Annex 1
Preventive Maintenance Schedule for Transformers and Reactors
|
S. No. |
Tasks assigned |
Shut Down
(SD) Or |
Periodicity |
|
a. |
Checking of bushing oil level |
WSD |
Monthly |
|
b. |
Checking of oil level in Conservator |
WSD |
Monthly |
|
c. |
Checking of oil level in OLTC Conservator |
WSD |
Monthly |
|
d. |
Checking of cooler oil pumps and fans |
|
|
|
|
i) Manual actuation |
WSD |
Monthly |
|
|
ii) Auto Starting |
SD |
Yearly |
|
e. |
Checking of oil leaks |
WSD |
Monthly |
|
f. |
Checking condition of Silicagel in breather and regeneration if required |
WSD |
Monthly |
|
g. |
Measurement of BDV of oil |
WSD |
Half Yearly |
|
h. |
Testing of oil for DGA and other oil parameters |
WSD |
Half Yearly |
|
i. |
Checking/Topping up of oil level in oil seal of breather |
WSD |
In case of requirement |
|
j. |
Vibration measurements (for Shunt Reactors only) |
WSD |
Half Yearly |
|
k. |
Measurement of BDV of OLTC oil |
SD |
Yearly |
|
l. |
Tand measurement for Bushings |
SD |
Yearly |
|
m. |
i) IR! measurement of Windings (Polarisation Index and DA+ Ratio) |
SD |
In 3 Years** |
|
|
ii) Tand measurement of Windings |
SD |
In 3 Years** |
|
|
iii) Measurement of Windings resistance |
SD |
In 3 Years** |
|
|
iv) Measurement of windings ratio |
SD |
In case of requirement |
|
|
v) Measurement of short circuit Impedance |
SD |
In case of requirement |
|
n. |
External cleaning of Radiators |
SD |
Yearly |
|
o. |
Cleaning of all Bushings |
SD |
Yearly |
|
p. |
Frequency Response Analysis |
SD |
In case of requirement |
|
q. |
Maintenance of OLTC driving mechanism |
SD |
Yearly |
|
r. |
Checking of all remote indications (STI and Tap position indicator) |
SD |
Yearly |
|
s. |
Electrical checking / testing of pressure relief device, Buchholz relay, OLTC surge Relay and checking/Replacement of the gaskets of the terminal box |
SD |
Yearly |
|
t. |
Checking/testing of Buchholz relay by injecting air or nitrogen |
SD |
Yearly |
|
u. |
Marshalling boxes of ICT/Reactor of: |
SD |
Yearly |
|
|
i) Cleaning of Marshalling boxes of ICT/Reactor and OLTC |
SD |
Yearly |
|
|
ii) Tightening of terminations |
SD |
Yearly |
|
|
iii) Checking of contactors, space heaters, illumination etc. |
SD |
Yearly |
|
v. |
Checking and Cleaning of Diverter Contacts |
SD |
SOS (50, 000 Operations) |
|
w. |
Checking of oil level and calibration of OTI, WTI |
SD |
Yearly |
|
x. |
Filteration /Replacement of Oil of OLTC |
SD |
In case of requirement |
|
y. |
Filteration / Degassing of main tank radiator oil |
SD |
In case of requirement |
|
z. |
Testing of bushing CTs. |
|
|
|
|
i) IR valve |
SD |
SOS |
*Water content, BDV, SP, Resistance, Tand, IFT. Total Acidity, 2-Furfuraldehyde etc.
**First time after one year from commissioning and then once in every three years.
+Di-electric Absorption Ratio
!To be measured as per the following combinations:
N/E, N/LV and LV/E.