Power transmission line evaluation system and power transmission line evaluation method

Abstract

The power transmission line evaluation system is connected to a power transmission line including a power cable having a conductor, an insulating layer, and a shielding layer in that order in the radial direction of the conductor, and includes a power source capable of applying a voltage between the conductor and the shielding layer, and a charge amount measuring unit connected in series between the power source and the power transmission line and measuring a charge amount, which is the integral value of the current flowing between the conductor and the shielding layer of the power transmission line.

Description

[Technical field]

[0001] The present disclosure relates to a power transmission line evaluation system and a power transmission line evaluation method. [Background technology]

[0002] Various methods have been disclosed as methods for evaluating the insulating layer of a power cable (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-29450 A Summary of the Invention

[0004] According to one aspect of the present disclosure, there is provided a power transmission line evaluation system including: a power cable having a conductor, an insulating layer, and a shielding layer in this order in a radial direction of the conductor, the power transmission line evaluation system being connected to the power transmission line and capable of applying a voltage between the conductor and the shielding layer; and a charge amount measuring unit connected in series between the power supply and the power transmission line, the charge amount being an integral value of a current flowing between the conductor and the shielding layer of the power transmission line. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic configuration diagram showing a power transmission line evaluation system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is an enlarged schematic diagram of the configuration in the vicinity of the power transmission line in FIG. [Diagram 3] FIG. 3 is an enlarged schematic diagram of the configuration in the vicinity of the radio unit in FIG. [Figure 4] FIG. 4 is a block diagram showing the management center. [Diagram 5] FIG. 5 is a flowchart illustrating a power transmission line evaluation method according to an embodiment of the present disclosure. [Figure 6]FIG. 6 is a diagram showing the sequence of a voltage application step and a charge amount measurement step. [Figure 7] FIG. 7 is a schematic diagram showing a conventional insulating material evaluation system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] An object of the present disclosure is to assess the condition of a power transmission line based on the charge mass characteristics of the power transmission line.

[0007] [Effects of this disclosure] According to the present disclosure, the condition of a power transmission line can be evaluated based on the charge amount characteristics of the power transmission line.

[0008] [Description of the embodiments of the present disclosure] <Knowledge gained by the inventors> First, the findings of the inventors will be described.

[0009] The inventors have developed a method for evaluating the insulating material contained in the insulating layer of a power cable by the so-called current-integrated charge method (also called the Q(t) method).

[0010] In the previous studies by the inventors, for example, an insulating material evaluation system 90 as shown in Fig. 7 was used. Specifically, the insulating material evaluation system 90 included, for example, a power supply 920, a switch 922, a switch 924, and a charge amount measurement unit 930 including a capacitor 932 and a switch 934.

[0011] The evaluation target was a sheet 910 containing an insulating material. A first electrode 912 and a second electrode 914 were provided on the front and back surfaces of the sheet 910, respectively. Furthermore, a guard electrode 916 was provided on the back surface of the sheet 910 so as to surround the outer periphery of the second electrode 914, and the guard electrode 916 was grounded.

[0012] In the conventional insulating material evaluation method, for example, a power source 920, a switch 922, a switch 924, and a switch 934 are used to apply a square wave voltage between a first electrode 912 and a second electrode 914, thereby causing an electric charge flowing in the thickness direction of a sheet 910 containing an insulating material to be accumulated in a capacitor 932. In this way, the amount of electric charge accumulated in the capacitor 932 is measured. Note that the characteristic obtained by measuring the amount of electric charge, which is the integral value of the current flowing through the evaluation target, is also referred to as the "electric charge characteristic" below.

[0013] Conventional insulating material evaluation methods have evaluated the characteristics of insulating materials, including at least one of the dielectric constant, space charge characteristics, electrical conductivity, etc., based on the charge amount characteristics of the insulating material obtained by the measurements described above.

[0014] However, in the conventional insulating material evaluation system 90, the evaluation target was limited to a thin sheet 910, and the voltage that could be applied by the power source 920 was low. For this reason, the insulating material evaluation system 90 was not able to evaluate the charge quantity characteristics of a power transmission line including a power cable actually laid in the field.

