Thermal Imaging Survey of High-Voltage Vacuum Circuit Breakers of Closed Switchgear

Vacuum Circuit Breakers (VCBs) of ladle-furnace units installed in 110 kV closed switchgears operate under heavy operating conditions. This is due to the asymmetric load and frequent switchings natural for steel ladle treatment. These conditions require the monitoring and reliable assessment of the technical condition of VCBs during operation. Such an assessment is conducted by means of frequent thermal imaging control. The report presents the results of the analysis of the thermal modes of the VCBs for two ladle-furnace units. The article provides information on the regulatory diagnostic criteria characterizing the transition from a serviceable state to a pre-emergency one. It is shown that none of these criteria is informative for VCBs. This is due to the fact that, alongside with the load and external factors, the intensity of switching processes affects their thermal mode. A set of criteria is substantiated, including the comparison of the module temperatures included in one phase and a change in the temperature of the module in one polling cycle. Based on these criteria, the authors developed a method for monitoring the thermal state of high-voltage electrical equipment. The results of frequent thermal imaging monitoring of the VCBs considered are provided. The developing defects in individual modules were revealed, thereby confirming the effectiveness of their temperature measurement. The authors point to the necessity of a comprehensive assessment of the condition, including frequent and continuous temperature monitoring of VCB modules. The objective of implementing the developed method in the on-line state monitoring systems is set.