Lashing power lines

[grasfulls]

I have seen this a lot of times "Incoming power cables should be lashed together, and they should be secured to the structure at least every four feet." Is there a definitive resource for type/style of lashing relative to potential inrush currents and/or seismic movement?

 

[beanland]

AFC Lashing

AFC Lashing

At high available fault current, typically over 65kA, lashing of lines is recommended to prevent movement during faults. In days gone by, lashing would be with waxed cord, these days nylon wire ties. Lashing of overhead lines to a messenger (if not triplex) is required to support the conductors.

 

[jim dungar]

At high available fault current, typically over 65kA, lashing of lines is recommended to prevent movement during faults. In days gone by, lashing would be with waxed cord, these days nylon wire ties. Lashing of overhead lines to a messenger (if not triplex) is required to support the conductors.

I have never seen a UL Listed piece of equipment that said to use 'nylon cable ties', everyone requires rope.
See page 10.
http://w3.usa.siemens.com/us/intern...hboards/Media/SB Installation Guide Final.pdf

Almost every electrical contractor uses cable ties. The last project where I spec'ed rope, the contractor valued engineered in cable ties, and used it as a means to show how I was interested in 'being an engineer' rather than getting the customer back into service.

 

[beanland]

Per Manufacturer Instructions

Per Manufacturer Instructions

Agreed, it always has to be per manufacturer instructions.

However, is there any technical reason that lashing cannot be done using appropriate nylon wire ties?

 

[jim dungar]

Agreed, it always has to be per manufacturer instructions.

However, is there any technical reason that lashing cannot be done using appropriate nylon wire ties?

Tensile Strength would be my guess.

 

[gadfly56]

Agreed, it always has to be per manufacturer instructions.

However, is there any technical reason that lashing cannot be done using appropriate nylon wire ties?

Embrittlement over time. One of the dirty little secrets about plastics is that the polymerization reaction that forms them never stops. High quality products contain additives designed to "quench" the reaction at the desired point, but usually something continues. Over time, there is more and more chain crosslinking which makes the plastic stiffer and more brittle. Early in life, the nylon will stretch, absorbing the lash energy. Later, there may not be enough give in the plastic and it shatters under the impulse load.

 

[grasfulls]

The manufacturer's engineer is not sure what it means...yet

The manufacturer's engineer is not sure what it means...yet

Agreed, it always has to be per manufacturer instructions.

However, is there any technical reason that lashing cannot be done using appropriate nylon wire ties?

I agree that it should be per the manufacturer. I have a building inspector who wants to see the installation instructions for the gear. Step 5 is to lash the power lines. I called the manufacturer and got the engineer for the particular line of gear and he is not sure about the lashing, he is supposed to get back to me. There are a few other closed threads in here on the same subject, but never a definitive answer with respect to exactly what the lashing should be relative to the AIC. One would think that regardless of the manufacturer, by now there would be an engineered standard for the point at which lashing should take place AND, relative to the potential fault level, how the lashing should be done and with what.

I have seen some massive wraps of rope, I just wonder where they got the detail from.

Thanks!

 

[grasfulls]

Plastic/Nylon breaking

Plastic/Nylon breaking

Embrittlement over time. One of the dirty little secrets about plastics is that the polymerization reaction that forms them never stops. High quality products contain additives designed to "quench" the reaction at the desired point, but usually something continues. Over time, there is more and more chain crosslinking which makes the plastic stiffer and more brittle. Early in life, the nylon will stretch, absorbing the lash energy. Later, there may not be enough give in the plastic and it shatters under the impulse load.

Do not many types of rope degrade over time as well? Might this then evolve into "if cotton rope is used, relash every 7 years" or some other means to mitigate potential liability over lashing failure? That would be sort of neat, I could finally have electrical work where I have to go back, like a painter.

 

[jim dungar]

I have seen some massive wraps of rope, I just wonder where they got the detail from.

