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Cable limiter availability?

A

AlbertL57

Member
Location
Falls Church, VA
Occupation
Solar maintainer
No supplier seems to stock them, and they're quoting lead times of 6 months or more. Does anyone know what happened to that supply chain?
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
ramsy said:
Are those allowed to reduce AFC to cheaper equipment ?
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No.

Usually, they are intended to open a faulted cable in a parallel set of conductors. They are not designed to be used as a backup OCPD.

I don't think I have ever seen a trip curve for a cable limiter. Without knowing its opening time you would not be able to calculate the resultant incident energy.
 
PaulMmn

PaulMmn

Senior Member
Location
Union, KY, USA
Occupation
EIT - Engineer in Training, Lafayette College
A

AlbertL57

Member
Location
Falls Church, VA
Occupation
Solar maintainer
PaulMmn said:
I'm mystified. How are these different from a fuse or circuit breaker? The spec sheet appears to only deal with wire size, and doesn't mention current... How does it -know- it's time to open the circuit?
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Yes, it does seem mysterious! You're correct - they are rated only by wire size and material (e.g. 250MCM Cu). Internally, they must have some kind of fuse element, apparently rated only on the basis of preventing the wire or insulation from melting.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
LarryFine said:
It sounds like a large fusible link.
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Which open after the conductor has already faulted, hopefully preventing/reducing damage to the other conductors in the set. It may be better to limp along on a reduced number of parallel conductors than it is to lose the entire facility while waiting for new conductors.
 
C

Choice_Gorilla

Senior Member
Location
New England
Occupation
Journeyman Electrician
PaulMmn said:
I'm mystified. How are these different from a fuse or circuit breaker? The spec sheet appears to only deal with wire size, and doesn't mention current... How does it -know- it's time to open the circuit?
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The paperwork says they don’t offer over current protection, just short circuit. Personally never even heard of the things, let alone installed them.
 
A

AlbertL57

Member
Location
Falls Church, VA
Occupation
Solar maintainer
Choice_Gorilla said:
The paperwork says they don’t offer over current protection, just short circuit. Personally never even heard of the things, let alone installed them.
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I believe a lot of their use is on the utility side, specifically on secondary networks (multiple transformers paralleled on the LV side, usually underground) where available fault currents are very high. By quickly isolating individual faulted cables, the limiters help maintain service continuity.
 
D

David Castor

Senior Member
Location
Washington, USA
Occupation
Electrical Engineer
Bussman makes them. Not sure why the long lead time. It's essentially a current-limiting fuse. Here's a TCC for 500 kcmil Buss limiter (according to EasyPower).

1722805317462.png
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
David Castor said:
Bussman makes them. Not sure why the long lead time. It's essentially a current-limiting fuse. Here's a TCC for 500 kcmil Buss limiter (according to EasyPower).
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How does thus compare to a typical OCPD? Your example is for a limiter to protect 500kcmil which is typically applied at roughly 380A. The TCC shows this limiter would carry roughly 2500A for10 sec before opening. This doesn't seem like it would be easy to coordinate with.
 
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