# Power Quality Impact and Its Assessment: A Review and a Survey of Lithuanian Industrial Companies
## 2 Literature Review  
The impact of electric power systems is multifaceted and must be continuously studied from various angles. One of the most well-known negative factors is undoubtedly the burning of fossil fuels--carbon dioxide CO\({}_{2}\), sulfur dioxide SO\({}_{2}\), and nitrogen oxides NO\({}_{\mathrm{x}}\) along with other gas and particulate matter emissions directly contribute to global warming, poor air quality, acid rains, etc. It is not a secret that although many technologies such as electric vehicles and energy production using renewable energy sources seem to be eco-friendly, they have many side effects. Hydropower can cause drought conditions downstream, affects fish migration, reduces the oxygen level in the water, reservoirs are subject to eutrophication (which is caused by excessive concentration of plant nutrients, primarily phosphates and nitrates) as well as produce carbon dioxide and methane emissions, water release from a reservoir can alter the temperature of the water downstream, etc. Solar and wind parks, not to mention their production process and utilization issues, can not only emit such PQ phenomena as harmonics and flickers, but also reduce the area of grasslands,  
Figure 1: (**a**) Essential requirements for the electromagnetic compatibility of equipment. (**b**) Principal groups of the electromagnetic emissions. which are important to birds of prey for hunt and feed (e.g., this factor is mentioned in [9], which describes the opposition from the local residents to the construction of the wind park in Sirvintos municipality) and, for instance, as a habitat for roe deer (_Capreolus capreolus_) fawns. Further, according to [10; 11], wind park noise can scare animals away and pose a risk of interference in their communication. Habitat loss is also caused due to vegetation clearing around power lines, which is necessary to avoid contact and accordingly PQ events: on the one hand, [10] cites two negative examples of great bustard (_Otis tarda_) and bearded vulture (_Gypaetus barbatus_) and, on the other hand, it cites one positive example of when \"vegetation clearing affected positively some endangered bird species [...] that use [forest] edges as nesting habitats\". Another relevant example is the effects of electromagnetic fields. This topic covers not only the fields created by 50 Hz, 60 Hz, 400 Hz and other frequency power systems, but also the higher frequency fields created by Smart Grid communication networks (see [1] for more information): for example, the highest frequency of 5G NR Frequency Range 2 is 71 GHz. Although neither 50 Hz nor 71 GHz radiation is ionizing and these frequencies are lower than the frequencies of the visible spectrum (400-790 THz approximately), this does not mean that there cannot be any biological or health effects, concerns and their studies. Exposure of living organisms to either power frequency or radiofrequency fields induces currents inside their bodies: this can result in heating of body tissues, and the main variables influencing such interaction are the frequency of the field, the intensity of the field, the length of exposure, the polarization of the field, the modulation of the signal, and the dielectric characteristics of the affected tissues [12]. According to the World Health Organization [13], \"it is not disputed that electromagnetic fields above certain levels can trigger biological effects\", but since the reference levels of electric, magnetic and electromagnetic fields are regulated by various documents (e.g., Council Recommendation 1999/519/EC [14], IEC 61000-6-3:2020 [15], IEC 61000-6-4:2018 [16]), the main question is whether long-term low-level exposure to such radiation can somehow affect one or another group of humans or animals. Such effects can be thermal and non-thermal [17].