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This paper presents a heuristic constructive algorithm (HCA) for optimal capacitor placement on distribution systems. This is a nonlinear mixed integer optimization problem. In the proposed approach, the integer variables are represented using sigmoid function, thus interior point optimal power flow formulation can be applied to obtain sensitivity indexes based on Lagrange multipliers, reactive power, and bus voltage. The methodology is applied to two power distribution systems, and the results are compared with those obtained using a genetic algorithm approach. Index Terms--Heuristic programming, Lagrange multipliers, optimal capacitor placement, optimal power flow.

This work presents a new formulation for the power flow problem, with explicit representation of the neutral conductor and grounding. This methodology has been named the four-conductor current injection method (FCIM). The Newton-Raphson method is applied to solve the set of nonlinear current injection equations that are derived using phase coordinates, and the complex variables are written in rectangular form. The proposed algorithm can be used to analyze both balanced and unbalanced systems, meshed or radial, with controls and distributed generation, and is shown to be very efficient and robust for large scale systems. Index Terms--Current injection method, distributed generation, distribution systems, four-wire systems, induction machine modeling, three-phase power flow, unbalanced operation.

This paper presents a new approach for distribution system reconfiguration (DSR) based on optimum power flow (OPF) in which the branch statuses (open/close) are represented by continuous functions. In the proposed approach, all branches are initially considered closed, and from the OPF results, a heuristic technique is used to determine the next loop to be broken by opening one switch. Then the list of switches that are candidates to be opened is updated, and the above process is repeated until all loops are broken, making the distribution system radial. This paper includes results and comparisons on test systems utilized in three classical papers published in the technical literature, as well as in a previous paper by the authors. Results obtained on a real large-scale distribution system are also presented. Index Terms--Heuristic optimization technique, losses, optimum power flow (OPF), radial distribution networks, reconfiguration.

This paper presents an optimum power flow (OPF) modeling algorithm that uses the primal-dual interior point technique to determine the best investment strategy in the transmission line expansion problem. In the proposed method, the expansion decision (0 or 1) is mitigated by using a sigmoid function, which is incorporated in the OPF problem through the modified dc power flow equations. The investment decision is taken using a new heuristic model based on good sensitivity produced by the OPF results. Additionally, the transmission power losses are considered in the network model. The proposed methodology has been compared with methods available in the literature, using both a test system and an equivalent of the southeastern Brazilian system. Index Terms--Heuristic algorithm, interior point method, sigmoid function, transmission network losses, transmission system expansion.

This paper presents a reconfiguration algorithm that is specially suited to large-scale distribution systems. The algorithm uses a heuristic strategy that starts with the system in a meshed status, with all maneuverable switches closed. The choice of the switches to be opened is based on the calculation of the minimum total system losses, using a load-flow program. A refinement on this procedure, based on branch status exchange, is described. The paper includes results and comparisons on test systems utilized in three classical papers published in the technical literature. Results obtained on a real large-scale distribution system are also presented. Index Terms--Heuristic optimization technique, losses, power system restoration, radial distribution networks, reconfiguration.

As a safety measure for certain applications in Nuclear. Power Stations, cable trays must be wrapped with a fireproof material. In this paper a new implementation of a thermal model is presented, suitable for the determination of the ampacity derating of electric cables in wrapped trays. Model simulation predictions have been compared with field tests to validate the model. Better agreement between simulations and experimental results is obtained when the standard procedure to determine the power loss in the cable mass is modified to account for the actual measured height of the cable mass in the tray. Keywords: Ampacity, Insulated Conductors, Fire Protection, Thermal Influences.

This letter describes a new voltage controlled bus (PV bus) representation in connection with the three-phase current injection method-TCIM of power flow analysis. This representation requires an augmented system of linearized equations to incorporate the reactive power as a dependent variable. Tests and comparisons between the former and the new approach are described and the improved stiffness of this new proposition is demonstrated. Index Terms--Current injection power flow, distribution power flow, PV buses, unbalanced power flow.

This paper presents a new sparse formulation for the solution of unbalanced three-phase power systems using the Newton--Raphson method. The three-phase current injection equations are written in rectangular coordinates resulting in an order 6n system of equations. The Jacobian matrix is composed of 6 x 6 block matrices and retains the same structure as the nodal admittance matrix. Practical distribution systems were used to test the method and to compare its robustness with that of the backward/forward sweep method. Index Terms--Unbalanced Power Flow, Current Injection Power Flow, Newton Raphson Power Flow, Distribution Power Flow.

This paper presents the development of mathematical models for thyristor controlled series compensator (TCSC), for voltage regulator devices and for remote bus voltage control that are suitable to be used with the three-phase current injection method (TCIM) for power flow calculation. TCIM is a Newton method where the equations are written in rectangular coordinates resulting in a 6n x 6n Jacobian matrix. The representation of a control device requires an augmented system of equations to incorporate the additional relationship between each control action and the controlled variable, resulting in an augmented Jacobian matrix. Practical distribution systems are tested and the effectiveness of the proposed formulation is demonstrated. Index Terms--Current injection power flow, distribution power flow, series capacitors, unbalanced power flow, voltage control.