[0015] Therefore, after extensive research, the inventors developed a power transmission line evaluation system that can evaluate the charge quantity characteristics of a power transmission line by directly applying a voltage to the power transmission line actually laid on-site.

[0016] However, it has been found that the above-mentioned power transmission line evaluation system gives rise to new problems, such as those described below, due to the circuit configuration and the like.

[0017] (i) In the above-mentioned conventional insulating material evaluation system 90, the charge amount measuring unit 930 was placed closer to the earth than the sheet 910 to be evaluated. As a result, the measurement computer was directly connected to the measurement system including the capacitor 932 as the charge amount measuring unit 930. The insulating material evaluation system 90 having such a configuration was installed in an environment such as a laboratory where the level of noise generated from the earth can be easily controlled. As a result, there was no malfunction in the measurement computer.

[0018] However, in the power transmission line evaluation system that applies an ultra-high voltage to the power transmission line, tests were conducted in various indoor and outdoor environments. For this reason, there was a tendency for the noise level from the earth of a factory or the like outside the power transmission line evaluation system to be high. In particular, when various power sources (such as inverter control power sources) in the factory were located near the power transmission line, the noise level was likely to be high. In such a case, when the charge amount measuring unit was located closer to the earth than the transmission line to be evaluated, noise was likely to be generated from the earth, and there was a risk that the noise would affect the measurement accuracy of the charge amount measuring unit.

[0019] In addition, in a power transmission line evaluation system in which the charge measurement unit is located closer to the earth than the power transmission line, the reference potential of the power transmission line is in a floating state via the charge measurement unit, which may cause the grounding of the power transmission line to become unstable.

[0020] Furthermore, in a power transmission line evaluation system in which the charge measurement unit is located closer to the earth than the power transmission line, if an electrical malfunction occurs in the charge measurement unit, the grounding system for the power transmission line may change. This may cause an unexpected current to flow or an unexpected voltage to be applied to the power transmission line. As a result, the electrical malfunction may affect the entire power transmission line evaluation system to which high voltage is applied.

[0021] (ii) In order to avoid the effect of (i) above, the inventors considered a configuration in which the charge amount measuring unit is placed at a position close to the positive electrode of the power supply where the charge amount measuring unit is at a high potential. In this case, since the charge amount measuring unit is at a high potential, it is not possible to directly connect a measurement computer to a measurement system including a capacitor as the charge amount measuring unit. Therefore, a wireless unit that wirelessly transmits the charge amount data measured by the charge amount measuring unit is provided in the power transmission line evaluation system.

[0022] However, when the voltage applied from the power source to the transmission line was gradually increased, for example when the applied voltage exceeded 400 kV, communication from the radio section of the transmission line evaluation system was cut off.

[0023] When the inventors investigated the cause, they found that the housing containing the charge amount measuring unit and the radio unit had a high potential equal to the positive pole of the power supply as a reference potential. On the other hand, for example, in the antenna of the radio unit having a coaxial structure, the second conductor that electrically shields the radio unit has the same potential as the housing, but the first conductor located at the center of the antenna is not directly electrically connected to the housing. For this reason, unintended excessive charges were accumulated in the first conductor of the antenna. As a result, it is believed that a communication failure occurred in the radio unit. Therefore, even with the arrangement as in (ii), it was difficult to stably obtain charge amount data.

[0024] As a result of further intensive research to solve the above-mentioned new problems (i) and (ii), the inventors discovered a configuration for a power transmission line evaluation system that can stably evaluate the state of a power transmission line.

[0025] The present disclosure is based on the above findings of the inventors.

[0026] <Embodiments of the present disclosure> Next, embodiments of the present disclosure will be listed and described.

[0027] [1] A power transmission line evaluation system according to an embodiment of the present disclosure includes: a power source connected to a power transmission line including a power cable having a conductor, an insulating layer, and a shielding layer in this order in a radial direction of the conductor, and capable of applying a voltage between the conductor and the shielding layer; a charge amount measuring unit connected in series between the power source and the power transmission line, for measuring an amount of charge that is an integral value of a current flowing between the conductor and the shielding layer of the power transmission line; Equipped with. According to this configuration, the state of the power transmission line can be evaluated based on the charge amount characteristics of the power transmission line.

