HV transmission lines during rain

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vinod

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Hi friends,
since water is a very conductive substance, Why the HV lines are not get shorted during rain? As we know during Rain, conductors and tower structures became wet. Is this water will make continuity between live lines and tower structure?

Kindly explain to me? :?
 
vinod said:
Hi friends,
since water is a very conductive substance, Why the HV lines are not get shorted during rain? As we know during Rain, conductors and tower structures became wet. Is this water will make continuity between live lines and tower structure?

Kindly explain to me? :?
Click to expand...

Generally most insulators are shaped like a bell which prevents the water from wetting the underside of the insulator, there are other designs that also work like this, also most rain water is not very conductive unlike water that may flow through or upon the Earth where it can pick up minerals that can make it more conductive, around salt water where you might have a high degree of salt contamination you can see a higher failure rate of insulators but with new designs in insulators this is not as much of a problem as it was in the past.

Also in many cases when a small leakage starts out it causes the insulator to heat up which helps dry out the insulator.
 
hurk27 said:
Generally most insulators are shaped like a bell which prevents the water from wetting the underside of the insulator, there are other designs that also work like this, also most rain water is not very conductive unlike water that may flow through or upon the Earth where it can pick up minerals that can make it more conductive, around salt water where you might have a high degree of salt contamination you can see a higher failure rate of insulators but with new designs in insulators this is not as much of a problem as it was in the past.

Also in many cases when a small leakage starts out it causes the insulator to heat up which helps dry out the insulator.
Click to expand...

Thank you very much Sir,

Well explained.... I am very clear about it.....
 
vinod said:
Hi friends,
since water is a very conductive substance, Why the HV lines are not get shorted during rain? As we know during Rain, conductors and tower structures became wet. Is this water will make continuity between live lines and tower structure?

Kindly explain to me? :?
Click to expand...
Added to what Hurk said, water isn't actually all that conductive anyway.
This from an article I have on my PC (sorry, no link)
Just like metal, water can conduct (transport) electricity. This is because there are salts dissolved in the water. If you have pure water with absolutely no salts, electricity will not be conducted and conductivity will be 0.
Click to expand...

We quite often use water for direct cooling of live semiconductor heat sinks.

Onelimb_zps5304a687.jpg
 
Though not recommended if you were to spray a mist of water at those conductors you would be at less risk then if you were to spray a solid stream of water at them. Air between the droplets has insulating properties.
 
Insulator are bell shaped to prevent a continuous stream of water from forming. They breaker up the water and run off of it. If rain didn't exist in theory the insulators could be smaller and at lower voltages could get away with having ridges/bells.
 
The bells or ridges also serve the very important function of packing a longer surface creep distance into a shorter linear distance.
That affects dusty as well as wet conditions.

Tapatalk!
 
Besoeker said:
Added to what Hurk said, water isn't actually all that conductive anyway.
This from an article I have on my PC (sorry, no link)


We quite often use water for direct cooling of live semiconductor heat sinks.
Click to expand...

well, DWP uses a washdown truck to remove the dirt and dust from
glass insulators on live lines. it's completely demineralized, and they
shoot it from a water cannon. basically a fire truck with a very pure
tank of water.

it's interesting to watch them wash down 230 KV glass at night.... there
is quite a bit of corona.

but no flashover or leakdown.

unlike the fellow in LA a number of years ago, who climbed up a 230 KV
tower to above the energized conductors, armed with a knapsack of beer,
to get good and drunk, and watch the sun set.

beer being what it is, after a while, he needed to go, and decided it seems,
to check his accuracy by seeing if he could hit the wire underneath him.

urine is conductive.

the fall didn't kill him. he lived for three days.

i know that sounds like urban BS, but i heard it at a LADWP safety meeting.
 
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I was working at a new NG turbine power plant and one day it was rainy and foggy. The conductors for the 315kV lines were arcing past the insulators and the arc was going to the steel on the towers.

We were told that was a normal condition for that type of weather.
 
K8MHZ said:
I was working at a new NG turbine power plant and one day it was rainy and foggy. The conductors for the 315kV lines were arcing past the insulators and the arc was going to the steel on the towers.

We were told that was a normal condition for that type of weather.
Click to expand...

Sure doesn't happen like that around here with the 500kV lines. Must raze havoc with AM radio.
 
Back in my days at University (199........something). There was a CRT based TV set in the foyer of the electrical engineering building. This TV was inside a (sealed) tank which was full of water. The TV was powered up & working fine, displaying a perfect picture of all students entering the building.

It was working fine because the tank had been filled (and then sealed) with pure water. Pure water (which contains no salts, minerals or other impurities) is actually a very good insulator, much better than air infact.

As an aside, from my school days, we were given some pure water to taste .... and its horrible. The salts & minerals give water its 'taste'.

Adrian
 
That water would, however, change the capacitance of any open plate capacitors inside the TV, as well as the stray capacitance values of the wiring. Water is polar molecule....
For an older TV they might have had to tweak some component values.

Tapatalk!
 
Technically, he just said it was horrible, not that it had a horrible taste.
When you expect something its absence can be disturbing.
It might also have had all kinds of non-ionic contaminants.

Tapatalk!
 
vinod said:
Hi friends,
since water is a very conductive substance, Why the HV lines are not get shorted during rain? As we know during Rain, conductors and tower structures became wet. Is this water will make continuity between live lines and tower structure?

Kindly explain to me? :?
Click to expand...

The reason why rain does not short circuit HV transmission lines is the same as why water spray extinuisghing fire on some outdoor HV transformers does not cause a short circuit or cause shock to the users of the same water distribution system: it is the discontinuity among water droplets.
 
Sahib said:
The reason why rain does not short circuit HV transmission lines is the same as why water spray extinuisghing fire on some outdoor HV transformers does not cause a short circuit or cause shock to the users of the same water distribution system: it is the discontinuity among water droplets.
Click to expand...
I don't suppose the droplets would be the concern but the accumulation of them.
But see post #3 and the contribution by Adrian.
 
The OP is talking about the effect of rain on HV transmission lines and not about the effect of accumulated rain water on HV transmission lines. If the rain were of continuous sheet of water, no HV overhead lines are possible,because the rain water absorbes minerals from the atmosphere and more or less conductive.
 
Sahib said:
The OP is talking about the effect of rain on HV transmission lines and not about the effect of accumulated rain water on HV transmission lines. If the rain were of continuous sheet of water, no HV overhead lines are possible,because the rain water absorbes minerals from the atmosphere and more or less conductive.
Click to expand...

From the OP:

Is this water will make continuity between live lines and tower structure?
Click to expand...
 
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