MR MESSKO MPREC, Operating Instructions Manual

Page: 44 / 60

7 Operation
44 BA5789879-01 EN
If the pressure relief device has tripped, the signal pin remains in the alarm
position even when the pressure in the transformer / on-load tap-changer
has normalized again. If the micro-switches inside the housing are con-
nected, a signal is sent simultaneously to the control room.
► Once the cause has been eliminated, push the signal pin (and the sema-
phore) back down manually .
If the signal pin is in the operation position, the pressure relief device has not
tripped mechanically. If a micro-switch has, nevertheless, issued a signal,
the error can lie in the tripping circuit, see Tripping circuit malfunction
[
► Section 9.1, Page 47].
7.2 Venting the pressure relief device
When mounted vertically, no gas collects below the valve plate. Venting is
therefore not necessary.
When mounted horizontally, venting the pressure relief device is only neces-
sary if this is recommended by the transformer / on-load tap-changer manu-
facturer.
WARNING
Danger of explosion!
Explosive gases in the pressure relief device, in the trans-
former or under the on-load tap-changer head cover can blow
out or explode and thus lead to death or serious injury.
► Ensure that there are no ignition sources such as naked flames, hot sur-
faces or sparks (e.g. caused by the build-up of static charge) in the im-
mediate surroundings and that none occur.
► De-energize all auxiliary circuits (e.g tap-change supervisory device,
pressure relief device, pressure monitoring device) before opening the
pressure relief device.
► Do not operate any electrical devices during the work (e.g. risk of sparks
from impact wrench).
To vent the pressure relief device after filling the transformer / on-load tap-
changer, proceed as follows:
1. Refer to the transformer / on-load tap-changer operating instructions and
only vent the pressure relief device if recommended by the transformer /
on-load tap-changer manufacturer.