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United Transformers Electric Company
HERMETICALLY SEALED DISTRIBUTION TRANSFORMERS
OPERATION & MAINTENANCE MANUAL
Second Industrial Estate, Al-Kharj Road, Kilo-19 P.O.Box 385, Riyadh 11383 Kingdom of Saudi Arabia Telephone : +01 – 498 4590 Fax : +01 – 498 3831 Web : www.uteconline.com e-mal : [email protected]
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CONTENTS
PAGE
1. INTRODUCTION .............................................................................................................2 2. WARRANTY ....................................................................................................................2 3. STANDARDS ..................................................................................................................3 4. DESPATCH .....................................................................................................................3 5. RECEIVING AND INSPECTION......................................................................................3 5.1 DOCUMENTS ........................................................................................................................ 3 5.2 INSPECTION ......................................................................................................................... 3
6. LIFTING ...........................................................................................................................4 7. STORAGE .......................................................................................................................4 8. INSTALLATION...............................................................................................................4 8.1 PLACING IN POSITION ......................................................................................................... 4 8.2 TESTING ................................................................................................................................ 5 8.3 CONNECTING AND PUTTING INTO SERVICE.................................................................... 5 8.4 TAP SELECTOR OPERATION .............................................................................................. 5
9. TRANSFORMER MAINTENANCE ..................................................................................5 9.1 GENERAL .............................................................................................................................. 5 9.2 INSPECTION ......................................................................................................................... 6 9.3 MONTHLY INSPECTION ....................................................................................................... 6 9.4 YEARLY INSPECTION ........................................................................................................... 6 9.5 HERMETIC SEALING ............................................................................................................ 7 9.6 OIL LEVEL ADJUSTMENT AFTER SEALING ....................................................................... 8 9.7 VACUUM FILLING ................................................................................................................. 9 9.8 DE-TANKING AND EXPOSURE OF OIL IMPREGNATED WINDINGS TO AIR ................... 9 9.9 REMOVAL OF CONTAMINANT .......................................................................................... 10
10. FAULT FINDING .........................................................................................................10 11. OIL MAINTENANCE ...................................................................................................11 11.1 GENERAL .......................................................................................................................... 11 11.2 OIL SAFETY....................................................................................................................... 11 11.3 OIL SAMPLING (Conservator Units Only) ....................................................................... 11 11.4 INSPECTION OF SAMPLES ............................................................................................. 12 11.5 NEUTRALISATION VALUE ............................................................................................... 12 11.6 ELECTRIC STRENGTH ..................................................................................................... 12 11.7 RESISTIVITY ..................................................................................................................... 13 11.8 MOISTURE CONTENT ...................................................................................................... 13 11.9 SLUDGE............................................................................................................................. 13 11.10 RECOMMENDED ACTION .............................................................................................. 14
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1.
INTRODUCTION The instructions in this manual apply to Hermetically Sealed Distribution Transformer. This transformer is a Hermetically sealed oil filled transformer suitable for outdoor or indoor operation on a distribution system and designed to give prolonged life and low maintenance. The equipment covered by these instructions should be installed, commissioned, operated and maintained by competent and experienced personnel, in accordance with relevant statutory requirements and good engineering and safety practices. These instructions are written for such personnel and are not intended as a substitute for adequate training and experience in the use of this equipment. This manual includes advice and instructions to secure safe and satisfactory service. The Transformer General Arrangement drawing shows the position of the nameplate and warning labels. Read and follow all nameplates and warning labels. Winding connections and masses are shown on the nameplate. Refer to General Arrangement drawing for physical details. Control and Wiring connections are shown on a separate drawing, if applicable.
2.
WARRANTY United Transformers Electrical Company shall make good by repair or, at our option by replacement, defects which, under proper use and in accordance with any instructions issued by us, appear in equipment of our manufacture within a period of twelve (12) months after first placing into service or eighteen (18) months after despatch from our works or, if despatch is delayed by circumstances beyond our control, within a period of eighteen (18) months after the equipment is notified as ready for despatch (whichever period expires earlier) and which arises solely from faulty design, materials or workmanship provided always that (a)
We are notified within seven (7) days of the alleged defect first coming to the purchaser's notice and within the warranty period.
(b)
The defective part(s) is returned promptly to our works free of charge if we so require. We shall return the repaired or replacement part(s) free of charge to the original contract delivery point unless otherwise arranged.
