Document XzepXNO3DjvjYrwa3DdrZbrXx

I *I,1AUKESNA.YVI B3M iTT .%. A*.1 .. ... ?:..%'*' SUBSTITUTES - NEW DEVELOPMENTS IN rr r^.^A^ilUOERlPiiS^ AND APPLICATIONS /.j ' ' ' V'1-* .- ^OrPimtnMon at fm 49th EngtnmiringConfmwncmof -S, /?? mm>iiri\MI^BicUk:Anodmtk)n ; . .. ' . - . *>., [C*i ..; S-T -v ' * s:y-;' <%. R|e R$E RfE Rj^E R^E R ______ R^E r|e ^pEiSf^KT.' (e^e n^E R^E RfE 3jjpE W^EvJ^E ..HR^IE j3$E rJe i^E R^ ... ^ ^**9^ R^E iJ$E r|e R$EE 3fE R vv^'t -y- ,G` A< ; . <c? ............... ' & f: ' -"' ,4 &$ HONS 013387 KB SCBSTITOTES--SEW DEVELQgtBnS TO MMEKIALS AM) APPLICKTICKS BIOCW3UMD Polychlorinated biphenyls were developed in 1929. Their excellent dielectric properties, including high dielectric strength, low tetter solubility, low fl--Ullty, high heat capacity, and stability were recognised almost inaediately as having the potential to provide low fire risk indoor type transformers with the inherent advantages of liquid cooled efficiency an! reliability. General Electric Company patented the electrical application of theee fluids, and they were subsequently marketed as transformer ilrarslii tndsr such tradenames as Pyranol (General Electric), Inertaen (Meatinghouae), Chloraxtol (Allis Chalmers), etc. The use of these fluids in transformers, and their excellent service record, lad to their acceptance for indoor use without additional fire protection by mjar insurance underwriting fins, and to their inclusion in the National Electrical code, provided that either gas absorption devices or external venting were used. Polychlorinated biphenyls also found wide usage in capacitors because of their relatively high dielectric constant, although fire risk was not con sidered to be a major consideration in their selection as capacitor fluids. In the late 1960s, it became apparent that PCBs had entered and aontaadnatad the environment (primarily fron non-electrical applications). Investigation into the long range effect of this contamination demonstrated that, although the acute toxicity of KBs was low, its resistance to biodegradation and its tendency to bioaocumilate could create situations where levels of concen tration would be harmful to man and his environment. Manufacturers instituted voluntary restrictions on the sale and use of PCBs except in closed electrical equipment. Federal and State agencies took steps to minimise or eliminate the addition of KBs into the environment. The Toxic Substances Control Act (Public Law 94-469) specifically singled out polychlorinated biphenyls and effectively eliminated their future use while establishing a requirement for the promilgaticn of rules relative to the disposal of the material and its operation in totally enclosed systems. The act also provided for the development of programs to examine new chemicals for their toxicological and environmental effects which will hopefully prevent a "PCB problem* from happening again. The Bivixormental Protection Agency estimates that there are presently approximately 140,000 transformers in service containing about 25 million gallons of PCBs and approximately 900 million capacitors in service (includes mall appliance* and flcureseant light ballasts) containing about 50 million gallons of PCBs. 1 HONS 013388 SUBSIT'lVli. PRODUCT DEVBCPtBfT With the ultimate demise of PCB materials apparent, manufacturers of equip ment utilizing FCBs and users of this equipment began pressing far the discovery and development of adequate replacement materials. It was obvious that a replacement fluid gust avoid the type of problem which occurred with the FCBs. Basic .development criteria included the following desix^le characteristics.W 1. It should be nontoxic or very low in toxicity. 2. It should be biodegradable. 3. It should be nonbioaccunilating. 4. It should exhibit low flagmability characteristics. 5. It should have good heat transfer capabilities. 6. It should possess good dielectric properties. 7. It should have a long life and be ccnpatible with the other materials of construction. 8. It should be readily available and reasonable in price. The techniques for studying such factors as toxicity, environnental inpact, heat transfer, dielectric properties and ccnpatibility were well known. Techniques for assessing risks relative to life and property were not established. The acceptance of aakarels had sinply grown into existence by virtue of their excellent service record, and they had never been 'listed* or "approved" by any nationally recognized laboratory. In 1974, RLE Corporation conducted a series of tests designed to sinulate the catastrophic explosion of a transformer. Tests were conducted on conventional transformer oil, transformer askarel, transformer silicone oil. and KUStp fluid. The results of these tests have been reported elsetbere. ' At the same time, work wes proceeding which culminated in revision of the National Electrical Code in May of 1977 and the addition of a new definition and oode'section for "high fire-point liquid insulated transformers'. Factory Mutual Research Corporation did additional developmental work on test pro cedures in the fall of 1976 and between Marc* and October of 1977, accepted for indoor use KlXnp fluid as manufactured