Document nkK23eLBDaojo85dBJ6p5D8bm

-/ ' O'T- Cwftrna tetiniaMi da gram* Usm Qednqms i ttitfe Tim III, Boulwvrd Hauumann, Paria Sauion 1999 -- 4 Juia *.14 Jala .119 - THE USE OP NONFLAMMABLE LIQUID IMPREGNANTS IN ELECTRICAL CAPACITORS AND TRANSFORMERS by r. X. CLAM, CasaalttBf Ea^aaaa-DWaatrtaa, Oaoml Oaatria Campamj, ScbaoaaUdy, Haw Yaak (V. A A.). naif a. cocmey, B. fa (Ba+), ALLt, P. IaaU P. Dr. to*, i AkHaifaaillirhaft. Pyiwwt, Bmlta (Oarmojr). x. w: roraorr, Prat Dr.-lo** AUfanatM EkkWatUtt-Oaaatlactaft, Stvtt|ul (Oamm*). ad r. YZALS, Pnfaaaa. AtoOoa. St. o*a* (Piaaaa). and poooaoa aooaftoW iUhttrU ataNUJy /br mm <ji aapaattan and Iran* /ortntro. Tkt fMa mkil ahn (baaa Kfitfda or* taaompoaad Pf bool or tita iMrb on or* non/tamnaNt and efnad--ffy mmoptoarfu. IMP aoo at fmpwfnarUa for aolid (nmidfiw imona Mkr aimtrfoaf knti dUtrttmttm aaroao a Marofwaoai tatnlaMM titan < poat/Ua UA mlnarta oil Tim MfM d/alatap<a oonotanl af tikaaa tinpr*. fMiUi oiaa rmotti (a imatiar pligotad i(n (ban dooo Ukuno/ mtttaral HONS 034540 119 oil when used in capacitor* of simitar construction. The soloent action of these liquids on other materials of construction may lead to increased dielectric toss which can be eliminated by the use of actleated alumina as Illustrated. Because of their nonflammable and nonexplolist characteristics, equipment containing these liquids may be installed without the severe restrictions whleh normally apply to the installation of simitar oil filled equipment. This frequently resultt in an economy In Uw installation and operation of transformers in which these synthetic liquids art used. Further economies are oMointd through the elimi nation of many of the maintenance problems generally associated with the um of mineral ott. REPORT Mineral Insulating oil 1ms boon tbo moot widely imd Imprs* footing liquid for electrical insulation, doopito tbs tact that Its uss Involves difficult problsms of refining and protection against dieiectrle and ehonUeal dsgradation. Most of those problsms trfst from tho fact that mineral ott is a complex composition whose etaomleal makc-op varies widely from one crude source to another. This variation in chemical competition Is reflected in the varying utility of any one refined produet for different electrical applications. But ovsrshadowlng these difficulties of composition and selection are the dUScnltles arising from tho son with which mineral Insulating oil Is oxidized. Resort has been made to mechanics! and te chemical means by which the oxidation of the oil may bo substantially reduced. The nonflammable materials, however, possess none of these basic objections found In oil. They are synthetic products, easily subject to quality control regulation and acceptance and made from materials which arc widely available. Unlike mineral oO, the nonflammable Insulaats are not fcubjeet to oxidation, and maintenance problems of this typo are eliminated. Their marked chemical stability insures freedom from both chemical and dielectric degradation when properly prepared and used in suitably designed sitetrical equipment. Because of thsir characteristic properties, these Uquid Insulating materials have found their greatest engineering applications in electric capacitors and transformers. HONS 0345^1 --3- lit CHEMICAL BASIS or THE NOMTLAMMABLE LIQUIDS. la tbi UbIM Statw, tba aorUUmmabU insulating liquids an taDS M AiluNi ". la Bumps u wall u la tba United Stataa, tbaaa Askars) compositions an also known by various tmds um inch aa Pyranal, foartasn. Amehlor, Pykanol, Pyndant, Clapbtn and NspoUn. , Aaknrol 1s a daw mbs which to appttad to tba United Statw to daalfaato a syuthatSe oonflawunahla insulating liquid which whan decomposed by tba aleetris an avdvaa only aoBdaanibla gnaoni minors* [1|. Tha rkwifral boats far tbto dwbabla behavior to faasd to tbs high raaettvtty of hydrogemand ebloftea (3). TFbao proparly chlorinated so tbat aaeh maiaenla eoBtatas a nhndnaltr equivalent amount <rf hydrogen and chlorine, dsesmpsitllon of a tnw Askarat by boat or tbs elsctrie are loma only hydwgen ablorbla and carbon. Ta mast tbs daatosd chamtonl and iHsiswtris stability required to daetrieal applications, commercial Askaralr of praaant usage tan tha ehlovtoatad darivutlv* of aromaUe hydrocarbarn. Moot widely nsad art chlorinated baaaana and tha cblartnatad dlpbeoyls, of which tba mcMoriianasaa and pswtaahlar dlpbanyl art ccttosplaa. Each of tbaaa materials to nsad as a mtatwo of (ta Itamsrr from which Its liquidity to derived. par transfonnar tut, tbaaa cblerlnatad products ara blended la praportlana ta give tba raqnlrad vtoaadty or solidification characteristics (3J. COMKEHCZAL NONFLAMMABLE # 2NHULATXNO LIQUIDS. . A cantor of nonflamsmbla insulating liquids ara in coouanrdal use. Tbaaa ara ail ccmpaatttana eompriatag chlorinated dlpbaayl or Mtetnm of chlorinated diphenyl and ablorinatad baniaaa. Typical proptrtSaa and asw of tba nonfiammaMc liquids art given to table L Tba propartiac listad ara avtrapt vahwa and an not naeoaaarily representative of any oaa coamtrdal conroa of than CAPACXTOH APPLICATIONS. From tba dlafoetrit itandpotot. tba greatest advantage poasasiid by tba aonflammaMo insulating ttqnlds as capacitor lapregnants ta ptaee at mtocni afl liw la tba bigbar dlaUetria constant which to posSMt to ba obtained. Figura i Uluitratas tha effect of chleri- no. HONS 034542 119 -- -4 -- Tamj I. Typical propirtitt <tnd hmi / M nonflammable intulatiftf liquult. L`ie............................................. Coaditioa (a5*C)...................... Color........... ............................... Acid value (af KOH/f)........... Freo chlorkto ion...................... Sp. frevltj' (j5C)................... Fire poiat (*C)......................... Pour point (*C).................. .. i (J?.a-c>................ Vlaeoaitv < (98.9*0)................ ((ioo*C).................... Goof, of expceiioa (35-09*0 (eV*V*C).......................... lleet eoaduetivitj' (4o*C) (kcal/a/h/*C)........................ Refractive jades (30*0X0)... Dielectric itrenftli (ao-po^C): (hV/ea)(V. B.D.)............... V. P. M. (A. $. T. M.)............ Dielectric coMteet.................... j Spec!Do remittance(po*C) (0-cm). Power feetor(9o*C)................. Capacitor* Capacitor* Clear Clear Yellow tint Light veilotv < 0.01 < o.ot .Ml Nil 1.40-1.45 I.54-1.5J None None 0 to --: 6 to 11 300 (S. 3. U.) 3000 (S- 3. (J.) 4o (3. 3. V.) 48 (3. S.U.) 1.4* <*> 80 x io~* 65 x to-* 0.091 1.033 0.08? 1.839 300 35o 5.3 (30*C) 4-4(o*C) 1-5 x to'* o.oi5 300 3So 5.o (io*C) 4.(90*C) 1-5 x to" o.0(3 Triniloreirt Clear VIUh tiM < o.ot Nil None -- Jo to -- >> U /S.S. c.. _ 67 X I-1 o.o9; 1.807 ran IS 4.5 (35*0 3.p (100*0 i-S x to" o.oiw.si Trenaf.H we! Clear Yellow Uni " .. Nil 1. ii-T. None --ii io --. X .3.5.0 U ' 3. 5.1. _ or x i.-> .ost.ti 100 J5 i.l Ji'**.j .ti !?''. 1 t-Vx jo*' i.oi-o.oi MOWS 034543 M lttT M C CONSTANT a ut nation on tha dMootrto eomtut ol the hydrocarbon dlpbanyL It wiO ba obaarrad that a dielectric eooatast aboot i i obtainable At Wtbler NpiMaylt fc MiMhbr NpWayU C, poMadtfw Nyha^ti Mpnpani apiiw yipT. A, triehlar itfimyt hanpt4> *, tiimMw NpMayl hapropatif; Ct tmtttMm Nphaayt iNpiapitedt D, tnwai oil liwptii. irtm Um proper degree of chlorination. Tha naa of ttqnids of sneh high dlNaetitf eowtant u coaparod to rainaral oQ (dMoetste ooMUnt a.*) b redacted to a deereaee in tha ikn of Um Impregnated *0**s 119 paper capacitor which may be only about 5o-6o % of the ilae of the oil treated capacitor of similar construction and capacitance. - The dielectric constant of the chlorinated diphenyl, however, decreases ripldly at the point of Its solidification. The effect of temperature change on the dielectric constant of typical chlorinated diphenyls of commercial use is illustrated In figure . The effect of temperature on the capacitance of capacitors impregnated with typical commercial nonflammable liquid dielectrics is Illustrated in figure 3. The dielectric loss characteristics of the capacitor having a Kraft {i t ic i i :4 t-te r Jf z - / 4- rinwcrtaTURi Fig. 4. -- The effect of temperature on the dielectric loos ol Kraft | spaced capacitors Impregnated with chlorinated dlpbanyl. A, trlchler diphenyl; B, tetrachlor diphenyl; C, pentaehler diphenyl; D, unlmpiegnnted capacitor. paper dielectric impregnated with each of the commercial non* capacitor liquids arc Illustrated la figure 4, showing the fleet of temperature o tf < characteristic of the finished capacitor, In comparison to similar data on the dried but unlmpregneted paper. The Ugh dielectric constant of the nonflammable capacitor Impreg nate insures a further advantage. Because of Us closer approach to the dielectric constant of capacitor paper fibre a more evenly distrib uteddielectric stress results than Is obtained with the use of mloeral oil. If the dielectric constant of the capacitor paper fibre is accepted Hons *4545 --7-- lit u 7, the rlectric itreac applied to th* liquid Sla In the oQ lmpr|* noted capacitor will bo about 1.5 timai that abtorbod by tba liquid Um in tba chlorinated diphenyl capacitor of iimiiar deeifa. thU huvaa a creator dlalaetrte mobility for tho chlorlaaUd diphenyl treated capacitor. With mineral oil treated paper bualatlon It haa bean observed that on inereactne tba voltafe, from a low Taint. Internal discharge (tontsattan) Q anew at a certain inception voltage. If that voltage la maintained or exceeded, theee dlacbargtc will normally build op Fig. S. -- ioateattaa pbeaemma la paper epaeed eepedten imprepuiod . elth eUeiteated itph--yl end wltt nlaand oU. 1, lealtaUen la mineral oO treated eepadter. X leatsaUea la ehlectaatrd dtpheayl treated eepeetter. l/,, Iteted vdUge ter hath opeettew. laeeptlea rettepee : A for mlnereft eO homed eapecMeri S fea eUartaate* bphoatH heated capoeHer. ' XntlMtian veltdgM : D ter adawal U treated eepealter. . In magnitude, but If the voltage la reduced, tba dlaeharcee will parent wttb much tba Mae Intimity until a mneb lower voltage la ranched, after which with mum further redaction In voltaf* tba fflintinrfte wfU atop. Thle last voitaft le known ea tho M extinction vefe^a It baa bean tba axpartaooa of ana of ue (5) that tba chlorinated diphenyl treated tnenlatkon bahavac more favorably than tba ad treated dletacmic with reaped ta tba lonlxatioa problem. Thle la Indicated dUtffnunmatleaUy in flgur* 5. Tba exact ebapa of tbaao carve* depanda an tba detain of manufacture, such h tba efftriency . 111. HONS 0345<r6 119 ot the drying and tb impregnation process, the purity ot the insu lating liquids, and the type of insulating paper which Is used. As illustrated In figure 5, the difference between the inception and the " extinction " voltage* for tho chlorinated diphenyl treeted capacitor dielectric le much lees than for the otl treated dielectric. 