Submerged Medium Voltage Cable Systems at Nuclear Power Plants. A Review of Research Efforts Relevant to Aging Mechanisms and Condition Monitoring [electronic resource]

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Bibliographic Details
Online Access: Online Access
Corporate Author: Sandia National Laboratories (Researcher)
Format: Government Document Electronic eBook
Language:English
Published: Rockville, Md. : Oak Ridge, Tenn. : U.S. Nuclear Regulatory Commission ; distributed by the Office of Scientific and Technical Information, U.S. Department of Energy, 2015.

MARC

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245 0 0 |a Submerged Medium Voltage Cable Systems at Nuclear Power Plants. A Review of Research Efforts Relevant to Aging Mechanisms and Condition Monitoring  |h [electronic resource] 
260 |a Rockville, Md. :  |b U.S. Nuclear Regulatory Commission ;  |a Oak Ridge, Tenn. :  |b distributed by the Office of Scientific and Technical Information, U.S. Department of Energy,  |c 2015. 
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500 |a "579628" 
500 |a Pena, Gary; Gelbard, Fred; Brown, Jason; Bernstein, Robert; Neely, Jason C.; Glover, Steven F.; Zutavern, Fred J.; Williamson, Kenneth Martin; White, II, Gregory Von. 
520 3 |a In a submerged environment, power cables may experience accelerated insulation degradation due to water - related aging mechanisms . Direct contact with water or moisture intrusion in the cable insulation s ystem has been identified in the literature as a significant aging stressor that can affect performance and lifetime of electric cables . Progressive reduction of the dielectric strength is commonly a result of water treeing which involves the development of permanent hydrophilic structures in the insulation coinciding with the absorption of water into the cable . Water treeing is a phenomenon in which dendritic microvoids are formed in electric cable insulation due to electrochemic al reactions , electromechanical forces , and diffusion of contaminants over time . These reactions are caused by the combined effect s of water presence and high electrical stress es in the material . Water tree growth follow s a tree - like branching pattern , i ncreasing in volume and length over time . Although these cables can be "dried out," water tree degradation , specifically the growth of hydrophilic regions, is believed to be permanent and typically worsens over time. Based on established research , water treeing or water induced damage can occur in a variety of electric cables including XLPE, TR - XLPE and other insulating materials, such as EPR and butyl rubber . Once water trees or water induced damage form, the dielectric strength of an insulation materia l will decrease gradually with time as the water trees grow in length, which could eventually result in failure of the insulating material . Under wet conditions or i n submerged environments , several environmental and operational parameters can influence w ater tree initiation and affect water tree growth . These parameters include voltage cycling, field frequency, temperature, ion concentration and chemistry, type of insula tion material , and the characteristics of its defects. In this effort, a review of academic and industrial literature was performed to identify : 1) findings regarding the degradation mechanisms of submerged cabling and 2) condition monitoring methods that may prove useful in predict ing the remaining lifetime of submerged medium voltage p ower cables . The re search was conducted by a multi - disciplinary team , and s ources includ ed official NRC reports, n ational l aboratory reports , IEEE standards, conference and journal proceedings , magazine articles , PhD dissertations , and discussions with experts . The purpose of this work was to establish the current state - of - the - art in material degradation modeling and cable condition monitoring techniques and to identify research gaps . Subsequently, future areas of focus are recommended to address these research gaps and thus strengthen the efficacy of the NRC's developing cable condition monitoring program . Results of this literature review and details of the test ing recommendations are presented in this report . FOREWORD To ensure the safe, re liable, and cost - effective long - term operation of nuclear power plants, many systems, structures, and components must be continuously evaluated. The Nuclear Regulatory Commission (NRC) has identified that cables in submerged environments are of concern, particularly as plants are seeking license renewal. To date, there is a lack of consensus on aging and degradation mechanisms even though the area of submerged cables has been extensively studied. Consequently, the ability to make lifetime predictions for submerged cable does not yet exist. The NRC has engaged Sandia National Laboratories (SNL) to lead a coordinated effort to help elucidate the aging and degradation of cables in submerged environments by collaborating with cable manufacturers, utilities, universities, and other government agencies. A team of SNL experts was assembled from the laboratories including electrical condition monitoring, mat erial science, polymer degradation, plasma physics,.. 
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