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Lafc.l-1 SUPERSEDES GEA-1886E | * Characteristics of Transformer, Regulator, and Capacitor Pyranol Pyranol is the trade-mark of the General Electric Company for cooling and insulating materials which generically are known as askarels. In addition to the desirable characteristics of mineral oil, askarel has the distinctive property of being non-flammable. The develop ment and application of these materials are fully covered by U. S. Letters Patent. The development of these materials has been actively carried on since 1928 and Pyranol was first used commercially in capacitors in 1931. Today Pyranol capacitors are recognized as the standard means of improving power factor. Prac tically all power-factor-capacitor manu facturers have asked for and received license to manufacture and sell capacitors impregnated with Pyranol. Over 20, 000,000 kvar of 60-cycle power-factor units, using Pyranol, are in service today in addition to over 6,000,000 kvar of high-frequency Pyranol capacitors. More than 60,000,000 small specialty capaci tors are in service for applications such as power factor correction of ballasts, capacitor-motors, radio transmitters, lu minous-tube transformers and radar. The above figures are given as industry figures. Pyranol was first used commercially in transformers in 1932. Since then, more than 35,000 Pyranol transformers, rang ing in size from l}4 to 27,000 kva and totalling more than 10,000,000 kva, have established an excellent operating record. Many of these installations include Pyranol current transformers and Py-. ranol potential transformers. The above figures apply to General Electric alone. The first Pyranol induction voltage regulators were built in 1938, and there are now more than 1250 units in service, totalling more than 110,000 kva. The Laboratories of the National Board of Fire Underwriters have investigated transformer, regulator, and capacitor Pyranols, and their series of reports No. 2581 definitely substantiates all the claims made for Pyranol. The following statements, prepared by our research, engineering, and laboratory organizations, summarize the answers to questions that are asked by users and prospective users of Pyranol equipment. specific need--the elimination of the fire and explosive hazard inherent in the use of mineral insulating oil as a dielectric and cooling medium in capacitors, regu lators, and transformers. Like most scien tific developments, Pyranol is the result of careful study and analysis of the problems involved. Its successful develop ment and commercial application meant the solution of a number of problems which were apparently insolvable. Could a non-flammable liquid be obtained which was not inherently chemically un stable and corrosive? What type of organic hydrocarbon molecule was best adapted to meet the requirements of resistance to sludge and oxidation? How do hydrocarbons decompose under the electric arc? How can the high degree of liquidity so necessary for the proper cooling of transformers be obtained with a non-flammable substance normally solid or plastic-like? These and other problems of equal difficulty and impor tance were attacked, and their successful solution has been the firm foundation on which the commercial application of Pyranol to transformers, regulators, and capacitors has been built. PHYSICAL CHARACTERISTICS Pyranols for different applications have different physical characteristics, ranging from a resin-like, noncrystalline com position to a thin, mobile liquid. The two Pyranols now in greatest commercial use are : (1) The transformer and induction-voltage regulator type (No. 1470), and (2) the capacitor type (No. 1476). Both types have the distinctive Pyranol characteristics of high dielectric strength and non-flammability. The characteristics of these two Pyra nols serve to demonstrate the wide range of physical properties possessed by the liquid materials. f'm. Lr Transformer Pyranol No. 1470 straw-yellow Capacitor Pyranol No. 1476 straw-yellow Viscosity at 37.8 C (Say- Dielectric constant (specific inductive capacity). .... -44 C 4.5 2400 sec + 10 C 4.5 HISTORY OF PYRANOL CHEMICAL STABILITY Pyranol was developed to meet a The Pyranols are all chemically stable *Reg. trade-mark of General Electric Co. and are not affected by reaction with other materials used in Pyranol filled equipment. Experience gained from trans formers in service and from factory tests proves that they are nonoxidizing, and that the