500 KV distance to ground..

[Luketrician]

Just want to know what the maximum distance that 500kv can/could jump to ground. Were working with a boom lift re-lamping hps fixtures and I know that we're close cause the static is really strong.

We are grounding the lift btw...I thought 11' was the maximum distance but I'm not sure..

Thanks in advance:smile:

 

[nakulak]

I hope somebody who knows the answer responds to your post before you find out the hard way

(I mean that in all sincerity - be safe)

 

[eric9822]

From Osha section on cranes

1926.550(a)(15)(ii)

For lines rated over 50 kV., minimum clearance between the lines and any part of the crane or load shall be 10 feet plus 0.4 inch for each 1 kV. over 50 kV., or twice the length of the line insulator, but never less than 10 feet;

Personally, even 25 feet sounds awfully close.

 

[nakulak]

if my math is right that comes to 25'

oops I see you already said that

 

[Luketrician]

Thanks so much for the responses guys. Well so far we have finished 4 rows with 8 pairs of fixtures in each row. I am pretty sure that we are within 25'..from the best I can tell we're within 15'.

What I have been doing so far is rotating the basket of the lift 90 deg so that I am atleast parallel with the buss. Still a bit scary for me. We still have to go back and change ballasts in some of these fixtures also.


Thank you for the osha refrence, I think I will bring this up to my foreman this morning before we go back out there. I know that being in this industry is dangerous, but I don't think it is a good sign when I am getting lit up by a powerfull static charge...I can even see it jump from my hand when I touch a light fixture.

 

[nakulak]

not good. not good at all.

 

[iwire]

Nuclear plant Electrician

I would have figured there would be a safety department / person that would be all over this? :-?

 

[mdshunk]

The minimum safe working distance (hot stick distance) for 500KV-552KV is 11', 0".

The rule of thumb, functionally, is that each 10,000 volts can jump an inch of air. This depends on a lot of other environmental factors, however. The minimum safe working distances are covered by OSHA (1926.950), but they are all approximately double the "inch per 10,000 volt" rule of thumb.

Yes, your lift must be grounded and considered energized unless it has an insulated boom and dielectric hydraulic fluid. At that voltage, even if the boom was insulated, good practices mandate grounding of the lift anyhow.

 

[Luketrician]

There is a TVA safety procedure in place that has the minimum distance at 119 inches..or 10'. I was just really wanting some more information and was hoping that the osha values would reflect our(TVAs) safety procedure. Working out there around 500kv really gets me to thinking about what is safe.

Now, with the help of some fine people on this board I have to wonder why TVAs safety procedure is different than the minimum distance than OSHAs????


OSHA minimum from 500kv = 25'

TVA Minimum from 500kv = 10'



Since it is the weekend I may have to wait till monday to ask this to our Saftey man.

 

[nakulak]

it may well have something to do with the fact that there is a presumption that all the workers at the facility are "qualified". not sure about that tho. I didn't read thru the osha section but I'm assuming that that is for any average joe working distance. (I'll leave it to you to read the osha stuff - I won't be working near 500kv anytime soon lol)

 

[don_resqcapt19]

Marc,
We will have to look at a different section as the one you cited does not apply to this work. It only applies to "the construction of electric transmission and distribution lines and equipment". I see no way that re-lamping fixtures falls into that. For these workers and this work, I beleive that the following is the OSHA rule that applies.

1910.333(c)(3)(i)(A)(2)
For voltages to ground over 50kV - 10 feet (305 cm) plus 4 inches (10 cm) for every 10kV over 50kV.

 

[Luketrician]

it may well have something to do with the fact that there is a presumption that all the workers at the facility are "qualified". not sure about that tho. I didn't read thru the osha section but I'm assuming that that is for any average joe working distance. (I'll leave it to you to read the osha stuff - I won't be working near 500kv anytime soon lol)

Yeah you may be on to something there. I am not a lineman, and normally I am not around our switchyards. The lineman used to maintain these lights but they're spread too thin. So management gave the responsibility to our group of inside j/ws.

 

[mdshunk]

OSHA minimum from 500kv = 25'

TVA Minimum from 500kv = 10'

I'm not sure where that 25' came from, because that's not right. I think that's for cranes. For T&D construction work, it is from Table V-1 of 1929.950, and that says 11 feet. For general work around live lines in a generation plant, that's covered under 1910.269, tables R6 through R10, which would normally be 11 feet, 3 inches. That crane rule is sorta mirrored in this section too, under "materials handling and storage". That's the one that's 10 feet for the first 50kv and 4 inches for each additional 10kv.

 

[mdshunk]

Marc,
We will have to look at a different section as the one you cited does not apply to this work.

I don't think your section is right either, since this is a generation facility. 1910.269 fits better.

 

[Luketrician]

Oh ok MD, I was thinking that something was amiss here..with there being such a huge gap between TVA and Osha safety procedures....

 

[mdshunk]

I think that there's no way you should be doing this work anyhow. It seems pretty obvious that they havn't provided you fellas with the proper safety training to do this work.

 

[Luketrician]

I think that there's no way you should be doing this work anyhow. It seems pretty obvious that they havn't provided you fellas with the proper safety training to do this work.

What happens out here is that before a job is started it goes to planning. Where a planner looks at the job and performs an anylisis to determine if there are any safety issues associated with the job, "JSA".or Job Safety Analyisis form. Then the work order is issued to our group with a copy of the JSA, and before we go out to do the work we have a breifing discussing the JSA and any other risks. Now we have discussed this with our crew and the JSA was talked about. However, the JSA goes along with the TVA safety procedure which states the 10' minimum distance to ground.

Which is why I wanted to bring this up here..I don't think we are 10' or that close..but I still want to be sure. I have seen the videos of 500kv arcing across greater distances than 10' 15' or 25'...so I just want to be sure that I am not in any grave danger doing this work...

 

[don_resqcapt19]

Marc,

I don't think your section is right either, since this is a generation facility. 1910.269 fits better.

I don't think so...they are not working on the maintenance of electric power generation, control, transformation, transmission, and distribution lines and equipment.

1910.269(a)(1)(i)
This section covers the operation and maintenance of electric power generation, control, transformation, transmission, and distribution lines and equipment.

 

[mdshunk]

I don't think so...they are not working on the maintenance of electric power generation, control, transformation, transmission, and distribution lines and equipment.

How are the lights in the switchyard not equipment? They simply are. Look at your typical transmission facility, and you couldn't service the lamp standards many times and maintain a 25 foot clearance, even if you wanted to, without shutting the whole place down. I think you're out in left field on this one.

 

[zog]

I think the 10 Ft distance is for qualified personel working on equipment in section 1910.269, the 25 ft is for unqualified personel. From the sounds of it the OP is working on equipment described in 269 but is unqualified based on the fact that the OP had to ask the question in the first place.