Short Communication Discussion of ‘‘Optimal reconfiguration and capacitor allocation in radial distribution systems for energy losses minimization’’ by L.W. de Oliveira et al., International Journal of Electrical Power and Energy Systems 32 (2010) 840–848 Pooya Rezaei ⇑ , Mehdi Vakilian Sharif University of Technology, Tehran, Iran article info Article history: Received 5 October 2010 Accepted 29 April 2012 Available online 20 June 2012 Keywords: Capacitor placement Distribution system reconfiguration Load levels Loss reduction abstract This article indicates the accurate method for load level calculation to solve the power flow problem when capacitor reactive power is involved. Using the correct method causes some changes in the results and conclusion stated in the discussed paper on optimal reconfiguration and capacitor placement in radial distribution systems. Ó 2012 Elsevier Ltd. All rights reserved. The authors are to be complimented for their excellent paper [1]. They have provided reconfiguration and planning solutions for the third case study, 83-bus system. Two typical load curves are used to calculate system loads and perform power flow analy- sis for loss calculation. Different load levels and their time duration in hour per year are shown in Table 1. It should be noted that capacitor reactive powers should not be included as reactive loads when load factors are multiplied by loads on buses, as it is done in [2]. They should be added later after the multiplication process, since they do not change in light load or peak load conditions. They are independent of load factor, and their reactive power is either constant (fixed capacitors) or decided by distribution system operator (variable capacitors). Apparently this fact is not considered in [1]. Here, Table 2 shows the power flow analysis and total cost calculation for the proposed planning solution in Table 11 of [1] for the 83-bus system. Case 1 considers the capacitor reactive power as load on buses and different load levels in Table 1 are multiplied by it. In case 2, the load factors are first multiplied by loads, then capacitor reactive powers are added to the load on buses. Table 2 shows the results of case 1 which are the same as [1]. The results of case 2, which considers the load levels appropriately, show that C&R approach in [1] has given a slightly better answer than R&C approach, which is in contradiction to the statement and the following conclusion in [1]. References [1] de Oliveira LW et al. Optimal reconfiguration and capacitor allocation in radial distribution systems for energy losses minimization. Int J Electrical Power Energy Syst 2010;32:840–8. [2] Rezaei P, Vakilian M. Distribution system efficiency improvement by reconfiguration and capacitor placement using a modified particle swarm optimization algorithm, Electrical Power and Energy Conference (EPEC); 2010. p. 1–6. Table 1 Load levels, 83-bus system analysis (Table 9 of [1]). Load level L1 L2 L3 L4 Load factor (p.u.) Group-1 0.5 0.8 0.95 0.7 Load factor (p.u.) Group-2 0.8 0.95 0.6 0.7 Time (h) 2920 3650 730 1460 Energy price (US$/kWh) 0.06 0.06 0.108 0.06 Table 2 Total cost for Test Case 3 planning solution in [1]. (R&C) (C&R) Open switches 7, 34, 39, 42, 55, 63, 72, 82, 86, 88, 89, 90, 92 7, 34, 39, 42, 55, 63, 72, 83, 86, 88, 89, 90, 92 Capacitor placement 6(1), 19(2), 71(3), 79(3) 6(3), 19(3), 28(1), 31(3), 71(3), 79(3) Case 1 Case 2 Case 1 Case 2 Losses cost 144346.4 142237.8 139408.2 136350.3 Capacitor cost 7200 7200 12 800 12 800 Total cost 151546.4 149437.8 152208.2 149150.3 0142-0615/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijepes.2012.04.036 ⇑ Corresponding author. E-mail address: pooya.rezaei@gmail.com (P. Rezaei). Electrical Power and Energy Systems 42 (2012) 701 Contents lists available at SciVerse ScienceDirect Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes