## 2 Discussion on Thermal Imaging Diagnostics in Electrical Power Engineering
### Example  
Let us consider the measurement situation shown in Figure 4. The middle phase, as its temperature is much higher than the right-side reference phase, will be tested. According to Equation (1), let us assume the most unfavorable value of k = 2--bad heat transfer conditions and that:  
* There is a 50% load on each phase: \[\Delta\text{T}_{\text{n}}=(69.1-52.0)\bigg{(}\frac{1}{0.5}\bigg{)}^{2}=68.4 \text{ K}\] Considering the values given in Table 2, the result obtained indicates that repairs should be carried out immediately 'IMM'. * There is a 100% load on each phase: \[\Delta\text{T}_{\text{n}}=(69.1-52.0)\bigg{(}\frac{1}{1}\bigg{)}^{2}=17.1 \text{ K}\] Considering the values given in Table 2, the result obtained indicates that repairs should be carried out urgently 'UR'. * There is a 200% load on each phase: \[\Delta\text{T}_{\text{n}}=(69.1-52.0)\bigg{(}\frac{1}{2}\bigg{)}^{2}=4.3 \text{ K}\] Considering the values given in Table 2, the result obtained already indicates the need to observe 'O' for this pair of electrical wires. For low- and high-voltage installations, certain deviations from the values of permissible temperature increases \(\Delta\text{T}_{\text{n}}\) indicated in Tables 1-3 are acceptable as fitted to the technical and financial circumstances. These factors are the possibility of obtaining higher loads (which is associated with an increase in the temperature of the junction), the technical \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Fault Class**} & \multicolumn{2}{c}{**Shielded Connection**} & \multicolumn{2}{c}{**Exposed Connection**} \\ \cline{2-5}  & \(\Delta\text{T}_{\text{n}}\), K & **Recommendations** & \(\Delta\text{T}_{\text{n}}\), K & **Recommendations** \\ \hline
1 & \textgreater{}3 & UR & \textgreater{}20 & UR \\ \hline
2 & 1–3 & NSSI & \textless{}20 & NSSI \\ \hline \hline \end{tabular} Abbreviations: UR—urgently, and NSSI—during the next scheduled service inspection.  
\end{table} 
Table 3: Assessment of the need to repair clamps and conductors of high-voltage power lines based on the calculation of the temperature rise \(\Delta\text{T}_{\text{n}}\) for the rated load \(\text{I}_{\text{n}}\)[20]. and organizational feasibility of shutting down the field (daily service operations, and weather conditions), and the financial consequences of failure or shutdown for maintenance. As stated in the introduction, the main purpose of this article is to encourage discussion to develop relevant international standards for the interpretation of thermograms obtained from thermovision measurements and how operators should react when a specific anomaly is detected. This is because it appears that the guidelines in this respect given, for example, in other standards as an example provided in [24], Table 4, seem to be insufficient and do not cover real-life situations. The most questionable one seems to be deciding on a criterion with low temperature levels as 1-3 K presented in Tables 3 and 4. The measurements of such low differences are difficult and have a high uncertainty due to the limited accuracy of the IR camera, compared to the reference object working in the same ambient conditions and load. The key issue, as mentioned in the standard itself are the qualifications of the person performing the electrical inspection that must be thoroughly trained and experienced concerning the apparatus and systems being evaluated as well as knowledgeable of thermographic methodology [24].