distance between joints

[144x]

one joint in one of our 66kv cable routes has been failed.after cutting the cable now there is a need for connecting a separate piece of cable to the previous cable.is there any practical limitatation for the distance between 2 successive joints? can we have 2 joints within a distance of 3 meters for example?

 

[abeltio]

have you tried posting it on the IEEE code forum? I had a posting on the batteries engineering and nobody answered until I changed to a different forum...
hth (hope this helps)
a.

 

[redtrumpet]

This is probably the best forum for this post. It may be that none of the members have the experience or knowledge necessary to answer the question - it happens!

 

[gordonl]

The only constraint I can think of for the distance between splices is the space required for the splices. I suppose if the cable is being stretched to the limit (in ampacity)there may be an issue with heat generated in the splices and heat dissipation through the splice and longitudally along the cable. I would suggest you contact the splice manufacturer (assuming your using kits) and get their feedback.

 

[benray]

I have performed bare handed live line maintenance on HV conductors damaged by bullet strikes. There is always enough slack in lines to permit cutting out the damaged portion. This makes only one splice(joint). Three meters may be a different situation, and require two splices(joints). Check and determine if slack can be pulled. One splice is better than two.

Good luck; Ben

 

[benray]

My error, sorry, I assumed this to be an overhead line. It appears to be an underground or in vault cable. Review the cause of first failure for making a resolution. Splice(joint proximity)correctly performed, should not be a problem.

 

[cuky2000]

Statistics show that splicing is the location were the highest frequency of failure happening in cabling system. If the installation is underground in metropolitan areas most A/E and utility prefer to do the splicing inside the manhole or in area were the repair will not disrupt traffic or other services.

The exposure to reduce the system availability could vary depend on the installation. If this cable is a vital component, then the impact of the additional splice could compromise the expected reliability/availability of the all installation such as in the interconnection of generating plant with the utility substation or similar installations.

It is easy to say than act, but if I were responsible to accept two splicing in installation like that I would think twice considering the following approach:

1- If the installation of those splicing are originated by cable failure, I will consider the extra splice as a temporarily fix until identify the origen of the problem.
Typically failure of this nature suggest degradation in the cable insulation due to cumulative stresses either for surge overvoltage, environment conditions, inappropriate surge/grounding protection or other combination causes and more failure is expected to happen as the time progresses.

2- If this were a new installation were typically additional 69 kV cable is not abundant storage or easily to delivery in short notice, I would ask the responsible party to fix the problem at a convenient time that will not compromise the project schedule or fix this situation during scheduled outage.

3- An intermediate alternative is not do nothing and accept the risk.

Perform risk analysis could identify what to do better in cases like that. Beaware that either case will add extra time and cost to the project.