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Application of SF6 switches

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birddogger

Electrical
Feb 23, 2004
31
I see frequent talk in this forum about SF6 switches and how they’re primarily used in Europe. I’ve worked on projects here in the States where we’ve specified them, but it always has to do with space and cable routing issues. The SF6 switches (as I know them anyway) are wider than they are tall, sit off the floor about 18” or so on legs, and the cables terminate on the front of the gear with some sort of elbow joint (please inform me of the proper term for these terminations if you know). This allows MV conductors with large bending radii to have enough room to sweep down from above (or below), since the terminations are at a lower elevation than for standard 90” tall gear.

Is this just a manufacturing standard for this particular company’s SF6 switch, or all they all made this way? Why is this low-profile arrangement only found on SF6 switches and not other types of air-break, vacuum-break, or other switches?
 
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One term for them is 'IEEE 386' connectors.

Air-insulated gear is larger for equal BILs. There is low-profile airbreak gear, like that from S&C Electric.
 
Hi birddogger,

Your explanation typicaly reffers to RMU (ring main units) type switchgear. What you say about them generaly is valid for all manufactures. In some cases strait cable terminations are applicable, same technology is used as in 90° MV cable termination plug.
Why you can't have the same compact design in air insulated switchgear, you simply need more space to achieve the same insulation level.
Why not vacuum, simply because these RMU are designed in one compartement containing all functions (interupter, earthing switch,coupler...). If you would try to achieve the same in vacuum the tank would collapse under the pressure of the surrounding eviroment.

I hope this provides some answers for you...

kind regards,

Danny
 
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There is an increasing demand for GIS in substations from the standpoint of site-acquisition difficulties and environmental harmony. In keeping with this tendency, GIS connection-type transformers are ever-increasing in their applications. At Toshiba, the SF6 gas bus is connected directly with the transformer coil terminal through an oil-gas bushing. Toshiba's oil-gas bushing support is composed of a transformer-side flange and an SF6 gas bus-side flange, permitting the oil side and the gas side to be completely separated from each other.
 
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