3M-LS-O2 Sep 9 - Morning (10:30-12:30 PM)
Large Scale - Fault current limiters
10:30 - 10:45 Status of superconducting fault current limiter in Italy: final results from the in-field testing activity and preliminary design of the 9kV/15.6MVA device|
ANGELI Giuliano1, BOCCHI Marco1, ASCADE Massimo1, ROSSI Valerio1, VALZASINA Angelo1, RAVETTA Cesare2, MARTINI Luciano1
1Ricerca sul Sistema Energetico - RSE S.p.A., Italy, 2A2A Reti Elettriche S.p.A., Italy
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Ricerca sul Sistema Energetico - RSE S.p.A. has been involved in a six-year long project, funded in the framework of the Italian research fund Ricerca di Sistema (RdS), for the design, development, installation and in-field testing of a 9kV/3.4MVA resistive-type Superconducting Fault Current Limiter (SFCL). The result was a three-phase BSCCO-based prototype installed in a MV substation belonging to the Italian utility A2A Reti Elettriche S.p.A. inside the Milan distribution grid. For the first time in Italy (and one of the first worldwide) a SFCL device was in-field tested for more than two years (March 2012 - June 2014) and its limitation capability was proved during a real three-phase short-circuit.
The main outcomes from the experimentation will be summarized in the first part of this paper; conversely, the second part will be dedicated to the results of the activities undertaken with the aim of developing the upgraded 9kV/15.6MVA SFCL device to be installed in the Milan city distribution grid in late 2015. Initially, two single-phase prototypes were developed: YBCO-based (2G) and BSCCO-based. Both prototypes were DC and AC laboratory tested at the temperatures of 77K and 65K and then short-circuit tested under severe fault conditions. Further to this preliminary activity, a single-phase 2G-based SFCL prototype, representing the first phase of the final three-phase prototype, was developed. The layout consists of two parallel-connected coaxially-arranged 2G windings, each made of two layers anti-inductively wound on a fiberglass-cylinder. The amount of 2G tape used for each winding is 96m. The SFCL device was tested in January 2015 at the nominal current of 1kA and was able to properly limit a reduced short-circuit current (6kArms) and then a full-current of 11kArms corresponding to a peak short-circuit current as high as 26 kAP. The details of the prototype architecture, along with the tests findings, will be described and discussed, as well as the next research steps.
This work has been financed by the Research Fund for the Italian Electrical System under the Contract Agreement between RSE S.p.A. and the Ministry of Economic Development in compliance with the Decree of March 8, 2006.
10:45 - 11:00 Feasibility Study of Superconducting Fault Current Limiters for DC Electric Railway Feeding Systems|
KUMAGAI Daisuke1, QIAN Kezhen1, OHSAKI Hiroyuki1, TOMITA Masaru2
1The University of Tokyo, Japan, 2Railway Technical Research Institute, Japan
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A superconducting power cable has features of a high power transmission capacity, reduced transmission losses, a compactness, etc., and, therefore, it is expected as an alternative technique for a conventional power cable, especially for power grid applications. We have been studying the feasibility of applying superconducting power cables to DC electric railway feeding systems. Our previous studies indicated that superconducting cables could improve the regeneration rate and system energy saving, and also could reduce the substation capacity. On the other hand, it has been concerned that the introduction of superconducting cables would lead to an increase in short circuit currents. A superconducting fault current limiter (SFCL) would be expected for a stable and reliable operation of the DC electric railway systems with superconducting cables.
Requirements for circuit breakers are strict to protect the superconducting cables and the system. However, as the possibility of breaker operation failure cannot be neglected, it is necessary to develop a method to protect the superconducting power cables when the breaker operation fails.
In this study, electric circuit analysis models of the system were created and the system behaviors were investigated by simulation using MATLAB-Simulink. Currents, voltages, temperatures, etc. of the substations, trains and SFCLs were evaluated under various conditions of the location of SFCLs, the operation parameters of circuit breakers, etc. Some fundamental experiments of an SFCL were also carried out. From these results, the effects of introducing SFCLs to the DC electric railway feeding systems with superconducting power cables are discussed.