(c)
Any unauthorised repairs or alterations to the equipment shall invalidate this warranty.
This express warranty does not exclude any condition or warranty implied by the appropriate laws or referred to in the Contract.
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3.
STANDARDS The transformers have been designed, manufactured and tested in accordance with the latest issue of the following standards: IEC 60 / AS 1931 IEC 71 / AS 1824 IEC 76 / AS 2374 IEC 137 / AS 1265 IEC 296 / AS 1767 IEC 354 / AS 1078 IEC 422 / AS 1883 IEC 551 / AS 2374 IEC 600 / AS 2421 IEC 722 / AS 2732
4.
High voltage testing techniques Insulation coordination Power transformers Bushings for alternating voltages above 1000V Insulating oil for transformers and switchgear Guide to loading oil immersed transformers Supervision and maintenance guide for mineral insulating oils in electrical equipment Determination of transformer and reactor sound levels Guide to the selection and use of power transformers Guide to the lightning impulse and switching impulse testing of power transformers and reactors
DESPATCH The transformer has been despatched completely filled with oil, hermetically sealed and ready to be connected for service.
5.
RECEIVING AND INSPECTION 5.1
DOCUMENTS Shipping documents, packing list and this manual must be available for reference during the inspection and unloading.
5.2
INSPECTION This transformer has passed all tests and the exacting requirements of Utec Quality System. The shipment has been carried out in accordance with recommended procedures to eliminate damage during normal handling and transport. Immediately upon receipt and prior to unloading from the carrier the transformer should be inspected for external damage. Any damage or discrepancy should be immediately notified to both the manufacturer and the carrier. The following items should be inspected :1. Are all tie-down wires or chains undamaged ? 2. Is all packing tight and in good condition ? 3. Is there any evidence of load shifting in transit ? 4. Are their indications of external damage ? 5. Is the paint finish damaged ? 6. Are all fittings secured and undamaged ? 7. Is there any oil leaks ? 8. Have any bushings been chipped or damaged ?
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6.
LIFTING This transformer has been provided with lifting lugs mounted on the transformer body (see General Arrangement Drawing for their exact location). A spreader bar must be used to avoid damage to the cable box trunkings. Determine the transport mass from the Rating and diagram plate and select the appropriate slings from the following table :-
CHAIN SIZE (mm)
No. OF
HERC-ALLOY
CHAINS
GRADE T 800
7.
SAFE LIFTING LOAD FOR STRAIGHT SLINGS (tonnes) VERTICA L WITH SPREAD ER BAR
60°
90°
120°
INCLUD ED ANGLE
INCLUD ED ANGLE
INCLUDED ANGLE
5.6
2
2.0
1.7
1.4
1.0
7.1
2
3.2
2.8
2.3
1.6
10.0
2
6.4
5.4
4.5
3.2
13.0
2
10.8
9.3
7.6
5.4
16.0
2
16.0
14.0
11.4
8.0
STORAGE Hermetically sealed and conservator style units are sealed and suitable for outdoor storage.
8.
INSTALLATION The location of a transformer has a direct bearing on its service life and efficiency and the following points should be noted when selecting a site :(a) (b) (c)
Facilities for erection and removal. A minimum clearance of 1 m headroom for inspection. A minimum clearance of 0.6 m around the perimeter of the transformer to provide sufficient space for the circulation of cooling air, dissipation of radiated heat and access for maintenance.
The warranty provided by Utec expects that the transformer will receive reasonable treatment. To obtain satisfactory service life it is essential that the conditions under which the transformer is required to operate be given careful consideration. 8.1
PLACING IN POSITION The foundation should be level and of adequate dimensions and strength to give firm support to the transformer. In case of an oil spill consideration should be given to an oil retention soak pit or bund wall of sufficient capacity to contain the transformer oil. Remove all protective coverings or wrappings and if provided, fit rollers.
8.2
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TESTING
The Transformer is hermetically filled with oil and under normal circumstances an oil sample should NOT be taken. Before connecting and putting into service the following tests and checks should be performed :1. 2. 3.
4.
8.3
}
CONNECTING AND PUTTING INTO SERVICE 1. 2. 3.
4.
