PPE and Safety checklist for switching 2

[Mbrooke]

Just to compare with others, what are the typical worker safety requirements, checklist and precautions required for you when opening/closing HV and EHV group operated isolators? Is it realistic to anticipate such an incident like this at 2:30? Would PPE even help?

https://www.youtube.com/watch?v=3DsJTDLHiIQ

There is a lot of debate regarding what precautions to take when performing routine maintenance switching.

 

[jraef]

Note to self: double up on underwear prior to working there.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[jfpe]

Typical PPE that we see includes safety glasses, hard hat, arc rated clothing, and voltage rated gloves.

I don't know of any PPE that will completely protect against switch gear disintegration like what happened in the video.

-JFPE

 

[marks1080]

We don't have nearly that much grass in our switch yards.... I still use steel toe boots though.

 

[wbd]

If there was an arc flash study done, then some sort of AR PPE would be worn and I don't believe the clear faceshield is AR. The other point is how much of a good visual inspection was done of the porcelain insulator prior to opening the switch? In utilities I have worked for a good visual inspection is made using binoculars as needed. For vertical single blade disconnects or fuses, a tug on the porcelain would be made prior to pulling the switch open.

 

[Mbrooke]

How does this tug work? What if the insulator failed during the tug?

 

[wbd]

Typically since the tug is done with the switch still closed, if there is any breakage the insulator would still be supported by the switch. The tug is done with a hot stick that has a hook on it.

 

[LFAVianna]

The arc flash study should define the ATPV of each electrical power system location. These studies follow the standard NFPA 70E. Please see the attached table where the NFPA describes the PPE list for each ATPV level determined.
The NFPA also describes a list of PPE to some activities in systems without arc flash studies.

 

[Mbrooke]

I'm confused though- where do you assume the fault in these studies? I have always seen them overhead, above the worker, however an insulator falling to the ground will put the arc right in front of the person.

 

[LFAVianna]

The studies assume several points of analysis. In the mathematical model there are classifications of the point in analysis, like "Open air","Switchgear" "MCC, Panels", "Cables".
It is important to define that the method proposed by NFPA 70E refers to the IEEE 1584, where only are valid to the calculation the triphasic faults.
Usually, when we make these studies, are considered switchgears, points in the open air, like power transformers and cables. The short-circuit study is used as base to the results in every busbar of the system and the operator approximation to the faulted point.
Zones of risks are usually resulted from these studies, assuming that nearest the operator is from the fault point higher is the ATPV level.

A good study takes into account several points of risk, always being conservative.

 

[wbd]

Note that in NFPA 70E, utilities are exempt and that seems to be what the personnel in the video are, utility workers. But in a different country.

Here in the USA, utilities follow the arc flash regulations in OSHA 1910.269, not NFPA 70E

 

[stevenal]

I dispute that NFPA is applicable here. To my knowledge, NFPA is only applicable in the USA. This also appears to be an electric utility, specifically excluded under the scope of NFPA 70E.

 

[LFAVianna]

Here in Brazil, we do not have an expecific standard to deal with arc flash evaluation. In our standard, we are oriented to seek international references, like the IEEE 1584, that refers to the NFPA 70E.
The scope of the NFPA 70E (2018) excludes "Installations under the exclusive control of an electric utility". In the video, it is not very clear the application of the installation.
The classification purposed for the PPE can be used as reference, since it uses conservative results by the Ralph Lee method, mainly in the absence of local regulations.

 

[wbd]

LFAVianna - I think it help the discussion to understand what your focus is. Are you asking on behalf of a utility or a non-utility entity?

 

[Mbrooke]

FWIW, my question is utility based, North America.

 

[low1]

We use FRC/ARC flash rated clothing as per assessment, hard had, face shield, hearing protection, steel toe boots and rubber gloves. Procedurally, we are taught to identify escape routes in the event something goes wrong.

 

[stevenal]

In the USA, requirements are spelled out in IEEE C2, the National Electrical Safety Code; as well as in OSHA 1910.269 and 1926.
As pointed out above, substations are kept free of vegetation. They are also covered with high resistivity crushed rock, and workers stand on conductive platforms bonded to the switch handle when switching. Looks like the worker in the video wisely put on dielectric boots prior to switching, but they might want to consider mowing before the vegetation reaches up past their boots.