Development of Protective Relay for Contact Fault between 50/60Hz Power Sources in AC Electric Railway

Takasaki-Nagano section, a part of Hokuriku Shinkansen was opened in October, 1997, just before Nagano Winter Olympics. Hokuriku Shinkansen has been electrified by 30kV a. c. commercial frequency AT feeding system.As for the commercial frequency, Japan is divided into two zones: the western part of Japan is a 60Hz zone and its eastern part is a 50Hz zone. Two different power frequencies exist in Hokuriku Shinkansen which passes power frequency borders between different electric power companies. Therefore, in case of a contact fault between two different power frequencies, a beat-formed large fault current will flow, which should be immediately detected and cut off.At present, a distance relay and an AC ΔI type relay are used as protective relays for a feeding circuit of Shinkansen lines. However, it was experimentally made clear that those relays do not operate by a beat-formed fault current which appears in the case of a contact fault between two different power frequencies. For this reason, we have developed and put to practical use a protective relay for a contact fault between two different frequencies, which operates by detecting 55Hz component peculiar to the current caused by the contact fault and also detecting power frequency of an opponent traction substation.They have been installed at a frequency-bordered sectioning post and at traction substations which sandwich the sectioning post.