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#136684 - 04/28/03 01:35 PM Variable frequency power plants  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
This is cool

-----------------
Summer blackout plan hits a snag

The Asahi Shimbun

TEPCO wants to buy 60 Hz power to avoid a shortage. But Tokyo uses 50 Hz.

Tokyo Electric Power Co. is hoping to avoid an energy crisis in the nation's capital this summer by buying power from other suppliers. But the fact Japan's power grid operates on two different frequencies will make that a difficult task.

TEPCO has had to shut down all 17 of its nuclear reactors for safety inspections, and if they are not put back in operation soon, the firm could fall 9.5 million kilowatts short of capacity, an amount equivalent to the output of 10 reactors.

Because eastern Japan, including Tokyo, runs on 50-herz power while western Japan is on 60 Hz, some of the power TEPCO purchases will have to be converted. Existing converters, however, can only handle the equivalent of the output of one nuclear reactor.

The Ontake and Nezame hydroelectric power plants operated by Kansai Electric Power Co. are among the few facilities in Japan that can generate power at either 50 or 60 Hz. They are located on the Kiso River in Nagano Prefecture and use runoff water from the Japan Alps. The two stations generated power at 60 Hz until March for the Kansai area, but switched to 50 Hz from April 1 to send 50,000 kilowatts to the Tokyo area.

Such power plants are the exception. Usually when power is sent from western Japan to the Tokyo metropolitan area, it has to pass through one of two frequency conversion facilities in Nagano and Shizuoka. Their total capacity is 900,000 kilowatts. The electricity industry has established frequency conversion facilities to prepare for emergencies, but only on a scale equivalent to losing about one nuclear reactor. Shutting down 17 reactors simultaneously was completely beyond expectations.

The combined output of the seven power companies on the main islands, aside from TEPCO and Chubu Electric Power Co., which has shut down three nuclear reactors, is 97 million kilowatts.

The seven utilities are expected to see a peak demand of 86 million kilowatts, averaged over a three-day period, leaving them a surplus of 11 million kilowatts. In theory, if power plants were run at full output and excess energy was sent to the Tokyo area, the electricity crisis could be avoided.

In reality, however, the requirement for frequency conversion will make just over 10 percent of that surplus available to TEPCO.(IHT/Asahi: April 22,2003)


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#136685 - 04/29/03 02:02 AM Re: Variable frequency power plants  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
C-H,
That's unusual, having two different mains frequencies in the same country.
You'd have to watch it if you were regularly replacing motors around a country like that!.


#136686 - 04/29/03 11:44 AM Re: Variable frequency power plants  
classicsat  Offline
Member
Joined: Nov 2002
Posts: 456
Not really, design the motor to work on both frequencies, and install an appropriate sized
or sprocket pulley to get the proper RPMs to the load.
Hi-tech electronics are easy to, just use a crystal based oscliiator, instead of referencing to the power line.

What seems silly to me though, is why they never stepped the shutdown/inspection/possible maintenance
of the plants, unless they are in dire need
of inspection/repairs. In that case, why were
they left to get in a position where the only thing to do would be a shutdown.


#136687 - 04/29/03 12:01 PM Re: Variable frequency power plants  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
The the only reason I can imagine that would force the shutdown of all reactors is some kind of nuclear scandal. Japan has had a number in the past.


#136688 - 04/30/03 02:36 AM Re: Variable frequency power plants  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
C-H,
Has Japan had nuclear problems in the past?.


#136689 - 05/01/03 11:09 AM Re: Variable frequency power plants  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
Yes, it has. Worse, Tepco (the company above) and others have tried to conceal them. Luckily, nothing serious so far. (A few dead workers)

An article from an Australian newspaper explaining the background



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