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Overhead line transmission tower angle problem
2

Overhead line transmission tower angle problem

Overhead line transmission tower angle problem

(OP)
hi everybody,I'm new to this forum.
I am an electrical engineer with a transmission and distribution company. we are currently constructing a 33 kV OHL. Our problem is with the angles on the towers.
By the manufacturers specifications,angles up to 10degrees should be considered as light angles and therefore clamps to hold conductor should be a suspension type.but following this instruction ended up with the suspension clamps and insulators bending so close to the metal structure(tower) even at angles near 6degrees,which means the conductor is now very close to the tower too. My question is,Is it advisable to use that light angle(LA) tower as an anti cascading (AC) tower,that is to use tension insulators on both sides,so as to avoid the bending of the insulator to the pole ? are there any other options available? thank you.

RE: Overhead line transmission tower angle problem

Usually towers are designed to take insulator swing into account. Do you have a drawing of the type of tower you have?

One of the advantages of suspension insulators is that they swing to equalize tensions between spans. Using tensions insulators will require the tower to withstand additional longitudinal stress. You would have to check if your light angle tower can withstand the extra stresses.

An anti cascading tower has additional longitudinal strength, not just a different insulator configuration. With suspension insulators in a broken conductor case, they can swing to near horizontal to lower the tension, but a tension insulator is already horizontal so the tower must withstand full tension.

Options we have used at 115 kV include:
-Extra bells/longer insulators
-Brackets or adapters to hold the insulator further from the tower.
-Weights suspended from the insulator to hold them closer to vertical.

RE: Overhead line transmission tower angle problem

(OP)
thank you bacon4life,really appreciate it. looking through your solutions,we have tried the last option and we hope it KEEPS the insulator closer to vertical.
I however i need further clarifications on the first option -Extra bells/longer insulators- wont this further increase the swing? i will try and get a scanned copy of the towers soon. thank you.

RE: Overhead line transmission tower angle problem

The attached file has a picture of single wood pole vertical construction where we use a bracket, but in some cases the same could be accomplished by using longer than standard insulators.

Can your insulator string be shortened any without compromising any other clearances? For example our standard polymer insulator has ball fitting so it would be identical to porcelain bells, but it would be a few inches shorted if it was purchased with a clevis and the ball-clevis adapter eliminated.

RE: Overhead line transmission tower angle problem

I think that Albert is referring to something like a double circuit tower and the outside circuit being pulled back toward the tower. If single circuit, then the pole (tower not really necessary at 33kV) should be to the outside of the conductor turn.

RE: Overhead line transmission tower angle problem

You need longer arms on the outside of the bend and shorter on the inside.

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