4.5 Note
1 The author thanks the International Electrotechnical Commission (IEC) for permission
to reproduce: the table ‘Fault Gas Ratios Interpretation’ and the illustration of
‘Duval’s Triangle’ from its International Standard IEC 60599 2nd edition 1999–03
Mineral oil-impregnated electrical equipment in service – Guide to the interpretation
of dissolved and free gases analysis. All such extracts are copyright of IEC, Geneva,
Switzerland. All rights reserved. Further information on the IEC is available from
www.iec.ch. IEC has no responsibility for the placement and context in which the
extracts and contents are reproduced by the author; nor is IEC in any way responsible
for the other content or accuracy therein.