The criteria for neutral point treatment selection in 20(10) kV radial networks in “Elektra” Zagreb

In the MV network of HEP-ODS “Elektra” Zagreb three ways of substation (transformer) neutral point treatment are used: isolated, low-ohmic grounded and resonant grounded. Methods and results of the study of defining the criteria for appropriate neutral treatment selection are described in this article. Selection criteria consider: • Technical features of all three treatments concerning the earthfault currents, overvoltages and network operation originated from literature, measuring, computer analysis and operation experiences; • People safety requirements and rules (touch voltages), heath and voltage stresses and interferences with telecommunications lines; • Network importance (number and type of connected customers), size (length of galvanic connected lines), type (cable and overhead lines ratio, type of poles, types of cable junctions and screens); • Network reliability (SAIFI and SAIDI); • Earth systems requirements concerning earthfault currents and soil resistivity.