Vol.7 No.4 2015

Research paper : Preparation of superconducting films by metal organic deposition (T. MANABE et al.)−240−Synthesiology - English edition Vol.7 No.4 (2015) quality large-surface-area superconducting film using the MOD method for application to FCL, under “R&D of the Core Technology for Superconducting AC Equipment”[1] funded for the Technological Development for Diversification of Power Source of the New Energy and Industrial Technology Development Organization (NEDO) and others.2 Necessity for device against accidental current such as FCL, and the required specification for the superconducting film in the thin film type FCLIt was mentioned in the previous chapter that one of the applications of the superconducting thin film is to the thin film resistive-type FCL. To meet the demands of electric power deregulation and power shortage, the grid interconnection is promoted in which the distributed power supply such as excess power from home generated sources are connected and operated using the distribution lines of the electric power companies. When the distributed power supply sites are connected, in cases of short-circuit accidents as shown in Fig. 1(a), large overcurrent (accidental current or fault current) flows through the grid system instantly, and this may cause whole area blackout, damage the distributed power generators, and harm power appliances. To avoid such accidental damages, expensive additions must be made to facilities such as changing the existing distribution lines and Fig. 1 Installation of FCL in distributed power supply siteG G Newly built power supplyDistribution line breaker×Inhibits overcurrentOvercurrentEasy to formulate facilitiesLow costStrengthen facilitiesHigh cost【Installation of FCL】Existing distribution lines and breakers can be used【Measures against accident/fault】Change existing distribution lines and breakers to larger ratingNewly built power supply damaged(b) With FCL(a) Without FCLBlackout area is localizedWhole area blackoutExisting facilities damaged××××××FCL installed77 kV transmission lineAccident/faultTransformerDistribution line6.6 kV bus lineTransformerBreakerNewly built breakerOccurrence of resistance by SN transition→Instantly breaks short-circuit currentTimeCurrentCritical temperatureSuperconducting(S)0Short-circuitingCritical currentNormal conducting(N)TemperatureLiquid nitrogen coolantSuperconducting current limiting elementCurrent leadYBCO superconducting film (uniform critical current distribution)Buffer layer (lattice matched, inhibits interface reaction)Large-area substrate of sapphire (high thermal conductivity) etc.Instantly breaks short-circuit current→Strong demand from power industryCoatingSubstrateCoating solutionSuperconducting filmPrefired filmFig. 3 Metal organic deposition (MOD) methodFig. 2 Superconducting thin film FCL (SN transition type)


page 44