THE INSTITUTION OF ELECTRICAL ENGINEERS | ] IEE PROCEEDINGS-A Science, Measurement and Technology Vol. 138, 1991 Published by The IEE, Savoy Place, London WC2R OBL, United Kingdom Publishing Department: Michael Faraday House, Six Hills Way, Stevenage, Herts. SG1 2AY, United Kingdom IEE Proceedings-A Science, Measurement and Technology The Institution of Electrical Engineers, Savoy Place, London WC2R OBL, United Kingdom Publishing Department: Michael Faraday House, Six Hills Way, Stevenage, Herts. SG1 2AY, United Kingdom Volume 138 1991 UK ISSN 0960-764X HONORARY EDITORS Dr. G.W. Chantry (/nformation Technology Transfer Consultant) Dr. M.J. Cunningham (University of Manchester) Pages in issues of /EE Proceedings-A, 1991 Pages Issue No. Date 1-100 January 101-144 March 145-204 3 May 205-248 July 249-288 September 289-336 November This publication is copyright under the Berne Convention and the International Copyright Convention. All rights reserved. Apart from any copying under the UK Copyright, Designs and Patents Act 1988, Part 1, Section 38, whereby a single copy of this article may be supplied, under certain conditions, for the purposes of research or private study, by a library of a class prescribed by The Copyright (Librarians and Archivists) (Copying of Copyright Material) Regulations 1989: SI 1989/1212, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means without the prior permission of the copyright owners. Permission is, however, not required to copy abstracts of papers or articles on condition that a full reference to the source is shown. Authorisation to photocopy items for internal or personal use, or for the internal or personal use of specific clients, is granted by the Institution of Electrical Engineers for libraries and other users registered with the Copyright Clearance Center Transactional Reporting Service, provided that the base fee of $3.00 per copy is paid directly to the Copyright Clearance Center, Inc., 21 Congress Street, Salem, MA 01970, USA. 0960-764X/91 $3.00+0.00. This consent does not extend to other kind« of copying, such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. Photocopies of individual papers published in the /EE Proceedings can be supplied from the IEE Library at 10p per page plus a handling charge. The telephone number of the IEE London office is 071 240 1871; telex: 261176 IEELDN G; facsimile: 071 240 77 35. The IEE is not as a body responsible for the opinions expressed by individual authors. The IEE is a member of the Association of Learned & Professional Society Publishers. © 1991: The Institution of Electrical Engineers Secretary of the IEE: J.C. Williams, PhD, FEng, FIEE Managing Editor: Gill Wheeler; Assistant Editor: Fiona MacDonald Graphics Manager: Maurice Partridge Typeset by: Santype International Limited, Salisbury, Wiltshire, United Kingdom Printed by: Unwin Brothers Limited, Old Woking, Surrey, United Kingdom index ABBREVIATIONS IEE Proceedings-A Science, Measurement and Technology paper, address or lecture discussion on a paper abstract of paper or address errata synopsis of a paper published in full in Vol. 138, 1991 another Pert of the IEE Proceedings Author index G M German, D.M., Haddad, A., and Elayyan, H.S.B. Makin, B., and Hu, D. see Hu, D. A see Haddad, A. Makin, B., and Hu, D. see Hu, D. Goksu, ¢., and Giines, F. High frequency surface Mandal, A.K., and Konar, A. see Konar, A. currents induced on a soft-hard cylindrical strip Martin, P., Knight, R.B.D., and Legg, DJ. see Al-Bawy, I., and Farish, O. Charge deposition on Pp Knight, R.B.D. an insulating spacer under impulse-voltage condi- Giines, F., and Goksu, ©. see Goksu, C. McGhee, J., Henderson, 1.A., Szaniawski, W., and tions pl45 Gundrum, H., Rizkalla, M.E., and Michel, H. see Domaradzki, P. see Henderson, I.A. Al-Bawy, I., and