JP6453004B2 - Superconducting cable soundness diagnosis system and soundness diagnosis method - Google Patents

Description

  The present invention relates to a technical field of a superconducting cable soundness diagnosis system and a soundness diagnosis method for diagnosing soundness by detecting the presence or absence of quenching in a superconducting cable for direct current power transmission in which a conductive layer is made of a superconductor.

  As one of the application fields of superconducting technology that exhibits excellent conductivity in which the electric resistance value becomes substantially zero in a cryogenic region, a power transmission cable that is a power transmission path for transmitting DC power is known. For example, a railway power transmission cable has a relatively low transmission voltage of 1500 (V), and since direct-current power is used, there is no AC loss and it is easy to increase the distance. It is considered as one of For example, when superconducting railway feeders are used, in addition to reducing power loss during power transmission, regenerative braking that occurs when the train is decelerating can be ensured, improving the energy-saving performance of the entire railway power system and further reducing electrical resistance. Various advantages are expected such as being able to solve the electric corrosion problem by being zero.

  In a power transmission cable using superconductivity, if an excessive current exceeding the critical current flows for some reason, the entire cable area may be dislocated (quenched) to the normal conducting phase, which may cause a dangerous accident. In particular, since railway feeders are a backbone system for railways, the impact of accidents is significant, and the establishment of technology to deal with this is required.

  By the way, if the excessive current that causes quenching is due to a normal accident or failure, it can be dealt to some extent by providing a current limiting device on the transmission cable. However, in the case of a power transmission cable grounded on the ground, the occurrence of quenching due to lightning strikes becomes a problem. Because lightning strikes can be received at any position in the system including the power transmission cable, even if a current limiter is installed on the power transmission cable, the lightning current enters the superconducting cable through a route that does not pass the current limiter. there's a possibility that. Then, the superconducting cable is instantly quenched over the entire area, and if the train as a load operates in this situation, the superconducting cable may generate enormous heat and burn out, which is extremely dangerous.

  In the superconducting cable, in order to prepare for the occurrence of such a quench, a technique for quickly diagnosing the soundness of the entire superconducting cable is required. However, as will be described below, with the conventional technology, it is difficult to make a diagnosis with sufficient responsiveness and diagnostic accuracy. In order to diagnose the soundness of a superconducting cable, it is one of effective methods to diagnose the presence or absence of occurrence of quenching by measuring an electric resistance value. For example, Patent Document 1 discloses a technique for diagnosing the presence or absence of quenching by Fourier transforming the voltage across the cable. However, in the application of a power transmission cable, since the superconducting cable extends over a very long distance, it is not realistic to measure the voltage across the cable.

  For such a problem, a method for diagnosing soundness by measuring the temperature of a superconducting cable has been studied. Here, if a large number of thermometers are installed over the entire superconducting cable, the superconducting cable for power transmission is a very long device, requiring a huge number of measurement lines, which is a major obstacle to high-voltage electrical insulation. This is not preferable. Therefore, a soundness diagnostic method has been devised that eliminates the measurement line by using a wireless thermometer or an optical fiber thermometer, and solves the above problems.

  As another method for diagnosing the soundness of a superconducting cable, for example, Patent Document 2 discloses a technique for determining the presence or absence of quenching based on the phase difference of a leakage magnetic field from a superconducting shield.

JP 2009-206237 A JP 2007-73605 A

However, in optical fiber measurement, it is a reality that the measurement resolution is limited to ± 0.1 (K), and there is a problem that it is difficult to obtain sufficient measurement accuracy. On the other hand, wireless temperature measurement has better measurement accuracy than optical fiber measurement, but has a problem of poor responsiveness because soundness is diagnosed based on a temperature change generated as a result of heat generated in the superconducting cable. For these reasons, there is a need for a new technique that replaces the conventional soundness diagnostic technique.
Note that the superconducting cable soundness diagnosis technology described in Patent Documents 1 and 2 above is an arrangement in which voltage measurement at both ends of the cable is easy because the cable is a loop-structured experimental facility. Cable applications have difficult drawbacks.

  The present invention has been made in view of the above-described problems, and the superconducting cable soundness diagnosis system and soundness diagnosis method capable of accurately diagnosing the soundness of a superconducting cable for direct current power transmission with good responsiveness. The purpose is to provide.

In order to solve the above-described problem, a superconducting cable soundness diagnostic system according to an aspect of the present invention has soundness of a superconducting cable for direct current power transmission having conductive layers in which superconducting layers having substantially cylindrical shapes are coaxially arranged. A superconducting cable soundness diagnosis system for diagnosing the problem is generated by a pulse signal input unit that inputs a pulse signal that is an electrical signal having a pulse waveform from one end of the conductive layer, and is generated by the pulse signal in the conductive layer A propagation signal receiving unit for receiving a propagation signal; an electrical resistance measurement unit for measuring an electrical resistance value of the conductive layer based on the received propagation signal; and the superconductivity based on the measured electrical resistance value And a determination unit for determining the soundness of the cable.

  According to this aspect, by inputting a pulse signal to the conductive layer of the superconducting cable for direct current power transmission and measuring the electrical resistance value of the conductive layer based on the propagation signal in the conductive layer, quenching in the conductive layer is performed. It is possible to detect problems such as occurrence. Since such a defect is detected based on a pulse signal propagating through the conductive layer at a high speed, in addition to obtaining excellent responsiveness, it is difficult to reach by a conventional measurement method using an optical fiber or the like. Measurement accuracy can be achieved.

