Service Manual
TRANSFORMER
HV / LV TRANSFORMERS
Revision April 2008
Prepared By Kobie Botha
Reviewed By Ray McElhinney Approved By Jack Denz
Aggreko International Technical Services
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Transformer Service Manual
TRANSFORMER
LV & HV TRANSFORMER
Table of Contents
WORK INSTRUCTIONS
1. Preventive Maintenance – LV & HV Transformers
2. “A” Service Standards Where Shutdown is Not Possible
3. “A” Service Standards For Low Voltage (Dry Type) Transformers
4. “A” Service Standards For High Voltage Transformers.
5. “B” Service Standards For High Voltage Transformers
APPENDIX
1. ABB Work Instructions
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Transformer Service Manual
LV & HV TRANSFORMER
1. Preventive Maintenance – LV & HV Transformers
• All transformers are to be “A” serviced on return from all hires.
• The service standards for “A” services are detailed on the following pages for
Low Voltage 220-400-600V and High Voltage 400-15kV, 400-22kV transformers.
Wherever possible these services should be carried out in depot. However, for
long-term hires, where a shutdown is possible they should be carried out every 3
months. Where a shutdown is not possible the Area Operations Manager must be
informed and the ‘A’ service standard detailed in section 2 must be carried out. A
planned shut down should be arranged with the client to carry out a full ‘A’ Service
within the next 3 month period. Service Sticker to be affixed on the transformer
panel (switch gear area) to indicate “A” Service status.
• All appropriate precautions shall be taken to ensure that transformer has been
made DEAD before carrying out “A” service following standard Lockout and Permit
to Work Procedure.(Ref:-BOP 040)
• Only engineers who have been trained and are AAP 1,2 & 3 certified shall be
permitted to carry out “A”&”B” services on LV & MV transformers.
• All Transformers are to be “B” serviced every 12 months. If transformer is on site
for more than 12 months and a shutdown is not possible then “B”service may be
delayed (up to a maximum of 6 months) with the approval of the Area Operations
Manager in conjunction with PRODUCT MANAGER until transformer is returned
to Base or a planned shut down can be arranged with the client. Service Sticker
to be affixed on the transformer panel to indicate the service status.
• Note: Safety guidance notes as referred to in BOP/40 shall be complied with at all
times. If in doubt please contact Technical Services/Engineering group.
• In case of hermetically sealed transformers (e.g.Aggreko 3.15 MVA), oil sampling
and BDV (Break down Voltage) tests shall be carried out ONLY at Base whenever
a major repair or service is due (this is to avoid testing of oil at site which is an
uncontrolled condition / environment that leads to oil degradation and spillage.
2. “A” SERVICE STANDARDS WHERE SHUTDOWN IS NOT
POSSIBLE
2.1 Check the transformer terminal connections, tank bottom and tank top with an
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Transformer Service Manual
infrared thermometer looking for any hot spots in both HV and LV connections. If
necessary reduce the load to prevent situation from becoming worse and report
to Area Operations Manager. (Temperatures must not exceed 100°C)
2.2 Check oil level in sight glass and in the DGPT is in line with the Manufacturer`s
instructions and oil is transparent
2.3 Check the SF6 gas indication on circuit breaker shows “Green” always.
2. Monitor oil temperature at temperature gauge.(Alarm = 85° and Trip = 100°)
2.5 Advise Area Operations Manager of any discrepancies, who must then advise
further action to take.
2.6 Visually check LV terminals in circuit breakers and contactors for signs of
corrosion.
2.7 All above checks to be recorded using Transformer Service Reports (A Service
2.9kV – 20kV Transformer General Checks)
3. “A” SERVICE STANDARDS FOR LOW VOLTAGE
TRANSFORMERS
• Before commencing any work ensure transformer is DEAD and that all necessary
precautions have been taken to prevent transformer from becoming LIVE by
following Aggreko BOP.
• Discharge the transformer to earth before starting work.
• Review previous service report for any breakdowns / problems with transformer
3.1 Check link arrangement is suitable to current application (dry type only)
3.2 Check unused links are fitted at storage point (dry type only)
3.3 Check all connections for tightness
3.4 On dry type Transformers visually check winding core for damage / signs of stress
and/or burning.
3.5 Visually check container for damage
3.6 Check main connections have been fitted with nuts/bolts/washers
3.7 Check for any oil leaks
3.8 Check oil level of the transformer, at DGPT. Check physical condition of oil, it
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Transformer Service Manual
should be transparent
3.9 Check the isolator operation on 400/600v side, where applicable check for any
discoloration of leads at the isolator end
3.10 Visually check that there are no cracks on the transformer tapping, terminals
3.11 Clean transformer and container
3.12 Check fan motors, bearings. Power up and check running current and rotation
3.13 Complete checklist
3.14 Green card transformer if all above is OK
4. “A” SERVICE STANDARDS FOR 6.3MVA / 5MVA CONTAINERISED
TRANSFORMERS.
• Before commencing any work ensure transformer is DEAD and that all necessary
precautions have been taken to prevent transformer from becoming LIVE by
following standard Lockout and Permit to Work Procedure.
