45
Procedure Time Check Method
Oil level gauge
Every three
weeks:
Check the oil level. Register variations in the oil level,
taking into account the level change due to changes in
the oil temperature.
Yearly
• Clean the mask.
• Fill of mineral oil for transformer, in case the level is
under the normal level for a 25° C temperature or
smaller.
Insulating liquid Yearly
In order to continuously monitor the transformer and
detect and prevent possible failures it must be done at
least once a year the next test:
• DGA Dissolved gas analysis (ANSI C57-104)
• Dielectric Strength (ASTM D-1816)
• Water content (ASTM D-1533)
For more information, please refer to ANSI C57-106
standard (current version)
Temperature Values
The transformer is usually designed to operate continually to 100% of load to a temperature
ambient average of 30° C (to above sea level indicated in the nameplate). The winding
hottest spot temperature will be, in general, 15°C bigger than the oil temperature.
Example: For a transformer with a 55° C of temperature over-elevation indicated in the
nameplate:
table 9-1 Nameplate
Name
Temperature
T. Ambient = 26°C
T. Oil (nominal load) = 74°C
T. Honest spot = 86°C
So it can be inferred that the transformer is operating normally, because the oil temperature
is smaller than the permissible of 85°C (30 °C of ambient temperature plus 55°C of oil over-
elevation). The hottest spot temperature must not be higher than 105° C, so an 86° C
temperature is acceptable.
User Manual 9 Transformer Maintenance Guide
To Next Page
Loading...
Need help?
General