The electrical resistance measurement unit may measure an electrical resistance value of the conductive layer based on an attenuation degree of the propagation signal.
According to this aspect, the attenuation generated when the pulse signal input to the superconducting cable travels back and forth in the conductive layer has a close correlation with the electric resistance value of the conductive layer. The electric resistance value of the conductive layer can be measured based on the signal attenuation. Since the propagation speed of the signal in the conductive layer is very high, the attenuation can be measured in a short time, and soundness determination with excellent responsiveness can be performed.

The determination unit may determine the soundness (for example, burnout or short circuit) of the superconducting cable based on the round trip time of the propagation signal in the conductive layer.
According to this aspect, when there is a defective portion in the superconducting cable, the soundness can be diagnosed based on the change in the round trip time of the signal because the propagation path length in the conductive layer changes. For example, by comparing with the round-trip time theoretically determined from the specifications of the superconducting cable, if there is a discrepancy between the theoretical value and the measured value, it can be determined that there is some defect in the superconducting cable.

In this case, when the determination unit determines that there is an abnormality in the superconducting cable, the determination unit may specify the occurrence point of the abnormality based on the round trip time of the propagation signal in the conductive layer.
According to this aspect, when the soundness is diagnosed based on the round trip time of the propagation signal as described above, the distance to the location where the abnormality occurs can be evaluated based on the round trip time. As a result, it is possible to easily identify a defective portion that has been difficult with the conventional temperature measurement and the diagnostic method using the optical fiber, and it is possible to diagnose information useful for more detailed cause analysis.

A signal generator for generating the pulse signal; an input state in which the pulse signal generated by the previous signal generator is input to the previous conductive layer; and a reception state in which a propagation signal from the conductive layer is transmitted to the receiving unit. The pulse signal input unit and the propagation signal receiving unit may be integrally configured by providing a signal switcher capable of switching between and a switching controller for controlling the signal switcher.
According to this aspect, by switching the input state and the reception state with the signal switcher, the location where the pulse signal is input and the location where the propagation signal from the conductive layer is received are provided at the same position in a compact configuration. Can do.

In this case, the propagation signal receiving unit may receive the propagation signal via a bandpass filter that selectively transmits a predetermined frequency corresponding to the pulse signal.
According to this aspect, by receiving the propagation signal used for obtaining the electric resistance value via the band-pass filter, it is possible to eliminate the influence of external noise and perform accurate soundness diagnosis.

Further, the pulse signal input unit is controlled so that the next pulse signal is automatically input when the attenuation of the received propagation signal reaches a predetermined value. The electric resistance value of the conductive layer may be obtained based on the input interval of the pulse signal input unit.
According to this aspect, the attenuation of the pulse signal is controlled by controlling the pulse signal input unit so that the next pulse signal is automatically input when the attenuation of the previously input pulse signal reaches a predetermined value. The electric resistance value can be obtained based on the input interval of the pulse signal reflecting the above.

The superconducting cable may be a superconducting feeder cable connected to a power supply trolley wire via an inductance component for a lightning arrester.
According to this aspect, when the superconducting cable that is the object of soundness diagnosis is a superconducting feeder that supplies DC power to the power supply trolley wire, an inductance component is provided between the trolley wire and the trolley wire. It is possible to prevent the lightning current that strikes the line from entering the superconducting cable, and it is possible to prevent the pulse signal input to the conductive layer for soundness diagnosis from leaking to the trolley line side. Thereby, since it is not influenced by the load side containing a trolley wire, an accurate soundness diagnosis can be performed.

In order to solve the above-described problem, a method for diagnosing the soundness of a superconducting cable according to an aspect of the present invention has the soundness of a superconducting cable for direct current power transmission having a conductive layer in which superconducting layers having a substantially cylindrical shape are coaxially arranged. A method for diagnosing the soundness of a superconducting coaxial cable, wherein a pulse signal input step of inputting a pulse signal which is an electric signal having a pulse waveform from one end side of the conductive layer, and the pulse signal in the conductive layer by the pulse signal A propagation signal receiving step of receiving a generated propagation signal, an electric resistance value measuring step of measuring an electric resistance value of the conductive layer based on an attenuation amount of a waveform of the received propagation signal, and the measured electric resistance And a determination step of determining the soundness of the superconducting cable based on the value.

The electrical resistance value measuring step may measure the electrical resistance value of the conductive layer based on the attenuation of the propagation signal.
The pulse signal input step automatically inputs the next pulse signal when the attenuation of the received propagation signal reaches a predetermined value, and the electric resistance value measurement step inputs the pulse signal. The electric resistance value of the conductive layer may be obtained based on the interval.

  The superconducting cable soundness diagnosis method according to this aspect can be suitably implemented by the soundness diagnosis system described above (including the various aspects described above).

  According to the present invention, by inputting a pulse signal to the conductive layer of the superconducting cable for direct current power transmission and measuring the electrical resistance value of the conductive conduction based on the propagation signal in the conductive layer, quenching in the conductive layer is performed. It is possible to detect problems such as occurrence. Since such a defect is detected based on a pulse signal propagating through the conductive layer at a high speed, in addition to obtaining excellent responsiveness, it is difficult to reach by a conventional measurement method using an optical fiber or the like. Measurement accuracy can be achieved.

