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Energy-saving railway systems based on superconducting power transmission
Accepted Manuscript Energy-saving railway systems based on superconducting power transmission Masaru Tomita, Kenji Suzuki, Yusuke Fukumoto, Atsushi Ishihara, Tomoyuki Akasaka, Yusuke Kobayashi PII:
S0360-5442(17)30106-8
DOI:
10.1016/j.energy.2017.01.099
Reference:
EGY 10234
To appear in:
Energy
Received Date: 9 September 2016 Revised Date:
17 January 2017
Accepted Date: 19 January 2017
Please cite this article as: Tomita M, Suzuki K, Fukumoto Y, Ishihara A, Akasaka T, Kobayashi Y, Energy-saving railway systems based on superconducting power transmission, Energy (2017), doi: 10.1016/j.energy.2017.01.099. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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ACCEPTED Railway MANUSCRIPT Energy-Saving Systems
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based on Superconducting Power Transmission
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Masaru Tomitaa,1, Kenji Suzukib, Yusuke Fukumotob, Atsushi Ishiharab, Tomoyuki Akasakab, Yusuke
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Kobayashib
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Promotion Division, Railway Technical Research Institute;
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Applied Superconductivity Laboratory, Materials Technology Division, Railway Technical Research
Institute;
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Correspondence to [email protected]
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Abstract
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Applied Superconductivity Laboratory, Materials Technology Division and Research & Development
The new railway transmission feeder systems using superconducting materials was proposed.
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With energy issues becoming increasingly important in this century, it is important to assess the
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situation in the transportation sector. In recent years, direct current (DC) systems has been
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progressing mainly in urban areas. Developing superconducting cable for railway power transmission
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should lead to increased regeneration efficiency, reduced power loss, equalization of load between
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substations, and fewer substations due to the smaller voltage drop. In order to verify to be formed as a
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system, it’s needed to evaluate the circulation cooling, electrical current, cooling stress, laying through
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typical line and electrical test of notch operation. The superconducting feeder system was set up along ACCEPTED MANUSCRIPT
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the test track and conducted running tests, and then verified the system on a commercial line for the
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first time in the world. As the results of energy analysis, it can be 5% energy saving system on average
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rail line model. When it's converted into CO2 amount of emission, it'll be reduction in 3.6× ×105
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ton-CO2/year in the world. As railway lines continue to be built to meet the increasing demand for
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transport in line, the superconducting feeder system can be the solution to today’s electric energy
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issues.
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Keywords : high temperature superconductivity; electric train; power transmission; feeder; direct current; energy analysis
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1. Introduction
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Railway transportation is safety, convenience, economy and environmental friendliness [1]. And they make
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it increasingly important in this century for the rational and efficient use of energy [2]. A comparison of
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energy efficiency between various means of transportation shows that, in the passenger transport sector,
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railways consume only 7% of the energy despite carrying 30% of passengers. In both the passenger and
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cargo sectors, energy consumption can be greatly reduced by changing the means of transport from trucks
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and other road vehicles to railways, so it is necessary to encourage a shift from road vehicles to railways [3].
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In such a case, the entire railway transportation system should be made more energy efficient [4]. Aiming to
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energy conservation, various research are recently studied in railway [5]. And also, energy analysis in
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railway are studied for energy saving [6]. Energy saving in railway largely effects to CO2 reduction [7].
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Western countries and Japan have highly developedMANUSCRIPT rail networks (Fig. 1a). ACCEPTED
About 5% of the electricity is
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lost as it is transmitted along the rail line—a substantial loss of energy across the world’s rail networks.
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While playing a key role in the railway sector, power transmission technology must be improved to reduce
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energy losses [8].
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in the rail systems in the early 20th century and this system is still used for most electrified sections on the
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main lines. In recent years, conversion to DC systems, which require shorter insulation distances, has been
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progressing mainly in urban areas.
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capacity of several thousand amperes in the city center and several hundred amperes in the suburbs [9]. The
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overhead contact line voltage in DC electrified sections on conventional rail lines is generally 600, 1500 or
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3000V at which power losses and voltage drops start to occur when the distance between substations
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exceeds 2 to 3 km [10]. Many DC electrified sections in Japan and Europe (Fig. 1b,c) [11] suffer from
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these power loss and voltage drop issues. In US, subway also has power loss issue and France’s high-speed
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TGV trains have similar issues while running on DC electrified sections in the suburbs. Superconducting
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power transmission is needed to solve both of these issues and enhance train running stability. Accordingly,
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a project was launched to develop technologies for reducing power transmission loss by using
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superconducting cables for next-generation railway systems [12]. Fig. 2 shows flow model of electricity
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from substations to trains on railways.
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transmission lines, during which time transmission loss occurs because conventional cables have some
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resistance. And, a voltage drop occurs when the distance between substations exceeds 2 to 3 km. Then, train
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can’t accelerate because of power shortage.
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enables us to solve the problems, such as transmission loss and a voltage drop, and to increase train
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In Europe and US, low-frequency alternating current (AC) transmission was introduced
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Rail system operation using DC power transmission requires a current
Electricity generated at substations is sent to trains through power
The introduction of the superconducting feeder cable system
schedules without the number of substations [13]. On electric trains, braking generates electricity, which is ACCEPTED MANUSCRIPT
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then used by other trains; this is called regenerative braking. The electricity generated in this way by the
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motor is transmitted through the overhead contact line to other trains running nearby. However, the energy
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cannot be successfully transmitted if other trains are far away (a problem called cancelled regeneration). By
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using superconducting cables as the feeding lines, electricity can be transmitted without loss to distant trains,
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thus overcoming the problem of cancelled regeneration. The system can be made more energy efficient.
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Furthermore, electricity generated at farther substations can be sent to trains through superconducting
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cables, which makes the current load at each substation level.
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simplified and the cost of substation’s equipment can be cut.
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sent back to substations through rails and cables, in which case, leakage current corrodes underground pipes,
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such as water pipe, gas pipe and so on.
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above-mentioned problems and can effect large energy saving.
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As a result, the substation system can be
After being supplied to trains, electricity is
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Introducing the superconducting feeder system can solve the
Following the discovery of high-temperature superconducting materials (e.g. La-Ba-Cu-O is discovered in
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1986 [14]. Y-Ba-Cu-O is discovered in 1987 [15]. Bi-Sr-Ca-Cu-O is discovered in 1988 [16]),
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superconducting technology is expected to play a key role in a wide range of applications related to high
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magnetic fields [17]. And the technology is also applied for power transmission with zero electric resistance
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[18]. Using rare-earth, a high-temperature superconducting bulk material, a high magnetic field of over 17 T
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(Tesla) was attained [19], which corresponds to an extremely high current density.
