Methods for calculating Available Transfer Capability (ATC) of the transmission systems may be grouped under Static and Dynamic methods. This paper presents a fast dynamic method for ATC calculations, which considers both Transient Stability Limits and Voltage Stability Limits as terminating criteria. A variation of Energy Function Method is used to determine the Transient Stability limit and the determinant of the Jacobian matrix of the system is used as an index to determine the Voltage Stability limit. A novel method is used to approximately calculate this determinant. Combining these two methods, an algorithm that calculates ATC, based on both Voltage and angle dynamic Stability is presented The advantage of this algorithm, besides considering both Voltage and angle dynamic Stability, is its high speed This-speed of calculation makes the algorithm a perfect candidate to be used in screening contingencies and determining those cases that need to be further analyzed. To demonstrate the validity, efficiency, and the speed of the new method, it is used to calculate ATC for numerical examples with 1, 3, 7 (CIGREE), 10,30 (IEEE) and US (Iowa State) buses.

With the rise in the penetration of inverter based distributed energy sources, grid codes say that converters should not be disconnected during the fault. These sources should also help the grid by reactive power injection. Power system grids are resistive inductive and the converter may be unstable during the fault. Converters use phase locked loop (PLL) to synchronize with the grid. PLL is not able to be stable during severe Voltage drop, so converters cannot ride through the fault and should be disconnected. In this paper a novel method based on virtual impedance is proposed to maintain the synchronization during severe Voltage drop. This method needs grid impedance estimation and virtually connects the converter to a point that has a stronger connection. By this novel method, during Voltage drop, the converter stays connected to the grid and injects reactive power. Simulation results in MATLAB verify the ability of proposed method in improving the Transient Stability of converter.

Nowadays, to having greater protection of the environment and due to the pollution caused by using fossil fuels and the limitation of these resources, the global orientation towards is renewable energy sources. As a sustainable form of energy, solar energy is really important, because that is almost the cheapest source of energy production in areas with high solar radiation potential; so global demanding of electricity generation can be supplied with using this technology. There is possibility of direct or indirect lightning strike on photovoltaic system equipment due to the installation of this equipment outdoors or on rooftops. In this paper, the Transient overVoltage crated by direct and indirect lightning strike to the photovoltaic frame in different parts of the photovoltaic system is investigated by an accurate modeling of the frame, pillars and ground of a photovoltaic system in EMTP-RV.

Due to space limitation along with the necessity to the increase of the substations, gas insulated substations (GISs) have been favorable option owing to their minimum required space for installation. One of the main challenge in this substation is very fast Transient overVoltage (VFTO) giving rise to the operation of disconnector. These waves travel through various components. Interestingly, along with waves, a wave is inducted on the ducts called Transient enclosure Voltage (TEV) or Transient ground potential rise (TGPR). This paper has been devoted to investigate these waves through modeling GIS and presenting some analytical approach. Subsequently, the impact of GIS design, CVT, arrester, and ground strap have been discussed through simulations in EMTP-RV. Finally, the impact of high frequency ground behavior has been discussed to show the importance of the design of grounding system in GISs from high frequency point of view.

Voltage Stability may be improved by various control functions. In this paper, it is shown that how High Side Voltage Control (HIVC) may be employed for this purpose. Two test systems, namely a 22- bus and IEEE U8-bus systems are used to demonstrate the proposed tuning strategy for HSVC control parameters.

The ability of network generators to maintain their synchronism after a fault depends on several factors, including the initial conditions of the system before the fault, so it can be expected that by changing the system variables, such as the angle of the generator rotors in the system, the system Stability can be against the fault. This change is possible by the Permanent presence of FACTS devices. The critical clearing time of fault as the most accurate criterion for Transient Stability evaluation can be the objective function of our optimization problem, but the determination of the critical clearing time, which involves the time domain simulation of the network along with the repeated examination of the fault occurrence It is time consuming to adjust the FACTS devices to a power system that is changing at any one time. In this paper, we present a new objective function based on the reduction of the Voltage angle difference between generators terminals, which greatly increases the speed of optimization, in order to improve the Transient Stability of smart grid by setting up the online FACTS devices. Minimizing this objective function by optimizing the FACTS is equivalent to maximizing Transient Stability. In addition to optimal tuning, optimal type, number and allocation of them are considered for long term. in determining the optimal number of these devices, the cost of investment is also considered.

In this article, a combined method is used to improving Transient Stability. In power systems, the maximum use of existing capacities along with the increased powers transferred through the transition lines make Transient Stability studies even more important. When the fault occurs, the kinetic energy of system is increased, and if the system kinetic energy exceeds a certain amount, system inStability will occur. Generator tripping is one of the most effective methods for improving Stability in case of serious faults. In this method tripped a number of units of a certain power plant unit for stabilizing the system. In fact, by removing the generator decrease the kinetic energy of the system so that Stability can be achieved. In generator tripping, for the above-mentioned, it should reach Stability by tripping the least generator possible. Due to its thermal limitations, fixed place of resistor bank and possibility of back swing, the braking resistor is less efficient than generator tripping. In combined method, system Stability against severe turbulence is reached through minimization tripping of generator units. In this method, we first decrease intensity of fault by applying braking resistor, and then, for the purpose of improving Transient Stability, it try to reduce kinetic energy by removing the least possible amount of producing the desired units at the right time.Simulations on 9-bus or 3-generator system were conducted, and satisfactory results were obtained.

This paper presents a new fault location method for radial distribution networks with distributed generations. The proposed fault location algorithm uses the Voltage and current data obtained by digital fault recorder installed at the head of the network main feeder, with or without the data from any digital fault recorders installed at DG connection points. The algorithm is based on fundamental frequency calculations and includes novel subroutines of current calculation of DG contained laterals and average loading factor and power factor estimation of the network transformers to solve the fault location problem. The method has been tested by simulation studies using EMTP on a 205-node 20 kV radial distribution network containing three DG's for different data acquisition scenarios. The results verify accuracy of the method under different fault conditions even with only one measuring point at the head of the main feeder.