Spring 2001 -
An Overview of Diagnostic Testing of Medium Voltage Power Cables (Non-PD Methodologies)
- "An Overview of Diagnostic Testing of Medium Voltage Power
Cables," John Densley,
Abstract: Distribution cable systems represent a large capital investment for
electrical utilities. In todays competitive environment, electrical utilities are
being faced with decisions to maintain, repair, refurbish, or replace their cable systems.
This requires an assessment of the condition of the cable system by understanding the
aging mechanisms and also the development of diagnostic tests. According to a 1994 report
of CIGRRE WG 21:04, the purpose of a diagnostic test is to evaluate and locate
degradation phenomena that will cause cable or accessory failure. The
presentation will describe the main aging and failure mechanisms of distribution cables
and the advantages and limitations of diagnostic tests. Diagnostic tests usually measure
or monitor one or more properties of the insulation system that are related to aging
and/or failure. Some tests measure localised properties; for example,
partial discharges at contaminants, voids or protrusions, while
others measure an overall property, for example tan delta (loss,
dissipation or power factor). These topics will be discussed in the
presentation. These slides are available in a 39 kB PDF file.
- "Assessment of Some Diagnostic Techniques for PILC Cables,"
Jean-Pierre Crine, Consultant.
Abstract: Based on a paper by: Vern Buchholz, M. Colwell and J.P. Crine, Powertech
Labs Inc., Vancouver, Canada, S. Cherukupalli, B.C. Hydro, Vancouver Canada, B. S.
Bernstein, EPRI, Washington, USA (now retired). Condition assessment of Paper Insulated
Lead Covered (PILC) cables is a crucial factor for many utilities that have considerable
lengths of these older design cables still in service. This paper is devoted to the
evaluation of various electrical and chemical tests designed to investigate failure
mechanisms such as thermal aging, water ingress and discharges. The non-destructive
electrical tests performed on field-aged PILC cables were: the isothermal relaxation
current (IRC), the LIpATEST leakage current test, the return voltage method (RVM) and the
ac breakdown strength. In addition, partial discharges were measured in the field on an
energized, in-service PILC feeder. Dielectric thermal analysis (DETA), Fourier transform
infra red (FTIR) spectroscopy and moisture content analysis were also performed on small
samples of paper tapes and oil taken in the same samples. It is shown that a combination
of these analytical techniques give a better understanding of the aging condtion of the
tested PILC cables. While studies employing IRC and RV have been reported for XLPE, little
information is available for PILC, and this effort is apparently one of the first in this
direction. The methods do show promise for providing meaningful information, but
additional work is required for a full assessment of PILC cables
condition. Some practical suggestions for future work are also made.
These slides are available in a 35 kB PDF file.
- "Detection of Water Trees in XLPE Distribution Cables Using the
IRC Method," Henning Oetjen, HDW Electronics, Inc.
Abstract: The IRC (Isothermal Relaxation Current) method detects the presence of
water trees and the extent of their damaging effect on XLPE cables. It
allows assessing the condition of the cable before making the
decision to repair, replace or rejuvenate it. The method is based on
the measurement of the relaxation current with regard to 3 distinct
time constants, which can be used to describe the behavior of water
trees with different degrees of progression under the influence of a
polarizing electrical field. The session will provide a technical
description of the method, aspects of its practical use in the field
and field data. These slides are available in a 1.1 MB PDF file.
- "Assessment of the Aging Condition of PILC Cables Using the
Voltage Return Method", Henning Oetjen, HDW Electronics, Inc.
Abstract: The Voltage Return Method assesses the condition of PILC cables by
determining the effect of water, which is adsorbed by the insulation. The water changes
the characteristic return voltage trace, which consists of 2 components. One component
represents the change in the insulation resistance RG and the cable capacitance
CG (parallel elements); the second component is influenced by the time constant
of the polarization effect Rp1Cp1. Both components
change the return voltage curve in a characteristic way. The session
will provide a technical description of the method, aspects of its
practical field use and some field data. These slides are available
in a 606 kB PDF file.
- "Medium Voltage Power Cable Diagnostics by Frequency Domain
Spectroscopy," Peter Werelius, Programma Electric AB.
Abstract: Frequency Domain dielectric Spectroscopy (FDS), or measurement of
capacitance and loss in a frequency range, is a non-destructive method for material
characterization and now available for practical diagnostic measurements under field
conditions. The method shows significant advantages in the interpretation of the results
since more data allow for accurate temperature corrections, separation between different
materials and minimization of the influence of accessories such as cable terminations. Two
main application areas of the method are diagnostics of extruded medium voltage cables
suffering from water tree deterioration and determination of moisture content in PILC
cables. For diagnostics of extruded cables, the high voltage FDS is used and it is found
that depending on aging stage and type, water tree deteriorated insulation exhibits a
characteristic response, which allows for reliable assessment of the insulation condition.
For determination of the average moisture content in PILC cables, the
method is used at low voltage. Higher moisture content gives a
characteristic increase of losses and the loss minimum correlate
well to moisture content. These slides are available in a 230 kB PDF file.
- "Tan Delta (Dissipation Factor) Measurements as an Effective
Tool in Determining the Insulation Condition of Power Cables," Craig Goodwin,
Abstract: The presentation will cover one of the most widely used and proven
on-site diagnostic techniques available to determine the insulation condition of power
cables. This technique provides insight into the overall condition of the cable
insulation. The Tan Delta diagnostic integrated system from BAUR utilizes a high voltage
Very Low Frequency (VLF) generator to apply both variable voltage and/or
variable frequency onto the cable under test. Measurements can be
made in both the frequency and time domain. A brief description of
theory behind this diagnostic technique, the equipment used, a
comparison with other methods and practical examples from field will
be presented. These slides are available in a 1.5 MB PDF file.
Fall 2001 - Basic Power Cable
Design, Part II
- Basic Electrical Characteristics Part II
Carl C. Landinger,
Hendrix Wire & Cable
Abstract: Power cables are utilized by the application of voltage and current on the
cable. The presence of voltage and current is accompanied by electrostatic and magnetic
fields. These both act upon, and are acted upon by, cable, materials, geometry and
adjacent facilities. This course gives a brief overview of the electrical characteristics
of single conductor power cables and a discussion of the impact of adjacent cables and
facilities. The student is made aware of several important characteristics in order to
take them into account when considering specific cable applications. Slides in PowerPoint format 205 kB, slides in PDF format 359 kB
- Fundamentals of Electrical Insulation Materials
Bruce S. Bernstein, Consultant
Abstract: This is the second in a series of presentations on "Fundamentals of
Electrical Insulation Materials". The previous seminar (spring, 2000) reviewed
the basics of polyolefins. This presentation will cover two topics: (1) Compare the basic
properties of paper/oil insulation with that of polyolefins; the natural polymer
(cellulose) and synthetic polymers (based on ethylene) are significantly different in
manufacture, processing and in cable aging behavior, as well as response to diagnostic
tests. (2) Fundamental electrical properties of Polyethylene including response to low and
high voltage stress. Slides in PowerPoint format 683 kB,
slides in PDF format 461 kB
IEEE prohibits discrimination, harassment and bullying. For more
Privacy & Opting Out of Cookies
Terms & Conditions
IEEE ICC PES & Design is a registered trademark of
The Institute of Electrical and Electronics Engineers, Inc.