Drying Processes; Overview; Drying With The Alternating Hot Air And Vacuum Process; Drying With The Vapor Phase Process - ABB VUBB Installation And Commissioning Manual

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
Pressure difference
Temperature
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
Pressure difference
Temperature
30
Value
100 kPa
135 °C
Value
100 kPa
135 °C
Note
Between the transformer tank and
the tap-changer.
-
Note
Between the transformer tank and
the tap-changer.
-
Installation and commissioning guide
1ZSC000562-AAK EN, REV. 2, 2019-07-03