Document JJ8dmv3pvj7o6aNQYvzQz03Dr

MONSANTO TRADE LITERATURE PERMANENT FIL E PLASTICIZER APPLICATION GROUP ft#******#**#****#*#***##*##*#***#*##************#*****!?* 367Reference Bulletin On: * AROCLOR FLUIDS For The Transformer Industry A#p*r*il 13*,1954*##******#**#***********#****##. #****#*** INTRODUCTION Electrical transformers consist of soft iron cores wound with two or more coils of copper wire. Their purpose is to change electricity from one voltage and amperage to another voltage and amperage. All-parts are insulated from each other, but current surging through one coll induces an electrical current in the other coll. The iron core helps this induction process. It is easier to transmit electricity over long power lines at very high voltages (from several thousand to several hundred thousand volts), so transformers are used to convert electricity generated at a few hundred volts into the very high voltages needed for long distance transmission. At the consume? end of the power lines, other transformers bring the very high voltages down to those commonly used by industry and private consumers. Thus, transformers are very important to our way of living. They ran~;e in bulk from teacup size doorbell trans formers to industrial giants several stories "Sigh. In spite of their simplicity of operation, large transformers present difficult design problems involving heat dissipation, dirt and moisture leakage, and the hazard of internal arcing caused by insulation breakdowns, lightning strokes, malfunction of circuit breakers, eto. Heat dissipation problems are handled by building vents, radiators, or blowers into the transformer case or housing. Insulation problems are handled by a proper choioe of dielectric (nonconducting) material. Dielectrics commonly used are air (for both its cooling and Insulation properties), "Class A" insulation materials (pape^;'--cardboard, cotton, nylon, etc.). "Class B" materials (glass, porcelain, asbeBtOB, mica, etc.), "Class H" materials (silioone deriva tives), mineral oil (where the fire hazard can be controlled) and "Askarel" nonflammable fluids. "Askarel" is a generic name used to describe dielectric fluids used in transformers and capacitors (electrical condensers). These fluids are usually chlorinated hydrocarbons of whioh Monsanto Aroolors are an important series. The Aroolors are mixed with chlorobenzenes. Such mixtures are usually trade marked items and a descriptive .lipfc will be found at the end of this bulletin. The Aroolors, then, are Monsanto's major contribution to the - transformer industry. This bulletin is meant to acquaint you 'jlth both the industry Itself and the Aroolors which find use Askarels". 0627487 TOWOLDMONOQ40038 SALES AND APPLICATION PICTURE j.'OR ASKAREL (Aroclor-Chloririated Benzene Filled) TRANSFORMERS Askarel, fire-reBlatant dielectric and cooling media for trans formers, was introduced commercially in 1932 by General Elec tric Company under their trade name, "pyranol". Subsequently, General Electric licensees have been using the same materials under their own various trade names. These transformer fluids are mixtures of Aroclor and chlorinated benzene, usually they contain a small amount of HC1 scavenger which protects the trans former shell from excessive corrosion in case the transformer arcs (thereby producing some free-HC1-by deterioration of the ohlorinated hydrocarbons). *' In terms of Pyranol alone, since 1932 more than 35,000 Pyranol transformers ranging in size from 1-1/2 to 27,000 KVA (kilovolt amperes) and totaling more than 10,000,000 KVA capacity have established an excellent operating record. These installations include both current transformers and potential transformers. In 1938 the first Pyranol induction type voltage regulators were built and there are now more than 1250 such units in service with a total capacity exceeding 110,000 KVA. . These figures, applicable to Pyranol alone, and reported several years ago, are growing larger each year and are given as a gener al indication of the scope of this business which accounts for a large portion of our Aroclor sales. Mineral oil filled transformers. Including power and distribu tion types, account for about 75# to 80# of transformer construc tion. . However, due to the flammability of mineral oil, these units are used outdoors, mainly. Mineral oil transformers are the least expensive of the fluid types. Nevertheless, in con fined areas' (buildings etc.) where it would be necessary to en close this type of transformer in a safety vault (concrete, etc.), the overall installation cost becomes much greater than the cost of using either Askarel or a dry type transformer unit which provides the safety required without vault enclosure. Consequently, for many industrial (factories) and commercial (office buildings) installations, the ABkarel and dry type trans formers are used rather than the mineral oil type transformers. In this type of installation the voltage ranges used are met most adequately by the Askarel transformers. The KVA class range in whioh ABkarel units are most commonly used is about 50 to 1,000 KVA. However, as mentioned previously, they have ranged up to 27,000 KVA in a few cases. The above information establishes the principal field of applica tion for Askarel transformers and serves to indicate that their direct competition is the dry type transformer, and very seldom, mineral oil transformers. 