[0028] [2] In the power transmission line evaluation system according to the above [1], The power supply is configured to be capable of applying a DC voltage or a square wave voltage of 10 kV or more between the conductor and the shielding layer of the power transmission line. According to this configuration, the amount of charge in the power transmission line can be measured under conditions close to those during actual operation of the power transmission line.

[0029] [3] In the power transmission line evaluation system according to [1] or [2] above, The power source includes: A positive electrode connected to the conductor of the power transmission line; a negative electrode that is grounded to earth together with the shielding layer of the power transmission line; having The charge amount measuring unit is connected in series between the positive electrode of the power source and the conductor of the power transmission line. According to this configuration, the state of the power transmission line can be stably evaluated.

[0030] [4] In the power transmission line evaluation system according to [3] above, The device further includes a wireless unit connected to the charge amount measuring unit and capable of wirelessly transmitting charge amount data measured by the charge amount measuring unit to an external device. According to this configuration, the charge amount data can be obtained wirelessly, stably, and safely.

[0031] [5] In the power transmission line evaluation system according to [4] above, a housing that houses the charge amount measuring unit and a part of the radio unit and is connected to the charge amount measuring unit and the radio unit as a common reference potential; The housing is connected between the positive electrode of the power supply and the charge amount measuring unit, and is configured to be at the same potential as the positive electrode of the power supply. According to this configuration, the charge amount measuring unit can accurately measure the amount of charge between the conductor and the shielding layer of the power transmission line.

[0032] [6] In the power transmission line evaluation system according to [5] above, The wireless unit includes: a signal processing unit connected to the charge amount measuring unit within the housing, for generating a data signal including the charge amount data and processing a signal from an external source; an antenna connected to the signal processing unit, for transmitting the data signal to an external device and receiving the signal from an external device; a coil connected to the housing as the reference potential and connected in parallel to the signal processing unit and the antenna; has. According to this configuration, the state of the power transmission line can be stably evaluated.

[0033] [7] A power transmission line evaluation method according to another aspect of the present disclosure includes: preparing a power transmission line including a power cable having a conductor, an insulating layer, and a shielding layer in this order in a radial direction of the conductor; applying a voltage between the conductor and the shielding layer using a power source connected to the power transmission line; measuring an amount of charge, which is an integral value of a current flowing between the conductor and the shielding layer of the power transmission line, using a charge amount measuring unit connected in series between the power source and the power transmission line; Equipped with. According to this configuration, the state of the power transmission line can be evaluated based on the charge amount characteristics of the power transmission line.

[0034] [Details of the embodiment of the present disclosure] Next, one embodiment of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims. At least a part of the embodiments described below may be arbitrarily combined.

[0035] <One embodiment of the present disclosure> (1) Power transmission line evaluation system An outline of a power transmission line evaluation system 20 according to an embodiment of the present disclosure will be described with reference to Fig. 1 to Fig. 4. In Fig. 1, a switching system of a power source 200 and an electric charge measuring unit 300, and a low-voltage shield ring 194 are omitted. In Fig. 1, a bent portion of the power transmission line 10 is omitted, and the power transmission line 10 is shown in a straight line. A part constituting the power transmission line 10 in Fig. 2 is shown in cross section.

[0036] As shown in Figures 1 to 4, the power transmission line evaluation system 20 of this embodiment is configured to evaluate the state of the power transmission line 10 based on the amount of charge of the actually laid power transmission line 10, for example, by a current integration charge method.

[0037] Specifically, the power transmission line evaluation system 20 of the present embodiment includes, for example, a power source 200, a charge amount measuring unit 300, a wireless unit 400, a housing 500, and a management center 60.

[0038] (Power lines) 1 and 2, in this embodiment, a power transmission line 10 to be evaluated includes, for example, at least a power cable 100. The power cable 100 has, for example, a conductor 101, an inner semiconductive layer (not shown), an insulating layer 103, an outer semiconductive layer (not shown), a shielding layer (metallic shielding layer) 105, and a sheath (reference number not shown) in this order from the central axis of the conductor 101 toward the outside in the radial direction of the conductor 101.

[0039] The power cable 100 may be configured for DC or AC. Even if the power cable 100 is configured for AC, a DC voltage or a square wave voltage is applied from the power source 200 of the power transmission line evaluation system 20 to the power transmission line 10 including the power cable 100.

[0040] In the present embodiment, the power transmission line 10 may further include at least one of a terminal connection portion 120 and an intermediate connection portion 140, for example.

[0041] The intermediate connection part 140 constitutes, for example, a portion where a pair of power cables 100 are connected in the power transmission line 10. Specific examples of the intermediate connection part 140 include an intermediate connection part including a cold-shrinkable rubber insulating unit, and a factory joint (FJ) formed by wrapping insulating tape around the intermediate connection part 140 in a factory. The intermediate connection part 140 includes, for example, a metal sleeve that connects the conductors 101 of the pair of power cables 100, an insulating unit that surrounds the outer periphery of the metal sleeve, and a shielding member that is connected to the shielding layer 105 of the power cable 100.

[0042] The termination connection part 120 constitutes, for example, a part where the power cable 100 is connected to an overhead transmission line or a predetermined device in the power transmission line 10. A specific example of the termination connection part 120 is an outdoor termination connection part. In the following, for example, a case where the termination connection part 120 is configured as an outdoor termination connection part will be described.

[0043] At the termination connection part 120, the power cable 100 is peeled off stepwise from the axial tip of the conductor 101 toward the opposite side. That is, the conductor 101, the insulating layer 103, the outer semiconductive layer, the shielding layer 105, and the sheath of the power cable 100 are exposed in this order from the tip side of the conductor 110 toward the opposite side. An insulating rubber unit may be provided around the exposed outer semiconductive layer of the power cable 100.

[0044] The terminal connection portion 120 includes, for example, a porcelain tube 122 and a lower metal fitting 124 .

[0045] The porcelain tube 122 is configured as a cylindrical insulating member, and is provided so as to surround the outer periphery of the power cable 100. The porcelain tube 122 is configured so as to ensure insulation around the power cable 100 that is peeled off in stages.

[0046] The porcelain tube 122 is erected in the vertical direction. The power cable 100, which has been stripped in stages, is inserted into the porcelain tube 122. The conductor 101 of the power cable 100 is fixed to the upper part of the porcelain tube 122. The inside of the porcelain tube 122 excluding the power cable 100 is filled with an insulating medium (reference number not shown) such as insulating oil or insulating gas.

[0047] The porcelain tube 122 has a plurality of flanges (folds, not shown) on the outer periphery of the porcelain tube 122, the diameter of which increases toward the outside of the porcelain tube 122. This ensures an insulation distance between the conductor 101 and the earth.

[0048] The lower fitting 124 is provided at the axial lower part of the porcelain tube 122 and closes an opening at the axial lower part of the porcelain tube 122. The lower fitting 124 is connected to the shielding layer 105 of the power cable 100 and is grounded together with the shielding layer 105. As a result, the shielding layer 105 in the entire power transmission line 10 is grounded.

[0049] The power transmission line 10 has a first end 10a in the axial direction of the conductor 101 (the direction in which the power transmission line 10 is laid), and a second end 10b opposite to the first end 10a. The above-mentioned termination connection parts 120 are provided near the first end 10a and the second end 10b of the power transmission line 10, respectively.

[0050] A high-voltage shield ring 192 is provided at each of the first end 10a and the second end 10b of the power transmission line 10 so as to surround the tip of the conductor 101. Two high-voltage shield rings 192 may be provided at each of the first end 10a and the second end 10b of the power transmission line 10. This makes it possible to suppress electric field concentration near the tip of the conductor 101 during measurement.

[0051] Furthermore, a low-voltage shield ring 194 may be provided to each of the pair of termination connection portions 120 of the power transmission line 10 so as to surround the lower metal fitting 124. This makes it possible to suppress electric field concentration near the lower metal fitting 124 during measurement.

[0052] In the power transmission line evaluation system 20 of the present embodiment, a first axial end 10a of a conductor 101 of a power transmission line 10 is connected to a positive electrode 202 of a power source 200 via a charge amount measuring unit 300, as described below. This causes a high voltage to be applied to the conductor 101 of the power transmission line 10 by the power source 200.

[0053] On the other hand, a second axial end 10b of the conductor 101 of the power transmission line 10 is open.

