plscadd

[ohmme]

hi gentlemen,
How can I work a model for the type of insulator v-string (2-part) ??
by method1
plz, see attachment

 

[transmissiontowers]

The insulators in your picture are not 2-part, they are suspension insulators. They are indeed very odd but they are definitely suspension insulators. I would put in an insulator length that is the distance from the arm tip to the wire directly below the arm tip. The weight would be the weight of the 2 insulators and the wind area is the area of 2 insulators. The concept of insulators in PLS-CADD is a load transfer mechanism to get the wire loads into the lattice structure. The ground clearance will be correct which is what you are after. The only part that might be mathematically a little off would be the longitudinal restraint the 2 insulators provide vs a single suspension insulator. My assumption is the difference will be so small that it is "close enough" to reality.

We calculate stress in angles to the 4th decimal but we really only know the tower wind and tension loads to about the closest 50 pounds if that close.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[ohmme]

thank u very much for reply
I think there is a Z dimension (x,y,z) for attachment point ??
..

 

[transmissiontowers]

I usually do full structural models when I do my models but I am a little familiar with the Type 1 structures you are trying to do. Yes, you establish the height of your structure in the top box then all wires are referenced from the top of the tower. The Transverse direction is perpendicular to the wires (probably X in your screen shot). The vertical coordinates are referenced to the top of the tower and positive is down from the top. Your Z direction is the Longitudinal and in your case should be zero.

The Type 1 structures only serve to hold the wire up to do vertical clearances for the sag and you cannot judge the strength of the tower. You might be able to generate a report for the structure to determine the loads at the wire attachments to give to a designer.

Good luck, and come back if you hit a snag.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[ohmme]

thank u Mr. transmissiontowers
yes,I cannot judge the strength of the tower by method1...its for cost estimate
thank u very much

 

[1ineman]

Hi guy
This type of insulator still is being used this date.We call it inverse V ssuspension string. It is used when vertical departure angle is exceed certain number which could damage the cable. Yes, sometime it can be fix by big departure angle trunk on clamp, however some utility still use. For PLSCADD model, u just simply model it as a regular suspension string as gentlemen above mentioned.
Cheers.

 

[ohmme]

thank u 1ineman