cable limiter

[kendrichchan]

cable limiters are short circuit devices that can isolate a fault cable.

a cable limiter is a short circuit device only?

 

[augie47]

yes

http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/Solution%20Center/technical_library/BUS_Ele_Tech_Lib_Cable_Limiters.pdf

 

[Electric-Light]

So, it's basically a single element fuse housing only the short circuit interruption portion of dual element fuse?

 

[cpal]

So, it's basically a single element fuse housing only the short circuit interruption portion of dual element fuse?

all the limiters I've seen where constructed with several (many) elements rather than one single link. As I understand this design feature reduces the possibility of a sustained arc. (provides several points of burn off).

 

[broadgage]

It should be noted that cable limiters seem to be a USA idea, they are virtually unknown here in the UK.
Most UK or European electricians or engineers would not know of them.

We use standard fuses here, thereby avoiding the costs of manufacturing and holding special items.
If it is desired to protect a cable against short circuit, but not against overload, it is common practice to use a standard HBC fuse rated at 2 or 3 times the cable rating. If overload protection is also required, then a similar type of fuse would be used, but with a rating not exceeding the cable ampacity.

As an example, at my work place, a cable owned by the POCO feeds a large chiller.
The cable is protected in the POCO substation by 800 amp fuses. These will not protect against overload because the cable is suited for about 380 amps.
Similar fuses, but rated at 315 amps are installed in our switchroom these protect against overload, or short circuit.
Any fault in the customers equipment should only open the 315 amp fuses, these may be replaced by the customers electrician.
Only the POCO can replace the 800 amp fuses as these are in the locked substation.
Note that contary to USA practice, these are standard fuses, not specialy made "cable limiters"

 

[Electric-Light]

all the limiters I've seen where constructed with several (many) elements rather than one single link. As I understand this design feature reduces the possibility of a sustained arc. (provides several points of burn off).

Well, it maybe built that way internally.
"dual element" fuses have whatever construction to quench fault current and have high interrupting capacity in addition to overload protection (i.e. 200A on 100A 20minutes). Element #1, however segments it maybe made of, acts instantly on shorts. Element #2 responds by becoming hot gradually and eventually melting.

 

[don_resqcapt19]

It should be noted that cable limiters seem to be a USA idea, they are virtually unknown here in the UK.
Most UK or European electricians or engineers would not know of them. ...

Cable limiters are not really used to protect the cables. The are normally used at both ends of cables that are connected in parallel. This lets the cable limiter clear the faulted cable and keep the other conductors of the parallel circuit in service. Other applications are for multiple loads fed off a single source. Here again they are intended to clear the faulted cable and keep the other loads in service.

 

[Electric-Light]

Cable limiters are not really used to protect the cables. The are normally used at both ends of cables that are connected in parallel. This lets the cable limiter clear the faulted cable and keep the other conductors of the parallel circuit in service. Other applications are for multiple loads fed off a single source. Here again they are intended to clear the faulted cable and keep the other loads in service.

Unless the cable are paralleled for redundancy(capable of carrying design with any single conductor), that would allocate the system current to whatever conductor(s) remaining. Wouldn't that overload the remaining conductors?

 

[don_resqcapt19]

Yes, there will be more load on the remaining cables, but they can prevent a total loss of power. They are often used by utilities that use networked (transformers connected in parallel) distribution on the low voltage side of their transformers.

In institutional, commercial, and industrial systems, cable limiters are used at both ends of each cable on three or more cables per phase applications between the transformer and switchboard, as illustrated in the diagram and photographs. In residential systems, the cable limiters are normally installed on a single cable per phase basis at the source end of the lateral feeder to each residence.

Quote is from this document.