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(1)
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Bz : magnetic field value, µ0 : 4µ×10-7[Wb/A m],
J : current density, h : The distance from the sample surface, d : bulk diameter, t : bulk thickness. ACCEPTED MANUSCRIPT
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These superconducting materials correspond to 1.1×106 A/cm2 in current density. However, superconducting
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material in bulk shape is strongly magnetized and so the actual current value is lower due to the
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demagnetizing effect. This demagnetizing effect can be reduced by making the superconducting material
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into a thin tape. This can be used to achieve more than 10kA DC transmission for railway transport [20]. A
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project was started to develop a superconducting DC feeder cable to solve issues typically faced on DC
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electrified sections.
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2. Methods
At first, a system was designed in which substations are partially connected with a superconducting feeder
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cable, to solve the problem of a voltage drop between substations. Electricity generated at power stations is
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sent to substations through power transmission lines as shown in Fig.3a.
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substations are partially connected with a superconducting feeder cable. Partially connecting substations
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with a superconducting feeder cable, it can effect energy-saving dependence on the superconducting cable
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length in addition to the solution for the voltage drop.
Fig.3b shows a system in which
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In order to verify to be formed as a system, it was evaluated the circulation cooling, electrical current and
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cooling stress, at first. Secondly, laying through typical line was evaluated. Thirdly, electrical test of notch
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operation was verified. Table.1 shows the developed superconducting cables and the main verification
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contents.
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The cable was built around a center core. Layers of copper tape and layers of superconducting tape were
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wrapped around the core and makeup the superconducting conductor. The superconducting tape was then
covered with a Kraft paper, which was used as anMANUSCRIPT electric insulation. Then, the wire was subsequently ACCEPTED
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covered by a core protective layer which consists of the cloth tape and Kraft paper. Finally, the wire was
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enclosed in a cryogenic pipe comprising double metallic pipes that provide vacuum insulation using
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super-insulation [20].
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The superconducting feeder system were set up along the test track on our research institute (Fig. 3c). The
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superconducting feeder cable system used in the test consisted of a superconducting feeder cable, current
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terminals which is current outlet port to feeder, a cryocooler and a circulation pump which is circulated
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refrigerant and liquid nitrogen was used as refrigerant.
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Using this superconducting feeder cable system, a train running test was conducted. And effect of saving energy was calculated on city rail line model.
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3. Results and Discussions
3.1. Verification of superconducting feeder cable system for the first time in the world
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With the system set up on the site, the following tests were conducted to verify correct system operation: a
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circulation cooling test in which the cryocooler and the circulation pump were used, and a current test by
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power supply. In the cooling test, the distribution of mechanical stress on the entire system was studied.
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When the superconducting cable is cooled, it shrinks because of thermal stress. Thermal stress was
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evaluated aiming to introduce a long superconducting cable. Fig. 4 shows the X-ray image of a
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superconducting cable before and after cooling.
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moved and contact area of the inner cable with outer pipe became large, so heat intrusion to the cable grew
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In case where the cable is fixed, the inner cable was
Therefore, if a longer cable are laid, it is required to ease the thermal stress, as is the case with the ACCEPTED MANUSCRIPT
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large.
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offset part or the winding part. In the voltage endurance test, the system withstood voltage levels similar to
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those used on existing rail lines. Following the verification test on the 31 meter cable system, a longer 310 meter superconducting feeder
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cable system was set up on the test track. These cables were laid through some typical line conditions –
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under the ground, under a viaduct and through a tight bend radius. And, take previous 31m cable cooling
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into consideration, it provide offset part because of easing the thermal stress as shown in Fig.5a. These
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verification tests showed that the superconducting feeder cable system satisfied the installation requirements
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on general commercial lines (relating to circulation cooling of liquid nitrogen, voltage endurance, cooling
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stress and routing). Using the superconducting feeder cable system, a running test was conducted with a
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two-car test train on the test track, about 600 meter long (Fig. 5b).
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Following the confirmation of running stability on the test track, the superconducting cable system was
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tested on a commercial line with a commercial train to verify the actual electrical circuit. This test was
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conducted to verify whether the superconducting cable is usable in an actual electrical circuit using a
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commercial three-car train. The system was installed on the side of the track at the railway’s stations, and
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electricity from the substations was transmitted to the train via the 6 meter superconducting cable. Fig. 5d
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shows the electrical circuit test result using commercial train. It was found that the current flows via the
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superconducting cable according to the notch operation as shown in Fig. 5d. The three-car train achieved a
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speed of about 70 km/h, the railway’s commercial speed, between four stations, 5.6 kilometer long. As the
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train gained speed, the current reading increased (up to 880 A) (Fig. 5c). Thus, the test on a superconducting
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feeder cable on a commercial rail line was successful. It was confirmed that it's formed as a electrical system
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through this verification test.
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3.2. Energy analysis of superconducting feeder cable system Fig. 6 shows a system in which substations are completely connected via a superconducting feeder cable,
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which reduced power loss, enhanced regeneration efficiency and evens out the electric load among
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substations in addition to having the benefit of Fig. 3b as shown in Table.2.
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when substations are completely connected via a superconducting feeder cable, analysis was conducted to
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quantitatively evaluate the effect of superconducting feeder cable using model in which substations were
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connected via a superconducting cable by laying it parallel to a feeder cable. The model route was 37.7 km
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long and had 19 stations and 13 substations. The 13 substations were connected via the superconducting
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feeder cable. Train intervals were set at 2 and 10 minutes and analysis was made at the 1000 seconds. A
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train interval for 10 minutes is an average train timetable in urban area and a train interval for 2 minutes is
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assumed at rush time. A simulation model was used a circuit model (Fig. 7). It was analyzed that 13
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substations - 45 trains (10-car train in urban area) organization was changed for simple equivalent circuit.
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The following energy conservation law(2,3) was used for an analysis.
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ۍ ێ ێ ۏ0
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To verify the energy effect
݈ଵ ܴ୪୧୬ୣ
⋱
ࡾ ࡵ = (ࡱ − ൣܹൗ ܫ൧)
⋮ ܫଵ ܧ ۍ ې ୗୗ ܹ ې ଵൗ ܫ ێ 0 ܫ ்ଶ ଵ )ۑ ۑ൦ ൪ = (൦ ൪ − ێ ۑ ⋮ ⋮ ۑ ێ ۑ ⋮ ܫୗେସ 0 ܴୗେ ے ۏ0 ے 0
(2)
(3)
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B Tieset matrix (closed circuit matrix), RSS Substation internal resistance [Ω], l1 The block distance [m],
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Rline Feeder resistance [Ω], Rrail Rail resistance [Ω], RSC Superconducting cable resistance [Ω], WT1 The
necessary electric power for the train [W], IT1 TrainMANUSCRIPT electric current [A] ACCEPTED
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As a result of the analysis, transmission loss reduced by introducing superconducting cable (Fig. 8a,d). And
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it was possible to send to the train away from the comeback energy, and regeneration energy efficiencies
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improved (Fig. 8b,e). While the conventional system would provide electricity to the train from the nearest
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substation, completely connected type sent electricity to the train from all of the substations, reducing the
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maximum substation current (Fig. 8c,f) and evening out the electric load among the substations. It was
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found that regeneration energy efficiencies and maximum substation current more improved for 2 minutes
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train interval. The superconducting feeder system was shown to require more cooling energy and, by
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reducing the energy, the system can be made more energy efficient. his superconducting feeder model was
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found to have a smaller Joule heat loss as electricity from the substations was sent to the trains via the
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conventional feeder line, as well as a higher regenerative ratio, saving 18.3% on 10 minutes interval, 30.2%
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on 2 minutes interval of the energy as it was possible to send regenerated energy to distant trains (Fig.9a,b).
