ISO INTERNATIONAL STANDARD 18095 First edition 2018-02 Condition monitoring and diagnostics of power transformers Surveillance et diagnostic de I'état des transformateurs de puissance Reference number IS0 18095:2018(E) so @IS02018 IS0 18095:2018(E) COPYRIGHTPROTECTEDDOCUMENT @ IS0 2018 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below or Iso's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +4122 749 0111 Fax: +41 22 749 09 47 Email: [email protected] Website: www.iso.org Published in Switzerland ii @ IS0 2018 - All rights reserved IS0 18095:2018(E) Contents Page Foreword ..vi Introduction. ..vii 1 Scope 2 Normative references 3 Terms and definitions 4 Abbreviated terms ..1 5 Approach to selecting appropriate condition monitoring techniques. .2 5.1 Implementing condition monitoring of transformers 5.2 Components, failure modes and detection techniques ..2 6 Power transformer types. .3 6.1 Oil-filled transformers .3 6.2 Dry-type transformers. 6.3 Gas-insulated transformers (GITs) .6 7 Power transformer failure mode analysis 6 7.1 Components. ..6 7.2 Categories of failure mode 7 7.2.1 General. 7.2.2 Dielectric failures 7 7.2.3 Thermal .7 7.2.4 Mechanical 7 7.2.5 External .8 7.3 Failure modes. .8 7.4 Influences on rate of failure mode progression 9 7.4.1 General. .9 7.4.2 Loading. .9 7.4.3 Environment 7.4.4 Design. .10 7.4.5 Maintenance .10 7.4.6 Protection. ..10 8 Range of techniques. ..10 9 Overview of techniques for condition monitoring power transformers .12 9.1 Mains current/voltage/load. .12 9.1.1 Fault mechanism ..12 9.1.2 Technique. .12 9.1.3 Faults detected/components covered ..12 9.2 Visual .12 9.2.1 Fault mechanism. .12 9.2.2 Technique. .13 9.2.3 Faults detected/components covered ..13 9.3 Oil condition .13 9.3.1 Fault mechanism .13 9.3.2 Technique. .15 9.3.3 Faults detected/components covered .15 9.4 Temperature including thermography ..17 9.4.1 Fault mechanism ..17 9.4.2 Technique.. ..17 9.4.3 Faults detected/components covered .17 9.5 Partial discharge (PD) .17 9.5.1 Fault mechanism ..17 9.5.2 Techniques.. ..18 9.5.3 Faults detected/components covered. ..19 @ IS0 2018 - All rights reserved iii