(a) (b) (c) Figure 7. The development of pantographs for the Shinkansen: (a) the diamond type (1964-2008), (b) the telescopic type (1997-2008), and (c) the single-arm low-noise type with low-noise insulators and a noise barrier. If a pantograph connected electrically with other pantographs loses contact with the contact wire, no arc occurs as long as some of other pantographs keep the contact. In other words, mechanical contact loss of only one -pantograph does not cause intense arc. In general, the Shinkansen train set is equipped with two pantographs with electrical connection today. Contact Force and Its Advantage Pa n t o g ra p h o p e ra t i o n w i t h -relatively low mean contact force has an advantage in reliability of the pantograph/catenary system. The contact wire is bent strongly by every passage of pantographs. This causes fatigue of the contact wire, and in the worst case, the contact wire will break. Giving a higher mean contact force should make it more probable that high strain occurs in the contact force. Even in the case of Shinkansen with r- elatively low mean contact force, measurement results of the contact wire strain indicate little margin for error in high-speed regions. Protection from intense strain of the -contact wire is essential for further speed-up. In March 2011, a new series of Shinkansen trains was in commercial operation with a maximum velocity of Substation 1 Changeover Section (Neutral Section) Changeover Switch Substation 2 Changeover Switch Air Section Track Circuit Automatic Power-Source Switching with 0.3-s Dead Time Figure 8. Changeover switches for Shinkansen phase separations. IEEE Elec trific ation Magazine / s ep t em be r 2 0 1 3 17