# Power Quality Impact and Its Assessment: A Review and a Survey of Lithuanian Industrial Companies
## 5 Discussion
### Further Analysis of the Survey Results: PQ Impact Similarity Assessment
4) can only be explained based on the comments of the companies, according to which voltage sags are not dangerous for both lighting and heating elements;
4. The similarity of \"Heating elements\" (No. 4) with \"Welding equipment\" (No. 9) perhaps can be explained because a certain analogy can be found out in the principle of operation of these devices;
5. The similarity of \"LV single-phase electric motors\" (No. 5) with both \"Servers\" (No. 6) and \"Welding equipment\" (No. 9) currently cannot be explained and confirmed;
6. The similarity of \"Servers\" (No. 6) with both \"MV three-phase electric motors\" (No. 7) and \"Variable-frequency drives\" (No. 8) currently cannot be explained and confirmed;
7. The similarity of \"MV three-phase electric motors\" (No. 7) with \"Variable-frequency drives\" (No. 8) seems very logical;
8. The similarity of \"LV single-phase electric motors\" (No. 5) with \"MV three-phase electric motors\" (No. 7) seems very logical; \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**No.** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** \\ \hline
**1** & - & 6/6 & 0/6 & 0/6 & 0/6 & 6/6 & 6/6 & 6/6 & 0/6 \\
**2** & 6/6 & - & 0/6 & 0/6 & 3/6 & 6/6 & 6/6 & 0/6 & 0/6 \\
**3** & 0/6 & 0/6 & - & 6/6 & 0/6 & 0/6 & 0/6 & 0/6 & 6/6 \\
**4** & 0/6 & 0/6 & 6/6 & - & 0/6 & 0/6 & 0/6 & 6/6 \\
**5** & 0/6 & 3/6 & 0/6 & 0/6 & - & 6/6 & 5/6 & 1/6 & 6/6 \\
**6** & 6/6 & 6/6 & 0/6 & 0/6 & 6/6 & - & 6/6 & 6/6 & 3/6 \\
**7** & 6/6 & 6/6 & 0/6 & 0/6 & 5/6 & 6/6 & - & 6/6 & 0/6 \\
**8** & 6/6 & 6/6 & 0/6 & 0/6 & 1/6 & 6/6 & 6/6 & - & 0/6 \\
**9** & 0/6 & 0/6 & 6/6 & 6/6 & 6/6 & 3/6 & 0/6 & 0/6 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 40: Overall similarity results. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**No.** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** \\ \hline
**1** & - & 3/3 & 0/3 & 0/3 & 0/3 & 3/3 & 3/3 & 3/3 & 0/3 \\
**2** & 3/3 & - & 0/3 & 0/3 & 0/3 & 3/3 & 3/3 & 3/3 & 0/3 \\
**3** & 0/3 & 0/3 & - & 3/3 & 0/3 & 0/3 & 0/3 & 0/3 & 3/3 \\
**4** & 0/3 & 0/3 & 3/3 & - & 0/3 & 0/3 & 0/3 & 0/3 & 3/3 \\
**5** & 0/3 & 0/3 & 0/3 & 0/3 & - & 3/3 & 2/3 & 0/3 & 3/3 \\
**6** & 3/3 & 3/3 & 0/3 & 0/3 & 3/3 & - & 3/3 & 3/3 & 0/3 \\
**7** & 3/3 & 3/3 & 0/3 & 0/3 & 2/3 & 3/3 & - & 3/3 & 0/3 \\
**8** & 3/3 & 3/3 & 0/3 & 0/3 & 0/3 & 3/3 & 3/3 & - & 0/3 \\
**9** & 0/3 & 0/3 & 3/3 & 3/3 & 3/3 & 0/3 & 0/3 & 0/3 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 39: Similarity results when the significance level is 0.10. The similarity of \"LV three-phase electric motors\" (No. 2) with \"LV single-phase electric motors\" (No. 5) seems very logical;
10. The similarity of \"Servers\" (No. 6) with \"Welding equipment\" (No. 9) currently cannot be explained and confirmed;
11. The similarity of \"LV single-phase electric motors\" (No. 5) with \"Variable-frequency drives\" (No. 8) currently cannot be explained and confirmed. Next, let us proceed to the second part and quantify the similarity. Initial data are given in Table 41: since all elements of the matrices are expressed as a percentage of the maximum, they are the same regardless of the method (No. 1, No. 2a or No. 2b). Contrary to the first method, the second does not consider both the weights and the size of a sample, but it is not a problem. The similarity is quantified by applying Equations (25)-(27). The calculated similarity matrices of three selected qualitatively similar pairs are given in Table 42: after comparing the matrix No. 1 with No. 6, No. 1 with No. 8, and No. 2 with No. 7, it can be concluded that the second pair (No. 1 and No. 8) is the most similar as all values of its similarity matrices are the smallest. This could not be concluded after the qualitative test, and thus greatly expands its capabilities. At the moment, we will not focus in more depth on how to analyze these matrices or extract features from them--this is a further research avenue.