# Power Quality Impact and Its Assessment: A Review and a Survey of Lithuanian Industrial Companies
## 2 Literature Review
### Economic Impact
and the secondary focus is subsystems and components that aid in the semiconductor manufacturing process (e.g., computers, robots, AC relays, variable speed drives, etc.) [33]. The SEMI F47 curve is more stringent compared to the ITIC curve and other curves given in IEEE Std 1564-2014. Standards play a very important role in the PQ field [1], thus, in spite of the criticism, this is one of the currently best-developed and methodologies suitable for both scientific and practical studies: for example, [34] uses it to assess voltage sags in distribution systems with fast charging stations, and [35]--for analyzing measurement data of the 13.2 kV busbar of the Colombian grid. The methodology of IEEE Std 1564-2014 is appropriate for this paper as well--it will be presented in detail in Section 3.2 and, together with other methods, will be used to assess the results of the survey of Lithuanian industrial companies. Another no less important research area, which also has a lot of gaps, is the immunity to other PQ phenomena. In [36], a focus is made on the impact of DC PQ (ripples, harmonics) on water electrolyzers: it has been found that current ripples generate additional losses in the electrolyzer cell, negatively affect hydrogen production and its energy efficiency, and further works should also concentrate on their impact on the cell degradation. The effects of voltage harmonics on dielectric losses and dissipation factor in HV insulating materials as well as their measurement results fall under the scope of [37]: voltage harmonics due to  
Figure 3: Test results of the LV single-phase equipment immunity to short-duration RMS voltage variations provided by [24; 29; 30]. During the tests, the operation of the devices was not disrupted by the RMS variations above the curve and vice versa. Additionally added fast changing slopes \(dU/dt\) shorten insulation lifespan, may result in additional losses and the acceleration of partial discharge development, as well as their presence complicates dielectric loss measurement and can lead to misinterpretation of the results. Voltage harmonic immunity requirements for adjustable speed electrical power drive systems are specified by IEC 61800-3:2022 [38]: the requirements for levels at the LV equipment terminals are set directly, but for the MV equipment--with a reference to IEC 61000-2-4:2024 [39]. A comparison with the requirements of EN 50160:2010 (which are identical for LV and MV networks) is presented in Figure 4. It can be seen that the immunity requirements for the equipment within the scope is stricter than the values of EN 50160:2010, and that IEC 61800-3:2022 sets limit values up to the 40 th harmonic, while EN 50160:2010--up to the 25 th, but not for all. The requirements for immunity to short-term voltage harmonics (less than 15 s) as well as the requirements for current harmonic values at agreed point of coupling are also given in IEC 61800-3:2022. It must be explained that the compliance with the standard does not mean that harmonics within permissible limits will not have an effect--this is more related to the general assessment of performance to determine whether it is satisfactory or not. Harmonics are classified into even and odd by distinguishing multiples from not multiples of 3, as well as into positive, negative, and zero sequence: positive sequence harmonics (1 st, 4 th, 7 th, 10 th, 13 th, etc.) rotate in the same direction as the fundamental, negative sequence harmonics (2 nd, 5 th, 8 th, 11 th, etc.) rotate in the opposite direction, while zero sequence harmonics (3 rd, 6 th, 9 th, 12 th, 15 th, etc.) do not rotate. Negative sequence harmonics can weaken the mechanical torque of an electric motor, while zero sequence harmonics can cause overheating of the neutral. Information about the impact of voltage unbalance on induction motors can be found in [40] (pp. 596-602). Its nature is threefold: (1) unbalanced power supply from the mains; (2) non-symmetric impedance in either stator or rotor; (3) asymmetrical winding configuration (connection).