'Where substantial voltage surge* are likely to bo encountered in commercial service, as for example where tho capacitor Is connected directly to overbend line networks, this dlffersncs in tho relation of the extinction voltage to the Inception voltage of Internal ioniza tion for the mineral oU and tha chlorinated diphenyl impregnated capacitor is of practical significance. TRANSFORMER APPLICATIONS. An Inevitable result of continued progress In modern high voltags Installations la tha demand that tha Are risk accompanying tha use of mineral Insulating oil bo reduced or eliminated altogether. This Pig. 9. -- The seUdlfieattwa temperature of peataeUer dipbsayl ss iftottd by the presence ot tiiehlev beastas. A, pour point region', B, crystallisation ngM. has led to tho production of oU poor and dry type high voltage switchgear and to gw Ailed transformers and liquid Ailed trans formers utilising the nonflammable insulating liquids. Because the trauformer operating requirement tor liquid (Utod transformers necessitates tha use of such liquids ss coolants as well as lusulants, and at temperatures at least as low as -- 3o C, the nonflammable insulating liquids for transformer use are synthetic blends of chlori nated benseiM and chlorinated diphenyl. Figure 9 illustrates tha sotldlAcatlon temperature values of such blends as a function of MONS 03*547 --9-- U tba amotrat ot tha chiorlofliUd dlphauyl praacat. Flfnrt 7 liluttratas tha vtacositytampamura ralaUoo of typical oonflaaunabia transforatr Insulating and cooling liquids in eomaurdal ua. Tba Qvtraga charuataristka ol tueh liquid* an included in table L Because of (hair spodfie advaataf**, the manufacture and um of the nonflammable, liquid Silad tranaformar* la Ineraaauig and bacom* Utf mora wtdeaprted. In torn* areas, however, the purchase of Uala type 01 traoMforaar haa baen rlard*d because of Iti addtd coat as compared to a similar oO Mad unit Tha syntbetk Insulating Uquid la heavier and mora axpeualve than minatul transformer oil, but whan drawing comparisons, tha adraatagee of tha aanflaumabl* liquid mad tfuuafarnar should ooft ha overlooked.^ Tha initial coat of a transformtr la frequently not so deeklve a taataf at tba saving in Installation coats and tbo saving In space, matarlal and operating Soononep in Intonation. ~ For raasona of tafaty, enclosed, HONS 0345<r8 119 - 10 - solidly built and fireproof vaults witb propsr oU drainage an required (or tlia Installation of oil flllad translormars. In tbt United States, tbo rtqnlrtmtnta of tlia National Electric Coda o( tba American Standards Association tor oU insulated transformers installed Indoors reads as follows [9] : ' " OU Insulated transformers shall be Installed In a vault cons tructed as specified In this article except as follows ; M a. Nofooer tts.5 kVA fofaf capacity.-- The provisions for trans former vaults specified to this article apply except that the vault may ha constructed of reinforced concrete not lees than i Inches thick. A Not cost too V, -- A vault Is'not required provided suitable arrangements are made where necessary to prevent a transformer oil Art igniting other materials end the total transformer capacity la* one locatlen does not exceed to kVA In a section of the bufldiag does!lied as combustible or 7$ kVA where the surrounding structure is classified as Are resistant construction. " The normal vault construction called for by the National Electric Code (Amsrtcaa) except as indicated specifies that the " watts and rood of the vaults shall consist of reinforced concrete not less than 9 laches thick, masonry of brick not lorn than I Inches thick, of it Inch load bearing hollow tUe, or is Inch load bearing bellow concrete building units... " (7]. On the contrary, the requirements of tbs National Electric Code of the American Standards Association for Askars! Insulated trans formers Installed Indoors- eliminates the expensive Installation requi rements except as noted In the following paragraph (g): - w AskaroMnsuiated transformers rated In exeese of *5 kVA shall bo furnished a pressure relief vent. If installed In a poorly venti lated place they shall be furnished with a meant for absorbing any gases generated by arcing Inside the case, or tbo pressure relief vent shatt ho oenaootsd to a chimney of flue which wttl carry each gases outside the budding. Askerei Insulated transformers rated more than iS oeo V shall ho Installed In a vault. " For oil Insulated tranriormere Installed out-of-doors, the Notional ITIerirto Code of the American Standards Association carefully sporift-- the conditions ol Installation in order to mlnhntee the fire risk [9J. No restrictions of snob nature, however, are applied to the Aakarel Insulated transformer for out-oMoon installations. Under curtate dreumstaneee, therefore, the expensive vault cons truction can bo entirely eliminated by the use of Askarel Insulated HONS 034549 --11 lit transformers and the transformer can be installed Indoors, it on the factory Door, with only tho usual protective fuarda to prevent contact with the live parte of the transformer. Economy hi operation. -- Because of the freedom permitted In the selection of the site for the traaaformer Installation when the nonflammable Insulating liquid to used, the transformer can be brought much closer to tho point of powee consumption, thereby reducing the power loesee which ere normally incurred due to the longer cable connections which are necessary when mineral ell DUed transformers are used. It has been found (10) that for every tooo m (S s5o feet) saved in the length of low