Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Atomfritz]

Joe, thank you for the illustrative explanation of "routing affairs".

...they had all power to Fukushima 1 going through that tower. Thus, they created a single point of failure. If they were trying to design in double and triple redundancy, they failed miserably.

As I explained above, according the schematic each reactor had it single grid line.
Reactors 1+2 had no redundant supply transformers, so have to shutdown when line fails.
Reactors 3+4 share two redundant supply transformers, one was unavailable due to maintenance.
There is no power input/output switching capability to make use of any other than their fixed assigned line.

The Japanese do not have exclusive ownership of intelligent people doing stupid things. That can happen anywhere, but in the case of Nuclear Power Plants where meltdowns can result in millions dying of cancer, this electrical circuitry screwup -- EVERYTHING ROUTED THROUGH ONE TOWER. -- should have been caught and corrected years ago.)

Indeed.
In the given scenario, line Okuma-1, the only line that still delivered electricity to the plant could not be used because it was connected to reactor 1, whose circuit breaker was damaged.
Sadly there had been no possibility to switch line Okuma-1 onto reactor 4 (Okuma-4).

In Germany usually 2 to 3 different lines (not fake redundancies like 2-line-masts etc) are connected to a NPP, so that shutdowns due to line failure are very rare. Usually it's just a matter of re-routing at line failures and maintenance, preventing outages and worse things.

Electricity that is generated for transmission on high power lines has stepup transformers in the system. Not only that, but the actual wires are designed for high voltage. Trying to use those lines to build an emergency power supply back to Fukushima would be totally impractical.

They just repaired the switchyard damage to get back to grid power, as was done quite early and shown in photos.

 

[joewein]

Also I was wondering whether it would not be possible to use the high voltage power lines backwards to supply power back to the plant in case of emergency if they are still safe while all other lines have collapsed.

That's the status that Fukushima-II (which kept its grid connection) is in right now.

 

[jim hardy]

""Look at the schematic here mentioned by joewein.
Just imagine a switch so you can conduct the Okuma-1 supply (cut off after switch at circuit breaker O-1) to circuit breaker O-84.""

that lateral tie appears to exist at the "M/C" (motor control center?) level, observe the horizontal lines connecting the three 'normal M/C' 's.

I see five lines coming into plant which seems enough.
but it's a moot point because all the M/C's are shown "Out of order because of inflowed or inundated.." except a lone one on unit 6.Loss of the complete electric grid is considered a single failure so should cause no trouble.
But there should be no single failure that'll take out both of a plant's diesels (or their respective switchgears) at once.
We're back to electrical switchgear in a basement that got filled with seawater.

Some poor soul is really kicking himself right now for not acting on those mid-nineties warnings about tidal waves. And somebody else is proud of #6.

 

[elektrownik]

They should use cable underground lines... Air lines are not quake-resistant...

 

[maddog1964]

They should use cable underground lines... Air lines are not quake-resistant...

Overhead lines vs underground lines would be not be a simple decision... there are many engineering factors that would have to be addressed... remember the pictures of how much the land (shown mostly) on the road pictures shifted. Then you also have to engineer the water intrusion issues (this would be all the time, not just when a EQ or storm happens, as you have water table). Last but definately not least when you have a disruption, not if, it is very combersom and time consuming to repair as fast. You can see a down wire or tower.

It would come down to a risk assesment issue and there would probably be places that underground might be better.. and some that overhead would be better...

but I don't believe we have the information necessay to make a logic choice.. remember the dicharge to the sea has been through the "mechanical tunnels (in part)...

Possibly a good ideal in some locations, but not in others

 

[zapperzero]

Meanwhile, three more workers got doses in excess of 250 mSv.

http://www.bloomberg.com/news/2011-07-07/tepco-says-3-more-workers-exposed-to-radiation-exceeding-limit.html

Must be the guys who went exploring in reactor three.

 

[tsutsuji]

What do you mean exactly ?

On http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e20.pdf we can see the 500 kv Futaba line located next to the collapsed Yonomori line. I don't know the status of the Futaba line, but if it was safe, Tepco could have found convenient to use that Futaba line to bring power.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf shows that Tepco used Futaba line tower No.2 as a replacement of the collapsed Yonomori tower No. 27 (1). My idea is to use the whole Futaba line : all its towers and all its conductors, with switching equipment on both ends enabling to connect quickly in case of emergency.

(1) Tepco also released this picture : http://www.tepco.co.jp/en/news/110311/images/110323_denngen_4.jpeg showing workers working on Futaba tower No. 2, and this one http://www.tepco.co.jp/en/news/110311/images/110323_denngen_3.jpeg showing the work on Yonomori tower No. 28.

 

[Susudake]

They should use cable underground lines... Air lines are not quake-resistant...

My understanding of this as a non-technical expert is that the above-ground power lines in Japan is because of the earthquake situation--both diagnosis and repair are greatly expedited. Ugly but practical.

More knowledgeable folks--is that not the case?

 

[NUCENG]

My understanding of this as a non-technical expert is that the above-ground power lines in Japan is because of the earthquake situation--both diagnosis and repair are greatly expedited. Ugly but practical.

More knowledgeable folks--is that not the case?

You are correct. If an underground cable is faulted it must first be excavated for repair. In high earthquake areas the biggest concern is a slip or thrust fault that can shear a cable just as it does to roads.

In the case of the tower that collapsed, I think the investigation will reveal that the foundation was either eroded or disrupted by the earthquake.
I heard something about a landslide, but can't remember if that was what collapsed the tower.