• Discharge the transformer to earth before starting work.
• Review previous service report for any breakdowns / problems with transformer.
4.1 BOP/040 shall be complied with at all times.
4.2 Check all door seals, bund wall, locks, roof hatch seals and hinges are fully
operational.
4.3 Carry out visual inspection of the transformer container to establish the extent of
any damage due to transport or deterioration through age.
4.4 Ensure all restraining bolts are intact and correctly fitted.
4.5 Check oil level in DGPT and sight glass for both left and right hand
transformers.
4.6 Check for any oil leaks from transformer bushings, tank, drain valves, cooling fins
and DGPT unit.
4.7 Check insulators for signs of cracking, damage, tightness and clean with dry
solvent.
4.8 Inspect HV compartment. Clean the dirt /dust from switchgear, slipover
terminations, voltage transformers and insulators.
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4.9 Check LV copper bus-bars are fitted with full complement of bolts/ nut/ washers
(M12 x 50) Guidance**
4.10 Check LV connections from transformer to isolator are sound
Guidance**(Torque Value- ).
4.11 Check mini circuit breakers at voltage transformer and the fan control supply
behind or above the doors are in good conditions.
4.12 Check circuit breaker operating handle is in good condition and is stored in
correct place.
4.13 Check operation of switchgear and isolators.(Open - Close - Open)
4.14 Visually check Fan motor bearings.
4.15 Record No Load currents before loading transformer including input voltage on
Transformer Service Report
Note: - Refer to ABB work instructions
4.16 After powering up the transformer check operation of fan motors and running
current using a Clampmeter in the Control panel wiring.
4.17 Check all container lighting and auxiliary electrical circuits are intact and
operational.
4.18 Check and ensure the battery charger voltage set to 27 volts and under voltage
level set to 18 volts.
4.19 Check all safety stickers are in place.
4.20 Check HV rubber gloves are in good condition supplied with talc powder and in
place.
4.21 Ensure all paint work is in good condition.
4.22 Prove that the protection relay trips the circuit breaker. (Refer to manufacturers
instructions for test procedure).
4.23 Complete service report and apply a service sticker on inside door to each
transformer. Green carding is applicable to depots and JA yard only.
Note:
Transformer Voltage taps and Relay settings should be confirmed with settings
in project design pack to ensure they meet the requirements of the intended
application.
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5. “B” SERVICE STANDARDS FOR 6.3MVA / 5MVA CONTAINERISED
TRANSFORMERS
• Before commencing any work ensure transformer is DEAD and that all necessary
precautions have been taken to prevent transformer from becoming LIVE by
following standard Lockout and Permit to Work Procedure.
• Discharge the transformer to earth before starting work.
• Review previous service report for any breakdowns / problems with transformer.
5.1 BOP/040 shall be complied with at all times.
5.2 Check operation of DGPT (Alarm=85°, Trip=100°, Pressure setting 0.2bar. Refer
to manufacturer’s instructions for this procedure).
5.3 Check and record relay settings. Compare with commissioning documents
5.4 Check test function of relay trip (refer to manufacturers instructions).
5.5 Prove that the protection relay trips the circuit breakers.
5.6 Prove operation of Transformer to genset intertripping, if fitted.
5.7 Conduct insulation resistance test of HV and LV windings to earth and compare
with previous results. Record on test sheet.
5.8 Check and confirm the settings of CT and VT ratio in UPM 3000/MIQ96
5.9 Carry out all items as required by ‘A’ Service..
5.10 Complete service report and apply a service sticker on inside door to each
transformer. Green carding is applicable to depots and JA yard only.
5.8 Record No Load currents before loading transformer including input voltage
5.11 Oil samples will only be taken in Jebel Ali.
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Transformer Service Manual
TRANSFORMER
11/33/66kV TRANSFORMER
Table of Contents
WORK INSTRUCTIONS
1. Service Intervals for 11/33/66kV Transformer.
2. Regular checks on 11/33/66kV transformers that are in service.
3. Tests to be done every Six months.
4. Tests to be done on a Yearly Basis
5. Storage Of Transformer Oil
6. Service Standards Where Shutdown is Not Possible
7. Oil Sampling Procedure.
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Transformer Service Manual
11/33/66kV TRANSFORMER
1. Service intervals for11/33/66kV Voltage Transformers
1.1 All 11/33/66kV transformers are to be serviced on return from all hires.
1.2 The service standards for “6.6/11/33/66kV”Transformers are detailed on the
following pages.
1.3 Wherever possible these standards should be carried out in Base. However for
long-term hires where a shutdown is possible, they must be carried out every
12 months. If a shutdown is not possible within the 12 months then the Area
Operations Manager must be informed, who may then depending on contract
duration request a planned shutdown with the client.
1.4 All appropriate precautions shall be taken to ensure that transformer has been
made DEAD before carrying out service following standard Lockout and Permit to
Work Procedure.(Ref: - BOP 040)
1.5 Only engineers who have been trained to APP1 or 2 shall be permitted to carry
out services on “6.6/11/33/66kV”HV transformers. If AAp2 engineer is not familiar
with the servicing of HV transformer, he must contact SFSM for further advice.
