Abstract
This paper presents and analyses a new method for the detection of the point of collapse and a new index for the definition of the distance of the voltage collapse point. This paper demonstrates that a point of a Newton-Raphson power flow becomes singular when the full sum of the partial derivate of the reactive power equations in relation to the voltage level is approximately constant. Numerical experiments using standard IEEE 14 and 57 bus systems show that the proposed method can compute the voltage collapse point using several different scenery of load increase, line or generator outages. The methodology proposed may be easily implemented in any power flow program.

Abstract
This paper proposes the use of available PMU measurements for establishing network observability State estimation is an important EMS application for providing real time, reliable and qualitative information on the system state. The observability analysis is the necessary function of the whole network state estimation. This paper addresses the incorporation of PMU measurements with the purpose of full network observability. The methodology is validated by the results on IEEE 14, 30 and 57 bus test system.

Abstract
Performance indices are used to rank the impact of contingencies in power system. security studies. In this paper it is proposed a new approach to the use of performance indices to contingencies screening. The developed methodology produces a screening and classification of the system outages. The developed technique is applied to a test power system and the results obtained were analyzed. Finally, some conclusions that provide a valuable contribution to the understanding of the power system security analysis are pointed out.

Abstract
Sabilizing control for power system stability has been applied to generators equipped with excitation controller and speed governor. Recently, power electronics-based control devices have been the focus of research and development for the improvement of dynamic stability. Power electronics control devices are utilized for control of the power flow on a transmission line or the reactive power in a power system. In this paper it will be presented a thyristor controlled series compensation strategy to improve the dynamic voltage stability of an Electric Power System. In this study it was simulated a significant load demand disturbance in a test power network. The Automatic Voltage Regulator of the generating units, the Under Load Tap Changer and loads were taken into account. The simulation results were obtained using EUROSTAG software package.

Abstract
This paper presents a transient stability preventive control technique based on a hybrid method. In order to maintain the power system security it is evaluated the generators output power that should be shift from the most unstable synchronous machines to the undisturbed units. The reallocation of the generators output power is carried out using an optimal power flow program. The hybrid method is a very important tool for the transient stability analysis, since it allows a fast evaluation of the stability limits and margins. This approach can also easily accommodate detailed models of the network devices and protective schemes. In order to validate the established mathematical models it was studied the transient stability of the New England test power network. The results obtained with the proposed methodology were compared with the solutions produced by another numerical formulation, showing a very close agreement.

Abstract
Climate change has arrived: deep, at a global level and sometimes catastrophic. Experts blame the greenhouse gas effect, boosted by the combustion of fossil fuels, which releases these dangerous gases. The purpose of this paper is to analyze the importance of energy efficiency on fighting climate change and how it has been used throughout the world, particularly by Energy Services Companies, also known as ESCOs. © 2012 IEEE.