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TRANSFORMER OIL TESTING FOR CORROSIVE SULFUR BY SHIVAKUMAR shivakumar
Visvesvaraya Technological University Jnana Sangam Belgaum-590014 Department of Electronics and Electronic’s EngineeringGHOUSIA COLLEGE OF ENGINERRING A seminar on “Testing for Corrosive Sulfur Effect in transformer oil ” Submitted in partial fulfillment of the requirement for the award of the degree Bachelor of Engineering in Electrical & Electronic’s Engineering presented by SHIVAKUMAR.S (USN: 1GC08EE049) Under the guidance of Mr. Faheem Ahmed Khan Asst. Prof, Dept. of E&E, GCE, Ramanagara Department of Electronics and Electronic’s Engineering Ghousia College of Engineering Ramanagara –562159 2011-2012
have been a number of failures of Department of Electronics and Electronic’s Engineering power transformers and reactors, due to formation of copper sulfides onGHOUSIA COLLEGE OF ENGINERRING conductors and insulating materials. The conductive copper sulfide reduces the dielectric breakdown voltage of the solid insulation. This can result in a dielectric puncture through the paper insulation.
Department of Electronics and Electronic’s Engineering •At normal operating temperatures the corrosion process will take time toGHOUSIA COLLEGE OF ENGINERRING form conductive sulfides. •This problem in the transformer is difficult to detect and manage, because the failures have occurred without prior evidence of abnormal gassing behavior. •This problem is mainly present in the large power utilities.
susceptible?” Department of Electronics and Electronic’s Engineering •In response to the above question, Doble has developed the following list.GHOUSIA COLLEGE OF ENGINERRING (1) Units that have the following characteristics a)Manufactured from 1999 to present. b) Operate at high temperatures over long periods of time. c)Are either gas blanketed or have a sealed conservator system. d)Have oils that fail the corrosive sulfur . 2) Those unit that do not have
3)In the fast several years, in response to this problem, Department of Electronics and Electronic’s Engineering there has been a great deal of research activity in developing new test to help identify oils with the potential to have corrosive sulfur problemsGHOUSIA COLLEGE OF ENGINERRING . some of the tests are in various stages of development and are broken down into two groups. 1. Oil tests. 2. Transformer Electrical test.
Department of Electronics and Electronic’s Engineering These test is to determining if corrosive sulfur compounds are present in the oil or not.GHOUSIA COLLEGE OF ENGINERRING Identifying sulfur compound that are presently stable but may become corrosive under conditions that exist in the transformer. A listing of some of the oil tests used with descriptions follows.
Department of Electronics and Electronic’s Engineering This test ages 220mls of oil in contact with a copper strip in aGHOUSIA COLLEGE OF ENGINERRING sealed vessel for 48 hours at 150 deg C as shown. The primary purpose of the test is to determine if any corrosive sulfur compounds present in the oil.
If the corrosive sulfur compounds present in the oil, then the oil will Department of Electronics and Electronic’s Engineering react with the copper strip to turn it gray or black as shown below.GHOUSIA COLLEGE OF ENGINERRING Noncorrosive Strip Corrosive Strip In the above figure the lift side is the strip before immersed in the sealed vessel & right side is the strip after removal from the sealed vessel after 48 hours at 150 deg C. This is a very routine test.
2)Sulfur speciation: Department of Electronics and Electronic’s EngineeringGHOUSIA COLLEGE OF ENGINERRING This test is performed by gas chromatography with sulfur selective detection and covers the detection of volatile sulfur-containing compounds. This test can be used to isolate specific sulfur compounds, some of which may or may not be responsible for corrosive sulfur attack. There are thousands of sulfur compounds, and this test does not have the ability to cover them all. It is usually not considered a routine test and mostly used for research purposes.
3)Total sulfur in oil: Department of Electronics and Electronic’s Engineering There are several tests that can be used for theGHOUSIA COLLEGE OF ENGINERRING detection of total sulfur in oil. This test determines the total amount of sulfur in the oil. But in this method it does not determine whether or not the compounds being detected are corrosive. This is a routine test, but it only provides information on how much sulfur in the oil.
4)Mercaptans in oil: Department of Electronics and Electronic’s Engineering Mercaptans are sulfur compounds that can be very corrosive.GHOUSIA COLLEGE OF ENGINERRING This is a potentiometric titration test that is used to determine the concentration of mercaptans compounds. From this test it is not able to identify specific compounds. This test is used in the fuel and lubrication industries often and is starting to be used in the transformer oil industry. The problem with mercaptans is that some of them are highly volatile and thus not easily sampled. It is presently not routine test. .
5)Doble Covered Conductor Deposition (CCD) Test, Doble Test Department of Electronics and Electronic’s Engineering This test is conducted by taking an abraded copper road and wrapping new Kraft paper insulation around the rod as shown in the figure below.GHOUSIA COLLEGE OF ENGINERRING Then they are placed in 20 mL headspace vials. Oil is added and then the vials are sealed as shown below.
CONT…… Department of Electronics and Electronic’s Engineering • A stainless steel needle of a particular diameter is then pierced through the spectrum of one vial and left there to allow air ingress during testing as shownGHOUSIA COLLEGE OF ENGINERRING in figure. • The vials are then tested at 140 deg C for four days. • At the end of the test cycle , the vials are removed and the copper rods with paper retrieved.
Cont….. Department of Electronics and Electronic’s Engineering The paper is then removed from the copper as shown in the figure below.GHOUSIA COLLEGE OF ENGINERRING • Then washed in a solvent to remove the oil. • The road is inspected to determine if it has been tarnished by corrosive sulfur, and the paper is inspected to determine if deposition as occurred. • The presence of deposition in the paper is important as most of the recent transformer failures have been due to copper sulfide deposits in the paper causing a severe reduction in dielectric strength. • The resulting “deposition,” whether heavy, moderate, or light, means that the interaction of the copper and oil with the paper insulation. • This is becoming a very routine test.
Conclusion epartment of Electronics and Electronic’s Engineering These test will be used to screen out or identify oils that may not be suitable.GHOUSIA COLLEGE OF ENGINERRING D
GHOUSIA COLLEGE OF ENGINERRINGDepartment of Electronics and Electronic’s Engineering THANK YOU
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This is seminar presentation gives about testing of transformer oil for copper sulfide