Installing Two Arresters in Parallel 2

[David.83]

Hi everyone,

wondering if some of you got experience or knowledge on the effectiveness or convenience of using 2 arresters in parallel.....

Here i found this information related from a previous thread:
thread238-160262

We are now considering the development of a DUAL ARRESTER ...there could be some benefits

Many Thanks

 

[bacon4life]

Putting two arrestors in parallel would mean twice as many possible components to fail. Are there any benefits you are hoping for besides only have one model stocked in your warehouse?

 

[cranky108]

Because of product variability, it is likely that one will take more energy than the other and will fail first, with the shrapnel taking out the other.

 

[jghrist]

If they were of the gapless type, I could see reducing the 10 kA maximum discharge voltage down to the 5 kA level, assuming equal distribution of discharge current. For a Cooper Varistar 9 kV heavy duty riser pole arrester, this would reduce the 10 kA discharge voltage from 27.0 kV to 24.7 kW (91.5%). I would expect no reduction in the front-of-wave protective level.

 

[David.83]

Bacon4life , Well, putting 2 arresters in parallel is related to the redundancy way to improve resiliency (more robustness due to increased current capability, 2 units with 10kA nominal current each) and adding to reliability taking into consideration that arresters are protection products basically being there to preserve expensive assets and avoid premature failures/ disruptions....if we add two components with good reliability it would decrease the probability to loose protection because even though one could be failing the other one will remain protecting the grid/ installation......therefore improving overall reliability as well as resiliency.

Here is a picture from a US Utility using some sort of this idea to protect riser pole point:

Thanks for your comments and feedback.

 

[David.83]

Cranky108, I understand what you mean ....but we´re not considering using 2 - 5kA arresters to 10 kA need but instead using 2 -10kA nominal current arresters to provide more robustness, that being said, those minor disparirites would produce a 70-30% for instance with the possibility to match them as much as we want (as manufacturer).....but always providing much more capacity than only using 1 heavy duty arrester (10kA), therefore giving a sort of Heavy Duty Plus in terms of energy handling capablity.

In any case there is a sequential operation that can be convenient to preserve protection, extend lifetime and let know Utility it´s only one arrester left protecting there.

Thanks for your comments

 

[David.83]

jghrist
Yes, Residual voltage in another benefit that can be acquired by putting 2 arresters due to the sharing current and charge transfer increased.

If we see some specific application such as to protect underground cable and eqpt. it is desirable to have lower protection level (Vres) to better preserve such an expensive and difficult to manteinance installations. Also having there 2 arresters adding reliability+ resiliency.

Thanks for sharing thoughts

 

[David.83]

Overall speaking benefits are as follows:

1) Increased robustness trough redundancy = higher reliability + resiliency
2) Decreases residual voltage , improving protection level
3) Eliminates no-protection window from an arrester failure all the way up to its changeout/ replacement.
4) Extends both arrester´s lifetime by reducing stress related prematury failing.

this is from our perspective but all opinions are welcome and appreciated.

Always happy to share and learn from community. Thanks

 

[bacon4life]

Oh I had been concerned you were considering using two light duty components instead of a single heavy duty component. Sounds like you are already purchasing the arrestor with the heaviest duty capacity.

One observation from the photo is that the arrestors have fairly long leads, dramatically reduces the protection provided by the arrestor. Configurations such as this eliminate the energized portion of the arrestor lead length.

Depending how well you want them to split current, it be necessary to change out both arrestors in a pair so that they are from the make/model/vintage.

Depending on how arrestors are distributed on the system, there may already be some redundancy. Having one poletop arrestor and one elbow arrestor at the far end of the cable might provide better protection at the padmount transformer than having two poletop arrestors.

In my region there is a low amount of lightning, so a high portion of our arrestor failures come from from causes other than voltage stress. I suppose in high lightning areas a higher percentage of arrestors would fail directly from discharge stress.

 

[davidbeach]

arrestor failures come from from causes other than voltage stress

Sounds like another way to say squirrel.

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

 

[cranky108]

Or hyper velocity lead.

 

[David.83]

Bacon4life, Yes, I completely agree with long leads on the photo and also with the possibility to address this so that can be as close as possible.

In regards to already existing redundancy due to riser pole arresters + elbow type that could be true only to some extent cause the underground cable itself is a non self-restoring insulation and can be damage by transients , specially when considered the traveling wave doubling effect for underground grids.

Thankd for your thoughts

 

[David.83]

Everyone,

Simply said ....what if adding only 30-40 USD to every arrester could be leading to already mentioned benefits (extended lifetime, increased robustness, improve protection level and uninterrupted protection)....specially in the following applications:

1) High Lightning Density Areas
2) Riser pole transition installations (OH-underground)
3) High value assets such as reclosers, transformers, capacitor banks, regulators, etc.

Isn´t this somenthing worth to consider?