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Unformatted text preview: IEEE TRANSACTIONS ON ELECTRICAL INSULATION, VOL. EI-9, NO. 2, JUNE 1974 Kerr-Effect Studies of an Insulating Liquid Under Varied High-Voltage Conditions ESTHER CHRISTMAS CASSIDY, SENIOR MEMBER, IEEE, ROBERT E. HEBNER, JR., MEMBER, IEEE, MARKUS ZAHN, MEMBER, IEEE, AND RICHARD J. SOJKA, STUDENT MEMBER, IEEE Abstract-RefinedKerrelectroopticalfringe-patternmethods are usedtostudytimeandspacevariationsintheelectricfieldbetween the electrodes of parallel-plate capacitors filled with liquid nitro- benzene.Photographsoffringe-patterndatarecordedduringapplica- tion of high direct (both positive andnegative)andsinusoidal voltages, ranginginfrequency from 40to200 Hz, are compiled to enable computation ofspace-charge distortionsofthe fieldinbulk oftheliquidduringthestressofhigh-field(upto85-kV/cm)opera- tion.The measurements revealsignificantdifferencesbetween the fieldand charge behavior under shortpulse (microsecond) voltage conditions, duringprolonged dc operation, aftersudden changes in thedcvoltageleveland polarity,and,forthefirsttime, atvarious intervalsoverthecourseofentirecyclesofsinusoidalvoltage.The resultsshow thatspace-charge distortionintheinterelectrodefield isinfluencedbythelevel,frequency,anddurationofappliedvoltage. Discussions of effectsbelieved due toparticulate charge carriers, to electrohydrodynamic motion ofthe liquid, and tothe electrode materialsarealsoincluded. I. INTRODUCTION R ECENT WORK has experimentally demonstrated theusefulnessoftheelectroopticKerreffectforthe determination ofvarious electricalparameters under the influenceofhighvoltage. Among thesearethemeasure- ment ofpulsed high voltage -,thedetermination of space-charge effects in nitrobenzene - and chlorinated biphenyls , the measurement of the electric-fielddistortioncausedby theinsertionofasolid dielectricina liquidinsulant , the measurement of 60-Hz alternating voltages , and the observation ofthespatialand temporal variationoftheelectric-field distribution caused by pulsed and direct voltage - .Inaddition,theoreticaladvancesintheunderstand- ingofspace-chargephenomena ininsulatingliquidshave beenmade insuchareasasthepredictionanddescription ofbulk space charge  and polarization waves  in charged-liquid systems and the role of particulate chargecarriersinelectricalconductance . Realizing that further advances are predicated on a knowledge of electric-field and space-charge behavior in Maniuscript received September 21, 1973. This work was sup- portedinpartby theU. S.Atomic EnergyCommission throughthe Sandia Corporation, Albuquerque, N. Mex. One of the authors (M. Zahn) received partial support from the National Science FounidationunderGrants GK-27803 anid GK-37594....
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