Pyranols show no development of corrosive acidity or insoluble sludge over long periods at high temperatures, even up to 150 C. PHYSIOLOGICAL EFFECTS Normal Liquid Condition Liquid Pyranols, like mineral oils, can be handled at room temperature without fear of toxic effects. With some individ uals, continued exposure to liquid Pyra nols may, as with mineral oils, produce skin irritations. Cleanliness among work men handling Pyranol is an adequate safe guard against such effects. Ordinary detergents or medicinal washes will re move any irritation caused by bringing Pyranol in contact with an open cut or skin abrasion. A drop or two of castor oil will neutralize any irritation caused by contact of liquid Pyranol with the eyes. Evaporation from Liquid Pyranol As with most volatile materials, ex posure to concentrated Pyranol vapors in unventilated rooms should be avoided. During the 23 years' experience of the General Electric Company in manufac turing Pyranol, there is no record of any workman requiring first aid or medical assistance because of Pyranol vapors. Products of Decomposition Air-saturated Pyranol at 25 C, when decomposed by an electric arc, evolves finely divided carbon and gases in the following approximate proportions: Hydrogen chloride................. Oxygen........................................ Unsaturated hydrocarbons. Carbon dioxide....................... Carbon monoxide.................... Phosgene..................................... Saturated hydrocarbons. .. Hydrogen............ ....................... Chlorine....................................... Inert (gases).............................. Transformer Pyranol, No. 1470 97.50% . 0.60 .00 .28 .28 .00 .00 .00 .00 1.34 Capacitor Pyranoi, No. 1476 99.00% 0.10 .40 .00 .00 .00 .00 .00 .00 .50 With the exception of the hydrogen chloride, these products of decomposition, which are formed only on failure of the apparatus, are present in such minute GENERAL ELECTRIC oS*5^ STLCOPCB4089177 proportions as to render it unnecessaryeven to consider them. Hydrogen-chloride gas is an irritant and gives full warning of its presence, even in small quantities, by its immediately noticeable odor and irritant action on the nasal membranes. All requirements for protection against gases which may be liberated under arc decomposition where Pyranol filled trans formers are installed in restricted loca tions are met by the "all-purpose" gas masks available for use around dry-type and oil-filled transformer installations. DIELECTRIC STRENGTH The dielectric strength of mineral oil, when new, meets the requirements of capacitor, regulator, and transformer use. Unfortunately, however, mineral oil oxidizes, and among the products formed as a result of this oxidation are some of high conductivity and low di electric strength, such as the organic acids and water. Pyranol is not subject to oxidation. Its dielectric strength is independent of its exposure, even to severe oxidizing conditions during use. The dielectric strength of Pyranol is normally of high order. Commercial values higher than 30 kv are customarily expected. Like mineral oil, however, Pyranol follows the usual gas-solubility laws. Ex posed to wet air, it will absorb some water, and an equilibrium will be set up between the water in the Pyranol and that in the air with which it may come in contact. In contact with water, Pyra nol will dissolve the water until a state of saturation is reached. In this respect, Pyranol greatly resembles new mineral oil; but, unlike mineral oil, its ability to absorb or dissolve water does not change materially with use. Because of the nonoxidizing character istics of Pyranol, filtration of this liquid will normally be less frequently required than with mineral oil. If it should become necessary to dry transformer Pyranol, it can be done in a manner similar to that used in the drying of mineral oil; that is, by the use of a filter press or a specially arranged centrifuge. mci crroir vafckkw i ixi^ rwniui4cTma mut The dielectric constant of transformer, regulator, and capacitor Pyranols is 4.5. at 25 C. This is practically the same as the dielectric constant of the solid insu lations used in transformer, regulator, and capacitor designs, and a more nearly equal distribution of dielectric stress throughout the insulation structure is obtained than with mineral oil. RESISTIVITY AND POWER FAC TOR Laboratory tests and careful observa tion throughout many temperature cycles, and over long periods of time, have shown that the