Further to our previous blogs for site instructions now we are giving some details about schedule for maintenance which will be helpful for site personal to take care the installed transformers.


 
RECOMMENDED MAINTENANCE SCHEDULE:
 
The hourly and daily inspection recommended is applicable for attended substations only.  However, for unattended substations these items should be inspected as frequently as possible. 

Sl. No.
Inspection

Frequency

Items to be inspected

Inspection Notes
Action required if inspection shows unsatisfactory conditions
1
Monthly
i.  Oil level in transformer
ii.  Connections
iii. Loading cycle
Check transformer
Oil level
Check tightness
Check if more than rated
If low, top up with dry oil.  Examine transformer for leaks
If loose, tighten
2
Quarterly
i. Bushings
Examine for cracks and dirt deposits.
Clean or replace
3
Half-yearly
Gasketted Joints, Gauges and General Paint Work
Check of moisture under cover inspects.
 Improve ventilation, check oil.
4
Yearly
i.  Oil in transformer
ii.  Oil in tap changer, if provided
iii. Connections
iv. Breather
Check for dielectric
Strength and water content.  Check for acidity and sludge.
           
             —
Colour of silica gel
Take suitable action to restore quality of oil.
Take suitable actions if earth resistance is high
If colour of silica gel is observed from blue to pink, silica gel shall be replaced.
5
5 Yearly
For large power transformers, check oil for DGA
          —-
—–
6
Occasionally
For fiber optic sensor
Signal strength
Clean through kit

TROUBLE SHOOTING CHART
 
Faults observed during the periodic maintenance schedules are to be rectified as per the suggested action required.  However, certain chance troubles and major faults in performance of the transformer shall have to be attended to in a desired sequence, as per manufacturer’s instructions (or) ready reference manuals.  Guidance to manage electrical and mechanical troubles normally encountered in all types of transformers are provided as follows:

Trouble Shooting
(1)
Cause
(2)
Remedy
(3)
Rise in temperature/
High temperature
Winding & oil
Over Load
If possible, reduce load.  Heating can often be reduced by improving power
Factor of load.  
Insufficient Cooling
1. Check if all the radiator valves are      open
2. If unit is forced cooled, make sure fans are functioning.
Sludged oil
Use filter press to wash off core and coils.  Filter oil to remove sludge.
Audio Noise
Leaky gaskets and joints.  Accessories and external transformer parts are set into resonant
Make certain all joints are tight.  Tighten loose parts.  In some cases parts may be stressed into resonant state.  Releasing pressure and shimming will remedy this condition.
Fractured metal or porcelain parts of bushings
Unusual strains placed on terminal connections
Cables and bus-bars attached to transformer terminals should be adequately supported.  In the case of heavy leads, flexible connections should be provided to remove strain on the terminal and bushing porcelain.
 Gases and Buchholz Relays
Due to incipient fault
Action required according DGA analysis
Oil level
Due to leakages or pilferage in gasket and welded joints
Cause of leakages to be checked and proper action to be taken
 
In case any enquiry free feel to contact us at info@saielectricals.com or gaurav.jain@saielectricals.com