 

[NUCENG]

Electricity that is generated for transmission on high power lines has stepup transformers in the system. Not only that, but the actual wires are designed for high voltage. Trying to use those lines to build an emergency power supply back to Fukushima would be totally impractical. It could not have been reengineered in time to prevent the total melt down of the three plants that are now belching radioactive gases over Japan and the Pacific Ocean.

Joe I need to clarify this. In normal power operation the license requires at least two independent feeds of offsite power to the plant switchyard. TEPCO reports have claimed six, but at least one other line was in close proximity to the failed tower, apparently running parallel in the same right-of-way. The two would really only count as one due to the potential for one failure to take them both out.

The plant generator feeds the grid through the Main transformer which raises voltage from the generator to grid voltages. An auxiliary transformer taps off power for the plant to run non-essential (non-safety) loads. The essential switchgear receives input s from the grid through another transformer. All house loads are thus already supplied with step down transformers to permit them to run from the grid. Depending on the damage to switchyard breakers and transformers, this would have been the fastest way to restore power to the plants. If anyone has seen a detailed list of failures in the switchyards, I would appreciate a link.

In an accident, the generator trips off , but the plant busses should automatically transfer to the grid. That didn't happen at Fukushima Daiichi due to failure of all offsite power at the time of the earthquake.

The best information I have seen from the NISA report to the CNS was that the switchgear to connect the diesels to the essential busses was also located in the turbine building basement and was flooded. so only one air cooled EDG was able to carry essential loads at units 5,6. That led to the extended SBO at units 1-4 and to core damage after batteries were exhausted and the IC on unit 1 was isolated.

Non-essential loads are not supplied from the diesels so they were all off. The SFP Cooling system pumps were thus lost with the offsite power. However, there is a backup mode of SFP cooling using the RHR system which is powered from the diesels. At Fukushima that was disabled along with the diesels.

There should never be a case where all the offsite power depends on a single tower. And I believe that is true with Fukushima. I will keep looking to clarify how many offsite feeds were lost and the actual causes for each one. I expect to find that the tsunami destroyed a number of switchyards both north and south of the plant. The grid diagraqm of japan i saw earlier that I will be looking for did not have many east-west links across the island, probably because of the mountains. To be continued.

The quality of backup power for SFP cooling is one of the big lessons learned, and that should require modifications at most BWRs.

 

[tsutsuji]

I heard something about a landslide, but can't remember if that was what collapsed the tower.

The landslide is mentioned in http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e20.pdf

If an underground cable is faulted it must first be excavated for repair. In high earthquake areas the biggest concern is a slip or thrust fault that can shear a cable just as it does to roads.

Perhaps the cable should not be buried, but installed in a trench or a tunnel where it is easily accessible. That tunnel, in turn, would be compliant with the relevant earthquake resistance standard, using whatever earthquake engineering technology is needed. The system should allow enough flexibility to prevent the cable from breaking if pulled. The following does not concern electric cables, but the general idea is perhaps relevant :

In a question about the reliability of the 4 km water pipes at the water treatment facility this morning, Junichi Matsumoto said : "The hoses are not attached to the ground, so (in case of earthquake or typhoon) they can absorb even if they vibrate. As long as they are not stretched by a crack in the ground, it is OK. The risk that highly contaminated water leaks over a large area is low" http://sankei.jp.msn.com/life/news/110708/trd11070813220012-n1.htm

 

[Atomfritz]

that lateral tie appears to exist at the "M/C" (motor control center?) level, observe the horizontal lines connecting the three 'normal M/C' 's.

I see five lines coming into plant which seems enough.
but it's a moot point because all the M/C's are shown "Out of order because of inflowed or inundated.." except a lone one on unit 6.

[...] We're back to electrical switchgear in a basement that got filled with seawater.

Hmm, I do not know if the station transformers also have been flooded and rendered unusable. They are outside of the parts enclosed with the red dotted line (flooded or submerged components).
But the fact that they are not being used (except at #5/#6) indicates that you are probably right.

(opinion)
BTW, I disagree somewhat with the opinion that one line is sufficient.
I really prefer the german approach of at least two redundant line transformers/lines. So in case of line problems (could be just due to lightning and such minor causes), transformer fires etc usually no shut down is necessary, just some instant re-routing.
(/opinion)

On http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e20.pdf we can see the 500 kv Futaba line located next to the collapsed Yonomori line. I don't know the status of the Futaba line, but if it was safe, Tepco could have found convenient to use that Futaba line to bring power.

As the Futaba line is not shown in the schematic, I suppose it is normally used to transport unit #5/#6 power to the grid. 66kV (Yonomori) really is a bit little for roughly 2GWe.
On the other hand, 500kV is not easy to handle in emergency situation when you have to improvise. You cannot handle this with portable equipment.
If the 500kV transformer has also been damaged, it will take some time to repair the 500kV connection.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf shows that Tepco used Futaba line tower No.2 as a replacement of the collapsed Yonomori tower No. 27 (1). My idea is to use the whole Futaba line : all its towers and all its conductors, with switching equipment on both ends enabling to connect quickly in case of emergency.

They just hung the conductors of Yonomori line to Futaba line tower in a temporary makeshift way, without altering anything on the Futaba line.
If they'd like, they could easily use the Futaba line at 66kV using a mobile transformer, but probably they feel to have sufficient redundancy now.