8.4
Connect the earth terminal to an effective earth. Electrical continuity on all windings and tapping positions. Electrical insulation resistance using a 2500 volt Megger, measure :HV to tank LV to tank Minimum acceptable 500 Mohm @ 20 °C HV to LV If possible measure the winding resistance and compare the results with those on the Certificate of Test and Inspection.
The tank earth terminal shall be connected to an effective earth. Connecting leads should be symmetrically arranged in order to equalise the impedance voltage drops. Refer to the Rating and diagram plate for the correct terminal identification. Check that all mating joints are clean, bolted connections are tight and locked and ensure that tap selector is set for the required voltage. This is particularly important if transformers are to be operated in parallel. Incorrect external connection could result in serious damage. If in doubt consult the manufacturer. Repair all damage to the external paint finish.
TAP SELECTOR OPERATION This transformer is fitted with a padlockable, rack and pinion operated off-circuit tap selector. IMPORTANT: The transformer must be completely de-energised before operating the tap selector, ie. when the transformer is disconnected from all supply sources including possible back feed from the LV system. A notch is provided to mark each position with precision. To change tap position, unscrew the central locking nut 5 mm and release the notch by pulling upwards on the control knob. Turn the control knob to the selected position, engage the notch with a downward push on the control knob and then screw up the lock nut.
9.
TRANSFORMER MAINTENANCE 9.1
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GENERAL The frequency of maintenance depends on the transformer fittings, environment and loading. Safety precautions should be observed when conducting inspection or maintenance.
9.2
INSPECTION There are two recommended categories of inspection :1. 2.
Monthly Yearly
Monthly inspection can be carried out without any interruption to service and by an observer at "ground level". At approximately yearly intervals or at convenience, the transformer should be taken out of service so that a more comprehensive and thorough examination can be made. At the same time, the operation of various protection devices and operating gear can be checked. 9.3
MONTHLY INSPECTION 1.
Leakage of oil Look for signs of oil leakage from flanges, tap selector handle mechanism, valves or sealing plugs. If any oil leakage is found, the transformer should be de-energised at the next convenient interval for corrective action. Do not top up with new oil until any leakage is cured.
2.
If Automation 2000 fitted Check the oil level in the automation 2000.
9.4
YEARLY INSPECTION 1.
Transformer tank Examine the transformer tank and fittings to ensure that there is no build up of excessive dirt or other foreign matter which could prevent dissipation of heat and encourage corrosion. Also examine for any metal corrosion, especially at the welded seams. If corrosion is found it should be completely removed with a wire brush or other means and the paint finish restored.
2.
Cooling fins In order to maintain the thermal efficiency of the transformer it is essential that the external surfaces are kept dirt free and clean.
3.
Leakage of oil Look for signs of oil leakage from flanges, welded joints, tap selector handle mechanism, valves or sealing plugs. If any oil leakage is found, tighten up cover bolts or screw down valve or sealing gland in question. Do not top up with new oil until any leakage is cured.
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Gasket joints
Examine all flange joints on tank cover, cable boxes and inspection openings (if fitted) and accessories for oil or water leaks. Correct any leaking gaskets by retightening. The tightening of gasket joints must be carried out carefully and gradually to avoid undue stress on bolts or studs, and distortion of the joint. Nuts and bolts must be tightened a little at a time in sequence diametrically opposite wherever possible. When tightening, recommended torque settings are :Tank lid (M10)
50 Nm
Cable box and cover (M10)
30 Nm
Inspection cover
50 Nm
Gland plates (M10)
30 Nm
Tap selector gland
5 Nm
LV bushing connector (M10)
50 Nm
HV bushing clamp (M10)
10 Nm
Filler stack 32 mm BSP plug
3/4 turn after bottoming
Drain valve 25 mm BSP plug
3/4 turn after bottoming
Automation 2000 filler cap
1/2 turn after bottoming
Automation 2000 clamp (M8)
5 Nm
If, after carrying out the tightening described above, the oil leak still persists, the oil should be lowered below the gasket level and an inspection of the gasket carried out. If damage or deterioration is evident, a replacement gasket should be fitted and the transformer topped up and sealed. 5.
Terminal connections Check the integrity of all cable boxes, and that the box fronts and gland plates are bolted up tightly. Ensure that all bushings are clean and intact. Examine all porcelains for minute cracks or other damage. Check that all cables are firmly supported so that no weight or mechanical strain is imposed on the transformer terminals.
