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Inconsistent insulation on overhead power-line structures

Inconsistent insulation on overhead power-line structures

Inconsistent insulation on overhead power-line structures

Hello Everyone......... We are designing the 35kV power-line in the area of high bird activity and one of the suggestions presented from the stakeholders was to use bigger line-ground clearances on the structure which are mostly bird targets (like corner structures or structures with crossarms). One way to achieve this is by using higher voltage class insulators like 69kV, which would provide additional 300mm or so clearance.

My question is ......... would there be any concerns with using different line to ground clearances on different structures of same voltage level?

RE: Inconsistent insulation on overhead power-line structures

Other than fault recurrence reduction, no.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Inconsistent insulation on overhead power-line structures

You should consider bird proofing all of the power line. It is unlikely that just the end structures are targets.

There is useful reference material available on the subject. I have attached Avian Power Line Interaction Committee (APLIC). 2006. Suggested Practices for Avian Protection on Power Lines: The State of the Art in 2006. Edison Electric Institute, APLIC, and the California Energy Commission. Washington, D.C and Sacramento, CA. (source of the above pictures)

RE: Inconsistent insulation on overhead power-line structures

I'm thinking if tree wire or covered wire could help in this application. Spacer cable has been designed and used up to 69kv.

RE: Inconsistent insulation on overhead power-line structures

No problem using different clearances. Sometimes utilities have long term plans upgrade the voltage on a section of line, and start by using higher rated equipment during routine maintenance. In my region it is common to see 69 kV lines where older poles have 69 kV insulators and all the newer poles have 115 kV insulators. It is also common to use higher BIL (i.e. longer) insulators on portions of lines in areas subject to insulator contamination from pollution or salt spray.

Changing the phase spacing will make a small difference in the inductance of a transmission line. If you are upgrading just a few poles, the overall impedance difference may be negligible. If you end up upgrading the whole line with larger phase-to-phase clearances, it may be worthwhile to update the impedance calculations.

RE: Inconsistent insulation on overhead power-line structures

Try larger insulators for derating above sea level. Or areas of high levels of MGCL use.

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