2 0627488 | TOWOLDMONOQ40039 HOW TRANSFORMER TYPES ARE SELECTED FOR A GIVEN APPLICATION Cost is one of the most important factors in selecting a trans former. A-general idea of cost, but by no means a conclusive one, may be gathered from the following generalizations: 1. Sealed dry type transformers which require sili cone (Class H) Insulation for temperature opera tion at l80C. cost about 25$ more than open, dry type transformers. .2 Ope#, dry type units which, for operation at 55C. over ambient temperature (normal room temperature), may use cotton, nylon, etc.. Insulation, cost' about the same as Askarel units. However, for operation at 80C. over ambient temperatures, glass and porcelain insulation (Class B) is re quired and these units are as much as 10$-15$ higher in than Askarel types. 3. Askarel transformers which use cotton, paper, card board, etc. (Class A insulation) cost about 15$ more than mineral oil transformers. Mineral oil units use oleo-resinous and other common types of varnish and Formvar insulation coatings. Because of this and other construction factors, it is not satisfactory to use Aska rel in a transformer designecTor specified for mineral oil use, ftn the other hand, mineral oil can be used, usually, in units insulated to handle Askarel. Many other factors, in addition to first cost, affect the selec tion of the transformer type for a given application. For ex ample, prompt availability or supply and servicing must be con sidered. The following seotion gives a typical analysis of in door" transformers"considering their various operating charac teristics as a basis for selecting the specific.-type best suited for the Job. ANALYSIS OF INDOOR TRANSFORMER CHARACTERISTICS A modern trend in indoor distribution involves the transmission of power to centers of electrical load at voltages higher than utilization levels, then reducing the voltage through powercenter transformers. This is the long distance power trans mission principle applied to indoor installations. By carrying power through the plant at higher voltages, con siderable savings result from copper reductions. Voltage drop is minimized with corresponding improvement in the performance of motor and lighting installations. The cost of power centers 3 0627489 L,.~. TOWOLDMON0040040 and Beoondary distribution transformers is more than offset by savings resulting from the elimination of long, heavy distribu tion runs inside the plant. Inooming primary currents generally are 3-phase at 13,800 volts or lower (common voltages include 13,200, 7200, 4l60, and 2400). Secondary distribution is usually at 480 volts or 208Y/120 volts 4-wire, with short conductor runs to individual loads. Where the motor load is the governing factor, distribution at 480 volts is usually more economical, with lighting circuits at 240/120 volts 3-wire supplied through step-down transformers. However, where the lighting load is the major consideration, distribu tion is generally at 208Y/12*0 volts 4-wire, with motor loads supplied at 480 volts through step-up transformers. A variety of equipment is available to protect indoor power cen ter transformers, such as high voltage air-break switches in ratings to interrupt full-load current or simply the transformer exciting current. For added protection, fuses may be protected by various combinations of main and feeder breakers in metal-clad compartments, thermal magnetic breakers, safety plug-in units, fused plug-in units, or a variety of switching or interrupting devices between the transformer and the individual load. The impedanoes (opposition to flow of alternating current) of the transformer itself may be used to advantage when circuit protec tion is considered. Impedances in the range of 5.0$ to 5.5$ have . been accepted as a compromise between better voltage regulation and limitation of fault currents. Impedance of this order limits short circuit stresses yet permits the burning clear of many fault ourrents that may occur in the secondary circuit. The transformer may be supplied with various accessories for its own protection. Temperature Indicators show the temperature of the windings under various loads. Thermal relays provide over load protection by automatically operating cooling fans, signal lights and alarms, or tripping the main circuit breaker if an excessive load or short circuit should occur. If it is desirable to prevent operation of the primary disconnect switch while the secondary breaker is closed, interlocking devices may be used. Such precautions are important for the safety of personnel and for protection of the primary disconnect switoh. Maximum service life is obtained by incorporating adequate pro tection of equipment into the electrical power distribution sys tem. Hazards to personnel are reduced to a minimum by enclosing busbars, wiring, switch equipment and transformers. Sheet metal enclosures, bus duct, and conduit prevent contact with live parts, I accidental short circuits, collection of dirt, dust and moisture, wear and