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JWG A2/B4-28 HVDC Converter Transformers. Progress Report Convener: Milan Saravolac IEC SYMPOSIUM DELHI, January 2009. Contents. Meetings JWG Members – current status JWG Report Summary. Meetings. Paris, 30 th August 2004, Inaugural Arnhem (KEMA), 27 th January 2005
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JWG A2/B4-28HVDC Converter Transformers Progress Report Convener: Milan Saravolac IEC SYMPOSIUM DELHI, January 2009
Contents • Meetings • JWG Members – current status • JWG Report Summary JWG A2/B4-28 Progress Report, January 2009
Meetings • Paris, 30th August 2004, Inaugural • Arnhem (KEMA), 27th January 2005 • Bangalore, 21st September 2005 (SC B4 Colloquium) • Rapperswil (Weidmann), 27th January 2006 • Paris, 28th August 2006 • Sao Paulo, 15th & 16th February 2007 • Osaka, 29th & 30th October 2007 • Ludvika, 11th and 12th March 2008 • Nuremberg, 10th and 11th June 2008 • Paris, 25th August 2008 • Delhi, 27th January 2009 JWG A2/B4-28 Progress Report, January 2009
JWG Members – January 2009 JWG A2/B4-28 Progress Report, January 2009
JWG Progress Summary • Reliability Questionnaire – Update for 2005 & 2006 2005 – 2006 vs 2003-2004 The total failure rate decreasing… JWG A2/B4-28 Progress Report, January 2009
JWG Progress Summary • Reliability Questionnaire – Update for 2005 & 2006 2001 – 2006 Decrease in actual failures and increase in prevented failures JWG A2/B4-28 Progress Report, January 2009
JWG Progress Summary JWG A2/B4-28 Progress Report, January 2009
Progress Summary • Design Review Guide HVDC Converter Transformers • The new guide is based on and derived from the existing document, “Guidelines for Conducting Design Reviews for Transformers 100 MVA and 123 kV and above” created by the CIGRE WG 12.22 and published in 2002 as CIGRE Brochure No. 204 JWG A2/B4-28 Progress Report, January 2009
JWG Progress Summary • POLARITY REVERSAL TEST • The dielectric stress depends on the polarization time and oil resistivity. • Oil conductivity of the new oil and the aged oil differs considerably. • Conductivity of oil impregnated high density pressboard remains almost • Transient dielectric field simulations were performed with different values of oil conductivity in order to relate stress profiles during service with design values and stresses experienced during tests. JWG A2/B4-28 Progress Report, January 2009
JWG Progress Summary EFFECT OF POLARIZATION DURATION AND DIFFERENT OILS JWG A2/B4-28 Progress Report, January 2009
JWG Progress Summary • Five different combinations of test voltage and time duration were simulated • PR test with 20% higher than test level Upr = 1.5((N-0.5)Udm +0.35Uvm)) and 45 min longer duration (90-120-90 min) was most suitable. JWG A2/B4-28 Progress Report, January 2009
JWG Progress Summary • Effect of Oil Conductivity • Oil conductivity is not measured on a regular basis • There is no consistent test method for measuring • The test method measures conductivity at dielectric stress below 0.5 kV/mm • In PR test oil can be subjected to 5-10 kV/mm • In service oil is different form the one used in testing • No information about real effectiveness of the PR test. JWG A2/B4-28 Progress Report, January 2009
JWG Progress Summary • Tutorial • The Tutorial on Reliability of HVDC Converter Transformers is complete as well and was initially presented at the CIGRE Brazil event (Workspot) in Belem in April 2008. The intention is to present this tutorial during the next A2 Colloquium in South Africa in August 2009 • Tutorial for B4 shall be scheduled . JWG A2/B4-28 Progress Report, January 2009
Action Plan • By the 2009 B4 Symposium, to issue the Design Review Guide. • By Aug 2009 to issue a Final Report. JWG A2/B4-28 Progress Report, January 2009
JWG A2/B4-28HVDC Converter Transformers Thank you for your attention