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The grid-connected Photovoltaic (PV) System was installed in the rooftop of Energi Building, PUSPIPTEK in 2017 located in Serpong, South Tangerang. The System consists of 40 modules @265 Wp, a 10 kWh battery system, and a 10250 kW grid-tie inverter. This study presents the performance analysis of the PV system based on the eight-months monitored data from July 2019 to February 2020. The evaluated parameters of the PV system include yields, performance ratio, capacity factor, energy efficiency, and average daily energy output of the PV system. The results show that the average value of the performance ratio and capacity factor during the eight-months monitored period were 82.42% and 14.07% with average values of the array (Ya), final (Yf ) and reference (Yr ) yields were 3.49 kWh/kWp/d, 3.38 kWh/kWp/d, and 4.12 kWh/kWp/d, respectively. Meanwhile, the average daily energy output of the PV system during the eight-months monitored period was 36.92 kWh per day with the average values of the module (ƞPV), system (ƞsys), and inverter (ƞinv ) efficiency was found to be 15.29%, 14.77%, and 96.63%, respectively. Compared with previous studies in the literature, these results indicated that the grid-connected PV system installed in Energi Building PUSPIPTEK Serpong exhibited good performance.

Power transformer has an important role in a transmission system. One factor that can reduce efficiency in the transmission system is transmission losses. Efficiency can be increased by reducing losses in the power transformer. The biggest influence determining the losses on the transformer is the material characteristic used by the transformer itself. To get maximum efficiency, it is necessary to optimize the materials on the transformer to get the lowest losses. The study is conducted by measuring core losses and copper losses on the 60 MVA 150/20 kV power transformer with the specified specifications. Furthermore, the transformer materials are changed into several types and the losses calculations are done. The calculation results are compared to get the most effective material. The results show that in the calculation of core losses, the core material type with the lowest core loss value is NK E-core of 0,49 Watt/kg. While in the calculation of copper losses, the winding material type with the lowest loss value is Continuously Transposed Conductor.

Power transformer (PT), essential equipment in electrical power system proceeds complicated manufacturing process to meet high standard design. During manufacturing process of PT, the drying stage is of importance to remove excessive moisture contaminant on the solid insulation. This study investigated the effects of drying duration on partial discharge test of 83.3 MVA 275/160 kV PT. The partial discharge test measurements were carried out using IEC 60270 standards comprising of the capacitive network model based on the main quantity apparent charge concept. We found that the lowest partial discharge of 21 pC was achieved at 68 hours drying duration, while the highest value of 60 pC was reached at 81 hours drying time. The longer drying time may lead to initial degradation of cellulose insulation due to excessive heating. The amount of water extracted during drying effect to partial discharge also investigated. We conclude that the drying time at a higher and lower than 68 hours significantly contributes to the increased partial discharge values of PT.

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