Q1: Workers need to perform maintenance on a lateral tap, fed from a three-phase main line. The workers open the lateral tap’s cutout, isolating the line and follow all the provisions of paragraph (m). They take precautions to prevent the lateral tap from contacting other sources of energy. And, OSHA 1910.269(n)(2) states:
“General” For the employee to work lines or equipment as de-energized, the lines or equipment shall be de-energized under the provisions of paragraph (m) of this section and shall be grounded as specified in paragraphs (n)(3) through (n)(9) of this section. However, if the employer can demonstrate that installation of a ground is impractical or that the conditions resulting from the installation of a ground would present a greater hazard than working without grounds, the equipment may be treated as de-energized provided all of the following conditions are met:
Doesn’t OSHA 1910.269 (n)(2) allow the worker to work the lateral tap without grounds?
Q2: Inside a substation maintenance is to be performed on one side of a 115 kV disconnect switch. The disconnect switch is opened and the provisions of paragraph (m) are followed. Due to the design of the substation one side of the disconnect remains energized while the other side is de-energized. The work is to be performed on the de-energized side of the 115 kV disconnect switch, however, grounds are difficult to install on the de-energized side of switch; doesn’t OSHA 1910.269 (n)(2) allow workers to install a barrier between the energized and de-energized side of the 115 kV disconnect switch, circumventing the need for grounds on the de-energized side?
A: There are two parts to each of your questions. The first is the “Minimum Approach Distance” MAD for qualified electrical workers, and the second part of the question is whether grounding is required in all cases for worker protection.
The first question asks if workers can isolate a lateral tap off a main line by opening the lateral tap’s cutout and work the line without grounds. Let’s take the example of a 7.2 kV single-phase lateral tap, off a 12.47 kV three-phase line. The workers open the cutout leaving one side of the cutout energized. The workers get a clearance per paragraph (m), and properly ground the line using the equipotential grounding (EPZ) method. However, even with the line de-energized per paragraph (m) and EPZ grounded, the workers cannot position themselves or work within the MAD distance (2' 3") from the hot side of the cutout, even if the conductor you are working is grounded. The other option for the workers is the example below:
Qualified workers need to work within the MAD distance (2’ 3”) of the high-side of an energized 7.2 kV cutout. They ground the de-energized portion of the switch or attached conductor, then cover the energized side of the cutout and all exposed energized conductors or equipment within the MAD distance of the work area; thus removing the MAD distance.
There is other option for qualified workers needing to work within the MAD distance (2’ 3”) of the high-side of an energized 7.2 kV cutout. The workers can ground the de-energized portion of the switch or attached conductor, then cover (with approved cover-up material rated for the voltage involved) the energized side of the cutout and all exposed energized conductors or equipment within the MAD distance of the work area; thus removing the MAD.
If the workers are going to leave one side of the cutout energized they need to inspect the cutout and make sure the cutout is in good electrical and mechanical condition. If the workers have any concern about the condition of the cutout they should de-energize both sides of the cutout, and it is always best to lift the cutout's hot tap if possible.
In the second question workers are going to work on a horizontal 115 kV disconnect switch. The switch is open, tagged for the worker(s) and locked open per paragraph (m). One side of the disconnect switch is de-energized and grounded. But, the other side of the switch is still energized, or de-energized and not grounded. Workers can work on the grounded side of the disconnect switch, however, the worker(s) must keep their MAD distance (4' 3") from the energized, or un-energized and not grounded, side of the disconnect switch. Workers could comfortably work on the grounded side of the disconnect switch, say 5' from the energized, or un-energized and not grounded part of the switch. There are no insulating barriers available, and approved in the industry, for voltages above 46 kV and some cases 69 kV phase-to-phase. Thus no barriers are available for use in this work method at 115 kV.
