5 Mounting
Maschinenfabrik Reinhausen GmbH 2020
79
5293079/01 EN
VACUTAP
®
VM-Ex
2. Seal off unused pipe connections with a suitable blank cover.
Figure 71: Shared lead
Vapor-phase drying in the transformer tank
1. Supply kerosene vapor at a temperature of around 90°C. Keep this tem-
perature constant for 3 to 4 hours.
2. Increase the kerosene vapor temperature by approx. 10°C/hour to the de-
sired final temperature of max. 125°C at the on-load tap-changer.
3. Vacuum-dry on-load tap-changer at between 105°C and maximum 125°C
for at least 50 hours.
4. Residual pressure of no more than 10
-3
bar.
5.3.7.2.5 Closing kerosene drain plug
NOTICE
Damage to the on-load tap-changer!
Moisture in the oil compartment reduces the dielectric strength of the insu-
lating fluid and thus leads to damage to the on-load tap-changer.
► Within 10 hours of drying, seal off oil compartment with on-load tap-
changer head cover.
1. Remove [
Section 5.3.7.2.1, Page 67] the diverter switch insert.
2.
NOTICE!
An open kerosene drain plug leads to insulating fluid escaping
from the oil compartment and therefore to damage to the on-load tap-
changer. Close kerosene drain plug by turning clockwise with extended
socket wrench (tightening torque 20 Nm).
3. Insert [
Section 5.3.7.2.3, Page 73] the diverter switch insert.
If you wish to perform another transformer ratio test after drying, proceed as
described in the section "Performing transformer ratio test following dry-
ing" [