damage. Enclosed electrical equipment is safer, re quires less maintenance and gives evidence of careful and order ; ly workmanship. iV 4 1 0627490 i TOWOLDMONOQ40041 COMPARISONS BETWEEN LIPOID PILLED AND DRV TYPE INDOOR ONITS Transformers using mineral oil as a dielectric and cooling medium have a serious disadvantage for indoor use. The oil will support combustion and serious fires and explosions may result from inter nal arcing or ignition from any external source. Earlier prac tice required a sturdy fireproof wall, usually of conorete, a round the transformer when located in or near a building. Con struction of the vault alone is costly and terminal connections away from the transformer were complicated. An added concern is provision for ventilation. Therefore mineral oil transformers are seldom used indoors. With the development of the fire-resistant, liquid dielectric Askarel (Aroolor-TCB mixture), and the dry type transformer, it became a safe practice to Install these transformers indoors without the need of expensive fireproof vaults. Both Askarel filled and dry type transformers have become very popular for indoor use. Each has certain advantages and disadvantages. The liquid Askarel has a dielectric strength oomparable to that of mineral oil and thus may be incorporated without difficulty into designs to withstand the same 60 cycle and impulse dielec tric tests as are standard for oil filled transformers. The following table lists ASA standard dielectric tests for liquid filled and dry type transformers. Type of Transformer KVA Class 60 Cycle 1 Minute Test Rating Full Wave Impulse Test Rating Dry Askarel or Oil Filled 5 8.7 15 5 8.7 15 12 KV 19 KV 31 KV : 19 KV 26 KV 34 KV 25 KV 35 KV 50 KV 60 KV 75 KV 95 KV It will be noted that dry type impulse (heavy surge currents) levels are roughly one-half as high as the level for liquid filled transformers. Sixty cycle tests are also lower though very nearly equal for the 15 KV olass. However, installed indoors where danger from lightning is considerably reduced, the precautions necessary for surge protection are not as im portant as for the outdoor transformer. The dry type transformer must rely upon clearances in air for its insulation strength. If an attempt were made to design the dry type transformer with impulse levels equal to liquid filled transformers, cost, weights, dimensions and losses would be con siderably Increased. The resultant loss of economy is not con sidered Justified. So higher impulse levels are obtained with liquid dielectrics. 5, 062799l TOWOLDMON0040042 Although It is not a great disadvantage, the power faster ef Askarel is somewhat higher than that of mineral oil. Experience has shown that the power factor of the complete Insulation structure of oil filled units is in the range of 1 to 2%. As karel filled IS-ans'r'ormers are found to vary between 3 and 8$*. Askarel has a somewhat erratic behavior at higher voltages but applications up to and including 44,000 volts are in satisfac tory service and the upper limit on voltage may be about 69 KV. Askarel filled transformers require periodic sampling of the liquid to check the dielectric strength which becomes impaired when moiBture is present. Because of the high specific gravity of Askarel, moisture or free water.will accumulate above the liquid level. Porcelain tubes on if.V. leads to terminals are used to proteot against failure over this low resistance mois ture film. As the top is the region of highest temperature in the transformer tank, the Askarel may become saturated with moisture. The saturated Askarel,circulates by thermal action and the moisture is absorbed in the innermost regions of the Insulation structure. Water vapor may form in the top of the tank if cooled sufficiently. This vapor deposited on porcelain or other parts above the liquid level will reduce effective spacings and oreepage distances. Filtering at intervals is necessary to remove any moisture and Impurities, often a special absorbing agent, such as activated clay, is required to remove impurities in solution as well as any moisture present. . While arcing of the Askarel transformer is a possibility and would cause gassing if continued, a properly installed and pro tected Askarel unit has only a very remote chance for this oc curenoe. The following table indicates the approximate volume of Askarel transformer fluid required to fill unite of the given KVA ratings: Ratings 5~WT~ 15 KVA 750 KVA 1000 KVA 1500 KVA 2000 KVA 6/7000 KVA Gallons 6 18 - 20 500 600 1600 Due to the high specific gravity of Askarel - 13 lbs. per gallon - transformers using this liquid are relatively heavy. Their weight is roughly 30 to 40$ higher than a dry type transformer * These figures are relative and subject to change with frequency and temperature. 