Utilization of renewable energy sources (RES) especially photovoltaic (PV) into electrical power system including Indonesia grid massively increasing. Furthermore, high PV penetration level can create duck curve phenomenon in net load profile. This study aim to describe the challenges introduced by grid-connected PV system into Java Bali power system. High PV penetration level changes the load shape in the middle of the day. The calculation results show that system operator must prepare high ramp rate from conventional power plant before reaching the peak load time. Therefore, system operator should make proper planning to deal with duck curve phenomenon.