In the second part of both questions OSHA 1910.269(n)(2) is really referring to a line; a good example is a new line being built. If the line is built in the middle of a field where there are no other electrical lines crossing over or under, no backfeed possible, and no induction possible; you do not have to ground. Let’s say workers want to build a five span tap off an existing line. The workers could build the entire line, less the first span from the tap pole, to the first new pole. If there are no physical or electrical tie to the tap pole, the tap line could be built without grounds. Or, workers could build an underground line extension without grounds if they do not connect the secondarys to the new houses (eliminating the possibility of back feed) and leaving the tap from the existing line physically disconnected (not made up or able in any way to become energized, and this includes the neutral).
Now to answer the second question; workers want to work on one side of an 115kV disconnect switch located in a substation. The workers open the switch and want to work on the de-energized side of the switch without grounds. First, qualified workers cannot, at anytime work on the de-energized side of the disconnect switch if the work location is within 4'3" from the energized portion of the switch, even if the workers have grounds on the de-energized portion of the disconnect switch. And, there is no cover-up made to remove MAD at 115kV. If workers need to work the de-energized side of the disconnect switch, say replace the contacts, workers will have to de-energize both sides of the switch. The normal manufactured clearances of 115kV disconnect switches, pole-to-pole, do not give workers the needed MAD distance. Can a worker work on the de-energized side of the bus ten (10) feet from the 115kV disconnect switch without grounds? At ten (10) feet the worker no longer has a MAD distance problem; but do I need to ground the bus at this point? OSHA 1910.269(n) asks; have you followed the provisions of paragraph (m)? Yes, the worker has a clearance on the switch to the end of the bus. Can the bus become energized in anyway? No, there are no other conductors or devices connected to the bus, crossing over or under the bus, and there are no other electrical connections of any kind. Could the switch come closed? No, I have locked it open and have a clearance. Is there any induction generated in the area? No none at all. Is the application of grounds impracticable or hazardous? Yes, it is both impracticable and very hazardous to install grounds. You do not need ground!
HOWEVER, if I am an inspector, a safety professional, or another qualified worker, a qualified worker is going to have to show me that the switch is in good mechanical and electrical condition, there are no other devices connected to the bus (PTs, CTs, transformers, etc.), there are no other lines that cross over or under, that could fall onto the bus, and there is no induction generated in the work area. AND, the installation of grounds are impracticable or hazardous. You may be able to meet all the items above, but is it really impracticable or hazardous to ground the bus. If it is possible to get a ground on the bus, and can be installed safely, YOU MUST GROUND!
I know of very, very, very few areas that I could agree that it is impracticable or hazardous to ground. That is why the Chance Company and the others come out with new ground clamps, new stud connectors and new grounding equipment. All this equipment removes the "impracticable or hazardous" defense.
Q: When working on de-energized transmission lines with a bucket truck, and the proper PPG is placed on the lines with the truck grounded, should an additional PPG conductor be attached from the truck's bucket to the line (to essentially jump around the man in the bucket)?
A: Thanks for your question. If you are using an insulated bucket truck, insulated for the voltage involved, and you have developed an equipotential zone (EPZ) at the worksite, you do not need to ground the bucket itself. I would recommend that the chassis be grounded to the best available ground source.
If you are using an un-insulated bucket truck and you have developed an EPZ at the worksite, you must install a jumper between the bucket and the conductor being worked. I would again recommend that the chassis also be grounded to the best available ground source.
Q: Attached is a drawing of a question that was brought up about the possibilities of circulating current on 115kv lines when installing
personal grounds when you have another 115kv line running parallel and then
crossing over the line you're working on.
A: Great question. There is probably not a great change of circulating current since the lines parallel for only a mile. But, I have learned to never say never when it comes to circulating current. The distance between Line A and Line B, and the current being carried in Line B will impact the circulating current in Line A. If Line A and Line B are within the same corridor and B is carrying 500 plus amps there could very possibly be circulating current due to the grounding procedure being used on Line A.
A simple solution to this problem is to open the ground switch(s) on Line A. The ground switches provide no protection for workers working on Line A. The crew should then only ground at one location (the work site) with EPZ. Grounding on either side of Line B crossing again provides no worker protection.