by HTE Corporation, as wall as the silicone products of Dow Coining, General Electric, union Carbide, and SMS, and synthetic hydrocarbon materials manufactured by Uniroyal and Gulf Chemical Corporation. Research work is continuing at Factory Mutual in an attenpt to develop rational "approval" standards. LEGAL STATUS Article 450-23 of the National Electrical Code has been revised and reads as follows: 2 HONS 013389 "Transfanners insulated with a nm-propagating liquid approved for the purpose, having a fire point not less than 300%, shall be permitted to be installed indoors or outdoors. Such transformers installed indoors and rated over 35,000 volts shall be installed in a vault. For the purpose of this article, a non-propagating liquid shall be one which, when subjected to a source of ignition, may burn tut the flats will not spread from the source of ignition.1' All of the materials accepted by Factory Mutual meet the requirmmnts of this section of the code. The code section was written in such a way that it would not preclude the development of other economical solutions to the problem. 06HA has issued Progrmn Directive *100-68 which reads essentially the sane aa the 1978 National Electrical Code Article 450-23. The only difference is in OSHA's definition of the word "approved". In order to be approved by 0GHA the material mist be accepted by a nationally recognized testing laboratory. The materials which have been accepted by Factory Mutual therefore meet the 06HA requirements. The Tooele Substances Control Act, and the Office of Tcncic Substances, have phased out all manufacture of PCB containing devices. They are not legally in a position to "approve" any replacement materials, but conversations with the EPA have indicated that, although sllioone oils are not biodegradable, there appears to be no adverse tcodcological or environmental affect from their use in transformers. Since RTBip fluid is less toxic and more biodegra dable than conventional transformer oils, there is virtually no concern about this type of material as a class. To the best of cur knowledge, insurance ccnpanies are writing insurance on installations of transformers insulated with both the silicone and hydrocarbon replacement materials with no increase in premium. Seme insurance ccspanies may choose to require sane type of liquid oontairment as well as currant limiting fuses on the primary side of the transformers, but these are insurance tmdarwriting requiraoents and not legal requirements. APFLICKTICHS Transformer aekarele have historically been used in areas where safety, fire risk, or external environmental conditions precluded the use of conventional mineral oil-filled transformers. They have also been used historically in areas where maintenance wes very difficult because they were felt to provide a lower maintenance situation (little or no sludging) as oonpared to conventional mineral oil-filled transformers. With the development of PCB substitute materials, a nmber of additional applications appear to be practical. A discussion of seme of these follows. 1. Ipdnnr Transformer Applications. Both the silicones and the hydrocarbons appear to be very-satisfactory replacements for transformers either located indoors or inmediately adjacent to buildings where substantial fire risk is involved. Transformers using these materials have been 3 HONS 013390 in service for acne time, and m^erienoe to date indicatea tlmt properly desicped tranafcamera can be used in unit subataticn appli cations and free standing transformer applications without fira protection. Sane manufacturers are reccamending external venting on silicon# transformers because of the potential for the accuailsticn of hydrogen gas.' ' 2. Higher voltage Applications. Transformer askarels have been prisaurily limited to a hlgn voltage of 35 kV because of sane of the characteris tics of other insulating materials impregnated with the askarels. Since KtBrp fluid performs as wall or better than conventional trans farmer oil as a dielectric medivm, we see no reason why it cannot be used at any voltage which is applicable to oil-filled transformers. There are acne indications that the silicones can also be used at higher voltages. Of course, additional work must be done in this area before these fluids become universally applicable to the high voltage arena. 3. High Tanperature Operation. Thera are indications that the replacement fluids add to the thermal stability of the cellulose materials used as insulation in transformers. Testing is going on at this time which may ultimately lead to the use of higher operating temperatures for trans formers impregnated and oooled with the new PCB replacement materials. 4. Switching Applications. One of the deficiencies of askarels wes poor performance as load break switching fluids. RUSip fluid has substantially batter arc suppression characteristics than conventional transformer oil, has superior lubricity and better fundamental dielectric characteristics. Preliminary testing in load break switching devices and in liquid poor circuit breakers indicates that its performance is scmewhat better that conventional mineral oil with the added advantage of a nuch higher degree of fire safety. Switching devices specifically designed to utilize the unique characteristics of KTfhp fluid may provide further econcmies and operating advantages. The silicone oils appear to. be better than the askarels in this regard but their lack of arc suppression capability and lubricity may tend to limit their use in this type of application. 