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A study was conducted on the effect of resistive lightning protection terminals in mitigating the lightning return stroke current. The investigation was performed on the recently developed R-L-C circuit model which allows resistive lightning protection terminals to be represented easily as circuit elements. The results show that the peak of the return stroke current was significantly reduced, thus demonstrating efficacy of the resistive lightning protection terminal and the utility of the R-L-C circuit model in such studies. Index Terms--Flashover, lightning protection terminal, peak current, return stroke current.

A dynamic model which describes the impulse behavior of concentrated grounds at high currents is described in this paper. This model is an extension of previous models in that it can successfully account for the surge behavior of concentrated grounds over a much wider range of current densities. It is able to describe the well known effect of ionization of soil as well as the observed effect of discrete breakdowns and filamentary arc paths at much higher currents. Results of verification against experimental results are also presented. Index Terms--Breakdown, concentrated grounds, ionization, sparking.

This paper describes the development of a new model for determining lightning return stroke current. An RLC circuit model was formulated to represent the lightning channel and was used to produce the return stroke current at ground matching median recorded values, while keeping reference to the current waveshape in the DU model. The proposed model was shown to be capable of matching the peak current, maximum di/dt, and front duration. Index Terms--Breakdown channel, corona sheath, inductance, lightning discharge, return stroke current, stepped leader.

This paper describes a new direct field orientation (DFO) scheme based on a modified flux observer using measured stator voltages and currents. The proposed approach addresses the problem of torque control of speed sensorless drives at low-zero speed, where rapid speed changes do not occur and signal frequency can approach zero. The scheme can maintain field orientation and stable torque control with simultaneous resistance and speed tuning taking place. Simulations and locked rotor experiments with torque measurements are used for verification. Index Terms - Direct field orientation, low-zero speed, speed sensorless, torque control, zero frequency.

This paper presents the design, simulation, implementation and performance evaluation of a computationally efficient and accurate digital distance relaying algorithm. Published historical data were used in the first phase for validation purpose. Sample results illustrating highly accurate fault impedance estimates for various conditions are reported. The second phase uses voltage and current signals generated by Alternative Transients Program (ATP) and a sample power system for various first-zone, second-zone and third-zone faults. Results of these studies confirming stability and computational efficiency of the algorithm are presented and discussed. In the third phase, a prototype of the relay was developed and tested using real-time fault data generated from physical models of the transmission lines. Oscillographs for these conditions were recorded. Results of these tests indicating high speed relay operation are also discussed. The performance evaluation studies reported in this paper conclusively demonstrate that the new algorithm provides fast and accurate fault impedance estimates for the three-zone protection of transmission lines. Key words: performance evaluation, digital distance relay

A new method, which simulates the lighting channel as a series network of R-C circuits, has been proposed by the authors. It successfully calculates the return stroke current with various added resistance values at the base of the lightning channel. The calculation shows that the peak current and current risetime along the channel are strongly influenced by the added resistance element at ground level. However, the larger voltage across this resistance element may cause the flashover along its surface and result in failure of current limiting. This paper describes the analysis and simulation of a novel method of current sharing following the termination of a lightning stroke onto a resistive lightning protection terminal. Such a system of resistance elements is essential to ensure that surface flashover does not occur across lightning rods and current limiting is successful. Index Terms--A resistive lightning protection terminal, flashover voltage, lightning discharge, peak current, return stroke current, voltage across rods, withstand voltage.

This paper describes a new method of calculation to determine the return stroke current by integrating all discharge currents along the channel. Using this method, the effect of added resistance in the lightning discharge channel is calculated. We find that the values of peak current, current risetime, and current-time derivative along the channel are strongly influenced by an additional resistance at the base of the channel. This result is of importance in the behavior of lightning protection terminal systems. Index Terms--Additional resistance, current risetime, lightning discharge, peak current, rate of change of current, return stroke current, stepped leader channel.

A chain of cascading LC sections consisting of series nonlinear inductors and parallel linear capacitors can be used to generate oscillating pulses. When a rectangular pulse is injected into the input of such a nonlinear inductive line (NLIL), the pulse undergoes modulation and exits at the output with oscillations in the waveform. This paper describes the implementation of high-voltage NLILs using commercial-off-the-shelf components. A pulser comprising of a storage capacitor and a fast semiconductor switch is used to provide the input pulse with approximate rectangular pulse shape. The design of the NLIL, which is a type of nonlinear lumped element transmission line (NLETL), is based on a NLETL circuit model developed earlier in-house. The nonlinear inductors made of ferrites are modeled using a simplified form of the Landau–Lifshitz–Gilbert (LLG) equation. A simple novel approach is proposed to determine the characteristic parameters in the LLG equation. Simulation results from the NLETL model are compared to the experimental results, and analyses on the voltage modulation and frequency content of the output pulses are performed. The use of crosslink capacitors in the line to modify the dispersive characteristics to enhance the performance is also investigated. With the results, the conditions and trends for producing oscillating pulses in NLILs are discussed. [ABSTRACT FROM AUTHOR]

A study was conducted on the effect of resistive lightning protection terminals in mitigating the lightning return stroke current. The investigation was performed on the recently developed R-L-C circuit model which allows resistive lightning protection terminals to be represented easily as circuit elements. The results show that the peak of the return stroke current was significantly reduced, thus demonstrating efficacy of the resistive lightning protection terminal and the utility of the R-L-C circuit model in such studies. [ABSTRACT FROM AUTHOR]

Presents a paper in which a direct field orientation (DFO) scheme was described, based on a modified flux observer using measured stator voltages and currents. Proposal of the approach for which the problem of torque control of speed sensorless drives at low-zero speed was addressed; How to overcome the problems; Effectiveness of field orientation of the DFO scheme.