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This 10 minutes interval is equivalent to general city transportation. And it was analyzed in urban line for
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one day average.
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minutes) (Fig. 10). By introducing superconducting transmission system, the energy saving was 28.3% for
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one day and the needed cooling energy was calculated 4% using heat intrusion and COP value which was
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resulted by previous experiment (Table.3). Based on the above, the superconducting feeder system offers the
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greatest benefit in terms of energy saving in DC electrified sections in urban areas. This is because DC
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sections have higher braking frequencies, or higher regenerative ratios, than AC sections and because the
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combined total of cancelled regeneration and Joule heat loss exceeds the cooling energy in urban routes. An
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average city railway model generally adopted the world was assumed and it was also simulated (Fig. 11,
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Table.4).
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model line. When it's assumed to have introduced a regeneration system and a superconducting feeder
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system into the line of the whole world, and the energy-saving amount is converted into CO2 amount of
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emission, it'll be equivalent to 3.6×105ton-CO2/year in the world. As next step, in order to verify the
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completely connect type, a 2000m superconducting cable will be introduced in our project started in 2016.
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A railway timetable at one day was imitated at three patterns (train interval for 10, 4.5, 2
By introducing the superconducting system, the energy saving was 5.0% for one day on this
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4. Conclusion
A superconducting feeder cable system was developed with the aim of saving energy in the global rail
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transport system. It was confirmed that it's formed as a system through the verification test. As the results of
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energy analysis, it was found that the benefits of introducing the superconducting feeder system include
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higher regeneration efficiency, reduced power loss, equalization of load between substations, and it can be
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5% energy saving system on city rail line model. Table.5 shows the current and next tests. As future's
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schedule, the superconducting feeder cable is introduced into commercial lines of Tokyo metropolitan in
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2018, and it works. Then, a superconducting cable of 2000m in length will be introduced in 2021 in a project
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which is supported by New Energy and Industrial Technology Development Organization. As railway lines
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continue to be built to meet the increasing demand for transport in line with the world’s growing population,
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the superconducting feeder system can be the solution to today’s electric energy issues.
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Acknowledgement
This work was funded by the Ministry of Land, Infrastructure, Transport and Tourism and the Japan
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Science and Technology Agency, Strategic Promotion of Innovative Research and Development
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(S-Innovation).
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We thank H. Ohsaki, T. Kiss, S. Fuchino, T. Masuda, N. Tamada, H. Kitaguchi, J. Shimoyama, N.
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Amemiya, S. Hata, T. Tamegai for technical support in S-Innovation project. We thank also IZUHAKONE
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Railway Co., Ltd., East Japan Railway Company, West Japan Railway Company, Tokyo Metro Co., Ltd.,
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Bureau of Transportation Tokyo Metropolitan Government, Tokyu Corporation, Hankyu Corporation and
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SNCF for railways technical supports, T. Nishihara, A. Maeda, H. Shigeeda, T. Konishi and G. Morita for
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experiments support.
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Author Contributions
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M. T. conceived the study and supervised. K. S., Y.MANUSCRIPT F., A. I., T. A., Y. K. and performed experiments and ACCEPTED
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analysis.
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Additional Information
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The authors declare no competing financial interests.
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Rail lines in the world and Rail electrification systems in Japan and European
countries.
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Figure 1
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a, The red lines represent existing rail lines in the world.
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developed rail lines.
b, Rail electrification systems in Japan. systems are more popular in local areas.
Western countries and Japan have highly
DC systems are more widely used in city areas while AC c, Rail electrification systems in European countries.
Some European countries prefer DC systems while others favor AC systems. 267
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Figure 2
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Flow model of electricity from substations to trains on railways.
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Electricity generated at substations is sent to trains through power transmission lines.
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Figure 3 a,
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Method of verifying superconducting feeder cable system.
Flow model of electricity from power stations to trains on railways.
And then, electricity is sent
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power stations is sent to substations through power transmission lines.
Electricity generated at
from substation to trains through superconducting feeder cable. A system in which substations are partially connected with a superconducting feeder
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cable.(Partially type)
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Partially connecting with a superconducting feeder cable, it can effect energy-saving dependence on the superconducting cable length in addition to the solution for the voltage drop. c,
Superconducting feeder cable system set up along the test track on the premises of the Railway
Technical Research Institute. 270
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Verifying contents of superconducting feeder system by train running test
Rail line
Content
Cable
Test track
31m
6960 A
310m
1110 A
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Circulation cooling, Current, Cooling stress
2080 A
Laying through typical line and verification (circulation cooling, current after laying)
Commercial line
Electrical test of notch operation
6m
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Current capacity
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Table. 1
Figure 4 cooling.
The X-ray image of 31m superconducting cable before and after
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Figure 5
Verification of superconducting feeder cable system
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a,
View of offset part on 310m superconducting feeder cable.
b,
The running test using the 310m superconducting feeder cable system on the test
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track. 285
c,
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Train running test using superconducting feeder cable system set up at Ohito Station
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on the Izuhakone Railway Sunzu Line. 287
Commercial train running data which is current value through the cable and train
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speed.
Figure 6
Introduction models of superconducting feeder cable for railways.(Completely
type) A system in which substations are completely connected via a superconducting feeder cable.
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Table.2
Effects of Introducing superconducting feeder cable for railways.
A system in which substations are partially and completely connected via a superconducting feeder cable.
Regeneration energy
○* ○
Solution of voltage drop (increase train schedules, fewer substations)
◎
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Load leveling substations
△*
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b Distance / km
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40 35 30 25 20 15 10 5 0 0
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Analysis model and train timetable of superconducting cables on railways.
a, Electrical circuit model of superconducting cables on railways.
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Solution of feeder energy loss
*Depending on superconducting cable length
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Completely type
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Partially type
Issue
b, Model of train timetable .
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Energy analysis results for introduction effects of railway transmission system
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a(d), A line impedance loss with/without superconducting feeder cable model in urban area (a : train interval for 10 minutes, d : train interval for 2 minutes).
b(e), A regeneration energy with/without
superconducting feeder cable model in urban area (b : train interval
for 10 minutes, e : train interval for 2
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minutes) c(f), A max substation current with/without superconducting feeder cable model in urban area (c : train interval for 10 minutes, f : train interval for 2 minutes).
