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11/20/06
Question #1:

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:

1. Lines have been de-energized under paragraph (m) of this section.
2. There is no possibility of contact with another energized source.
3. The hazard of induced voltage is not present.”

Doesn’t OSHA 1910.269 (n)(2) allow the worker to work the lateral tap without grounds?

Question #2:

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?

Answer:

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.

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