It is a schematic diagram which shows schematic structure of the superconducting cable used as a diagnostic object. It is a schematic diagram which shows the whole structure of the soundness diagnostic system of the superconducting cable which concerns on 1st Embodiment. It is the alternating current equivalent circuit of FIG. It is a schematic diagram which shows the propagation image in the superconducting feeder cable of the high frequency pulse signal input from the pulse signal input part. It is the figure which expanded the waveform which observed the propagation signal in a superconducting feeder cable for about 1 millisecond for a long time. It is a block diagram which shows the other structural example of a pulse signal input part and a propagation signal receiving part. FIG. 7 is a diagram showing an example of a pulse signal waveform obtained by observing the propagation signal in the superconducting feeder cable in about several tens of microseconds. It is an example of measurement data when a propagation signal in a superconducting feeder is observed for a long time of about several tens of milliseconds. It is another example of measurement data when the propagation signal in the superconducting feeder cable is observed for a long time of about several tens of milliseconds. It is a flowchart which shows the soundness diagnostic method of the superconducting cable which concerns on 1st Embodiment for every procedure. It is a flowchart which shows the soundness diagnostic method of the superconducting cable in 2nd Embodiment for every procedure. It is an example of the circuit diagram which shows the pulse signal input circuit in the soundness diagnostic system of the superconducting cable which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. This is just an example.

  First, the schematic structure of the superconducting cable 10 that is the object of soundness diagnosis will be described. FIG. 1 is a schematic diagram showing a schematic structure of a superconducting cable 10 to be diagnosed.

  The superconducting cable 10 is a coaxial cable in which an inner superconducting layer 14, an inner insulating layer 16, an outer superconducting layer 18, and an outer insulating layer 20 are sequentially formed on a former 12 provided at the center. The cooling tube 26 has a structure of 24 having a double tube structure. The inner superconducting layer 14 and the outer superconducting layer 18 (hereinafter referred to as “conductive layer” where appropriate) are formed by spirally winding a Bi-based or Y-based high-temperature superconducting tape wire. The refrigerant (liquid nitrogen) cooled by a refrigerator (not shown) is cooled to such an extent that a superconducting state having an electric resistance value of substantially zero can be stably maintained. DC power for power transmission is supplied between the inner superconducting layer 14 and the outer superconducting layer 18 to achieve high-efficiency power transmission utilizing the characteristics of superconductivity, while there is no magnetic flux leakage to the outside due to the electromagnetic shielding function. It has the characteristics.

  A low-temperature refrigerant supplied from a refrigerator (not shown) is supplied from one end side (left side in FIG. 1) into the former 12 having a hollow structure, and after cooling the heat load, the other end side (right side in FIG. 1). A so-called Go-Return Flow method is employed in which the cooling is performed by passing through a space 28 formed between the inner tube 22 and the outer insulating layer 20 of the cooling tube 26. In addition, the cooling pipe 26 has a vacuum heat insulating structure in which the space 28 between the inner pipe 22 and the outer pipe 24 is depressurized by a decompression device such as a vacuum pump, and prevents heat from entering from outside at room temperature. Yes.

(First embodiment)
FIG. 2 is a schematic diagram showing the overall configuration of the soundness diagnostic system 100 for the superconducting cable 10 according to the first embodiment. In this example, as the superconducting cable 10 to be diagnosed, a superconducting feeder used in a railway power transmission system for supplying DC power to the electric vehicle 34 via the trolley wire 32 is adopted (hereinafter referred to as “superconducting cage” as appropriate). Referred to as electric wire 10 "). In this type of railway power transmission system, by connecting the substations 36 with the superconducting feeder 10, power interchange between the substations 36 can be facilitated, and the regenerative power from the electric vehicle 34 is reliably and effectively used. be able to.

  In FIG. 2, the detailed configuration of the superconducting feeder cable 10 is omitted for easy understanding of the configuration, and only the inner superconducting layer 14 and the outer superconducting layer 18 are typically shown. The substation 36 is connected to the inner superconducting layer 14 and the outer superconducting layer 18 through a pair of wirings, and a current limiter 38 is provided as a protection device when an excessive current is generated in the wirings. Further, the outer superconducting layer 18 is grounded by being connected to the rail 35 of the electric vehicle 34, and the inner superconducting layer 14 is connected to the substation 36 and to the trolley wire 32, whereby the substation 36 is connected. DC power transmitted from the vehicle is supplied to the electric vehicle 34 via the trolley line 32.

Since the railway power transmission system is provided on the field, an excessive pulse current may enter the superconducting feeder 10 due to, for example, a lightning strike. As a countermeasure against such an excessive pulse current, an inductance Lx is provided on the wiring connecting the inner superconducting layer 14 and the trolley wire 32, and the pulse current caused by the lightning strike is returned to the ground via the lightning arrester 40. Further, between the inner superconducting layer 14 and the inductance Lx, a pulse signal input unit 42 for inputting a high-frequency pulse signal (current or voltage) for performing a soundness diagnosis to be described later, and propagation in the superconducting feeder cable 10. Propagation signal receiving unit 43 that receives the signal, electric resistance measurement unit 44 that measures the electric resistance value of the superconducting feeder cable based on the received propagation signal, and the soundness of the superconducting cable 10 is determined based on the measured electric resistance value And a determination unit 45 that performs the determination.
The electrical resistance measurement unit 44 and the determination unit 45 are configured by an electronic computing unit such as a computer, for example, and may include a display for displaying measurement results and diagnosis results as necessary.