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Figure 9
Energy analysis results for superconducting feeder cable model in urban area (a : train
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Time / hour 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0
4.5 minutes interval
Train： 45-trains
2 minutes interval
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Train： 20-trains
Railway simulation model for 2, 4.5, 10 minutes train interval in urban area.
Energy analysis for introduction effects of railway transmission system for one day.
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Table. 3
10 minutes interval
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Figure 10
Train： 9-trains
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Train： none
Total energy [kW]
Substation output
15130
49%
1314
4%
14328
47%
Conventional system
22939
77%
－
－
6681
23%
Superconducting system
－
－
1314
100 %
－
－
Conventional system
－
－
－
－
－
－
Superconducting system
6052
44%
1314
10%
6292
46%
Conventional system
9014
73%
－
－
3294
27%
Superconducting system
14751
50%
1314
4%
13904
46%
Conventional system
22801
81%
－
－
5504
19%
Superconducting system
33586
50%
1314
2%
31628
48%
Conventional system
49977
75%
－
－
16883
25%
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No train
Train interval for 10 minutes
Train interval for 4.5 minutes
Train interval for 2 minutes
297
Regeneration energy[kW]
Superconducting system
EP
1day average
Cooling energy
Energy saving
28.3%
18.3%
29.5%
30.2%
1
2
3
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ACCEPTED MANUSCRIPT
4
21 22 23
8 minutes interval
Train： 21-trains
5 minutes interval
Train： 34-trains
3 minutes interval
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Figure 11
Train： 13-trains
Railway simulation model assumed an average city railway model generally adopted
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the world .
Table. 4
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Train： none
Energy analysis for introduction effects of railway transmission system for one day on an
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average city railway model generally adopted the world. Total energy [kW]
Substation output
9080
64%
1238
9%
3909
27%
Conventional system
10856
80%
－
－
2657
20%
Superconducting system
－
－
1238
100%
－
－
Conventional system
－
－
－
－
－
－
Superconducting system
10385
69%
1238
8%
3560
23%
Conventional system
12472
86%
－
－
2110
14%
Superconducting system
13859
60%
1238
5%
8075
35%
Conventional system
16440
73%
－
－
6037
27%
Superconducting system
20561
54%
1238
3%
16183
43%
Conventional system
24129
63%
－
－
14019
37%
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No train
Train interval for 8 minutes
Train interval for 5 minutes
Train interval For 3 minutes
298
Regeneration energy[kW]
Superconducting system
EP
1day average
Cooling energy
Energy saving
5.0%
6.8%
8.2%
9.7%
ACCEPTED MANUSCRIPT Schedules of superconducting feeder system verification
Rail line
Current value on train running test
Current capacity
Cable
Test track
250 A
6960 A
31m
Test track
260 A
1110 A
310m
Connection type between substations
Year 2013 2014
Partially
Commercial line Commercial line
880 A
2080 A
6m
(1000-1500 A)
(8100 A)
410m
Test track or commercial line
-
(4000-8000 A) 2000m Completely
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( ) Designed
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2015
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Table. 5
2018
2021
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Content
Cable
Circulation cooling, Current,
Test track
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Cooling stress
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Rail line
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Table.1Verifying contents of superconducting feeder system by train running test
Current
capacity
31m
6960 A
310m
1110 A
6m
2080 A
Laying through typical line and verification
(circulation cooling, current after laying)
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Electrical test of notch operation
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Commercial line
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Table.2 Effects of Introducing superconducting feeder cable for railways.
Partially
Issue
Completely type
type *
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Regeneration energy
Solution of voltage drop (increase train schedules, fewer substations) *
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*Depending on superconducting cable length
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Load leveling substations
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Solution of feeder energy loss
ACCEPTED MANUSCRIPT Total energy [kW] Substation
Cooling
output
energy
Superconducting system
15130
49%
Conventional system
22939
77%
1314
Regeneration energy[kW]
4%
14328
47%
6681
23%
28.3%
Superconducting system
1314
100%
1314
10%
No train
for 4.5 minutes
Train interval for 2 minutes
44%
Conventional system
9014
73%
Superconducting system
14751
50%
Conventional system
22801
81%
Superconducting system
33586
50%
Conventional system
49977
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Train interval
6052
1314
1314
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for 10 minutes
Superconducting system
75%
EP
Train interval
Table. 3 Energy analysis for introduction effects of railway transmission system for one day.
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Conventional system
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1day average
Energy saving
4%
2%
6292
46% 18.3%
3294
27%
13904
46% 29.5%
5504
19%
31628
48% 30.2%
16883
25%
ACCEPTED MANUSCRIPT Total energy [kW]
Regeneration energy[kW] Substation
Cooling
output
Energy 64%
Conventional system
10856
80%
1238
1day average
Superconducting system
1238
Conventional system
for 5 minutes Train interval For 3 minutes
69%
Conventional system
12472
86%
Superconducting system
13859
60%
Conventional system
16440
Superconducting system
20561
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Train interval
10385
1238
1238
8%
5%
54%
27%
2657
20%
3560
23% 6.8%
2110
14%
8075
35%
6037
27%
1238
3%
16183
43%
Table. 4 Energy analysis for introduction effects of railway transmission system for one day on an average city railway model generally adopted the world.
5.0%
8.2%
73%
EP
for 8 minutes
Superconducting system
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Train interval
3909
100%
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No train
9%
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9080
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Superconducting system
Energy saving
9.7%
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Schedules of superconducting feeder system verification
Connection
Current value on train
running Current capacity
Cable
test
type between substations
250 A
6960 A
31m
Test track
260 A
1110 A
310m
Commercial line
880 A
2080 A
6m
Commercial line
(1000-1500 A)
(8100 A)
410m
-
(4000-8000 A)
2013
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Test track
Year
SC
Rail line
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Table. 5
2014
commercial line ( ) Designed
or
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track
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Test
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Partially
2000m
2015 2017 ~2018
Completely
2021
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Highlights Proposed new railway transmission feeder systems using superconducting
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materials
Advantages of high regeneration energy, reduce power loss, solution of
SC
voltage drop
Laid the system, conducted train running tests and verified on commercial
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line
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EP
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Result of analysis, 5% energy saving system on city rail line model
S0360-5442(17)30106-8
DOI:
10.1016/j.energy.2017.01.099
Reference:
EGY 10234
To appear in:
Energy
Received Date: 9 September 2016 Revised Date:
17 January 2017
Accepted Date: 19 January 2017
Please cite this article as: Tomita M, Suzuki K, Fukumoto Y, Ishihara A, Akasaka T, Kobayashi Y, Energy-saving railway systems based on superconducting power transmission, Energy (2017), doi: 10.1016/j.energy.2017.01.099. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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ACCEPTED Railway MANUSCRIPT Energy-Saving Systems
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based on Superconducting Power Transmission
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Masaru Tomitaa,1, Kenji Suzukib, Yusuke Fukumotob, Atsushi Ishiharab, Tomoyuki Akasakab, Yusuke
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Kobayashib
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a
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Promotion Division, Railway Technical Research Institute;
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b
Applied Superconductivity Laboratory, Materials Technology Division, Railway Technical Research
Institute;
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Correspondence to [email protected]
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Abstract
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Applied Superconductivity Laboratory, Materials Technology Division and Research & Development
The new railway transmission feeder systems using superconducting materials was proposed.
