Combined approach to Medium Voltage Cable and Accessories Aging Management Technique at Nuclear Power Plants

摘要

Studying the influence of long-term operation on medium voltage (MV) cable and associated accessories performance is an ongoing process. In the many years collecting operating experience at nuclear power plants (NPPs), including at those plants licensed for extended operation, it has been found that extruded polymer cabling and accessories can be susceptible to degradation which in some cases cannot be easily or accurately inspected to assess reliability. NPPs have specific nuclear regulatory commitments to establish programmatic ways to appropriately assess and maintain aging management of medium voltage cables and accessories. This paper provides practical NPP experience, methods, and examples of maintaining a comprehensive test methodology that prevents emergent cable replacement and/or unplanned outages. The two vivid examples depicted in this paper discuss this mature MV cable testing program based on a combination of complementary test methods that enable NPPs to: 1. Maximize sensitivity to a broad range of defects. 2. Minimize the risk of false positive' and 'false negative' diagnostic results. 3. Provide high confidence in engineering judgments and decisions. The combination of testing techniques provides a solid technical basis to support robust 'Fitness for Service' decisions. The condition monitoring data can be used to identify time-related deterioration trends before they affect cable performance. The overall approach allows NPPs to make risk-informed and planned decisions on targeted replacement/repair and to address deficiencies to maintain reliable electrical systems.