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CPTM Field/Case Studies

The Centre staff members were involved in a number of case studies on monitoring and diagnostics of operating transformers, factory vacuum dryouts and temperature rise tests, transformer failure investigations and tear-down inspections of failed and retired transformers. A brief list of such case studies is given below:

• 1999 – Australia, 20 MVA 66/22 kV new transformer: moisture assessment using moisture transmitter during factory temperature rise test;
• 1999-2000 – South Africa, Boiler Feedpump Supply 8 MVA 11 kV 1990 vintage transformer: moisture assessment using moisture transmitter;
• 1999-2000 – South Africa, Transmission 180 MVA 275 kV vintage 1969 transformer: moisture assessment using moisture transmitter;
• 2000-2001 – South Africa, GSU transformer: moisture assessment using moisture transmitter;
• 2000 – Australia, failure investigation, 250 MVA 220 kV GSU transformer: reason for failure – wet insulation;
• 2001-2003 – USA, 4 MVA 26 kV distribution 1928 vintage transformer: moisture assessment using two moisture transmitters;
• 2001-2003 – USA, 180 MVA 230 kV transmission 1998 vintage transformer: moisture assessment using moisture transmitter;
• 2001-2003 – USA, 45 MVA 138 kV nitrogen blanketed shell-type 1994 vintage transformer: moisture assessment using moisture transmitter;
• 2001-2003 – USA, 550 MVA 230 kV 1982 vintage autotransformer: moisture assessment using moisture transmitter;
• 2002-2003 – Europe, 22.5 MVA 93 kV 1982 vintage GSU transformer: assessment of effectiveness of on-line dryout;
• 2002-2003 – Australia, 15 MVA 33 kV new distribution transformer: study into dryout of thick and thin transformer insulation using the conventional factory heat-and-vacuum dryout process; study of effects of change in moisture, temperature and clamping pressure of the layer-type transformer windings on FRA signatures;
• 2003-2004 – Australia, 150 MVA 220 kV new transmission transformer: study into dryout of thick and thin transformer insulation using the modern factory vapour-phase dryout process; study of effects of change in moisture, temperature and clamping pressure of the transformer disk-type windings on FRA signatures;
• 2003 – USA, 4 MVA 1928 vintage distribution transformer: assessment of effectiveness of on-line dryout; teardown inspection; paper samples collected and tested using Karl Fisher method; good correlation between direct (Karl Fischer) and indirect (moisture transmitter and Monash Water-in-Paper algorithm) measurements;
• 2003-2004 – Australia, 31 MVA 220 kV 1957 vintage GSU transformer: assessment of effectiveness of on-line dryout;
• 2004 – USA, 225 MVA 230 kV transmission transformer: assessment of effectiveness of on-line dryout;
• 2006 – Australia, failure investigation, 20 MVA 66 kV substation transformer: reason for failure – wet insulation;
• 2005-2007 – Australia, on-line monitoring of three power transformers operating at the CPTM Sponsoring utilities.