Problem related to lightning stirke in 132 kV double circuit

[simatic7]

Hi
I was asked what I will do if there are a number of lightning strikes in a double circuit transmission line of 132 kV. How can this problem can be dealt with ?
Could any body suggest the solution to this problem ?

 

[davidbeach]

What problem? There could be any of a number of issues related to lightning strikes. Some will be "problems" for some installations and not for others. How about buried insulated cable?

 

[simatic7]

they asked me if there is a frequent lightning strike in a DOUBLE CIRCUIT 132 kV line , what will you do ? They asked why did it happen (meaning what may be the problem) and what is the solution.

I said if we can modify the tower then we should increase the shielding angle by changing slightly the tower configuration assuming other things are fine. I wanted to know what may be the possible problems and what can be the possible solution.

 

[davidbeach]

There is no one right answer, it all just depends on many circumstances. What happens when lightning hits the line/shield? How often does it happen? What happens to system stability if the lines in question trip and reclose? Just because you have a shield doesn't mean that the line won't trip when the shield is struck as the potential across the insulator may become higher than the insulation rating. What we might do in the land of unshielded 500kV is probably different than what might be done in locations where distribution circuits are built with the neutral on top as a shield wire.

You have to study your particular installation and make your own determinations. Those answers would be appropriate for that location, but might not even apply elsewhere on your system.

For me and my system, lightning is so rare that it doesn't make sense to worry about it. In Florida lightning caused misoperations are so common that they'll reclose once on bus diff trips. Again, no one right answer.

 

[simatic7]

yes in our country also we don't take care so much about lightning but here in Australia , I assumed they are more concerned with lightning than anything else.
In the question , I was asked more about lightning only which I was least bothered . But it was a kind of time when I had to answer . I am not sure whether my answer convinced him or not ?
But still I wanted to know what are the possible casues and solution to this problem even though we need to study for specific reason. Please be kind to elaborate the problem
regards

 

[transmissiontowers]

I am a structural guy so take this with a grain of salt. You need to find out what the footing resistance is for the structures legs (1 for a pole and 4 for a tower). When lightning hits the shield/earth/ground wire, if the footing resistance is higher than 4 ohms, the lightning will flash over to the transmission conductors since the BIL of the insulators cannot handle the massive voltage and current of the lightning strike. If you have good grounds with a low footing resistance, the lightning will go to ground at the 2 closest structures.

You can also put in some distribution under-build on the transmission towers. Since the distribution insulators are much shorter than the 132 kV insulators, the lightning will flash over to the distribution line and save the transmission line. This will make your distribution customers very mad as their transformers will explode and put them in the dark and possible damage their electronics.

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

 

[simatic7]

I also read that if we put lightning arrester in one circuit (near the tower) of the line , the tripping rate in other ckt will also be reduced. so the possible solutions in total seemed to be
1. reduce the tower resistance and
2. we can put lightning arrester in one of the circuit.

 

[transmissiontowers]

FWIR, lightning arresters are not generally used when you have a ground wire above the circuit. They are used when you do not have a ground wire.

Of course the arrester vendor will tell you that they will protect the line and happily sell you lots of arresters.

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