[0054] In this disclosure, also in the above-mentioned terminal connection part 120 and intermediate connection part 140, the metal member connected to the conductor 101 of the power cable 100, the insulating member having insulating properties similar to the insulating layer 103 of the power cable 100, and the shielding member connected to the shielding layer 105 of the power cable 100 are described as the “conductor 101,” the “insulating layer 103,” and the “shielding layer 105,” respectively, as in the power cable 100.

[0055] (power supply) The power supply 200 is, for example, connected to the above-mentioned power transmission line 10 and configured to be able to apply a voltage between the conductor 101 and the shielding layer 105 of the power transmission line 10.

[0056] Specifically, the power source 200 has, for example, a positive electrode (+ electrode, high voltage electrode) 202 and a negative electrode (- electrode, ground electrode) 204. The positive electrode 202 of the power source 200 is connected, for example, to the conductor 101 of the power transmission line 10 (via the charge amount measuring unit 300 described later). The positive electrode 202 is connected to the conductor 101, for example, at a position close to the first end 10a of the power transmission line 10. On the other hand, the negative electrode 204 of the power source 200 is grounded to earth together with, for example, the shielding layer 105 of the power transmission line 10. With this configuration, the power source 200 is configured to be able to apply a voltage between the conductor 101 and the shielding layer 105 of the power transmission line 10.

[0057] The power source 200 is configured to be able to apply, for example, a voltage equivalent to the voltage applied to the transmission line 10 during actual operation of the transmission line 10 between the conductor 101 and the shielding layer 105 of the transmission line 10 to be evaluated. Specifically, the power source 200 is configured to be able to apply, for example, a DC voltage or a square wave voltage of 10 kV or more, 100 kV or more, or 400 kV or more between the conductor 101 and the shielding layer 105 of the transmission line 10. The "square wave voltage" here means, for example, a square wave voltage having a first voltage of 0 V or more and a second voltage that is a positive voltage higher than the first voltage. Furthermore, the power source 200 is configured to be able to gradually increase the voltage from 0 V to the above-mentioned upper limit voltage that can be applied.

[0058] (Charge amount measurement section) The electric charge measuring unit (Q(t) meter) 300 is connected in series, for example, between the power source 200 and the power transmission line 10. The electric charge measuring unit 300 is configured to measure an electric charge Q(t) which is an integral value of a current I(t) flowing between the conductor 101 and the shielding layer 105 of the power transmission line 10 (i.e., the insulating layer 103 of the power transmission line 10 when the power transmission line 10 is normal).

[0059] Specifically, the charge amount measuring unit 300 includes, for example, a capacitor 320 and a voltmeter (not shown). The capacitor 320 is, for example, connected in series between the power source 200 and the power transmission line 10, and configured to accumulate a charge flowing between the conductor 101 and the shielding layer 105 of the power transmission line 10. The voltmeter is, for example, configured to measure (continuously at a predetermined time interval) the voltage between both electrodes of the capacitor 320 transmitted from the buffer circuit. Note that an operational amplifier (not shown) that transmits the voltage between both electrodes of the capacitor 320 to the voltmeter may be provided between the capacitor 320 and the voltmeter. When the known capacitance of the above-mentioned capacitor 320 is C and the voltage between both electrodes of the capacitor 320 measured by the voltmeter is V, the capacitor 320 satisfies Q(t)=CV. The charge amount Q(t), which is the integral value of the current I(t) flowing between the conductor 101 and the shielding layer 105 of the power transmission line 10, can be obtained by this formula.

[0060] Hereinafter, information relating to the charge amount Q(t) determined by the charge amount measuring section 300 will also be referred to as "charge amount data".

[0061] In this embodiment, the electric charge measuring unit 300 is connected in series, for example, between the positive electrode 202 of the power source 200 and the conductor 101 of the power transmission line 10. That is, the electric charge measuring unit 300 is disposed in the power transmission line evaluation system 20 at a position closer to the positive electrode 202 of the power source 200 than the power transmission line 10 and at a position at which the electric charge is at a high potential.

[0062] (Radio Division) The wireless unit 400 is configured to be able to wirelessly transmit and receive various signals.

