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Opinion

The Great East Japan Earthquake

Massive Blackouts and Preventive Measures

Shinichi Iwamoto
Professor, Faculty of Science and Engineering, Waseda University

Are we overly dependent on electricity?

Yes, we most certainly are. With doors powered and toilets flushed by electricity nowadays, there must be many people who would be at a loss if the power were to go out suddenly. Until several decades ago, we had no air conditioners, and the contracted amperage in those days was generally 10. As the standard household voltage is 100 volts, the power was 1,000 watts calculated by multiplying 10 amperes by 100 volts, in other words, 1 kilowatt contract back then. In addition, when there were no air conditioners during the summer, people lost their appetites because of the heat and lost weight naturally, so there was no need for the slimming diets that we have today. Nowadays, I think one family has at least three air conditioners. One air conditioner requires approximately 10 amperes at the time of maximum power consumption, which causes the contracted amperage to grow to 40 amperes (4 kilowatts), determined by adding 30 amperes to the original 10 amperes. Assuming that a family consists of four members, for example, 4 kilowatts are required for the four members during the summer-i.e., 1 kilowatt per person. Now, what does it mean that one nuclear generator is capable of supplying 1 million kilowatts? It means that the generator alone is able to supply electricity for one million people.

Is there a shortage in the supply of power this summer?

In so far as Tokyo Electric Power Company (TEPCO) goes, it can only be described as a state of emergency. The Great East Japan Earthquake stopped six nuclear generators at Fukushima Daiichi (total of 4.7 million kilowatts from reactor No. 1 to No. 6) and four at Fukushima Daini (total of 4.4 million kilowatts from rector No. 1 to No. 4) from working. Because there is no chance that these generators may be restarted this summer, 9.1 million kilowatts of power-the combined capacity of Fukushima Daiichi and Daini-suddenly disappeared beyond the scope of the assumption. As previously mentioned, 1 kilowatt per person is required during the summer, which indicates a sudden loss of power supply for 9.1 million people this time. Tokyo has a population of approximately 13 million, which means that power equivalent to the amount for about 70% of its population is gone at all once. Another concern is that nuclear power plants are obliged to stop for a periodical inspection every 13 months, and in order to resume, permission must be obtained from the Nuclear and Industrial Safety Agency, as well as the consent of local residents including the prefectural governor. Due to the effects of the nuclear accident at Fukushima Daiichi, it is very uncertain whether the prefectural governor and local residents in the vicinity of any nuclear plant will consent to the restart of such a plant, and what will happen in the future. If the restart of nuclear power plants is difficult, one may think of the possibility of immediate thermal power plant construction, but it takes five to ten years to build a high-efficiency thermal plant for utilities.

Can't the power be supplied by other utilities?

The maximum amount of about 600 thousands kilowatts and about 1 million kilowatts can be diverted respectively from Hokkaido Electric Power Company and from or via Chubu Electric Power Company. It is often said that the power cannot be supplied because of the frequency difference-i.e., 50 hertz at TEPCO, and 60 hertz at Chubu Electric Power Company and Kansai Electric Power Company-but this is a misunderstanding. If the frequency is converted from 50 hertz to 60 hertz or vice versa, power can be interchanged. At present, approximately 1 million kilowatts can be obtained from or via Chubu Electric. The reason this is the maximum amount is that the tie-line (transmission line) capacity is limited to about 1 million kilowatts. The tie-line capacity can be compared to the diameter of a water pipe. A pipe with a larger diameter allows a larger amount of water to flow, but one with a small diameter allows only a small amount to flow, and this is the same theory with the tie-line capacity. Some may suggest that they should install additional tie-lines and frequency conversion equipment, but it is said such installation requires approximately 10 years and 100 billion yen. Construction of tie-lines (transmission lines) in particular involves such issues as land acquisition and land use, which requires a lengthy period of time.

What is the difference between a normal blackout and this feared massive blackout?