Edit:
They operate part of Yonomori 1 line at 6kV, using a portable transformer (see Work 3,4,9) to transform from 66 to 6.
Maybe because in March the roads were in no shape to transport a big transformer on a truck convoy?
I am still guessing why they did this. Maybe it was the fastest way to get a handy low voltage to operate with?

Thanks Tsutsuji for the links! This schematic and the pictures really help to get some insight.

 

[NUCENG]

...

Additional Information:

Applicable drawings in the NISA report to the Convention on Nuclear Safety are Figures 3.2-8a, and b. Explanation was as follows:

"The earthquake caused damage to the breakers of the switchyards of Units 1 and 2. As to TEPCO nuclear line (66 kV) from Tohoku Electric Power, although it’s not possible to estimate the cause, cables were damaged. Concerning Units 3 and 4, in addition to the Okuma No. 3 transmission line under construction, the breakers of Nos. 3 and 4 transmission lines on the side of Shin Fukushima Power Substation failed. In addition, about Units 5and 6, one transmission line tower (No. 27 tower) connecting to the switchyards of Units 5 and 6 was collapsed. So, as a result, although damage caused by tsunami was not clear, all external power supplies of Units 1 to 6 were lost." page III-33.

That explanation leaves me with more questions than answers.

The two independent offsite feeds I discussed above are apparently a 275 kV supply and a 66 kV supply. Th 66 kV supply was lost due to cable failures.

For the 275 kV supply there were the following problems and failures:

• It appears there were breaker failures in the site switchyard for units 1 and 2 that took out all offsite power to those units.
  
• Units 3 and 4 had breaker failures at the Shin Fukushima switchyard, plus there was a line that was under construction.
  
• The tower colloapse took out supplies to Units 5 and 6.

There was a common cause failure here - the earthquake, but the tower failure was only one of several failures. Cables and breakers failed in the Shin Fukushima switchyard and on site in the 66 kV swichyard and supplies to units 1 to 4.

I earlier quoted reports that TEPCO had initiated a seismic upgrade of the Fukushima plants under direction from NISA. They had not completed reanalysis and upgrades to the new SS2 limit of 600 gal for seismic events off the coast. Based on the number of failures above, I wonder whether they even looked at their offsite power supplies and the Shin Fukushima switchyard. Even more important, some of the failures in the on-site switchyard may have been in safety related cables or breakers. The description above isn't detailed enough to tell.

 

[NUCENG]

The landslide is mentioned in http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e20.pdf



Perhaps the cable should not be buried, but installed in a trench or a tunnel where it is easily accessible. That tunnel, in turn, would be compliant with the relevant earthquake resistance standard, using whatever earthquake engineering technology is needed. The system should allow enough flexibility to prevent the cable from breaking if pulled. The following does not concern electric cables, but the general idea is perhaps relevant :

In a question about the reliability of the 4 km water pipes at the water treatment facility this morning, Junichi Matsumoto said : "The hoses are not attached to the ground, so (in case of earthquake or typhoon) they can absorb even if they vibrate. As long as they are not stretched by a crack in the ground, it is OK. The risk that highly contaminated water leaks over a large area is low" http://sankei.jp.msn.com/life/news/110708/trd11070813220012-n1.htm

Thanks, I had just seen the landslide drawing that almost took out the second line as well.

I just looked up the insulation standards for a 300 kv (close to the 275 kV at Fukushima. The standard ceramic stacked insulators used on transmission towers at that voltage are about 10 feet long (about 3 m). That tunnel would have to be pretty big to prevent ground faults and moisture intrusion is a huge threat for shorts. I have never seen buried applications of high energy transmission lines, but I'm not rejecting your idea. I'm thinking it may be a lot better to really amp up backup supplies,on site or close by, that can be done at 480 or 1600 VAC which covers the onsite voltages for the big loads.

Edit: Just talked to a transmission engineer. Apparently another reason not to bury or have high voltage lines close to the ground is that it skews power factor by adding a lot of capacitance between the cables and ground. Also he reminded me that three phase power lines have to be separated from each other as well as from ground so a tunnel or trench would bave to be on the order of 9 m or larger to keep the lines separated from each other and from ground.

 

[Atomfritz]

Thanks NUCENG for hinting to the convention report!

Now I have three different pictures to compare: http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf":

Looking at the image above you hinted at, I learn that the Futaba line apparently cannot be used for supplying power to the plant, as it is marked with the text "let-off only".

And, it still remains unclear where the #5/#6 switchboard can draw its supply from. From Tohoku line only, or from the other reactor's switchyards also?

It is really confusing that one document talks of "under construction", and the other talks of "under maintenance". Looking closely at the schematics, I suppose there is has in fact been only maintenance, and not construction of a new line.

BTW, I read in the report "In addition, the normal high voltage switchboard of Unit 1, the normal high voltage switchboard of Unit 2, and the normal high voltage switchboard of Units 3 and 4 were connected mutually, and electric power interchange was possible."
So I possibly was wrong in my assumption that each reactor was fixed to one single line. The above sounds like that it was possible, for example. to have reactor 2 and line 1 in maintenance, using line 2 to let off reactor 1's electric output.

Based on the number of failures above, I wonder whether they even looked at their offsite power supplies and the Shin Fukushima switchyard. Even more important, some of the failures in the on-site switchyard may have been in safety related cables or breakers. The description above isn't detailed enough to tell.

Indeed.
I think we can excuse the on-site breakers and switches for failing when submerged in seawater. Maybe just nothing special would have happened without this flooding.

