# Power Quality Impact and Its Assessment: A Review and a Survey of Lithuanian Industrial Companies
## 2 Literature Review
### Environmental Impact
In Lithuania, most lightning strikes occur between the end of spring and the beginning of summer and, as can be seen from the map given in [1], the territory of the country is divided into two zones regarding annual thunderstorm duration--up to and more than 40 h. According to [41], weather is responsible for Minnesota Power high SAIFI and SAIDI values: in 2015-2016, as can be seen from the circular diagrams, the share of weather-related events in SAIFI was 72% and in SAIDI was 27%. In Lithuania, as can be seen from the statistical data of 2015-2018 given in [2], which uses a different data classification and aggregation method, most 10 kV grid faults are caused by flora (including both weather-related and non-weather-related events) with an expected rate (mode of a probability density function) above 1200 per year, followed by cable line failures with an expected rate above 700 per year, lightning and lightning arrester failures, fauna, and insulator failures, while the expected number of conductor gallop events per year is approximately equal to 30; however, the influence of these groups on SAIFI and SAIDI values has not been estimated (only the general assessment of the dependence on the total number of events has been performed by means of regression analysis, which does not reveal the whole picture). Another aspect is the relationship between fauna and short circuits. In [10], twelve abiotic impacts of electric power systems on biodiversity (including plants) are distinguished--the barrier effect, line as a resource, habitat conversion, habitat fragmentation, edge effects, electromagnetic field, the corridor effect, habitat loss, fire risk, the noise effect, air pollution, as well as soil degradation and hydrological alterations. The aspect under consideration falls as a partial case under the scope of the first two topics: (1) the 'barrier effect' is a topic that includes animal contact (collisions) with power grid infrastructure, modification of animal behavior in response to the presence of physical obstacles, as well as other factors (e.g., [10] mentions that power line corridors, especially when combined with roads, affects the distribution and density of ungulates which can be caused by a higher risk of predation, poor foraging conditions, hindered movement and decreased habitat quality, for small arboreal mammals--this results in the loss of canopy connectivity, and for salamanders--this potentially limits the population connectivity); (2) 'line as a resource' is a topic about bird species that use power grid structures for nesting and as a foraging perch: on the one hand, this is beneficial for both individuals and their populations, while on the other, this poses a risk of bird electrocution. A collision must be distinguished from an electrocution--acontact with conductors can either cause a short circuit or not: (1) if an animal touches one wire, the cause of death or injury will be mechanical but not electrical and therefore it will not result in a short circuit (except for the case if a sufficient potential difference is formed between bird's feet, which probably remains a hypothetical scenario), but (2) if an animal touches two points of different electric potential (i.e., either two phases or phase and ground), it will result in both its death/injury and a short circuit. However, at the moment is difficult and therefore studies do not orient towards finding out the proportion between collisions, electrovutions, caused PQ events, their parameters and influence on grid reliability indexes [2] by categorizing the data according to species, grid voltage, transmission tower structure and other relevant criteria.