On June 6th, JR East Japan announced that the cause of the power outage that occurred on the Tokaido Shinkansen line in Shizuoka Prefecture, which resulted in a three-hour suspension of service, was damage to the power transmission cable above the stopped train. The power outage occurred on the afternoon of the 6th on the upbound line between Kakegawa Station and Shizuoka Station in Shizuoka Prefecture, halting service between Shin-Osaka and Tokyo for the upbound line and between Tokyo and Nagoya for the downbound line for approximately three hours. JR East Japan's investigation revealed that the power transmission cable located above the 12th and 13th cars of the upbound "Nozomi 12" train, which was stopped in the Shizuoka Prefecture section, had been damaged, causing a "ground fault," where electricity flows to the ground, resulting in the power outage. The power transmission cable is about 5 cm in diameter and serves to draw electricity from the pantograph and send it to each car. No abnormalities were found during a vehicle inspection on July 4th. The cause of the damage to the power transmission cable is under investigation, and JR East Japan is conducting inspections on all its vehicles to ensure there are no abnormalities with the cables.

JR East Japan also revealed that in addition to the power outage caused by the damage to the power transmission cable, a trolley wire break incident occurred on the Tokaido Shinkansen line on June 21, 2017. At that time, a trolley wire, which supplies power to trains, broke in the Kyoto-Shin-Osaka section where service had been suspended due to heavy rain, resulting in delays of 172 to 365 minutes for 63 trains in both directions, affecting 51,000 passengers. The cause of the accident was that the train had stopped in the "air section" where two trolley wires run in parallel.

On the day of the incident, service was suspended for three and a half hours due to heavy rain, and although service resumed, operating times were significantly delayed. Prior to the accident, trains were lined up on the downbound line in front of Shin-Osaka Station. The trolley wire broke at 7:48 p.m. at the location of the pantograph of the 12th car of "Nozomi 241," one of the trains lined up. At the time, JR East Japan was unaware of the broken trolley wire. At 7:53 p.m., when "Nozomi 241" began to move, the broken trolley wire came into contact with the roof of the same train, causing a ground fault and resulting in a power outage. Holes were punched in both sidewalls of the pantograph due to the ground fault current.

After that, the trolley wire either fell off the vehicle or became capable of transmitting power, and service resumed without the cause of the power outage being known. However, when the subsequent train, "Nozomi 391," arrived at the scene, the broken trolley wire came into contact with the area around the pantograph of the 5th car (one of the two pantographs on the train, the one on the Shin-Osaka side), again causing a ground fault and a power outage. Holes were similarly punched in the sidewalls.

It took five hours for staff at the scene to investigate the cause and repair the broken trolley wire. The immediate cause of the trolley wire breaking was the flow of a large current between the trolley wire and the pantograph, which generated Joule heat and an arc discharge.

These recent accidents, including the damage to the power transmission cable and the previous trolley wire break incident, have heightened concerns about safety issues during high-speed rail operations in Japan. JR East Japan needs to thoroughly inspect all power transmission cables and trolley wires on all vehicles, prioritizing safety, and strengthen measures to address potential problems during operation.