9.5
HERMETIC SEALING To prolong the oil life, hermetically sealed transformers are completely filled with oil by the manufacturer to prevent moisture and air entering the transformer. If for some reason there is a need to open the unit, the following procedure should be followed:1.
To relieve pressure - With the top flanged plug or filler cap (Automation 2000) closed, allow oil to drain from transformer through the bottom valve. Continue to drain oil until flow stops.
2.
To remove lid - Open the top flanged plug or filler cap and open the drain valve to allow sufficient oil to drain from the transformer, so that the level of the oil is about 50 mm below the lid of the tank. The depth of the oil can be checked with a clean dip stick. Close the drain valve.
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9.6
OIL LEVEL ADJUSTMENT AFTER SEALING The sealing of the transformer is critical and should not be undertaken before reading the following instructions. Measure the top oil temperature.
1.
Top Oil Temperature ≥ 25 °C a)
Ensure bottom drain valve is closed and top up the transformer via the top filler stack (or Automation 2000 if fitted). Oil level must be to the very top of the filler stack. Close filler cap.
b) 2.
Top Oil Temperature < 25 °C a)
Obtain oil volume of the transformer from rating plate.
b)
Using the table below, determine the oil volume which must be removed from the transformer.
c)
Keep filler cap closed. Open drain valve and drain required amount of oil out of transformer.
d)
Close valve securely and seal with the flange plug.
OIL VOLUME (Litres) TO BE EXTRACTED FOR TEMPERATURES BELOW 25°C
TEMPERATURE OF TRANSFORMER OIL °C
OIL VOLUME
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Litre
1 5
1 6
1 7
1 8
1 9
2 0
2 1
2 2
2 3
2 4
100
1
1
1
0
0
0
0
0
0
0
200
1
1
1
1
1
1
1
0
0
0
300
2
2
2
1
1
1
1
1
0
0
400
3
2
2
2
2
1
1
1
1
0
500
3
3
3
2
2
2
1
1
1
0
600
4
4
3
3
2
2
2
1
1
0
700
5
4
4
3
3
2
2
1
1
0
800
5
5
4
4
3
3
2
2
1
1
900
6
5
5
4
4
3
2
2
1
1
1000
7
6
5
5
4
3
3
2
1
1
1100
7
6
6
5
4
4
3
2
1
1
1200
8
7
6
5
5
4
3
2
2
1
1300
8
8
7
6
5
4
3
3
2
1
1400
9
8
7
6
5
5
4
3
2
1
1500
1 0
9
8
7
6
5
4
3
2
1
If the volume of the transformer lies between the values shown in the Table, take the next highest value eg. 550 litres use 600 litres instead. 9.7
VACUUM FILLING All transformers built by United Transformers Electric Company are vacuum filled using an Autoclave. Any transformer that has been completely drained of oil, must be refilled under a vacuum. Failure to follow this requirement could result in damage to the transformer. Consult the manufacturer if in doubt.
9.8
DETANKING AND EXPOSURE OF OIL IMPREGNATED WINDINGS TO AIR
In some cases when it may become necessary to un-tank the transformer, it may only be done with manufacturer’s consent. If there is any suspicion that gasses accumulated in the transformer tank (underneath the cover) no electrical measurements may be taken. This may result in a spark and cause an explosion of accumulated gases. Measurements may be taken when the active transformer part is removed from the tank. When un-tanking the transformer, the following sequence must be observed: • • • • • • • • •
Disconnect all cable leading to HV & LV bushings, Drain about ¼ of total quantity oil in the tank through the drain valve Disassemble and remove cable boxes Disconnect all cables leading to additional accessories, equipment and protection devices, Undo fastening nuts and bolts on the cover. Remove active part fixing bolts ( 4 Nos. ) inside the tank Remove active part fixing plate. Lift the active part through lifting eye available at the top of end clamp via suitable lifting eye and chain. Allow some time for excess oil to drain from active part and place it in the dry and clean place. Exposure of oil impregnated transformer windings and insulation to air will result in the absorption of moisture into the insulation. Although the rate of absorption is slow and little water will be absorbed it is correspondingly much more difficult to extract. When an oil impregnated core and coils assembly or internal insulation is exposed to air the maximum permissible exposure time before redrying is required is as follows:
System Highest Voltage
Maximum Exposure Time (Hours)
of Transformer
Relative Humidity ≤ 85%
Relative Humidity >85%
≤ 36 kV
30
24
Should the above exposure time be exceeded a re-dry is necessary (consult the Manufacture for detailed drying procedure.