5. Retrofiiilnq Of Aakarel Transformers. Primarily for environmental reasons, a substantial amber of aakarel transformers have been cetrofilled with other materials. Among these are RTBq? fluid, conventional transformer oil and silicone oils. The ismiscibility of silicone fluids with askarels, their lack of lubricity, and their higher cost, are problems which aust be considered in e zetrofill situation.However, as stated above, a substantial amber of transformers have been successfully retrofillsd with silicone and are operating properly today.'5' Conventional transformer mineral oil does not have the imviscibility or lubricity problems of the silicone fluid, but transformers retrofilled with conventional transformer oil must have additional fire protection if they are in an indoor location or irmediately adjacent to building openings. KTOip fluid has the misci bility and lubricity advantages of conventional transformer oil. It is priced substantially above conventional oil, the price being approximately half way between conventional oil and silicone. When used in transformers not specifically designed for their characteristics, both RIBip and sili cone fluids are slightly lass effective as coolants. However, as indicated 4 HONS 013391 In paragraph 3 above, this nay be wore than ccnpensatad for by their high-tsnperature stability.167 6. Betrofllllng of Conventional Oil-Filled Transformers, in past years, conventional oil-filled transformers in specific locations suffered changes in their risk environment due to plant expansion, etc. These transformers were acraetimes retxofilled with eskarel. While this situation still occurs, the traditional eskarel solution is no longer available and the transformers mist either be relocated, contained in fireproof vaults, or retrofillad with a high-fire-point liquid. Being a hydrocarbon material, KIBip fluid is uniquely suited to this applica tion. The only concern is that the residual mineral oil content be low enough to not adversely affect the fire point of the RXBip fluid. Generally, a residual oil level of less than 2% is satisfactory and techniques are available to reach a satisfactory level. 7. Makeup Fluid for Askarel Transformers. Many owners of eskarel trans formers wish to maintain than in their present condition for as long as possible. However, it is occasionally necessary to "top off askarel transformers with sane liquid in order to bring the liquid level qp to the proper point. Since the chlorobenezones have been used in varying percentages ever the years as fillers in the manufacture of transformer askarels, they esn generally be added in reasonably snail quantities without any particular problem. However, they are under suspicion of being carcino gens and the banezanes may not continue to be available. KIBtp fluid is fully miscible with transformer askarel; in any cenhinaticn with askarel the fire point never falls below the fire point of the FXBqp fluid, and the dielectric characteristics will not fall below those of the askarel. Therefore, it makes an excellent topping off fluid which my be easily handled without the potential envircnmntal or toxicological problems of tri or tetrachlarobenezene. semug Tha Governmental actions which have resulted in the elimination of askarel frem the manufacture of new equipment and which have placed severe restric tions on the use of askarels in material already in service may yet panm to be a blessing to the electrical industry. Certainly the continued intrrxJuc- ticn of polychlorinated biphenyls into the envirennent could not be tolerated. As testing continues with the replacement materials, new applications continue to arias which broaden the scope of these materials well beyond that %*iich was permissible car practical with askarel. . 5 HONS 013392 mbmogbathf (1) "PCS Substitutes and Their Properties For Use in Electrical BjuipMnt*, John Olmsted, ttargaret Picrtrowmki, paper presented at American Public Power Association, March, 1977. (2) "Proposed Substitute Fluids For Transformer Aakarels", D. A. Duckett, paper presented at the Southeastern Electrical Exchange, 4-27-76. (3) "Installation and Maintenance of Silicone Fluid Transformers*, page 10, Nestinghouse Electric Corporation. (4) "Problems Associated with the Retxofilling of Askarel Transformers", L. A. Morgan, R. C. Osthoff, paper presented at Power Biginaaring Society, 1977, Winter Meeting. (5) "Silicone Retxofill of Askarel Transformers", T. O'Neil, J. J. Kelly, paper presented at Electrical Insulation Conference, September 28, 1977, Chicago, Illinois. (6) "Cements and Peocamandations on Retrofilling of Transformers", J. Olmsted, RTS Corporation hesearch Publication, 10/31/77. (7) "Cements and Reocmandations on Makeup Fluid for Askarel Transformers", J. Olmsted, RTF Corporation nasearch Publication, 11/15/77. HONS 013393