HLEP WITH PLS CADD STRUCTURE ANALYSIS OF A LINE BUILT IN 1970

[bgannon]

I am performing analysis for a client(small local owned utility) on a 115kV line they built in 1970. they want to swap their existing ADSS or SW for OPGW or higher fiber ADSS. My task is to evaluate whether or not the structures can withstand the (small) increase in loading. I have modeled the structures using LiDAR, batch thermal calculator for finite element tensions, and old P&P's. Many of the DE structures which have head and back guys to support single sided conductor are failing. The PLS CADD model shows that the pole itself (all class 1 DF) are buckling.

What were the NESC strength requirements for 1970? I believe that the strength factors applied today are going to be much lower than they were in 1970, hence the calculated failure by today's standards(not even taking into account age and line decay).

Has anyone worked with this before?

 

[DRWeig]

Hi bgannon,

You might get more info in the Electric Power & Trasmission & Distribution forum. Here's a link.

http://eng-tips.com/threadminder.cfm?pid=238

If you do re-post there, please remember to come back to this thread and red-flag it.



Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[bacon4life]

The overload factors assumed in the 1970s NESC are not easily compatible with the nonlinear analysis provided by PLS-CADD due to pole p-delta effects. In older codes the pole deflection was ignored. PLS-CADD actually models horizontal pole top displacement, then calculates the increase stresses from the vertical loads not being directly above the pole base. These p-delta stress are quite nonlinear, so a 4x Wind overload factor might result in more than a 16x increase in stress.

Take a look at

http://www.powline.com/products/buckle.pdf

for guidance on on how to use strength reduction factors instead of overload factors to when attempting to model buckling.