1.6 Note: Safety guidance notes as referred to in BOP/040 shall be complied with at
all times.If in doubt please contact Technical Services/Engineering group.
2. Regular checks on High Voltage transformers that are in service.
2.1 The following checks should be carried out on a minimum of weekly basis:
2.2 The oil and winding temperatures should be checked on an hourly basis, Especially
when the transformer is heavily loaded (full load >90%).
• Oil Temperature settings: Alarm 85°C and Trip 105°C
• Winding Temperature settings: Alarm 105°C and Trip 115°C
The OT and WT indicators are mounted on the transformer or in the control
cubicle. There are two settings on the OT and WT indicators, an alarm and a trip
setting. Additional settings on the WTI are used to start the cooling fans and oil
pumps on some of the transformers.
2.3 Operation of the Cooling fans and oil pump where fitted, the fans and pumps are
controlled by temperature and will be switched off if the temperature is below 30
– 40°C.
2.4 Visual Check for gas in the Buchholz (gas) relay.
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2.5 Check the condition of the Breather, the colour of the silica gel should be blue; in
the new type breathers the colour of dry silica gel is orange. The silica gel must
be replaced if colour changes from blue to pink or from orange to green.
2.6 Check the oil level on the side of the conservator tank. The level should be in the
middle of the gauge.
2.7 Check for any oil leaks.
2.8 Inspect cables for damage.
3. Tests to be done every Six months.
3.1 An oil sample of at least 500ml in a clean glass bottle must be taken and test the
dielectric strength.
3.2 An oil sample will be sent for dissolved gas analysis (DGA) and water content
only if the dielectric strength test fails. (See Oil sampling procedure in Section 7
of this document)
4. Tests to be done on a Yearly Basis
Note:- Test will be carried out by Specialist Support Group due to the Test
equipment required
4.1 Winding resistance
4.2 TTR (Ratio test)
4.3 PI Test – Megger test 1 minute and 10 minutes
4.4 HV Pressure test
4.5 Oil Analysis –oil sample to be sent to a lab.
4.6 Oil dielectric test, a Breakdown voltage should be higher than 30kV at 2.5mm.
4.7 Check oil and winding indicators
4.8 Check gas relay (buchholz).
4.9 Transformer test results to be logged on the test sheet and sent to Jebel Ali
Product records department and compared with previous results.
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5. Storage of Transformer Insulating oil.
5.1 The oil drums should be stored lying down with the filling plugs horizontal to the
ground. The oil drums must NOT BE STORED UPRIGHT; this is to prevent any
moisture from entering through the filling plugs. These oil drums should be stored
indoors if possible.
5.2 Oil samples must be taken from each drum and dielectric test done prior to filling
the transformer with the oil from the drums.
5.3 Note:- Guidance on typical specification EN/BS -EN IEC 60296/BS 148.
6. Service Standards Where Shutdown is not Possible
6.1 Periodically reactivate or change silica gel provided in the breather. This can be
done with the transformer on load.
6.2 Check for any oil leakage.
6.3 Monitor oil & winding temperature.
6.4 Visual inspection of terminations for wear and damage.
6.5 Check oil levels.
6.6 Do dielectric strength test every six months.
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7. Oil Sampling Procedure
7.1 Purpose:
• The purpose of oil sampling is to determine the condition of the oil in the
transformer, to build a database on the history of each transformer and to set a
standard of how it should be done.
7.2 Method:
• The oil sample of a transformer with a conservator tank must be taken from the
bottom valve of the transformer tank. The flange cover must be removed on
the sample valve, the valve must be cleaned before taking any sample. Sealed
transformers (transformers fitted in containers),need special tool for oil samples.
Drain at least 100ml into a clean dry glass or hard plastic sample container, rinse
the container with the oil and discard the oil in a safe manner, take a sample of
at least 500ml and seal the container with an air tight lid. Prolonged exposure to
direct sunlight should be avoided.
• After obtaining an oil sample, the valve should be tightened and the cover should
be fitted on the flange, care should be taken that no oil leaks from the valve and
that any spillage should be cleaned.
• Inspect the oil level of the transformer at the level indicator either at the
conservator tank or at the level indicator on top of the transformer. Topping up
of the transformer should only be done with new clean moisture free oil and is
done by filling the conservator or filling at the DGPT unit on sealed transformers
to the required level. Record the transformer details (Serial no and type)on the
container and the date when the sample was taken. The sample must be sent for
analysis.
• The results of the oil sample must be recorded in the commissioning document
before putting a transformer in service. Oil samples should be taken at least every
six months after date of commissioning due to the age and the high temperatures
of these transformers.
• All container-mounted transformers need to have their oil tested, topped up and
results recorded prior to being shipped out on a new project. The HV transformers
will have their tests done on site after erection of the transformer.
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Transformer Service Manual
TRANSFORMER
FORMS
Table of Contents
FORMS
1. “A & B” Service Report.
2. Green and Red Cards
3. Service Sticker
4. Component Change Advice Note (CCAN)
5. 11/33/66kV Transformer Test Report
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