MR VACUTAP VM-Ex, Installation And Commissioning Instructions

Page: 123 / 210

5 Mounting
Maschinenfabrik Reinhausen GmbH 2020 123 5293079/01 EN VACUTAP
®
VM-Ex
5.4.8.1 Vacuum-drying in the transformer tank
The on-load tap-changer head cover remains closed during the entire drying
process.
1. Establish a connecting lead between either connections E2 and Q or con-
nections E2 and R on the on-load tap-changer head.
2. Seal off unused pipe connections with a suitable blank cover.
Figure 133: Connecting lead
Vacuum-drying in the transformer tank
1. Heat up the on-load tap-changer in air at atmospheric pressure with a
temperature increase of approximately 10 °C/h to a final temperature of
maximum 110 °C.
2. Pre-dry the on-load tap-changer in circulating air at a maximum tempera-
ture of 110 °C for a period of at least 20 hours.
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.
If you wish to perform another transformer ratio test after drying, proceed as
described in the section "Performing transformer ratio test following dry-
ing" [
► Section 5.4.10, Page 137].
5.4.8.2 Vapor-phase drying in the transformer tank
If you have opened the kerosene drain plug already (e.g. after the trans-
former ratio test), you can begin the drying [
► Section 5.4.8.2.4, Page 134]
right away.
Otherwise, you first have to open the kerosene drain plug before you can be-
gin the drying.