MTM Gear

[anbm]

Kind of field question, for the MTM (Main Tie Main) gear, 480V, if the owner wants to replace the old MTM gear with new one,
can left M, T sections + their distribution sections be disconnected any removed from site first, then left M and its distribution
section be removed later or the whole package (MTM) must be disconnected and removed together?

 

[ron]

You can do whatever you want, but working energized and what can the building tolerate during the work regarding outages will affect what you do.

 

[jim dungar]

If you make the new gear M-T-T-M you would need one complete outage to disconnect the first set of gear, but opening both ties might allow you to replace the second half without a full outage. It also makes future maintenance safer.

 

[anbm]

If you make the new gear M-T-T-M you would need one complete outage to disconnect the first set of gear, but opening both ties might allow you to replace the second half without a full outage. It also makes future maintenance safer.

do you know if the old gear will be disconnected and removed from front or rear?

 

[JoeStillman]

If you make the new gear M-T-T-M you would need one complete outage to disconnect the first set of gear, but opening both ties might allow you to replace the second half without a full outage. It also makes future maintenance safer.

Rather than a second tie breaker, couldn't you just build the first new section with a bus-transition cubicle between the tie and the second section? With the tie open in one cubicle, the bus-transition cubicle would be fully de-energized where you bolt on the second new section.

 

[jim dungar]

Rather than a second tie breaker, couldn't you just build the first new section with a bus-transition cubicle between the tie and the second section? With the tie open in one cubicle, the bus-transition cubicle would be fully de-energized where you bolt on the second new section.

But during normal operation the tie breaker cubicle always has some energized components making maintenace an NFPA70E complicance concern. A M-T-T-M eliminates this issue. Only one of the T devices needs to be an OCPD.