Even with DC electrification, an air section is required at the substation border. In the city centre(Areas with many trains), air sections are located approximately every 2 to 3 km. In the Greater Tokyo Area there are about 170 air sections on JR lines alone.
The emergency signal was switched on at the level crossing in front of us, so we had to make an emergency stop. The pantographs had to be lowered to avoid a short circuit as the train was stopped in the 'air section', the junction of the wires. One pantograph, which was not in the "air section", was then raised by computer and the train escaped. The train consisted of 15 cars, 8 of which were motor cars. Only the rearmost pantograph was raised, so the motor was only running for two cars. After the escape, the train stopped again and all the pantographs were raised to resume operation. tnx comment :)