Farish, O. Insulator flashover in Rizkalla, M.E. Michel, H., Rizkalla, M.E., and Gundrum, H. see SF, under impulse voltage conditions p89 Rizkalla, M.E. Allen, N.L., Boutlendj, M., Lightfoot, H.A. and H Montaifio, J.C., Ibafiez, M.C., Ojeda, A.L., and Neville, R.B. see Boutlendj, M. Benitez, J.G. Measurement of the load admit- Allen, N.L., and Boutlendj, M. Study of the electric tance and reactive current RMS value in the fre- fields required for streamer propagation in humid Haddad, A., Elayyan, H.S.B.. and German, D.M. quency domain p138 air p37 ZnO surge arrester elements with mixed direct Morrow, R., Murphy, A.B., and Powell, KJ. see Antonopoulos, C.S., Panas, S.M., and Kriezis, E.E. and 50 Hz voltages p265 Murphy, A.B. Transient electromagnetic shielding in a system of Hann, R.A., and Webb, P.W. see Webb, P.W. Murphy, A.B. Pewell, K.J. and Morrow, R. two coaxial cylindrical shells p281 Harid, N., and Waters, R.T. Statistical study of Thermal treatment of sewage sludge by ohmic Ari, N., and Blumer, W. see Blumer, W. impulse corona inception parameters on line con- heating p242 Auckland, D.W., and Varlow, B.R. Dependence of ductors pl61 electrical tree inception and growth on mechani- Henderson, I.A.. McGhee, J., Szaniawski, W., and cal properties p51 Domaradzki, P. Incorporating high reliability N into the design of microprocessor-based instru- mentation pl05 Howe, A.F., Barrow, D.R., and Cook, N. see Naidu, S.R. Time domain model for the ferromag- B Barrow, D.R. netic core, including the effects of hysteresis and Hu, D., and Makin, B. Study of a five-electrode eddy currents p44 Barirstorwy, ofD .eRl.ec,t rHico wfeu,se Aa.rFc.i,n ga nd p8C3o ok, N. The chem- aqsupaedcrtusp olpe3 2l0e vitation system. Part I: Theoretical Nevfiololte,, HR..AB.. , seBeo uBtoluetnldejn,d j,M .,M .A llen, N.L., and Light- Hu, D., and Makin, B. Study of a five-electrode Benitez, J.G., Montafio, J.C., Ibafiez, M.C., and quadrupole levitation system. Part II: Experi- Ojeda, A.L. see Montaiio, J.C. mental results p329 O Binns, K.J., Liu, Z.J., and Vourdas, A. see Liu, Z.J. Hui, S.Y.R., and Christopoulos, C. Discrete trans- Blumer, W., and Ari, N. NEMP- interaction with form technique for solving coupled integro- plane multilayer structures p199 differential equations in digital computers p273 O’Connor, W. Forces on semi-infinite overlapping Bond, L.J., Shiloh, K., and Som, A.K. see Shiloh, K. rectangular poles: infinity permeable against Bond, L.J., and Clark, R. see Clark, R. saturable case p176 Boutlendj, M., Allen, N.L., Lightfoot, H.A. and Ohki, M., and Saito, S. Effect of a magnetic field on Neville, R.B. Positive DC corona and sparkover I low-pressure gaseous breakdown along the in short and long rod-plane gaps under variable surface of a solid insulator p300 BBuo,uh tulWme.inHdd.ij,t, y aMnc.do, n dFaiantndig o,An lslM e.nT,. pC3N.1. L.s ees eeF aAnlgl,e n,M .NT..LC.. IbaBfeienzi,t ez,M .JC..G,. seMeo nMtoanftiaoj,i o,J .JC..C . Ojeda, A.L., and OOjnegBdaeanr,io t,e zA,. RL..J,,. Ga. nMdsoe ne tPaMifloilnootn,an ieito,J ,.C .A,J. . C.SI ybanftiheezt, ic M.tCh.e,o ry anodf Ikejiri, T., and Kawamoto, A. Erosive failure caused by surface discharge on the surface of epoxy resin Poole and Poole—Frenkel (PF) effects p127 Overshott, K.J. Address as Chairman of the IEE immersed in insulating oil p288 Science Education & Technology Division: Mag- € netism;i ti s permanent p22 J Carpenter, C.J. Electromagnetic energy changes due P to charges moving through constant, or zero, magnetic field p55 Jones, D.A. President’s Inaugural address: Electri- Christopoulos, C., and Hui, S.Y.R. see Hui, S.Y.R. cal engineering; the backbone of society pl Panas, S.M., Antonopoulos, C.S., and Kriezis, E.E. Clark, R., and Bond, L.J. Response of horizontal Jones, G.R., Taylor, S., Fang, M.T.C., and Shimmin, see