The best protection and simplest process is to ground at each work location using the equipotential grounding method and ground no where else.
There was an interesting accident in California recently where a transmission line had been de-energized, the ground switch at the station had been closed, grounds installed at the work site, and the station breaker closed accidentally. After the accident they re-enacted the accident and measured 9,000 Amps at the work location with the ground switch closed at the sub. So much of ground switches.
Q: On an existing 13.2 line: they are taping off the existing line to a new line. The new primary and new neutral are both caught off on insulating hoists with a fiberglass extension stick. Both tails are tied back and taped. Can they work this extension with leather gloves or is single point required?
A: Great Question! Yes, this is a perfect example where grounding is not required. Now, I am assuming that the new line does not have any change of backfeed from transformers connected to homes or businesses. Gloves are all that is needed in this case except the usual PPE.
Q: A 7200 V single-phase conductor and neutral, between pole four and pole five, has been broken mid-span by a tree and both conductors are lying on the ground. The crew has installed a set of working grounds between pole three and pole four, and a set of working grounds between pole five and pole six (working grounds are properly sized grounding cables and grounding clamps installed between the neutral and phase conductor(s).) Equipotential grounding practices have not been used (a cluster bar and a grounding jumper from the cluster bar to the neutral installed on both poles ) on this job. A bucket truck will be used to raise the conductors into place and spliced back together. Can the crew safely, and legally, re-install the conductors using only working grounds and wearing Class 2 rubber gloves?
A: Yes! This is an acceptable way to install conductors broken mid-span. In fact, equipotential grounding only protects workers positioned on the same pole as the equipotential zone. Workers not located on this pole have no protection unless they wear rubber gloves rated for the system's voltage. When workers are not in this equipotential zone of protection, rubber gloves rated for the system's voltage are one way to protect themselves when contacting phase or neutral conductors.
The other method of protecting workers contacting downed lines is by installing grounding jumpers on either side of the break and installing an equipotential grounding mat at the location where the workers will be standing and contacting the conductors. This equipotential grounding mat must be installed to the conductors on both sides of the break.
Equipotential grounding provides protection only for workers positioned within the equipotential zone. The equipotential zone is developed by installing a cluster bar below the working position, a grounding jumper is installed between the cluster bar and neutral and grounding jumpers installed between the neutral and phase conductor(s).
Federal OSHA 1910.269(n)(3) and ALL state laws require the use of equipotential grounding methods on de-energized lines and devices, or workers must insulate or isolate themselves from the conductors and devices. If workers choose to use the rubber gloving method in states having a 5000 V, maximum, rubber gloving rule, workers must first install grounding jumpers between the phase and neutral on the conductors to be worked. Remember, however, if you choose to NOT use the equipotential grounding method, but simply the grounding jumpers and the gloving method, you must fully comply with ALL rubber gloving work methods and practices when conducting this work.
We hear comments from workers who say "The grounds are a pain," or "Grounds always get in the way," or "If the line is tagged and grounded on both sides, we are safe." Try telling that to the 50 plus United States journeymen linemen who died in 2002 when they also thought grounds were a pain, or they get in the way, or grounds on both sides are enough. The equipotential law is there for a reason, IT SAVES LIVES.
Q: At a PUD's general safety meeting recently, we heard a question asked about the new DOT laws that have been pulled back a little. You know, the ones where two tickets for illegal lane change, tailgating, etc., would result in loss of CDL for 60 days, etc. The guy who asked didn't understand that the employee's responsibility to report all traffic convictions was not affected by the proposed law.
A: Some people want to look for a loophole because they feel like their privacy is being invaded.
I want to clarify about having to report moving violations to the PUD. The Federal Motor Carrier Safety Regulations, Subpart C, Paragraph 383.31 explains the reporting procedure for motor vehicle violations. It requires CDL drivers to report within 30 days any violations other than parking tickets to their employer. It doesn't matter if the violation happened in the state where you have your license or not.
At the time I said it was PUD policy, but the more I thought about it, the more I remembered that there was a regulation that addresses it.
