A study is being conducted to supply electricity to a developing 50-mi' area. At the peak of development, the density of the area load is expected to reach at 2,500 kVA/mi?the power factor can be assumed as 0.9 lagging and the load factor as 0.7. The primary voltage is planned at 13.2 kV. The primary feeders are planned as three-phase overhead lines with copper conductors. The conductor sizes will be #470 AWG copper for the main trunk and #4 AWG copper for the feeder (three-phase) laterals. The equivalent spacing of the conductors on the poles is 37 in (both main and lateral lines). For the planning process we will assume that there are 20 laterals per mi on each feeder. Also we will assume that, at the maximum peak load, the feeders become voltage drop limited and that the maximum allowed voltage drop is 3%. We want to find the more economical of two alternative substation configurations to supply the above load: (a) 4 feeders per substation and (b) 6 feeders per substation. Assume a fully developed area and that the substations cover equal canonical regions (e.g. square or hexagonal-shaped areas). Use Fig. 4.25 in Gnen first edition or Fig. 4.34- 35 in third edition and, for each alternative configuration, calculate the number of substations needed to cover the entire area, the total number of annual energy losses on the primary feeder (include the laterals, assume that each substation operates under maximum load) and the total mileage of overhead line needed to cover the load. Compare. Calculate the total annual cost to own and operate each of the proposed distribution schemes. Use the cost data below and an annual carrying charge of 15%. What is the least costly scheme annually? What is the largest cost determinant for the previous question? 1. Energy Cost: $0.07/kWh 2. Substation Cost (each substation): Site Cost and other Initial and Fixed Expenses: $300,000; Substation Entry Bus Work: $200,000; Substation Transformer**: $15/VA; Substation Exit Feeder Bus Work: $50,000 per primary feeder; Maintenance and Operation (per year): $2,000+50.05/kVA+$500/primary feeder. 3. Primary System Cost: Material and Construction: $15,500 per mi of three-phase line; Maintenance and Operation (per year): $100 per mi of three-phase line. 1 The total substation transformer capacity must be 20% above the expected maximum peak demand of the substation (e.g. an expected utilization factor of 80%). A study is being conducted to supply electricity to a developing 50-mi' area. At the peak of development, the density of the area load is expected to reach at 2,500 kVA/mi?the power factor can be assumed as 0.9 lagging and the load factor as 0.7. The primary voltage is planned at 13.2 kV. The primary feeders are planned as three-phase overhead lines with copper conductors. The conductor sizes will be #470 AWG copper for the main trunk and #4 AWG copper for the feeder (three-phase) laterals. The equivalent spacing of the conductors on the poles is 37 in (both main and lateral lines). For the planning process we will assume that there are 20 laterals per mi on each feeder. Also we will assume that, at the maximum peak load, the feeders become voltage drop limited and that the maximum allowed voltage drop is 3%. We want to find the more economical of two alternative substation configurations to supply the above load: (a) 4 feeders per substation and (b) 6 feeders per substation. Assume a fully developed area and that the substations cover equal canonical regions (e.g. square or hexagonal-shaped areas). Use Fig. 4.25 in Gnen first edition or Fig. 4.34- 35 in third edition and, for each alternative configuration, calculate the number of substations needed to cover the entire area, the total number of annual energy losses on the primary feeder (include the laterals, assume that each substation operates under maximum load) and the total mileage of overhead line needed to cover the load. Compare. Calculate the total annual cost to own and operate each of the proposed distribution schemes. Use the cost data below and an annual carrying charge of 15%. What is the least costly scheme annually? What is the largest cost determinant for the previous question? 1. Energy Cost: $0.07/kWh 2. Substation Cost (each substation): Site Cost and other Initial and Fixed Expenses: $300,000; Substation Entry Bus Work: $200,000; Substation Transformer**: $15/VA; Substation Exit Feeder Bus Work: $50,000 per primary feeder; Maintenance and Operation (per year): $2,000+50.05/kVA+$500/primary feeder. 3. Primary System Cost: Material and Construction: $15,500 per mi of three-phase line; Maintenance and Operation (per year): $100 per mi of three-phase line. 1 The total substation transformer capacity must be 20% above the expected maximum peak demand of the substation (e.g. an expected utilization factor of 80%)