98

“ . ”, 55, .I , , , 2012 ANNUAL of the University of Mining and Geology “St. Ivan Rilski”, Vol. 55, Part , Mechanization, electrification and automation in mines, 2012

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SISTEM EARTHING IN THE MIDDLE VOLTAGE ELECTRICAL GRIDS Vladimir Perpelitsev, Ivan Stoilov, University of Mining and Geology “St. Ivan Rilski”, 1700 Sofia ABSTRACT: In the report is made survey on the used system earthing in the middle voltage electrical grids around the world and in our country. Underlying is considered sistem earthing with Petersen coil. They are led analytic equations for voltage with zero succession, voltages compared to earth and earth fault current. It’s made analyses for advantages and disadvantages of system earthing with Petersen coil.

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