4160 Volt Gas, Air, or Oil Insulated Equipment

[steve66]

Could someone explain the advantages or disadvantages of using gas, air, or oil insulated equipment at 4160 volts?

Thanks.

 

[zog]

Forget about Oil for 4160, been 50 years since anyone made those and the ones that were made have mostly been replaced.

I have never seen a GCB in 4160V.

Air or Vacuum should be the decision. VCB's (As compared to Air) are generally more relaible, lighter, and have higher AIC's than air (In general). They also require less maintenence, the most common failure is the bottles, which are expensive to replace when they do fail.

 

[steve66]

So are the gas enclosed switches and breakers mostly used on higher voltages, like 15KV?

Steve

 

[rcwilson]

So are the gas enclosed switches and breakers mostly used on higher voltages, like 15KV?

Steve

Steve- Gas Insulated Switchgear (GIS) at 15 kV is expensive and does not save much space. At 27kV and above, the higher cost is offset by the smaller footprint. One supplier offers 15-42 kV SF6 insulated gear in 24? wide x 64? deep enclosures.

Another benefit comes from each phase being in a separate "pipe" enclosure, which is considered by some as a zero arc flash hazard design. All energized components are enclosed in pressure vessels filled with insulating gas. A phase-phase fault is impossible and phase-ground faults can only occur inside the pipe.
At lower voltages (<42kV) a vacuum bottle circuit breaker interrupter is used, surrounded by insulating SF6 gas. That avoids the production of SF6 byproducts from arcing.

Some owners are using the 38 kV gear at 15 kV because of the arc flash benefits and the decreased maintenance costs (20-year maintenance cycle, if manufacturer literature is believable.)

If you?re interested check out ABB, Siemens, AREAVA, Hyundai and other websites.

 

[jdsmith]

Steve- Gas Insulated Switchgear (GIS) at 15 kV is expensive and does not save much space. At 27kV and above, the higher cost is offset by the smaller footprint. One supplier offers 15-42 kV SF6 insulated gear in 24” wide x 64” deep enclosures.

Another benefit comes from each phase being in a separate "pipe" enclosure, which is considered by some as a zero arc flash hazard design. All energized components are enclosed in pressure vessels filled with insulating gas. A phase-phase fault is impossible and phase-ground faults can only occur inside the pipe.
At lower voltages (<42kV) a vacuum bottle circuit breaker interrupter is used, surrounded by insulating SF6 gas. That avoids the production of SF6 byproducts from arcing.

Some owners are using the 38 kV gear at 15 kV because of the arc flash benefits and the decreased maintenance costs (20-year maintenance cycle, if manufacturer literature is believable.)

If you’re interested check out ABB, Siemens, AREAVA, Hyundai and other websites.

We have two lineups of Powell 38 kV arc-resistant switchgear that are very large - 2000 A bus, sections are 42" wide x 10' 6" deep x about 11 ft high with the plenum. The nice thing about this switchgear is that it is a supersized version of other MV vacuum gear. It has required very little training for our substation-qualified electricians to learn to operate and maintain the gear.

We are investigating options for a new main sub at 34.5 kV. Powell is developing 3000A 38 kV arc-resistant gear, and we've done some preliminary investigation into the so-called 38 kV gas insulated switchgear. I say so-called because the interrupter is still a vacuum bottle and the primary insulation medium can be air in the worst case. The SF6 gas is used to establish the BIL rating - I think something like 25-30 psi provides 200 kV BIL. I believe 0 psi of SF6 provides 140 kV or so of BIL. Make sure you physically inspect a demo unit before specifying or buying any of the arc-resistant gear. As far as the claims of arc resistance and isolated phases being more fault resistant, that all depends on your relaying scheme and 3 phase vs. single phase available short circuit current. Even if the system is safer on paper, whoever if writing operating and safety procedures for the owner may not agree and you may not get the anticipated benefit. I shouldn't say more than that on a forum, but feel free to PM me if you want more information or some of the caveats to watch out for.