The biggest difference is that sufficient capacity for power supply is assured in the former case, while capacity is insufficient in the latter. Let us assume that power lines were cut for some reason, for example, and the power went out at substations and for household consumers. What happens then is to perform system switching so that electricity can be provided from other uncut lines. Although this is an unlikely example at home, it is the same with a case where another wall outlet could be substituted for an unusable one. The system is switched by hand or automatically, but it takes 10 to 15 minutes for manual switching per substation. A while ago, a crane on a crane ship struck some power transmission lines, triggering a blackout and affecting five substations, and the restoration process took 59 minutes. The above would be a convincing explanation for why it took 59 minutes. On the contrary, however, this feared massive blackout occurs when there is not enough power supply capacity. That is, it occurs in a case of imbalance between power supply and demand. The quality of electricity is determined by constant frequency and voltage, and it is particularly the frequency that makes all the difference this time. Again, the frequency is set at 50 hertz in the TEPCO service areas, as previously mentioned.

What does the frequency of 50 hertz mean?

In a generator, a magnet with a north and a south pole rotates 50 times per second especially at a thermal power plant to generate electricity. One rotation generates one cycle of electricity. Fifty cycles of electricity per second is referred to as electricity at a frequency of 50 hertz. In the TEPCO service areas, all generators rotate to produce electricity at a frequency of 50 hertz, where the heavier load (larger demand) causes the frequency to drop. All electric equipment is manufactured based on the frequency of 50 hertz, and the excessively low frequencies result in problems including instability in products as well as harmful effects on turbines, which rotate generator shafts. Under stable conditions, therefore, the frequency in the TEPCO service areas is controlled to remain within the range of 50 ± 0.2 hertz. And when excessive loads (demands) lead to extremely low frequency, UFRs (Under Frequency Relays) as protective relays detect the decline of frequency and send signals to circuit breakers, so that the circuit breakers are open to lessen loads (demands). This is how a blackout takes place. A chain reaction of these grows to a massive blackout. A series of blackouts occurs, for example, starting with a load rejection of A kilowatts at 48.X hertz, and then a load rejection of B kilowatts at 48.Y hertz.

Is a prompt recovery from a massive blackout difficult to achieve?

A prompt recovery is impossible. It took two whole days at the time of the 2003 North America blackout. The scale of this massive blackout was 62 million kilowatts, almost the same as the total summer demands in the TEPCO service areas. However, one of the reasons why the recovery took this long during this massive blackout in North America might have been that their power supply system was different from ours, in that the electricity producer, transmission company, and grid operator were all separate entities. TEPCO would probably be able to restore the electricity much sooner. For recovery, a frequency monitoring section of the utility provides substations with an order to close the circuit breakers while checking if enough capacity is assured to meet the demands. If it is determined that there is no supply capacity, the blackout continues.

How to avoid a massive blackout

When urgent countermeasures are required, nothing is effective except planned outages (commonly knows as rolling blackouts). Therefore, the planned outages were implemented this time, however various problems emerged with trains, traffic signals, factories, medical institutions and other such issues, as you know. A complaint was voiced on the fact that power went out at one family's house but it did not at its next-door neighbors' in the same ward, and this all depends on the substations which these families are connected to. Some may wonder if there is another way other than planned outages, and one solution is the total volume control of electricity, which is scheduled to be implemented mainly this summer. Roughly speaking, the total volume control is to set the maximum electric power (kilowatt) and the maximum electric energy (kilowatt-hour) and observe them. At a factory, for example, 24 hours can be divided in thirds to have three different teams work every eight hours in order to equalize the power usage and reduce the peak power. In cases where this is impossible, efforts should be made to cut the peak power to reduce the maximum instantaneous power.

How to prevent a massive blackout

The way considered most effective is to stop using air conditioners, as mentioned at the beginning of this article. An air conditioner uses about 1 kilowatt at the time of maximum consumption (about one-sixth once the preset temperature is reached). On the other hand, an electric fan with a blade diameter of 30 centimeters only requires about 30 watts. For your reference, it is said that the combined use of an electric fan and an air conditioner with its preset temperature raised by 1 属C reduces the power by about 10%. The next possible way is lighting. It is effective to use LED bulbs instead of incandescent or fluorescent lights. Other than the above, the countermeasures include turning off toilet seats with a warm-water shower feature, vending machines, and the warming function of electric kettles, and using heat shield films on windows. Businesses and universities in particular can appoint a person responsible for monitoring and controlling the maximum electric power and energy and to have him/her monitor the electricity usage curve, and take action such as making an emergency announcement when the maximum electric power is almost reached, for example. It is better to provide an exclusive circuit for the power supply of air conditioners, and monitor and control it. If a massive blackout occurs, extra attention must be paid to elevators. It is critical to fully check in advance whether an emergency actuation device for the elevator properly works to prevent people from being trapped in the elevator at the time of a sudden blackout. TEPCO should do more other than boosting its power supply capacity in order to avoid a massive blackout. I think they should insert tickers or emergency electricity warnings on TV immediately when a massive blackout is likely to occur, for example, instead of holding their breath while watching a supply and demand curve. Such emergency bulletins will prompt residents to reduce their electricity usage, so that a massive blackout can be prevented.

