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The emergency control for catastrophic disturbance in future power grids includes innovative approaches and methods proposed to improve the power system response to the emergency condition caused by catastrophic disturbances and countermeasures to prevent widespread power outage throughout the grid.

Voltage stability requires the continuing control of the total system's supply of reactive power during emergency situation. The supply of reactive power, however, can be curtailed by the action of rotor over-current protection or over-excitation limiter (OEL) in reducing the rotating unit reactive power output. Practical heat run tests shows that the timing of the activation of the OEL can be very conservative, resulting in earlier than necessary operation and system voltage collapse. Significant benefit can be achieved if the timing of the OEL activation can be delayed while ensuring sufficient margin is provided to avoid harming the rotor of the synchronous generator. This paper proposes a new thermal-based method to determine the timing of the OEL activation that is based on the thermal capacity of the rotor as the main indicator for limiting the excitation level of the synchronous generator. The proposed thermal based method is validated using the extensive simulations of a single-machine and the Nordic power system. Simulation studies show that the system voltage collapse can be delayed significantly by delaying the OEL activation without compromising the thermal capacity of the rotor if the proposed OEL setting is used.

Utilizing of the power system stabilizer (PSS) is a common approach to eliminate the low frequency power swings. The phase lag that must be compensated by the PSS to increase the damping of the system efficiently should be carefully obtained from the excitation system; but, the uncertainty in the excitation system data is an unavoidable issue and must be eliminated. This paper utilizes a comparative study of different AC excitation system models on a large-scale power grid to investigate the impact of uncertain information on the compensation angle and then PSS design and tuning. Moreover, this paper presented a new grouping scheme for the excitation systems based on similarity in the value of phase shift. Using this scheme, the excitation models of each group will share similar parameters for PSS tuning which can improve the stability for all excitation system models in the same group. So, the excitation system with inaccurate information can be replaced with an alternative model in the same group to be used for PSS tuning. The efficiency of the grouping scheme has been validated using the four-machine two-Area, The New England and Iran national power grid.

High impedance faults (HIFs) are part of the most common faults in distribution power system. The randomness, non-linearity and unstable nature of these faults have resulted in false detection and a growing concern, due to the involvement of electrical arcs. Contrary to typical power system faults, HIFs are more likely to result in casualties and therefore, are treated with grave importance. Low current magnitude is witnessed to be overcurrent relays biggest weakness and the main reason of conventional methods failure. In the presented paper, a new Fourier based detection scheme has been proposed. By designing two independent parallel algorithms, focusing on abnormal conditions and HIF signatures, this method benefits from simplicity, low computational burden and high accuracy in comparison to other conventional methods. Simulation of an IEEE standard distribution system has provided proof to this claim. Needles of extra equipment installation has also made the proposed method financially reasonable.

In this paper a practical approach to design an optimal robust Power System Stabilizer (PSS) is presented which improves the PSS dynamic performance facing uncertainty in its model parameters. Generally, the PSS system is a critical element in increasing the damping of the system in an emergency condition and it is necessary to strengthen its dynamic characteristics against any uncertainty in its model parameters. To model the uncertainty in the PSS, it is decomposed into two matched and unmatched types of uncertain components. The linear quadratic regulator (LQR) problem is then used to handle the matched component, while an augmented control is used to manage the unmatched component. To evaluate the robustness of the proposed optimal robust PSS system, the IEEE PSS1A PSS system model considering the reported uncertainties in its model parameters is used.

In this paper a new protection scheme for DC traction supply system is introduced, which is known as 'overload protection method'. In this scheme, with the knowledge of the number of traveling trains between two traction substations and the value of current which is drawn from each substation, the occurrence of short circuit fault is detected. The aforementioned data can be extracted and transmitted from railway traffic control system. Recently DDL ('Détection Défaut Lign in French', which means 'Line Fault detection') protection method is used in supply line protection. In this paper, the electrical system of railway system is simulated using the data obtained from Tabriz (located in Iran) Urban Railway Organization. The performance of the conventional and proposed protection schemes is compared and the simulation results are presented and then the practical measures and requirements of both methods are investigated. According to the results obtained, both methods accomplish satisfactory protection performance; however the DDL protection scheme is severely sensitive to the change in components and supply system parameters and it is also hard to determine the setting range of protection parameters of this method. Therefore, it may lead to some undesired operations; while the proposed protection scheme is simpler and more reliable.

In this paper, a new approach is presented to reduce the nonlinear characteristics of a stressed power system by reducing its second-order modal interaction through retuning some parameters of the generator excitation system. In order to determine the second-order modal interaction of the system, a new index on nonlinearity is developed using normal form theory. Using the proposed index of nonlinearity, a sensitivity function is formed to indicate the most effective excitation system parameters in the nonlinear behavior of the system. These dominant parameters are tuned to reduce the second-order modal interaction of the system and to reduce the index on nonlinearity. The efficiency of the proposed method is validated using a four-machine two-area test system. Simulation results show that a proper tuning of the excitation controller can reduce the second-order modal interaction of the system and can even improve the transient stability margin of the network.