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Bashewa Rural: Build interconnectors for the Akasia feeder

Bashewa Rural: Build interconnectors for the Akasia feeder. Compiled by: Koena Mojapelo Sune Cotzee 011 747 6504 (Tel) and 021 980 9569 (Tel)

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Bashewa Rural: Build interconnectors for the Akasia feeder

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  1. Bashewa Rural: Build interconnectors for the Akasia feeder Compiled by: Koena Mojapelo Sune Cotzee 011 747 6504 (Tel) and 021 980 9569 (Tel) Mojapek@eskom.co.zaCoetzeSU@eskom.co.za

  2. Contents Background Problem statement Load forecast Proposed alternatives Cost Recommendation

  3. Problem Statement The Akasia feeder is configured in such a way that it is unnecessarily long and as a result the losses in the feeder are high. The minimum MV voltage on the Akasia feeder is 0.85p.u and this is below the permissible limits as per NRS048-2.

  4. Problem Statement p.u sending-end Voltage axis p.u daily load axis • At peak load the sending end voltage on the Bashewa transformer ranges between 0.99-1 p.u.

  5. Background • The Akasia feeder (BA) is supplied from a 1x10MVA, 88/11kV transformer at Bashewa Rural. • There are three feeders in total which are supplied from Bashewa Rural: viz Akasia (BA), Geelhout Feeder (BG), Jakaranda Feeder (BJ). • The backbone of Akasia feeder is 19km long and is built with Mink conductor. • There are 154 customers (residential and agricultural) on the Akasia feeder with an installed load of 8231kVA. • The MD on the BA feeder was 2.7MVA in 2008

  6. Load Forecast • There is no history of MD on the Akasia feeder, MD data is only available from 2006. • The load forecast is based on history of actual installed trfr’s on the feeder over a period of 5yrs since 2004. • The average installed load over the 5yr period was calculated as 348kVA. • Load growth is based on a fixed diversified peak contribution of 113kVA annually.

  7. Proposed alternatives Immediate network change: Change the tap settings of Bashewa substation Trfr. • Set the setpoint @ 103% and the bandwidth at +-1.4% Comments • MD 2008 = 2.7MVA • The minimum voltage is improved from 0.85p.u to 0.88p.u.

  8. Proposed alternatives Alternative 1: Install a voltage regulator on the BA feeder(2009) • Install a voltage regulator at BA80 Comments • MD 2009 = 2.8MVA • The voltage improves from 0.88p.u to 0.95p.u. • The capacity created is insufficient.

  9. Proposed alternatives Alternative 2A: Build inter-connectors on the Akasia feeder (2009) • Build 714m Fox inter-connector from BA60/7/5 to BA147/25. • Open the existing links at BA119 to create a N/O point. • Build a 380m Fox inter-connector from BA60/7/7 to BA177/22. • Open the existing links at BA148 to create N/O point. • Re-stencil the feeder. Comments • The backbone length is reduced from 19km to 12km resulting in a reduction of 100kVA in losses. • The voltage is improved from 0.88p.u to 0.93p.u.

  10. Proposed alternatives Alternative 2B: Build inter-connectors and install a shunt capacitor(2009) • Build 714m Fox inter-connector from BA60/7/5 to BA147/25. • Open the existing links at BA119 to create N/O point. • Build a 380m Fox inter-connector from BA60/7/7 to BA177/22. • Open the existing links at BA148 to create N/O point. • Install a 300kVAr capacitor Comments • PF = 0.96 during peak load. • Voltage improves 92.31% to 93% • Spare capacity created = 0 • The power factor is improved from 0.96 to 0.97.

  11. Proposed alternatives Alternative 2C: Build inter connectors and install a voltage regulator (2009) • Build 714m Fox inter-connector from BA60/7/5 to BA147/25. • Open the existing links at BA119 to create N/O point. • Build a 380m Fox inter-connector from BA60/7/7 to BA177/22. • Open the existing links at BA148 to create N/O point. • Install a voltage regulator at BA55. • Re-stencil the feeder. Comments • The voltage is improved from 0.88p.u to 0.97p.u • Point spare capacity created = 450kVA. • Distributed capacity created = 1.2MVA.

  12. Proposed alternatives Alternative 3: Rebuild the Akasia backbone with Hare conductor (2012) • Rebuild 11km of Mink and Fox conductor with Hare from BA1 to BA156/23. Comments • MD in 2012 = 3.12MVA • Point spare capacity created = 1.5MVA • Distributed spare capacity = 2.5MVA • Maximum stress = 62.13% • From a construction point of view this option is not practical as it is going to involve a lot of break and build and many customers will be affected by the outages. Point Spare capacity = 1.5MVA Distributed spare capacity = 2.5MVA Maximum stress = 62.13% Point Spare 2012 = 425kVA Distributed spare capacity 2012 = 900kVA Maximum stress = 69.56%

  13. Proposed alternatives Blue Horizon 1.8MVA Emri 28MVA Proposed substaton site Alternative 4: Deload a section of the Akasia feeder to a proposed new substation in the Boschkop Area (2012) Background • Three applications were received on the Tweedracht Tiegerspoort (TT) network. • These applications cannot be accomodated on the existing network and it is proposed that a new substation be built to connect them. • If the customers accept the quotes sent to them, the proposed substation can be completed by 2012. • It is proposed that the TT feeder be split into three sections in order to feed Blue Horizon and Borotech. • Akasia feeder has a N/O point with the TT feeder and it is proposed that this N/O point be closed and a section of Akasia be deloaded to the proposed substation via a section of TT. Borotech 800kVA

  14. Proposed alternatives Blue Horizon 1.8MVA Emri 28MVA Proposed substation site Alternative 4: Scope of work • From the proposed substation, build 900m Hare line to inter-connect with the Tiegerspoort feeder at TT130/26. • Install a tri-switch at TT128 to create a N/O point. • Close the N/O point between the Akasia and Tiegerspoort feeder at BA201. • Open the links at BA187. • Relocate the voltage regulator installed at TT62 to TT131/9 • Rebuild 2.3km of Fox conductor from TT130 to TT 130/26. Comments • The TT feeder will be split into three sections, viz TT LZ1, TT LZ2, TT LZ3. • TT LZ1 is the portion that will remain at Tweedracht substation. • A new feeder will be built from the new substation to inter-connect with TT LZ3, and this will form New feeder 1 and Borotech will be supplied from this feeder. • BA LZ2 will be fed from the new substation via TT LZ3. • A second feeder will be built from the new substation to inter-connect with TT LZ2 and Blue Horizon will be fed from this new feeder. Borotech 800kVA Point spare capacity = 600kVA Distributed spare capacity = 1.5MVA Maximum stress = 63.22% Point Spare capacity = 800kVA Distributed spare capacity = 2.4MVA Maximum stress = 52.9%

  15. Cost: Alternative 2C: Build inter-connectors and install a voltage regulator(2009)

  16. Recommendation • Change the Bashewa transformer tap settings as an immediate solution. • Implement Alternative 2C as a short-term solution • Implement Alternative 4 as this is a long-term solution that will allow for future load growth in the area.

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