Dc and ac fundamentals
- 1. DC and AC Fundamentals By S. P. Vasekar, Superintending Engineer, MSETCL
- 2. ?????? How we get power with voltage standard voltage? What is the standard voltage for residential supply? What are the voltage steps in between ?
- 3. Contents • Power System Overview – SLD – Load Served • Star and Delta Connection of load • Important Formulae • Power Triangle • Conversion Factor MVA to AMP • Transformer Rated Current • Voltage Regulation – Formula – Example insufficient data – Example and simulation • Line loss calculations • Capacitor Bank Calculations • Effect of capacitor on voltage regulation • Representation of load as R-L Circuit
- 4. Typical power system for discussion 15kV-25kV 400kV 220kV 132kV 2x200 MVA 33kVDistribution Transmission 33kV 11kV 440V 440/ 3 = 254 𝑉 132kV 2x50 MVA 2x500 MVA
- 5. Approximate Load Served and Corresponding Voltages SrNo Voltage Level Load/Generation 1) 11kV 2-5 MW 2) 33kV 5-20 MW 3) 132kV 20-100 MW 4) 220kV 100-300 MW 5) 400kV 300-1000 MW
- 6. Formula for 3-Ph Power
- 7. Formulae for 3ϕ Power • S = 3 𝑥 𝑉𝐿 𝑥 𝐼𝐿 • P = 3 𝑥 𝑉𝐿 𝑥 𝐼𝐿 𝑥 𝐶𝑂𝑆(ϕ) • Q = 3 𝑥 𝑉𝐿 𝑥 𝐼𝐿 𝑥 𝑆𝐼𝑁(ϕ) • S = 𝑃2 + 𝑄2 • S = V*I*
- 8. Power Triangle MW MVAR MVA V I ω P = 3VLILcos ϕ Q = 3VLIL sin ϕ S = 3VLIL ɸ
- 9. Conversion Factor MVA to Amp SrNo Voltage Level Ampere equivalent to 1 MVA 1. 400kV 1.44 2. 220kV 2.625 3. 132kV 4.375 4. 33kV 17.5
- 10. Table Showing HV and LV Amp For Transformers and ICT MVA Voltage kV Current Amp HV LV HV LV 25 132 11 109 1312 25 132 33 109 437 25 220 33 66 437 50 132 33 219 875 50 220 33 131 875 100 220 132 262 437 200 220 132 525 875 315 400 220 455 827 500 400 220 722 1312
- 11. Formula for Voltage Regulation of Transmission Line % Voltage Regulation = 𝑽𝒐𝒍𝒕𝒂𝒈𝒆 𝑵𝑳 − 𝑽𝒐𝒍𝒕𝒂𝒈𝒆 𝑭𝑳 𝑽𝒐𝒍𝒕𝒂𝒈𝒆 𝑭𝑳 𝑿𝟏𝟎𝟎
- 12. Representation of AC Quantity • Find voltage at receiving end – Sending end voltage 129kV – Line length 50 km – Line parameters 0.16 + j0.4 Ohm/km – Load on to be served • 50 MW • 30 MVAR
- 13. Representation of AC Quantity – Reformulation of the Problem • Find voltage at sending end – Receiving end voltage 124.5kV – Line length 50 km – Line parameters 0.16 + j0.4 Ohm/km – Load on to be served • 50 MW • 30 MVAR
- 14. Approximate Formula For Voltage Calculations Exact Calculations Approximate Calculations
- 15. Transmission Line Loss Calculations
- 16. Capacitor Bank Calculations • Let at 132kV level 15 MVAR bank is to be commissioned – what MVAR it will generate at 124kV – what MVAR it will generate at 140kV – what current it will draw from the system at 140kV – What would be the value of capacitor cell – What current will be drawn by a cell for voltage of 450 V – What would be the value of series inductor at the rate of 6% • Other Data is as below – Cell rating is 500 KVAR at 15 kV – Bank is divided between two star connected groups
- 17. Voltage improvement by Capacitor Bank In previous example of line voltage drop calculations if at receiving sub-station a capacitor bank of 25 MVAR commissioned. What would be it’s effect on voltage regulation and line losses
- 18. Representation of AC Quantity • Find voltage at receiving end – Sending end voltage 132kV – Line length 50 km – Line parameters 0.16 + j0.4 Ohm/km – R-L Load • 50 MW at 124.5 kV voltage • 30 MVAR at 124.5 kV voltage
- 19. Calculations and SLD 270 A