FIG. 3 is the AC equivalent circuit of FIG. In FIG. 3, the superconducting feeder 10 is represented as a distributed constant circuit including an inductance l, a capacitance c, and a resistance component r per unit length. If it explains supplementarily, if superconducting feeder cable 10 is completely zero resistance to a high frequency pulse signal, it is r = 0, but in reality, it does not become complete zero resistance to a high frequency pulse signal. Moreover, the high frequency pulse signal input to the superconducting feeder 10 does not leak to the trolley wire 32 due to the presence of the inductance Lx. Further, the impedance Z _H substations 36 as compared to the characteristic impedance Z ₀ of the superconducting feeder line 10, since in general sufficiently small, the AC equivalent circuit is regarded as short-circuit state.

Further, as described above, the inner superconducting layer 14 and the outer superconducting layer 18 constituting the superconducting feeder 10 are each formed by spirally winding a number of Bi-based and Y-based superconducting tape wires, but have an inductance component. In order to simplify the explanation, these conductive layers are regarded as electrically integrated uniform cylindrical conductors. Furthermore, the AC characteristics of the superconducting feeder 10 can be expressed simply by the following distributed constant circuit. To do.

ここでＶ_１ｎ、Ｖ_２ｎ、Ｗ_１ｎ、Ｗ_２ｎは初期条件や境界条件で決まる定数であり、ｎはゼロを除く自然数である。 The above equation (1) is a hyperbolic parabolic equation, which is the wave equation itself. Since the left side of the equation is expressed only by the time term and the right side is expressed only by the place function, the analytical solution is obtained by applying the variable separation method as follows.

Here, V _1n , V _2n , W _1n and W _2n are constants determined by initial conditions and boundary conditions, and n is a natural number excluding zero.

According to the equation (2), the high-frequency pulse signal input from the pulse signal input unit 42 is attenuated according to the exponential function exp (−0.5 (r / l) t) in the superconducting feeder cable 10. Has been. Further, in view of the fact that the equation (1) is a wave equation, the propagation speed U ₀ and the characteristic impedance Z ₀ of the high-frequency pulse signal transmitted through the superconducting feeder 10 that is a coaxial cable can be obtained by the following equations.

但し、μ_０及びε_０は真空中の透磁率、誘電率、ε_ｒは電気絶縁体の比誘電率である。ちなみにμ_０、ε_０の具体的な値は以下のとおりである。

Here, when the specifications (inner conductor diameter D _i , outer conductor diameter D _o ) of the superconducting feeder cable 10 defined as shown in FIG.
And c are obtained as follows.

Where μ ₀ and ε ₀ are the magnetic permeability and dielectric constant in vacuum, and ε _r is the relative dielectric constant of the electrical insulator. Incidentally, specific values of μ ₀ and ε ₀ are as follows.

尚、超電導饋電線１０の特性インピーダンスＺ_０は数１０Ωであるが、変電所３６のインピーダンスが十分に小さく、交流回路的に短絡状態に近いため、Ｚ_Ｈ≒０と見なすこととする。 Here, FIG. 4 is a schematic diagram showing a propagation image of the high-frequency pulse signal input from the pulse signal input unit 42 in the superconducting feeder cable 10. 4 (a) to 4 (c) show the state of the propagation signal generated by the high-frequency pulse input into the superconducting feeder cable 10 in time series order. The input high-frequency pulse signal of one wavelength is superconductive. A state in which the reflection is attenuated at both ends of the feeder 10 is shown. The state of reflection of the high-frequency pulse signal at both ends is determined by the high-frequency impedance Z _H of the substation 36 connected to both ends of the superconducting feeder cable 10 and the characteristic impedance Z ₀ of the superconducting feeder cable 10. Here, when the current amplitude of the high frequency pulse signal at both ends of the superconducting feeder cable 10 is i ₁ and the current amplitude of the propagation signal appearing in the substation 36 is i ₂ , the following equation is established.

Although the characteristic impedance Z ₀ of the superconducting feeder cable 10 is several 10 [Omega, the impedance is sufficiently small substation 36, close to the AC circuit shorted condition, and be regarded as a Z _H ≒ 0.

となり、超電導饋電線１０の寸法（Ｄ_０やＤ_ｉ）とは無関係に、伝播速度はＵ_０≒３×１０^８（ｍ／ｓｅｃ）となる。これは、光速に等しい伝播速度である。しかし実際には内側絶縁層１６や外側絶縁層２０は真空ではなく、電気絶縁体であるガラス繊維や紙が用いられているため、比誘電率が３〜１０、あるいは２〜２．５と大きくなる。また、超電導饋電線１０の導電層である内側超電導層１４及び外側超電導層１８もまた高温超電導テープ線材を巻きつける構造なのでインダクタンス成分を有することから、単純な同軸円筒板金属板構造で生じるインダクタンス値より大きいと考えられる。従って伝播速度Ｕ_０も光速以下になるが、それでも伝播速度Ｕ_０は十分に高速である。 If the inner insulating layer 16 and the outer insulating layer 20 of the superconducting feeder cable 10 are vacuum layers, the propagation speed is

