Eaton RVAC - Chapter 5 Operation, Maintenance and Repair; Pre-Operation Checks and Notices; SF6 Gas Management and Safety

Instruction Leaflet IL0102002E
Effective April 2018
Ring Main Unit Operation Instruction
30 EATON CORPORATION www.eaton.com
Chapter 5 Operation, maintenance
and repair
WARNING
THE OPERATION, MAINTENANCE AND REPAIR OF THE PRODUCT SHALL
BE CONDUCTED ONLY BY PROPERLY TRAINED PROFESSIONAL STAFF.
1.1. Inspection prior to operation
1. Notice for operations
The RMU can be put into operation right after the completion of
installation and commissioning. Check the mechanisms
completely before running to see whether each functional circuit
switch is in open position, whether the voltage presence display is
normal, whether the indications are indicating correctly, whether
the interlocking mechanism is operating properly, whether the
pressure meter indication is at the rated pressure, whether the
fuse is installed in the combination unit circuit. Properly lubricate
the drive parts, and tighten the loose nuts and screws.
1.2. SF6 gas control and supervision
Pure SF6 gas is colorless, tasteless, non-toxic, and not easy to be
noticed. However, SF6 gas will deposit in the lower part of the
area, because SF6 gas has bigger density than the air. When the
density of SF6 in the air exceeds a certain amount, SF6 can make
people suffocate. Therefore, before the staff goes into the
installation site, especially into low-lying places such as the
basement and the cable trench, the place must be ventilated, and
the oxygen concentration in the air shall be detected. Only when
the oxygen concentration is greater than 18%, the work shall be
started. From the perspective of environmental protection and
safety, the concentration of SF6 in the air should not exceed 1000
PPM.
The SF6 gas should maintain a certain density within the
enclosure. A certain amount of gas shall be released when the
density of use exceeds the upper limit. A certain amount of gas
shall be filled when the density of use is lower than the lower
limit. The RMU uses a pressure meter to check the SF6 gas inside
the enclosure, while the SF6 gases of same density offer different
pressures at different temperatures, the curve as shown in Figure
19.
Figure 19 Pressure curve according to gas density and temperature change