Stephen P. Frost, Director of Field Operations, ESCI
Q: What portion of an extendo stick can I consider insulated? Can I assume the entire stick will insulate from energized lines?
A: Telescoping (Extendo) stick testing and protection. Extendo sticks are tested from the factory for the entire length of the stick, but once they are put into service, the hollow sections of the stick may become contaminated and the only advertised protection from the stick is in the last foam-filled section of the stick. The stick must be not be used as a hot tool below the foam-filled section. The stick needs to be cared for in the same way we care for all sticks, i.e., it needs to be wiped and inspected before using, especially the foam-filled section. When you do in-service testing, the foam-filled section of the stick must pass. Even if you clean the outsides of the hollow sections, there is no guarantee that the impurities inside these sections will not track.
As with all hot tools, don't use extendo sticks beyond their electrical and mechanical capacities.
Q: I am a Safety and Training Instructor with the Virginia Association of Electrical Co-ops. I have two important questions that I feel you might be able to help me with.
2. The pole ground wire does help somewhat. In my studies in the 1980s I found that the pole ground when stretched tight and in full contact with the pole helped somewhat. However, when we added the cluster bar we got a substantial reduction in voltage across the worker. As the pole is in the ground the pole ground gets loose and does not make good contact with the pole as the pole dries out and shrinks. Also, what if the pole ground gets broken or has a loose connection at the neutral.
Great questions. Thanks, Brian
Q: If you're working a de-energized 230 kV transmission line, two miles from the substation, using the equipotential grounding procedure (jumpering the three phases to a cluster bar and developing an equipotential zone), how do you protect workers on the ground from step and touch potentials?
A: You should keep workers on the ground a minimum of 15 feet from the bottom of the structure and any driven ground rod. The use of insulated footwear is also something you might what to consider for everyone on the ground.
The use of equipotential grounding does not increase the danger for workers on the ground when compared with the old system of grounding. The hazard has always been there for ground workers and continues using equipotential grounding. In the old grounding system workers jumpered the phase conductors together, then jumpered to a static, or a temporarily driven ground rod. In using the static the structure may have a pole ground which becomes part of the grounding system and creates step and touch potentials. The use of a temporary ground rod also allowed fault current to be "dumped" into the ground near workers on the ground.
Step potential is developed when fault current enters earth at the ground level of a structure, pole, or ground rod. The fault current traveling into the earth at that point wants to travel back to the generating source and will take many paths. The fault current dissipates in all directions from the structure, pole, or ground rod and becomes less intense as it is able to dissipate in all directions from the structure, pole, or ground rod. Very near the structure, pole, or ground rod the current is high and the fault current traveling through earth, times the resistance of earth, develops step potential. When a worker is standing a distance away (15 feet or more) from the structure, pole, or ground rod, the fault current is able to dissipate greatly and the current at that point, times the resistance of earth, will develop lower step potential compared with the step potential very near the structure, pole, or ground rod.
Is the magic number 15 feet? No. I depends on the fault current and resistance of earth at the work location. Many utilities use 15 feet or more for transmission voltages depending on their system design and operating methods.
If the structure is steel, the tower will be tied into the equipotential zone. The base of the tower and the footing grounds can develop high step and touch potentials. Workers should remain a distance away for the base of the tower. If the structure is wood, the pole(s) will also be tied into the equipotential zone. The pole will also create step and touch potential hazards for the workers due to pole grounds and the conductivity of the pole. If a ground rod is used to ground the line, it should be installed a distance from the base of the pole or structure, and away from workers on the ground. Studies have shown that installing the ground rod a span away from the work location may lower step potentials in some cases.
Q: If a qualified operator is operating a highway digger with a steel mast and they do not ground the truck, do the overhead lines need to be covered? How close can the truck be operated to the overhead lines?