Thus, regardless of the dimensions (D ₀ or D _i ) of the superconducting feeder cable 10, the propagation speed is U ₀ ≈3 × 10 ⁸ (m / sec). This is a propagation velocity equal to the speed of light. However, since the inner insulating layer 16 and the outer insulating layer 20 are not made of vacuum but are made of glass fiber or paper, which is an electrical insulator, the relative dielectric constant is as large as 3 to 10, or 2 to 2.5. Become. In addition, since the inner superconducting layer 14 and the outer superconducting layer 18 which are conductive layers of the superconducting feeder cable 10 also have a structure in which a high temperature superconducting tape wire is wound, the inductance value generated in a simple coaxial cylindrical plate metal plate structure. It is considered larger. Accordingly, the propagation speed U _{0 is} also lower than the speed of light, but the propagation speed U ₀ is still sufficiently high.

For example, if the length of the superconducting feeder cable 10 is 1 (km) and the propagation velocity is U ₀ = 1 × 10 ⁸ (m / sec), the time for the high-frequency pulse signal to reciprocate the superconducting feeder cable 10 is Δτ = 2 × 1000/10 ⁸ = 20 × 10 ⁻⁶ = 20 (μsec). In this case, as will be described later, even if it is reciprocated 1000 times in order to clearly observe how the high-frequency pulse signal is attenuated, the necessary time is only 0.02 seconds. Sex judgment can be made.

  The attenuation of the high-frequency pulse signal input to the superconducting feeder cable 10 depends on the inductance l and the resistance r per unit length of the superconducting feeder cable 10 as shown in the equation (2), but the inductance l is (4-1). ) Is a known amount obtained from the equation (1), the attenuation state changes depending on the resistance r. In the soundness diagnosis system 100 according to the present embodiment, the electrical resistance value of the superconducting feeder 10 is measured by using the characteristic that the attenuation degree of the high-frequency pulse signal depends on the resistance r in this way, and quenching or the like is performed. The presence or absence of abnormality can be diagnosed.

4 shows the state of a high-frequency pulse signal propagating in the superconducting feeder cable 10 for easy understanding of the measurement principle in the present embodiment, but in actual measurement, the propagation in the superconducting feeder cable 10 is shown. It is difficult to follow and observe signals directly. Therefore, in this embodiment, the propagation signal receiving unit 43 that receives the propagation signal is arranged in the vicinity of the pulse signal input unit 42, but in principle, it may be provided at any position on the superconducting feeder cable 10. Needless to say.
As will be described later, the propagation signal receiving unit 43 may be configured as a CT (current transformer) together with the pulse signal input unit 42, or may simply use a capacitance of several hundreds (pF).

  FIG. 5 is a diagram showing the change over time of the amplitude of the propagation signal in the superconducting feeder cable 10. The pulse signal input from the pulse signal input unit 42 has a maximum amplitude at the time of input, and thereafter attenuates exponentially as time passes. In this embodiment, since the pulse signal input unit 42 periodically inputs a pulse signal, FIG. 5 shows a state in which a plurality of pulse signals are attenuated. In this example, the case where the input frequency of the pulse signal is 100 Hz is shown.

Here, assuming that the length of the superconducting feeder 10 is L = 1000 (m), the diameter of the inner superconducting layer 14 is D _i = 3 (cm), and the diameter of the outer superconducting layer 18 is D ₀ = 6 (cm), A time change of the propagation signal in the superconducting feeder 10 will be obtained by simulation. The high-frequency pulse signal input to the superconducting feeder 10 does not leak to the trolley wire 32 side by the reactor Lx (see FIG. 2). When the specifications D _i and D ₀ of the superconducting feeder cable 10 are substituted into the equation (4), the inner superconducting layer 14 and the outer superconducting layer 18 are assumed to be conductive layers of the superconducting feeder cable 10 and the outer superconducting layer 18. Is a simple metal tube, the inductance per unit length is l ₀ = 1.3863 × 10 ⁻⁷ (H / m), but the conductive layer is formed by winding a high-temperature superconducting tape wire. Therefore, it is assumed that l = 2.77258 × 10 ⁻⁷ (H / m), which is approximately twice as large.

Furthermore, when the relative dielectric constant of the electrical insulating material forming the inner insulating layer 16 and the outer insulating layer 20 is ε _r = 2 and the capacity per unit length is c = 160.52 × 10 ⁻¹² (F / m), The propagation speed of the high frequency pulse signal in the superconducting feeder cable 10 is U ₀ = 1.499 × 10 ⁸ (m / sec), and the characteristic impedance is Z ₀ = 41.6 (Ω).
Incidentally, substantially assumed zero because the impedance of the substation 36 is considered much lower than the characteristic impedance Z ₀ of the cable.

を避けるように４０５．５（ｋＨｚ）を選択している。 The pulse signal input unit 42 inputs a sine wave having a frequency f = 405.5 (kHz) cut out in units of one wavelength as a pulse signal. The frequency of the sine wave from which the high-frequency pulse signal is cut out can be freely selected. However, in this embodiment, the time for the high-frequency pulse signal to reciprocate in the superconducting feeder 10 is 2 L / U ₀ = 13. Since it is 3 × 10 ⁻⁶ (sec), there is a resonance frequency of the superconducting feeder 10

405.5 (kHz) is selected to avoid this.