There are many ways to lash conductors, some of it will depend on the spacing between them.
The skills are very basic, any Boy Scout that earned his Pioneering meri badge has learned the basics.
Every manufacturer, that has listed equipment that might need lashing, has diagrams as part of their instructions.

I believe you can find a diagram in an Ugly's book.

Lashing requirements are part of SCCR ratings and are based on available fault current (SCA), so may be needed with equipment that does not have an AIC rating, such as meter sockets and terminal compartments.

 

[grasfulls]

Great reference

Great reference

I have never seen a UL Listed piece of equipment that said to use 'nylon cable ties', everyone requires rope.
See page 10.
http://w3.usa.siemens.com/us/intern...hboards/Media/SB Installation Guide Final.pdf

Almost every electrical contractor uses cable ties. The last project where I spec'ed rope, the contractor valued engineered in cable ties, and used it as a means to show how I was interested in 'being an engineer' rather than getting the customer back into service.

The installation reference you provided is great, thank you. Those images are exactly what I remember seeing before. I see that the first lashing example is for 65kA, do you know if this means there is no need to lash if available inrush is less than 65kA.

 

[grasfulls]

Nylon Rope

Nylon Rope

I have never seen a UL Listed piece of equipment that said to use 'nylon cable ties', everyone requires rope.
See page 10.
http://w3.usa.siemens.com/us/intern...hboards/Media/SB Installation Guide Final.pdf

Almost every electrical contractor uses cable ties. The last project where I spec'ed rope, the contractor valued engineered in cable ties, and used it as a means to show how I was interested in 'being an engineer' rather than getting the customer back into service.

Plus, it specifically states "nylon rope" as well as the size....great doc! I would like to think, since this is an engineered specification, it holds true for any installation regardless of manufacturer. It would be great if there were an agency that creates the spec to which all manufacturers would then cite as the proper installation method. This would alleviate every manufacturer coming up with their own method. Maybe we can start one...lashing.com? Another bureaucratic layer.

 

[grasfulls]

UGLY's and at meter sockets too

UGLY's and at meter sockets too

There are many ways to lash conductors, some of it will depend on the spacing between them.
The skills are very basic, any Boy Scout that earned his Pioneering meri badge has learned the basics.
Every manufacturer, that has listed equipment that might need lashing, has diagrams as part of their instructions.

I believe you can find a diagram in an Ugly's book.

Lashing requirements are part of SCCR ratings and are based on available fault current (SCA), so may be needed with equipment that does not have an AIC rating, such as meter sockets and terminal compartments.

I will find an UGLY's book, thank you. However, what if I cheated on the merit badge?

 

[grasfulls]

Lashing typically starts at 65kA

Lashing typically starts at 65kA

At high available fault current, typically over 65kA, lashing of lines is recommended to prevent movement during faults. In days gone by, lashing would be with waxed cord, these days nylon wire ties. Lashing of overhead lines to a messenger (if not triplex) is required to support the conductors.

With respect to the 65kA, what if the gear is rated at 65kA but the available inrush as provided by the utility is less than 65kA? And, before everyone jumps on the AHJ being the final say (yes, I know they are, or perhaps an engineer's annotation that no lashing is required....) I am asking if the requirement for lashing must still be be done so the now in-use assembly is all rated at 65kA? Let's say the inrush is only able to achieve 47kA. I also know this opens the door for "what about 49kA" etc. but there should be a line somewhere that makes lashing a complete non-necessity.

 

[jim dungar]

With respect to the 65kA, what if the gear is rated at 65kA but the available inrush as provided by the utility is less than 65kA?

Most of the literature I have seen talks about lashing for fault currents in excess of 65kA.
Page 29 of this one, has a chart showing that different fault currents and different devices have different results.
http://static.schneider-electric.us...ow Voltage Switchgear/PZ4/80298-002-06_en.pdf

 

[grasfulls]

Lashing at 10kA

Lashing at 10kA

Most of the literature I have seen talks about lashing for fault currents in excess of 65kA.
Page 29 of this one, has a chart showing that different fault currents and different devices have different results.
http://static.schneider-electric.us...ow Voltage Switchgear/PZ4/80298-002-06_en.pdf

I just received an email from an engineer at Eaton:
Our minimum requirements for cable lashing can be found on page 9 of the attached installation manual. This lashing applies to anything over 10kA.

