It is of great importance to choose low-cost, high-performance/efficient and operating and protection equipment in accordance with the applicable legislation in electrical facilities. It is necessary to make calculations for the selection of the most suitable cable/line, measuring and protection system equipment. In this study, panel-inverter compatibility calculation, voltage drop, current control, short circuit, lightning risk and protection calculations, grounding resistance and grounding conductor calculations and tilt angle calculation were made for a grid connected photovoltaic system with a power of 0.4 MWe. It has been calculated that the allowable voltage range and maximum powerpoint voltage values of the selected inverter are compatible with the panel system. With voltage drop and current control calculations, copper cable cross section for each inverter output and solar board output were found to be 3x70+35 mm2 2 and 2(3x185+95) mm2, 2 , respectively, and transformer low voltage busbar 60x10 mm2. 2 . In order not to deform the low voltage busbars in peak short-circuit current, they should be placed at 10 cm intervals for 80 cm length. According to the transformer low voltage side phase-earth short circuit current, the cross-section of the grounding conductor should be at least 53.97 mm2 2 copper conductor. In the lightning protection facility of the panels, according to the rolling sphere method, it has been calculated that the air termination rods should be at least 0.84 m above the upper point of the solar panel. The optimum fixed panel tilt angle was found to be 32.08 degrees. The calculations used in the study will benefit the practitioners in the design of grid-connected photovoltaic systems, in the selection of the most suitable electrical equipment with minimum size.