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9.9
REMOVAL OF CONTAMINANT If a small amount of contaminant enters a transformer, it should be removed immediately, by means of a "suction thief", eg. 12 mm bore pipe attached to a pump, all globules of water and pieces of rust, dirt etc. from horizontal surfaces before any oil circulation occurs. At this time a visual inspection must be made to ascertain the extent and nature of the contamination. If in doubt, consult the manufacturer.
10.
FAULT FINDING Should the transformer malfunction or trip the protection circuit when in service, the following procedure should be used to determine the probable fault before contacting manufacturer. TYPE OF FAULT: No HV Volts POSSIBLE CAUSE: Transformer not connected to supply. Supply to transformer is not switched on. Metering equipment is not connected properly. Open circuit fault on HV supply. Short circuit fault on HV supply. Short circuit fault on HV bushings. Transformer has been struck and damaged by lightning. ACTION:
Investigate all possible causes of non-supply. Inspect transformer for any evidence of a lightning strike or switching surge.
TYPE OF FAULT: No LV Volts POSSIBLE CAUSE: Transformer not connected to HV supply. HV supply to transformer is not switched on. Open circuit fault on HV supply. Short circuit fault on HV supply. Short circuit fault on HV bushings. Transformer has been struck and damaged by lightning. No connection to the LV side of the transformer. LV metering equipment is not connected properly. No connection to LV terminals. ACTION:
Investigate all possible causes of non-supply. Inspect transformer for any evidence of a lightning strike or switching surge.
TYPE OF FAULT: Voltage of LV is incorrect POSSIBLE CAUSE: Tapselector is on the wrong tap position. HV phase missing. ACTION:
Change tap position of the transformer. Investigate all possible causes of non-supply.
TYPE OF FAULT: Oil appears around or on the transformer POSSIBLE CAUSE: Tank is leaking. Gaskets are leaking. Fittings are damaged and are leaking. Page-10/14
ACTION:
Check for damaged tank or fittings. Inspect for leaking gaskets.
TYPE OF FAULT: Oil is not visible in sight gauge (if fitted) POSSIBLE CAUSE: Tank is leaking. Gaskets are leaking. Fittings are damaged and are leaking. Trapped air. ACTION:
11.
Check for damaged tank or fittings. Inspect for leaking gaskets. Bleed trapped air
OIL MAINTENANCE This transformer is hermetically filled with oil and under normal circumstances an oil sample should NOT be taken. 11.1
GENERAL The oil supplied with the transformer is a pure hydro carbon mineral oil conforming to the requirements of IEC 296 and with this manual. The functions of the oil are :1. 2.
To serve as a medium for the transfer of heat from the windings and core to the tank and coolers. To serve as an electrical insulator.
Therefore it is important that :1. 2.
Nothing should diminish the circulation of the oil The oil should be kept free from moisture, dust, and anything which may tend to reduce its dielectric strength.
All equipment used for handling and processing of oil should be flushed through with clean oil before use. The oil in a transformer operating under normal load conditions, adequately ventilated, and free from moisture, will show little oil deterioration after years of service. If, due to overload or inadequate ventilating conditions, the oil temperature is high (approx. 120 °C) for prolonged periods deterioration of the oil will be accelerated. 11.2
OIL SAFETY Proper safety procedures should be used to prevent vapour inhalation and skin contact with mineral oil. Excessive and prolonged exposure to mineral oil and/or its vapour can cause headaches, confusion, nausea and lack of co-ordination.
11.3
OIL SAMPLING (Conservator Units Only) 1. 2. 3.
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Observe and implement all electrical safety requirements. Samples of oil should be drawn from the transformer when the oil is warm. Check that there is sufficient oil in the transformer to allow a sample to be taken.
4.
5. 6.
7.
8. 9.