But, look at the second link above. You could think of the breakers at Shin-Fukushima grid station just tripped (these marked with blue cross). This would be completely normal when the line got shorted as happened.
Really, for me it is somehow hard to believe that 5 out of 6 breakers being destroyed by the earthquake only. This is sturdy stuff designed to withstand heavy blows. Just look at youtube and watch such a breaker trip.
So we do not even know enough to do more than speculate if the breakers tripped or failed. And this makes quite a difference.
I really hope it was only a translation problem and nothing worse.

Edit:
I fear I might be too optimistic.
On p. III-36, regarding Daini:

"The transmission network of external power supply of Fukushima Dai-ni NPS contain four lines including two lines of the extra high voltage switchyard on the site used in combination among Units 1 to 4 and the Tomioka Nos. 1. and 2 transmission lines outside the site (500 kV), and two line of the Iwaido Nos.1 and 2 transmission line (66 kV), and they connect to Shin Fukushima Power Substation, 8km upper, and in addition, connect to Shin Iwaki Switchyard, approximate 40 km upper. Out of transmission lines, Iwaido No.1 had been stopped power supply for maintenance.

The seismic intensity in the area around Shin Fukushima Power Substation is estimated to be 6 upper. The Tomioka No. 2 transmission line (500 kV) and the Iwaido No. 2 transmission line (66 kV) to Units 1 to 4 of Fukushima Dai-ni NPS stopped transmission due to failure restoration of devices on the side of the switchboard, etc. The Tomioka No. 2 transmission line (500 kV) and the Iwaido No. 2 transmission line (66 kV) to Units 1 to 4 of Fukushima Dai-ni NPS stopped transmission due to failure restoration of devices on the side of the switchboard, etc. caused by strong ground motion in this earthquake."

This report is somewhat clearer - massive damage on Shin-Fukushima substation...

 

[jim hardy]

fwiw - regarding switchyard breaker failures

the breakers are mostly out in the yard someplace. They are controlled remotely and the ones that affect the plant have a lot of small wires going into the plant. These wires are part of the relay logic that controls the breakers. Some relays are in the plant switchgear, some are in the switchyard.

This brings up two failure scenarios:
1. Earthquake can displace the Earth shearing buried conduits and cutting those wires, or more likely stretching them to point their insulation gets scraped away and they 'ground out' . I suspect this is one of the things Nuceng meant when he said (to effect) 'safety related cables may have failed'.
2. Relays in the plant switchgear panels likely got submerged in seawater and ceased working. Certainly they wouldn't work after station batteries ran down.

Indeed the breakers themselves are very robust devices and the term "breaker fail" only means it is unusable for whatever reason - very likely a flimsy #12 control wire scraped bare in a broken conduit, or a relay full of seawater.

hope this helps clear thought path for your continued analysis.

 

[NUCENG]

Thanks NUCENG for hinting to the convention report!

Now I have three different pictures to compare: http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf":

Looking at the image above you hinted at, I learn that the Futaba line apparently cannot be used for supplying power to the plant, as it is marked with the text "let-off only".

And, it still remains unclear where the #5/#6 switchboard can draw its supply from. From Tohoku line only, or from the other reactor's switchyards also?

It is really confusing that one document talks of "under construction", and the other talks of "under maintenance". Looking closely at the schematics, I suppose there is has in fact been only maintenance, and not construction of a new line.

BTW, I read in the report "In addition, the normal high voltage switchboard of Unit 1, the normal high voltage switchboard of Unit 2, and the normal high voltage switchboard of Units 3 and 4 were connected mutually, and electric power interchange was possible."
So I possibly was wrong in my assumption that each reactor was fixed to one single line. The above sounds like that it was possible, for example. to have reactor 2 and line 1 in maintenance, using line 2 to let off reactor 1's electric output.

Indeed.
I think we can excuse the on-site breakers and switches for failing when submerged in seawater. Maybe just nothing special would have happened without this flooding.

But, look at the second link above. You could think of the breakers at Shin-Fukushima grid station just tripped (these marked with blue cross). This would be completely normal when the line got shorted as happened.
Really, for me it is somehow hard to believe that 5 out of 6 breakers being destroyed by the earthquake only. This is sturdy stuff designed to withstand heavy blows. Just look at youtube and watch such a breaker trip.
So we do not even know enough to do more than speculate if the breakers tripped or failed. And this makes quite a difference.
I really hope it was only a translation problem and nothing worse.

Edit:
I fear I might be too optimistic.
On p. III-36, regarding Daini:

"The transmission network of external power supply of Fukushima Dai-ni NPS contain four lines including two lines of the extra high voltage switchyard on the site used in combination among Units 1 to 4 and the Tomioka Nos. 1. and 2 transmission lines outside the site (500 kV), and two line of the Iwaido Nos.1 and 2 transmission line (66 kV), and they connect to Shin Fukushima Power Substation, 8km upper, and in addition, connect to Shin Iwaki Switchyard, approximate 40 km upper. Out of transmission lines, Iwaido No.1 had been stopped power supply for maintenance.

The seismic intensity in the area around Shin Fukushima Power Substation is estimated to be 6 upper. The Tomioka No. 2 transmission line (500 kV) and the Iwaido No. 2 transmission line (66 kV) to Units 1 to 4 of Fukushima Dai-ni NPS stopped transmission due to failure restoration of devices on the side of the switchboard, etc. The Tomioka No. 2 transmission line (500 kV) and the Iwaido No. 2 transmission line (66 kV) to Units 1 to 4 of Fukushima Dai-ni NPS stopped transmission due to failure restoration of devices on the side of the switchboard, etc. caused by strong ground motion in this earthquake."

