More info
Description / Abstract:
This guide provides technical information regarding factors that
can affect the life of an impregnated paperinsulated transmission
cable system, and it reviews available methods to evaluate the
remaining life of such systems and preventive maintenance to extend
their service life.
Purpose
This guide provides technical background, discussion, and advice
to those needing to evaluate the remaining life of impregnated
paper-insulated transmission cable systems. Guidance is given for
both high-pressure fluid-filled (HPFF) (see Association of Edison
Illuminating Companies CS2-97 [B12]1) and self-contained
liquid-filled (SCLF) (see Association of Edison Illuminating
Companies CS4-93 [B13]) cables, which use a dielectric 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 gas
as the filling and pressurizing medium. The information presented
here is intended to provide a complete and concise summary and
overview, with frequent references to the technical literature for
those who wish to investigate specific subjects in more detail.
Emphasis is placed on practical, realistic, and economical methods
for performing field and laboratory sampling and testing, and later
analysis to determine the actual condition of a cable
installation.
This guide describes the various aging mechanisms that act on
cable components. This includes aging of the outer protective
coverings and the fluid-containing sheaths and pipes. It also
includes thermal-mechanical aging of SCLF cable sheaths and their
mechanical aging due to creep and fatigue, and thermal-mechanical
aging of HPFF insulation due to flexural fatigue resulting from
cyclic loads. Thermal and electric stress aging 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 nonintrusive techniques are
described; however, emphasis is placed on the latter. Treatment of
the subject includes a description of traditional evaluation
methods used in the past, supplemented by newer and emerging
methods. Emerging methods include dissolved gas and metals analysis
of dielectric fluids, as well as tests for other byproducts of the
decomposition of cellulose, which can be used to gauge insulation
aging and diagnose incipient failure mechanisms. Finally, advice is
provided on preventive maintenance methods, for use in extending
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 technology and experience
gained with long service-operating cables.
1The numbers in brackets correspond to those in the
bibliography in Annex A.