11.4
Ensure that the valve from which the sample is to be taken is closed, and then remove the plug and sealing washer. Clean the external surface and threads of the valve. Finally the valve should be flushed by draining off a minimum of 0.75 litre of oil to ensure that the sample obtained is representative of the oil at the bottom of the tank. Collect this oil in a polished container and examine it for foreign matter, water or sludge. Approximately 1/4 fill a 0.5 litre clean sample bottle with oil from the equipment. Wash the stopper with oil from the bottle and then fit the stopper and rinse the bottle. Drain, and allow the bottle to remain inverted for at least 10 seconds. Repeat this rinse. Fill the bottle with the test sample. To prevent aeration, avoid splashing the oil directly into the bottle, but allow the oil to run down the side of the bottle. Wash the stopper by allowing a small quantity of oil from the bottle to flow over it, then immediately fit the stopper. Do not carry bottles by holding a hand over the stopper. The oil samples must not be exposed to the air or sunlight for any longer than is necessary. Label the bottle, recording details, such as serial number, date and time of sample, tests required, signature. Tests should be carried out as soon as possible after drawing a sample.
INSPECTION OF SAMPLES A limited but useful amount of information can be obtained from the odour and colour of the oil. Cloudiness in the oil may be due to suspended moisture or suspended solid matter, such as iron oxide or sludge. The moisture can be detected by a crackle test. If the oil is dark brown, the presence of dissolved Asphaltenes may be suspected. If the colour is green the presence of copper soaps is indicated and it may be expected that further deterioration of the oil will be rapid. An acrid acid smell is indicative of volatile acids which can cause internal corrosion and which may render the oil unsuitable for treatment on site. A petrol-like or acetylene odour may indicate a low flash-point due to a fault or some other cause.
11.5
NEUTRALISATION VALUE The neutralisation value of an oil is a measure of the acidic constituents or contaminants in the oil. When the acidity is above 0.5 mg KOH/g the oil should be reconditioned or replaced.
11.6
ELECTRIC STRENGTH The dielectric breakdown voltage is an important measurement of the electrical stress which an insulating fluid can withstand without failures. The dielectric strength, measured in accordance with IEC 296, should be not less than the following :-
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System Highest Voltage of Transformer
Dielectric Strength of Oil kV r.m.s Before Filling
After Filling
≤ 36 kV
50
40
The electric strength can be increased by filtration, to remove moisture and fibres. Experience indicates that oil is sometimes rejected unjustifiably because inadequate care is taken during sampling. Attention is accordingly drawn to the importance of correct sampling procedures. 11.7
RESISTIVITY Then resistivity new oil after filling shall be not less than :60 GΩ.m @ 90 °C
11.8
MOISTURE CONTENT The "Crackle Test" for moisture is a simple and useful test for detecting the presence of suspended moisture in oil. This only detects free water above the saturation point i.e., @ 20 °C ≥ 50 mg/kg. Two alternative methods of performing the Crackle Test are as follows :A.
Quarter fill a clean, dry 13 mm diameter test tube with the oil to be tested, taking care that the oil is not aerated. Place the test tube and sample into a silent flame, heating the oil as fast as possible until it boils. Audible crackling will be heard if moisture is present. The oil shall be considered to have passed the test if no crackling occurs with 2 of the 3 quantities tested.
B.
Fill a clean, dry container with 300 ml of oil. Heat a metal rod 13 mm diameter to a dull red and stir the oil with it. Audible crackling will be heard if water is present.
WATER CONTENT The water content, measured in accordance with IEC 296, shall be not greater than the following :System Highest Voltage of Transformer
≤ 36 kV
11.9
Water Content mg/kg of Oil Before Filling
After Filling
15
20
SLUDGE Although severe sludge is not frequently experienced in transformer oil in service, it is nevertheless a most serious form of deterioration. When sludge is allowed to accumulate, the oil circulating ducts become blocked causing higher core and winding temperatures. This increases sludge formation until eventually transformer failure results. A transformer with sludge deposits is difficult to clean thoroughly without dismantling.
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11.10 RECOMMENDED ACTION The action to be taken following testing is as detailed below :-
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1.
Where a test result is outside the recommended limits, a fresh sample should be taken for further tests before any other action is taken.
2.
As a general rule, several characteristics have to be unfavourable in order to justify rejection of the oil. If the electric strength is below the limits given then, irrespective of the values of the other characteristics, action is essential.
3.
Where oil is confirmed as failing to meet the limits and the cause is unknown, it is advisable to consult an oil supplier or the transformer manufacturer.
4.
Where refilling is required following oil treatment the equipment should be thoroughly flushed through with unused oil before refilling.