voltage oaMe there results an added savtng of about 0.4 to o.j % In tha elec* Ortoal power transmitted. A further economy la the operation of tho nonflammable, liquid DUed transformer results from tha ettmlnatloa of tha problem of oxidation to which tho mineral transformer ofl to susceptible. The nonflammable Uquld Is uou-oxldtotag sad during operation forma no moisture or Uquld Insoluble products similar to the formation of ofl sludge. Sludge deposits on tho windings and heat dissipation turfacee of the Aekarel DUed transformers to therefore imposeIblo. With e nrooerlv constructed transformer containing tha nonflam- maSU and using 0>a air Hghisaaiiacoagtructlonor lUtFetlMi*or^sq^^^ceplncvnient1^ tha uquB~which Is geneiaSy "tha practloa'wtth mineral oU' flllad tHB*fbrias Is sliaflnatst TIE PROBLEM OP hCTARETd COEVTAXnfATXON. Tba eyntheUe, nonflammable Uquld dielectrics ere characterised by a wider range of solvent notion than to mineral oiL Tba result to thnt carafal attention must be given tba selection of other insalatiag materials and Insulating vamtohee to prevent their degmdatien en doe to tho presence of them materials la liquid solution. la general, it has been found that most of tho vegetable oil typo varnishes are attacked by tho eynthetle, nonflammable liquids. CMMltJv "trt tTM'Wttl `-""I 'boohoaoUcroom. tho Incnua tlMlr MaeopUblUty to ottock by tbo ijithatie Uqvldo. Tho omul c.flolMki laudation rack oo Knit popor, Uaoa popor oak oottoo popor nut tbo cord* and prouad boards mndo from took c.UuloMc MOMS 034550 119 -- 12 pulp* art suitable for u with tb same degree of acceptance quality control a* 1 normally exercised In their oe in mineral oil oiled apparatus Mineral oil te soluble In Uieia nonflammable liquids and lta pretence may affect the nonflammabUtty of the synthetic liquid and Introduce a degree of exploiivity in the gate* formed by tbe action of an electric arc. In accordance with the finding* of the Underwriter*' Laboratory of the National Board of Fire Under writer* (American), the permissible amount of mineral ou in trans former Askerel doe* not exceed 3 % by volume of the Askarel (H). The effect of oonmninetbw la Aakarol filled traaaformare. -- The problem o! contamination retuiting from the solvent action of the nonflammable liquid* on the insulation* and structural mate- ftg. i -- limning the bm of ea activated ahnataa rvoondlUoaer lor the leawvel of Impurities derlag the operation of the Askars! filled transformer (Courtesy of tbs Predslse Company). rials uaed la the manufacture of such equipment rarely If ever concerns the dielectric strength of the liquid. The effect of contamination, bewever, may be pronounced when viewed from the standpoint of HONS 034551 - 13 - 119 tb dlalactrle low. Contaminated liquids of tha synthetic, nonflam mable typo Invariably show an Ineroaaa la dlaleetrie loss, to an extent which la chiefly dependant on the typo of malarial prosant la liquid Pteleetrts (trMfta. IMthity. eolation. resettle contaminants in traaafaraar manniaetnra include laminated atnwtnvaa and tha Uha. ITmtiiearing eara must bo euar* dsod to provan! tha contamination of tha Inanlatlng liquid bayoad that Uaattatioa Imposed by good engineering practice. HONS 034552 119 -- 14 -- It has been found by experience that despite the careful selection of commtrciaUy available materials, a tread toward Increased dielec tric low (a the liquid of the Aekarel filled transformer will occur during the early stages of the operation of the unit In sendee. This change in dielectric lost hae been demonstrated to be of little If any practical significance by the excellent operating record of this type of transformer, but even this tread of change can bo eliminated by the use of activated alumina either placed inside of the transformer or in a separata container through which the dleieetrie liquid is caused to circulate (!3|, (13). Its application to the nonflammable liquid filled transformer Is illustrated Ln figure t which show* the estivated alumina container attached to a 7 5oo kVA, to 5oo V power transformer Figure 9 illustrates both the behavior of the Aekarel in the transformer before the circulation through the acti vated alumina waa started end the effect of such circulation during subsequent yearn of tha commercial operation of Urn transformer The details of the eonstruettaa, rating and testing of this trans former art aa follows: Kve capacity............................................ Voitege reilag.............. .......................... M | ""** Sarga teat.*.,,......,........................... Caotiag....................................................... Conservator.............................................. Baehols relay aeed................................... Aakarei used.......................................... Weight of aikartL.................... .............. Ankles* tejapereture of operation........ Service use............................................... guinea teaaperatore of eckarel... Activated ahaniaa container............. Weighs of Mtiveled aiewiae.......... Ctvealatfo* of where)...................... . faMel service (wHhaat ahmlas).... CJrealstioe thMagk eluesiae tuned. 