A: OSHA 1910.269 (p) Mechanical Equipment, requires that when any mechanical equipment (highway digger) is operated near energized lines the operator must do one or more of the following:
1. The energized line shall be cover with protective materials (cover-up), or
a. All equipment shall be bonded together, and
Now what does this all mean in relation to your question? A highway digger does not have an insulated portion of the boom so option 2 is out. The line can be covered as stated in option 1. Enough cover-up must be installed so that the boom of the highway digger cannot get within the minimum approach distance (MAD) of the energized line.
Your second question: how close can the boom get to an energized line? Section P states that protection must be taken if the boom could contact the energized line. You did not give me the voltage of the line, so I will assume we are talking about a system below 50 kV. Some type of protection shall be used when the boom is operated within the distances of OSHA 1926.550(a)(15), the 10-foot rule.
Now Section P is all messed up. It states that if you ground you must also use ground mats, and insulated protective equipment, or barricades. It should read if you ground you must use ground mats, or insulated protective equipment, or barricades. ESCI is working with Mr. Dave Wallis, Federal OSHA, to fix this section as part of the revision of OSHA 1926.
To answer your question if you do not want to ground, and a highway digger does not have an insulated boom section, the only option you have is the use of insulated cover-up whenever the highway digger is operated within 10 feet of a 12 kV energized overhead line.
Q: Do I need to ground my insulated bucket truck when working near energized lines and equipment?
A: OSHA 1910.269 (p) Mechanical Equipment states "Mechanical equipment shall be operated so that the minimum approach distance of Table R-6 through R-10 are maintained from exposed energized lines and equipment. However, the insulated portion of an aerial lift operated by a qualified worker in the lift is exempt form this requirement."
This paragraph means that if your bucket truck is insulated, tested for the voltage involved, and operated by a qualified worker in the bucket, you do not need to ground, barricade, or take any other steps to protect workers on the ground. However, you must ensure that the un-insulated portion of the truck does not get within the minimum approach distance (MAD). You can position the insulated boom up to, but not touching, the exposed lines or equipment. Also remember the qualified worker in the bucket cannot enter MAD (the minimum approach distance) unless insulated protective equipment is used.
Now that's the law, if your utility requires you to ground the bucket truck this could add extra protection for workers on the ground. In all the years I have been involved with grounding, I have never heard of anyone killed or hurt around a properly grounded truck.
Q: If I am going to ground my truck, what do I ground it to? Do I need to take additional steps besides just grounding?
A: Tests conducted at the A.B. Chance Labs, and published in IEEE 91 SM 312-9 PWRD, showed the best protection for workers on the ground, around trucks, occurred when the truck was grounded to the neutral. Grounding the truck to a driven ground rod provided no protection. The eight-foot ground rod was driven in to undisturbed soil a full eight feet and the ground resistance was measured to be 18 ohms.
Q: When do hot sticks need to be tested?
A: ( j ) (2) (ii) If any defects or contamination that could adversely affect the insulating qualities or mechanical integrity of the live-line tool is present after wiping, the tool shall be removed from service and examined and tested according to paragraph ( j ) (2) (iii) of this section before being returned to service.
29CFR1910.269 ( j ) (2) (iii) Live-line tools used for primary protection shall be removed from service every two years and whenever required under paragraph ( j ) (2) (ii) of this section for examination, cleaning, repair, and testing as follows:
( j )(2) (iii) (A) Each tool shall be thoughly examined for defects
( j ) (2) (iii) (B) If a defect or contamination that could adversely affect the insulating qualities or mechanical intergrity of the live-line tool is found, the tool shall be repaired and refinished or shall permanently removed from service. If no such defect or cintamination is found, the tool shall be cleaned and waxed.
Most utilities in the Northwest have their live-line tools inspected and tested within the two year period. ESCI advocates this practice which is more stringent than the regulation.
Remember the live-line tools need to be removed from service every two years and must be inspected. In order to verify this inspection the individual tools need to be identified (marked) in some manner.
If you have a question you would like answered by the Safety Fireman,
Email email@example.com with Question for Safety Fireman in subject line.
© ESCI, Inc. 2018 | Providers of Safety, Training, and Consulting Services | all rights reserved. ESCI home page