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Load Flow Modelling Service Project results 30 September 2002

Load Flow Modelling Service Project results 30 September 2002. Mick Barlow Srdjan Curcic. Content. Project objectives Modelling assumptions Some potential issues with the proposed approaches to allocation of losses Illustration of the key results. Project objectives.

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Load Flow Modelling Service Project results 30 September 2002

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  1. Load Flow Modelling ServiceProject results 30 September 2002 Mick Barlow Srdjan Curcic

  2. Content • Project objectives • Modelling assumptions • Some potential issues with the proposed approaches to allocation of losses • Illustration of the key results

  3. Project objectives • Power Technologies Int. has been commissioned to assist the assessment procedure of modification proposals P75 and P82, specifically: • to perform calculations of TLFs & TLMs for a specified number of SPs for P75 & P82 • to present the results in a form suitable for the assessment procedure; and • to draw attention to potential issues with the fundamentals of the two marginal approaches proposed (P75 & P82) • This presentation contains an appropriate selection of the project results

  4. Modelling assumptions • MW injections are calculated from the metered volumes assuming they are constant (average) • Power factors published in NGC’s SYS are used to calculate reactive power injections • It is assumed that “offtake” metered volumes/injections are accurate and then the “delivery” volumes/injections are calculated to balance “offtake” metered volumes/injections and calculated variable active power system losses, while maintaining relative “deliveries” among the generators (DICTATED BY DATA QUALITY)

  5. Modelling assumptions • Load flow assumptions: • Generation P is calculated as described above • Generation Q is calculated automatically by setting voltage target to 1.03 p.u. • Load P is calculated from the metered volumes • Load Q is calculated from typical power factors given in the NGC’s SYS • Transformer tap changer are set according to information in the NGC’s SYS for each voltage level • Transformer target voltage is set to produce reasonable voltage profile (between 0.97 and 1.03 p.u.) • SVC’s target voltage is set to values recommended in the NGC’s SYS

  6. Modelling assumptions • AC load flow calculations are using the standard NGC’s slack at Cowley • PTI’s PSS/E-OPF is used for calculating marginal TLFs • Out of TLFs obtained for active power injections and reactive power injections, unique TLFs are calculated that relate only to active power injections, while providing for the total losses incurred from a node TLFij = (TLFPij Pij + TLFQij Qij) / Pij

  7. Modelling assumptions • On the basis of information in the NGC’s SYS, the fixed losses are assumed to be 200MW (peak), 180MW (trough) and 190MW (other periods – Autumn) • For the purpose of calculating TLMs, these fixed losses are smeared across generators, proportionally to their power output

  8. Issues with proposed allocation of losses Slack node – An issue with the marginal TLFs approach: • The choice of the slack node potentially matters more that initially expected :

  9. Issues with proposed allocation of losses Slack node Network & metered volumes are for 22 January 2002 Comparison is between slack node at Cowley and at Thorpe Marsh Illustrative example: Assume a generation metered volume of 1000MWh and a TLM of 0.94. That would attribute 60MWh of losses to this generation. Due to the indicated change in slack node this 60MWh of losses would change for 9.23%, on average.

  10. Issues with proposed allocation of losses • The sensitivity analysis to introduction/variation of power factors has been done in an simple exercise: For 02 January 2002 network and metered volumes two cases were calculated: • P.F. = 1 for all demand nodes • P.F. by NGC’s SYS Power factor

  11. Issues with proposed allocation of losses Power factor • At the level of TLFs the effect was much more tangible. This indicates: • that reactive powers should not be ignored; and • a possible need for further consideration

  12. Summary: Issues with proposed allocation of losses • There are some issues arising from the modelling • TLFMG, nevertheless, have confidence in the modelling results

  13. Illustration of key resultsP75

  14. P75 (T1)Base cases02 Jan. 02 (SP36) - Peak01 Aug. 01 (SP8) - Trough10 Oct. 01 (SP25) – Week day daylight11 Oct. 01 (SP11) – Week day night 13 Oct. 01 (SP25) – Weekend daylight 14 Oct. 01 (SP11) – Weekend night

  15. GSPG and TNUoS (gen) zones

  16. Change P75 introduces – an example (based on marginal, GSPG zone, ½ h TLFs) 02 January 2002 North South

  17. Demand TLMs for P75 (based on marginal, GSPG zone, ½ h TLFs) North South

  18. Change P75 introduces – an example (based on marginal, TNUoS (gen) zone, ½ h TLFs) 02 January 2002 North South

  19. Generation TLMs for P75 (based on marginal, TNUoS (gen) zone, ½ h TLFs) North South

  20. P75 (T1) - Summary • Introduction of Modification Proposal P75 would result in variable TLMs: • over time; and • across country with an overall, indicative variation between 0.95 and 1.06 for demand and between 0.94 and 1.09 for generation

