IEEE 1425-2001 pdf download IEEE Guide for the Evaluation of the Remaining Life of Impregnated Paper-Insulated Transmission Cable Systems
1.1 Scope
This guide provides technical information regarding factors that can affect the life of an impregnated paper.insulated transmission cable system, and it reviews available methods to evaluate the remaining life of suchsystems and preventive maintenance to extend their service life
1.2 Purpose
This guide provides technical background, discussion, and advice to those needing to evaluate the remaininglife of impregnated paper-insulated transmission cable systems. Guidance is given for both high-pressurefluid-filled (HPFF) (see Association of Edison Illuminating Companies CS2-97 (B12) and self-containedliquid-filled (SCLF)(see Association of Edison Illuminating Companies CS4-93 (B137) cables, which use adielectric liquid as the filling and pressurizing medium (dielectric fluid), and for high-pressure gas-filled(HPGF) (see Association of Edison Illuminating Companies CS2-97 (B12]) cables, which use nitrogen gasas the filling and pressurizing medium. The information presented here is intended to provide a completeand concise summary and overview, with frequent references to the technical literature for those who wish toinvestigate specific subjects in more detail. Emphasis is placed on practical, realistic, and economicamethods for performing field and laboratory sampling and testing, and later analysis to determine the actualcondition ofa cable installation
This guide describes the various aging mechanisms that act on cable components. This includes aging of theouter protective coverings and the fluid-containing sheaths and pipes. It also includes thermal-mechanicalaging of SCLF cable sheaths and their mechanical aging due to creep and fatigue, and thermal-mechanicalaging of HPFF insulation due to flexural fatigue resulting from cyclic loads. Thermal and electric stressaging due to cable heating effects and the applied voltage are covered as well.
Methods are presented to assist in evaluating the extent of cable aging Both intrusive and nonintrusivetechniques are described; however, emphasis is placed on the latter. Treatment of the subject includes adescription oftraditional evaluation methods used in the past, supplemented by newer and emerging methodsEmerging methods include dissolved gas and metals analysis of diclectric fluids. as well as tests for otherbyproducts of the decomposiion of cellulose, which can be used to gauge insulation aging and diagnoscincipient failure mechanisms. Finally, advice is provided on preventive maintenance methods, for use inextending the actual service life of a cable system well beyond its economic life.
It is intended that this guide be revised periodically to reflect new developments in diagnostic technologyand experience gained with long service-operating cables.
1.3 Unit conversion factors and acronyms
Metric units are used. Unit conversion factors are given in Annex B
All acronyms used are defined at their first use.
All technical terms are as per IEEE definitions.
2. Cable thermal environment
The cable operating temperature is a direct function ofits loading and of the thermal resistivity of surroundingsoils (see AlEE Committee Report (B4], Mochlinski B711, and Schmill (B91). Although a cable operatedcontinuously or frequently at loads exceeding its design limits will overheat even if the cable thermalenvironment is unchanged, changes to the environment in which a cable is placed may result in the cableoperating at temperatures exceeding design temperatures. Overheating accelerates cable aging (see KurtzB661) or forces cable derating (see AIEE Committee Report B4]).
For the purpose of this discussion, the cable thermal environment includes. in the case of land cables. thebackfill in which it is embedded. the surrounding soil, the surface cover, the water table, and the proxinityto external heat sources. In the case of submarine cables, the marine environment and sediments in which thecables are placed have to be considered. The cable environment can change with time due to either natural orman-made processes.
This clause discusses changes in the cable thermal environment and the methods that could be used tomitigate harmful influences on cable service life.
2.1 Thermal resistivity
IEEE 1425-2001 pdf download
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