TRANSFORMER OIL FILLING PROCEDURE

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TRANSFORMER OIL FILLING PROCEDURE

• Cooling fans and pumps shall operate correctly and that fan and pump motors have correct over current protection, if applicable. NETA, ATS­Sec.7.2.2.1.11 .
• Correct liquid level shall be verified in all tanks and bushings. NETA,  ATS-Sec.7.2.2.1.13.
• Operation of all alarm, control, and trip circuits shall be verified from temperature and level indicators, pressure relief device, and fault pressure relay, if applicable. NET A, ATS-Sec. 7 .2.2.1.10 .
• Transformer tank shall meet the Standard requirement of SAES-P-111, Sec. 9.
• Insulation resistance test shall be performed before and after installation of surge arresters.
• Surge arrester grounding shall be as per SAES-P-107, Sec. 11.3.
• Cooling fans and pumps shall operate. (7.2.2.1.11) NETA, ATS­ Sec.7.2.2.3.3.1.2 .
• Insulating transformer oil shall be tested for -Dielectric breakdown voltage, Water content, Acid neutralization number, Specific gravity, lnterfacial tension, Visual condition, Color, Power factor tests. NETA, ATS-Sec.7.2.2.2.10 and ANSI/ IEEE C57.106.

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Oil Processing and Filling Procedure by Approved 3rd Party

• Inspect he seal of the delivered oil drums. Unsealed drums be set aside and not to be included in the filling. Never ever take chances for any unsealed drums, a small amount of solvents, hydraulic and engine oils, diesel fuel and water will eventually jeopardize the whole process.
• Randomly check sampling of oil received in drums in different palettes.
• Sampling of Oil received in bulk container should be taken one sample for  each container.

Oil filling and Oil Processing of the Transformer.

• Position the oil processing and filling unit at the cleared area besides the ransformer. Hard barricading the area to ensure that only authorized personnel are within the filling and processing area.
• Place the oil in drums besides the oil processing and filling unit near its oil  intake suction pipe.
• Connect the intake suction to the oil drum using hydraulic hose.
• The oil processing and filling unit suck the oil from drums to the heating tank  then degassed unit and filled in to the transformer.
• transformer Oil filling is in progress, open the radiator valve one by one until such time the  radiator is filled with oil.
• Fill the oil up to the desired level in the oil level gauge. The level should  coincide with the equation of oil level against temperature mark in the oil temperature gauge.
• The temperature gauge is furnished to indicate to top liquid temperature in the tank.

After filling of Transformer, Oil Circulation follows.

• Connect the oil filling return hose at the top portion of the transformer main tank.
• Connect the oil suction hose at the bottom portion of the transformer main tank.
• Start circulation of oil continuously for up to 24 hours.
• This step is necessary to ensure that the oil, core and winding in the transformer get more additional drying.
• Lastly, take approximately (1) litre of oil for dielectric strength test and other test required to ascertain health oil.
• Transformer furnished with Pressure/ Vacuum Gauge, If the gauge read zero and does not change the transformer should be checked for possible leak. A leak will allow moisture and air to enter the transformer, which could degrade the insulation and oil.

Additional Procedure as Required by Approved 3rd Party

• Ventilate the gas space with dry air to purge it of the nitrogen gas that it contains.
• Dry air should be used to ventilate the inside of the tank when it is opened for internal fitting.
• Temperature of dry air entering the transformer shall be at least as high as that of the transformer and at least 10° higher than the dew point of the outside air.
• Dry air shall be blown into the transformer so as to create a flow of air through the cover opening.
• The dew point in the transformer should never be higher than 20°F.
• When nitrogen is called for, the nitrogen used should have a dew point not higher than -50°C (-58°F) and total impurities not exceeding 0.1 % by volume. 7.7.1.7 Nitrogen can be obtained in high pressure steel cylinders, or in some locations in insulating low pressure containers in liquid form, or in some location in insulating low pressure container in liquid form.
• When nitrogen is supplied from high pressure cylinder the proper regulating valve must be used introducing the gas in to the transformer tank.
• Cylinder should not be completely emptied, but should be returned to the supplier with least 25psi residual pressure.

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Vacuum Pressure Requirements During Oil Filling: by Approved yd Party

• When transformer is to be filled or topped off in the field, they must be filled under vacuum according to specific instruction. (These specific instructions are Vendor provided).
• Transformer should not be left under vacuum except during the vacuum filling operation.
• Leaks in the temporary piping and connections lead to danger of drawing moisture into the tank if it is under vacuum during periods of high humidity or during rain.
• It is recommended that the tank be under positive pressure during rain to prevent drawing moisture in to the tank.

Approximate Duration (hour) before breaking the Vacuum: by Approved 3rd Party

The vacuum time is based on the transformer rating, voltage and the Company Specifications.

Process on how to break the Vacuum: by Approved 3rd Party

• The pressure-vacuum gauge indicates the tank gas space pressure relative to atmospheric pressure.
• The pressure relief device will vent tank gases when excessive tank pressure exists.
• The device consists of a self-resetting, spring loaded diaphragm and a mechanical operation indicator (Semaphore).
• The maximum tank pressure at which the pressure relief device will remain sealed is stamped on the relief device nameplate.
• Should the tank pressure increase above the pressure relief device nameplate rating, the gas pressure will lift the diagram, vent the excess pressure and trip the Semaphore.
• The pressure relief device will withstand full vacuum and need not be removed from the transformer tank during any vacuum.
• A hood may be bolted over the relief device.
• When supplied, the hood must be vented to the outdoors.

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