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Proceedings: 1983 PCB Seminar,EL-3581,Research Project 2028,Proceedings, June 1984
Atlanta, Georgia, December 6-8, 1983
Edited by
G. Addis, Electrical Systems Division
R.Y. Komai, Coal Combustion Systems Division

Electric Power Research Institute
3412 Hillview Avenue Palo Alto, CA 94304
EPRI Manager, G. Addis
Transmission Substations Program
Electrical Systems Division

Thomas L. Forrester (PG&E) and Thomas H. Milby, M.D. (Medical Consultant)


The utility industry has been unjustifiably branded as the "bad guys" because of PCBs. Once considered a benevolent public servant, the electric utility industry is now regarded by the public as another insensitive, profit-motivated corporate giant which must be continually scrutinized by citizen action groups and heavily regulated to prevent environmental pollution and harm to the public from toxic materials. As a result, electric utilities are confronted with some important decisions about: (1) the type of electrical insulating fluids which are best suited to replace PCBs; and (2) the most effective manner in which to safely and economically replace the millions of pounds of PCBs in existing equipment.

Until recently, the process of choosing an electrical insulating fluid has never been too complicated. The proper selection of a suitable insulating fluid depended upon its ability to satisfy certain operating and engineering performance criteria such as: (1) dielectric strength, (2) viscosity, (3) flammability, and (4) compatibility.1 Having passed these preliminary specifications, the insulating fluid would then be evaluated against more subjective criteria such as: (5) past field performance and experience, (6) availability, (7) the supplier's reputation and dependability and (8) costs.

However, to coin an old adage, "the old must make way for the new" so it goes for the process of selecting an electrical insulating fluid. The task once regarded as "business as usual" has now become more of a nightmare. To illustrate, at 5:30 a.m. on February 5, 1981, a fire broke out in the first level basement mechanical room of an 18-story office building in Binghamton, New York. The fire originated through a fault in the building's secondary (480 v) switch gear, which resulted in a cracked bushing on an adjacent Askeral-filled transformer providing service to the building. Approximately 180 gallons of insulating fluid spilled from the transformer. Ventilation intake ducts located adjacent to the transformer spread the oily smoke and soot throughout the building. Almost three years and more than 10 million dollars later, the building remains closed.2 At 11:19 a.m. on May 15, 1983, in San Francisco, California, a transformer fire in an underground street vault at Steuart and Mission Streets contaminated a small area of a 28-story office tower with PCBs and forced the closure of the entire building. After 10 days of extensive testing and decontamination. Floors 7 through 28 were reopened for occupancy, while floors 1 through 7 remained closed for six months. Out of these episodes have arisen more citizen action groups demanding the immediate replacement of all PCB transformers. The lesson that can be learned from these frightening experiences is that the criteria once thought sufficient to select a high quality performance insulating fluid are no longer adequate. In an ecologically sensitive culture, the public's fear of environmental contamination demands that the electric utility industry broaden the scope of its evaluation process to include the fluid's potential toxicity and effect on the environment.


What then are the alternatives? One concept becomes more and more apparent - that the toxic properties of a prospective insulating fluid are equally, if not more important, in terms of an industry's public image and financial health, than the engineering qualities, and that whatever fluid is chosen must be a s environmentally acceptable as it is a good electrical insulating fluid.

Once the task of identifying all the criteria necessary to properly choose an insulating fluid is completed, the next step is the selection of a suitable insulating fluid. This is the decision area which is critical and requires a thorough understanding of the importance of the toxicity and environmental criteria in making the final fluid selection. There are several non-PCB insulating fluids commercially available which have already been accepted on their engineering qualities.3 The question that remains to be answered is the effect that these electrical insulating fluids will have on the public and the environment.

