The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:

2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Safety at heights?
by HotLine1
Yesterday at 08:51 PM
International Wire Colour Codes
by Texas_Ranger
Yesterday at 03:29 PM
Looking for older post
by Texas_Ranger
Yesterday at 03:22 PM
Last time to chat here
by Trumpy
01/20/17 11:41 PM
Unsafe Situations
by Trumpy
01/20/17 09:46 PM
New in the Gallery:
Desk-mounted "power-board"
Shout Box

Top Posters (30 Days)
Admin 35
HotLine1 20
Ruben Rocha 17
gfretwell 16
Trumpy 15
Who's Online
0 registered (), 74 Guests and 11 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#28809 - 08/31/03 11:49 AM tie breakers
Eandrew Offline
Member

Registered: 05/24/02
Posts: 69
Loc: seattle, wa, usa
does anyone know the purpose of tie breakers in switchgear.

Lets say you have a 4000 amp tie breaker ( with a spring loaded handle) between two 3000 amp switchboard panels (each 3000 amp switchboard section housing about 600 amp feeder breakers. Why is this tie breaker connected via copper bussing in the switchgear necessary?

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#28810 - 08/31/03 12:56 PM Re: tie breakers
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
It is likely that the fault duty is too high for insulated cables to withstand without damage. Properly braced busbars may have been specified particularly for the increased fault current when the tie breaker is closed. The fault duty effectively doubles in that situation—with three breakers closed, two transformers are then operating “in parallel”.




[This message has been edited by Bjarney (edited 08-31-2003).]

Top
#28811 - 08/31/03 05:59 PM Re: tie breakers
Ron Offline
Member

Registered: 03/13/02
Posts: 577
Loc: White Plains, NY
Main-tie-main switchgear is very common in critical facilities. Depending on the application, each of the mains is designed to carry half of the total swgr load on a normal day. In the event of a failure of one source, the main breaker on the "bad" source is opened, then the tie is closed for the "good" main to carry the full load of the SWGR.
Sometimes I design in a main-tie-tie-main. This allows maintenance access to either side of the tie without any live bus to contend with.
_________________________
Ron

Top
#28812 - 08/31/03 08:51 PM Re: tie breakers
Winchester EE Offline
Junior Member

Registered: 08/16/03
Posts: 9
Loc: St. Louis
In the 8 years I've been with my current company, we have used our tie breakers more than once. I think they are a good investment for a company.

We melt copper in large induction furnaces which will "freeze up" if you leave power off for too long. When a main lead blows off the 34Kv, we can tie into a secondary incoming line.
_________________________
Please buy American made Winchester ammunition! Business is slowly going overseas!

Top
#28813 - 09/02/03 04:47 AM Re: tie breakers
fireftr Offline
Member

Registered: 01/16/02
Posts: 17
Loc: Bucyrus Ohio Usa
At my plant we have 6 indoor substations that we can tie together in case of a xfmr failure in one of them. We have used it a couple times here in the last few years after a xfmr failure. We also use the Kirk key sytem to avoid any kind of mix up when tying subs together.

Top


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals