Alternative Continuation Method For Loading Margin Improvement And Transmission Losses Reduction

This paper presents an alternative methodology for loading margin improvement and total real power losses reduction by using a continuation method. In order to attain this goal, a parameterizing equation based on the total real power losses and the equations of the reactive power at the slack and generation buses are added to the conventional power flow equations. The voltages at these buses are considered as control variables and a new parameter is chosen to reduce the real power losses in the transmission lines. The results show that this procedure leads to maximum loading point increase and consequently, in static voltage stability margin improvement. Besides, this procedure also takes to a reduction in the operational costs and, simultaneously, to voltage profile improvement. Another important result of this methodology is that the resulting operating points are close to that provided by an optimal power flow program. © 2004 IEEE.1116Glover, J.D., Sarma, M., (1989) Power System Analysis and Design, , Boston, MA: PWS-KentReactive power compensation analyses and planning procedure (1989) CIGRE Publication, 90p. , Cigre Study Committee 38 Working Group 01 Task Force 03Sharif, S.S., Taylor, J.H., Hill, E.F., Scott, B., Daley, D., Real - Time implementation of reactive power flow (2000) IEEE Power Engineering Review, pp. 47-51. , AugKundur, P., (1993) Power System Stability and Control, p. 1176. , New York, McGraw-HillAlves, D.A., Da Costa, G.R.M., A geometric interpretation for transmission real losses minimization through the optimal power flow and its influence on voltage collapse (2002) Electric Power Systems Research, 62, pp. 111-116Voltage stability criteria, undervoltage load shedding strategy, and reactive power reserve monitoring methodology (1998) Western Systems Coordinating Council, Final Report, , Technical Studies Subcommittee, MaySeydel, R., (1994) From Equilibrium to Chaos: Practical Bifurcation and Stability Analysis, 2nd Ed., , New York: Springer-VerlagAjjarapu, V., Christy, C., The continuation power flow: A tool for steady state voltage stability analysis (1992) IEEE Trans. on Power Systems, 7, pp. 416-423. , FebCañizares, C.A., Alvarado, F.L., Point of collapse and continuation methods for large AC/DC systems (1993) IEEE Trans. Power Systems, 8, pp. 1-8. , FebChiang, H.D., Flueck, A.J., Shah, K.S., Balu, N., CPFLOW: A practical tool for tracing power systems steady-state stationary behavior due to load and generation variations (1995) IEEE Trans. Power Systems, 10, pp. 623-633. , MayFlueck, A.J., Dondetti, J.R., A new continuation power flow tool for investigating the nonlinear effects of transmission branch parameter variations (2000) IEEE Trans. on Power Systems, 15, pp. 223-227. , FebFette, M., Voss, J., Calculation of all algebraic solutions of electrical power systems by continuation method Proc. of the 1999 IEEE Power Tech Conf., , paper BPT99-419-16Wang, Y., Da Silva, L.C.P., Xu, W., Investigation of the relationship between ill-conditioned power flow and voltage collapse (2000) IEEE Power Engineering Review, PER-20, pp. 43-45Da Costa, G.R.M., Langona, K., Alves, D.A., A new approach to the solution of the optimal power flow problem based on the modified Newton's method associated to an augmented Lagrangian function Proc. of the 1998 International Conference on Power System Technology, pp. 909-913Van Cutsem, T., Vournas, C., (1998) Voltage Stability of Electric Power System, , Boston, Kluwer Academic PublishersSekine, Y., Takahashi, K., Ichida, Y., Ohura, Y., Tsuchimori, N., Method of analysis and assessment on power system voltage phenomena, and improvements including control strategies for greater voltage stability margins 7992 CIGRE Proc., , paper 38-206Tare, R.S., Bijwe, P.R., Look-ahead approach to power system loadability enhancement (1997) IEE Proceedings-generation, Transmission and Distribution, 144 (4), pp. 357-362Alves, D.A., Da Silva, L.C.P., Castro, C.A., Da Costa, V.F., Continuation fast decoupled power flow with secant predictor (2003) IEEE Trans. Power Systems, 18, pp. 1078-1085. , AugFreris, L.L., Sasson, A.M., Investigation of the load-flow problem (1968) Proc. of IEE, 115 (10), pp. 1459-147