Antonopoulos, C.S. axis eddy current coils to layered media: a theo- DS. see Taylor, S. Pillonnet, A., and Ongaro, R. see Ongaro, R. retical and experimental study p248 Powell, K.J.. Murphy, A.B. and Morrow, R. see Cook, N., Barrow, D.R., and Howe, A.F. see Murphy, A.B. Barrow, D.R. K Corlett, B.J., Lucas, J., and Smith, J.S. Sensors for narrow-gap welding p213 R Kawamoto, A., and Ikejiri, T. see Ikejiri, T. Kibble, B.P. Present state of the electrical units (Commissioned IEE review) p187 Reed, ILS. Wave packet with special relativity D Knighi, R.B.D., Legg, D.J., and Martin, P. Digital demonstrating quantum rules, Schrédinger’s ‘bridge’ for comparison of AC-DC transfer equation and propagator integral p223 instruments p1l69 Rickard, D.A., Dupuy, J., and Waters, R.T. Verifica- Davwiist,h aL .Es.u,p earncdo ndSumictthi,n g P.iAn.n erQ coofn dau cctooarx ial p3c1a3v ity Knicguhrtr,en t R.cBo.mD.p,a raLteogrg,s Di.nJ .t,h e ancadl ibMraarttiionn, ofP. ACUs-eD Co f tuiseo n aso fa atnr anaslmtiesrsnaitoinn g linceu rdreesnitg n coairdo na p2m5o0d el for Domaradzki, P., Henderson, I.A.. McGhee, J., and transfer standards pl01 Rizkalla, M.E. Gundrum, H., and Michel, H. Szaniawski, W. see Henderson, I.A. Konar, A., and Mandal, A.K. Microprocessor based Design of a fractional phase locked-loop fre- Dupuy, J., Rickard, D.A. and Waters, R.T. see automatic sun tracker p237 quency synthesiser using a Motorola based Rickard, D.A. Kriezis, E.E., Aptonopoulos, C.S., and Panas, S$.M. microcontroller p295 see Antonopoulos, C.S. Robinson, G. Discharges in asymmetric cavities under AC stresses pl19 E L S Elayyan, H.S.B., Haddad, A., and German, D.M. Legg, D.J., Knight, R.B.D., and Martin, P. see see Haddad, A. Knight, R.B.D. Saito, S., and Ohki, M. see Ohki, M. Legg, DJ., Knight, R.B.D., and Martin, P. see Sheshadri, T.S. MHD arcjet onset studies p286 Knight, R.B.D. Shiloh, K., Som, A.K., and Bond, L.J. Character- F Lightfoot, H.A., Boutlendj, M., Allen, N.L., and isation of high frequency focused ultrasonic trans- Neville, R.B. see Boutlendj, M. ducers using modulation transfer function: Liu, Z.J., Vourdas, A., and Binns, K.J. Magnetic Concept and experimental approach p205 Fang, M.T.C., Taylor, S., Jones, G.R., and Shimmin, field and eddy current losses in linear and rotat- Shimmin, D.S., Taylor, S., Fang, M.T.C., and Jones, DS. see Taylor, S. ing permanent magnet machines with a large G.R. see Taylor, S. Fang, M.T.C., and Bu, W.H. Investigation of number of poles p289 Smith, J.S., Corlett, B.J., and Lucas, J. see Corlett. ablation-dominated AC nozzle arcs_ p71 Lucas, J., Corlett, B.J.. and Smith, J.S. see Corlett, BJ. Farish, O., and Al-Bawy, I. see Al-Bawy, I. BJ. Smith, P.A., and Davis, L.E. see Davis, L.E. IEE PROCEEDINGS-A, Vol. 138, 1991 337 Sobocki, R. Function representation of lightning Towill, D.R. Address as Chairman of the IEE Man- W impulses produced by a testing circuit with con- agement & Design Division: Engineering change; tinuity of voltages and currents at a tested object or is it change engineering? A personal per- p78 spective pll Waiatn,i soJ.tRr.o pEilc ecctyrlionmdaegrn etipcl surface impedance of an SSzoamn,i aAw.sKk.i,, ShWi.l,o h,H eKn.d,e rasnod n,B onId.,A. . L.MJ.c Gsheee eS,h iloJh.,, aKn.d WatReircsk,a rd,R. TD.., A. Rickard, D.A., and Dupuy, J. see Domaradzki, P. see Henderson, I.A. Waters, R.T., and Harid, N. see Harid, N. Webb, P.W., and Hann, R.A. Measurement of T V thermal transients in a thermal print head used for dye diffusion colour printing p98 Wilson, A. Slot discharge damage in air cooled Taylor, S., Fang, M.T.C., Jones, G.R., and Shimmin, Varlow, B.R., and Auckland, D.W. see Auckland, stator windings p153 D.S. Current zero flow conditions in a circuit D.W. Woods, R.C. Design of surface-acoustic wave breaker-nozzle p259 Vourdas, A., Liu, Z.J., and Binns, K.J. see Liu, Z.J. devices p181 Addresses IEE commissioned reviews Jones, D.A. President’s Inaugural address: Electri- Kibble, B.P. Present state of the electrical units cal engineering; the backbone of society pl p187 Overshott, K.J. Address as Chairman of the IEE Science Education & Technology Division: Mag- netism; itis permanent p22 Towill, D.R. Address as Chairman of the IEE Man- agement & Design Division: Engineering change; or is it change engineering? A personal per- spective pll IEE PROCEEDINGS.