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With energy issues becoming increasingly important in this century, it is important to assess the
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situation in the transportation sector. In recent years, direct current (DC) systems has been
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progressing mainly in urban areas. Developing superconducting cable for railway power transmission
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should lead to increased regeneration efficiency, reduced power loss, equalization of load between
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substations, and fewer substations due to the smaller voltage drop. In order to verify to be formed as a
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system, it’s needed to evaluate the circulation cooling, electrical current, cooling stress, laying through
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typical line and electrical test of notch operation. The superconducting feeder system was set up along ACCEPTED MANUSCRIPT
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the test track and conducted running tests, and then verified the system on a commercial line for the
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first time in the world. As the results of energy analysis, it can be 5% energy saving system on average
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rail line model. When it's converted into CO2 amount of emission, it'll be reduction in 3.6× ×105
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ton-CO2/year in the world. As railway lines continue to be built to meet the increasing demand for
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transport in line, the superconducting feeder system can be the solution to today’s electric energy
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issues.
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Keywords : high temperature superconductivity; electric train; power transmission; feeder; direct current; energy analysis
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1. Introduction
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Railway transportation is safety, convenience, economy and environmental friendliness [1]. And they make
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it increasingly important in this century for the rational and efficient use of energy [2]. A comparison of
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energy efficiency between various means of transportation shows that, in the passenger transport sector,
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railways consume only 7% of the energy despite carrying 30% of passengers. In both the passenger and
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cargo sectors, energy consumption can be greatly reduced by changing the means of transport from trucks
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and other road vehicles to railways, so it is necessary to encourage a shift from road vehicles to railways [3].
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In such a case, the entire railway transportation system should be made more energy efficient [4]. Aiming to
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energy conservation, various research are recently studied in railway [5]. And also, energy analysis in
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railway are studied for energy saving [6]. Energy saving in railway largely effects to CO2 reduction [7].
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Western countries and Japan have highly developedMANUSCRIPT rail networks (Fig. 1a). ACCEPTED
About 5% of the electricity is
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lost as it is transmitted along the rail line—a substantial loss of energy across the world’s rail networks.
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While playing a key role in the railway sector, power transmission technology must be improved to reduce
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energy losses [8].
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in the rail systems in the early 20th century and this system is still used for most electrified sections on the
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main lines. In recent years, conversion to DC systems, which require shorter insulation distances, has been
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progressing mainly in urban areas.
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capacity of several thousand amperes in the city center and several hundred amperes in the suburbs [9]. The
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overhead contact line voltage in DC electrified sections on conventional rail lines is generally 600, 1500 or
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3000V at which power losses and voltage drops start to occur when the distance between substations
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exceeds 2 to 3 km [10]. Many DC electrified sections in Japan and Europe (Fig. 1b,c) [11] suffer from
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these power loss and voltage drop issues. In US, subway also has power loss issue and France’s high-speed
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TGV trains have similar issues while running on DC electrified sections in the suburbs. Superconducting
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power transmission is needed to solve both of these issues and enhance train running stability. Accordingly,
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a project was launched to develop technologies for reducing power transmission loss by using
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superconducting cables for next-generation railway systems [12]. Fig. 2 shows flow model of electricity
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from substations to trains on railways.
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transmission lines, during which time transmission loss occurs because conventional cables have some
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resistance. And, a voltage drop occurs when the distance between substations exceeds 2 to 3 km. Then, train
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can’t accelerate because of power shortage.
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enables us to solve the problems, such as transmission loss and a voltage drop, and to increase train
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In Europe and US, low-frequency alternating current (AC) transmission was introduced
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Rail system operation using DC power transmission requires a current
Electricity generated at substations is sent to trains through power
The introduction of the superconducting feeder cable system
schedules without the number of substations [13]. On electric trains, braking generates electricity, which is ACCEPTED MANUSCRIPT
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then used by other trains; this is called regenerative braking. The electricity generated in this way by the
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motor is transmitted through the overhead contact line to other trains running nearby. However, the energy
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cannot be successfully transmitted if other trains are far away (a problem called cancelled regeneration). By
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using superconducting cables as the feeding lines, electricity can be transmitted without loss to distant trains,
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thus overcoming the problem of cancelled regeneration. The system can be made more energy efficient.
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Furthermore, electricity generated at farther substations can be sent to trains through superconducting
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cables, which makes the current load at each substation level.
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simplified and the cost of substation’s equipment can be cut.
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sent back to substations through rails and cables, in which case, leakage current corrodes underground pipes,
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such as water pipe, gas pipe and so on.
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above-mentioned problems and can effect large energy saving.
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As a result, the substation system can be
After being supplied to trains, electricity is
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Introducing the superconducting feeder system can solve the
Following the discovery of high-temperature superconducting materials (e.g. La-Ba-Cu-O is discovered in
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1986 [14]. Y-Ba-Cu-O is discovered in 1987 [15]. Bi-Sr-Ca-Cu-O is discovered in 1988 [16]),
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superconducting technology is expected to play a key role in a wide range of applications related to high
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magnetic fields [17]. And the technology is also applied for power transmission with zero electric resistance
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[18]. Using rare-earth, a high-temperature superconducting bulk material, a high magnetic field of over 17 T
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(Tesla) was attained [19], which corresponds to an extremely high current density.
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(1)
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Bz : magnetic field value, µ0 : 4µ×10-7[Wb/A m],
J : current density, h : The distance from the sample surface, d : bulk diameter, t : bulk thickness. ACCEPTED MANUSCRIPT
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These superconducting materials correspond to 1.1×106 A/cm2 in current density. However, superconducting
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material in bulk shape is strongly magnetized and so the actual current value is lower due to the
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demagnetizing effect. This demagnetizing effect can be reduced by making the superconducting material
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into a thin tape. This can be used to achieve more than 10kA DC transmission for railway transport [20]. A
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project was started to develop a superconducting DC feeder cable to solve issues typically faced on DC
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electrified sections.
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2. Methods
At first, a system was designed in which substations are partially connected with a superconducting feeder
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cable, to solve the problem of a voltage drop between substations. Electricity generated at power stations is
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sent to substations through power transmission lines as shown in Fig.3a.
