SUMMARY
Load unbalance is a fault that can damage power transformers in medium voltage networks. The larger load or current unbalance cause heating at the transformer winding and can cause fatal damage if it occurs in a long time. One way to prevent this damage is by monitoring the percentage of load unbalance or current unbalance in medium voltage network. This paper presents the design of load unbalance monitoring equipment on medium voltage networks. Arduino microcontroller is used as the main controller. Current sensors and voltage sensors are used to obtain the data of current and voltage at any time. The load unbalance monitoring result that exceeds the setting value is sent to a warning systems and mobile phones. The test results on the secondary side of the power transformer showed that the equipment can monitor load (current) unbalance with a maximum difference of 0.17%, voltage unbalance with maximum difference of 0.033% and neutral current with maximum difference of 3.29A compared to the actual values. The monitoring equipment is also capable of sending data to sound warning system and to the mobile phone when the percentage of load (current) unbalance exceeds the setting value, i.e. 30%.Keywords : load unbalance,monitoring, medium voltage network, power transformerKata Kunci : ketidakseimbangan beban, monitoring, jaringan tegangan menengah, transformator daya