59 / 2024-04-07 00:05:07

Contact Resistance as an Indicator of Arcing Contact Degradation in High-Voltage Gas Circuit Breakers

arcing contacts,erosion,high-voltage circuit breakers,resistance

     In electrical power systems, high-voltage circuit breakers (HVCBs) are used to carry normal load current and break short circuit current for operational control and protection purposes. As the components are directly exposed to the switching arcs, the electrical lifetimes of arcing contacts determine the reliability and service lifetime of HVCBs. After current interruptions, it leads to an electrical degradation of the interrupting unit, which is typically referred to as contact erosion. Material transfer occurs between the plug and tulip contacts of the circuit breaker due to a splash erosion. Thus, mass loss, as a conventional characterization parameter, cannot represent the erosion degree of the tulip contact. Therefore, to characterize the degree of arc erosion scientifically, contact resistance is adopted as a basic parameter in this study. The electrical resistance (R) across the closed contact gap was measured using a high-precision ohmmeter with measurement accuracy of 0.1 μΩ. Based on the arc voltage (U) and current (I) in each arc erosion test, the transferred electric charge (C=∫Idt) and arc energy (E=UC) can be calculated. By accumulating the transferred charge (C) or arc energy (E) at different current levels in sequence, the corresponding accumulated amount (∑C or ∑E) can be obtained. It has been found that the transferred charge and arc energy can be used as variables to quantitatively study the degradation process of the contact resistance of the arcing contacts. By comparing the contact resistance after arc erosion tests at different current levels, the degradation process can be divided into three stages, including the initial stage of increased contact resistance, the middle stage of stable contact resistance, and the final stage of rapid increase in contact resistance. The research in this paper can be applied to the condition monitoring and evaluation of the contact system of HVCBs, which provides scientific guidance for improving the reliability of gas circuit breakers.