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Evaluation of laboratory tests as indicators of service life of TRANSFORMER OILS

Evaluation of laboratory tests as indicators of service life of TRANSFORMER OILS evaluation of laboratory tests as indicators (4) The change in the neutralization value of an o f service life of oil and the change in the pressure sludge value are suggested as tests which show promise in the evalu­ ation of the continued useability of an oil in trans­ former service. Each of these tests, however, and TRANSFORME R OILS especially the change in neutralization number can be safely applied only with proper consideration of the operating conditions imposed by the design of RESULTS of some very long term investigations the transformer in which the oil is being used. into the service testing of transformer oils have recently been published by the A.S.T.M. in two papers as follows : "Evaluation of Mineral Transformer Oil McConnell's Conclusions. During Service, Par t II.—Correlation of Oil Character­ The paper by McConnell deals with eleven of the istics with Continued Transformer Operation," by transformers provided by the Detroit Edison Com­ Frank M. Clark (Division Engineer, General Engin­ pany, and in this paper, the author has these remarks eering Laboratory, General Electric Co., Schenectady), to make. Through the entire course of the testing "A study of Changes in Oil Characteristics during programme one great disadvantage appears evident 4½—6 Year s of Service," by T. A. McConnell (Research when considering the value of sludge accumulation Engineer, The Detroit Edison Company, Detroit). test as an indicator of the quality of an oil after any I t is not possible here to give more than the briefest period of service. If it can be assumed that the trend conclusions reached as a result of several years of the test values, rather than their magnitude at any service tests on a wide variety of transformers, but period, is the real criterion of sludge deposition, then the complete papers are obtainable from the A.S.T.M., it would be necessary to sample and test an oil in 1916 Race St., Philadelphia, Pa. service continuously, in order to obtain any real benefit from the test. A relatively high value might Object of Tests. indicate that an oil in service had a great tendency to sludge, but whether sludge had been deposited The operator of a transformer desires a testing would not be known unless previous history of sludge procedure which will indicate the degree of deterior­ accumulation values were known. The amount of ation and sludging propensity of the oil at selected testing involved, therefore, would exclude sludge periods, in order to avoid the dielectric and thermal accumulation as a routine test for oil-service quality. problems associated with sludge deposition. The samples were tested in accordance with the following Pressure oxidation appears to offer somewhat more A.S.T.M. testing procedures : Colour (D155), Steam merit as a routine oil test than the sludge accumu­ Emulsion (D157), Neutralization Value (DCG3), lation test because the test values tend to indicate Sludge Value by Pressure Oxidation and by Accumu­ gradual oil deterioration, but pressure oxidation test lation (DC70)," and Interfacial Tension (D.971). is less reliable than either the neutralization number Eighteen transformers were assigned to the 10-year or interfacial tension tests. Relative simplicity, field investigations. especially of the neutralization number further qualifies it and the interfacial tension test as being the more suitable for routine tests. General Conclusions. The general conclusions to Clark's papers were as follows : (1) A variety of tests are necessary for the quality grading of new oils. Among these tests are those for sludge accumulation and the pressure oxidation test. (2) Of the new oil (quality) tests, those for neutral­ ization number and pressure oxidation appear to be best suited as a gauge for the continued useability of an oil during transformer operation. Other tests, such as steam emulsion and interfacial tension appear to be of diminishing value as the use of the oil is continued in the transformer because of the de­ creasing rate of change in these properties with continued oil oxidation. (3) The sludge accumulation test as at present constituted is not suited for use as a gauge of the condition of a used transformer oil because of the erratic nature of the test results. 30 Scientific LUBRICATION February, 1952 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Industrial Lubrication and Tribology Emerald Publishing

Evaluation of laboratory tests as indicators of service life of TRANSFORMER OILS

Industrial Lubrication and Tribology , Volume 4 (2): 1 – Feb 1, 1952
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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0036-8792
DOI
10.1108/eb052155
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Abstract

evaluation of laboratory tests as indicators (4) The change in the neutralization value of an o f service life of oil and the change in the pressure sludge value are suggested as tests which show promise in the evalu­ ation of the continued useability of an oil in trans­ former service. Each of these tests, however, and TRANSFORME R OILS especially the change in neutralization number can be safely applied only with proper consideration of the operating conditions imposed by the design of RESULTS of some very long term investigations the transformer in which the oil is being used. into the service testing of transformer oils have recently been published by the A.S.T.M. in two papers as follows : "Evaluation of Mineral Transformer Oil McConnell's Conclusions. During Service, Par t II.—Correlation of Oil Character­ The paper by McConnell deals with eleven of the istics with Continued Transformer Operation," by transformers provided by the Detroit Edison Com­ Frank M. Clark (Division Engineer, General Engin­ pany, and in this paper, the author has these remarks eering Laboratory, General Electric Co., Schenectady), to make. Through the entire course of the testing "A study of Changes in Oil Characteristics during programme one great disadvantage appears evident 4½—6 Year s of Service," by T. A. McConnell (Research when considering the value of sludge accumulation Engineer, The Detroit Edison Company, Detroit). test as an indicator of the quality of an oil after any I t is not possible here to give more than the briefest period of service. If it can be assumed that the trend conclusions reached as a result of several years of the test values, rather than their magnitude at any service tests on a wide variety of transformers, but period, is the real criterion of sludge deposition, then the complete papers are obtainable from the A.S.T.M., it would be necessary to sample and test an oil in 1916 Race St., Philadelphia, Pa. service continuously, in order to obtain any real benefit from the test. A relatively high value might Object of Tests. indicate that an oil in service had a great tendency to sludge, but whether sludge had been deposited The operator of a transformer desires a testing would not be known unless previous history of sludge procedure which will indicate the degree of deterior­ accumulation values were known. The amount of ation and sludging propensity of the oil at selected testing involved, therefore, would exclude sludge periods, in order to avoid the dielectric and thermal accumulation as a routine test for oil-service quality. problems associated with sludge deposition. The samples were tested in accordance with the following Pressure oxidation appears to offer somewhat more A.S.T.M. testing procedures : Colour (D155), Steam merit as a routine oil test than the sludge accumu­ Emulsion (D157), Neutralization Value (DCG3), lation test because the test values tend to indicate Sludge Value by Pressure Oxidation and by Accumu­ gradual oil deterioration, but pressure oxidation test lation (DC70)," and Interfacial Tension (D.971). is less reliable than either the neutralization number Eighteen transformers were assigned to the 10-year or interfacial tension tests. Relative simplicity, field investigations. especially of the neutralization number further qualifies it and the interfacial tension test as being the more suitable for routine tests. General Conclusions. The general conclusions to Clark's papers were as follows : (1) A variety of tests are necessary for the quality grading of new oils. Among these tests are those for sludge accumulation and the pressure oxidation test. (2) Of the new oil (quality) tests, those for neutral­ ization number and pressure oxidation appear to be best suited as a gauge for the continued useability of an oil during transformer operation. Other tests, such as steam emulsion and interfacial tension appear to be of diminishing value as the use of the oil is continued in the transformer because of the de­ creasing rate of change in these properties with continued oil oxidation. (3) The sludge accumulation test as at present constituted is not suited for use as a gauge of the condition of a used transformer oil because of the erratic nature of the test results. 30 Scientific LUBRICATION February, 1952

Journal

Industrial Lubrication and Tribology – Emerald Publishing

Published: Feb 1, 1952

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