Vulkene cable?

[alehman]

The engineer at an industrial plant has told me that the utility service entrance cables are rated 34.5kV with Vulkene insulation. The cables are pushing 30 years old, I'm told. The plant wants my opinion as to whether or not they should consider replacing them, although there have been no faults. We don't have any other information on the cable or manufacturer.

I'm not familiar with Vulkene insulation. I see BICC has a 5kV unshielded Vulkene cable listed. Can anyone provide insight on Vulkene insulation? Was/is it in common use anywhere? Pros or cons? Known problems?

 

[advidana]

Wow, thirty years that ready great but is about time to replace it.

Vulkene insulation was invented and use by the Germans in ww2. I belive it is now known as EPR Ehhylene-Propylene-Rubber. It's pretty good stuff, it last a long time - over 20 years. but it cost more than the other high voltage plastic insulated cables and the cable sales people push the other newer type cables. you also need larger conduit sizes to intall it because it is thicker. I have only seen it use it on 4160v and 12kv system.

Plants and Facitities use it because they contract high voltage maintenace people for repairs. so they need someting that will last a long time . Utilities alway have people and equipment on staff so they can use the other types, since repair are not a problem, it's what they do.

 

[PWR]

Vulkene was a GE trade name for mineral-filled cross linked polyethylene cable.

As an adherent of EPR since the mid 70s I was skeptical of it but we have many customers who installed it. I would have to say that their experience with it has been good.

The installations I am familiar with are at 5 and 15kV however.

 

[cuky2000]

In my opinion just because the cable is old may not be sufficient reason to recommend its replacement, particularly if there is not history of failure.

Predicting the end of life of a cable is not an easy task since this is not a deterministic phenomenon. I see old cable exposed to a lot of abuses and still in service after 50 years. On the other hand, I see relative new cables manufactured with the latest technology and careful workmanship installation subjected to light loading and minimum stresses failing without obvious reasons.

The failure mode are linked not only to the material and process used but to an appropriate QC during fabrication and installation. After that, the history of service conditions could be a significant factor to determine the remaining of cable life.

In many instance there is not record of the cable fabrication inspection, witness report of the installation and service performance record incomplete or vague. In this case may be appropriate consider testing the cable and determine the cost and consequence vs. the risk of failure and if a practical, prepare a contingency plan that could mitigate the failure and able to defer the investment for several years. After that, you may be in the position to express your recommendation based on findings.

 

[dpc]

It is probably a GE cable. If the cables are not too long, I'd probably budget to replace them and get it over with. If replacement will be extremely costly, it might make sense to just cross your fingers and see how much longer they last. They will fail eventually, but they might outlast you.

Partial discharge testing is a possibility, but I wouldn't recommend a high-pot test.

 

[advidana]

Best to replace it now, a controlled outage is less costly than a surprise outage. If you are in charge you will take the hit for it's failure.

 

[TestBeforeTouch]

If I were going to make a recommendation to this plant I would like to know some more information.

Is the cable in a wet environment? Water treeing (which forms in wet environments and leads to failure) is a concern for XLPE.

How critical are these cables? What is the "true" cost of a failure to the business?

Does this plant have an alternate feed?

If the cables were to fail right now what are your options? (e.g. Can the load be easily supplied by rental generators while repairs are being made)

How long are the cables? Long pulls can mean that a replacment cable may not be "off the shelf".

I would also inform the customer that XLPE should not be Hi-Pot tested as it does not provide any useful information on cable condition.

 

[busbar]

 
Vulkene has been for decades a trademark of GE, and looks to be currently used by BICC. It is a clay-filled cross-linked polymer dielectric, sold in 600-5kV unshielded and shielded at higher voltages.

Somewhat like Kerite and Okonite products {and track records} for other specifiers, there seems to be roulghy similar allegiance to Vulkene.

I thought for awhile there was a

http://www.vulkene.com.

Curiously,

http://tarr.uspto.gov/servlet/tarr?regser=serial&entry=72011924

lists Vulkene as “Filled, Cross-Linked Polyolefin Compositions” by General Electric Co since 1956 .

 

[alehman]

Thanks for the great feedback. this is the only service to the plant. An outage would be costly. The owner is considering adding a second service. I'm not sure that's a total 'fix.'

 

[advidana]

second service is a good idea also use tie breakers.

 

[benlanz]

I have a fair amount of experience with offline partial discharge (PD) testing Vulkene. An offline PD test is the most effect test at determining future performance of field aged cable, per IEEE 400. It would be ideal for you to perform an offline PD test on your cable first so you can make good decision about the future performance. The problem with most Vulkene cables from a diagnostic stand point is that water corrodes the copper tape shields. This makes it impossible to repeat the ‘factory PD test’ to which IEEE 400 refers. The corroded shields will not allow for the PD pulses coming from the defect under stress to travel on the cable. You could have someone come out and test your cable but, if they do a good job and calibrate the test they will more than likely find that the cable will not allow for better than 1000pC sensitivity. A factory test has 5pC sensitivity.

So you are caught in a dilemma. You can not test the cable to see if it is reliable and the information you have is that the cable is 30+ years old and, for the most part, the industry does not use this type of insulation any more (for good reason). From what I have seen of 30+ year old Vulkene I would replace it. At best it is a ticking time bomb with questionable reliability.

When you go to replace the cable I recommend not replacing it with a tape shield!!! Most tape shields will eventually corrode (in about 10years) and you will be left with cable that can not be test with modern diagnostics including, arc-reflection fault location, TDR (radar), or PD testing.

I recommend you place the cable with a concentric or flat strap type shield. If you decide to use a concentric shield go with 1/3neutral or larger. Perform an offline PD test before energizing the circuit and then retest in 10 years. You will have the most reliable system.

-cheers