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Discuss Didcot power station 33KV incident 18/08/19 in the Industrial Electrician Talk area at ElectriciansForums.net

UKMeterman

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Didcot power station cooling towers were demolished today,
in the process there was damage to a 33KV substation. The strange thing is that there was signifcant flashover on the 33KV network causing alleged damage and injury to the public. Some videos here



What do people think was the sequence of events?
 

rapparee

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I think it was a rough bit of work.

The Risk Assessment should have checked out cables in the vicinity of the falling towers.


In one video you can see the towers hitting the cables, they were saying about and touching each other.
 

Matthewd29

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I think it was a rough bit of work.

The Risk Assessment should have checked out cables in the vicinity of the falling towers.


In one video you can see the towers hitting the cables, they were saying about and touching each other.
sounds like drunk students on a saturday night also
 

TonyMitchell

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I read elsewhere on Twitter that a number of drones were filming the demolition and one was seen to strike overhead cables
 

UKMeterman

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No,
A metal mat was blown off the coolingtower and landed in the 33KV substation compound. I do wonder if it caused a an over voltage on the 33KV network, I wonder if there was a 132KV 33KV power cross
 

Megawatt

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USA Advisor
Didcot power station cooling towers were demolished today,
in the process there was damage to a 33KV substation. The strange thing is that there was signifcant flashover on the 33KV network causing alleged damage and injury to the public. Some videos here



What do people think was the sequence of events?
Do y’all think that dust from the cooling towers was conductive with carbon possibly shorted out the 33k power lines
 

Edtwozeronine

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The 3rd twitter link seems to show it best but it also looks like after effects was used to make that blue alien-looking flash over.
 

marconi

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The swaying HV lines in one clip is caused by the electromagnetic forces between them due to the fault currents flowing in them - see Ampere's Law and Lorentz forces. Perhaps the amplitude of these sways was such the lines touched causing the shower of sparks over any nearby onlookers.

1566192130204.png
 

marconi

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So, for a pair of parallel conductors, if the fault current was 10kA = I1 = I2 = then force per metre of line when the lines are a metre apart is:

1.25 x 10exp-6 x 10 x 1000 x 10 x 1000/(2pi x 1) =

approximately

1.25/6 x 10exp-6 x 10exp8 = 0.2 x 10exp2 = 0.20 x 100 = 20N/m

mu is the permeability of free space or magnetic constant and is - 1.25663706 × 10-6 m kg s-2 A-2

So for a 50m span total force is 50 x 20 = 1000Newtons.

As the force pulls the conductors together it increases - F is inversely related to r - so towards mid span where the conductors are freer to sway more, the forces will be much higher. On top of this, the impulse nature of this force will set up transverse vibrations of the conductors.
 
Last edited:

Lucien Nunes

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1000Newtons.
Or 225 lbs force for the physics luddites on here and those who refuse to use metric at any cost. Either way it's a fair old pull. The operating voltage is immaterial here, the same force per unit length would be experienced by a pair of meter tails for example.
 

Pete999

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The swaying HV lines in one clip is caused by the electromagnetic forces between them due to the fault currents flowing in them - see Ampere's Law and Lorentz forces. Perhaps the amplitude of these sways was such the lines touched causing the shower of sparks over any nearby onlookers.

View attachment 51446
So, for a pair of parallel conductors, if the fault current was 10kA = I1 = I2 = then force per metre of line when the lines are a metre apart is:

1.25 x 10exp-6 x 10 x 1000 x 10 x 1000/(2pi x 1) =

approximately

1.25/6 x 10exp-6 x 10exp8 = 0.2 x 10exp2 = 0.20 x 100 = 20N/m

mu is the permeability of free space or magnetic constant and is - 1.25663706 × 10-6 m kg s-2 A-2

So for a 50m span total force is 50 x 20 = 1000Newtons.

As the force pulls the conductors together it increases - F is inversely related to r - so towards mid span where the conductors are freer to sway more, the forces will be much higher. On top of this, the impulse nature of this force will set up transverse vibrations of the conductors.
Is it me or am I looking at the wrong picture but those three cables./wires, that are swaying, look suspiciously like stay wires, judging by the protective sleeves on the last few meters, mind you I do wear Specs so I could be hopelessly up the wrong tree without a branch, what do you think,? good explanation by the way nice post.
 

marconi

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I looked at Rachel Barbaresi's clip in #1 - with a bit of close observation one can see the conductors stationary and then vibrating. Click on enlarge bottom right before play.
 
Whatever the cause it doesn't look good for the Didcot project.
The previous incident caused the death of 4 workers.

HSE will need a permanent office there if this continues.
 

Pete999

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I looked at Rachel Barbaresi's clip in #1 - with a bit of close observation one can see the conductors stationary and then vibrating. Click on enlarge bottom right before play.
Will do 5 blinking words
 

Pete999

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I looked at Rachel Barbaresi's clip in #1 - with a bit of close observation one can see the conductors stationary and then vibrating. Click on enlarge bottom right before play.
Done that Marconi, honestly can't see a difference must be me cus I dont discount your theory all I see is 3 wires shaking, we must be looking at different pictures. Could you link the frame cus I'm avin an epi trying to understand, sorry Mate.
 

Pete999

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Marconi, you aren't often wrong, in fact I have always respected your views I am obviously missing something here, would love to clarify but all I can see is three wires shaking and they appear to me as though they are going straight to ground ie Stay cables.
 

Lucien Nunes

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In the second clip, there are some 33kV lines that are stationary at first immediately after the demolition. Then you see a small flashover at one insulator stack, then once the sub flashover happens in the distance and you hear the arcing, the nearby lines (which are not arcing) start twanging up and down like rubber bands.
 

UKMeterman

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  • Thread Starter Thread Starter
  • #19
I have seen in some twitter comments that initaly SSE and their control room stated it had nothing to do with the demolition. I do wonder if somene tried a remote reclose. It is rather poor that their control room didn't know when the demolishion was going to take place and lock out any auto reclose.
 

marconi

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Pete999 - take a decko at :


at about 6.15 mins in (but the preceding is interesting too). These are tests on HV/EHV installations and lines which have been done to help produce mathematical models of short circuit situations and their effects. I think I underestimated the short circuit current.

Like most engineering, there is more to consider than first meets the eye.
 
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