7 toe HlMtlX/isV '41 kV te kV jio kv Natural cooiieg tkrougk redieton Pilled with eektrtl, eh drier Pvreleae to Joe kg <s* lie lbs) --s5C te --3S*<2 Coatieaoue service feeding power ta ee eleetreiytte factory . hC Dlearatar Mo win <93 ieebee), height 1 Mo am (Mlethea) 15 bg (1I7 lha) Thermo siphon Jeeoarv 17, 1951 Mirth 1, 19*4 In figure 9 data are given for the dielectric strength, tg t end the ittMvtty of the- Pyrelene daring the Ufa of the transformer to date. HONS 034553 -- 15 -- 119 These measurements were mad* oa samples composed of equal amounts at the liquid drawn from tha tap and the bottom af tbo transformer. Tba dlalaetrlo itran|th value waa made la aaear daaea with tha taat requirements specified bp tba American Sodety Car Testing Materials (161. Tha tangent al tha aafla ol didectrte wu maaaurad at coo* C uadar s6.6V/oun (a.66S v. p. m.) with a frequency of 5o cycles/. Tba resistivity waa maaaurad at too v/nun (5 . p. ol) altar t mlauta al electrification at too* C. la addition to tha data Illustrated (a d|ora 9, additional valves wero maaaurad far tha acidity, color, refractive index, ehlorlda laa coataat and moisture ceataat ol tha AskareL Tha raaulta obtained In this type of tasting Indicate (a) no loss duo to evaporation, (*) no decomposition of the chlortnatad molaeuloa, and (a) no change in tha mototura content. Tha slight incraaaa la liquid addlty (0,0*4 to a.013 Mg KbH/g) which waa noted daring the period of operation before tba drcolattoa through tbo activated alumina was started baa bean eilmlniftd (peasant aridity valna 0.00s) along with the color Increase which Is now being maintained at a valna of So (AM). Crmtanrtncrion la Aakarol fitted oapndloee. -- As la mineral oil impregnated eapedtore, tha praeanca of molsturo la the Aaharei Imprognatod capacitor lneraasaa the dielectric iocs ttader A. & veitags, and dccraniic the capacitor Ufa. The lowest possible energy laaaoa and tba loagcot capacitor Ufa la practice are therefore only obtained with tha lowest residual aolstaro coataat which Is obtainable only by tha as# of the moat eOrient drying procimoo during the moan* feature of tha capacitor. . MoivturCi bowovar. Is only one Impurity which may bo present la tha llqaM Impragaatad capacitor. Any ether substance that disanlva la tha Impropaat and la dissociated thereby lata positive and negative leas la liable to havu a harmful affect on tbo dlaioetrio loot of the capacitor. Evan tha dipolar structure of tha Insulating paper normally osod Ut. capacitor manafneturo has boon shown by om of as (17) to have a pronounced affect on detonalniag the lam characteristic of both tho oil and tho Askarri bapragaatod aaparitor at tha hlgbaat and lowest temperatures of possible application (/If, 4). Tho prasaneo of lonlsablo contaminants dlssolvad la tha Askanft Improgaant af tha aaparitor. however, may have a marc significant effect on the dielectric loss of the capacitor within tha normal temperature range of commercial operation. Probably tha meat sensitive test for tho presence of dissolved Imparities which effect the dielectric Iocs end usability of tho Aakarol treated capacitor Is a teat for the variation of the dielectric leas with applied voltage at an elevated temperature, la a capacitor uaeontemlneted Aakarol Impregnant, tho losses (tg t) MON$ 034554 119 - 16 - are substantially constant at all voltages op to the limiting value where internal discharges begin, beyond which the value of tgt Increases. If the Askarel Impregnant be contaminated, however, (he value of tg I measured at normal room temperature will show an changing value throughout the entire range of voltages used, below that which producer Internal discharge. If this test be repeated with the capacitor heated uniformly to a higher temperature, it will ha found that there will occur a pronounced maximum value of the lorn* at same intermediate voltage in the test range. Figure 10 MaHatee the remits obtained at two different temperatures {5). lie actual voltage at which this maximum value occurs la a function net only of the total dielectric thickness but also of tha viscosity of the Impregnant at the temperature of the test (11], The curves of figure to showing the pronounced maxima in the tg* -- voltage relationships are typical of tbo contamination of the impregnant. The magnitude of the " hummock " is an Indication of tbs " efftc* ttveneu " of the contamination. It has been observed that very MONS 034555 - 17 _ n. jmU amounts of a harmful malarial tn tha Aakanl may raiult [a paak valuta of t| i a or 3 tlmas IU normal valno at ratad voltage. F*. it. -- Ca--artaa tha iflai of voKaga m___ f ntataaritin* aa* aatadundaitt* Aafcanl tnato* K aaatafala* aapaottant 1, UntoataadMla* U,, Rata* aapasttar toUaga. ............... Sa*C| Mac. (H If whatantlal amounts at contaminant art prtaaat, aitnmaly high vainaa of t|< may ba obttrved at la figure tt. in tha eapadtor HONS 034356 149 -- 18 -- tested in Agure ii, the Askarel was contaminated with a small quantity of an elastomer recommended for sealing the capacitor can. Tha peak tg * value Is approximately o.o3 at 8S C. whereas the same type of capacitor when impregnated with the uncontaminated Askarel showed a peak value of only o.ooi |5). From the Illustrations given it might be concluded that the presence of the Askarel contaminant is not of practical and dangerous effect when the capacitor is operated at rated voitage ((/,,). Such, however, is not the case* When such contaminated capacitors are operated continuously at their normal rated voltage,'the losses soon commence to Increase at that voltage stress also. When this occurs, ultimata fallurs of the dielectric Inevitably results because of thermal Instability. . THE PAPER SPACER. In the foregoing