The research was partly supported by Japan Science and Technology Agency, JST, under Strategic Promotion of Innovative Research and Development Program.
11:00 - 11:15 Studies on the Application of SFCL in the Electrical Power Transmission System|
LI Bin1, YIZHE Ou1
1Tianjin University, China
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It is funded by the National Natural Science Foundation Project (GrantNo.51277130).
11:15 - 11:30 Can resistive type fault current limiter operate in cryogen-free environment?|
VOJENCIAK Michal1, OUC Ján1, DUTOIT Bertrand2, GÖMÖRY Fedor1
1Institute of Electrical Engineering, SAS, Slovakia, 2Ecole Polytechnique Fédérale de Lausanne, Switzerland
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Superconducting fault current limiters are unique devices which don’t have a non-superconducting alternative. Therefore they are interesting for industrial use although their price is high.
Principle of the resistive type fault current limiter is based on steep current - voltage characteristic of the superconductor. When the current rises over the critical one, voltage on the superconductor rises steeply and this mechanism blocks further increase of the current. Simultaneous appearance of voltage and current during this limiting period of operation generates a substantial amount of heat that is dissipated in the superconducting wire causing rapid increase of its temperature. In fact, duration of the limiting period is restricted by maximal allowed temperature.
Most of the current limiters are based on high temperature superconductors (HTS) and use liquid nitrogen as a coolant. Nitrogen in liquid state exhibits high thermal capacity and also the latent heat of evaporation is high. However, during the most critical moments of limiting period nitrogen evaporates so fast that it creates gas film thermally insulating superconductor from liquid.
In this contribution we further develop older idea that during limiting period there is only small difference between cooling by liquid nitrogen bath and adiabatic conditions. Using this approach one can think about current limiter free from a liquid coolant using a cryocooler. Way to realization is, however, not straight-forward. In this contribution we discuss the main differences in cooling conditions and test the idea on short sample of HTS REBCO conductor. We compare parameters such as temperature rise, re-cooling time, etc. for identical samples cooled to the same temperature by liquid nitrogen and cooled by the cryocooler. If the realization can be achieved the huge benefit would be a FCL with tunable triggering current via its operating temperature. Experimental results are supported by numerical modeling.
11:30 - 11:45 Key Factors in Designing a Saturated Iron Core Superconducting Fault Current Limiter|
CUI Jibin1, XIN Ying1, JIN Jianxun2, WEI Ziqiang2
1Futong Group, Co., China, 2Tianjin University, China
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Saturated Iron Core Superconducting Fault Current Limiter (SICSFCL) is one of a few types of superconducting fault current limiters that have been installed for real power grid operation. SICSFCLs become more and more attractive due to its good performance in both normal power transmission and fault current limiting as well as the intrinsic advantage in recovery time and cryogenic load. Since SICSFCL is generally new to most engineers and technicians of utilities and equipment manufacturers, it may be worthwhile to summarize the critical issues and newly developed technologies in designing an SICSFCL. This paper is focus on how to design an SICSFCL properly and efficiently. Key factors in designing each major sub system of an SICSFCL, including the superconductor coil, the reactor, the dc magnetization circuit, the control and protection, and the cryogenics, are introduce and discussed.
11:45 - 12:00 Experimental tests of a resistive SFCL integrated with a vacuum interrupter|
PEI Xiaoze1, SMITH Alexander1, SHUTTLEWORTH Roger1
1The University of Manchester, United Kingdom
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A resistive superconducting fault current limiter (SFCL) has been developed using round magnesium diboride (MgB2) wire. The SFCL coil was wound using an interleaved coil arrangement to minimize the total coil inductance. The SFCL coil demonstrated reliable and repeatable current limiting properties during testing. However, the wire temperature of the SFCL coil increases quickly during quench tests and several minutes are required for temperature recovery after the fault is cleared. The SFCL coil therefore was fully integrated with a vacuum interrupter to quickly remove the SFCL coil from the circuit once a fault occurred. This allowed the SFCL coil to recover quickly whilst a bypass resistor acted as the current limiting resistance. A fast-acting actuator and its control circuit were designed and built to provide automatic control for the operation of the vacuum interrupter. The SFCL with the integrated prototype vacuum interrupter was successfully tested. The energy dissipated in the SFCL coil was significantly reduced by integrating the vacuum interrupter. The fault tests with different potential fault currents also proved that the operation of the vacuum interrupter is independent of the fault current level. This prototype demonstrated the potential of a cost-effective and compact integrated SFCL and vacuum interrupter for power system applications.
