## 4 Results  
Experimental Installation for Testing of the Impedance Bond with Condition Monitoring Device and Faults Detection  
After design, realization, testing, and validation of the monitoring device in laboratory conditions, a thermal analysis of the return circuit from electric traction was performed. Moreover, in order to establish the technical condition of the impedance bond, faults that may occur in exploitation were highlighted. The thermal stresses of the return circuit from the electric railway traction are produced by the electrocaloric effect of the current flowing through it. Thus, by monitoring this component of electric traction, it is possible to evaluate the thermal stresses. The analyzed parts of the return circuit are the contacts between the impedance bond and railway tracks from the return circuit of electric traction, where the connection is performed through cables made from different materials and different cross-sections. The goal of the experimental tests was to determine the thermal stress level of the contact terminal area between the impedance bond terminals and connectors of the connection ropes through the condition-monitoring device, and with an infrared device to validate the measurements. The experiments were performed in laboratory conditions. The tests were carried out using the installation shown in Figure 6, which contains the following elements: the main switch K, which supplies with low voltage the power sources composed of an autotransformer (200 kVA) and a power transformer (250 kVA), the non-metallic casing impedance bond (250 A), the connecting conductors between the impedance bond and the railway tracks (steel and copper connection ropes), two railway tracks with a length of one meter, the monitoring device with two current transformers (CT1 and CT2), and NTC temperature sensors (TS) for monitoring the \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Technical Specifications**} \\ \hline Number of current inputs & 2 \\ \hline Current measurement range & 0... 300 A \\ \hline Current accuracy & \(\pm 3\%\) \\ \hline Current measurement resolution & 0.1 A \\ \hline Current transducer on PCB & LEM 6 A type \\ \hline Number of temperature inputs & 5 \\ \hline Temperature measurement range & \(-40\ ^{\circ}\)C... 250 \({}^{\circ}\)C \\ \hline Temperature measurement resolution & 0.1 \({}^{\circ}\)C \\ \hline Temperature sensor & NTC thermistor type \\ \hline Temperature accuracy & \(\pm 2\%\) \\ \hline Programming mode & ISP connector \\ \hline Communication interface & RS 232, USB, GSM \\ \hline Data recording & PC, SD-card \\ \hline Card type & SD/miniSD/microSD \\ \hline SD-card memory & 8 MB... 32 GB \\ \hline Display & LCD 16 \(\times\) 2 characters, lighting \\ \hline Operating temperature & \(-40\ ^{\circ}\)C... +85 \({}^{\circ}\)C \\ \hline Power supply & 90... 264 Vca \\ \hline Exterior dimensions & \(90\times 155\times 60\) mm \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Technical specifications of the impedance bond monitoring and diagnosis device. temperature of the terminals of impedance bond connections (A1-M-A2, Figure 2) and for the ambient temperature (AM). The object, which is under testing, is the impedance bond in the non-metallic casing that is mounted in the electric traction return circuit, starting before 2014, in Romania. They appeared as a result of the advantages over the classic impedance bond in the sense that they can be mounted between the railway tracks, no longer require cooling oil (impregnated with resin), and have small weight and dimensions. The experimental setup was realized in the laboratory and aimed to present the real situation encountered in the field. The experimental tests were performed by connecting the impedance bond terminals to the railway tracks in some situation that could occur in exploitation, based on statistics and historical database.