0627<t92 TOWOLDMON0040043 of equivalent rating. Such added weight may be a considera tion when moving or installing the transformer onto platforms or other levels. Floor space required offers little advantage for either type. Cooling tubes extend from the tank wall of Askarel filled units and add to the overall dimensions. In the same manner, dry type transformers require liberal insulation clearances in air. The dry type transformer enclosure may be conveniently matched to the height of incoming primary and secondary switchgear enclos ures for uniform dimensions and pleasing appearance of the com plete unit substations. CAUSE AND CONTROL OF VIBRATION AND NOISE The main source of transformer noise is the crowding of magnetic waves (magnetostriction) in the iron core. When an alternating magnetizing current is applied, there are rapid minute contrac tions and elongations of the core laminations. Vibrations are set up in the core and coil supporting frames and transmitted to the tank or enclosure and produce noises varying from a charac teristic hum to a loud rattle. Askarel with its high specific gravity adds considerable mass to the transformer assembly. The combination of internal parts and fluid dielectric tends to make the complete Interior a solid structure which dampens or attenuates the vibrations originating in the core. Enclosures for the dry type transformer are made of lighter gauge sheet metal. The panels are in removable sections with ventil ating openings. The enclosures are Intended only to protect the transformer from falling dust, dirt, water, rodents and damage from ordinary movement of men and equipment. They are essen tially light frameworks and of little value in reduolng the noise level and may even amplify it. A comparison of established sound levels for the two types of transformers are listed below: Transformer Sound levels KVA Rating 200 - 300 301 - 500 501 - 700 701 -1000 Liquid Filled 56 Decibels 58 Decibels 60 Decibels 62 Decibels Dry Type 66 Decibels 68 Decibels 70 Decibels 72 Decibels 7 0627493 TOWOLDMON0040044 In a factory where the general ambient sound level Is high, the noise from the transformer may not be noticed. In a school, office building, or hospital, the same noise level may be object ionable. Vibrations may be transmitted through steel structural members, walls, or other parts of the building. It may be necess ary to erect sound absorbing barriers, line the interior of rooms with sound absorbing material or mount the transformer on sounddeadening supports to prevent vibration from being transmitted. The sound level of the transformer varies in relation to the magnetic flux density at which the core is operated. Any sub stantial reduction in noise level would require a transformer of special design. In such a special transformer, it must be expec ted that the core loss would be low but, cost, weight, copper loss and impedance would be high. If price and performance is of no consideration, it is possible to design a transformer with any desired low noise level. In general, the Askarel filled transformer is preferred for loca tions where excessive dirt or moisture is present or When a mini mum noise level is desired without added cost. For suitable applications where reduced weight and a minimum of maintenance is desired, the dry type transformer is preferred. For distri bution to smaller Individual loads, Buch as lighting ciroults, machine tools or special devices, the ease of mounting and sim plicity of connections is an advantage of dry type transformers. DEVELOPMENTS IN DRY TYPE TRANSFORMERS Originally dry type transformers were insulated with class A organio materials such as cotton, paper, fiber, fullerboard, and Insulation board all of which were readily combustible. As the temperature rise of the windings was limited to 55C. over am bient, substantial ventilation waB required, necessitating many ducts in the coil. Expanded metal was generally used to enclose and partially protect the colls. Current densities in the con ductors were low. With the development of Class B insulation permitting a tempera ture rise of 8ocC., it was possible to operate the coil conduc tors at higher current densities. It was also possible to reduoe the area of coil exposed for ventilation, and sheet metal en closures generally replaced expanded metal ones. The class B dry type transformer is smaller and lighter than the older class A types. It is explosion-proof and essentially fire proof. The insulation consists of porcelain, mica, asbestos, fibreglass and similar inorganic materials with an organio binder. After treatment in a special varnish, the coils are baked to give a glossy, tough finish highly resistant to moisture and penetra- 8 0627A94 TOWOLDMON0040045 tion by collections of dirt and dust. Usually the only main tenance required Is cleaning off the accumulations of dust. Suoh maintenance Is fairly simple as the panels are easily removed for acoess to the Internal parts. Excessive moisture or condensa tion on the colls must be guarded against and. If present, a special drying out process Is required. The ventilated dry type transformer Is not adapted to locations where water could enter or submerge the enclosure; or where excessive dirt and lint Is encountered. A more recent transformer development has been the hermetically sealed dry type transformer. The construction consists of a large smooth tank enclosing the core and colls with glass sealed bushings and welded Joints to completely seal the Interior from the atmosphere. Without benefit of ventilation through the core and coll struc ture, all heat losses must be dissipated by radiation