Siemens 8DJH Series Installation And Operating Instructions Manual page 36

Description
Mode of operation
36
Principle of gas monitoring with ready-for-service indicator
a Measurement box in filled stainless-steel vessel
s
Magnetic coupling
d
Red indication: not ready for service
f
Green indication: ready for service
For the ready-for-service indicator, a gas-tight measurement box is installed on
the inside of the switchgear vessel.
A coupling magnet, which is fitted to the bottom end of the measurement box, transmits
its position to an outside armature through the non-magnetizable switchgear vessel. This
armature moves the ready-for-service indicator of the switchgear.
While changes in the gas density during the loss of gas, which are decisive for
the insulating capacity, are displayed, changes in the gas pressure dependent on
temperature and external pressure variations are not. The gas in the measurement box
has the same temperature as that in the switchgear.
The temperature effect is compensated via the same pressure change in
both gas volumes.
Revision 03 * INSTALLATION AND OPERATING INSTRUCTIONS 8DJH * 500-8067.9