TripCurve

[Engcan]

Hi,
I am asking this question keeping in mind that no question is stupid. This might be drop in the ocean for you but these questions are bothering me. Please see below:

Q1 In case of selection of relays and circuit breakers for protective coordination, When it comes to molded case circuit breaker: Is it correct that they have their own TCC curves.

While in case of SF6 or Vacuum CB's, it is the relays TCC curves are used as relay will activate the CB. am I correct?
If yes is any time considered for the CT's.

Q2 Somebody suggested here a link on this website written below from bussman

http://www.bussman.com/library/docs/EPR_Booklet.pdf

this article talks about using current limiting fuses at every place. Is it true in practice also or depending upon the tolerance of the equipment being protected, we decide we have to use a current limiting or a normal fuse.

Q3 My last question, what is a lowpeak fuse and how do we decide while selecting fuses, who will be the manufacturer while doing design for example
: Cooper power, Bussman, Hubble .

I am sure this might take a bit of your time. I would appreciate, if you guys could drop few words.

Regards,

 

[alehman]

Q1: Yes. Some types have a variety of available trip units which have different curves. Some have adjustable settings. Medium and high voltage breakers typically utilize external relays as you suggest.

Q2: Selection of current limiting fuse (or circuit breaker) is typically driven by the available fault current and ability of the protective device and the protected equipment to withstand that current. Current limiting is commonly employed to increase the interrupting rating of the device and to reduce the let-through energy for high fault current levels.

Q3: Lowpeak is a trade name for a particular manufacturer's current limiting fuse product line.

 

[RonShap]

If you work for a fuse manufacturer, then you need to specify fuses everyplace.
Most folks have personal preferences regarding when a fuse is used, as most circuit breakers can do what fuses do. Both have pluses and minuses.
Personally, in a critical environment, we only specify circuit breakers for ease of reclose after investigation.