# August 2006 Tokyo blackout

On 14–15 August 2006, a major blackout had occurred in the Tokyo metropolitan area, impacting 1.39 million households and train lines in eastern Tokyo. It lasted from 7:38 to 0:54. The blackout was caused by a crane ship's boom crashing into the Koto power transmission line 78 over the Edo river, damaging electrical wires.

## Incident

On August 14, 2006, at around 7:38 am JST, a crane ship sailing near the border between Urayasu city of Chiba Prefecture and Edogawa ward in Tokyo on the Edogawa(now called Edogawa) river, crashed its boom into Koto Line 78. The power transmission overhead 275kV Koto lines No. 1 and 2 between the tower No. 79 were interrupted and disconnected, resulting in a power outage at all three substations in Katsunan, Setagaya, and Eda wards of Tokyo.
Thanks to grid switching, the Eda substation was restored at 7:46 am, but at 7:58 am, the Shinagawa Thermal Power Plant, which had been isolated from the grid, automatically shut down (due to an increase in demand in the morning due to a lack of supply capacity). Because the balance collapsed, the Koto and Jonan substations completely lost power.
At least 120,000 commuters were left stranded on underground trains, many people were trapped in elevators and more than 400 sets of traffic lights malfunctioned. The outage was also blamed for a glitch in the computer system at the Tokyo Stock Exchange that prevented it from updating the benchmark Nikkei share average.
This caused a widespread power outage to 974,000 households in the wards of Tokyo, 220,000 households in the northern part of Yokohama city and western Kawasaki city of the Kanagawa Prefecture, and 197,000 homes in parts of Urayasu City and Ichikawa City, Chiba Prefecture, for a total of approximately 1,391,000 homes.
This was the second largest number of households in Japan, after the 2.8 million households that suffered during the major power outage in the Tokyo metropolitan area in July 1987, and the fourth highest ever in terms of electricity consumption, but many of the major companies were on summer vacation. Due to this period, electricity demand was lower than usual even though it was a weekday (Monday), and at 9:55, approximately 1 hour and 17 minutes later, all but two high-voltage power stations were restored, and the remaining two The eaves were fully restored at 10:44 a.m., three hours and six minutes later. Afterwards, restoration work was carried out on the Koto Line, and power transmission was resumed on Lines 1 and 2 at 12:54 a.m. on the 17th.
The power outage caused traffic lights to stop, affecting railways, and caused a series of accidents in which people were trapped in building elevators. Even after power was temporarily restored, the power supply was still insufficient, so transportation facilities operated with reduced air-conditioning output.
Congestion occurred on mobile phones, and IP telephone service was temporarily interrupted. The Government of Japan has established an Information Liaison Office at the Crisis Management Center of the Prime Minister's Office.
Chiba Prefectural Police investigated the incident, considering charges of property damage and violations of the Electricity Business Law, but decided not to file charges in September of the same year, as the accident was not an intentional act. On September 22nd of the same year, the Yokohama Regional Marine Accident Inquiry Board applied for the commencement of a marine accident inquiry to the Yokohama Regional Marine Accident Inquiry Agency, and on March 1st, 2007, the captain of the crane ship responsible for the work was given a two-month The captain of the tugboat that was towing the crane ship was ordered to cease work for a month and a half, the crane operator was advised, and Mikuniya Construction was advised to correct its guidance.

## Cause

A crane ship owned by Mikuniya Construction sailed through the river with its boom raised and severed a major power transmission line on the former Edo River. The location of the site is near Tokyo Disney Resort.
According to investigations by Chiba Prefectural Police Urayasu Station and other sources, the 33-meter-long boom of a jib crane mounted on a crane ship (legally defined as a mobile crane) owned by Mikuniya Construction was designed to begin work immediately after arriving at the dredging site. As it was raised (raised) while being towed, it came into contact with a 275,000 volt (275 kV) power transmission line that crossed 16 meters above the water surface of the former Edogawa River, causing arcing and melting and melting.
The damaged and fused power transmission lines are the Koto Line, which connects the Shinkeiyo Substation in Funabashi City, Chiba Prefecture, the Koto Substation in Koto Ward, Tokyo, and the Eda Substation in Aoba Ward, Yokohama City. As a result of this accident, both the main line and the backup line were damaged in the 275,000-volt special high-voltage power transmission line, and approximately 974,000 households in 14 wards and 1 city of Tokyo were affected from 7:38 a.m., approximately 220,000 households in Yokohama City and Kawasaki City, Kanagawa Prefecture, and approximately 197,000 households in Urayasu City and Ichikawa City, Chiba Prefecture, for a total of approximately 1.39 million households.