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substations are partially connected with a superconducting feeder cable. Partially connecting substations
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with a superconducting feeder cable, it can effect energy-saving dependence on the superconducting cable
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length in addition to the solution for the voltage drop.
Fig.3b shows a system in which
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In order to verify to be formed as a system, it was evaluated the circulation cooling, electrical current and
100
cooling stress, at first. Secondly, laying through typical line was evaluated. Thirdly, electrical test of notch
101
operation was verified. Table.1 shows the developed superconducting cables and the main verification
102
contents.
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The cable was built around a center core. Layers of copper tape and layers of superconducting tape were
104
wrapped around the core and makeup the superconducting conductor. The superconducting tape was then
covered with a Kraft paper, which was used as anMANUSCRIPT electric insulation. Then, the wire was subsequently ACCEPTED
106
covered by a core protective layer which consists of the cloth tape and Kraft paper. Finally, the wire was
107
enclosed in a cryogenic pipe comprising double metallic pipes that provide vacuum insulation using
108
super-insulation [20].
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The superconducting feeder system were set up along the test track on our research institute (Fig. 3c). The
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superconducting feeder cable system used in the test consisted of a superconducting feeder cable, current
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terminals which is current outlet port to feeder, a cryocooler and a circulation pump which is circulated
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refrigerant and liquid nitrogen was used as refrigerant.
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Using this superconducting feeder cable system, a train running test was conducted. And effect of saving energy was calculated on city rail line model.
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3. Results and Discussions
3.1. Verification of superconducting feeder cable system for the first time in the world
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With the system set up on the site, the following tests were conducted to verify correct system operation: a
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circulation cooling test in which the cryocooler and the circulation pump were used, and a current test by
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power supply. In the cooling test, the distribution of mechanical stress on the entire system was studied.
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When the superconducting cable is cooled, it shrinks because of thermal stress. Thermal stress was
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evaluated aiming to introduce a long superconducting cable. Fig. 4 shows the X-ray image of a
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superconducting cable before and after cooling.
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moved and contact area of the inner cable with outer pipe became large, so heat intrusion to the cable grew
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In case where the cable is fixed, the inner cable was
Therefore, if a longer cable are laid, it is required to ease the thermal stress, as is the case with the ACCEPTED MANUSCRIPT
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large.
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offset part or the winding part. In the voltage endurance test, the system withstood voltage levels similar to
128
those used on existing rail lines. Following the verification test on the 31 meter cable system, a longer 310 meter superconducting feeder
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cable system was set up on the test track. These cables were laid through some typical line conditions –
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under the ground, under a viaduct and through a tight bend radius. And, take previous 31m cable cooling
132
into consideration, it provide offset part because of easing the thermal stress as shown in Fig.5a. These
133
verification tests showed that the superconducting feeder cable system satisfied the installation requirements
134
on general commercial lines (relating to circulation cooling of liquid nitrogen, voltage endurance, cooling
135
stress and routing). Using the superconducting feeder cable system, a running test was conducted with a
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two-car test train on the test track, about 600 meter long (Fig. 5b).
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Following the confirmation of running stability on the test track, the superconducting cable system was
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tested on a commercial line with a commercial train to verify the actual electrical circuit. This test was
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conducted to verify whether the superconducting cable is usable in an actual electrical circuit using a
140
commercial three-car train. The system was installed on the side of the track at the railway’s stations, and
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electricity from the substations was transmitted to the train via the 6 meter superconducting cable. Fig. 5d
142
shows the electrical circuit test result using commercial train. It was found that the current flows via the
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superconducting cable according to the notch operation as shown in Fig. 5d. The three-car train achieved a
144
speed of about 70 km/h, the railway’s commercial speed, between four stations, 5.6 kilometer long. As the
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train gained speed, the current reading increased (up to 880 A) (Fig. 5c). Thus, the test on a superconducting
146
feeder cable on a commercial rail line was successful. It was confirmed that it's formed as a electrical system
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through this verification test.
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3.2. Energy analysis of superconducting feeder cable system Fig. 6 shows a system in which substations are completely connected via a superconducting feeder cable,
151
which reduced power loss, enhanced regeneration efficiency and evens out the electric load among
152
substations in addition to having the benefit of Fig. 3b as shown in Table.2.
153
when substations are completely connected via a superconducting feeder cable, analysis was conducted to
154
quantitatively evaluate the effect of superconducting feeder cable using model in which substations were
155
connected via a superconducting cable by laying it parallel to a feeder cable. The model route was 37.7 km
156
long and had 19 stations and 13 substations. The 13 substations were connected via the superconducting
157
feeder cable. Train intervals were set at 2 and 10 minutes and analysis was made at the 1000 seconds. A
158
train interval for 10 minutes is an average train timetable in urban area and a train interval for 2 minutes is
159
assumed at rush time. A simulation model was used a circuit model (Fig. 7). It was analyzed that 13
160
substations - 45 trains (10-car train in urban area) organization was changed for simple equivalent circuit.
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The following energy conservation law(2,3) was used for an analysis.
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ܴୗୗ
ۍ ێ ێ ۏ0
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To verify the energy effect
݈ଵ ܴ୪୧୬ୣ
⋱
ࡾ ࡵ = (ࡱ − ൣܹൗ ܫ൧)
⋮ ܫଵ ܧ ۍ ې ୗୗ ܹ ې ଵൗ ܫ ێ 0 ܫ ்ଶ ଵ )ۑ ۑ൦ ൪ = (൦ ൪ − ێ ۑ ⋮ ⋮ ۑ ێ ۑ ⋮ ܫୗେସ 0 ܴୗେ ے ۏ0 ے 0
(2)
(3)
165
B Tieset matrix (closed circuit matrix), RSS Substation internal resistance [Ω], l1 The block distance [m],
166
Rline Feeder resistance [Ω], Rrail Rail resistance [Ω], RSC Superconducting cable resistance [Ω], WT1 The
necessary electric power for the train [W], IT1 TrainMANUSCRIPT electric current [A] ACCEPTED
168
As a result of the analysis, transmission loss reduced by introducing superconducting cable (Fig. 8a,d). And
169
it was possible to send to the train away from the comeback energy, and regeneration energy efficiencies
170
improved (Fig. 8b,e). While the conventional system would provide electricity to the train from the nearest
171
substation, completely connected type sent electricity to the train from all of the substations, reducing the
172
maximum substation current (Fig. 8c,f) and evening out the electric load among the substations. It was
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found that regeneration energy efficiencies and maximum substation current more improved for 2 minutes
174
train interval. The superconducting feeder system was shown to require more cooling energy and, by
175
reducing the energy, the system can be made more energy efficient. his superconducting feeder model was
176
found to have a smaller Joule heat loss as electricity from the substations was sent to the trains via the
177
conventional feeder line, as well as a higher regenerative ratio, saving 18.3% on 10 minutes interval, 30.2%
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on 2 minutes interval of the energy as it was possible to send regenerated energy to distant trains (Fig.9a,b).
