TRXLPE versus EPR - MV cable

[magoo2]

I know there are and have been different camps on insulation preferences for medium voltage cable. Some swear by EPR while others will only use XLPE (or TRXLPE).

Is there any good data today to suggest that one will give better performance than the other or is the current thinking that it simply a matter of choice and you get acceptable performance from either? Why would you prefer one over the other?

 

[davidbeach]

It is more like Mac vs. PC. Good luck.

 

[saladhawks]

Yeah, the MAC is better.

 

[dpc]

As far as performance - here's the Cliff notes version:

EPR - more reliable in terms of insulation failure. Historically, MUCH more reliable, but newer TRXLPE is supposed to be much more reliable than the old stuff. I don't know of a single industrial facility that uses anything but EPR for medium voltage cable.

TRXLPE - lower losses. EPR has higher dielectric losses than TRXLPE. These losses are small, but when you are a utility that is running hundreds of miles of the stuff, it adds up, at least if you're an accountant.

If the application is an industrial facility, I wouldn't think of using anything but EPR. If it is for URD cable that you are buying by the MILE, then a cost/benefit analysis may be in order. Most utilities use XLPE because first cost is lower and losses are lower.

 

[saladhawks]

From a cable splicer perspective, EPR is easier to work with. At the utility I work for, the impact of greater losses is considered less important than the advantage of EPR being easier to work with.

 

[magoo2]

Our company (utility) has used both and have not seen a significant difference in reliability. I guess that's the Mac versus PC argument.

We've evaluated the cost of losses and concluded that the premium one pays for EPR over XLPE is essentially doubled when you add in the lifetime cost of dielectric losses. This is more the pay me now and pay me later argument.

 

[Zogzog]

XPLE is know to be suspetable (I know I spelled that wrong) to water trees, hence the more expensive and slightly more resistant TR-XLPE, which hasnt proved to be much better.

It is simply a matter of cost vs reliability, if you are talking about 3000 miles of cable, I would go XLPE, if this is for a plant then use EPR.

 

[magoo2]

I think you'll find that EPR is also susceptible to water trees. It's just harder to detect them because the material isn't transparent like XLPE. We used to slice wafers of older XLPE cable that had failed and you can see various defects this way, including manufacturing defects. This method doesn't work with EPR because it's opaque.

I think Carlos Katz of Cable Technologies Lab has done some work showing the presence of water trees in EPR as well as XLPE.

 

[Zogzog]

I saw some EPR samples from CTL on EPR, yes you can get water trees in anything but it is more likely in XLPE, mostly service aged cables, thats what I meant to say.