Increased security of supply Power quality support Reliability improvement Distribution infrastructure augmentation cost deferral
- 7. Modes of Power Generation
- 8. NEPRA Issues Sale of electricity Cheaper than IPP rates Inter-connection configurations for DG defined in Distribution & Grid Codes
- 9. Technical Problems Among the challenges of DG are Feeder protection & auto-reclose schemes Network voltage control, with varying generation output Dynamic stability of generators during network faults Power flow in two directions ‘ Loss-of-mains’ & ‘islanding’ issues
- 10. Two-directional Flows with DG Power flows in traditional network Power flows with distributed generation
- 11. Utility Company The distribution company would like to ensure: Consumer voltage levels within statutory limits Equipment thermal ratings not exceeded Switchgear & cable fault ratings not over-stressed Voltage disturbances (step-changes, flicker, harmonics) minimized In larger installations, this would require studies for: load flow fault levels protection coordination
- 12. Protection of DG Inter-connection ANSI # Function 21 Distance 25 Synchronizing 27 Under voltage 27N Neutral under voltage 32 Directional power 40 Loss of excitation 46 Neg. seq. current 47 Neg. seq. voltage 50 Instantaneous overcurent 50N Neutral overvoltage 51N Neutral instantaneous overcurrent 51V Voltage-restrained overcurrent 59 Overvoltage 59I Instantaneous overvoltage 59N Neutral overvoltage 60FL Voltage transformer fuse failure 67 Directional overcurrent 79 Reclosing 81 Frequency (under and over) 81R Rate of change of frequency 87 Differential LOM Loss of mains
- 13. Islanding
- 14. Anti-Islanding Protection Common passive methods include: Under/Over-Voltage Under/Over-Frequency Rate-of-Change-of-Voltage Rat-of-Change-of-Frequency (RoCoF) Voltage Vector Shift (phase displacement, phase jump)
- 15. 4 MW Cogeneration Installation
- 16. Other DG Projects Among some of the projects engineered are Pipe Mill, Landhi 4 MW Textile Mill, Sheikhupura 4 MW Board Factory, Korangi 2 MW Cable Factory, SITE 4 MW Cold Rolling Mill, Landhi 16 MW Chemical Plant, Bin Qasim 18 MW
- 17. Further Penetration of DG Depends on a number of factors: Knowledge of the subject to be disseminated New technical models to be developed & implemented Inter-connection standards for power & data interfaces to be further developed & harmonised True ‘avoided cost’ tariffs to be made available to compensate DG
- 18. Use of Aluminium Cables in Buildings & Industries
- 19. Background Building & Industry cabling – Copper Utility cabling – Aluminium A saving around 50% of power cabling costs in a project by substituting Cu with Al.
- 20. ? ? ? Why this saving has not been investigated before?
- 21. Cu/Al Cu Al Trends in LME Prices
- 22. Aluminium vs Copper 53 61….62 97…100 % Conductivity @+20oC IACS 23.0 23.8 16.6 10 -6 / o C Coef. Of thermal expansion 310 180..80 450..240 N /mm 2 Tensile strength (hard…annealed) 2.7 2.7 8.9 Kg/dm 3 Density AlMgSi Al Alloy E-Al Aluminium E-Cu Copper Unit Properties
- 23. Current-carrying Capacities 1.8 35 1.5 25 80 1.35 50 1.1 35 100 0.92 70 0.81 50 120 0.68 95 0.57 70 150 0.44 150 0.43 95 190 0.37 185 0.35 120 220 0.30 240 0.29 150 250 0.25 300 0.25 185 300 0.24 400 0.21 240 350 0.22 500 0.185 300 400 2.5 25 2.4 16 64 Voltage drop (mV/A/m) Size(mmsq) Voltage drop (mV/A/m) Size(mmsq) Aluminium Copper Amperes
- 24. Cost Advantages 582 189 35 771 25 80 803 253 50 1056 35 100 1054 373 70 1427 50 120 1573 472 95 2045 70 150 2118 713 150 2831 95 190 2677 884 185 3561 120 220 3231 1145 240 4376 150 250 3994 1485 300 5479 185 300 5378 1810 400 7188 240 350 6793 2220 500 9013 300 400 372 160 25 532 16 64 Rate(Rs./m) Rate(Rs./m) Size(mmsq) Rate(Rs./m) Size(mmsq) savings Aluminium Copper Amperes
- 25. Savings in Power Cabling Costs Rs.600 - 700/sft 100% Overall building electrical cost Rs.25 - 35/sft 4% - 5% Power cabling (Al size > 25mmsq) Rs.50 - 60/sft 8% - 10% Power cabling (Cu) Cabling cost (Rs./sft) Cabling costs (%)
- 26. Additional Factors a) Connectivity issues Oxidation in the presence of moisture. Dissimilar metals: Galvanic corrosion. Looseness of contact with thermal (load cycling) b) Brittleness Vibration
- 27. Bi-metallic Lug Cu Al Filled with anti-oxidation sealing compound
- 28. Conclusion Ex-WAPDA DISCO’s and now KESC are using aluminium conductor cables for distribution. Aluminum also used in other areas: Dry type transformers Bus bar trunking, etc.. Building and industries now need to look at power cabling with aluminium conductor.