This paper describes the application of SVC (Static Var Compensator) for the AC electric railway system, outlines the SVC installed at the Shin-syo sectioning post of San-yo Shinkansen and reports the results of a verification site investigation. A single-phase SVC can reduce the voltage drop in the feeding circuit and improve the power factor at substations by compensating for the reactive power. To compensate for the voltage drop, it is more effective to locate an SVC at a sectioning post than at a substation. The site investigation has revealed that an SVC can reliably suppress voltage drop.

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The feeding transformer for AC electric railways converts three-phase electric power into a pair of single-phase electric power supplies for driving electric cars. To prevent the fluctuation of three-phase voltage, however, a single phase feeding suits car depots. Authors have developed a single-phase feeding power conditioner (SFC) for unbalanced voltage compensation. This paper describes the principle and test results of using SFC. SFC is made of a scalene Scott-connected feeding transformer and a pair of self-commutated inverters, which connect the secondary side of a transformer and are coupled with the DC side capacitor. Each inverter operates independently in order to control reactive power. On the other hand, SFC controls active power from larger to small load phase circuits via the DC capacitor to keep the active power balanced.

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The contact loss and wear of contact wire at overlap sections are larger than those in the normal areas of Shinkansen. It is important to modify overlap structures to reduce contact loss and wear of contact wire. We measured the height and wear of contact wire and acceleration produced on vibrating pantographs of a testing train at overlap sections of JYOETU Shinkansen to investigate the relationship between the height and the wear or acceleration. Furthermore we calculated current collecting characteristics of overlap sections by simulation. According to the results obtained, we can keep the wear rate of contact wire to an appropriate value by maintaining a constant height of contact wire.

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Presently, the maximum speed of Shinkansen trains reaches 300km/h. In this high-speed operation, one of the factors in estimating the quality of current collecting behavior is the stress of contact wire. There are various fittings clamped to the contact wire of overhead catenary equipment. These fittings dynamically become hard spots for pantograph collecting current. Above all, large magnitudes of contact wire stress have been marked at steady arm points. Though being under statics, in order to reveal the fundamental properties in the relation between constrain conditions of steady arms and a moving constant force, analytic calculations are carried out.

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An overhead contact line inspection system that can be installed on a rail-and-road car has been developed. It consists of a small-size contact wire wear measuring instrument and a small-size pantograph with various sensors. It can be used in the daytime at the maximum inspection speed of 30km/h, which is limited by car running stability. From the results of laboratory and field tests, it is proved that wear measurement is accurate enough for practical use.

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It has become very important to correctly grasp the contact loss between contact wire and pantograph, evaluate the current collection performance and diagnose the overhead contact line equipment of electric railroads. Although some methods have already been developed to measure contact loss, they are not practical because of the restriction, on measurement accuracy, by noise. We devised a new method to measure contact loss from feeble current changes produced between a pantograph and the ground at the moment of contact loss. The new method uses a no-current collection pantograph of inspection car used for Shinkansen AC electric railroads. In the examination by an inspection car installed with the measuring equipment, we confirmed that it was possible to obtain good response to contact loss.

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To reduce aerodynamic noise radiated from pantographs, low noise pantographs have been studied and developed in Japan. The low noise pantograph is characterized by the small number of component members with smoother forms. As the result of repeated tests, its aerodynamic noise is sufficiently lower than that of ordinary pantographs. But changing the forms of members to aerodynamically smooth shapes means to incur increased risk of receiving large aerodynamic force. The aerodynamic lift force of the panhead is particularly problematic. The authors contrived a passive lift suppression mechanism for the panhead to prevent large lift force. A prototype model of low noise pantograph named PEGASUS with this mechanism was produced. By wind tunnel and line tests, it was proved that this mechanism worked effectively.

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One of the most important subjects of overhead contact line and pantograph system is to reduce the contact loss of pantograph in high-speed operation. In this research, the relation between the wave motion of contact wire and the contact force fluctuation of pantograph is studied; the contact force fluctuation in a hanger span cycle is analyzed; and methods to reduce the contact force fluctuation are proposed. It is shown that the contact force fluctuation of pantograph in high-speed operation is mainly caused by the incident wave of contact wire that is generated by the unevenness of contact wire and is reflected at hangers. This influence becomes extremely large when the train speed is close to the wave velocity of contact wire. Increasing the wave velocity of contact wire or decreasing the reflection factor of wave motion at hangers is expected to effectively reduce the contact force fluctuation.

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To supply high-quality power to electric cars, it is required to technically study power conversion at substations, power supply to feeding circuits, current collection using contact lines and pantographs, measurement and maintenance. The power supply technology development division consists of three groups called the power supply systems group, the current collection maintenance group and the contact line structure group.
Recently, the advancement of microelectronics and power electronics led to the remarkable development of control, measurement and power converter in the field of electric railway.
This paper describes several results of the development.

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