Breaker and a half vs. main tie main 2

[gregnola]

I have worked in the petrochem industry for a while where a double ended main-tie-main system is very common. Now that I am on a power job I keep hearing breaker and a half scheme. The two seem similar but could someone tell me the difference between a breaker and half scheme and a double ended main-tie-main system?

 

[davidbeach]

The breaker and a half scheme would be like the M-T-M scheme if you have only one load per side of the M-T-M and no feeder breakers. Three breakers & two loads = 1 1/2 breakers per feeder.

 

[gregnola]

Thank you! That makes sense

 

[alehman]

It's commonly operated with all three breakers closed so a trip requires opening two breakers. Multiple sets of 3/2 can be applied between two source buses.

 

[cuky2000]

See the enclose site showing a typical simplify layout and one Line Diagram for a breaker 11/2 configuration.

http://cuky2000.250free.com/Swyard1.jpg

See also the enclose site for additional information describing advantages and disadvantages of the Bkr 11/2 substation configuration

http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-3006/c-5.pdf

 

[alehman]

Cuky always has great stuff..