Mineral oil (Chevron Insulating Oil and Shell DIALA Oil A) probably has the longest track record of any of the non-PCB insulating fluids. It has demonstrated satisfactory electrical insulating qualities and has never to date been associated with any harmful effects other than as a flammable liquid.3,6 However, it may be still too early to determine whether mineral oil may become a problem due to increasing interest about polynuclear aromatic hydrocarbons and their potential toxicity, and bioenvironmental implications.3

From all available information, polydimethylsiloxane or silicone fluid (Dow Corning 561 and General Electric SF 97(50)) appears to be not only an acceptable insulating fluid but represents the lowest potential or adverse effects to the public and the environment.3 The only apparent problem associated with silicone fluid is its potential fire hazard.

Perchloroethylene or tetrachloroethylene (WECOSOL) is being suggested as a very good PCB substitute insulating fluid because of its electrical qualities and more important, its non-flammability.3,6 However, perchloroethylene, like PCBs, is another chlorinated hydrocarbon which may bioaccumulate in the environment and is regarded as a toxic substance and suspected carcinogen.3,5

Finally, the last fluid to be considered as a substitute for PCB is a paraffin-based, high molecular weight hydrocarbon oil (RTEmp). It has good electrical properties, but it is a flammable liquid and, like mineral oil, may have some future problems due to trace amounts of polynuclear aromatic hydrocarbons.3,6


As previously pointed out, the electric utility industry faces two dilemmas: (1) the selection of a suitable PCB substitute fluid; and (2) what to do with the PCBs on hand. Having discussed the relevant issues surrounding the first problem, let us now examine what alternatives are available for the disposition of the PCBs in existing equipment.

Three options are available to the electric industry to resolve the PCB dilemma: (1) a retrofill program whereby the concentration of PCBs is reduced in existing equipment; (2) a total replacement program whereby all PCB equipment is replaced; and (3) some combination of a retrofill and replacement program. However, before a commitment is made to any of these alternatives, the advantages and disadvantages of each must be carefully weighed.


A retrofill program allows or accommodates the implementation of a low-key PCB removal program. The three most obvious advantages of such a program include: (1) a reduced commitment of immediate funds and manpower resources; (2) possibly less attention from the media and the general public; and (3) the costs of retrofilling existing equipment are somewhat less than a replacement program. (Estimates of the cost of retrofill have been quoted by contractors as 6-70 percent of the purchase price of the new equipment.)

Another attractive advantage of a retrofill program is the Environmental Protection Agency's recent program for recertification of PCB and PCB-contaminated equipment. This is the program whereby the EPA will recertify equipment if it is shown through retrofilling that the concentration of PCBs can be reached and maintained below the legal definitions of 50 and 500 parts per millions (ppm) for longer than 90 days.4 EPA's reclassification of electrical equipment is beneficial to industries because it may facilitate employee protection and waste management programs by lessening regulatory requirements.

Finally, the removal of PCB transformers and related equipment may require the complete reconstruction of the vaults in highrise buildings or underground vaults. A successful retrofill program uses existing equipment, resulting in a more timely more economical and more convenient PCB-removal program.

There are also some disadvantages to the retrofill program which are important and must be emphasized. One drawback to this program focused on the safety of the insulating fluids. Although some information is available on the toxic and environmental effects of these fluids, the questions of long-term toxicity, cancer-causing effects and reproductive hazards are still unanswered for some of the fluids.3

Another area of concern with this type of program centers on its alleged capability to reduce and more importantly, maintain the amount of PCBs below certain levels. A successful retrofill program must filter PCBs faster than they leach from the windings and paper products in the core of a transformer and maintain PCB levels below EPA defined criteria or other prescribed levels.

However, tests have shown that when the PCB-filtering and removal system is disconnected, the continued leaching of PCBs from the transformer core will, after some time, again raise the PCB concentration in the quipment.1 Theoretical calculations indicate that the residual PCB concentration must be maintained indefinitely below 1 ppm in order to ensure that in the event of a transformer fire, PCBs and their decomposition products are not found at or above the preliminary safe decontamination levels being proposed by an expert panel of scientists for the Binghamton fire.

