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Anonymous Poster #1

Cross Arm vs Boom in Transmission Tower

07/09/2018 12:45 PM

Dear Sirs,

It is said that cross arm supports power conductor through string insulators and boom also supports power conductor in horizontal configuration only.

But what is the difference between cross arm and boom?

Best Regards,

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#1

Re: Cross Arm vs Boom in transmission tower.

07/09/2018 12:56 PM

Er, the direction of the thrust it is there to withstand?

Why not ask the people that <...It is said...> by?

Is this a trick question or is there a prize for getting it right?

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#2
In reply to #1

Re: Cross Arm vs Boom in transmission tower.

07/09/2018 2:27 PM

Homework or interview question.

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#3

Re: Cross Arm vs Boom in Transmission Tower

07/09/2018 2:49 PM
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#6
In reply to #3

Re: Cross Arm vs Boom in Transmission Tower

07/09/2018 9:40 PM

Left: Vertical configuration using cross arms.

Right: Horizontal configuration using boom.

Both are used to support conductors.

https://www.slideshare.net/KumarVEL7/transmisiion-line

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#4

Re: Cross Arm vs Boom in Transmission Tower

07/09/2018 3:08 PM

No difference, basically two names for the same thing...

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#5
In reply to #4

Re: Cross Arm vs Boom in Transmission Tower

07/09/2018 9:02 PM

Well, sort of the same I suppose if considering electrical functionality. A Cross Arm is the term for the part(s) that hold the conductors. A Boom is part of the structural support of the tower itself and may also be USED the same as a Cross Arm to hold conductors since it is going to be oriented the same way. But a Cross Arm is just there to hold the conductors, no structural support involved.

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#7
In reply to #5

Re: Cross Arm vs Boom in Transmission Tower

07/09/2018 9:43 PM

What's the difference between a beam and a boom?

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#9
In reply to #7

Re: Cross Arm vs Boom in Transmission Tower

07/09/2018 10:46 PM

What's the difference between a beam and a boom?

A beam is a light. A boom is a sound...

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#11
In reply to #9

Re: Cross Arm vs Boom in Transmission Tower

07/10/2018 10:37 AM

What about a boombeam?

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#12
In reply to #9

Re: Cross Arm vs Boom in Transmission Tower

07/10/2018 11:30 AM

More like two vowels and a perception.

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#14
In reply to #12

Re: Cross Arm vs Boom in Transmission Tower

07/10/2018 1:06 PM

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#15
In reply to #14

Re: Cross Arm vs Boom in Transmission Tower

07/10/2018 1:22 PM

Beam me up Scottie?

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#8

Re: Cross Arm vs Boom in Transmission Tower

07/09/2018 10:02 PM

A beam is a ray of light, a boom is a loud sound.

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#13
In reply to #8

Re: Cross Arm vs Boom in Transmission Tower

07/10/2018 12:10 PM

Does (Humbug State) still offer a program in your engineering discipline?...

(They discontinued mine, so I stopped financially supporting them...)

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#10

Re: Cross Arm vs Boom in Transmission Tower

07/10/2018 6:11 AM

The difference depends on the object described and practice in a particular application! It is not surprising you are confused.

In this case, Arm projects out like a person's arms, but a boom does not, with boom side clearance of conductor is got by waist of tower narrow compared to top.

wiktionary.org on internet gives following relevant definitions - use of words is specific to transmission towers I guess & probably follows those used in standards for such, the long horizontal part of a crane gets called arm or boom!!.

Arm - A long, narrow, more or less rigid part of an object extending from the main part or centre of the object, such as the arm of an armchair, a crane, a pair of spectacles or a pair of compasses.

The robot arm reached out and placed the part on the assembly line

"Boom" is probably related to "beam" in this application -typically a horizontal part of a building structure thin compared to length & supported at both ends (called "cantilevered beam" if only supported at one end).

boom

  1. A movable pole used to support a microphone or camera.
  2. A horizontal member of a crane or derrick, used for lifting.
  3. (nautical) A spar extending the foot of a sail; a spar rigged outboard from a ship's side to which boats are secured in harbour.
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#16
In reply to #10

Re: Cross Arm vs Boom in Transmission Tower

07/10/2018 2:23 PM

A cantilevered beam is a boom...

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#17

Re: Cross Arm vs Boom in Transmission Tower

07/11/2018 12:20 PM

If the word "tower" is added to OP's question, the differences become much more obvious.

A cross arm tower can carry two circuits or more, most boom towers cannot (there are exceptions).

A cross arm tower is taller, narrower, has a smaller footprint, occupies less right of way, and provides more visual pollution than a boom tower, for a given voltage level.

There are geological/geographic/siting considerations such as soil conditions, terrain, vegetation, local jurisdictional requirements, etc.

Cross arm towers generally carry lower voltage circuits while boom towers become a necessity at EHV (345kV and above) due to conductor spacing, height, and ground clearance restrictions.

There are electrical considerations such as circuit impedance, power carrying capacity, isokeuranic (lightning severity/frequency) levels, soil resistivity, etc. may favor one design over the other.

Plus material and construction costs, foundations, maintenance, vegetation control, etc., etc., need to be factored in as well.

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