and natural oonvection of gas flow from core and coil to tank. The operating temperature for a practical design is Increased beyond the per missible 8oC. rise for class B insulation. Development of class H insulation has made possible the sealed dry type transformer with higher operating temperature. Class H insulation, of which the silicones are most common, permits operation at 180C., a limit which has been tentatively (and probably conservatively) established aB these units will with stand emergency exposure to even higher temperatures. Silicones have ohemloal compositions similar to glass, mica, and quartz. An atmosphere of dry nitrogen gas; is usually sealed into the tank at low pressure. This inert atmosphere excludes oxygen whioh would acoelerate aging and deterioration of insulation especi ally at higher temperatures. By sealing, the effects of humidity, water vapor, dirt, dust, and other contaminants are eliminated. Maintenance for the sealed unit is reduced to a minimum. Only perlodlo oheoks of gas pressure and occasional cleaning are re quired. Hie tank is smooth without openings or radiator tubes, eto., which simplifies cleaning and maintaining a good appearance. Should the transformer be de-energized for long periods, no pre cautions need be taken to prevent condensation on the coils nor is a dryout process required before returning to Bervice. Sound levels are considerably reduced over ventilated dry types of equivalent rating. The confined internal gas space and rigid welded tank reduoes the intensity of noise from the core and coil assembly. Weight and dimensions are comparable to ventilated dry types and considerably lower than equivalent Askarel units. 9 0627495 TOWOLDMON0040046 The sealed dry type transformer is adapted to any use or loca tion where either oil filled, Askarel filled, or ventilated dry type transformers of 15 KV class and below are used in network distribution systems. At the present time about the largest such units in service are 2000 KVA network transformers. They are particularly suited for use in underground vaults where flooding regularly occurs, indoors in dirty locations, or in contaminated atmospheres where corrosive action is a hazard. The sealed units may be located In the open or in busy areas without' danger to personnel. The cost of class H Silicone insulation materials at present is much higher than that of class B insulation. Costs are being steadily reduced through improved manufacturing methods and greater volume, but present costs of sealed dry type transformers are 20 to 25$ higher than equivalent Askarel filled or open dry type transformers. To date, there are no reliable indications that the sealed dry type at its higher cost will compete with the Askarel type transformer in other than special applications. The Aroclor products suitable for Askarel applications are 1242, 1248, 1254, and 1260. How these Aroclor materials are combined is shown.by the following on Askarel nomenclature 1 TRANSFORMER AND CAPACITOR DIELECTRIC NOMENCLATURE ..Aroclor used in transformer and capacitor dielectrics is sub ject to a variety of nomenclature used by various firms. The following breakdown will be useful but should be regarded as confidential as these products and trade names belong to other companies. ASKAREL is a generic name often used to cover halogenated hydro carbons, such as Aroclor, used as dielectrics. general Electric has the following items under their general trade name of Pyranol: Pyranol 85-C - QE's low temperature capacitor Pyranol. Pyranol R362I-S - Special coating for transformer shells in storage to prevent rusting. Pyranol 1432 - (100$g Afoclor 1254 / stabilizer), used for DC capacitors. Pyranol 1436 - (75$ Aroclor 1254 $ 25$ TCB / stabi lizer), used for DC capaoitors. Pyranol 1467 - (60$ Aroclor 1260 / 40$ TCB / seav- enger), used in transformers. Pyranol 1470 - (4556 Aroclor 1260 / 55$ Tri-Tetra- chlorobenzene / scavenger), transformers Pyranol 1476 - Aroclor 1254, capacitors. Pyranol 1478 - Triohlorobenzene, mixed with Aroclor for transformers and capacitors. . 10 0627496 TOWOLDMON0040047 Pyranol l48l - (75# Aroolor 1254 / 25# TCB), used for AC capacitors. Pyranol 1482 - Aroolor 1260, mixed with other Askarel ; for transformers. . . Pyranol 1488 - (60# Aroolor 1260 / 40# TCB), trans formers . Pyranol 1498 - Aroolor 1248, capacitors. Pyranol 1499 - Aroolor 1242, capacitors. Westlnghouse designate their material as Inerteeni Xnerteen 98l8-l - (Aroolor 1242), capacitors. Inerteen 6935-1 - (Aroolor 1254), capacitors. Inerteen 7336-9 - (60# Aroolor 1260 / 40# TCB / scavenger), transformers. Cornell-Dublller call their'-material Dykanol: Dykanol A - (Aroolor 1254), capacitors. Allls-Chalmers use the name Chlorextol; Chlorextol - (Same as Pyranol 1470), transformers. Wagner Electric use the name Noflamol: Noflamol - (Same as Pyranol 1467), transformers. Moloney Electric use the name ABkarel: Askarel - (Same as Pyranol 1470), transformers. Line Material use the name Elemex: Elemex Liquid A - (Aroolor 1254), capacitors. Low temp. Elemex - (Same as Pyranol l48l), capacitors. Part a-67565 I s 'C* I I L. 11 #****&!<! 0f Bulletin***** PQB: MS-400-4A3/54 Printed in U. S. A. 0627<*9? TOWOLDMON004Q048