# Power Quality Impact and Its Assessment: A Review and a Survey of Lithuanian Industrial Companies
## 2 Literature Review
### Environmental Impact
In Lithuania, according to the Law of the Republic of Lithuania on Special Conditions of Land Use [73], the safety zone of overhead power lines of up to 1 kV is 2 m in both directions, 6 kV and 10 kV--10 m, 35 kV--15 m, 110 kV--20 m, 330 kV and 400 kV--30 m, and formerly used 750 kV (between the Ignalina Nuclear Power Plant and Belarus)--40 m. Further, it is noteworthy that the safety zone of aerial power cables is 2 m in both directions, underground power cables--1 m, and submarine power cables--100 m. The formation of the safety zones results in a corridor effect--these zones, for example, can facilitate the access of both predators and hunter to ungulates, as well as hinder the movement of some ungulate species, such as the white-tailed deer (_Odocoileus virginatus_), when there is snow accumulation [74; 75; 10; 76] (in addition to the already mentioned the roe deer and the European moose (Figure 5c), the following ungulate species also live in Lithuania, many of whose main enemies are grey wolves (_Canis lupus_) and northern lynxes (_L. lynx lynx_): the wild boar (_Sus scrofa_), the European fallow deer (_Cervus dama_), the red deer (_Cervus elaphus_), the European bison (_Bison bonasus_), as well as non-native and less common the northern spotted deer (_Cervus nippon_) (which can mate with native red deer, resulting in the hybrid offspring and thus affecting their own gene pool), the [PERSON]'s deer (_Elaphurus davidianus_), and the European moulfon (_Ovis ammon mason_) [77]). 2. Electrical network equipment and infrastructure failures. These are electrical apparatus failures, pole and crossarm failures, and line failures [71]. The first group includes explosions of transformers, circuit breakers, and other oil-filled equipment. The most common type of insulating oil is mineral oil, which, like many other products of crude petroleum, is flammable, explosive and not environmentally friendly. The second group includes such incidents as wooden pole burning due to short circuit, and insulator contamination. In Lithuania, in contrast to, for example, Latvia, wooden poles are not used. Contamination on the surface of the insulators directly and indirectly enhances the chances of flashover by forming a conductive layer on insulator surface, accelerating the corrosion process, causing cracks, etc., and many effects can be prevented through washing: in addition to natural overgrowth with plants, lichens and algae, insulator contamination may be caused by many other factors and materials, such as salt, bird exceta and feathers, weather and its variations, cement, coal, soil, metallic particles, fertilizers, various chemicals, volcanic ash, sandstorms, smog, and smoke (e.g., see [78; 79; 80; 81] for more information). The third group includes sparking during earthed--three-phase-to-ground, two-phase-to-ground, and single-phase--faults, when the wires fall to the ground. In the Lithuanian MV grids, after a single-phase fault, high grounding (capacitive) currents are limited with arc suppression reactors (by creating the conditions for current resonance). According to [82], it is \"generally assumed that arcs extinguish by themselves when the arc current is below 5-10 A\". It is worth mentioning that under the appropriate conditions, the extinguished arc can reignite.