Page 1 of 5 123 ... LastLast
Results 1 to 10 of 48

Thread: Fuses vs Circuit breakers in switch gear

  1. #1
    Join Date
    Jan 2011
    Location
    United States
    Posts
    7,427

    Fuses vs Circuit breakers in switch gear

    What are the advantages and disadvantages of using fuses over circuit breakers in 13.8kv switch gear? How much maintenance, and what type of maintenance do fuses require? In so far I see many compelling reasons to use fuses in place of breakers where maintenance and inspection is infrequent. Here is one reason as an example:



    https://www.sandc.com/globalassets/s...nt-621-r69.pdf


    Cost is also less. Is it to good to be true? Most stuff I have evaluated have used breakers so I am not to familiar with fuses outside of fused cutouts on poles.
    I'm in over my head...

  2. #2
    Join Date
    Feb 2005
    Location
    Charlotte, NC
    Posts
    6,768
    MV Fuses are expensive and have to be replaced every time they interrupt a fault, breaker can just be reset. Breakers can be operated remotely and can tripped for other reasons than just overcurrent (Freq, UV, etc...). I really depends on the application as to which is the better choice.

  3. #3
    Join Date
    Jan 2011
    Location
    United States
    Posts
    7,427
    Quote Originally Posted by zog View Post
    MV Fuses are expensive and have to be replaced every time they interrupt a fault, breaker can just be reset. Breakers can be operated remotely and can tripped for other reasons than just overcurrent (Freq, UV, etc...). I really depends on the application as to which is the better choice.


    How much do fuses cost as compared to that saved on having them? My (thin) understanding are that breakers cost much more upfront.
    I'm in over my head...

  4. #4
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    16,789
    Quote Originally Posted by mbrooke View Post
    How much do fuses cost as compared to that saved on having them? My (thin) understanding are that breakers cost much more upfront.
    I don't know much about MV costs but I have found that for 600V and under fuses are usually only cost effective <200A. Depending on AIC requirements MCCB are often cost effective at ratings as low as 100 A.
    Bob

  5. #5
    Join Date
    Jan 2011
    Location
    United States
    Posts
    7,427
    Quote Originally Posted by petersonra View Post
    I don't know much about MV costs but I have found that for 600V and under fuses are usually only cost effective <200A. Depending on AIC requirements MCCB are often cost effective at ratings as low as 100 A.
    Cost in equipment of cost of the fuses themselves?
    I'm in over my head...

  6. #6
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    16,789
    Quote Originally Posted by mbrooke View Post
    Cost in equipment of cost of the fuses themselves?
    total cost of one option versus another.

    I only design industrial control panels.

    The cost of a 400A fuseblock, 3 400A fuses, and the extra space they take up over a 400A MCCB adds up.

    There is also the issue of being able to use the MCCB as a disconnecting means which is not possible with a fuse block. It requires a seperate switch which are quite pricey over 200A and eat up a lot of space.

    Also, all the major MCCB manufacturers have distribution lugs so you can get rid of distribution blocks if it is a feeder. Bussman has some fuse blocks that have the same feature but they are only recognized so we had to pay UL to get them added to our procedure.

    Incidentally, I have found it is often more cost effective to buy an extra MCCB with distribution lugs in lieu of a distribution block because most distribution blocks have issues with SCCR ratings and require fuses to get much of a rating.
    Bob

  7. #7
    Join Date
    Jan 2011
    Location
    United States
    Posts
    7,427
    Quote Originally Posted by petersonra View Post
    total cost of one option versus another.

    I only design industrial control panels.

    The cost of a 400A fuseblock, 3 400A fuses, and the extra space they take up over a 400A MCCB adds up.

    There is also the issue of being able to use the MCCB as a disconnecting means which is not possible with a fuse block. It requires a seperate switch which are quite pricey over 200A and eat up a lot of space.

    Also, all the major MCCB manufacturers have distribution lugs so you can get rid of distribution blocks if it is a feeder. Bussman has some fuse blocks that have the same feature but they are only recognized so we had to pay UL to get them added to our procedure.

    Incidentally, I have found it is often more cost effective to buy an extra MCCB with distribution lugs in lieu of a distribution block because most distribution blocks have issues with SCCR ratings and require fuses to get much of a rating.
    Noted and makes sense.


    By any chance have you ever worked with QMQB bolted pressure switches?
    I'm in over my head...

  8. #8
    Join Date
    Feb 2005
    Location
    Charlotte, NC
    Posts
    6,768
    Quote Originally Posted by mbrooke View Post
    How much do fuses cost as compared to that saved on having them? My (thin) understanding are that breakers cost much more upfront.
    True, but say you spend $20k on a MV breaker, that's it for 20 years or so until you have to refurb it and/or replace VI's, etc..

    MV fuses can be a few grand each, plus as mentioned you will need a switch to house them in ($10k). A phase to phase fault will blow 2 of those fuses and that costs a few grand everytime it happens. Google 400E fuse and look at the prices, not cheap.

  9. #9
    Join Date
    Jan 2016
    Location
    PA
    Posts
    5,697
    many faults on the utility side are self clearing
    trees, wind, birds, critters, etc.
    every time you have one of these and blow the fuse you are down for hours, while with a CB you can reclose when cleared

    a cb with relaying can be coordinated much better than any fuse set-up
    The difference between genius and stupidity is that genius has its limits.

  10. #10
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    16,789
    Quote Originally Posted by mbrooke View Post
    By any chance have you ever worked with QMQB bolted pressure switches?
    no
    Bob

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •