Japanese Powergrid 50/60hz, debate on what to install after the disaster.

[Ed.Kloonk]

http://flyjin.com/japanese-power-grid-primer/

As many of us know, Japan has two different energy grids, a 50 Hz system for Tokyo and the east, and a 60 Hz system for Osaka and the west. Originally, in the late 19th century both Tokyo and Osaka were 60 Hz, because they used generators from the U.S. But when Tokyo’s generator conked out, they replaced it with a 50 Hz German generator, and from that fateful day the country was electrically divided. Because electricity in the early days was mostly used for incandescent lights, which are somewhat frequency agnostic, the difference didn’t seem that important, but nowadays you need different models of equipment for the two areas.

Although it’s possible to convert between the systems, current capacity is very limited. There is talk of increasing this, but Hikosaemon thinks now is the time to just bite the bullet and bring Tokyo and the east into a 60 Hz system. Maybe the factories to make all the new appliances could be built in the tsunami affected area to give them some jobs?

What do you boys think?

[Bored@Work]

Which frequency they end up with doesn't matter. The big freaking task at hand and challenge is to get the politics, bureaucratic, economic and organizational issues under control to modernize the grid.

The moment you see excessive debates regarding the final frequency is the moment you know that there are forces at work who aren't interested in fixing the problems, but instead having an own agenda.

[Zero999]

Most appliances don't care whether it's 50Hz or 60Hz. The only ones which do use induction motors run direct on line (not off an inverter) or the mains as a timebase. Fortunately most household appliances use a universal motor and I would've thought that devices designed for Japan either wouldn't use the mains as a timebase or would have switch.

If they need to standardise, I think they should go with 60Hz because it's easier for transformers to work on higher frequencies rather than lower.

[saturation]

Interesting historical topic, how did 50 vs 60 Hz ever get established and which is technically more efficient?

http://en.wikipedia.org/wiki/Utility_frequency

DC driven appliances use PSU that are multiple voltage or frequency, but a problem arises with AC motor driven appliances like washing machines or blenders.  This is much worse at the industrial level.

After reading the Wiki article, it looks like it will be a political process weighing established industrial bases of machinery in the area. 

[Zero999]

I've never seen a blender with a true AC motor, all the ones I've seen use a universal motor which will work the same off 50Hz or 60Hz - induction motors are too big and bulky for most small household appliances.

This is less of a problem today as inverter driven motors have become more and more widespread - most washing machines and air conditioning units now use them. Changing to the frequency would effect ridges, freezers and clocks though.

In my opinion, if the whole power system could be redesigned from scratch, DC would be used because power transmission is more efficient due to lack of skin effect and radiative losses and it can now be stepped up or down in voltage with efficient DC-DC converters rather than large power transformers.

[elCap]

I'm living in Japan and have moved a few times from south of Japan (Kyushu) to Tokyo, and now in Kansai area. In frequency that is 60 to 50, back to 60Hz. I have never had any problem with the electric equipment. Although I cannot say I checked it that carefully, and there are no complains from the wife!

For me personally there are two aspect of the different frequencies used. First, I think it's kind of strange and should be corrected. On the other hand now after the earthquake, there is no black-outs or power savings going on in Kansai area. And as I have a daughter in the hospital it gives me one less thing to worry about.

Also the power savings going on in the Kanto/Tokyo area seems to increase the demand for low power equipment. And the need is urgent. This will probably bring on some new technology and products. Future will tell.

[quantumfall]

In my opinion, if the whole power system could be redesigned from scratch, DC would be used because power transmission is more efficient due to lack of skin effect and radiative losses and it can now be stepped up or down in voltage with efficient DC-DC converters rather than large power transformers.

I always was under the impression that the skin effects only made a noticeable difference at high frequency, what sort of losses are there ?

I presume you would still need a very high distribution voltage to keep the current needed to a reasonable level for the cables used, unless you could use superconductors , do they not have current limits though ?

Would you need hundreds of thousands of volt DC-DC high current systems, are they available or would they need development ?

[Ferroto]

Can't they just flip a coin. 

[rf-loop]

In my opinion, if the whole power system could be redesigned from scratch, DC would be used because power transmission is more efficient due to lack of skin effect and radiative losses and it can now be stepped up or down in voltage with efficient DC-DC converters rather than large power transformers.

I always was under the impression that the skin effects only made a noticeable difference at high frequency, what sort of losses are there ?

I presume you would still need a very high distribution voltage to keep the current needed to a reasonable level for the cables used, unless you could use superconductors , do they not have current limits though ?

Would you need hundreds of thousands of volt DC-DC high current systems, are they available or would they need development ?

In world there is lot of UHVDC transmission line projects. Some are ready oin use, some are onder construction and some are planned. Example in China there are lot of these projects. (also other very interesting power grid systems)
one small example: http://www.abb.fi/cawp/db0003db002698/d765a96b5818c2d8c1257784004f8783.aspx
(Xiangjiaba - Shanghai ±800 kV UHVDC transmission project)

Some other example: http://tdworld.com/overhead_transmission/siemens-china-hvdc-link-0610/
(The Yunnan-Guangdong UHVDC system, First 800-kV HVDC Link in China Now Fully Operational)

[jahonen]

I always was under the impression that the skin effects only made a noticeable difference at high frequency, what sort of losses are there ?

For thick cables, this is relevant also at 50/60 Hz. Skin depth for copper at 60 Hz is 8.5 mm according to wikipedia, so it does not make sense to make single conductor thicker than 1-2 cm, anything more is waste of material.

Regards,
Janne

[quantumfall]

Well I'm shocked, I was always under the belief that power used AC distribution.  You live and  learn.  Thanks for the replys.

[Zero999]

Yes, DC is only used over very long distances. There are also other advantages such as lower dielectric and radiative losses

Although I think switching to DC for the domestic supply would be good in theory, it's just not practical because many appliances would either need to be replaced or run off an inverter.

[Zad]

It isn't that long ago that we had DC supplies here in the UK. I think it goes back to the pre- national grid days when each area had it's own power generation company. As recently as the early 1970s London still had a DC system. I think it was as low as 100V but wouldn't swear to it. Mostly used for electric motors in lifts etc. Not only that, but it had hydraulic power too! Used for similar systems, running at 800psi. It only closed in 1977, with much of the hydraulic pipe system being used to carry fibre optic cables now.

[FreeThinker]

The question should be are they going to continue building Nuclear power stations on a fault line?. They got away with it this time (Just) but the cost were, are and will continue to be for a very long time, extremely high in both human and environmental terms. The conspiricy of silence is frightening. Compare the press coverage of Chernobayl and the Japanese disaster and you will see what I mean. I believe the alert level got as high as 3 which is I think the highest every recorded but the world just seemed to ignore it or brush it under the carpet. Why? Is wise to allow the same mistakes to be repeated? Chernobyl lives on, we still have a charity shop in town that sends a lorry with aid (clothing, blankets, Toys household items etc) every month or so even today.....and it is still needed. The worlds response to the Japanese was 'How will this affect my Nissan' or to grab some market share to cover shortfalls. This disaster will live long and bite hard and we all should learn lessons from it.

[TheWelly888]

It isn't that long ago that we had DC supplies here in the UK.

There was a DC cable from Kingsnorth power station to Willesden in North London, it used mercury arc rectifiers.

http://www.theiet.org/forums/forum/messageview.cfm?catid=226&threadid=3247&highlight_key=y Here is a brief forum thread on the IET website about it.

[hannobisschoff]

By the way, which one was first, 60 or 50 HZ, and why the international difference?

[scrat]

In my opinion, if the whole power system could be redesigned from scratch, DC would be used because power transmission is more efficient due to lack of skin effect and radiative losses and it can now be stepped up or down in voltage with efficient DC-DC converters rather than large power transformers.

Although it would be technically possible to use only DC, there are still some little advantages of AC over DC (besides the use of asynchronous motors directly fed by AC), IMO. First of them is the electro-mechanical switches size can be smaller for AC. Then, a transformer is still much simpler than the simpler DC-DC converter, which would make a difference in developing countries and other places where maintenance after a fault is difficult (it's usually easier to make a reliable thing if it is simpler, and it's also easier to repair).