جستجوی مقالات مرتبط با کلیدواژه « حفاظت شبکه توزیع » در نشریات گروه « برق »

The rapid growth of distributed generations (DG) in distribution grids brings new challenges in the protection coordination of overcurrent relays. So far, various adaptive techniques have been addressed to solve DG units’ mis-coordination problem, however, the un-predictable penetration of installed DG units highlights the importance of a penetration-free methodology. This study presents a novel offline, quick, applicable and cheap solution which guarantees protection coordination for any penetration and location of DG units. To do so, first, under different DG penetration levels and locations, the conventional protection performance is studied to discover the worst mis-coordination cases. Next, according to relays standards, the characteristic curve of the back-up relay is modified such that it can maintain coordination in all worst cases. The proposed methodology is applied to a power distribution network equipped with numerous DG units. The results successfully prove the effectiveness of the proposed method. This fact makes this method an attractive option for distribution systems with DG units.

Integration of distributed generation (DG) into distribution networks causes some protection challenges, which can be solved by appropriate coordination of directional overcurrent relays. The optimal coordination of directional overcurrent relays is an important task to fulfill the protection requirements of the network. This paper presents an optimal coordination method for directional overcurrent relays in the presence of synchronous DGs. The optimization problem is solved by using Harmony Search algorithm to obtain optimal protection settings. Then, the transient stability of synchronous DGs is studied by modeling DGs excitation system according to the clearance time of the network faults. Instantaneous setting of the relays is used in case of the generators instability. The simulation results on an MV network using DIgSILENT Power Factory show that the transient stability of synchronous DGs plays an important role in the coordination of overcurrent relays. The results validate the effectiveness of the proposed method for coordination of overcurrent relays when considering the transient stability of synchronous DGs.

In this paper, pattern recognition algorithms are employed to detect and classify the type of high impedance faults (broken and unbroken) and in case of broken ones to determine the surface (gravel, asphalt and concrete) which the conductor has become in contact with it in power distribution networks. These methods are multilayer SVM and Fuzzy ART classifiers on the bases of features extracted by S-transform and TTtransform from feeder one cycle post-fault current waveforms. These features include energy, standard deviation and median absolute deviation. The proposed algorithms have been tested on different data set, obtained from field tests and simulated data for events with similar characteristics. The results have shown that the features which are extracted by applying TT-transform contain more information and separability characteristics than those extracted by S-transform and also Fuzzy ART classifier has more accuracy in comparison with multilayer SVM.