Equalizing voltage levels in MV distribution network of Elektra Zagreb

Abstract

In normal working conditions switching power supply of medium voltage (MV) network from one 110/10 kV or 30/10 kV substation to another is conducted almost on daily basis due to different reason, for example maintenance process. This kind of manipulations can cause severe change of voltage levels in low voltage (LV) network powered by 10/0,4 kV substations. This voltage changes can be caused due to voltage drop along the line to which substation is connected to after the switching operation, or due to different voltage levels on MV bus-bars of 110/10 kV or 30/10 kV substations. This problem was noticed after customers connected to LV network started complaining on problems with supply voltage. Considering networks topology and interconnected 110 kV and 30 kV substations through 10 kV network in distribution area of Elektra Zagreb, it was noticed that most customers' complaints could have been avoided by equalizing voltage levels in MV distribution network. With the help of data from Elektra Zagreb's permanent power quality monitoring system and additional voltage measurements, equalization of voltage levels in MV distribution network was conducted.