This report is somewhat clearer - massive damage on Shin-Fukushima substation...

You may be forgetting that offsite power was lost prior to the tsunami. I'm not sure whether some of the failures I discussed were only a result of the tsunami and which were there at the earthquake itself. It is fact however that offsite power was gone prior to the tsunami, so there were enough faillures from the earthquake alone to do the job.

I agree they probably meant that the line was down for maintenance, but either way it was not available.

 

[NUCENG]

fwiw - regarding switchyard breaker failures

the breakers are mostly out in the yard someplace. They are controlled remotely and the ones that affect the plant have a lot of small wires going into the plant. These wires are part of the relay logic that controls the breakers. Some relays are in the plant switchgear, some are in the switchyard.

This brings up two failure scenarios:
1. Earthquake can displace the Earth shearing buried conduits and cutting those wires, or more likely stretching them to point their insulation gets scraped away and they 'ground out' . I suspect this is one of the things Nuceng meant when he said (to effect) 'safety related cables may have failed'.
2. Relays in the plant switchgear panels likely got submerged in seawater and ceased working. Certainly they wouldn't work after station batteries ran down.

Indeed the breakers themselves are very robust devices and the term "breaker fail" only means it is unusable for whatever reason - very likely a flimsy #12 control wire scraped bare in a broken conduit, or a relay full of seawater.

hope this helps clear thought path for your continued analysis.

Thanks, Jim, that is correct. Once the wires come down into the onsite switchyard from the last transmission tower, the power busses use rigid conductors instead of cables. They no longer have enough ground clearance to allow the use of cables that would be drooping and blowing in wind. The only cables within the swichyard are as you pointed out, instrumentation and control wiring and power cables to station battery chargers, and cooling systems on transformers. Much of this instrumentation cabling provides lockout functions that trip breakers and can prevent repowering the lines. A good portion of the control circuitry is for automatic transfer functions to transfer essential power to whateve source of offsite power is available.

 

[Atomfritz]

Thanks Jim and Nuceng for the info!

So probably indeed the "failure" is not the breakers', but rather something other in their control circuitry.

I'm not sure whether some of the failures I discussed were only a result of the tsunami and which were there at the earthquake itself.

Me neither. I really need to re-read the infos about the first hour after the earthquake again.
I especially do not understand what was failing around Okuma line 1. Probably it could not be utilized due to sorts of damage Jim explained. But I ask myself, why exactly?

http://www.tepco.co.jp/cc/press/betu11_j/images/110524d.pdf". Does anybody know of an english translation?
Logs of unit #1 and #6 are in English and so quite understandable.


(semi-offtopic)

Just talked to a transmission engineer. Apparently another reason not to bury or have high voltage lines close to the ground is that it skews power factor by adding a lot of capacitance between the cables and ground. Also he reminded me that three phase power lines have to be separated from each other as well as from ground so a tunnel or trench would bave to be on the order of 9 m or larger to keep the lines separated from each other and from ground.

Hm, maybe this is one of the reasons why the major international submarine power cables seem to run on DC.
No worries with capacitance.

https://www.physicsforums.com/attachment.php?attachmentid=37019&stc=1&d=1310162658

Either HVAC or HVDC, the articles linked below say usual trench size is about 3x5 ft.
Some further reading:

• http://www.sjbenergyconnect.com/involvement/documents/SJ-Overhead_Underground_Feb-2011.pdf"
• "[URL cable company page, some basic information about long range underground/submarine
  high-power transmission, some informative pics[/URL]
• http://www.guardian.co.uk/environment/2011/apr/11/uk-netherlands-power-cable-britned"

(/semi-offtopic)

 

[Most Curious]

The rigid conductors in substations (welded aluminum pipe in most cases) would not fare well with a lot of Earth movement! Broken support insulators and transformer / breaker bushings would be likely, IMHO.

The control wiring would be subject to shearing or stretching and the control devices (relays in the power trade terminology) do not respond well to shaking.

Any of the above problems, not to mention towers collapsing, insulators failing or conductor failure, particularly if the natural resonant frequency of anything happened to be excited by the earthquake could cause massive damage. Not all of these potential problems are likely to have been predicted accurately, even if the system were carefully designed. I am actually surprised there was not more damage than has been reported.


As for buried high voltage lines, I remember a buried 138 KV line at my former employer. Thing was paper insulated in a 5" steel pipe. The pipe was mastic coated with a DC protective charge on the pipe with high pressure oil inside the pipe. Pot heads / risers for the thing were large and potentially earthquake sensitive. When our guys inquired of the installing contractor about locating faults in the line, his reply was "look for the large crater from the explosion"! I do not remember how deep it was buried but the thing always gave me the creeps to be around it. Fortunately, we never had a failure in the line other than dig-ins that damaged the protective coating. Technology has no doubt changed from that period but not THAT much. Bump up to 500 KV and the problems in building a reliable underground circuit would multiply as well.

 

[westfield]

In case its not been linked - http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110615e11.pdf"-

 

[jmelson]

I have never seen buried applications of high energy transmission lines, but I'm not rejecting your idea. I'm thinking it may be a lot better to really amp up backup supplies,on site or close by, that can be done at 480 or 1600 VAC which covers the onsite voltages for the big loads.