179
This 10 minutes interval is equivalent to general city transportation. And it was analyzed in urban line for
180
one day average.
181
minutes) (Fig. 10). By introducing superconducting transmission system, the energy saving was 28.3% for
182
one day and the needed cooling energy was calculated 4% using heat intrusion and COP value which was
183
resulted by previous experiment (Table.3). Based on the above, the superconducting feeder system offers the
184
greatest benefit in terms of energy saving in DC electrified sections in urban areas. This is because DC
185
sections have higher braking frequencies, or higher regenerative ratios, than AC sections and because the
186
combined total of cancelled regeneration and Joule heat loss exceeds the cooling energy in urban routes. An
187
average city railway model generally adopted the world was assumed and it was also simulated (Fig. 11,
188
Table.4).
189
model line. When it's assumed to have introduced a regeneration system and a superconducting feeder
190
system into the line of the whole world, and the energy-saving amount is converted into CO2 amount of
191
emission, it'll be equivalent to 3.6×105ton-CO2/year in the world. As next step, in order to verify the
192
completely connect type, a 2000m superconducting cable will be introduced in our project started in 2016.
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A railway timetable at one day was imitated at three patterns (train interval for 10, 4.5, 2
By introducing the superconducting system, the energy saving was 5.0% for one day on this
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4. Conclusion
A superconducting feeder cable system was developed with the aim of saving energy in the global rail
196
transport system. It was confirmed that it's formed as a system through the verification test. As the results of
197
energy analysis, it was found that the benefits of introducing the superconducting feeder system include
198
higher regeneration efficiency, reduced power loss, equalization of load between substations, and it can be
199
5% energy saving system on city rail line model. Table.5 shows the current and next tests. As future's
200
schedule, the superconducting feeder cable is introduced into commercial lines of Tokyo metropolitan in
201
2018, and it works. Then, a superconducting cable of 2000m in length will be introduced in 2021 in a project
202
which is supported by New Energy and Industrial Technology Development Organization. As railway lines
203
continue to be built to meet the increasing demand for transport in line with the world’s growing population,
204
the superconducting feeder system can be the solution to today’s electric energy issues.
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Review. 27, 16-24 (2001).
208
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R. Smith, Railway technology -The last 50 years and future prospect. Japan Railway & Transport
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R. C. Pietzcker et al., Long-term transport energy demand and climate policy: Alternative visions on transport decarbonization in energy-economy models. Energy 64, 95-108 (2014).
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3.
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(2008)107-116.
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B, Mathiesen et al.,
Integrated transport and renewable energy systems. Util Policy. 16
W. Gunselmann, Technologies for increased energy efficiency in railway systems. Power Electronics and Applications, 2005 European Conference on. 10 (2005).
X. Feng, B. Mao, X. Feng, J. Feng, Study on theMANUSCRIPT maximum operation speeds of metro trains for energy ACCEPTED
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saving as well as transport efficiency improvement. Energy 36, 6577-6582 (2011).
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fields of over 17 tesla at 29 K. Nature 421, 517-520 (2003).
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Acknowledgement
This work was funded by the Ministry of Land, Infrastructure, Transport and Tourism and the Japan
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Science and Technology Agency, Strategic Promotion of Innovative Research and Development
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(S-Innovation).
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We thank H. Ohsaki, T. Kiss, S. Fuchino, T. Masuda, N. Tamada, H. Kitaguchi, J. Shimoyama, N.
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Amemiya, S. Hata, T. Tamegai for technical support in S-Innovation project. We thank also IZUHAKONE
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Railway Co., Ltd., East Japan Railway Company, West Japan Railway Company, Tokyo Metro Co., Ltd.,
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Bureau of Transportation Tokyo Metropolitan Government, Tokyu Corporation, Hankyu Corporation and
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SNCF for railways technical supports, T. Nishihara, A. Maeda, H. Shigeeda, T. Konishi and G. Morita for
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experiments support.
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Author Contributions
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M. T. conceived the study and supervised. K. S., Y.MANUSCRIPT F., A. I., T. A., Y. K. and performed experiments and ACCEPTED
259
analysis.
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Additional Information
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The authors declare no competing financial interests.
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ACCEPTED MANUSCRIPT
Rail lines in the world and Rail electrification systems in Japan and European
countries.
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Figure 1
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a, The red lines represent existing rail lines in the world.
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developed rail lines.
b, Rail electrification systems in Japan. systems are more popular in local areas.
Western countries and Japan have highly
DC systems are more widely used in city areas while AC c, Rail electrification systems in European countries.
Some European countries prefer DC systems while others favor AC systems. 267
268
Figure 2
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Flow model of electricity from substations to trains on railways.
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Electricity generated at substations is sent to trains through power transmission lines.
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Figure 3 a,
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Method of verifying superconducting feeder cable system.
Flow model of electricity from power stations to trains on railways.
And then, electricity is sent
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power stations is sent to substations through power transmission lines.
Electricity generated at
from substation to trains through superconducting feeder cable. A system in which substations are partially connected with a superconducting feeder
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cable.(Partially type)
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b,
Partially connecting with a superconducting feeder cable, it can effect energy-saving dependence on the superconducting cable length in addition to the solution for the voltage drop. c,
Superconducting feeder cable system set up along the test track on the premises of the Railway
Technical Research Institute. 270
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271
Verifying contents of superconducting feeder system by train running test
Rail line
Content
Cable
Test track
31m
6960 A
310m
1110 A
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Circulation cooling, Current, Cooling stress
2080 A
Laying through typical line and verification (circulation cooling, current after laying)
Commercial line
Electrical test of notch operation
6m
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Current capacity
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Table. 1
Figure 4 cooling.
The X-ray image of 31m superconducting cable before and after
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Figure 5
Verification of superconducting feeder cable system
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a,
View of offset part on 310m superconducting feeder cable.
b,
The running test using the 310m superconducting feeder cable system on the test
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track. 285
c,
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Train running test using superconducting feeder cable system set up at Ohito Station
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286
on the Izuhakone Railway Sunzu Line. 287
Commercial train running data which is current value through the cable and train
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d,
speed.
Figure 6
Introduction models of superconducting feeder cable for railways.(Completely
type) A system in which substations are completely connected via a superconducting feeder cable.
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288
Table.2
Effects of Introducing superconducting feeder cable for railways.
A system in which substations are partially and completely connected via a superconducting feeder cable.
Regeneration energy
○* ○
Solution of voltage drop (increase train schedules, fewer substations)
◎
◎
Load leveling substations
△*
◎
SS
SS
SS
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SS
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Figure 7
b Distance / km
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40 35 30 25 20 15 10 5 0 0
200
400 600 Time / s
Analysis model and train timetable of superconducting cables on railways.
a, Electrical circuit model of superconducting cables on railways.