## Impact
### Government structures

At 8:30 a.m., the Japanese government set up a report at the Prime Minister's Office Crisis Management Center. Chief Cabinet Secretary Shinzo Abe instructed the relevant ministries and agencies to investigate the cause, and the Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade and Industry instructed the Tokyo Electric Power Company to investigate and report on the cause and scope of the impact, in accordance with the Electricity Business Act.

### Railway

Train service was suspended for a period of time in all areas affected by the power outage, affecting the travel of approximately 345,000 people.
* JR East's Keiyo Line service was suspended for approximately 20 minutes, 10 trains on both lines were suspended, and 20 trains were delayed by up to 42 minutes, affecting approximately 19,000 people. As the company sources most of its electricity from its own power plants, the impact was minor.
* Tokyo Metro: Ginza Line, Hibiya Line, Tozai Line, and Hanzomon Line train service was suspended for up to 1 hour and 10 minutes, affecting approximately 103,000 people.
* Toei Subway: suspended on Shinjuku Line, Asakusa Line, and Mita Line.
* Yokohama Municipal Subway: suspended for approximately 10 minutes from 7:40. on Lines 1 and 3 (now the Blue Line).
* Yurikamome: suspended from the time of the power outage until 10:30. When trains stopped between stations, such as on the Rainbow Bridge, passengers were guided by staff to disembark onto the tracks and move on foot.

### Roads

Traffic lights were shut down at 440 locations in Tokyo's 23 wards and 118 locations in Chiba Prefecture. Police officers from the Metropolitan Police Department and Chiba Prefectural Police were in charge of directing traffic at intersections.

### Businesses

Due to the suspension of public transportation, many employees were late to work, and many stations and office buildings also lost power, leaving many companies and offices unable to carry out their work. However, since many businesses were on the so-called "Obon holiday" that day, the damage was less than if a power outage had occurred on a normal weekday.
Approximately 200 7-Eleven convenience stores and 30 Lawson stores were affected.

### Communications

About 300 indoor base stations installed by mobile phone companies were out of service, causing mobile phone congestion.
Nippon Broadcasting System's Kisarazu transmitting station was unable to operate due to a power outage, so the company switched to transmitting from its backup Adachi transmitting station and continued broadcasting.

### Manufacturing industry

The Oji Paper Company's plant in the Edogawa Ward, Tokyo, took about ten hours to restore operations due to the shutdown. Nisshin Steel's Ichikawa Works in Ichikawa City of the Chiba Prefecture, was also halted for a while.

### Financial institutions

Although the Tokyo Stock Exchange continued trading as normal, the Nikkei Stock Average could not be calculated. Approximately 1,000 automated ATMs in the Tokyo metropolitan area and two prefectures were temporarily suspended, and it took Seven Bank, which has ATMs in 7-Eleven stores, two and a half hours to restore operations.

### Other

The power outage caused elevators to stop working, resulting in over seventy cases of people becoming trapped inside. Tokyo Disney Resort delayed the opening of the park by about fifty minutes and temporarily suspended its attractions. Water was temporarily cut off in Chiba Prefecture, and tap water became cloudy in some areas of Tokyo. Multiple construction projects were also halted.

## Power restoration

Some power transmission was restored at 8:37 am, 59 minutes after the power outage occurred. However, there was still a continued outage due to malfunction in some power distribution equipment. Thanks to power rerouting most areas received power at 10:44 am, four hours and six minutes after the initial power outage.
The Koto power transmission line 78 was repaired at 0:54 on August 17, 2006.