Cable Limiter

[wbd]

On an installation at a condominium complex the transformer is a 300kVA, 208/120V secondary. The secondary conductors are 500mcm AL 6 per phase. Transformer FLA is 832A so cable capacity is 1860A more than double transformer FLA. Each conductor has a BUSS Cable Limiter CDB-RV. I could not find this in Buss literature so probably obsolete now. Additional information that may be pertinent: location in Vermont and all condos have electric heat and were built in early 1980's.

Since this is the first time, I have seen cable limiters, I have read the Buss literature on them but have some questions:

1. Since the cable limiter works on short circuit current and not overload, how does one know a single conductor faulted? Does it show physical signs of a fault?
2. If there are physical signs of a cable limiter activating, I assume periodic inspections should be done to see?
3. Without knowing any derating factors applied to the conductors, which seem to be more than needed, was that done to compensate for a possible faulted conductor?

Thank you in advance for answering.

 

[RRaghunath]

Cable limiters are essentially fuses rated in terms of cable size (instead of current rating).
Unlike fuses that are available with operation indicators, Cable limiters come without any operation indicators.
So, I think continuity check of cable runs during every shutdown is the only option.
Anyway, we need to replace cable limiters in all cable runs even if one cable is faulty.