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Abstract: Reactive flows compensation optimal design for losses reduction in MV automated distribution systems is a problem deeply studied in literature. In this paper, the design problem is formulated considering the new deregulated energy market. These new operational conditions allow the MV grid operator to consider the generation of reactive energy also as a service that can be sold to the transmission system above. In this case, the transmission system would be helped in all the working conditions in which a strong modulation of the reactive flow through the HV/MV node is required. Then, for the MV grid operator, the compensation system optimal design problem is therefore that of the search for the configuration (number, location and rated power of the capacitor banks) attaining the following main objectives: (i) to minimise power losses; (ii) to maximise the return on investment for the compensation system. Since results are strongly influenced by the parameter ‘economic value given to the reactive power’, RPEV, flowing from the MV network through the HV node, the optimisation problem has been parameterised for different values of RPEV and the total installed reactive power has been observed. A threshold value of this parameter has been identified. For values greater than the threshold, the proposed investment is economically profitable for the distribution grid operator, DGO. [Copyright &y& Elsevier]

Abstract: This paper proposes an efficient solution to the problem of reactive power flow tracing in electrical transmission networks. For such systems, the tracing techniques used for active power flows cannot be used straightforwardly, due to reactive power variations induced by the line reactances, these variations often being comparable to the powers delivered to the loads. In other words, as is well known, in transmission systems the reactive flows are strongly influenced by the inductive and capacitive effects of the network, making the tracing of power flow and allocation of losses more critical. In this paper, after discussing some methodological aspects, an approach based on the use of transmission line models differentiated on the basis of the reactive behaviour of the lines is proposed. These models allow the power contributions due to reactive losses to be evaluated separately and compared to the flows exchanged between generators and loads; moreover, their application does not require the introduction of nodes or additional links, as is the case with other methods proposed in the literature. The proposed tracing technique is then presented; the method is straightforward and does not require the creation or inversion of matrices of participation factors. The paper concludes with two applications, a 4 node system and the IEEE test system with 30 nodes. [Copyright &y& Elsevier]

Abstract: In this paper an iterative backward methodology to solve radial distribution networks with fixed voltage (PV) nodes and with constant power loads or mixed loads (with at least one component with constant power) is proposed. The method developed, although deriving conceptually from the backward/forward (b/f) methodology, presents only the backward phase in which all the network variables are evaluated. In the methods developed up until now for the solution of such systems, PV nodes are taken into account at the end of each iteration by evaluating, based on the known quantities of the network, the unknowns associated with PV nodes. In the methodology developed here the unknowns relevant to PV nodes are considered within the search process together with the unknown state variables. The proposed method at each iteration requires the solution of a network made up only of impedances; for such a system, supplied only at one node, the susceptances of the PV nodes are unknown as well as the currents in shunt impedances of the terminal buses. In order to solve such a system, a simple and efficient technique has been established. It allows the determination during the backward sweep of all the unknowns. The main and most important feature of the simulation of PV nodes with shunt reactance is the high precision of results related to reactive power injection at PV nodes. The applications indeed show that precision does not differ from that related to the use of the classical Newton–Raphson method; furthermore, also the number of iteration is similar with reduced CPU times. After having reported the models of PV nodes already existing in the literature in the field of b/f analysis methods, the general methodology for solving a radial network made up of impedances is briefly presented. The new analysis method and its implementation are then presented in detail. The results of the applications carried out show the good performance of the model in terms of both speed of convergence and, mainly, of precision. [Copyright &y& Elsevier]