transformer oil related aspects

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TRANSFORMER OIL RELATED ASPECTS

OIL PLANT CAPACITY

60KL/Day(Now we are enhancing to 120KL/Day from existing 60KL capacity)A) TOBS storage capacity-1000KL(600KL tank-1no,100KL tanks-4nos)B) In process Oil storage capacity-125KL(20KL filters-3nos,10KL filters-6nos and 5KL filter-1no)C) Finished Oil storage capacity-390KL(240KL tank-1no,100KLtank-1no and 25KLtanks-2nos.

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FUNCTIONS OF TRANSFORMER OIL

To provide dielectric strength of the transformer insulation system.

To provide efficient cooling.To protect the transformer core and coil

assembly from chemical attack.To prevent the build up of sludge in the

transformer.

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PRODUCTION OF TRANSFORMER OIL

Transformer oil is hydrocarbon product,mainly oil contains napthanic,parrafinic and aromatics.

To obtain the TOBS the crude oil which is burried from earth crust subjected in to the following sequence of operations .

Distillation-Acid treatment-Neutralization-Water wash-Hot air blowing.

Clay treatment process on TOBS will give us the finished transformer oil.

After the hot filtration operation transformer oil is ready for filling the transformers.

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DETORIORATION ASPECTS OF TRANSFORMER OIL

Deterioration due to the accidental leakage of water .

Deterioration due to the chemical decomposition.Deterioration due to the oxidation.Deterioration due to the contamination by gases.Deterioration due to the electrical stresses.Deterioration due to the thermal stresses.Deterioration due to the effect of oxidation products.Deterioration due to the physical contamination.

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PRECAUTIONS INVOLVED IN TRANSFORMER OIL SAMPLING.

The utmost care should be taken to avoid contamination of samples with external impurities such as dust and moisture.

Attention is drawn to the danger of sampling in rainy or foggy weather.

The hands of the sampler should not come into contact with the samples.

Care should be taken when sampling oil colder than the surrounding air, to avoid contamination by condensation.

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PRECAUTIONS INVOLVED IN TRANSFORMER OIL SAMPLING.

Only glass sample containers,preferably fitted with ground glass stopper,should be used.

Cotton waste or other fibrous materials should not be used to wipe the containers or apparatus.

Where practicable,if a bottom sample is required the contents of the tank or package,after movement,should be allowed for at least 8Hrs,preferably 24Hrs before sampling.

Before the actual sample is taken,the entire sampling apparatus and containers should be rinsed with the oil,which should then discarded

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PRECAUTIONS INVOLVED IN TRANSFORMER OIL SAMPLING.

To remove any moisture or dirt on the surfaces over which the oil sample will flow a small amount of oil should be allowed to flow from the tank or package and run to waste before the sample is taken.

Samples that are to be tested for sludge,corrosive sulphur or tan delta should be protected from light.

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TRANSFORMER OIL

Specifications for Testing of transformer oil.IS-335ASTM-D3487IEC-60296BS-148JIS-2320

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IS-335SPECIFICATION

APPEARANCE:Clear transparent and free from suspended matter and or sediments.

DENSITY:IS-1448 P(16) HYDROMETER/THERMOMETER DESIGN VALUE—0.89 gms/ml @29.5°C max

KINEMATIC VISCOCITY:IS-1448 P(25) CONSTANT TEMPERATURE BATH THERMOMETERS/STOP WATCH DESIGN VALUE—27cSt @ 27 °C max

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IS-335SPECIFICATION

INTERFACIAL TENSION:IS-6104 INTERFACIAL TENSIO METER DESIGN VALUE—0.04N/M max

FLASH POINT:IS-1448 P(21) PENSKY MARTINS CLOSED CUP FLASH POINT TESTER/THERMOMETERS. DESIGN VALUE—140 °C min

POUR POINT:IS-1448 P(10) CLOUD POINT&POUR POINT APPARATUS/THERMOMETERS DESIGN VALUE-- -6 °C max

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IS-335SPECIFICATION

NEUTRALIZATION VALUE:IS-1448 P(2) CONICALFLASKS/BURETTES/MEASURING CYLINDERS/BURETTE STANDS/ VOLUMETRIC FLASKS DESIGN VALUES-- A. TOTAL ACIDITY : 0.03mgKOH/gm B. INORGANIC ACIDITY: NIL

ELECTRIC STRENGTH(BDV): IS-6792 BDV TEST SET DESIGN VALUES A. UN FILTERD :30kv min B. FILTERD : 60kv min

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IS-335SPECIFICATION

DIELECTRIC DISSIPATION FACTOR (TAN DELTA):IS-6262 TANDELTA TEST SET/OIL CELL HEATER/OIL CELL. DESIGN VALUE : 0.002 max

RESISTIVITY : IS-6013 RESISTIVITY TEST SET/OIL CELL HEATER /OIL CELL DESIGN VALUES A. 1500*10E12 Ohm-cm @27 °C min

B. 35*10E12 Ohm-cm @90 °C min

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IS-335SPECIFICATION

PRESENCE OF ANTI OXIDATIVE INHIBITOR :IS13631

MEASURING CYLINDERS/PIPPETES/ BURETTES/BURETTE STANDS

DESIGN VALUE : NOT DETCTABLEWATER CONTENT : IS-13567 AUTO MATIC KARLE FISHER

TITRATOR/WEIGHING BALANCE DESIGN VALUE : 50PPM max

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IS-335SPECIFICATION

CORROSIVE SULPHUR : IS-335 ANNEX-B TEMPERATURE CONTROLLED OVEN/CONOCAL FLASKS/FORECEPS

DESIGN VALUE : NON CORROSIVE OXIDATION STABILITY :IS-335 ANNEX-C

OXIDATION STABILITY BLOCK/ VACUUM PUMP/OXIDATION TUBES/G-4 FILTERS/BURETTES/BURETTE STANDS/ CONICAL FLASKS/WEIGHING BALANCE. DESIGN VALUES A.NEUTRALIZATION VALUE:0.4mgKOH/gm

