Main Tie Main Switchgear Replacement

[anbm]

Main(M1 ) - Tie(T1) - Main(M2) - Tie(T2) - Main(M3) - Tie(T3) - Main(M4) - Tie(T4) - Main(M5)

M1, M2, M4 and M5 - each is fed from dedicated transformer (480V/3PH secondary)

The client wanted to replace all switchgear with new due to the gear is 40 - 50 years old and does not have latest technology.

Can each section be replaced one at a time to minimize power downtime? i.e. Option #1 or has to be either option 2, 3,4?

Option #1
M1
T1
M2
T2
M3
T3
M4
T4
M5

or
Option #2
M1-T1
M2
T2-M3-T3
M4-T4
M5

or
Option #3
M1-T1
M2-T2-M3-T3
M4-T4
M5

or
Option #4
M1-T1-M2
T2-M3-T3
M4-T4-M5

 

[jim dungar]

Individual breakers may be able to be upgraded/rebuilt, but it is not likely the existing gear can be removed full sections at a time. Each breaker section will always contain energized bussing unless the breakers on both sides are opened.

Do you have accurate drawings of the internal wiring and bussing?

 

[ron]

The single tie between SWGR lineups means that an Electrician may not work adjacent to the tie because they would have exposure to the energized side. You would need to confirm the isolation that may be provided by the construction of the tie SWGR section.

As mentioned by Jim, you might be better to have a certified company recondition the SWGR by replacing the breakers with modern versions fitting in the same cradles. See NEC 408.8(B) (2020 and later)

 

[zbang]

Does the client want to minimize total downtime or the duration of an/each outage? By that I mean whether five or six 8 hour outages. or a single 24-36 hour outage, is more desirable. (I made up those numbers, but it gets the point across.)

Or- It might make sense to replace the entire switchboard at once instead of in pieces. That said, everything inside requires occasional checking and cleaning, and I don't think bus-bars themselves have an EOL (stabs might), so replacing/reconditioning the breakers/etc might be the way to go.

 

[anbm]

They use rental generator to feed downstream loads of each gear section while removing and replacing that particular gear section. Try to minimize generator runtime.

 

[anbm]

Individual breakers may be able to be upgraded/rebuilt, but it is not likely the existing gear can be removed full sections at a time. Each breaker section will always contain energized bussing unless the breakers on both sides are opened.

Do you have accurate drawings of the internal wiring and bussing?

No

 

[jim dungar]

No

Chose your contractor early, they need to be part of your design team.