How to measure the height of an overhead power line?

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mdooher

Hmm, what to write...
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#2939774 8-Jul-2022 14:07

shk292:

mdooher:

I may have even done it with a wind up type tape measure by just throwing it over the lines... (don't do that, it's stupid)

I was going to suggest throwing a weight attached to a length of nylon cord over the line and measuring, but despite not being able to see how this would be dangerous, it still doesn't seem a good idea.

I would have thought that, unless it's right on the edge of being allowable, the trig methods are accurate enough.

the reason it is dangerous (apart from wet string etc) is the lines will not be in a good state of repair and you could knock off bits of cable sheath or miss and get it to wrap around a conductor getting stuck (then what happens to your string when it rains?) ...

Matthew

shk292

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#2939775 8-Jul-2022 14:13

mdooher:

the reason it is dangerous (apart from wet string etc) is the lines will not be in a good state of repair and you could knock off bits of cable sheath or miss and get it to wrap around a conductor getting stuck (then what happens to your string when it rains?) ...

I'd thought of dry string but not the other things - I knew there was a reason it didn't seem sensible

Could throw a pair of laced-together trainers up there for an easier laser target. I've seen that done all over NZ

gregmcc

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#2939807 8-Jul-2022 16:02

Danite: Could buy a couple of pieces of 20/25mm conduit and push them together, would wobble but be safe.

***ABOVE IS NOT SAFE*** DO NOT TRY

gregmcc

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#2939810 8-Jul-2022 16:15

I can't believe all the posts of people suggesting throwing things over the LIVE lines, come on people common sense says don't throw or poke anything at power lines.

Take my advise (from an Electrical Inspector), if you want to do a physical measurement then get a qualified person with the right tools involved. The mathematical solution may work - but as this isn't my area knowledge I'm not competent to make that call, the laser measurement should work if you can get the aim right.

tim0001

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#2939836 8-Jul-2022 17:11

Thanks everyone for their input. Below are some answers to the questions.

The overhead cables are part of the LV network, and only just cross our property by about 10 cm. (We've got an underground feed). The overhead lines are bare (ie no insulation). Cable swing will be minimal because the pole is only 9m from the shed. The neutral cable is closest to the shed.

Below is my CAD drawing.

The shed is significantly further away than the distances specified in "table 3". So IMO there is limited benefit in measuring to the nearest cm.

Daynger

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#2939854 8-Jul-2022 18:53

Just stand below it and extend out a tape measure until you can hook it onto the line then measure.

Note: Do not actually do this, it could kill you.

insane

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#2939876 8-Jul-2022 20:32

Here are some guidelines I found online

https://www.powerco.co.nz/safety/electricity-safety/building-near-lines

Sounds like you're close enough to want to get this Okay'd by the power provider first.

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shk292

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#2939928 9-Jul-2022 08:40

insane: Here are some guidelines I found online

https://www.powerco.co.nz/safety/electricity-safety/building-near-lines

Sounds like you're close enough to want to get this Okay'd by the power provider first.

I disagree based on the diagram posted by OP. He has 5m vertical and 2m horizontal, and needs 4m. That's well outside the margin of error

neb

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#2940160 9-Jul-2022 17:40

mdooher:
the reason it is dangerous (apart from wet string etc) is the lines will not be in a good state of repair and you could knock off bits of cable sheath or miss and get it to wrap around a conductor getting stuck (then what happens to your string when it rains?) ...

The OP mentioned they were less than a year old so should be OK in that regard, but even then it's not something I'd want to do.

neb

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#2940161 9-Jul-2022 17:41

Daynger: Just stand below it and extend out a tape measure until you

feel the jolt in your arm,

then measure.

gregmcc

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#2940162 9-Jul-2022 17:48

@freitasm, can we get this topic locked as there is a lot of downright dangerous suggestions been made, suck as throwing string or tape measures over live power lines, measuring with plastic conduit (just because it's plastic doesn't mean it protects you from and electric shock) and there are others who are offering electrical advice who I doubt have any kind of electrical background.

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