Still Having Problems with Static build up on Street Signs and Stop Lights.

[muskiedog]

Funny how the power company doesn't want to give direction.

I will let you know whats up. I will be talking with the highway crew leaders tomorrow.

The hit a gas main installing a railing.

Gas compnay marked it wrong,

I understand someone lost their job today. Thanks god no one went boom.

 

[RayS]

We fought these wrist bands in one plant because hi-pot voltage was high enough for lethal let thru currents.

I'm not comfortable trusting my life to a resistor. Before experimenting with full OSHA fines and liabilities by issuing resistors or non-dielectric equip., not considered PPE, I would need to see it handle more than static, because an energized grounding circuit is not usually slowed by resistance, it tends to heat resistors at it burns thru them.

I understand the concern with attaching a grounding path to your person while working on energized circuits. If there were energized lines nearby, I'd have to say deenergize em. I thought the problem was with static from overhead lines, which I wouldn't think present a contact problem.

The mat in the link I posted could be used without the wrist bands. I would have to try and see if it did any good depending on boots etc.

 

[George Stolz]

I have no practical experience in this, but I would consider grounding to be a better attack than bonding on this induced voltage. But I am not sure. Jon definutely has some theory points over me, but I can't shake my gut feeling on this one.

What really amazed myself was that my AC power sensor stick 110-600v lights up whe you are underneath the transmission lines. Never realized how much juice is in the air.

Mine lights up in my front yard, 200 feet away from the 130kV transmission lines running through my property.

 

[robbietan]

(What I find odd is that the OP said it was worse in damp weather. I'd expect it to be worse in dry. Please let us know what results!)

which shows that its not static electricity


(We fought these wrist bands in one plant because hi-pot voltage was high enough for lethal let thru currents.)

maybe not grounded properly


safety mat is fine to minimize these induced voltages

 

[DaveTap]

Have you ever taken a flourescent tube and held it out on this job site? It would probably glow. It sounds like the people are becoming "energized" just like if you walk across a carpet in stocking feet and touch a door knob or something else grounded, but in this case the "static" is being continuously generated or induced by the power lines. The reason it becomes worse with humidity or rain is that all those rain drops also become charged by passing near the lines and because they are more conductive there is even more power from the lines being transfered or as the power company would say... lost. If I remember correctly POCO can lose approx 20-30% of the power transmitted over high voltage lines during a rain storm... luckily the moisture also helps cool the conductors.
If you have a "peak" meter you might even be able to get a reading although probably not even close to the actual voltage, just by touching one probe end while you contact the sign with the other. I'd also be curious to see if you could get a reading from the sign to a ground rod or from a person to a ground rod.

Most blue wrist straps do not have a resistor... the idea is to make sure there is as little resistance as possible so that personnel are properly grounded and bonded to the equipment and can not build up a charge in the first place.

If you want to get the POCO's attention just have someone on a pace maker go touch the sign... then sue when they have a heart attack. Next day the sign will be fenced off with a sign that says Danger High Voltage... Authorized Personnel Only! (I keep saying I should start a company called Authorized Personnel... it would be so convienient having easy access to all those places)

 

[don_resqcapt19]

Dave,

Most blue wrist straps do not have a resistor... the idea is to make sure there is as little resistance as possible so that personnel are properly grounded and bonded to the equipment and can not build up a charge in the first place.

Are you sure? That would be a real safety hazard. Even with a 1,000,000 ohm resistor, the static won't build up.
Don

 

[winnie]

As I said previously, with no further information, I would be on kingpb being correct, and he is firmly in the 'ground the signs better' camp. I still have a strong hunch that disagrees with this as the solution, but this is a laypersons hunch versus someone with experience in the field.

Remember , "Theoretically, there is no difference between theory and practise."

My hunch is still that the sign is 'grounded' well enough to dissipate any induced voltage. The sign does not have an official 'made electrode', and probably has a resistance to ground much greater than the 25 ohm standard that we see over and over again, but it is sitting on a metal pole embedded in concrete in the soil. Since the impedance of the energizing circuit is also very high, I expect that the sign is inadvertently 'grounded well enough'.

However, if we agree that the signs are being energized in a high impedance fashion by the high tension lines, by some as yet ill defined mechanism (electrostatic induction? Magnetic induction? Air carrying ions from corona discharge? Little green aliens worms that live on the potential difference? ), then it seems to me that other objects in the vicinity would be similarly energized. This includes the truck and the workers.