  FIG. 6 is a block diagram illustrating another configuration example of the pulse signal input unit 42 and the propagation signal reception unit 43. In this example, a signal generator 46 that generates a pulse signal, an input state in which the pulse signal generated by the signal generator 46 is input to the conductive layer, and a propagation signal from the conductive layer are transmitted to the propagation signal receiving unit 43. The pulse signal input unit 42 and the propagation signal receiving unit 43 are integrally configured by including a signal switching unit 48 that can switch the reception state and a switching controller 50 that controls the signal switching unit 48. . In particular, the propagation signal receiving unit 43 passes through a band-pass filter 52 that selectively transmits a predetermined frequency corresponding to the pulse signal, and then amplifies the signal to an optimum level by the amplification & signal processing device 54, thereby performing soundness diagnosis. It is configured to function also as an interface between the electrical resistance measurement unit 44 and the determination unit 45 that implement the above.

  More specifically, first, the signal generator 46 generates one wavelength of a high-frequency signal of 405.5 (kHz), and the signal switch 48 is switched to disconnect the band-pass filter 52 side and to generate a signal from the receiving side. A high frequency pulse signal is input to the superconducting feeder 10 by preventing intrusion and connecting to the superconducting feeder 10 side. Thereafter, by switching the signal switch 48, the signal generator 46 is disconnected to prevent signal intrusion from the input side, and the propagation signal in the superconducting feeder 10 is received by connecting the bandpass filter 52 side. .

  As described above, in FIG. 6, by switching control between the input state and the reception state by the signal switch 48, the location where the pulse signal is input and the location where the propagation signal from the conductive layer is received are in the same position with a compact configuration. Can be provided. For example, space saving and compactness can be realized by integrally forming the pulse signal input unit 42 and the propagation signal receiving unit 43 from one CT. In addition, by receiving the propagation signal used for obtaining the electric resistance value via the band pass filter 52, it is possible to eliminate the influence of external noise and the like and perform a soundness diagnosis with high accuracy.

  FIG. 7 is a diagram showing an example of a propagation signal in the superconducting feeder cable 10. In FIG. 7, ± 1 (A) is used for easy understanding of the amplitude of the propagation signal in the superconducting feeder 10, but it can be sufficiently measured at ± 0.1 (A) or less.

As shown in FIG. 7, the high-frequency pulse signal input to the superconducting feeder 10 is a pulse signal having a clean waveform for one wavelength at the beginning. Disturbances occur in the waveform due to the influence of reflection and resonance of the part. Therefore, it is necessary to ensure a sufficiently long measurement time in order to grasp the attenuation amount of the high-frequency pulse signal in the superconducting feeder cable 10. As described above, the time required for the high-frequency pulse signal to reciprocate through the superconducting feeder cable 10 is 2 L / U _0. If this time is short, the conductive layer is damaged in the middle of the superconducting feeder cable 10 such as burning or short circuit. This suggests the possibility of That is, as will be described later, in addition to the absolute value evaluation of the electrical resistance value, the determination unit 45 evaluates the round-trip time of the propagation signal, thereby providing more detailed information such as the presence or absence of damage to the superconducting feeder cable 10 and the damage position. It is also possible to make a diagnosis.

  In the above description, it has been described that long-time measurement is necessary for the soundness diagnosis of the superconducting feeder cable 10, but the period is only 10 (msec). Since this is much faster than measurement using a thermometer, it is still possible to perform soundness diagnosis with sufficiently excellent responsiveness.

  FIG. 8 is an example of measurement data of a propagation signal in the superconducting feeder cable 10. In this data, the entire state in which the amplitude is attenuated to substantially zero by capturing the input interval of the high-frequency pulse signal sufficiently long is captured. Specifically, the input frequency is set to 100 Hz (that is, input at an interval of 0.01 seconds), and the amplitude of the high frequency pulse signal is attenuated to approximately zero after about 2 (msec) from the time of input. Yes.

In FIG. 8, the amplitude of the high frequency pulse signal is attenuated by about 2% after 1 (msec) from the time of input. Therefore, the electrical resistance measuring unit 44 applies the propagation signal received by the propagation signal receiving unit 43 to the attenuation term exp (−r / l) t / 2, and substitutes l = 2.77258 × 10 ⁻⁷ (H / m). By doing so, the resistance per conductor unit length of the superconducting feeder cable 10 can be obtained as r = 13.8 × 10 ⁻⁴ ≈10 ⁻⁵ (Ω / m). Thus, the electrical resistance value of the superconducting feeder 10 can be measured based on the attenuation state of the propagation signal.

FIG. 9 shows another example of the measurement data of the propagation signal in the superconducting feeder cable 10. FIGS. 9A and 9B show the resistance per unit length of the superconducting feeder cable as r = 5 × 10 ^−4. The attenuation state of the high-frequency pulse signal observed when (Ω / m) and r = 1 × 10 ⁻⁴ (Ω / m) is shown. From these results, it is apparent that the attenuation state of the high-frequency pulse signal depends on the resistance r per conductor unit length of the superconducting feeder cable 10.

  FIG. 10 is a flowchart showing the soundness diagnosis method for the superconducting cable 10 according to the first embodiment for each procedure. First, the pulse input unit 42 inputs one pulse signal (step S101). The pulse signal input here attenuates as time passes as shown in FIG. The propagation signal receiving unit 43 receives the propagation signal (step S102), and the electrical resistance measurement unit 44 measures the electrical resistance value based on the attenuation of the propagation signal according to the principle described above (step S103).

