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Distance protection of the electrical power system is analyzed in the paper. Electrical power transmission lines are divided into sections equipped with protective relaying system. Numerical protection relays use specialized digital signal processors as the computational hardware, together with the associated software tools. The input analogue signals are converted into a digital representation and processed according to the appropriate mathematical algorithms. The distance protection is based on local and remote relays. Hazard is the event: remote circuit breaker tripping provided the local circuit breaker can be opened. Coordination of operation of protection relays in time domain is an important and difficult problem. Incorrect values of time delays of protective relays can cause the hazard. In the paper, the time settings are performed using probabilistic fault trees with time dependencies (PFTTD). PFTTD is built for the above mentioned hazard. PFTTD are used in selection of time delays of primary (local) and backup (remote) protections. Results of computations of hazard probabilities as a function of time delay are given. [ABSTRACT FROM AUTHOR]

The application of the wavelet-based algorithm for arcing high-impedance fault detection medium-voltage (MV) distribution networks is presented in this paper. This paper describes continuation of research on HIF detection with particular reference to algorithm application in solidly grounded MV networks. The results obtained by use of the improved version of the algorithm are presented. The algorithm performance was tested using data obtained from staged HIFs in a real MV network as well as from EMTP-ATP simulations. Satisfactory results of the algorithm performance were observed for all examined HIF cases in which the ground fault current was greater than 3 A root mean square. The improved algorithm also proved to be more immune to transients generated during switching operations in protected feeders and to capacitor bank switching. [ABSTRACT FROM AUTHOR]

A new simple and effective algorithm of arcing fault detection in distribution networks with the application of a wavelet transform technique is presented in this paper. The protection algorithm developed observes the phase displacement between wavelet coefficients calculated for zero-sequence voltage and current signals at a chosen high-level frequency. The final decision in regards to feeder switching off (or alarm issuing) is met either with a deterministic logic scheme or with the use of a neural net trained especially for that purpose. The developed wavelet-based high-impedance fault (HIF) detector has been tested with Electromagnetic Transients Program-Alternative Transients Program (ATP)-generated signals, exhibiting better performance than traditionally used algorithms and methods. The protection method proposed may be used for HIF detection independent of the network neutral-point grounding mode. The scheme proved to be robust against transients generated during normal events such as feeder energizing and de-energizing as well as capacitor bank switching. [ABSTRACT FROM AUTHOR]