In addition, per NEC Code 230.51(A), service entrance conductors must be “strapped” within 12” of every service head, gooseneck or enclosure connection, and again at intervals of no more than 30” past this first 12” strap. They do not define what “strapping” is so we follow the guideline set in the attached manual.
END ENGINEER QUOTE

Within the pdf he sent me, the dialogue begins with:
Cable bracing instructions
For short-circuit ratings above 10,000A rms, install cable braces
per the following instructions:
END PDF COPY/PASTE

So...it is interesting at least, all the way down to >10000 rms.

The Siemens lashing started at 65kA and went up through 200kA, each diagram as a different style, same size and type of rope, a 3/8" nylon. The Eaton is a tad different:
The material required for the cable braces is 3/8”diameter
nylon rope (note1) or any rope having a minimum tensile strength
of 2,000 pounds (note 2) .
END CITATION

The two notes are manufacturers:
(note 1) Wellington Puritan Mills, Inc., Madison, GA, Catalog Number 10989.
(note 2) Norva Products, Carrolton, GA, Catalog Number TPR12.

 

[don_resqcapt19]

I just received an email from an engineer at Eaton:
...
In addition, per NEC Code 230.51(A), service entrance conductors must be ?strapped? within 12? of every service head, gooseneck or enclosure connection, and again at intervals of no more than 30? past this first 12? strap. They do not define what ?strapping? is so we follow the guideline set in the attached manual.
END ENGINEER QUOTE ...

I don't see how the section cited by Eaton has anything to do with the lashing or supporting of cables inside the enclosure.

 

[grasfulls]

Eaton referenced incorrect page

Eaton referenced incorrect page

I don't see how the section cited by Eaton has anything to do with the lashing or supporting of cables inside the enclosure.

Page 9 sure does not, page 11 has two diagrams for power lines prior to landing on lugs within the enclosure, neither of which is very detailed, the latter being difficult for me to see how the cables are being braced for a fault. I also do not know what "ratings up to 200A" means with respect to anything greater, I am emailing the engineer again. I tried attaching the pdf page of the manual, it exceeded the forum's allowance, but a jpeg worked:

FROM PDF:

All cable conductors of a load circuit are to be bundled together
with five adjacent wraps of rope at distances of 6 inches and 12 inches from the supply terminals
for ratings up to 200A
maximum. (See Figure 20 and Figure 21.)
END PDF

I cannot tell how the lash begins or ends. It actually somewhat highlights the issue with manufacturer's specs versus a generic engineered spec and the problem when an inspector wants the manufacturer's specs to be adhered to. It should not matter whose gear it is, this has nothing to do with the lashing at various fault levels.

 

[don_resqcapt19]

I was refering to their reference to section 230.51(A) of the NEC. It appears to me that they are trying to say that this code section requires the internal lashing. I don't think it has anything to do with lashing inside of the equipment.

 

[grasfulls]

230.51a not apply?

230.51a not apply?

I was referring to their reference to section 230.51(A) of the NEC. It appears to me that they are trying to say that this code section requires the internal lashing. I don't think it has anything to do with lashing inside of the equipment.

Sorry....got lost for awhile. I see what you mean. Perhaps the part about "connecting to a raceway or enclosure"?

 

[Jraef]

http://literature.rockwellautomation.com/idc/groups/literature/documents/in/2100-in012_-en-p.pdf

Pages 44 and 45 show securing cables on incomers using glass filled tape, nylon rope and wood blocks.



When I went through my apprenticeship we used sisal rope, waxed to preserve it. But it's been nothing but nylon rope or Ty-raps since then.