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I just learned the National Electrical Safety Code (NESC) excludes utility poles with heights above ground of 60 ft or less from the extreme wind loading design requirements. Is this exclusion supported by data? If not, what will it take to change? This may be a case of commercial considerations overriding good design practice. In that case, those pushing the exclusion should test drive an extended period without power to see if the exclusion really makes sense. I

Extreme wind loading is covered by Rule 250C in the NESC. Per the 2023 NESC Handbook:  Rule 250C was added in 1977 and recognizes that tall structures may be subjected to wind only loadings that exceed the combined ice and wind loadings included in Rule 250B. ASCE Manual 52, Guide for Design of Steel Transmission Towers, was one of the references used in this change. This change was made to specifically recognize that the heavy- and medium-loading conditions of Rule 250B do not properly reflect the actual loads applied by wind to structures higher than 18.3 m (60 ft) that carry conductors of 2 cm (0.8 in.) diameter or greater. There are additional details in the handbook as well.

For more information on the NESC, which is an IEEE publication, see the links below on how to participate and submit change requests.

• NESC Program Page
• 2028 NESC Change Proposal and Revision Schedule

I just learned the National Electrical Safety Code (NESC) excludes utility poles with heights above ground of 60 ft or less from the extreme wind loading design requirements. Is this exclusion supported by data? If not, what will it take to change? This may be a case of commercial considerations overriding good design practice. In that case, those pushing the exclusion should test drive an extended period without power to see if the exclusion really makes sense. I

What is the logic for the 60 ft or greater? Most utility poles are less than 60 ft.

Extreme wind loading is covered by Rule 250C in the NESC. Per the 2023 NESC Handbook:  Rule 250C was added in 1977 and recognizes that tall structures may be subjected to wind only loadings that exceed the combined ice and wind loadings included in Rule 250B. ASCE Manual 52, Guide for Design of Steel Transmission Towers, was one of the references used in this change. This change was made to specifically recognize that the heavy- and medium-loading conditions of Rule 250B do not properly reflect the actual loads applied by wind to structures higher than 18.3 m (60 ft) that carry conductors of 2 cm (0.8 in.) diameter or greater. There are additional details in the handbook as well.

For more information on the NESC, which is an IEEE publication, see the links below on how to participate and submit change requests.

• NESC Program Page
• 2028 NESC Change Proposal and Revision Schedule

I just learned the National Electrical Safety Code (NESC) excludes utility poles with heights above ground of 60 ft or less from the extreme wind loading design requirements. Is this exclusion supported by data? If not, what will it take to change? This may be a case of commercial considerations overriding good design practice. In that case, those pushing the exclusion should test drive an extended period without power to see if the exclusion really makes sense. I

I just learned the National Electrical Safety Code (NESC) excludes utility poles with heights above ground of 60 ft or less from the extreme wind loading design requirements. Is this exclusion supported by data? If not, what will it take to change? This may be a case of commercial considerations overriding good design practice. In that case, those pushing the exclusion should test drive an extended period without power to see if the exclusion really makes sense. I

I have worked for your local wires provider in Houston for a little over 50 years designing T-Line structures when it was HL&P. I know a few people on the NESC and the consensus from the structural folks on the committee is the EE's on the committee vote down any attempt to remove the 60' exemption. Their rationale is the wind-borne debris wraps around the wire and brings the poles down. This is anecdotal remarks from a few EE's at the company and may not be a national reason. The NESC is not a design standard although many treat it as one. It is a public safety document meant to protect the public from our wires. ASCE MOP 74 covers wind loading and is currently being considered to be elevated to an ASCE Standard.

IMHO, The 60' exemption was put in to make the poles cheaper and the electric cost lower. There is no viable reason to not consider wind below 60' other than economics. Trees and debris cause the majority of damage to wood distribution poles and pure wind accounts for little damage. 

In Texas, the PUC/ERCOT deregulated utilities so you can switch providers and the local utility gets a few cents per KWH to maintain the poles and wires. In Houston the rate is currently 4.04¢ per KWH plus the 10¢ to 15¢ the generators charge. I think the rate for power in California is around 50¢. 

Could the NESC revoke the 60' exemption? Sure. Will it make much difference? Probably not. What amount of load should a distribution pole be required to handle? Will an extra 4x8 sheet of plywood added to the pole or wire be enough?  How about 5 or 6 sheets? The roof of an apartment carport can be 20' x 100', so do we design for that wind area? Trees falling onto lines are the major problem. The new NESC Rule 250C uses a 100-year MRI wind map from ASCE 7-16.

The Texas Governor had a news conference and mandated that we cut or trim all trees that could impact any wires. The 100' tall tree on your property that is just outside our easement would have to be cut down or trimmed where there is no possibility of it touching the wire. Are property owners willing to allow us to cut down trees? Likely not. 

