Guy Wire Calculations

[DMG_1]

Hi All.

I have a question for you. I am working on a project where we are replacing a medium voltage stringer and a utility pole.

The pole is going to be Southern Yellow Pine, Class 3, 45'.
The medium voltage stringer is going to be 3-phase, #2 AWG ACSR Beech with an RBS of 3458 pounds.
I am looking at guy wire calculations and have determined the "Fully Loaded Design Tension" based on #2 AWG ACSR, "Horizontal Pull", and "Guy Resultant Tension".


How do I relate this to the utility pole? I would assume there is a calculation or specification indicating if the utiltiy pole itself could support the load of the conductors and maybe not require a guy wire.

Thanks,
Dave

 

[Terrier]

Guying Calcuations

Guying Calcuations

It is not said, but it sounds like your application would fall under NEC Article 399, Outdoor Overhead Conductors over 1000 Volts, which basically passes the requirements over to the authority having jurisdiction (399.30(B)).

In most jurisdictions those authorities will require design work be in accordance with The National Electrical Safety Code.

 

[mgookin]

Hi All.

I have a question for you. I am working on a project where we are replacing a medium voltage stringer and a utility pole.

The pole is going to be Southern Yellow Pine, Class 3, 45'.
The medium voltage stringer is going to be 3-phase, #2 AWG ACSR Beech with an RBS of 3458 pounds.
I am looking at guy wire calculations and have determined the "Fully Loaded Design Tension" based on #2 AWG ACSR, "Horizontal Pull", and "Guy Resultant Tension".


How do I relate this to the utility pole? I would assume there is a calculation or specification indicating if the utiltiy pole itself could support the load of the conductors and maybe not require a guy wire.

Thanks,
Dave

I would think you need the physical properties/ load rating of the pole which you should be able to get from the supplier or manufacturer.

 

[Iron_Ben]

Hi All.

I have a question for you. I am working on a project where we are replacing a medium voltage stringer and a utility pole.

The pole is going to be Southern Yellow Pine, Class 3, 45'.
The medium voltage stringer is going to be 3-phase, #2 AWG ACSR Beech with an RBS of 3458 pounds.
I am looking at guy wire calculations and have determined the "Fully Loaded Design Tension" based on #2 AWG ACSR, "Horizontal Pull", and "Guy Resultant Tension".


How do I relate this to the utility pole? I would assume there is a calculation or specification indicating if the utiltiy pole itself could support the load of the conductors and maybe not require a guy wire.

Thanks,
Dave

Need more info to answer confidently. Span length(s), ruling span calculations, pole framing details, attachments if any, soil type and lots more. My rule was in a close case, always install an anchor and guy. Sometimes we'd install a short three phase tap, say 100' of 1/0 or #2, and not guy it. It would look fine at installation. Come back a year or two later and the conductor sag would be alarming. Better to pull it tight and install the anchor and guy.

 

[mivey]

Hi All.

I have a question for you. I am working on a project where we are replacing a medium voltage stringer and a utility pole.

The pole is going to be Southern Yellow Pine, Class 3, 45'.


The medium voltage stringer is going to be 3-phase, #2 AWG ACSR Beech with an RBS of 3458 pounds.
I am looking at guy wire calculations and have determined the "Fully Loaded Design Tension" based on #2 AWG ACSR, "Horizontal Pull", and "Guy Resultant Tension".


How do I relate this to the utility pole? I would assume there is a calculation or specification indicating if the utiltiy pole itself could support the load of the conductors and maybe not require a guy wire.

Thanks,
Dave

I am going to assume this is a single dead-end pole. I will also assume you don't have much other load on the pole (like transformers, etc.) as that will make what I'm about to tell you worse. I'll also make some assumptions about the conductor and guying lay-out unless you want to provide more detail. I'll also assume 4 conductors. I'll also assume class C construction in a heavy loading district.

1) A class 3 pole is probably too small unless you are going to keep the conductor design tension to about 1,000 lbs or less.

2) A 1,000 lb design tension would require a class H2 pole to be guy-less. The problem is with poor soil the pole needs to be about 12 ft deep so now you might need a 55 ft pole. For average soil you would need a 10 ft depth and a 50 ft pole. For good soil the 45 ft class H2 would probably work.

3) 2,000 lbs of design tension (a reasonable number for the high end) would require a class 1 pole.

4) A 2,000 lb design tension would require a concrete pole (there is no "H7") to be guy-less. The problem is with poor soil the pole needs to be about 13.5 ft deep so now you might need a 55 ft pole. For average soil you would need a 11 ft depth and a 50 ft pole. For good soil the 45 ft class "H7" would need to be 8 ft deep so you need a 50 ft pole. Also, you need to consider soil-bearing for a concrete pole.

With more detail we can give you a better answer.