A report submitted by Shikoku Electric Power Transmission and Distribution and Kansai Electric Power Transmission and Distribution to the Ministry of Economy, Trade and Industry on the 6th regarding the large-scale power outage that occurred in four prefectures in Shikoku in November highlights the pitfalls hidden in wide-area power cooperation. In addition to deficiencies in manuals regarding power interchange between power companies, insufficient communication between sites and human error caused by misunderstanding instructions led to the power outage.

“This was a once-in-a-decade situation. We lacked the ability to respond to unexpected operations.” Atsushi Nishida, Managing Executive Officer of Kansai Transmission and Distribution, explained this.

Honshu and Shikoku exchange electricity through two systems: the “Honshu-Shikoku Interconnection Line,” which uses the Seto Ohashi Bridge, and the “Anan-Kihoku DC Trunk Line,” which is partially laid under the seabed of the Kii Channel. The accident occurred on the Honshi-Shikoku Interconnection Line at around 2:20 p.m. on November 9th. Two control devices worked automatically: “EFC,” which matches Shikoku’s frequency to Honshu’s frequency, and “EPPS,” which transfers current from the Honshu-Shikoku interconnection.

In order to restore the Honshi-Shikoku interconnection, the Shikoku side requested the Kansai side to “suspend the Honshi-Shikoku EFC” based on the manual, meaning the suspension of the EFC and EPPS. However, the Kansai region accepted that “only EFC was suspended” and left EPPS running. As a result, the current flowing from Shikoku to Honshu rapidly increased, causing power outages.

Koji Takahata, vice president of Shikoku Transmission and Distribution, promised to “prevent recurrence.” With the liberalization of electricity, electric power companies are adjusting supply and demand not only within their jurisdictions but also across a wide area, and thorough measures are required to prevent similar situations. (Hiroto Kuwashima)

Large-scale power outage in Shikoku, discrepancies in operation recognition reported to national government, president returns compensation Shikoku, Kansai Power Transmission and Distribution