Hurricane Beryl caused over 2 million meters to stop spinning on July 8 and many were out for several days while tree trim crews worked to clear lines. The T-Line system lost around 14 wood poles which were replaced in a couple of days. Power was re-routed and almost all substations were energized by the 138kV and 345kV lines feeding them. The huge issue was all the trees in the distribution wires.

Your next question will be, just put everything underground. This is an option but is more costly than overhead and much more difficult to repair when someone digs into the cable. We buried a 138kV circuit along I-10 west when the freeway needed our land. The extra cost was paid by TXDOT. The cost factor was about 20 times more than typical overhead construction. I don't work in distribution and their added cost factor is likely lower.

The above opinions are my own and not my employers. I'm an old structural engineer that designs towers and substation structures.  The bottom line is, how much extra are you and your neighbors willing to pay for power? Are you willing to cut down your trees, so you have uninterrupted power? 

Hurricane Beryl was projected to hit 300 miles away 2 days before it hit Houston. 

I just learned the National Electrical Safety Code (NESC) excludes utility poles with heights above ground of 60 ft or less from the extreme wind loading design requirements. Is this exclusion supported by data? If not, what will it take to change? This may be a case of commercial considerations overriding good design practice. In that case, those pushing the exclusion should test drive an extended period without power to see if the exclusion really makes sense. I

Thank you for your candid and informed response! Having lost my power from Hurricane Beryl due to a fallen tree on a line tied to our circuit breaker, I have first-hand experience with this risk. I think an integrated study of transmission system structural resilience 2is needed, including civil, mechanical, and electrical engineering disciplines. This needs to be a practical and data-driven effort. Such a study could inform the public, regulators, and transmission system owners about recommended changes considering the bang for buck. Everything I have read about putting the lines underground indicates this is not a practical or economically feasible solution to replace existing overhead lines.

I have worked for your local wires provider in Houston for a little over 50 years designing T-Line structures when it was HL&P. I know a few people on the NESC and the consensus from the structural folks on the committee is the EE's on the committee vote down any attempt to remove the 60' exemption. Their rationale is the wind-borne debris wraps around the wire and brings the poles down. This is anecdotal remarks from a few EE's at the company and may not be a national reason. The NESC is not a design standard although many treat it as one. It is a public safety document meant to protect the public from our wires. ASCE MOP 74 covers wind loading and is currently being considered to be elevated to an ASCE Standard.

IMHO, The 60' exemption was put in to make the poles cheaper and the electric cost lower. There is no viable reason to not consider wind below 60' other than economics. Trees and debris cause the majority of damage to wood distribution poles and pure wind accounts for little damage. 

In Texas, the PUC/ERCOT deregulated utilities so you can switch providers and the local utility gets a few cents per KWH to maintain the poles and wires. In Houston the rate is currently 4.04¢ per KWH plus the 10¢ to 15¢ the generators charge. I think the rate for power in California is around 50¢. 

Could the NESC revoke the 60' exemption? Sure. Will it make much difference? Probably not. What amount of load should a distribution pole be required to handle? Will an extra 4x8 sheet of plywood added to the pole or wire be enough?  How about 5 or 6 sheets? The roof of an apartment carport can be 20' x 100', so do we design for that wind area? Trees falling onto lines are the major problem. The new NESC Rule 250C uses a 100-year MRI wind map from ASCE 7-16.

The Texas Governor had a news conference and mandated that we cut or trim all trees that could impact any wires. The 100' tall tree on your property that is just outside our easement would have to be cut down or trimmed where there is no possibility of it touching the wire. Are property owners willing to allow us to cut down trees? Likely not. 

Hurricane Beryl caused over 2 million meters to stop spinning on July 8 and many were out for several days while tree trim crews worked to clear lines. The T-Line system lost around 14 wood poles which were replaced in a couple of days. Power was re-routed and almost all substations were energized by the 138kV and 345kV lines feeding them. The huge issue was all the trees in the distribution wires.

Your next question will be, just put everything underground. This is an option but is more costly than overhead and much more difficult to repair when someone digs into the cable. We buried a 138kV circuit along I-10 west when the freeway needed our land. The extra cost was paid by TXDOT. The cost factor was about 20 times more than typical overhead construction. I don't work in distribution and their added cost factor is likely lower.

The above opinions are my own and not my employers. I'm an old structural engineer that designs towers and substation structures.  The bottom line is, how much extra are you and your neighbors willing to pay for power? Are you willing to cut down your trees, so you have uninterrupted power? 

Hurricane Beryl was projected to hit 300 miles away 2 days before it hit Houston. 

I just learned the National Electrical Safety Code (NESC) excludes utility poles with heights above ground of 60 ft or less from the extreme wind loading design requirements. Is this exclusion supported by data? If not, what will it take to change? This may be a case of commercial considerations overriding good design practice. In that case, those pushing the exclusion should test drive an extended period without power to see if the exclusion really makes sense. I