Finding a suitable treatment solution for a leachate from a non-hazardous industrial solid waste landfill

The current study aimed at tackling the lack of effective treatment solutions for leachates from industrial solid waste landfills (ISWLs) through the development of a treatment train for a non-hazardous ISWL (NHISWL) leachate with low/moderate content of organics and salts and low biodegradability. The following technologies were tested: (i) coagulation using ferric chloride (FeCl3) or aluminium sulphate (Al2(SO4)3), (ii) biological oxidation, and (iii) chemical and electrochemical advanced oxidation processes (AOPs/EAOPs), including photo-Fenton oxidation using ultraviolet C (UVC) or ultraviolet A (UVA) radiation (PF-UVC or PF-UVA), anodic oxidation (AO), ozonation process and ozone (O3)-based processes. The best multistage treatment strategy included: (i) coagulation with FeCl3 for partial removal of organics (with direct impact on colour, odour and turbidity removal and biodegradability enhancement) and phosphorous, (ii) PF-UVC process for recalcitrant organics oxidation (with direct impact on colour and odour removal and biodegradability enhancement) coupled to a clarification step for removal of suspended solids, turbidity, iron and phosphorous, and (iii) biological process for removal of the generated biodegradable organics and of nitrogen compounds. Upon treatment, the NHISWL leachate fulfilled European and Portuguese requirements for discharge into aquatic systems, except for ammonium (and consequently for total nitrogen), pointing to the need to change the biological process conditions or add an air stripping step. The application of coagulation before the PF-UVC process has proved to be crucial for the fulfilment of the legislation requirements.info:eu-repo/semantics/publishedVersio

Coupling electrokinetic with a cork-based permeable reactive barrier to prevent groundwater pollution: A case study on hexavalent chromium-contaminated soil

This work proposes an eco-efficient treatment technology for the remediation of a kaolinite-based clay soil artificially contaminated with hexavalent chromium (50 mg Cr(VI) kg–1 soil), combining electrokinetics (EK) with permeable reactive barriers (PRB) composed of cork granules, the major by-product of cork stoppers production. This 100% natural and sustainable material can act as (i) an electron donor in the Cr(VI) reduction into trivalent chromium [Cr(III)], the less toxic state, and as (ii) a binder for the reduced Cr(III) on its pre-oxidized surface. The EK and Cr(VI) reduction efficiencies were assessed over 15 days as a function of the: (i) supporting electrolyte solution (demineralized water – DW, tap water, citric acid – CA, and sodium chloride – NaCl); and (ii) cork-PRB inclusion and position (near the anodic compartment, using direct current, or in the soil middle section, applying reversal polarity). Results showed that DW was the best supporting electrolyte solution, removing about 33% of total chromium (CrT) from the soil towards the anode, mainly under the Cr(VI) form, even though CA and NaCl presented higher electrical conductivity. Besides, nearly 67% Cr(VI) was reduced into less mobile Cr(III) only by soil-borne electron donor constituents, especially iron (> 6 g kg–1), which impaired the overall Cr migration due to the Cr(III) precipitation/adsorption over/onto the soil. Such reaction was boosted by CA and NaCl electrolytes, which increased H+ ions availability, reaching reduction efficiencies higher than 98%. When the cork-PRB was incorporated into the DW-driven EK process near the anode, the best position owing to the low pH, the Cr(VI) reduction and CrT removal efficiencies improved to about 97% and 42%, respectively. Furthermore, virtually no Cr(VI) migrated to the anolyte/catholyte, and less than 2% Cr(III) was found in the anodic chamber, being c.a. 40% of CrT retained in the cork-PRB as Cr(III) and c.a. 3%/55% of Cr(VI)/Cr(III) into the soil. Notwithstanding, the EK-PRB process can render polluted soil somewhat less dangerous and prevent the spreading of contamination to natural aquifers

