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Nowadays, the integration of renewable energy sources, especially grid-connected photovoltaic, into electrical power systems, is increasing dramatically. There are several stimulants especially in the Java-Bali power system, including huge solar potential, a national renewable energy (RE) target, regulation support for prosumers, photovoltaic technology development, and multi-year power system planning. However, significant annual photovoltaic penetration can lead to critical issues, including a drop of netload during the day, ramping capability, and minimal load operation for thermal power plants. This study analyses the duck curve phenomenon in the Java-Bali power system that considers high shares of the baseload power plant and specific scenarios in photovoltaic (PV) penetration and electricity demand growth. This study also analyses future netload, need for fast ramping rate capability, and oversupply issues in the Java-Bali power system. The results showed that the duck curve phenomenon appears with a significant netload drop in the middle of the day because of high power generation from grid-connected PV. Furthermore, the need for fast ramp rate capability is critical for a higher peak load combined with the lowest netload valley. Moreover, the significant load growth with high grid-connected PV penetration level caused unit commitment issues for thermal power plants as baseload operators.

a transmission line system consists of five sub-systems, based on their individual functions. They are insulation, current carrying, construction, lightning protection and accessories subsystems. Each of the subsystem consists of components. Hundreds of transmission towers are usually be found between two substations. . The condition of a transmission line is assessed based on these subsystems. Among others, only some component, namely critical components, contributes to the condition of a transmission line. A favourable transmission line assessment will include every aspect of transmission line, i.e. component condition and environment condition. Environment is crucial factor in transmission lines, a transmission lines may have severe weather condition on some of its towers and in the same time a benign environment on its others. Despite of this importance, in this paper we will discuss about the determination of a transmission line condition. To begin with, an FMECA approach should be conducted and the result will shows each subsystem's weighting factor's which by then we are able to determine the most critical components of it. To achieve this, a good data is very important. The rule used in the assessment is the condition of a transmission line which is determined by the lowest tower condition score.

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Transformers are one of some important equipments on electricity network. Each utility, in this case PLN P3B Jawa-Bali, has to assure their reliability in order to maintain electrical power system stability by assessing transformer conditions. Once transformer condition attained, appropriate maintenance and operation strategy can be defined.Based on failure investigation, transformer conditions are influenced by its insulation condition. PLN P3B Jawa Bali has applied dissolved gas and oil characteristic diagnostics. Since the load grows faster than the network expansion, our transformers tend to be operated at their nominal value or even overloaded. We also find out that through fault current is one of transformers failure root causes. Therefore, we are developing on-line thermal monitoring and vibration in order.The oil and winding temperatures are dependant to load. As the load increases to its nominal value, risk due to transformer paper insulation damage caused by disturbances becomes higher. Subsequently the situation will accelerate the transformer to ageing. By recognizing the raise and fall function of these temperatures to load we can identify the thermal characteristics of the transformer. Other characteristic will be identified is dissolved gas increase caused by feeder faults. Based on these characteristics we are able to conduct some actions, for example: maintaining the temperatures in safe range by controlling cooling system (prohibiting ageing) or determining the condition status of the transformer at that particular time.In this paper we would like to describe our experience in developing the thermal statistic characteristics using load and temperature manual data acquisition, and dissolved gas produced by feeder faults.