Outdoor Cable Terminations / Do They Include Short Time Withstand Ratings?

[saladhawks]

For outdoor cable terminations (cold or heat shrink) between extruded shielded cable and rigid-bus open-air rack - I have not been able to locate any specific short time withstand ratings supplied by vendors (such as 3M).

Vendors do provide applicable BIL ratings. In addition, documentation states adherence to IEEE 48 Outdoor Class 1A (which I do not have a copy of).

On a side note, underground connectors (such as 600 Ampere components) include both a BIL and short time withstand rating in vendor documentation (such as Elastimold).

Thank you in advance.

 

[cuky2000]

Why the short-time rating is important for you?

Similar to the rigid bus dynamic performance, cable terminations are exposed initially to magnetic forces (by peak current) and heat thermal effect (by RMS current) until the protective device trips.

Only Elastimold Cable Joints specify a Short-Time rating equal to the rating of the cable up to 35kA shield design per IEEE 404 "Standard for cable joints and splices".

However, the IEEE Std 48, "standard for cable terminations" does not specify a short-time rating for cable termination.

[sub]NOTE: Neither the 600 A deadbreak separable connectors Link or the 200 A loadbreak elbows Link indicates the short-time withstand rating.[/sub]

 

[saladhawks]

The short time rating for cable terminations (cold and heat shrink) is important to me as they are connected to an utility system with over 40 kA sym Amperes fault duty (both 3PH and SLG).

Circuits leave Receiving Station Open-Air Rack via underground synthetic cables. We have to be really careful where our first installed underground connector is installed to meet their 25 kA sym Amperes short time withstand rating.

Since vendor documentation was completely silent, I was just making sure the installed cable terminations between Open-Air Rack and underground synthetic cables had an adequate short time withstand rating for the 40 kA sym Amperes available fault duty.

 

[kartracer087]

Load-break and Dead-break elbows indeed do have manufacturer short time ratings. A typical 600A dead-break elbow will have a short time rating of 25kA symmetrical for 0.1 second, and a load-break elbow 10kA for 0.1 second. These would be acceptable for your 25kA symmetrical application based on what information you have provided. I can also think of one manufacturer who has a 40kA rated dead-break elbow see here: Link. As far as live type terminations (heat shrink or cold shrink) I am not aware of any ratings by manufacturers for those. I do not believe it is an issue with those types. I can say the same about hand taped or inline splices that there is no real established rating to those. Generally speaking lead splices and other types of hand made splices historically have had very high withstand ratings based on field experience. Same with hot and cold shrink terminations, those typically do not have a published value but have been used successfully in demanding environments. But an actual number is not available.

Also, one last note, be aware of the difference between symmetrical and asymmetrical amperes. Symmetrical does not include the first cycle DC components, so those values are much lower than the asymmetrical values. You might find that the 25kA symmetrical elbow will work with 40kA asymmetrical amperes. Asymmetrical depends directly on the X/R ratio of your system which you can get from the Thevenin sequence impedances at the specific point you are installing your devices.