discussion It has been Implied that the source of the materinl which may contaminate the Askarel lies in the use of an improperly selected varnish or resin, or in the presence of a foreign material introduced In the gasketing or sealing operations, or by the materials used in soldering or welding, or picked up by the Askarel during factory handling or shipment, or from some other M accidental " source. Contamination of this typo is Important, but accidental effects of this type are not the only significant sources of trouble. The contamination of the Askarel may arise from the ceilulosie insulation Itself. Cellulose products are used widely In transformer and capacitor construction in the form of insulating papers, tape*, cloths, cords and pressed boards. It has long been recognised that proper care must be exercised In the selection of the ceilulosie insulation used in the construction of oil Ailed apparatus. The same degree of care mutt be exercised in the selection of cello* losle Insulation for use In Askarel Ailed equipment. This Is espe cially true In the case of capacitors where increased dielectric loss arising from the use of unsuitable papers or pressed boards may lead to overhoatlng and dielectric breakdown. The quality control of tbo insulating papers usually involves chemical tests for the characterisation of tbo paper Aber and tha purity of tha pulp fig), supplemented by physical and electrical teats to insure the quality of the paper sheet. In many casee, the dielectric lots of the Impregnated paper corresponds to the loss In the dried hut unlmpregnated paper, but experience has shown (201 that with tho Askarel impregnated paper thle relationship is not always sustained and that higher loss values increasing rapidly with temperature may be exhibited by certain Askarel treated papers; *ONS 0 - 19 - . U9 Examination ol the Askanl treated papr la necessary to eliminate the use ot M contaminated " paper ol Uala type. An Illustration ol tiio problem presented by differences in tbroo commercial capaeltor papery la presented by tha teat results given fig. ts. -- The effect el tennati > the leeeee la eapaelter papers (30). AtotitnaCw One fflsreat (4M> ceparitsr papm (dsmtty m>i A* B| aad C* mum papeca after fyralaaa lafficgaetlm A* B( end G fjilici after ticetad paper tester to Ifen is (30). to ebtalnlnf these rcaalta tba (ottowing procedure m used : I. Tba Kraft papers used were from throe commercial lots ol capadtor paper, each Paving a spedffe gravity of 0.9. . 3. The papers to be tested wen assembled to pods 0.1 mm (0,004*) thick. 3. The paper pads wen dried at io5C under a presian lower than 1 am for a parted ef ith. 4. The Aakaroi need wee 1470 Pynlea*. ft. The Askan) was approved ter tin oa the basis ot Its resistivity and lose angle values. HONS 034558 lid -- 20 -- 6. The Askarel was degassed and introduced in the evacuated impregnation vessel at a temperature of no* C. 7. The vacuum was broken by meant of dried air and the impreg nated papers were allowed to stand at atmospheric pressure for t$ b. 8. Electrical measurements were ail made In a special cell which 'also constituted the drying and Impregnation chamber. No expo* sure of the dried paper or the dried and impregnated paper to normal room atrtiopsheric conditions was permitted. 9. Electrical tests mi the Askarel Impregnated papers were made with a Scherlng Bridge at a voltage stress varied up to 5 volts per micron (is? volte per ml!) at go cycle frequency. 10. Electrical tests on the dried but untmpregnated papers were made at i volts per micron (5i volte per mU). j j from the data illustrated In figure i *, It will be observed that the / /dielectric loss in Askars] impregnated capacitor paper may In some / / Instances be much higher than the losses to be anticipated from m*a* l I ursrasnts made on the dried paper before Impregnation. Tests on the ` { Askarel made after Its use in the impregnation of the paper showed no abnormality which would he Indicative of the presence of soluble contamination. These test results are supported by the examination of commercial capacitors In which these papers were need. Capa citors made with paper B and with paper C were each characterised by higher losses after drying and Impregnation than would have been expected from the measured losses of the papers before impregnation with the Askarel. The quantity and nature of the constituents in Kraft paper which are the basis for the abnormalities observed are . not yet able to ha specified by chemical analysis. Measurement of . the fosses of the Askarel Impregnated paper dielectric Is an Important supplement to the physical* chemical and dielectric teste usually l made on the unimpregnated paper. ' THE DIELEGTXUC STRENGTH UNDER SURGE VOLTAGES. The power frequency voltage breakdown of the Askarel and the Askarel treated Insulation is equal to and in many instances superior to the breakdown ot mineral traneformer oil and the corresponding oil treated Insulation. However* in transformer construction, the surge voltage breakdown of tho Insulation treated with Askarel it (equal to tho sorgo voltage, breakdown of insulation treated with mineral oil of like viscosity only when the electrical held Is uniformly HONS 034559 -- 21 -- 119 applied or when small insulation thlelmosMs era ueed. For large gap distance# or with thick layers of the Impregnated insulation tested with surge voltages under conditions which eaaso a aoauaiform distribution ol