16 Mar 04 10:19
A lot of great responses here. The original question didn't specify utilization voltage or application (underground, cable tray, conduit) which would be strong determining factors.
Tree resistance has been discussed, which would suggest EPR for underground or wet applications.
Temperature has been discussed. My experience is that EPR is significantly more flexible, although your choice of PVC as a jacket material means that you will have a stiff cable anyway.
Flame retardance was briefly mentioned. One cannot say that one material is always more flame retardant than any other, but EPR tends to be more flame retardant in general. That's because the standard way to make cable insulation more flame retardant is to dope it up with halogens (mainly chlorine and bromine). They add to the insulating properties of EPR but subtract from the insulating properties of XLPE. As a result, it's easy to make EPR flame retardant and harder to add flame retardance to XLPE. At 5kV and standard insulation thicknesses, though, XLPE can be made reasonably flame retardant.
For cable tray applications and others, XLPE and XLPO are making headway as low-smoke, low halogen insulating and jacketing compounds. Those same halogens that make EPR flame retardant are lethal during a fire. Once again, your choice of PVC as a jacket material suggests that you aren't concerned about low-smoke.
My impression is that the XLPE compounds are VERY similar between manufacturers but there is very little similarity between EPR compounds between manufacturers. They all have their proprietary recipes for EPR. That is why it is very important to use a reputable manufacturer.
The comment above about difficulty stripping EPR insulation is something to consider but the problem has been overcome by the really good manufacturers.
If your utilization voltage is 2.4 kV you might consider unshielded cable. Otherwise don't even think about it. The only manufacturer that I'm aware of who would try to sell you an unshielded cable for >2.4kV is Kerite. Let's just say their opinion differs from the mainstream in that regard.