Ageing phenomena of current pass blades in high voltage disconnector switch
This failure mode has three primary origins:
Electrical Causes: The switching of currents, such as loop currents, can lead to localized wear. At higher currents, an electric arc may burn at a specific spot, increasing the local resistance. As more switching operations occur, the contact surface wears down further, causing an increase in resistance.
Mechanical Causes: Vibrations, often due to wind, are the main contributors to mechanical aging. These vibrations cause abrasion over time, leading to material wear and potential failure.
Environmental Causes: Corrosion plays a significant role, affecting materials like aluminum, copper, and steel through oxidation. This environmental stress factor can significantly deteriorate components.
An image illustrating a deteriorated flexible joint (specifically, the primary contacts of a center-break disconnector) highlights an instance where improper welding of aluminum belts suggests a manufacturing defect. Environmental stresses have led to the corrosion of the external belt. When combined with mechanical stresses from switching operations, this results in significant material fatigue at the weld site, ultimately causing the aluminum blades to break. This scenario exemplifies how a combination of manufacturing deficiencies and environmental and mechanical stresses can lead to failure.