The authors would like to thank Rolls-Royce plc. for their support. Thanks are also due to Hyper Tech Research, Inc. for providing the MgB2 wire sample and Scientific Magnetics for the design and manufacture of the cryogenic system.
12:00 - 12:15 Optical and Electrical Investigation of a Novel Method for Improving the Recovery under Load Characteristics of Thin Film Superconductors|
HELLMANN Sebastian1, NOE Mathias1
1Karlsruhe Institute of Technology (KIT), Germany
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Most resistive type superconducting fault current limiters use the controlled quench of a superconductor in the current path to limit fault currents in the power grid via increasing resistivity of the superconducting material.
A resistive type superconducting fault current limiter has to exhibit two main properties: It should facilitate a high electrical resistivity during a fault current in the power grid and it should be capable of recovering to a nominal operating condition as fast as possible after the fault in the grid is cleared.
In order to achieve a sufficient current limitation for a current limiter in the electrical power grid superconducting tapes with a low amount of electrical stabilization are required. However, a high performance in recovery under load demands superconducting tapes with a large amount of thermal and electrical stabilization. For the design of a resistive fault current limiter, this usually leads to a tradeoff between the current limitation performance and the capability of recovery under load.
In this paper we present a novel method for significantly improving the recovery under load characteristics and therefore the recovery time of thin film superconductors in current limiters. This is achieved without decreasing the current limitation performance of the superconductor during the resistive state.
For evaluating the performance of modified superconducting tapes, we use conventional electrical investigation methods as well as high speed camera equipment to determine the different boiling phases of the conductors in the liquid coolant during the current limitation and the recovery phase. In this juncture, especially the acquisition of high speed camera data allows a precise determination not only of the recovery of the superconductor to operation conditions, but also of the quench propagation along the tape during the fault current.
12:15 - 12:30 Multiscale model of a resistive-type superconducting fault current limiters based on 2G HTS coated conductors|
BONNARD Charles-Henri1, SIROIS Frédéric1, LACROIX Christian1, DIDIER Gaëtan2, DOUINE Bruno2
1Ecole Polytechnique de Montreal, Canada, 2Université de Lorraine, France
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Superconducting fault current limiter (SFCL) is one of the most promising applications of second generation (2G) high temperature superconductor (HTS) coated conductors (CCs). In order to plan the integration of SFCLs in real power systems, models of SFCLs should be included in power system transient simulators. In this work, we developed a model of a resistive-type SFCL based on 2G HTS CCs in the EMTP-RV software, which is a reference in power system transient simulation, widely used by power utilities. The model reproduces the complete 3D electro-thermal dynamics of the quench, and therefore allows including critical current inhomogeneities along the length of the tape. Both the electrical and thermal phenomena are modeled using only electric circuits components. All nonlinear properties of the materials entering in the composition of CCs are taken into account. Finite element simulations were performed to validate the circuit model, which can be qualified as “multiscale” since it can at the same time model local quench dynamics of 2G HTS CCs (microscopic scale) and the global impact of the SFCL on the power system (macroscopic/system-scale) when the later operates in real network conditions. The model was used to compare the minimum length of HTS CCs needed to build a SFCL depending on the tape architecture (thickness of the various layers, types of materials used, interfacial resistance between HTS and stabilizer, etc.) for various overcurrent levels. The model was also used to investigate the benefits of 2G HTS CCs with low and high normal zone propagation velocity (NZPV) on the performance of SFCL in comparison with commercially available 2G HTS CCs with low NZPV. Our results show that high NZPV tape increases the quench uniformity and the robustness of the limiter, especially when the current level is close to the critical current (Ic) of the weakest region of the tape.