-A, Vol. 138, 1991 Subject index ACOUSTOELECTRIC EFFECTS ELECTROMAGNETIC THEORY Characterisation of high frequency focused ultrasonic transducers using modu- Electromagnetic energy changes due to charges moving through constant, or lation transfer function: Concept and experimental approach. K. Shiloh, A.K. zero, magnetic field. C.J. Carpenter p55 Som and L.J. Bond p205 Electromagnetic surface impedance of an anisotropic cylinder. J.R. Wait ps4 High frequency surface currents induced on a soft-bard cylindrical strip. C. ARCING Géksu and F. Giines pi13 NEMP.-interaction with plane multilayer structures. W. Blumer and N. Ari Current zero flow conditions in a circuit breaker-nozzle. S. Taylor, M.T.C. pl99 Fang, G.R. Jones and D.S. Shimmin p259 Response of horizontal axis eddy current coils to layered media: a theoretical Discharges in asymmetric cavities under AC stresses.G. Robinson p119 and experimental study. R. Clark and L.J. Bond p248 Effect of a magnetic field on low-pressure gaseous breakdown along the surface Transient electromagnetic shielding in 2 system of two coaxial cylindrical shells. of a solid insulator. M. Ohki and S. Saito p300 C.S. Antonopoulos, $.M. Panas and E.E. Kriezis p281 Erosive failure caused by surface discharge on the surface of epoxy resin immersed in insulating oil. T. Ikejiriand A. Kawamoto p288 ENERGY CONVERSION AND STORAGE Investigation of ablation-dominated AC nozzle arcs. M.T.C. Fang and W.H. Bu p7l MHD arcjet onset studies. T.S. Sheshadri p286 MHD arcjet onset studies. T.S. Sheshadri p286 The chemistry of electric fuse arcing. D.R. Barrow, A.F. Howe and N. Cook ENGINEERING AND SOCIETY 3 Verification of an alternating current corona model for use as a transmission Electrical engineering; the backbone of society. D.A. Jones pl line design aid. D.A. Rickard, J. Dupuy and R.T. Waters p250 FERRITES AND FERROMAGNETICS BREAKDOWN AND GAS DISCHARGES Time domain model for the ferromagnetic core, including the effects of hyster- Effect of a magnetic field on low-pressure gaseous breakdown along the surface esis and eddy currents. S.R. Naidu of a solid insulator. M. Ohki and S. Saito p300 Positive DC corona and sparkover in short and long rod-plane gaps under GENERATORS variable humidity conditions. M. Boutlendj, N.L. Allen, H.A. Lightfoot and R.B. Neville p31 Slot discharge damage in air cooled stator windings. A. Wilson p153 Study of the electric fields required for streamer propagation in humid air. N.L. Allen and M. Boutlendj p37 HISTORY Synthetic theory of Poole and Poole—Frenkel (PF) effects. R. Ongaro and A. Pillonnet p127 Electrical engineering; the backbone of society. D.A. Jones pl CIRCUIT BREAKERS AND CIRCUIT BREAKING HYSTERESIS Current zero flow conditions in a circuit breaker-nozzle. S. Taylor, M.T.C. Time domain model for the ferromagnetic core, including the effects of hyster- Fang, G.R. Jones and D.S. Shimmin p259 esis and eddy currents. S.R. Naidu COAXIAL COMPONENTS INSTRUMENTATION AND MEASURING SCIENCE Transient electromagnetic shielding in a system of two coaxial cylindrical shells. Digital ‘bridge’ for comparison of AC-DC transfer instruments. R.B.D. Knight, C.S. Antonopoulos, S.M. Panas and E.E. Kriezis p281 DJ. Legg and P. Martin pl69 Incorporating high reliability into the —_— of microprocessor-based instru- — LA. Henderson, J. McGhee,W . Szaniawski and P. Domaradzki CONDUCTORS AND CONDUCTIVITY P Q of a coaxial cavity with a superconducting inner conductor. L.E. Davis and Measurement of the load admittance and reactive current RMS value in the P.A. Smith p313 i domain. J.C. Montafio, M.C. Ibaiiez, A.L. Ojeda and J.G. Benitez Pp Measurement of thermal transients in a thermal en head used for dye diffu- CONTROL SYSTEMS sion colour printing. P.W. Webb and R.A. Hann Microprocessor based automatic sun tracker. A. Konar and A.K. Mandal Present state of the electrical units. B.P. Kibble 18) p237 Response of horizontal axis eddy current coils to layered media: a theoretical Sensors for narrow-gap welding. B.J. Corlett, J. Lucas and J.S. Smith p213 and experimental study. R. Clark and L.J. Bond p248 Use of current comparators in the calibration of AC—DC transfer standards. R.B.D. Knight, D.J. Legg and P. Martin pl01 CONVERTORS Digital ‘bridge’ for comparison of AC-DC transfer instruments. R.B.D. Knight, INSULATORS AND INSULATION UseD J.o f Lceugrgr enatn dcPo m.p Maarrattionr s p1in6 9t he calibration of AC-DC transfer standards. ChaArlg-eB awdeyp oasnidt ioOn. Foanr iasnh inps1ul4a5t ing spacer under impulse-voltage conditions. I. R.B.D. Knight, D.J. Legg and P. Martin p101 a in asymmetric cavities under AC stresses.G. Robinson p119 Effect of a magnetic field on low-pressure gaseous breakdown along the surface DESIGN of a solid insulator. M. Ohki and S. Saito p300 Erosive failure caused by surface discharge on the surface of epoxy resin Design of surface-acoustic wave devices. R.C. Woods p181 immersed in insulating oil. T. Ikejiriand A. Kawamoto p288 — flashover in SF, under impulse voltage conditions. I. Al-Bawy and O. DIELECTRIC MATERIALS Farish p89 Slot discharge damage in air cooled stator windings. A. Wilson 153 Dependence of electrical tree inception and growth on mechanical properties. D.W. Auckland and B.R. Varlow p51 LIGHTNING AND LIGHTNING PROTECTION Effect of a magnetic field on low-pressure gaseous breakdown along the surface of a solid insulator. M. Ohki and S. Saito p300 Function representation of lightning impulses produced by a testing circuit with continuity of voltages and currents at a tested object. R. Sobocki p78 DIGITAL CIRCUITS MAGNETIC DEVICES AND PROPERTIES Digital ‘bridge’ for comparison of AC-DC transfer instruments. R.B.D. Knight, D.J. Legg and P. Martin p169 Forces on semi-infinite overlapping rectangular poles: infinity permeable against saturable case. W.O’Connor pl76 DIGITAL COMMUNICATION SYSTEMS Magnetic field and eddy current losses in linear and rotating permanent magnet machines with a larg: number of poles. Z.J. Liu, A. Vourdas and K.J. Binns Design of a fractional phase locked-loop frequency synthesiser using a Motor- p289 ola based microcontroller. M.E. Rizkalla, H.Gundrum and H. Michel p295 Magnetism; it is permanent. K.J. Overshott p22 DIGITAL COMPUTERS AND COMPUTATION MAGNETIC FIELDS Discrete transform technique for soiving coupled integro-differential equations Electromagnetic energy changes due to charges moving through constant, or in digital computers. S.Y.R. Hui and C. Christopoulos p273 zero, magnetic field. C.J. Carpenter p55 DIGITAL-ANALOGUE CONVERSION MANAGEMENT Design of a fractional phase locked-loop frequency synthesiser — Motor- Enguicering oon or is it change engineering? A personal perspective. D.R. ola based microcontroller. M.E. Rizkalla, H.Gundrum and H. Michel p295 Towill pil EDDY CURRENTS MATHEMATICAL TECHNIQUES Magnetic field and eddy current losses in linear anc -otating permanent magnet Discrete transform technique for solving coupled integro-differential equations machines with a large number of poles. Z.J. Liu, A. Vourdas and K.J. Buins in digital ——— S.Y.R. Hui and C. Christopoulos p273 p289 Measurement of the load admittance