Correlation Between Insulation Resistance and Temperature Measurement Error in Type K and Type N Mineral Insulated, Metal Sheathed Thermocouples

Mineral insulated, metal sheathed (MI) Type K and Type N thermocouples are widely used in industry for process monitoring and control. One factor that limits their accuracy is the dramatic decrease in the insulation resistance at temperatures above about 600 °C which results in temperature measurement errors due to electrical shunting. In this work the insulation resistance of a cohort of representative MI thermocouples was characterised at temperatures up to 1160 °C, with simultaneous measurements of the error in indicated temperature by in situ comparison with a reference Type R thermocouple. Intriguingly, there appears to be a systematic relationship between the insulation resistance and the error in the indicated temperature. At a given temperature, as the insulation resistance decreases, there is a corresponding increasingly negative error in the temperature measurement. Although the measurements have a relatively large uncertainty (up to about 1 °C in temperature error and up to about 10 % in insulation resistance measurement), the trend is apparent at all temperatures above 600 °C, which suggests that it is real. Furthermore, the correlation disappears at temperatures below about 600 °C, which is consistent with the well-established diminution of insulation resistance breakdown effects below that temperature. This raises the intriguing possibility of using the as-new MI thermocouple calibration as an indicator of insulation resistance breakdown: large deviations of the electromotive force (emf) in the negative direction could indicate a correspondingly low insulation resistance.

Feasibility Study on Electrical Properties of 20 kV Polymeric Insulator Dry Test and Rainwater Test

Insulator is a very important equipment in an electric power system. Ceramic insulators have been widely used to support conductors in 20 kV power lines. The problem of ceramic insulators is that they are heavy, easily contaminated on the surface and require a lot of energy in the manufacturing process. Therefore, polymer insulators were developed. This paper presents the design of an epoxy resin polymer insulator with Titanium Dioxide (TiO2) as a nanofiller. The leakage current test was carried out in a high voltage laboratory by applying an AC high voltage of 50 Hz to the insulator dry conditions and the insulator wetted by rainwater contaminants. The results of the leakage current test in dry conditions are 487.6 μA, rainwater contaminated conditions are 594.93 μA, insulation resistance in dry conditions is 2.07 G-Ohms, and contaminated conditions are 1.41 G-Ohms. Based on the test results show that the insulator leakage current increases up to 22% when the surface of the insulator is contaminated with rainwater. Meanwhile, the insulation resistance decreased by up to 32% in conditions contaminated with rainwater. The value of leakage current and insulation resistance indicates that the epoxy resin insulator with TiO2 as filler is electrically feasible to use.

Optimization of the norms of overhaul runs for traction electric motors of locomotives based on the results of the distribution of failures at the range of the Far Eastern Railway

Objective: Optimization of the rates of overhaul runs on the basis of the results of the study of the distribution of failures of traction motors caused by a critical decrease in the insulation resistance of the windings to reduce the cost of eliminating the consequences of unscheduled repairs of locomotives. Methods: Mathematical statistics, probability theory, theory of reliability of technical systems are applied. Results: A cause-and-effect analysis was carried out of cases when locomotives were placed for unscheduled repairs in 2019–2020. An element has been determined that limits the rates of overhaul mileage of traction electric motors of locomotives. The theoretical distribution of failures of traction electric motors due to a critical decrease in the insulation resistance of its windings is obtained. The optimization of the norms of overhaul runs of locomotives was carried out according to the conditions of current repairs in the amount of TR-2 relative to traction electric motors. It was revealed that the failures are mainly associated with the first period of operation of traction motors. As a result of the analysis of the reasons for the failure of traction electric motors, it was found that most cases of unscheduled repairs fall on the first interval of locomotive runs due to the poor quality of repairs. In this case, the first normal peak of failures falls on the mileage in the modal interval from 156 to 234 thousand kilometers, when the overhaul mileage on TP-2 is 250 thousand kilometers, which necessitates its optimization within the preceding modal interval. Practical importance: The presented version of optimization of overhaul runs can be used to determine the rationality of establishing the norms for the periods of maintenance and repair operations on locomotive units under the conditions of a planned preventive control system for their technical condition

The Electrical Characteristics of Medium Voltage Insulators Against Contaminants at Coastal Area

Insulators have an important role in an electrical distribution line. They has a role as a mechanical support and on electrical insulation that isolate the live line and dead part of the electrical poles. Environmental factors will affect the performance of the insulator. Every area where the isolator was installed has a unique characteristics, therefore the electrical characteristics of each insulator will be differ from an area to others area. This study investigated the electrical characteristics of the 20 kV insulator for some feeder that representing all regions in coastal area. Coastal area has four types of areas, namely industrial, household, city, and rural areas. The leakage current of sample of these four area were measured and the Non-Soluble Deposite Density (NSDD) of each sample were also measured. The results show that the industrial area had the highest leakage current value of 1.22 mA while the lowest leakage current was observed in the household area of 0.44 mA. These were also confirmed that the industrial area had the highest NSDD value of 0.2412 mg/cm2 and the lowest NSDD in household areas of 0.0228 mg/cm2 were observed. Moreover, It was also observed that the highest flashover voltages and insulation resistance were in rural areas of about 53.4 kV and 261.33 GΩ, respectively and the lowest flashovers were in household areas of about 39.34 kV and 118.83 GΩ, respectively.

Insulation Monitoring of Dynamic Wireless Charging Network Based on BP Neural Network

The transmission cable and power conversion device need to be buried underground for dynamic wireless charging of an expressway, so cable insulation deterioration caused by aging and corrosion may occur. This paper presents an on-line insulation monitoring method based on BP neural network for dynamic wireless charging network. The sampling signal expression of the injection signal is derived, and the feasibility of this method is verified by experiments, which effectively overcomes the problem of large calculation error of insulation resistance when the cable capacitance to ground is large. The experimental results indicate that the error of the proposed method is less than 9%, which can meet the needs of insulation monitoring.