IEEE Electrification Magazine - September 2013 - 13

Today, a total of 3,667 km of conventional lines are
electrified with ac 20 kV.

Technology of Japanese AC Power Supply Today

Shinkansen

Figure 4 shows a typical installation of a Japanese ac feeding circuit. Receiving power from the three-phase highvoltage, and supplied by paired single-phase circuits,
known as a center feed system are popular in Japan. In
subsations, Scott-connected traction transformers are
used for resistor grounded power grid. Also, modified
Woodbridge connected traction transformers are used to
receive the ultrahigh-voltage, directly grounded power
grid. Substations feed the contact line until sectioning
posts. The spacing of substations is 40-50 km.

Basic Configuration
AC traction showed its effectiveness, and JNR then decided
to apply ac traction for the Shinkansen project in 1958.
Shinkansen means new trunk line. In those days, the
Tokaido conventional trunk line from Tokyo to Osaka had
reached its limit of capacity. JNR specified the Shinkansen
as a system completely different from conventional lines,
with speeds faster than 200 km/h, a standard gauge, larger
clearance that enabled five seats in row, and no level crossings. The high speed and larger bodies needed high power,
and ac traction was suitable to supply the Shinkansen.
After the Tokaido Shinkansen, JNR engineers developed autotransformer (AT) supplies for commercial frequency, fed by the national ultrahigh-voltage (UHV) grid
for the success of the Shinkansen. In 1987, JNR was
divided and privatized into six passenger regional companies, one freight company, one seat reservation company, one telecommunication company, and one
research institute.
As of 2012, the Shinkansen had been extended to a
2,388-km-long network. It carries 369 million passengers
per year. In December 2010, the northern part of the
Tohoku Shinkansen from Hachinohe to Aomori was
opened. In March 2011, the Kyushu Shinkansen was fully
opened from Hakata to Yatsushiro. This connects Aomori,
the northernmost city of Honshu Island, and Kagoshima,
the southernmost city of Kyushu Island, by a 1,870.8-kmlong high-speed line.

Equipment to Suppress Harmonic Resonance
When the first commercial AT feeding was tested on
the Kagoshima line in 1969, the JNR engineers faced a
serious harmonic resonance problem. Large stray capacitance between conductors and earth on a 65-kmlong circuit was the reason. Then, the capacitors and
resistors were installed in sectioning posts to diminish
the resonance before opening the service in 1970. The
installed capacitors increased the capacitance and
lowered the peak resonance frequency. The resistors
terminated the feeding circuit to stop the reflection of
harmonics by matching the surge impedance of the
feeding circuit being between 200 and 300 Ω. Later, a
reactor was added in parallel with the resistor to
reduce Joule loss at basic frequency. Figure 5 shows the

AT Supply
The AT supply, sometimes written as 2 × 25 kV, was
invented in the United States in 1911 by Prof. Charles
F. Scott and planned for use in the Tokaido Shinkansen at
first. However, in those days, the JNR engineers could not
grasp phenomena in AT configuration with commercial
frequency. They investigated the features carefully with
computers, and after some field tests, the first AT supply
with a 10-km AT interval began revenue service in 1970 on
the Kagoshima conventional line (Figure 3). This interval
resulted from the calculations made to ensure that the AT
system's induction was equivalent to that of the booster
transformer (BT) system. AT systems provide a powerful
supply with less induced voltage. Now, AT with commercial frequency supplies most high-speed trains.
Since the Tokaido Shinkansen caused some trouble
with imbalances in the high-voltage (HV) power grid,
the later Sanyo Shinkansen used an AT system and
received power from 275-kV grids in 1972. After the
Sanyo Shinkansen and to date, a combination of an AT
system and a UHV supply has been standard for
-Shinkansen. The Tokaido Shinkansen was also updated to an AT supply between 1984 and 1991, still supplied by the HV grid.

50 Hz

Tokyo

60 Hz
ac 20 kV, 50/60 Hz
dc 1.5 kV
ac 25 kV, 50/60 Hz
Nonelectrified
Figure 2. JR electrified lines in 2013.

IEEE Elec trific ation Magazine / s ep t em be r 2 0 1 3

Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2013