Document 6bn88bRoReROXL4jaw1gBXBv1

PYRANOL* U tl* Characteristics of Transformer, Regulator, and Capacitor Pyranol Pyranol is the trade-mark of the GenTal Electric Company for cooling and sulating materials which generically are known as askarels In addition to the desirable characteristics of mineral oil, askarel has the distinctive property of being nonflammable. The development of these materials has been actively carried on since 1928 and Pyranol was first used commercially in capacitors in 1931. I t was first used commercially in transformers in 1932 and in induction-voltage regulators in 1938. 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. HISTORY OF PYRANOL Pyranol was developed to meet a specif ic 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, regulators, and transform ers. Like most scientific developments, Pyranol is the result of careful study and analysis of the problems involved. Its successful development and commercial application meant the solu tion of a number of problems which were apparently insolvable. Could a non flammable liquid be obtained which was cot inherently chemically unstable and corrosive? W hat type of organic hydro carbon molecule was best adapted to meet the requirements of resistance to sludge and oxidation? How do hydrocarbons de compose under the electric arc? How can the high degree of liquidity so necessary for the proper cooling of transformers be obtained with a nonflammable substance normally solid or plastic-like? These and other problems of equal difficulty and importance were attacked, and their successful solution has been the firm foundation on which the commercial "nplication of Pyranol to transformers, .ulators, 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 Pyranols now in greatest commercial use are: (1) the transformer and inductionvoltage regulator type (No. 1470), (2) the capacitor type (No. 1476), and (3) the capacitor type (No. 1499). All types have the distinctive Pyranol characteristics of high dielectric strength and non flammability. The characteristics of these three Py ranols serve to demonstrate the wide range of physical properties possessed by the liquid materials. Treat- C ap acitar C ap acitor fonar Tyrand Tyran d Tyran oi N o. No. N o. 1470 1476 1499 Color ................................... urntaf petar V bcoeltr a t 3 7 .S C (So t- b e iti.................................... Row potai (A J.T JA .) . . D ielectric contrant [(p a cific inducthr Sp ecific g ravity a t 2 3 / 15J C .......................... Straw Y llo w Non 42 Sec la m r than -4 4 C 4J us Straw YUow Nan 2400 Set +10 c 4 .23 U05 Straw Y e llo w Non 67 Sc -1 4 C 4J IJS 6 CHEMICAL STABILITY The Pyranols are all chemically stable and are not affected by reaction with tOther materials used in Pyranol filled equipment. Experience gained from trans formers in service and from factory tests proves that they are nonoxidizing, and th at the pyranols show no development of corrosive acidity or insoluble sludge over long periods a t high temperatures, even up to 150 C. PHYSIOLOGICAL EFFECTS Normal Liquid Condition Liquid Pyranols, like mineral oils, can be handled a t 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 iHn 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 30 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 Aff-saturated Pyranol at 2S C, when decomposed by an electric arc, evolves finely divided carbon and gases in the following approximate proportions: Transformer Tyrand, No. 1470 Capacitar Pyranol, No. 1476 Hydrogen Chloride............ O xygen .......................... Unsstvroted hydrocarbons. Carbon dloxidn .............. Carbon won se id .............. iotgen............................. Saturated hydrocarbon.. H y d ro g e n ............................. C h io d a ............................. .. Inert [g a le ri........................ 97.30% 0.60 .00 .28 .28 .00 .00 .00 .00 U4 99.00% 0.10 .40 .00 .00 .00 .00 .00 .00 JO 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 proportions as to render i t unnecessary even 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 t f . trade-mark of General Electric Co. 772537 GENERAL E L E C T R I C GENP 004578 It *:'v- Ii 1- capacitor, regulator, and transformer use. .Unfortunately, however, mineral oil oxit dizes, and among the products formed as a result of this oxidation are some of high conductivity and low dielectric strength, such as the organic adds and water. Pyranol is not subject to oxidation. Its dielectric strength is independent of its exposure, even to severe oxidizing condi tions 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 th at used in the drying of mineral oil; th at is, by the use of a filter press or a specially arranged centrifuge. DIELECTRIC CONSTANT The dielectric constant of No. 1470 Pyranol is 4.5 a t 25 C, of No. 1476 Py ranol is 4.25 a t 25* C and of No. 1499 Pyranol is 4.8 a t 25 C. These values are practically the same as the dielectric constant of the solid insulations used in transformer, regulator, and capacitor de signs, and a more nearly equal distribu tion of dielectric stress throughout the insulation structure is obtained than with mineral oil. RESISTIVITY AND POWER FA C TOR Laboratory tests and careful observa tion throughout many temperature cy cles, -and over long periods of time, have shown that the resistivity and powerfactor 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. The high power factor does not indicate degradation of the Pyranol but rather the solution of trace amounts of transformer materials in the liquid. This effect of in creased power factor Is not harmful unless dielectric strength is affected adversely. EFFECT OF PYRANOL ON OTHER MATERIAL Pyranols are stable and chemically inert. Pyranol and its vapors have nc 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. I t 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, hydrogen-chloride 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 gns which may have been absorbed in the liquid. Consequently, if there has been no contact with free water or high humid ity,'this gas can cause little damage to the organic insulation except in the immedi ate vicinity of the failure. 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 ran usually be returned to a satisfactory condition by filtration through a fuller's earth press. MIXTURE WITH OIL Mineral oil is completely miscible with Pyranol, and it is practically impossible 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 nonflammability 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 installed 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 con tainer itself. Because gases produced by an arc in Pyranol are nonflammable and nonexplosive, it is feasible to relieve the gas pressure in the tank by means of a frangible diaphragm. For indoor installa tions of oil-filled equipment, this method would be undesirable, as the flammable gases released might result in a secondary explosion. All Pyranol transformers 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: (I) a pipe can be attached thereto, through which the gases th at 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. For further information, contact your nearest G-E Apparatus Sales Office, Agent, or Distributor GENERAL ELECTRIC IM S (3M) J 0 S C H E N E C T A D Y , N. Y. 772538 oo U\ -a vo