ABB VUBB, Installation And Commissioning Manual

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Installation and commissioning guide
1ZSC000562-AAK EN, REV. 2, 2019-07-03
5.2 Drying processes
5.2.1 Overview
Dry the tap-changer with the transformer as a unit. The unit can be dried one of with these two processes:
• Vapor phase process
• Alternating hot air and vacuum process
CAUTION!
Do not operate the tap-changers mechanism after the drying process has started. Operation of the
mechanism without lubrication will cause damage to the tap-changer.
5.2.2 Drying with the alternating hot air and vacuum process
Overview
Make sure that both the pressure, and temperature are less than the maximum permitted values during the
drying process.
Maximum permitted Value Note
Pressure difference 100 kPa Between the transformer tank and
the tap-changer.
Temperature 135 °C -
Procedure
1. Do the drying process.
End of instruction
5.2.3 Drying with the vapor phase process
Overview
Make sure that both the pressure, and temperature are less than the maximum permitted during the drying
process.
Maximum permitted Value Note
Pressure difference 100 kPa Between the transformer tank and
the tap-changer.
Temperature 135 °C -