If you have a worker (energized by proximity to the line) touching a sign (also in proximity to the line, but also in contact with ground), then the worker will receive a shock as they ground _through_ the sign. In this case, the solution is not grounding the _sign_ further, but instead grounding the _worker_ before they touch the sign; or bonding the worker to the sign prior to touch.

The reason that I cannot advocate using some sort of simple bonding cord or strap is that while this might reduce the nuisance shocks caused as above, in the even of a real fault such a bonding mechanism would be a real safety hazard. When lineworkers ground out transmission lines, they follow very careful 'hot work' practise when installing the grounding cables. Similarly, would you want to be in an _insulated_ bucket when working up high, not intentionally near power lines, but always with the risk of accident, or would you want to be in a well grounded bucket? I do not know the relative safety merits.

In any case, the outcome will be determined by the experiment, and I am waiting to see how things work out.

-Jon

 

[muskiedog]

Finally an Update - Power Transmission Line

Finally an Update - Power Transmission Line

Well, we did the additional grounding of the sign structures with out getting any reduction or elimination from the static build up. So I am looking into the best equipment PPE that I can supply the crews to help eliminate the getting static shocks from the signs and poles. Any ideas on gloves, boots etc...

Thanks,

 

[winnie]

Hey, thanks for the update. I'm sorry that the grounding didn't work, although I am perversely pleased that my hunch that it wouldn't work has somewhat proven out.

Re-reading this old thread, I see that all of us who are suggesting bonding are also concerned about the increased risk in the event of contact to an energized line.

If it were _my_ body in that bucket truck, I would wear conductive shoes, put a grounding mat in the bucket, and run a jumper from the mat to the sign post. However not having the necessary engineering experience nor licence, I _cannot_ advise anyone else to do this. I can only offer it as a suggestion for proper engineering analysis.

-Jon

 

[mgd]

use ppe and be done with it. grounding will not solve your problem as you have found out. this is not a static problem as some have already mentioned. an electric (electromagnetic) field that exists between the overhead lines and the "grounded" signs is the problem. the fact that humidity/rain increases the shock confirms this. a bucket truck isolates the user from ground, why undermine this protection by bonding to the signs. maintain the isolation from ground use ppe.

 

[haskindm]

I believe Winnie is on the right track here. The workers are building up a charge, which is dissipated by touching the signs which are "grounded". They would probably experience a similar situation by touching anything else that is conductive and connected to earth. The workers will either need to be insulated from, or bonded to, the signs prior to working on them to prevent them from becoming "conductors". No amount of grounding will make this go away. Grounding does not cause current to disappear.

 

[muskiedog]

Thanks All. Have a great day.

 

[ramsy]

High-voltage static shock

High-voltage static shock

..a bucket truck isolates the user from ground, why undermine this protection by bonding to the signs. maintain the isolation from ground use ppe.

I believe inside wiring authority supports MGD's statement. NEC 110.27, 430.132, NEC 460.6(A), 460.28(A).

Linemen have a separate code (NESC?), but I doubt bonding practices for electrical services are applied to people, where the voltage exceeds that 50 volt threshold.

NFPA 70E and OSHA 1926, 1910, certainly do not approve bonding people in the proximity of high voltages.

I'm having visions of OSHA investigators looking at photos of men in a bucket truck, wired like Frankenstein to road signs below. While the bonding science may be sound any coincidental heart attack or injury would find the contractor in front of a firing squad, before OSHA lynched the corps, and surviving family litigation was awarded any remaining value.

While, some electronics plants bond assembly-line workers thru a 100k Ohm wrist-band-line to remove static around sensitive electronics (intended for use below 50 volts), the problem with this forum is the wide range of experts that share their experience and opinions without citing the supporting authorities.

In matters of safety, or liability wise shoppers should check the authority tag before buying.

If the authority is not current with science or practical principles, you can search letters of interpretation at:

http://www.osha.gov/pls/oshaweb/owa...NS&p_toc_level=0&p_keyvalue=&p_status=CURRENT

The OSHA directorate regularly provides clarification and relief for similar matters of apparent error, or omissions.

 

[ramsy]

So I am looking into the best equipment PPE that I can supply the crews to help eliminate the getting static shocks from the signs and poles. Any ideas on gloves, boots etc...

I've been using an electrical rated Redwing boot, stock No. 6680 with an ANSI Z41 PT99 rating. The boot has a non-metallic impact ratings for the toe, and is rated over 600 VAC insulating. This model is popular with fire fighters, and electrical trades because of the comfort, which does not require a traditional break in. The price was around U$D 200.