It is done, in special cases, like running under bays and such. They pump oil through the conduit to cool the cable, and provide insulation as well. It is a huge complication, and it has to be insanely expensive to do it any other way before it becomes affordable to use underground HT mains.

Jon

 

[tsutsuji]

It is really confusing that one document talks of "under construction", and the other talks of "under maintenance". Looking closely at the schematics, I suppose there is has in fact been only maintenance, and not construction of a new line.

On a road sign, the same Japanese word means "work ahead", be it a new work or a repair work.

This report is somewhat clearer - massive damage on Shin-Fukushima substation...

The list of damages at Shinfukushima substation is provided at http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e18.pdf . The referred pictures are at http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e19.pdf .

Thanks NUCENG for hinting to the convention report!

Now I have three different pictures to compare: http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf":

Looking at the image above you hinted at, I learn that the Futaba line apparently cannot be used for supplying power to the plant, as it is marked with the text "let-off only".

And, it still remains unclear where the #5/#6 switchboard can draw its supply from. From Tohoku line only, or from the other reactor's switchyards also?

I wonder what the meaning of the dots on this image from convention report page III-42 is. If I follow http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf, the Yonomori line should be shown going all the way to the Shinfukushima substation. The repair work connecting Yonomori line No. 1 and Ookuma line No.3 is mentioned as "work 6" on http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf and it is clearly outside the plant, while the dots on page page III-42 of the report are inside.

According to http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf , Work 6 seems to consist in connecting Ookuma tower No.7 with Yonomori tower No.8 (or the other way round Ookuma tower No. 8 with Yonomori tower No. 7 : the "Tower(s) No. 7.8 (No. 7.8 鉄塔)" wording is ambiguous).

Edit : Work 6 is also mentioned on page 3 of http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e26.pdf where they say "Transmission Tower №7 and 8 of Okuma Transmission Line 3 and 4L: Connection of Okuma Transmission Line 3L and Yonomori Transmission Ligne 1L started.【Work⑥】".

Page III-42 says the image is based on http://info.nicovideo.jp/pdf/2011-03-18_1930_touden_genpatsu.pdf where only one tower is shown and the connection is made between two lines on the same tower. See image below :

I have no idea if he is correct, but according to Martin Gugino who tried to map the power lines using satellite views on http://commons.wikimedia.org/wiki/File:FukushimaGrid.JPG , the Yonomori line is "a shared tower with the second Okuma towers". What adds to the mystery is that Yonomori is a village located South from the plant and one wonders why the power line is called with that name if it does not actually run through that village. See also what Martin Gugino says after "I speculate that" on http://commons.wikimedia.org/wiki/File_talk:FukushimaGrid.JPG .

The 1/25000 map at http://watchizu.gsi.go.jp/watchizu25.html?longitude=141.030889&latitude=37.429553 shows only 3 lines going from the plant to Shinfukushima substation, not making the distinction between Futaba line and Yonomori line and does not locate the towers, but perhaps it could help.

Page III-42 of the report aslo refers to http://www.tepco.co.jp/nu/kk-np/info/tohoku/pdf/23032202.pdf (this is a report from Kashiwazaki-Kariwa, not translated into English, as far as I know) where the figure page 3 shows 4 pairs of lines, with 4 rows of towers depicted with "☒" boxes and named from left to right Ookuma 4, Ookuma 3, Ookuma 2, Ookuma 1, Yonomori 2, Yonomori 1, Futaba 1, Futaba 2. That figure marks tsunami damages with red crosses and ignores earthquake damages such as the collapse of Yonomori tower No. 27.

 

[NUCENG]

On a road sign, the same Japanese word means "work ahead", be it a new work or a repair work.



The list of damages at Shinfukushima substation is provided at http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e18.pdf . The referred pictures are at http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e19.pdf .



I wonder what the meaning of the dots on this image from convention report page III-42 is. If I follow http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf, the Yonomori line should be shown going all the way to the Shinfukushima substation. The repair work connecting Yonomori line No. 1 and Ookuma line No.3 is mentioned as "work 6" on http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf and it is clearly outside the plant, while the dots on page page III-42 of the report are inside.

According to http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf , Work 6 seems to consist in connecting Ookuma tower No.7 with Yonomori tower No.8 (or the other way round Ookuma tower No. 8 with Yonomori tower No. 7 : the "Tower(s) No. 7.8 (No. 7.8 鉄塔)" wording is ambiguous).

Page III-42 says the image is based on http://info.nicovideo.jp/pdf/2011-03-18_1930_touden_genpatsu.pdf where only one tower is shown and the connection is made between two lines on the same tower. See image below :

I have no idea if he is correct, but according to Martin Gugino who tried to map the power lines using satellite views on http://commons.wikimedia.org/wiki/File:FukushimaGrid.JPG , the Yonomori line is "a shared tower with the second Okuma towers". What adds to the mystery is that Yonomori is a village located South from the plant and one wonders why the power line is called with that name if it does not actually run through that village. See also what Martin Gugino says after "I speculate that" on http://commons.wikimedia.org/wiki/File_talk:FukushimaGrid.JPG .

The 1/25000 map at http://watchizu.gsi.go.jp/watchizu25.html?longitude=141.030889&latitude=37.429553 shows only 3 lines going from the plant to Shinfukushima substation, not making the distinction between Futaba line and Yonomori line and does not locate the towers, but perhaps it could help.

