Porcelain vs polymer housing Metal-oxide station class surge arresters (2021 comparison) 2

[VMMF]

I'm writing the specifications for a new substation class transformer that needs to be purchased. As a guideline, I'm using the specifications written by our provincial utility company for a similar transformer that was bought by them. On the lightning/surge arresters section they specify "Intermediate Class and/or polymer housing arresters are not acceptable". However after reading many documents from manufacturers as Hubbell and ABB they all seem to promote polymer over porcelain claiming that it weights less, it is less fragile, it doesn't explode (if reclosed on a failed arrester), the pressure relief capability of the porcelain housed arrester is only for the first venting,etc.

I have the following questions:
1. Are porcelain surge arresters considerably cheaper than polymer housing arresters?
2. Are utilities reluctant to install polymer housing arresters because even in 2021 they need to be frequently cleaned to prevent malfunctioning?
3. Has the polymer housing arrester a shorter life (aging faster, temperature, UV, etc) compared to the porcelain arrester?
4. Even in 2021. Do polymer housing arrester losses hydrophobic properties in time?
5. What other possibilities may lead the utility to only work with porcelain ?

 

[RRaghunath]

Polymer is a generic term. Silicone rubber based polymer is known to withstand harsh weather conditions outdoors and provide good life.
Many clients changed the term polymer to Silicone rubber based polymer and most of the established vendors like ABB, Siemens are able to provide Surge arresters with silicone rubber based polymer material.

 

[VMMF]

@RRaghunath Thank you for your answer. So Silicone rubber is actually better than porcelain in every aspect mentioned in my question? What possible reason has the utility company to continue using porcelain then?

 

[Rejeckted]

Check this Comparison by ABB (OEM)

https://search.abb.com/Library/Download.aspx?DocumentID=2750 515-136&DocumentPartID=&Action=Launch

Good Luck!

 

[RRaghunath]

Porcelain insulators / bushings used to have better cantilever strength but not any more. Silicone rubber insulators / bushings are superior to porcelain ones in every respect now.

 

[cranky108]

But do Silicone insulators have the life that the porcelain does? That was the early problem with the silicone products.

Then again, the porcelain is a known long life product.

 

[dpc]

Utility engineers (and linemen) are notoriously conservative. They like to use what they know and earlier polymer insulators had some issues. Porcelain is a well-understood technology. One of the major selling points among rural utilities for the polymer insulators was better survival rate when shot.

 

[davidbeach]

As-installed porcelain is just pre-shrapnel. Polymer doesn’t become shrapnel. Ever been in a station following the failure of a porcelain device?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[VMMF]

Thank you for your answers.
@ Rejeckted excellent!
@ RRaghunath I have the same doubt as cranky108
@dpc. What do you mean better survival rate when shot? Vandalism?
@davidbeach If porcelain lightning arresters are sized with enough Pressure Relief Capability-Symmetrical rms (kA). Do they still end up exploding if reclosed to a fault? According to Hubbell "pressure relief capability of the porcelain housed arrester is only for the first venting" Does this mean that porcelain lightning arresters are pretty much 1-time use devices if we want to prevent an explosion and no reclosing is installed?

 

[cranky108]

Arresters are not a one time use device. Except if you have something other than a one time lightning, in the same reclosing interval.

David is right, porcelain when over pressured will explode, where silicone will split, then conduct.

But silicon will survive better when shot, but if people are shooting at your substation, that is actually a different problem.
On the lines, people do try to shoot the birds, with no vandal intent.

If shooting at your substation is a problem, a couple of things to try. Place a single light in the substation. When it is shot out, they can't see anything to shoot.
Or place a target, some distance from the substation (an actual target).

 

[dpc]

Yes, shooting insulators seems to be some kind of sport in some areas. I guess they are more challenging than the highway signs. Fairly common to see polymer insulators with a skirt shot off but still in service.

 

[sushilksk]

Polymer surge arresters have replaced porcelain in most of the applications. One issue of polymer surge arresters is large defelection at rated cantilever load, this needs to be specified before design.

 

[kartracer087]

The other thing to keep in mind as well was their use as fuse supports. Until IEEE came out with C37.41 2016 edition, it was kind of the wild west in terms of fuse supports for devices like cutouts. You saw the horror stories of cutouts breaking in half on stick operations because of the mechanical strength was not there. The 2016 C37.41 spec made some enhancements to address silicone rubber cutouts and the performance requirements of them. Nowadays with these enhancements in specs, you see more utilities with greater comfort in using silicone rubber or polymer type insulators and bus supports/apparatus insulators.