arc flash barrier

[patrick7961]

I have a situation in which there are pad mounted transformers.

These transformers have a high side disconnect switch internal to the transformer tank. These switches are designed for occasional switching. The problem is: in order to access the switch you must open the low side compartment then open the high side compartment. Doing so exposes energized equipment.

Has anyone thought of a way of mitigating the exposed parts as to allow access to the transformer switch?

I am thinking of installing a barrier of some sort.

Any comments or suggestions on the type of barrier.

 

[Zogzog]

We have remote (Wireless) switching available for some types, and are developing more.

http://www.remoterackingsolutions.com/remote-switch-operators.htm

 

[cranky108]

We have consitered using a laxan shield, but the question I keep bringing up is do we have any data supporting the idea of it being an effective shield.
And are you willing to take an outage to replace it when it ages?

However they do make a face shield for FR and arc flash protection, so what is it made of?

Some of these problems over time will change the required designs of pad mounted devices, but we have to wait and do it ourselves for now.

 

[dpc]

We have been grappling with this issue as well. Ideally, the manufacturers would make a separate compartment to access the HV switch operator, but that is not the reality today.

Our recommendation is to fully insulate all low voltage voltage parts using boot kits and taping. With no exposed live parts, the risks of opening the LV door are greatly reduced.

Also, the door can be "roped" open to increase working distance.

"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

 

[jghrist]

Also, the door can be "roped" open to increase working distance.

Do you have a hot stick adapter for a penta head wrench?

One solution is to get some gophers to backfill the compartments as shown in

http://www.mikeholt.com/newsletters.php?action=display&letterID=724

 

[stevenal]

I'm not sure that opening a padmount cover is sufficient interaction to require PPE or mitigation, if no work is performed on the exposed live parts. The 70E table lists removing bolted covers, but in the case of a padmount the penta is only there for security. If the hinges are sound (they can be inspected first), I see little chance of the opening action creating an arc.

 

[stephenw22]

Depending on what your high-side switchgear is, you could install an arc flash relay. I've heard them called Vamp relays, but I think that's just a brand name. Anyways, the worker wears a photosensor that is wired back to the switchgear and trips it if an arc occurs. It may significantly reduce the arc flash rating. At least that's the sales pitch we've had on our site from a couple of vendors.

We just de-energize the transformer if we need to open it up. Sometimes it requires a little bit of creative scheduling to find times to do the work, but we eventually get it done if it's important enough.

 

[cranky108]

Part of the problem with arc flash is that so much is undefined. There have been few lawsuits to roundout the definitions and what they really mean.
And between groups we deal with both sets of rules, which is even more confusing.

We consitered plastic covers for 480 fan controls in a transformer cabnet. Not sure we resolved this completly.

We consitered arc flash relays, but there are several issues to be resolved here (like who cleans the fiber, how, when, and how to test).

 

[resqcapt19]

stevenal,
While I tend to agree with you that there should not be much of a hazard in opening a pad mount door, many of the arc flash incidents have involved "traps" left by a previous worker. A tool left inside or some bracket not properly bolted in place that moves as you open the door creating the arc flash. Most of these incidents have involved switch gear or MCCs where there is much more potential for a "trap" than in a pad mount, and there would be much less risk of this happening in a pad mount.