and reactive current RMS value in the Response of horizontal axis eddy current coils to layered media: a theoretical frequency domain. J.C. Montaiio, M.C. Ibafiez, A.L. Ojeda and J.G. Benitez and experimental study. R. Clark and LJ. Bond p248 p138 Time domain model for the ferromagnetic core, including the effects of hyster- Time domain model for the ferromagnetic core, including the effects of hyster- esis and eddy currents. S.R. Naidu p44 esis and eddy currents. S.R. Naidu Transient electromagnetic shielding in a system of two coaxial cylindrical shells. Wave packet with special relativity demonstrating quantum rules, Schrodinger’s C.S. Antonopoulos, S.M. Panas and E.E. Kriezis p281 equation and propagator integral. 1S. Reed p223 IEE PROCEEDINGS-A, Vol. 138, 1991 339 MICROPROCESSORS SIMULATION Incorporating high reliability into the design of microprocessor-based instru- Forces on semi-infinite overlapping rectangular poles: infinity permeable mentation. I.A. Henderson, J. McGhee, W. Szaniawski and P. Domaradzki against saturable case. W.O’Connor p176 p10s Statistical study of impulse corona inception parameters on line conductors. N. Microprocessor based automatic sun tracker. A. Konar and A.K. Mandal Harid and R.T. Waters p1l61 p237 Study of a five-electrode quadrupole levitation system. Part I: Theoretical aspects. D. Hu and B. Makin p320 MOTORS Study of a five-electrode quadrupole levitation system. Part II: Experimental results. D. Hu and B. Makin p329 Slot discharge damage in air cooled stator windings. A. Wilson p153 Verification of an alternating current corona model for use as a transmission line design aid. D.A. Rickard, J. Dupuy and R.T. Waters p250 NONDESTRUCTIVE TESTING SOLAR POWER Electromagnetic surface impedance of an anisotropic cylinder. J.R. Wait p184 Microprocessor based automatic sun tracker. A. Konar and A.K. Mandal p237 PHASING AND PHASE CONTROL SONICS AND ULTRASONICS Design of a fractional phase locked-loop frequency synthesiser using a Motor- ola based microcontroller. M.E. Rizkalla, H.Gundrum and H. Michel p295 Characterisation of high frequency focused ultrasonic transducers using modu- lation transfer function: Concept and experimental approach. K. Shiloh, A.K. Som and L.J. Bond p205 POWER SYSTEM PROTECTION ZnO surge arrester elements with mixed direct and 50 Hz voltages. A. Haddad, STANDARDISATION AND STANDARDS H.S.B. Elayyan and D.M. German p265 Present state of the electrical units. B.P. Kibble p187 POWER UTILISATION AND INDUSTRIAL APPLICATIONS SURFACE-ACOUSTIC-WAVE DEVICES (SAW) Thermal treatment of sewage sludge by ohmic heating. A.B. Murphy, K.J. Design of surface-acoustic wave devices. R.C. Woods p181 Powell and R. Morrow p242 SYNCHRONOUS MOTORS QUANTUM ELECTRONICS Magnetic field and eddy current losses in linear and rotating permanent magnet Wave packet with special relativity demonstrating quantum rules, Schrédinger’s machines with a large number of poles. Z.J. Liu, A. Vourdas and K.J. Binns equation and propagator integral. LS. Reed p223 p289 SYSTEM PROTECTION RELIABILITY Statistical study of impulse corona inception parameters on line conductors. N. Incorporating high reliability into the design of microprocessor-based instru- Harid and R.T. Waters pl61 mentation. I.A. Henderson, J. McGhee, W. Szaniawski and P. Domaradzki pl0s TRANSDUCERS REVIEWS OF PROGRESS Characterisation of high frequency focused ultrasonic transducers using modu- lation transfer function: Concept and experimental approach. K. Shiloh, A.K. Present state of the electrical units. B.P. Kibble p187 Som and L.J. Bond p205 SERVOMOTORS TRANSMISSION LINES Microprocessor based automatic sun tracker. A. Konar and A.K. Mandal Statistical study of impulse corona inception parameters on line conductors. N. p237 Harid and R.T. Waters pl61 IEE PROCEEDINGS.-A, Vol. 138, 1991