Last precautions

It is now reported that TEPCO's power capacity has been gradually increasing, and exceeded 55 million kilowatts, which is the power demand estimate by TEPCO for this summer. I wrote in the first half of this article that it takes 5 to 10 years to newly construct a thermal power plant and install additional transmission lines, and it is not something that can be done immediately. But why is TEPCO's power supply increasing? Indeed, this is partly due to restarting operations at a thermal power plant which has been idle, restoring the thermal power generators affected by the Earthquake, and newly building gas turbine generators, but mainly because pumped storage power generation has been included as available supplies. In pumped storage power generation, reservoirs are built at the top and bottom of a mountain respectively, and water is pumped from the lower elevation reservoir to the higher elevation mainly using electricity produced by nuclear power generators at night, and the stored water is released from the higher reservoir to the lower reservoir as needed during the daytime, which allows only six hours of power generation. It is different from the 24-hour nuclear power generation. Shortly after the Earthquake, there was actually not much power for use during the night, however the amount of water to be stored at night has increased with gradual restoration of thermal power generators. According to a recent announcement, pumped storage generation produces 6.5 million kilowatts. The significance of this development, however, is not simple. Although pumped storage generation used nuclear power generation which emitted very low amounts of CO2 until now, at present, it substantially depends on aging thermal power facilities which were idle, and emits large amounts of CO2 during the night, subject to breakdown at any time. It is necessary, therefore, to fully understand that the figures of the power supply before and after the Earthquake are different in their nature, and they involve uncertainty. It is estimated that Tohoku Electric Power Company, which was affected by the Earthquake, also faces a power shortage this summer, and TEPCO could assist Tohoku Electric Power Company with its surplus power if available. What we can do is strive first to save on electricity in order to prevent a massive blackout in the TEPCO service areas, and then to create a situation in which TEPCO can possibly assist Tohoku Electric Power Company. To achieve this, it is vital for us to save on electricity to the maximum extent this summer.

Shinichi Iwamoto
Professor, Faculty of Science and Engineering, Waseda University

[Profile]
Professor Iwamoto specializes in electric power system engineering, especially the operation and control of power systems.

He currently serves on the Board of Directors and chairs the Interconnection Operating Committee at the Electric Power System Council of Japan.
1971 - Graduated from Electrical Engineering Department, Faculty of Science and Engineering, Waseda University
1972 - Started his graduate study at Clarkson University, U.S.A. on scholarship
1974 - Completed his master's course at Clarkson University (obtained U.S. MS)
1975 - Completed his master's course at Graduate School of Science and Engineering, Waseda University
1978 - Completed his doctoral course at Graduate School of Science and Engineering, Waseda University (obtained PhD in engineering) Lecturer at School of Engineering, Tokai University
1982 - Associate Professor, Faculty of Science and Engineering, Waseda University
1986 - Professor, Faculty of Science and Engineering, Waseda University
1988 - Visiting professor at University of Waterloo, Canada (three months)
1992 - Visiting professor at University of Washington, U.S.A. (one year)

Professor Iwamoto has mainly been active in the Institute of Electrical Engineers of Japan (IEEJ): Chairperson, Program Committee of IEEJ in FY 1986 (Power and Energy Society); Chairperson, Editorial & Planning Affairs Committee of IEEJ in FY 1988 (Power and Energy Society); Director, Editorial Affairs of IEEJ in FY 1990; The Japanese delegate to CIGRE SC39 (power system operation and control) in 1996; Chairperson, Program Committee for the International Conference on Power Transmission and Distribution of the American Institute of Electrical Engineers in 2002; Chairman, Interconnection Operating Committee of the Electric Power System Council of Japan (neutral organization) in 2004; Member of the Sub-committee on the Wind Power Generation System Relevant Measures, New Energy Division, Agency for Natural Resources and Energy, METI in 2004; Director, Electric Power System Council of Japan in 2009.

Website of Professor Iwamoto's study team: http://www.eb.waseda.ac.jp/iwamoto/