Kathleen Davis, Senior Editor
The world’s largest technical professional association honored Carlos Katz with the 2010 IEEE Herman Halperin Electric Transmission and Distribution Award for his “pioneering and vital research on moisture prevention in power cables (that) has extended product life and saved utility companies substantial money worldwide.”
The award, sponsored by the Robert and Ruth Halperin Foundation in memory of Herman and Edna Halperin and the IEEE Power & Energy Society, recognizes Katz for developing and understanding factors that influence life of XLPE- and EPR-insulated cable systems.
POWERGRID International magazine spoke with Katz in May about his award, what inspired him to be an engineer and the pesky, tricky water lurking inside cable.
PGI: How did you think of this cable process? What started the idea bubbling in your mind?
CK: In the late ’60s early ’70s, we became aware of and began investigating the so-called water-treeing phenomenon, which is a degradation of the cable insulation. We learned that this phenomenon is a consequence of water permeating the cable insulation in the presence of electric stress. Water trees concentrate at locations where voltage stress is enhanced, for example, at the location of imperfections such as contaminants, voids and protrusions. The water-tree phenomenon leads to a premature breakdown of the cable insulation.
In subsequent years, several means were developed to minimize the effect of water trees, for example, by developing tree-retardant compounds, modifying the curing-cooling process (using instead of steam a dry pressurizing medium), blocking the conductor inter-strand spacing to the movement of moisture by the use of special compounds, adding water-absorbing layers to the outside of the cables and using jackets incorporating moisture barriers. All of these measures improved the newly manufactured cables. However, the problem of water-tree degradation still existed with the millions and millions of feet of cable already installed in the ground, which in many cases did not even have a jacket. The need to find a means to prolong the life of these cables was of prime concern and made us explore ways in which their useful service life could be prolonged. It was a team effort.
PGI: Once you discovered the water-tree problem, what was the trial and error process for finding a solution? How long did it take?
CK: We worked on the water-tree problem since the early ’70s. At that time I was working in the research laboratories of Phelps Dodge Cable & Wire, later in the laboratories of General Cable Corp. We dedicated significant time and effort to investigate the causes of water-tree degradation. We published extensively on the subject. The initial aim was to minimize the onset of water trees in new cables. Once industrywide solutions were developed, the need to prolong the service life of the already installed old design cables became more acute.
During the early investigations, we had learned that the presence of moisture in the insulation of the cable was the principal contributor to the water-tree development. Without moisture, no water trees developed—so that one of the priorities became to minimize the presence of moisture in the cable insulation. Up to the mid-late ’70s, thermoset cables were manufactured by curing (cross-linking) in steam, which implied that the manufacturer was already injecting moisture into the insulation at the time the cable was being made.
In the field, moisture is always in the environment of the cable, even if it is just moisture in the air. Polymeric jackets slow down the ingress of moisture into the cable insulation but do not eliminate it. Our initial thoughts were to find means to remove moisture from the insulation. This is feasible by having a source of heat at the conductor and in that way causes a thermal gradient, which will minimize moisture in the most critical part of the cable. However, heating the conductor by circulating high current is not practical and is quite expensive.
After several trials, a practical means to achieve removal of the moisture from the cable insulation was found by circulating a dry gas through the inter-strand spacing. Of course, means had to be developed to inject the dry gas and exhaust the moisture-loaded gas. In addition, ways to bypass or replace blocking joints had to be sought. This solution was successful, and many practical experiences were achieved using dry nitrogen and or dry air. However, some of the utilities with whom we were working were not satisfied because of costs related to replacing bottled gas or the maintenance of air-drying equipment, which had to be installed to achieve proper results.
As a consequence, laboratory and field trials were developed using liquids compatible with the cable insulation. One of the first successful trial liquids was acetophenome, which is also generated as a by-product during the curing reaction in cross-linked polyethylene. Although acetophenome is stable in the insulation at relatively low temperatures, unfortunately when it is heated, it diffuses out of the insulation. Shortcomings with this liquid were overcome by the advent of other specially engineered fluids.
PGI: How do you feel about receiving the 2010 IEEE Herman Halperin Electric Transmission and Distribution Award?
CK: I feel highly honored. There were quite a number of people who over the years worked with me on the subject and who contributed significantly to the success of cable rejuvenation, who equally deserve recognition. I personally feel like I have received a Nobel Prize and that all the effort put into this and other developments over the years has paid off.
PGI: What made you want to become an engineer?
CK: During the last year of high school in Ecuador, where I was educated, we had three choices regarding our career development. They were medical, social and engineering sciences. I choose engineering because it was in line with my aptitude and liking.
PGI: What advice would you give other engineers who might have new tech ideas they are toying with?
CK: I would tell them to make sure that their ideas are sound and feasible, to look into all possible aspects and details, to persevere and not to give up easily.
PGI: Looking at all the technology on the horizon, what new concepts have the most promise?
CK: We are strongly focused on cables; therefore, I cannot provide a general response with respect to technology. In relation to cables, because of required reliability, changes are relatively slow. The most promising concepts are in reduced insulation wall thickness (higher dielectric strengths), more reliable accessories (easier to assemble) and higher ampacity systems.
An IEEE Fellow, Katz holds 16 U.S. patents, has published more than 40 technical papers and has contributed to numerous industry reports. He has received the IEEE Power and Energy Society’s Dr. George H. Bahder Memorial Award in 2002 and a Prize Winning Paper Award in 2007. He obtained a bachelor’s degree in electrical engineering from the National Polytechnic School, Quito, Ecuador, and a master’s degree in management science from Stevens Institute of Technology in Hoboken, N.J. He is the president of Cable Technology Laboratories Inc. in New Brunswick, N.J., which provides testing services to manufacturers and utility companies to assure cable system reliability.