Studies are underway by the Electrical Power Research Institute (EPRI) and the New York State Department of Health to determine the minimum levels of PCBs necessary in silicone, perchloroethylene, mineral oil and high temperature hydrocarbon insulating fluids to prevent the type and degree of contamination demonstrated by the Binghamton and San Francisco fires. Until such time as these studies are completed in March or April 1984, it cannot be ascertained what minimum concentration of PCBs bill be acceptable in a retrofilled transformer to prevent the PCB episodes seen by the Binghamton and San Francisco experiences.


If the uncertainties of a retrofill program are too risky and unwielding, let us consider another possible alternative and discuss the advantages and disadvantages of a total PCB equipment replacement program.

Perhaps the most obvious and important attraction of a PCB equipment replacement program is that once and for all, the risks associated with PCBs would be eliminated and the utility industry might begin to breathe a bit easier in the future. Unquestionably for a utility company, the attractiveness of this course would be sufficient to pursue a PCB equipment replacement program.

However, not unlike the retrofill alternative, there is also a dark side to the PCB equipment replacement program. One disadvantage of the program is the lengthy and disruptive construction phase necessitated by enlarging the openings into existing street and building vaults to remove PCB transformers and install new equipment.

The increased costs associated with a replacement program is another drawback. In contrast to a retrofill program where the costs are derived from the purchase of new insulating fluid and any labor involved, the costs associated with a replacement program include not only the new equipment and insulating fluid, but the requisite reconstruction expenses of the program.

Furthermore, since the same insulating fluids are used in both programs, the questions of toxicity and potential environmental effects are still unresolved.


The costs, the conveniences and inconveniences, the unanswered questions about toxicity and environmental effects of the insulating fluids, and the value of retrofilling transformers for recertification purposes are some of the uncertainties which make the decision to retrofill or replace difficult. The potential risks or either alternative are high and there are no guarantees. The decision to retrofill or replace rests with each individual utility and depends on its own particular circumstances and goals. It has not been our purpose to recommend or condemn a PCB retrofill or replacement program, but to provide some insight into the type of considerations which are important and should be evaluated before a final decision is reached.



U.S. Department of Commerce, National Technical Information Service (NTIS). Assessment of the Use of Selected Replacement Fluids for PCBs in electrical Equipment, EPA 560/6-77-008, March 1979.


New York Office of General Service. Binghamton State Office Building Clean-up<, A Progress Report Update, January 1983.


Geon, R.L., Ryan, J.W., Pawlovish, A.M., Joiner, R.L., Rogers, J.L., McEwen, G.N., Rich, P.A. Summary Data on Substitutes for Polychlorinated Biphenyls (PCBs)<, Stanford Research Institute, International, Contract No. 68-01-6016, February 1981.


Environmental Protection Agency, 40 CFR Part 761.30A. Federal Register<, Volume 47, No. 165, Wednesday, August 25, 1982, Page 37358.


Environmental Protection Agency, "List of Toxic Pollutants: Petition to Remove Aromatic Haloethers", Federal Register<, Volume 44, No. 60, Pages 18279-83, March 27, 1979.


U.S. Department of Commerce - National Bureau of Standards; U.S. Department of Energy - Division of Electrical Energy Systems; National Electrical Manufacturers Association (NEMA). NEMA Fluid Filled Transformer Flammability Study, Contract No. NB795BCA0024, July 15, 1980.


The questions basically were in regard to the assumptions and limits used in the study. For example, the requirement that retrofilling should reduce and maintain 1 ppm PCB. This requirement was based on calculations of the limits of furans in soot. It was pointed out, by several discussors, that conversion to ppm furans from ppm PCB was not linear, especially in low concentrations.

Dry type transformers were not considered for replacement because of cost, size and lower efficiency.

Questions were raised regarding trace contamination of silicone fluids with PCB and/or formaldehyde. It was reported that the silicone used was certified to contain less than 1 ppm PCB and that the formaldehyde problem had been solved.

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