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○
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◎
Solution of feeder energy loss
*Depending on superconducting cable length
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Completely type
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Partially type
Issue
b, Model of train timetable .
800
1000
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Energy analysis results for introduction effects of railway transmission system
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Figure 8
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a(d), A line impedance loss with/without superconducting feeder cable model in urban area (a : train interval for 10 minutes, d : train interval for 2 minutes).
b(e), A regeneration energy with/without
superconducting feeder cable model in urban area (b : train interval
for 10 minutes, e : train interval for 2
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minutes) c(f), A max substation current with/without superconducting feeder cable model in urban area (c : train interval for 10 minutes, f : train interval for 2 minutes).
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Figure 9
Energy analysis results for superconducting feeder cable model in urban area (a : train
interval for 10 minutes, b : train interval for 2 minutes). 295
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Time / hour 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0
4.5 minutes interval
Train： 45-trains
2 minutes interval
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Train： 20-trains
Railway simulation model for 2, 4.5, 10 minutes train interval in urban area.
Energy analysis for introduction effects of railway transmission system for one day.
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Table. 3
10 minutes interval
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Figure 10
Train： 9-trains
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Train： none
Total energy [kW]
Substation output
15130
49%
1314
4%
14328
47%
Conventional system
22939
77%
－
－
6681
23%
Superconducting system
－
－
1314
100 %
－
－
Conventional system
－
－
－
－
－
－
Superconducting system
6052
44%
1314
10%
6292
46%
Conventional system
9014
73%
－
－
3294
27%
Superconducting system
14751
50%
1314
4%
13904
46%
Conventional system
22801
81%
－
－
5504
19%
Superconducting system
33586
50%
1314
2%
31628
48%
Conventional system
49977
75%
－
－
16883
25%
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No train
Train interval for 10 minutes
Train interval for 4.5 minutes
Train interval for 2 minutes
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Regeneration energy[kW]
Superconducting system
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1day average
Cooling energy
Energy saving
28.3%
18.3%
29.5%
30.2%
1
2
3
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ACCEPTED MANUSCRIPT
4
21 22 23
8 minutes interval
Train： 21-trains
5 minutes interval
Train： 34-trains
3 minutes interval
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Figure 11
Train： 13-trains
Railway simulation model assumed an average city railway model generally adopted
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the world .
Table. 4
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Train： none
Energy analysis for introduction effects of railway transmission system for one day on an
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average city railway model generally adopted the world. Total energy [kW]
Substation output
9080
64%
1238
9%
3909
27%
Conventional system
10856
80%
－
－
2657
20%
Superconducting system
－
－
1238
100%
－
－
Conventional system
－
－
－
－
－
－
Superconducting system
10385
69%
1238
8%
3560
23%
Conventional system
12472
86%
－
－
2110
14%
Superconducting system
13859
60%
1238
5%
8075
35%
Conventional system
16440
73%
－
－
6037
27%
Superconducting system
20561
54%
1238
3%
16183
43%
Conventional system
24129
63%
－
－
14019
37%
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No train
Train interval for 8 minutes
Train interval for 5 minutes
Train interval For 3 minutes
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Regeneration energy[kW]
Superconducting system
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1day average
Cooling energy
Energy saving
5.0%
6.8%
8.2%
9.7%
ACCEPTED MANUSCRIPT Schedules of superconducting feeder system verification
Rail line
Current value on train running test
Current capacity
Cable
Test track
250 A
6960 A
31m
Test track
260 A
1110 A
310m
Connection type between substations
Year 2013 2014
Partially
Commercial line Commercial line
880 A
2080 A
6m
(1000-1500 A)
(8100 A)
410m
Test track or commercial line
-
(4000-8000 A) 2000m Completely
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( ) Designed
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2015
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Table. 5
2018
2021
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Content
Cable
Circulation cooling, Current,
Test track
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Cooling stress
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Rail line
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Table.1Verifying contents of superconducting feeder system by train running test
Current
capacity
31m
6960 A
310m
1110 A
6m
2080 A
Laying through typical line and verification
(circulation cooling, current after laying)
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Electrical test of notch operation
AC C
Commercial line
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Table.2 Effects of Introducing superconducting feeder cable for railways.
Partially
Issue
Completely type
type *
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Regeneration energy
Solution of voltage drop (increase train schedules, fewer substations) *
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*Depending on superconducting cable length
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Load leveling substations
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Solution of feeder energy loss
ACCEPTED MANUSCRIPT Total energy [kW] Substation
Cooling
output
energy
Superconducting system
15130
49%
Conventional system
22939
77%
1314
Regeneration energy[kW]
4%
14328
47%
6681
23%
28.3%
Superconducting system
1314
100%
1314
10%
No train
for 4.5 minutes
Train interval for 2 minutes
44%
Conventional system
9014
73%
Superconducting system
14751
50%
Conventional system
22801
81%
Superconducting system
33586
50%
Conventional system
49977
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6052
1314
1314
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for 10 minutes
Superconducting system
75%
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Train interval
Table. 3 Energy analysis for introduction effects of railway transmission system for one day.
AC C
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Conventional system
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1day average
Energy saving
4%
2%
6292
46% 18.3%
3294
27%
13904
46% 29.5%
5504
19%
31628
48% 30.2%
16883
25%
ACCEPTED MANUSCRIPT Total energy [kW]
Regeneration energy[kW] Substation
Cooling
output
Energy 64%
Conventional system
10856
80%
1238
1day average
Superconducting system
1238
Conventional system
for 5 minutes Train interval For 3 minutes
69%
Conventional system
12472
86%
Superconducting system
13859
60%
Conventional system
16440
Superconducting system
20561
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Train interval
10385
1238
1238
8%
5%
54%
27%
2657
20%
3560
23% 6.8%
2110
14%
8075
35%
6037
27%
1238
3%
16183
43%
Table. 4 Energy analysis for introduction effects of railway transmission system for one day on an average city railway model generally adopted the world.
5.0%
8.2%
73%
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for 8 minutes
Superconducting system
AC C
Train interval
3909
100%
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9%
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9080
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Superconducting system
Energy saving
9.7%
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Schedules of superconducting feeder system verification
Connection
Current value on train
running Current capacity
Cable
test
type between substations
250 A
6960 A
31m
Test track
260 A
1110 A
310m
Commercial line
880 A
2080 A
6m
Commercial line
(1000-1500 A)
(8100 A)
410m
-
(4000-8000 A)
2013
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Test track
Year
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Rail line
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Table. 5
2014
commercial line ( ) Designed
or
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track
AC C
Test
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Partially
2000m
2015 2017 ~2018
Completely
2021
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Highlights Proposed new railway transmission feeder systems using superconducting
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materials
Advantages of high regeneration energy, reduce power loss, solution of
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voltage drop
Laid the system, conducted train running tests and verified on commercial
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line
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Result of analysis, 5% energy saving system on city rail line model