Racking Breakers

[Mr. Pickle]

I have seen in a few Wastewater Treatment facilities, where they have large racking breakers. The voltage system is always 480V,3-phase. I can't figure out why these would be used with this voltage system.

Yesterday I went into a plant, in addition to racking breakers they had SEL devices for the service main and a generator breaker. Any idea to why these SEL devices where used for a 480V system?

My guess is that there was/is an engineering in the area that would design plants this way. Typically it seems when they are used the services is 2000A or greater. Any input to why these strategies would be a good idea and better than more typical switchgear/distribution gear?

 

[jim dungar]

Among other things racking style breaker allow for reduced downtime when performing maintenance.

Relays can provide protection against things like low voltage or reverse current flow. They can also perform automatic throw over and generator control.

 

[Todd0x1]

Some thoughts: It's a public utility project and designed by engineers who design public utility projects, who use things like SEL products and draw out breakers. Project is likely designed to last much longer than a typical commercial project. There's also the ability to keep spare breakers onsite and rotate them for breakers undergoing maintenance. SEL devices for the highest quality monitoring and protection.

For the system responsible to treating sewage I would much rather see a room full of draw out switchgear and SEL relays than a rusty 3r switchboard outside full of pringle switches.

 

[Jraef]

The tree main reasons for using switchgear (defined as being draw-out) vs switchboards (fixed mount) are to isolate faults in the individual cells to prevent collateral damage, service and maintain the breakers without having to de-energize the entire lineup, and provide higher fault tolerance so that faults can have time to clear at the protective device closest to the fault rather than take out a large section of (or the entire) facility. In turd farms, unexpected shutdowns cause massive cleanups and fines, so the higher cost of better equipment is a pittance in comparison.

 

[masterinbama]

The tree main reasons for using switchgear (defined as being draw-out) vs switchboards (fixed mount) are to isolate faults in the individual cells to prevent collateral damage, service and maintain the breakers without having to de-energize the entire lineup, and provide higher fault tolerance so that faults can have time to clear at the protective device closest to the fault rather than take out a large section of (or the entire) facility. In turd farms, unexpected shutdowns cause massive cleanups and fines, so the higher cost of better equipment is a pittance in comparison.

Having worked on both fresh water and wastewater facilities, redundancy and backup to redundancy to backup is critical.