Page III-42 of the report aslo refers to http://www.tepco.co.jp/nu/kk-np/info/tohoku/pdf/23032202.pdf (this is a report from Kashiwazaki-Kariwa, not translated into English, as far as I know) where the figure page 3 shows 4 pairs of lines, with 4 rows of towers depicted with "☒" boxes and named from left to right Ookuma 4, Ookuma 3, Ookuma 2, Ookuma 1, Yonomori 2, Yonomori 1, Futaba 1, Futaba 2. That figure marks tsunami damages with red crosses and ignores earthquake damages such as the collapse of Yonomori tower No. 27.

I think the doublr slash is a cable failure and the dots show repair connections.

 

[tsutsuji]

I think the doublr slash is a cable failure and the dots show repair connections.

According to the key on the top right corner of the page (http://info.nicovideo.jp/pdf/2011-03-18_1930_touden_genpatsu.pdf page 4), straight red lines mean "completed work" and red dotted lines mean "work to be performed in the future". The handwritten note adds "as of 17 March". I guess the double slash mean "disconnected jumpers" as the key in http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e25.pdf mentions.

The only instances of cable failures I have heard of are those mentioned on http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e17.pdf :

* "cable damage" between the Tohoku electric 66 V line and unit 1
* Okuma 3L "overhead line broken" inside shinfukushima substation, referred to as "ground wire disconnected" on page 1 of http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e19.pdf
* The Yonomori tower No. 27 collapse

Pages 8 and 9 of http://www.tepco.co.jp/cc/press/betu11_j/images/110524d.pdf explain why the breakers tripped :

Okuma 1L : breaker O-1 trips because of the damage of breaker O-81
Okuma 2L : breaker O-32 trips because of the damages of breaker O-82 and disconnector O-82
Okuma 3L : breaker O-33 trips because of the arc at tower No. 7 (arc traces were observed, showing a conductor touched or came close to the tower)
Okuma 4L : breaker O-34 trips because of the arc at tower No. 11 (arc traces were observed, showing a conductor touched or came close to the tower)
Yonomori 1L : breaker O-93 trips because conductors touched or came close to each other. Also, Yonomori tower No. 27 collapsed.
Yonomori 2L : breaker O-94 trips because conductors touched or came close to each other. Also, Yonomori tower No. 27 collapsed.

 

[tsutsuji]

Edit:
They operate part of Yonomori 1 line at 6kV, using a portable transformer (see Work 3,4,9) to transform from 66 to 6.
Maybe because in March the roads were in no shape to transport a big transformer on a truck convoy?
I am still guessing why they did this. Maybe it was the fastest way to get a handy low voltage to operate with?

On pages 64 and 65 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110525_01-e.pdf , there are a few explanations on the different power voltages used at the plant. The diesel generators supply 6.9 kV, and some equipments can use this 6.9 kV directly. Then the voltage is lowered to 480 V for some other equipments. Some yet other equipments use DC 125 V.

I wonder if they actually mean 6.9 kV when they write 6 kV or if they mean exactly 6.0 kV.

 

[Atomfritz]

I think the doublr slash is a cable failure and the dots show repair connections.

In electrical engineering the double slash means "line cut". Didn't ever find an other meaning, even though schematics are drawn differently around the world.

No matter whether for revision, modification etc.
Just my 2 ct, as my profession is electronics engineering and when dealing with apparatuses you always have to keep in mind what version they are of.

@ tsustsuji-san:
Thank you for the links!
I have to admit that I didn't see these detailed pics before. This damage on Shin-Fukushima really shocks me. (Please don't misunderstand me, in Germany we know such damage only from former foreign bomb raids...) I really have to sleep over all this information before I can digest it and get clear thoughts about the whole thing.

Edit:

The diesel generators supply 6.9 kV, and some equipments can use this 6.9 kV directly. Then the voltage is lowered to 480 V for some other equipments. Some yet other equipments use DC 125 V.

I wonder if they actually mean 6.9 kV when they write 6 kV or if they mean exactly 6.0 kV.

In fact this is not very important due to the tolerances. Under-overvoltages of +-20% are usually of no problem. So you usually can supply a 6kV transformer primary with 7kV without noticing an adverse effect on the secondary (except higher consumption and wear), and vice versa.

 

[jim hardy]

this is more trivia, but it helps one's thought processes to not let these little questions pile up unanswered for they chip away at our confidence.

so i'll cast a little light on this one:
"I wonder if they actually mean 6.9 kV when they write 6 kV or if they mean exactly 6.0 kV. "


4160 and 6900 volts are two very common standard voltages. With higher voltage you need less copper but better insulation. As plant designs require ever bigger motors the wire sizes required become unmanageably big. Biggest motor in my plant was 7,000 hp and we were 4160, those wires looked like firehoses. They are difficult to install and copper is today ~ $4 a pound.It's almost certain they are referring to nominal 6.9kv equipment. We tend to name things colloquially, 4kv and 6kv is how we referred to ours though 7kv would have been more accurate.

The tolerance Atomfritz mentioned is important to the plant. We have to float up and down a few percent according to system load.
Power company tries to deliver constant voltage to the customer. On days with high demand the plants will raise their voltage a bit to overcome voltage loss in the transmission wires & transformers, and on easy days lower voltage somewhat. That's all directed from a central system control office.

We always said "Our in-plant power is not nearly so stable as what the customer sees".

old jim

http://www.resourcesaver.com/file/toolmanager/O105UF493.pdf

 

[Lambert]

oh oh

http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc0004sg6.php

http://www.vancouversun.com/news/Quake+jolts+northeast+Japan+nuclear+workers+evacaute/5079075/story.html

 

[Gary7]

Was about a magnitude 4 (Japanese scale) in Fukushima. Fukushima Daiichi reported no damage as a result of this quake. Tsunami was about 10 centimeters in Fukushima.
Tsunami alert has been lifted.