the voltage stress* the sorgo voltage breakdown of the Aakarol and Aakarol txoalod insolation to lower than that of tha corrospoadlag oO or ott treated dielectric (28]. As in the case of a gas Insulated transformer* the eolation of this problem Uos In the derige of the transformer. Those transformer designs which give the greatest uniformity la the distribution of the applied voltage favor the highest wage voltage breakdown Taines for the Aakarol to mosuM or stdaoosn chloride. In the normal operation at the Aikerel Ailed transformer, sleniilsnl arotag beneath the snrtnos of the Askarel does not occur. However, daring high voltage testing* corona may br formed. Forthonnor*, despite the eneeOant service resold of the Askarel filled transformer* ever many yean, stestrteal breakdown during the commercial ass of the transformer mny ooenr. It to well reeognlsed that an deetrleal am will save tha molecular breakdown of mineral eQ. U also causes the meioealar breakdown of AskaraL In alnaral oil, sneh breakdown rssnlts In tho formation of carbon itndgo and gases sneh as hydrogen* methane, acetylene, carbon monoxide,' and other flsiuinahli and toxlo veiatDo matartato. la Askaral, breakdown under the eUetrtc era produces earbon and hydrogan chloride gas. The volatile products formed from tho docompostttou of mineral ott by the ilsetrk are Infrodnee e degree of flammability end esplostvtty which to aheent whsn the Askarel liquid Is decomposed. Hydrogen chloride to neither Osmmebls aer uplodm But hydrogen chloride may be eonwh* fan tha prsssnes of moisture. Experience has hewn that a dlstostoto failure In an oil filled transformer is frequently repairable without serious degradation of the properties of the etOnloste InsnlaUon. Experience has alee ehown that when dlolootrio breakdown seen bsnsath the smfase of the liquid In n Askarel filled tnufovmer* the hydrogen chloride formed may attaek the oofliloeto tasulatlens preoeut. Serious degradation of thsoo insu lations may be earned by tbs slew attaek of tho hydrogen chloride dfssolvid la the Askarel liquid. This degradation of tbs ctUnlosio Insnlattsn can bo sHutfnotod by tho presence of n ** gorier " dtoeetved m tho Askarel fht). A * gsttar * to defined as a material which whsn pcssrat In tha Askarel at tho tlmo tho insulating liquid to decomposed by the ctoetrte are will react with tho hydrogen chloride HONS 034560 m -- 22 -- and eliminate the possibility of U reaction with the Insulating and structural parts of the transformer. Such a material has no func tion In modifying the normal dielectric bevavior of the Atkartl under normal operating conditions and becomes effective and of significant protective aetlon only when hydrogen chloride Is formed es when an electric are has caused decomposition of the Askarei. Since the " getter M Is present during the normal commercial use of the trans former, It must possess good dielectric properties when dissolved in the Aikartl and mutt not diminish Us freedom from fire nor detract from the nonexplosive quality of the arc formed gases. Such a material la tin tetra phenyl [22]. When dissolved In the transformer Askarei to an extent of about o.i5 % by weight, tin tetra phenyl gives adequate protection against Use degradation of the structural and Insulating members of tbo transformer [24]. THE USB or STABILIZERS. In the normal use of Askarei In A. C. voltage capacitors and In transformers there to no necessity for the us# of a stabiliser of any type. The chemical stability of the Askarei and Its freedom from the possibility of oxidation,. unUko the behavior of mineral oil, removes any necessity for Use use of antioxidants or retarders which have feen found desirable In certain typos of oil filled transfonneri. Under D. C. voltage, however, the Ufe of the Askarei treated capacitor has boon extended by the use of a stabiliser (12). It is believed that when the Askarei treated capacitor paper dielectric Is operated under high values of D. C. voltage stress, there Is a small hut significant degradation of the Askarei which affects the perfor mance of the capacitor la D. C. voltage (tee. Such a stabiliser is anthraqulnone and its chlorinatad derivatives. ' . THE USB OB ASXA1UELS AT LOW TEMPERATURE. For the operation of the Askarei capacitor at low temperature In ease* whtqp the capacitor to not continuously energised, the use of peata chlor diphenyl has not boon found to give a completely satis factory performance. During periods when tbo capacitor Is off voltage, tb Imprognaat may solidify with resultant mechanical motion and the possibility of void formation within the dlelectrie structure. In some cates, capacitors Impregnated with penta chlor diphenyl have failed electrically when the normal capacitor voltage wee rtappUcd after a period of time at temperatures below -- is* C during which the capacitor was not energised. By the use of trichler lit dipt--n r atotwaa of ft aolaatod chlorinated dlpboayi tad tvtefctor bMMM aft ttft laprafnaat, Aftkftrtl Mod eftpftdton eta b twitched ad od ootftfa wtth lapmnMy at teapontnm a* few m -- * c ad lawar. Ha fthftfwtariittoa of trichtor dlphMyt whteh ara aatUMt for aacfc apphraUcaa aw plv-- li the data ol tebte it Tboao proportion of my atafto maaircHI toarea of t taau II. DU mm+ff proportfat t/ irtthbr fykmyl tmmUa /or an to MpMton tmkjtm ft law iMm< ftm^ntfam. Caadkteft (*iC>...................................... Ciltt........................................................ Add ftlM (ap KOB,'(>.................... !!.. 1 Pooo thlotidt too.... *.............................. SpaaMa pn*ty <a9*C).............................. Foot potoa (*C>....................................... I (>7.fC)..................................... VhaaahW <.)................................. I (ioaC).................................... Spaatfa boat (af*C) (l/r*C).................. Cool of aftpiftilaft (aM5C)J.................... Haftt aoftfftWitky (|o*C) (kaaVa/W*C).:. Rafraadra ladat (aoC) (D)...................... Moteatite Mroftfth (ao'fftC): (kV/aaHV.IM.)................................ v.p.m.<a..t;n.)............................... DMoairfo aon--I*.................................... SpaaMa laatowaao (ao*C) ((Ha)............... Powar tetter (pa*C).*................................ Qaftf PraaMoalljraateHata <a.oi ?(H i.9* --if to --wrC *9(9. 9.1., 31(5. i.iS* (K) yxiar** i.*9 3So S.o-I.p (*S*C> i.7*(.f(iooC) Sxio** o.oiS Tha Aafcawf twlPtf Mftt pawaa vary tow order of tottetty who* haaiof la aoootdaaoo wttk aoroud practice to too Idtod ttoul my wt *--a ifcto lnttftttoa. If ti npota fra tho tat aaftartada ara hrahad ftoar ft wirtutly loot parted of ttto tMM aflaotft Mp raK. Tbo lawar order of votatOtp of tfeo aototoareM Aakaiate a* raptrod with sort chlorinated matt- 0ji*5<>2 rtOi*s 119 -- 24 -- rials in commercial um (chlorinated othylsne) protects against abnormal personnel dimcultlet. Despite this and especially whan Mm heated Askarab are handled in opan containers, good ventilotion of tha atmosphere should ba provided. Hydrogen chloride, which to formed only when tha Albania ara decomposed at by an aloetrtcal an, i a toxic gat. It to to ba pointed out, however, that tha exceedingly unpleasant and Irritating charactertotle of hydrogen chloride acts to glee adequate warning of its prosenes even in very small concentrations, thus preventing tha dangerous exposure of persons. It to suggested by the Underwriters' Laboratory 111) of the National Board of Fire Underwriters (United States) that " the resulting concentration of hydrochloric grid In air when; failure of a transformer or other electrical apparatus contain ing these products occurs win depend largely upon the conditions. It will constitute a toxic hasard only where the oondlUona ara such as to causa a high concentration of tha fumes, as In a closed roosn In accordance with this finding, the National Electric Coda of the American Standards Association as already stated |6), permits the installation of Aahnrol Ailed transformers up to ifoooV rating without the Are vault protection reqiired tor oil AIM tranafnimsn. but tha coda does require that la poorly ventilated areas, means shall be provided tor carrying of! the gases evolved in case tha transformer should fall electrically. Rnrsaswcxa. 1. Twtattm mstted of testing Adrarek (A.S.T. M. Derivation . D BOt-AAT). - . 2. F. M. Claus; The dmhpmmt and application of sgnrtrik ffguM diskettes (Trans. Amir. BMntkun, See., vol. 65, igJ4 p. ipVaoOb S. F. M. fasta, Diskette material /or rtedrfraf dities (U. S. Patent 1.631.873). . 4. F. M. Class, The steetteaf tosebdewn of Hgnfd dtetesttet (J. FranMta Mst, voL 816, 19IS, p. |>pi|JI). 5. Philip R. Covwri, 6. Ndftenal Bkrirte Cede, American Standards Asoodatlon (iff6), Article 460, Sorites 4363, p. tSd. 7. National JMsstte Cods, American Standards Association (ig54), Artlcli 460, Section 4649, p. 1S7. 1. Notional Bhetrt* Cod*, American Standards Assodatloa (igfg). Arttcla 460, Soetten 4629, p. i56. 8. National Slottrio Cede, Amerioon Standards Asoodatlon (ig54), Artida 460, Section 4694, p. i5j. HONS 03,563 25 -- 119 10. J, Kuhssmann. (Uophrn transformers (4. li. Progress, i<jj7, No. 1, p. 38). 11. Dielectric and canting medium admired with small amounts of transformer oil. Mil `2581. 12. I*'. M. Clark, Prr/onwmce r/torneferMfc* of the \skarch (Special Technical Publication, No. 1)5, i<>1o, p. 3-ao, Atnciicnn Society for Testing Materials). 13. F. M. Clank, Stabilization of halogenatcd hydrocarbons (C. S Patents 2 501872, 2 504 873, 19 V/;. 14. J. )\. Hoiiski.ky, Reconditioning of insulating nils by activated alumina (.1. /. H. E. Trans., vol. 08, iy3'i, p. 177-17.1). 15. M. Gu.on, J'rOinte Conirminieatton, l.n Soviclt Prodrlce, Parti. l'l'ntice. 16. Standard method of fesi for dielectric strength of insulating oil of petroleum origin (A. S. T. M. Designation D 877-49). 17. F. LutnsciiKJi, Power capacitors for low and high temperatures (hlektrixitalswirtschaft, vol. 50, 1937, p. 145). 1$. C. (i. Gahtom, Dielectric loss in thin films of insulating liquids (1.12. E., vol. 88, 1941, p. 103-170). 10. II. II. Hack, H. J. IIbmpiiii.l and 11. S. ISndicott, Im/toriunt properties of electrical insulating pa/iers (Gen. Hied. Pm., vol. 43, No. 12, p. {97-499). 20. F. ViAi.ii, 21. F. M. Clark, Jiirr/r/col f/isuloiio/r, a field for chemical exploi tation (Cheat. and ting. News, vol. 25, 1947, p. 1976-1978). 22. I1'. M. Curk, Stabilized halogenatcd compositions and electrical device (U. S. Patent 2 468 544, 19(9). 23. T. W. Dakin and C. N. Works, The impulse dielectric strength charaeterislfes of liquid impregnated pressboard (A. I. I'., K. Conference Paper, 1953). 24. F. M. Clark, Ctamfafry and life elnlrical engineer (Gen. Elect. Rev., vol. 54, ig51, p. 11-3I). I'KtraU de In CoR^ftorr JoternnHumiie tfrs firomi* fltoaitx fclrelriqur*. Smloti 1968. HONS 034564 PAWS. - 1MPWMIMI GAUTRIIWTILUM Qwti 4* 6rM4tA*fUtiM, 1$, 1S2SUS1 toprtMt Fmmi 034505 HONS