Outdoor Ring Main Unit SF6

General of Outdoor Ring Main Unit

OMR is a ring main unit for the secondary distribution network. OMR can be supplied in 10 different configurations suitable for most switching applications in 12/24 kV distribution networks. The Unit can be mounted to the smallest distribution transformer or be sited in a free standing format. It is extendable and combined with DONGFU own developed technology concept, which is flexible, modular compact switchgear, they represent a complete solution for 12/24 kV secondary distribution networks. OMR have identical user interfaces.

OMR is a completely sealed system with a stainless steel tank containing all live parts and switching functions. A sealed steel tank with constant atmospheric conditions ensures a high level of reliability as well as personnel safety and a virtually maintenance-free system. The OMR concept offers a choice of either switch-fuse combination or circuit-breaker with relay for protection of the transformer. OMR can be supplied with an integrated remote control and monitoring unit.

This product is in conformity with the standards:

IEC62271-200, IEC60420, GB/T11022, GB3804,GB3906

Service Environment of Outdoor Ring Main Unit

a) Air temperature: Maximum temperature: +45 ℃ ; Minimum temperature: -20 ℃

b) Humidity: Monthly average humidity 95%; Daily average humidity 90% .

c) Maximum installation altitude: 2500m

d) Ambient air not apparently polluted by corrosive and flammable gas, vapor etc.

e) No frequent violent shake

Enclosure

OMR use SF6 – gas (Sulphur hexafluoride) as insulation and quenching medium. The SF6 is contained in a welded stainless steel tank, which is sealed for life.The pressure system is defined as a sealed for life system with an operating life time exceeding 30 years. The leakage rate is less than 0,1% per year. In order to ensure a reliable and tight welding, all welding work is carried out by computer controlled robots. Electrical and mechanical bushings penetrating the tank are clamped and sealed to the tank by high quality O-rings. The mechanical bushing has in addition a rotating shaft which connects the shaft of the switch to the corresponding shaft of the mechanism. The rotating shaft is sealed by a double set of gas seals. All SF6-tanks have to pass a leakage test before gas filling. Leakage test and gas filling are done inside a vacuum chamber. The first step in the leakage test is to evacuate all air inside both SF6-tank and vacuum chamber simultaneously. Then the SF6-tank is filled with Helium. Due to the characteristics of Helium, this test will detect all possible leakages. If the SF6-tank passes this test, the Helium will be evacuated and replaced by SF6. The SF6-tank has a degree of protection of IP67 and can be immersed into water and still maintain all functions in a satisfactory way.

Technical Data Sheet

Internal Structure