Subsequently, the determination unit 45 determines whether or not the electrical resistance value r calculated in step S104 exceeds a threshold value r ^* set in advance in order to determine the presence or absence of quenching (step S104). When the electrical resistance value r exceeds the threshold value r ^* (step S104: YES), the determination unit 45 determines that there is a possibility of quenching in the superconducting cable 10 and “abnormality exists” (step S105). On the other hand, when the electrical resistance value r is less than the threshold value r ^* (step S104: NO), the determination unit 45 determines that “no abnormality” has occurred in the superconducting cable 10, and repeats the measurement (step S106). ).

  Thus, in this embodiment, soundness diagnosis is performed by measuring an electrical resistance value based on the attenuation degree of the propagation signal in the superconducting cable 10. In particular, since the speed of the propagation signal is very high, attenuation can be measured in a short time, and soundness determination with excellent responsiveness can be performed.

  The determination unit 45 may determine the soundness such as burnout or short circuit in the superconducting cable 10 based on the round trip time of the propagation signal. In this case, when there is a defective portion in the superconducting cable 10, the soundness can be diagnosed based on the change of the round trip time of the propagation signal. For example, by comparing with the round-trip time theoretically determined from the specifications of the superconducting cable 10, it can be determined that there is some defect in the superconducting cable when there is a difference between the theoretical value and the measured value. .

  In this case, when the determination unit 45 determines that there is an abnormality, since the propagation speed of the propagation signal is already known as described above, the distance to the location where the abnormality occurs is specified based on the round trip time. Can do. That is, since it is possible to identify a defective portion that has been difficult with the conventional diagnosis method, a more detailed diagnosis is possible.

  The measurement method described above is particularly effective for a DC superconducting cable having a coaxial structure. For example, in a superconducting cable for three-phase AC power transmission that transmits three-phase alternating current, if you try to check the soundness of one phase by the above method, the other phases will be affected, and accurate soundness in each phase Will become difficult. Moreover, in the superconducting cable for AC power transmission, since the power transmission target is AC power, there is a concern about an increase in noise due to confusion between the high-frequency pulse signal and the commercial frequency, so that the measurement accuracy is likely to deteriorate.

  As described above, according to the present embodiment, the soundness is diagnosed by inputting a high frequency pulse signal to the superconducting cable 10 for direct current power transmission and measuring the electrical resistance value based on the received propagation signal. , Such as quenching can be accurately detected over a long distance. Such soundness diagnosis is performed using a pulse signal that propagates at a high speed, and thus can be performed with responsiveness and accuracy that are difficult to reach by conventional methods.

(Second Embodiment)
Next, a soundness diagnostic system for a superconducting cable according to a second embodiment will be described. In the first embodiment described above, the diagnosis is performed by evaluating the resistance r per unit length based on the propagation degree of the superconducting cable 10, but the present embodiment is different in that the diagnosis is performed using a simpler electronic circuit. ing.
Since the basic configuration of the superconducting cable soundness diagnostic system according to this embodiment is the same as that of the first embodiment, common portions are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. To do.

FIG. 11 is a flowchart showing the soundness diagnosis method for the superconducting cable 10 in the second embodiment for each procedure. First, the pulse input unit 42 inputs one pulse signal (step S201). The pulse signal input here attenuates as time passes as shown in FIG. The propagation signal receiving unit 43 receives the propagation signal (step S202), and determines whether or not the amplitude of the propagation signal is smaller than a predetermined threshold value I ^* (step S203). When the amplitude of the propagation signal becomes smaller than the predetermined threshold value I ^* (step S203: YES), the pulse signal input unit 42 inputs the next one pulse signal and outputs the input frequency based on the input interval of the pulse ( Step S204).

Subsequently, the electrical resistance measurement unit 44 correlates the input frequency output in step S204 with the electrical resistance per unit length of the cable. Based on this, the electrical resistance value r per unit length of the cable is calculated. Calculate (step S205). The input frequency and the electric resistance value r per unit length of the cable are correlated with each other. For example, if the input frequency is high, it means that the resistance component r of the superconducting cable 10 is large.
The relationship between the input frequency and the electrical resistance value r per unit length of the cable may be stored in advance in a storage unit such as a memory as a map. Then, the determination unit 45 determines whether or not the electrical resistance value r calculated in step S205 has exceeded a preset threshold value r ^* in order to determine whether or not there is a quench (step S206).

When the electrical resistance value r exceeds the threshold value r ^* (step S206: YES), the determination unit 45 determines that there is a possibility of quenching in the superconducting cable 10 and “abnormality exists” (step S207). On the other hand, when the electrical resistance value r is less than the threshold value r ^* (step S206: NO), the determination unit 45 determines that “no abnormality” has occurred in the superconducting cable 10, and repeats the measurement (step S208). ).

  Since the input frequency is several Hz to several hundred Hz according to the results of FIGS. 8 and 9, the superconducting cable 10 having a length of 1 (km) is based on the measurement sound in the human audible sound region. It is also possible to determine the abnormal state of the cable.

  Next, a specific input circuit for realizing the pulse signal input method in steps S201 to S204 will be described. FIG. 12 is an example of a circuit diagram showing a pulse signal input circuit in the superconducting cable soundness diagnostic system according to the second embodiment.