Dinâmica da distribuição diamétrica de bracatingais na região metropolitana de Curitiba Dinamic of the diameter distribuition of Mimosa Scabrella Benth stands in the metropolitam region of Curitiba

O objetivo desta pesquisa foi estudar a dinâmica da distribuição diamétrica com relação à idade, em povoamentos nativos de bracatinga (Mimosa scabrella Benth.) localizados nos municípios da região metropolitana de Curitiba. Os dados utilizados provieram de um experimento de densidades iniciais, delineado em blocos ao acaso, constituído de cinco blocos e quatro tratamentos, perfazendo um total de 20 parcelas de 325 m², as quais foram remedidas às idades aproximadas de 4, 5, 6 e 7,5 anos. A densidade inicial sofreu redução para 2.000, 4.000 e 8.000 árvores por hectare quando o povoamento tinha 1 ano de idade. Deixou-se também uma parcela-testemunha em cada bloco, as quais não sofreram nenhum raleamento e tinham em média 25.000 árvores por hectare. Desses cinco blocos, um estava localizado na classe de sítio I, 2 na classe de sítio II e 2 blocos na classe de sítio III. Paralelamente, foram medidos os diâmetros e as alturas de todas as árvores em 124 parcelas temporárias distribuídas nos vários municípios da região metropolitana de Curitiba, representativos de povoamentos de bracatinga sob regime tradicional de cultivo e manejo, cobrindo idades de 3 a 18 anos, e as três classes de sítio. Dentre as funções de densidade de probabilidade testadas por Bartoszeck (2000), a S B de Johnson foi a de melhor desempenho, sendo, portanto, utilizada para a estimativa do número de árvores por classe diamétrica e por hectare e conseqüente construção das curvas de distribuição diamétrica para as inúmeras combinações de idade, sítio e densidades disponíveis. Através da observação visual das curvas sobrepostas, evidenciou-se que essas apresentaram assimetria para a direita e achatamento (curtose), com o aumento da idade. As curvas foram, então, comparadas analiticamente entre si, pelo teste qui-quadrado, o qual revelou a existência de diferenças significativas entre as curvas de distribuição diamétrica em diferentes idades.<br>The objective of this research was to study the behavior and dynamic of diameter distribution curves with respect to age, in native stands of bracatinga (Mimosa scabrella Benth) located in the metropolitan region of Curitiba, State of Parana, Brazil. The data came from a trial of densities, arranged in randomized blocks, with 5 blocks and 4 treatments, in a total of 20 plots (325 m²) remeasured at the approximate ages of 4, 5, 6 and 7.5 years. The initial density was reduced to 2000, 4000, 8000 trees per hectare when the stands were 1 year old. The control plots in every block, without any treatment , had in average,25000 trees per hectare at 1 year old. From these 5 blocks, 1 was located on site class I; 2 on site class II and 2 on site class III. Diameters and heights were also measured in 124 temporary sample plots scatered throughout several counties of the metropolitan region of Curitiba, representative of bracatinga stands under traditional cultivation and management with ages ranging from 3 to 18 years, and the 3 site classes. Among the tested distribuition functions by Bartoszeck (2000), the S B from Johnson was the one with the best performance, being used to estimate the number of trees per diameter class per hectare, and for constructing the diameter distribuition curves for the several possible combinations of age, site and initial density. The evolution of the distribution curves along the ages presented positive skewness and a flat distribution (Kurtosis) with the increasing age. These curves (estimated values) were compared by the chi-square test that indicated significant differences among diameter distribuition curves at different ages