This document analyzes the conditions and impacts of connecting photovoltaic power plants to the electric distribution network, with a focus on electricity quality, including voltage and harmonics. The introduction highlights the importance of integrating solar systems into the grid and the challenges in maintaining voltage quality according to standards. The technical requirements for connecting photovoltaic systems in households and businesses are discussed. Key parameters of electricity quality according to the EN 50160 standard and electromagnetic compatibility standards HRN EN IEC 61000 are reviewed in detail. Quality measurements are conducted using digital multimeters, numerical protection relays, and PQ monitors. The document explores the impact of photovoltaic power plants on voltage stability, flicker occurrence, and harmonics, with examples of the effects of solar systems of4 various capacities. It includes analyses of harmonics, covering odd, even, interharmonics, and supraharmonics. Finally, a detailed analysis and recommendations are provided for maintaining electricity quality in the distribution network when integrating photovoltaic power plants.