The pulse signal input circuit includes a band-pass filter circuit 60, a detection circuit 62, a comparison circuit 64, and a one-shot pulse generation circuit 66. When a propagation signal generated in the superconducting cable 10 is received by the previously inputted pulse signal, the received propagation signal is inputted to the pulse signal input circuit from the left side of FIG. The input propagation signal is filtered by the band-pass filter circuit 60, and then detected by the detection circuit 62 to become an analog electric signal. When the comparison circuit 64 determines that the level of the received signal is equal to or less than the reference value I ^* by comparing the input level from the detection circuit 62 with a separately generated reference level, the one-shot pulse generation circuit 66 causes the one-shot pulse generation circuit 66 to The pulse generation circuit 66 is urged to generate the next pulse signal.

  In this manner, the electronic circuit shown in FIG. 12 can be realized at a low cost because all stages are configured by readily available operational amplifiers. In order to reduce the cost, a TTL type IC can be used instead of the high-frequency operational amplifier.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a superconducting cable soundness diagnosis system and soundness diagnosis method for diagnosing soundness by detecting the presence or absence of quenching in a superconducting cable for direct current power transmission in which a conductive layer is made of a superconductor.

DESCRIPTION OF SYMBOLS 10 Superconducting cable 12 Former 14 Inner superconducting layer 16 Inner insulating layer 18 Outer superconducting layer 20 Outer insulating layer 26 Cooling pipe 32 Trolley wire 34 Electric car 35 Rail 36 Substation 38 Current limiter 40 Lightning arrester 42 Pulse signal input part 43 Propagation signal reception Unit 44 Electrical resistance measurement unit 45 Judgment unit 46 Signal generator 48 Signal switch 50 Switch controller 52 Band pass filter 54 Amplification & signal processing device 60 Filter circuit 62 Detection circuit 64 Comparison circuit 66 One-shot pulse generation circuit 100 Soundness diagnosis system

Claims (11)

A superconducting cable health diagnostic system for diagnosing the health of a superconducting cable for direct current power transmission having a conductive layer in which superconducting layers having a substantially cylindrical shape are coaxially arranged with each other,
A pulse signal input unit for inputting a pulse signal which is an electrical signal having a pulse waveform from one end side of the conductive layer;
A propagation signal receiver for receiving a propagation signal generated by the pulse signal in the conductive layer;
Based on the received propagation signal, an electrical resistance measurement unit that measures an electrical resistance value of the conductive layer;
A superconducting cable soundness diagnostic system comprising: a determination unit that determines soundness of the superconducting cable based on the measured electric resistance value.   The superconducting cable soundness diagnosis system according to claim 1, wherein the electrical resistance measurement unit measures an electrical resistance value of the conductive layer based on an attenuation degree of the propagation signal.   2. The superconducting cable soundness diagnostic system according to claim 1, wherein the determining unit determines soundness of the superconducting cable based on a round-trip time of the propagation signal in the conductive layer.   The said determination part specifies the generation | occurrence | production location of the said abnormality based on the round trip time of the said propagation signal in the said conductive layer, when it determines with the said superconducting cable having abnormality. Superconducting cable health diagnostic system. A signal generator for generating the pulse signal;
A reception state and a switchable signal switching device for transmitting a propagation signal from the conductive layer and the input state for inputting a pulse signal generated by the signal generator to the conductive layer to the receiving unit,
By comprising a switching controller for controlling the signal switcher,
2. The superconducting cable health diagnosis system according to claim 1, wherein the pulse signal input unit and the propagation signal receiving unit are integrally configured.   6. The soundness diagnosis of a superconducting cable according to claim 5, wherein the propagation signal receiving unit receives the propagation signal through a band-pass filter that selectively transmits a predetermined frequency corresponding to the pulse signal. system. The pulse signal input unit is controlled so that the next pulse signal is automatically input when the attenuation of the received propagation signal reaches a predetermined value.
2. The superconducting cable soundness diagnostic system according to claim 1, wherein the electrical resistance measurement unit obtains an electrical resistance value of the conductive layer based on an input interval of the pulse signal input unit.   2. The superconducting cable health diagnosis system according to claim 1, wherein the superconducting cable is a superconducting feeder cable connected to a power supply trolley wire via an inductance component. A method for diagnosing the health of a superconducting coaxial cable for diagnosing the health of a superconducting cable for direct current power transmission having a conductive layer in which superconducting layers having a substantially cylindrical shape are coaxially arranged with each other,
A pulse signal input step of inputting a pulse signal which is an electrical signal having a pulse waveform from one end side of the conductive layer;
A propagation signal receiving step of receiving a propagation signal generated by the pulse signal in the conductive layer;
An electrical resistance value measuring step of measuring an electrical resistance value of the conductive layer based on the attenuation of the waveform of the received propagation signal;
And a determination step for determining the soundness of the superconducting cable based on the measured electrical resistance value.   The method of diagnosing the superconducting cable according to claim 9, wherein the electrical resistance value measuring step measures an electrical resistance value of the conductive layer based on an attenuation degree of the propagation signal. The pulse signal input step automatically inputs the next pulse signal when the attenuation of the received propagation signal reaches a predetermined value,
The method of diagnosing the soundness of a superconducting cable according to claim 9, wherein the electrical resistance value measuring step obtains an electrical resistance value of the conductive layer based on an input interval of the pulse signal.

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