resistivity and power-factor values of Capacitor Pyranols are of the same order of magnitude as those of any good mineral oil adapted for use with these products. Tests on samples of transformer and regulator Pyranol re turned from the field, and other tests in the laboratory, indicate that the power factor will be higher and the resistivity will be lower than those of mineral oil. EFFECT OF PYRANOL ON OTHER MATERIAL Pyranols are stable and chemically inert. Pyranol and its vapors have no effect on the metals and insulations used in Pyranol filled equipment, but are, in general, powerful solvents of most of the gums, binders, paints, etc., customarily used in oil-filled equipment. For this reason, such materials have been elimi nated from Pyranol filled equipment, and only paper, pressboard, porcelain, and other carefully selected materials which have proved to be unaffected by Pyranol are used. It has been found that the aging of these materials under Pyranol will be approximately the same as that under oil. No materials should be used in contact with Pyranol, except those specif ically approved by the General Electric Company. When Pyranol is decomposed by an arc, hydrogenchloride gas is pro duced. The new No. 1470 Pyranol, and No. 1467 which it has superseded, unlike the No. 1488 Pyranol previously used, chemically neutralizes any of this gas which may have been absorbed in the liquid. Consequently, the gas can cause no damage to the organic insulation. This new No. 1470 Pyranol (and the older No. 1467) enables Pyranol filled apparatus, in the rare case of failure, to be opened, inspected, and repaired as readily as oil-insulated apparatus. Pyranol in which arcing has occurred can usually be returned to a satisfactory condition by filtration through a fuller's earth press. MIXTURE WITH GIL Mineral oil is completely miscible with Pyranol, and it is extremely difficult to separate the two materials once they have been mixed. It is important, there fore, to avoid contamination of Pyranol with mineral oil or other petroleum oils, the presence of which definitely influences the vital characteristics of the non flammability of Pyranol. PRESSURE CAUSED BY ARCING If an arc occurs under the surface of any liquid, the liquid evolves gases. The type of liquid determines the character istics of the gases formed. The amount of energy in the arc and the duration of the arc determine the quantity of the gas produced. In general, protective gear or circuit-interrupting devices are in stalled to prevent the evolution of a sufficient amount of gas to rupture the enclosing tank. If the protective gear does not interrupt the arc in time, and no means of release is provided, the gases will be vented by rupture of gasketed joints or, in extreme cases, by rupture of the container itself. Because gases pro duced by an arc in Pyranol are non flammable and nonexplosive, it is feasible to relieve the gas pressure in the tank by means of a frangible diaphragm. For indoor installations of oil-filled equip ment, this method would be undesirable, as the flammable gases released might result in a secondary explosion. All Pyranol transformers and regulators above 25 kva which are to be installed in buildings in accordance with the National Electrical Code are provided with such a frangible diaphragm. The frangible diaphragms for indoor Pyranol distribution transformers or Py ranol regulators are so arranged that: (1) a pipe can be attached thereto, through which the gases that are prod ucts of decomposition can be vented to the outside air; or (2) a gas absorber can be attached thereto containing active materials that will absorb the hydrogen chloride which constitutes the major' portion of the evolved gases. BIBLIOGRAPHY Clark, F. M. "The Dielectric Strength of Noninflammable Synthetic Insulating Oils and Noninflammable Dielectric Organic Compounds," Bulletin GEA- 2691. Clark, F. M. "Water Solution in High ^ Voltage Dielectric Liquids," Bulletin GEA-3509. (AIEE paper.) "Comparative Effects Possible from the Failure of Oil-filled and Pyranol Filled Transformers," Bulletin GEA-3214. "Gas Absorbers and Vent Pipes," Bulle tin GEA-3228. "Pyranol Purifier Instructions," Bulletin GEH-1031. "Pyranol Transformers," Bulletins GEA- 2048 and GEA-2637. "Pyranol Transformer Instruction Book," Bulletin GEH-1093. - For further information, contact your nearest G-E Apparatus Sales Office, Agent, or Distributor t s 10-52 (4.M) 5400 GENERAL mm ELECTRIC SCHENECTADY, N. Y. DS\N 55076A STLCOPCB4089178