# Voltage Problems on Farms with Agricultural Biogas Plants--A Case Study
###### Abstract
Many adverse effects, including financial losses, result from investors' ignorance, who often violate the basic principles of biotechnology when selecting substrates for their installations [35]. Existing installations are constantly being improved in terms of their production efficiency and environmental impact [6]. The local use of the generated energy avoids the losses associated with the transmission of energy over longer distances [36]. Biogas power plants, being renewable energy sources, are characterised by the stability of the generated power over time (concerning wind or P.V. power plants). Previous authors' studies on agricultural biogas plants connected to the Polish medium-voltage grid confirm this characteristic [8]. However, there is a lack of analysis in the literature of the results of studies that would present an in-depth analysis of the impact of generation in biogas plants on the voltage of the electrical system supplying consumers installed on farms. Power plants connected to the electricity grid can cause an increase in voltage at their point of connection [37]. This increase in network voltage stresses the insulation of electrical equipment, reducing its service life and, in extreme cases, can damage it [38]. Voltage variability depends on the structure of the grid and the power of the connected power plants [39]. In the case of P.V. plants, as the generation level increases, the number of voltage oscillations increases, which can cause instability--short-term voltage stability is strongly influenced by the disconnection of P.V. generation and the resulting voltage drop [36]. The main factors affecting static voltage stability are the power and location of the sources and how they are controlled [40]. Better voltage stability occurs near the transformer station. The variation in the voltage value depends not only on the actual power generated but also on the quality of the current connections, the length and cross-section of the wires connecting the micro installations to the main switchgear and the resistive parameters of the low-voltage network [41]. When the line is not loaded, and the distributed energy sources operate at total capacity, the voltage at each point in the system is higher than the voltage at the transformer terminals. This situation worsens as one moves away from the transformer. The effect of generation on mains voltage values is described in detail for P.V. systems. It is not easy to find publications that describe the impact of a biogas plant (as a stable energy source) on the voltage parameters of the power grid. The impact of microbial biogas plants on the parameters of the supply voltage is all the more relevant because, in Poland, farmers with small agricultural biogas plants have reported problems with the operation of specific consumers, including milking clusters. The authors have filled this research gap by conducting a detailed study of one Polish microbial gas plant. The main objective of the research was to analyse the causes of voltage problems on the farm and to propose and apply a possible solution to this issue. Particular analysis was carried out on the parameters determining the quality of electricity generated in the agricultural micro biogas plant. Presenting the proposed solutions to a broader audience may make it possible in the future to avoid mistakes made in the construction of micro gas plants and even influence the companies building their components to optimise the amount and quality of energy fed into the grid.