HV Clearance/OH Lines
- Thread starter jimrubino
- Start date
- Status
jtester
Senior Member
- Location
- Las Cruces N.M.
Re: HV Clearance/OH Lines
If you are under the NEC, refer to 225.60. If under the NESC, Article 232 applies. Unfortunately the NEC rule is terribly inadequate in helping.
The NESC defines conditions of sag and temperature that must be included in determining clearance compliance. It is very difficult to determine if a span has adequate clearance without a sag and tension program to determine sag at the maximum operating temperature of the line. The NEC does none of that.
Jim T
If you are under the NEC, refer to 225.60. If under the NESC, Article 232 applies. Unfortunately the NEC rule is terribly inadequate in helping.
The NESC defines conditions of sag and temperature that must be included in determining clearance compliance. It is very difficult to determine if a span has adequate clearance without a sag and tension program to determine sag at the maximum operating temperature of the line. The NEC does none of that.
Jim T
jtester
Senior Member
- Location
- Las Cruces N.M.
Re: HV Clearance/OH Lines
Jim
I'm not sure if there is a free web site to access. Perhaps someone else can chime in.
Be sure to read all of the clearance section. It will require you to determine the sag at the highest temperature that the line is designed to operate at. This would be conductor temperature, not ambient temperature. After you determine the sag at the highest temperature, you can compare it to the table to see if you comply. The NESC is very thorough in describing how to determine compliance.
You can imagine that on a cold day, the line would have less, maybe lots less, sag than on a hot day, or a day with the conductors heavily loaded.
If you can tell what type of land this line is traversing, someone can post the clearance listed in the Table.
Jim T
Jim
I'm not sure if there is a free web site to access. Perhaps someone else can chime in.
Be sure to read all of the clearance section. It will require you to determine the sag at the highest temperature that the line is designed to operate at. This would be conductor temperature, not ambient temperature. After you determine the sag at the highest temperature, you can compare it to the table to see if you comply. The NESC is very thorough in describing how to determine compliance.
You can imagine that on a cold day, the line would have less, maybe lots less, sag than on a hot day, or a day with the conductors heavily loaded.
If you can tell what type of land this line is traversing, someone can post the clearance listed in the Table.
Jim T
jtester
Senior Member
- Location
- Las Cruces N.M.
Re: HV Clearance/OH Lines
Jim
The rule concerning vehicular traffic is not whether it is likely that vehicles will be passing under, but whether it is possible for vehicles to pass under the line. If a vehicle can physically get under the line, you probably should consider the area subject to vehicular traffic.
That clearance is 18.5 feet from the lowest point of conductor sag under worst case conditions, to the ground below.
If the grade is likely to change in the future, you are also responsible for providing your best guess of what that might be and allow for reasonable changes as well.
Jim
The rule concerning vehicular traffic is not whether it is likely that vehicles will be passing under, but whether it is possible for vehicles to pass under the line. If a vehicle can physically get under the line, you probably should consider the area subject to vehicular traffic.
That clearance is 18.5 feet from the lowest point of conductor sag under worst case conditions, to the ground below.
If the grade is likely to change in the future, you are also responsible for providing your best guess of what that might be and allow for reasonable changes as well.
Re: HV Clearance/OH Lines
Jim,
Thanks for the 411, the 18.5' dimension was what I was looking for. This project is near an air base and there is a maximum elevation for the landfill as dictated by the air base. I needed the distance to ground to reverse engineer the min pole height to remain under the dictated ceiling height.
I really appreciate your efforts.
Jim
Jim,
Thanks for the 411, the 18.5' dimension was what I was looking for. This project is near an air base and there is a maximum elevation for the landfill as dictated by the air base. I needed the distance to ground to reverse engineer the min pole height to remain under the dictated ceiling height.
I really appreciate your efforts.
Jim
- Status