B. SLUDGE % BY MASS :0.1max

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IS-335 SPECIFICATION

AGEING CHARACTERISTICS: IS-12177 AGEING OVEN /WEIGHING BALANCE/

VACCUME PUMP/ G-4 FILTERS/ BURETTES/BURETTE STANDS/ CONICAL FLASKS.

DESIGN VALUES A.RESISTIVITY@27DegC-2.5Ohm-cm min

B.RESISTIVITY@90DegC-0.2Ohm-cm min C.TANDELTA@90DegC-0.2 max

D.TOTAL ACIDITY -0.05mgKOH/gm E. TOTAL SLUDGE –0.05%

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NABL RECUREMENTS IN OIL LAB

Equipment history cardsMeasurement uncertainty calculations.Regular calibrations of instruments from NABL

accredited laboratories.Interlab comparison

Replicate testing

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APPEARANCE TEST

APPEARANCEMeasurement uncertainty calculation for

transformer oil appearance test Sources of uncertainty a) Improper sampling b) Presence of sediments and suspended matter in the bottles used for sampling c) Persons skills

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APPEARANCE TEST

a) Improper sampling : To avoid the uncertainty due to improper sampling the following care should be taken 1) Don’t use the cotton waste while sampling 2) Don’t pickup the sampling in dust and foggy weather 3) Clean the sampling point (pipe end) before sampling

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APPEARANCE TEST

b) Presence of sediments and suspended matter in the bottles used for sampling : The test results may be effect due to the contamination of

sediments and suspended matter, if any present in the sampling bottles. Bottles should be thoroughly clean before sampling by using the following cleaning agents as per the sequence

1) Tap water 2) Soap solution 3) Tap water 4) Hot distilled water 5) Acetone and allow for oven drying at 110°C for 1hr. And then vacuum with the vacuum pump.

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APPEARANCE TEST

Persons skills : Person skills may also be the one of

the reason for effecting the test results. To avoid this problem . The following persons will take care in the bottles cleaning and reporting the results

01) P.SRINIVAS RAO

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BRAKE DOWN VOLTAGE TEST

Measurement uncertainty calculation for BDV test on transformer oil

Sources of uncertainty 1) Test results obtained 2) BDV test set resolution

3) BDV test set calibration 4) Atmospheric condition

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BRAKE DOWN VOLTAGE TEST

Results obtained . Repeated measurements on sample transformer oil sample a) ( 68,74,72,60,68,64) = 67.6kv

b) (66,72,80,64,68,62) = 68.6kv c) (68,70,70,68,80,76) = 72.0kv d) (72,62,76,68,82,68) = 71.3kv e) (64,66,78,72,68,70) = 69.6kv

Average value = 69.82kvSt. Deviation = (-2.22)2+(-1.22)2+(2.18)2+(1.48)2+(-0.22)2 / 4 =

(4.9284+1.4884+4.7524+2.1904+0.0484) / 4

= 1.8308Type A uncertainty = 0.818kv

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BRAKE DOWN VOLTAGE TEST

2)BDV test set resolution : (B1)uncertainty due to BDV test set resolution = 2 / 2 3 = 0.577kv

3) BDV test set calibration : (B2)uncertainty due to BDV test set calibration. = 1.9 / 2 = 0.95kvType B uncertainty = (B1)2+(B2)2 = (0.572)2+(0.95)2 = 1.1115kvcombined uncertainty = (Type A)2+(Type B)2

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BRAKE DOWN VOLTAGE TEST

combined uncertainty = (Type A)2+(Type B)2 = (0.818)2+ 1.1115)2

= 1.38kv

Note :4 Room temperature and relative Humidity

maintained at 27°C and 44% RH respectively so uncertainty due to Atmospheric Conditions is not Considered

Expended uncertainty = 2 x 1.38 = 2.76kvAt 95% confidence level with respeet to 69.82kv

69.82 ± 2.76

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INTERLAB COMPARISION

Brake down voltage Inter lab comparison 1) PGCL values = 73.1kvVijai electrical value = 69.3kvDifference = 3.8kv Uncertainty = 3.01kvZ = Difference / uncertainty = 3.8 / 3.01 = 1.26Z Value is less than 2 OK

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INTERLAB COMPARISION

ERDA VALUE = 64.0kvVijai electrical value = 69.3kvDifference = 5.3kv Uncertainty = 3.01kvZ = Difference / uncertainty = 5.3 / 3.01 = 1.76Z Value is less than 2 OK

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INTERLAB COMPARISION

CPRI VALUE = 87.0kv Vijai electrical value = 69.3kvDifference = 17.7kv Uncertainty = 3.01kvZ = Difference / uncertainty = 17.7 / 3.01 = 5.88Z Value is higher than 2 (Not OK) The value of BDV reported By CPRI Bangolure

appears to be very high . Requested CPRI to examine the same