 

[joewein]

Was about a magnitude 4 (Japanese scale) in Fukushima.

The Japanese "shindo" scale is usually translated as "intensity" or "seismic intensity" in English (you don't say "magnitude" unless you mean the Western scale that measures energy released, which is sometimes incorrectly referred to as "Richter scale").

It's listed as M7.1 here:
http://www.jma.go.jp/en/quake/20110710100736491-100957.html

That's almost 1000 times less energy than the M9.0 quake on March 11. I still felt it here in Tokyo and it was fairly long but quite weak here, unlike 3/11. Only half of my family noticed it at all.

 

[tsutsuji]

Edit:
They operate part of Yonomori 1 line at 6kV, using a portable transformer (see Work 3,4,9) to transform from 66 to 6.
Maybe because in March the roads were in no shape to transport a big transformer on a truck convoy?
I am still guessing why they did this. Maybe it was the fastest way to get a handy low voltage to operate with?

So this 6kV is another name for the 6.9 kV which they need at the plant. You need to lower that 66 kV into this 6 or 6.9 kV some way or other. My guess is that they wanted to work as far away from the plant as possible, rather than risk the workers' lives in a contaminated plant where hydrogen explosions occur every couple of days.

Was about a magnitude 4 (Japanese scale) in Fukushima. Fukushima Daiichi reported no damage as a result of this quake. Tsunami was about 10 centimeters in Fukushima.
Tsunami alert has been lifted.

http://mainichi.jp/select/jiken/news/20110710k0000e040029000c.html During the tsunami alert, workers evacuated the area close to the sea and the megafloat filling operation was stopped.

[URL]http://www.tepco.co.jp/en/news/110311/images/110710_1t.jpg[/URL]
http://www.tepco.co.jp/en/news/110311/images/110710_1.jpg

It had been a long time since they last had a trouble at the water treatment facility.

http://www.jiji.com/jc/c?g=soc_30&k=2011071000054 : It had to stop at 4:50 AM because of a chemical leak at the Areva facility. A green coloured chemical burst out at the junction of the chemical hose and the (contaminated water?) pipe. The amount leaked is 50 l. The chemical is not poisonous but some contaminated water could have leaked too. It is the first trouble since 30 June.

http://mainichi.jp/select/jiken/news/20110711k0000m040021000c.html the leak was viewed on a surveillance camera at 4:53 AM. The facility was started again at 5 PM after the junction was changed for a cast iron one. The leaked liquid's radiation was 5500 Bq/cm³ of Cs-137 which is a normal radiation at the entrance of the Areva system and a hint that contaminated water flowed backwards through the leak. Tepco is studying what to do with another similar junction located elsewhere in the facility, beyond a visual inspection showing it is not leaking. The megafloat filling will start again on 11 July.

http://www.asahi.com/national/update/0708/OSK201107080148.html In a symposium in Tokyo, Kyoto university reseachers presented a water decontamination method they claim is cheaper and faster, and produces less waste than the one used at Fukushima Daiichi. It is based on the flotation method used in the mining industry. You add Fe or Ni, and chemicals that help separate Cs from water and precipitate the Cs. Then you add bubbles from the bottom, and the Cs rises to the surface with the bubbles. Then you skim the foam. Their tests with 5 different contaminants show that more than 99% can be removed.

 

[Bioengineer01]

It appeared that the screwup that I had discovered had never made it to the top bosses because nobody wanted it known that it was a problem that was easily corrected with people doing their jobs in an attentive fashion.

Joe, I have been in several situations similar to what describe but in the pacemaker/defibrillator industry of medical devices. And always the screw-ups got to the top the bosses, but never in writing (so that they could deny knowing), but never to the board of Directors, because it would have made them look bad. It is possible that your fix was known by your top brass, but that they had already told the board that it was a system problem and had already requested approval for the expenditure for the new system.

 

[Bioengineer01]

It is this human nature issuer you describe that makes me question the safety and wisdom of nuclear reactors, situated close to population centers and valuable real estate.

I did a back of the envelope reliability analysis similar to those we do for medical devices and calculated what is the reliability level that the worst Nuclear Power Plant (and associated systems, like power lines) should have to have a 99% probability level that NO nuclear plant will have a catastrophic failure in the next 30 years. The number is scarely close to 100%. I am not a reliability person, but if you know of anybody, please invite him/her to destroy my guestimates here. When I brought that system reliability number down, it very quickly trended to 100% probability of one catastrophic failure every thirty years...

 

[Bioengineer01]

The reaction of worldwide nuclear community up to now is mostly PR. PR is not going to convince me. I need to see deeds, not words.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled", said Richard Feynman, and I fully agree with him.

I completely agree with Nikkom perspective. It is unbelievable how close the analogy is to implantable medical devices too. Where the shuttle accident reports were evaluated in detail and lessons learned. Sadly the reality always was that before the money was invested, every lesson was used correctly and the burden of proof was on the engineers to prove it was safe, but after the product was launched commercially, then the burden of proof was shifted to "prove to me it is unsafe". Most recalls in the implantable medical device industry have been made a lot worse by this behavior. NPPs are in the post commercial launch situation and thus the mentality is prove it is unsafe before I do something. That is not the mentality of the patient that has the device or the public that will suffer the consequences of failure.