Protection of transmission lines is essential to ensure a correct operation of power systems. In this paper a pilot protection scheme, known as permissive overreaching transfer trip, is used. This structure combine two different protection relays: directional overcurrent relay, a backup protection for phase-earth faults, and distance relay for phase-phase faults. An intelligent method was developed to the optimal coordination of protection relays in meshed networks like transmission networks. The proposed method employs the genetic algorithm as optimization procedure that considers network characteristics (maximum load current and minimum fault current) and adjustment parameters of overcurrent and distance relays. Two testing networks, one of 8-bus and other of 39-bus, were used to evaluate the proposed method that obtained feasible and good solutions for the coordination problem.
This paper proposes a novel one-port passive circuit topology consisting of a two-dimensional network of resistors and capacitors, which can be used as a fault-tolerant building block for analog circuit design. Through an analytical procedure, the network is shown to follow simple first-order admittance dynamics. A Monte Carlo method is employed to describe the effect of simultaneous faults (short or open circuit) in random network elements in terms of confidence bounds in the frequency-domain admittance profile. Faults in 10% of the elements resulted in only minor changes of the frequency response (up to 3.9 dB in magnitude and 12.5 ∘ in phase in 95% of the cases). An example is presented to illustrate the use of the proposed RC network in the faulttolerant design of a low-pass filter.
This paper is concerned with the control of linear systems with switched actuators subject to lower bounds on dwell times. The problem addressed herein consists of driving the system state to a desired periodic trajectory through suitable perturbations in the switching times. For this purpose, a linearization procedure is derived to describe the relationship between the switchingtime perturbations and the resulting state trajectory. This procedure allows the constrained predictive control problem to be cast in the form of a convex quadratic program, which is a key contribution of the present work. Simulation examples with single-input and two-input models are presented for illustration. In all cases, the system state is driven to the desired trajectory with satisfaction of the dwell-time constraints on the switched input signal.
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