gassing tendency of oil
TRANSCRIPT
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GASSING TENDENCY IN TRANSFORMER OIL
(A key aspect for selection of oil)
Y. V. JOSHIDy. Engr. (Engg)
GUJARAT ENERGY TRANSMISSION CORPORATION LIMITED
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GASSING TENDENCY IN TRANSFORMER OIL
What is gassing tendency of transformer oil?
How gases generate in transformer?
Role of gassing characteristics
Positive gassing tendency
Negative gassing tendency
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GASSING TENDENCY IN TRANSFORMER OIL
Transformers today
Parameters affecting generation of gas in oil- constitution of oil- type of discharge- the voltage- the current & frequency of stresses- severity of fault- presence of other materials like solid insulation
temperature & pressure
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GASSING TENDENCY IN TRANSFORMER OIL
Positive gassing tendency
Negative gassing tendency
Relation between oil and gas absorption.
Use of gas absorbing characteristics of oil
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GASSING TENDENCY IN TRANSFORMER OIL
Poly Aromatic content (PCA)
Poly Cyclo Aromatic (PCA)
Effect of their presence in oil
Health and safety issue
Use of gas absorbing oil in transformer
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GASSING TENDENCY IN TRANSFORMER OIL
Recommendation of IEC 60296 for gassing tendency of oil
Requirement of positive gassing tendency for oil used in Transformer
Requirement of negative gassing tendency for oil used in Instrument transformers
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GASSING TENDENCY IN TRANSFORMER OIL
CASE STUDY:The various data collected from various manufacturers is studied in one of biddings in GETCO and put up for reference.
MAKE W X Y ZOil Base Paraffinic Paraffinic Naphthanic Paraffinic
Total Paraffin 63.45 % 69.1% <46% 64%Content
TotalNaphtha 34.9% 17.3% >46% 33%Content
TotalAromatic 1.25% 13.6% 4 – 8% 12%Content
Gassing 3.2 -11.1 +5 max -18.67Tendencyin mm3/min
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From above, it can be derived that1) According to content of paraffin or naphtha the final
product is called as paraffinic based or naphthanic base oils.
2) Gassing tendency is controlled by aromatic content
in oil. For lower aromatic content, transformer oil will be of positive gassing tendency.
3) Increasing aromatic content beyond certain level, the gassing tendency changes from evolving nature to absorbing.
4) Positive gassing tendency is possible in both paraffin and naphtha based oil.
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CONCLUSION:
It is required to consider gassing tendency as one of the major characteristic while selecting oil.
For power transformers, oil with positive gassing tendency is desirable. Limit for positive gassing tendency may be adopted between 0 and 5 mm3/min.
For instrument transformers oil with negative gassing tendency may be used.
To balance the parameters like oxidation stability & gassing tendency the aromatic contents have to be maintained at certain level during refining process, otherwise neutralization value and sludge formation will be more with ageing of oil.
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Flow chart of gassing tendency
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References: (1) Dr. V. Shrinet & M J Patel, ERDA, paper in LAWPSP, Bombay 1997,
(2) Revised IEC std – Prof. B. Pahlavanpour, Nynas,
(3) Poly Aromatics – A key to the properties of insulating oils.
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ACKNOWLEDGEMENTS:
I am very much grateful to the GETCO management for granting permission to publish this paper.