LAB5.docx - POWER SYSTEM PROTECTION SWITCHGEAR LAB ASSIGNMENT 05 SURABHI RAMAN 17BEE0029 TESTING OF BREAKDOWN VOLTAGE STRENGTH OF THE GIVEN SAMPLE OF

LAB5.docx - POWER SYSTEM PROTECTION SWITCHGEAR LAB...

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POWER SYSTEM PROTECTION & SWITCHGEAR LAB ASSIGNMENT - 05 SURABHI RAMAN 17BEE0029
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TESTING OF BREAKDOWN VOLTAGE STRENGTH OF THE GIVEN SAMPLE OF TRANSFORMER OIL USING TRANSFORMER OIL TESTING KIT Ex.No : 05 OBJECTIVES: 1. To know the operation of transformer oil test set. 2. To measure the Breakdown voltage of given specimen of transformer oil. APPRATUS REQUIRED S.No Description Range Type Quanti ty 1. Transformer Oil Testing Kit (0 – 60) kV Ac 1 2. Gauge Plate 2.5,4.0mm - 1 3. Screw Driver - - 1 4. Sample Oils - - As req. THEORY : High voltage distribution and power transformers are mostly filled with oil. The functions of the oil are to provide additional cooling to the core and winding and to improve insulation between windings and the earth. Similarly, insulating oil is also used in low and medium voltage switchgear. Since it is mostly used in transformers, it is commonly known as transformer oil. The transformer oil is obtained by refining suitably selected natural petroleum crude. The synthetic transformer oil is also available in the market but the use of mineral oil is preferred due to its property of self-restoration after dielectric discharge or puncture. The transformer oil must comply with the Bureau of Indian Standard Specifications IS-335 - 1983in respect of its tendency towards sludging, acidity, flash point, dielectric strength, etc. Description of all the tests performed to ascertain suitability of the oil is beyond the scope of this experiment and only dielectric strength verification will be dealt with. The electric strength of transformer oil as per IS:335 - 1983, (amended July, 1987) should be as given below:
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(a) New unfiltered oil 30 kV (rms.) (b) After filtration 60 kV (rms.) If the unfiltered oil does not withstand 30 kV (rms.), the oil should be filtered and re- tested. The electric strength of the oil is tested by finding the breakdown voltage at which there is visible arcing through the oil across two electrodes. In order to standardize the results, The test has to be carried out in a standard vessel (or test cell ) as described in IS:6792. Since high voltage ac is to be applied across two electrodes dipped in the test
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