  21. P75 (T2)Variation of TLMs over time 02 Jan. 02 (SP8 & SP36) – Peak day01 Aug. 01 (SP8 & SP36) – Trough day 10 Oct. 01 (SP1 – SP48) – Week day11 Oct. 01 (SP11) – Week day night 13 Oct. 01 (SP25) – Weekend daylight 14 Oct. 01 (SP11) – Weekend night

  22. P75: GSPG zone TLMs over sample time period - demand North South

  23. P75: TNUoS (gen) zone TLMs over sample time period - generation North South

  24. P75: GSPG zone TLMs over a day - Demand 10 October 2001 South North

  25. P75: TNUoS (gen) zone TLMs over a day - Generation 10 October 2001 South North

  26. P75 (T2) - Summary • Introduction of Modification Proposal P75 would result in daily variation in TLMs of up to approximately 0.03 for demand and 0.045 for generation (the exception is TNUoS zone 5 with reversible hydro plants where the variation is up to 0.065) on a typical autumn working day

  27. P75 (T3)Sensitivity to network configurationIndicative/Intact/Representativenetworks for the following SPs:02 Jan. 02 (SP36) - Peak01 Aug. 01 (SP8) - Trough10 Oct. 01 (SP25) – Week day daylight11 Oct. 01 (SP11) – Week day night 13 Oct. 01 (SP25) – Weekend daylight 14 Oct. 01 (SP11) – Weekend night

  28. P75: GSPG zone TLMs - Demandsensitivity to network configuration 02 January 2002 (peak) North South

  29. P75: TNUoS (gen) zone TLMs - Generationsensitivity to network configuration 02 January 2002 (peak) North South

  30. P75: GSPG zone TLMs - Demandsensitivity to network configuration 01 August 2002 (trough) North South

  31. P75: TNUoS (gen) zone TLMs - Generationsensitivity to network configuration 01 August 2002 (trough) North South

  32. P75: GSPG zone TLMs - Demandsensitivity to network configuration 10 October 2001 (weekday daylight) North South

  33. P75: TNUoS (gen) zone TLMs - Generationsensitivity to network configuration 10 October 2001 (weekday daylight) North South

  34. P75: GSPG zone TLMs - Demandsensitivity to network configuration 11 October 2001 (weekday night) North South

  35. P75: TNUoS (gen) zone TLMs - Generationsensitivity to network configuration 11 October 2001 (weekday night) North South

  36. P75: GSPG zone TLMs - Demandsensitivity to network configuration 13 October 2001 (weekend daylight) North South

  37. P75: TNUoS (gen) zone TLMs - Generationsensitivity to network configuration 13 October 2001 (weekend daylight) North South

  38. P75: GSPG zone TLMs - Demandsensitivity to network configuration 14 October 2001 (weekend night) North South

  39. P75: TNUoS (gen) zone TLMs - Generationsensitivity to network configuration 14 October 2001 (weekend night) North South

  40. P75 (T3) - Summary • Network configuration can have an effect on TLMs: • while there is almost no difference between intact and representative networks, • there is a tangible difference between indicative and intact networks

  41. P75 (T4)Sensitivities to constraints02 January 2002 (base case)02 January 2002 (constrained case) 5 double circuits restricted for 20% below the flow level in base case

  42. P75: GSPG zone TLMs - Demandsensitivity to constraints Losses: 758.5MW (base case), 573 (constrained case) North South

  43. P75: TNUoS zone TLMs - Generationsensitivity to constraints Losses: 758.5MW (base case), 573 (constrained case) North South

  44. P75 (T4) - Summary • Constraints may have an impact on TLMs

  45. P75 (T5)Comparison of Generation TLFs/TLMs and Demand TLFs/TLMs at the same node

  46. P75: Comparison of Generation/Demand Zonal TLFs/TLMs Node: Rye House GSPG zone: 7 TNUoS zone: 10 SP: 02 January 2002, SP36

  47. P75 (T5) - Summary • Discrepancies between TLMs for generation and demand at a node are not greatly exacerbated if generation and demand zones are different from one another • Only one node has been assessed and this may not be representative

  48. P75 (T6)Comparison of Nodal TLFs/TLMs with Zonal TLFs/TLMs

  49. P75: Comparison of Nodal/Zonal TLMs (Demand) 02 January 2002 Winter peak (SP36)

  50. P75: Comparison of Nodal/Zonal TLMs (Generation) 02 January 2002 Winter peak (SP36)

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