[0063] In this embodiment, the wireless unit 400 is configured to be connected to the charge amount measuring unit 300, for example, and to be capable of wirelessly transmitting charge amount data measured by the charge amount measuring unit 300 to the outside. As a result, even if the charge amount measuring unit 300 is placed at a position close to the positive electrode 202 of the power source 200 and at a high potential, the charge amount data from the charge amount measuring unit 300 can be stably acquired by the management center 60 described later through wireless communication of the wireless unit 400.

[0064] A specific wireless communication method by the wireless unit 400 is not particularly limited. However, the wireless communication method by the wireless unit 400 may be, for example, a short-distance wireless method of the ZigBee (registered trademark) standard. The frequency band of the wireless communication by the wireless unit 400 may be, for example, the 2.4 GHz band.

[0065] The radio section 400 will be described in detail later.

[0066] (others) In addition, a battery (not shown) for driving the charge amount measuring section 300 and the wireless section 400, and a recording section (not shown) for storing charge amount data may be provided near the charge amount measuring section 300.

[0067] (Housing) The housing 500 is configured as, for example, a metal container, and houses the charge amount measuring unit 300 and part of the wireless unit 400. The housing 500 is connected to, for example, the charge amount measuring unit 300 and the wireless unit 400 as a common reference potential (frame ground).

[0068] The housing 500 is connected, for example, between the positive electrode 202 of the power source 200 and the charge amount measuring unit 300, and is at the same potential as the positive electrode 202 of the power source 200. On the other hand, the housing 500 is not connected between the charge amount measuring unit 300 and the conductor 101 of the power transmission line 10 to be evaluated. With this configuration, it is possible to suppress superposition of a charge amount component based on a floating electrostatic capacitance generated between the housing 500 and the earth in the measurement result of the charge amount measured by the charge amount measuring unit 300.

[0069] (Management Center) 1 and 4, the management center 60 is provided, for example, at a location away from the power transmission line 10, and is configured to manage each part of the power transmission line evaluation system 20 and the power transmission line 10 to be evaluated. In this embodiment, the management center 60 may be provided, for example, near the power source 200.

[0070] The management center 60 is configured to, for example, control the power source 200 and also to control the charge amount measuring unit 300 and the wireless unit 400 through wireless communication with the wireless unit 400 .

[0071] Furthermore, the management center 60 is configured to, for example, receive a data signal from the wireless unit 400 and evaluate the state of the power transmission line 10 based on the charge amount data obtained from the data signal.

[0072] Specifically, as shown in FIG. 4, the management center 60 includes, for example, a control unit 620 and a center radio unit 640.

[0073] The control unit 620 is configured as a general-purpose computer, and has, for example, a CPU (Central Processing Unit) 622, a RAM (Random Access Memory) 624, a storage device 626, and an I / O port 628. The RAM 624, the storage device 626, and the I / O port 628 are configured to be able to exchange data with the CPU 622. The I / O port 628 is connected (by wiring) to, for example, a center radio unit 640 and a power source 200.

[0074] The storage device 626 is configured to store, for example, a power transmission line evaluation program, charge amount data, etc. The storage device 626 is, for example, a hard disk drive (HDD) or a solid state drive (SSD).

[0075] The RAM 624 is configured to temporarily store programs, information, etc. that are read from the storage device 626 by the CPU 622 .

[0076] The CPU 622 is configured to execute a predetermined program stored in the storage device 626, thereby executing, for example, each process in a power transmission line evaluation method described later. The power transmission line evaluation method will be described in detail later.

[0077] The predetermined program for executing each process by the control unit 620 described above is used, for example, by installing it in a computer configured by the control unit 620. The program may be provided, for example, by being stored in a non-transitory computer-readable storage medium prior to installation. Alternatively, the program may be provided to the computer via the center radio unit 640, for example.

[0078] The center wireless unit 640 is configured to transmit and receive predetermined information or signals between the wireless unit 400 and itself, for example, by wireless communication conforming to the wireless communication method of the wireless unit 400. Specifically, the center wireless unit 640 can control the charge amount measuring unit 300 and the wireless unit 400 by wirelessly transmitting various signals from the control unit 620 to the wireless unit 400. In addition, the center wireless unit 640 can obtain the charge amount data by wirelessly receiving a data signal including the charge amount data from the wireless unit 400.

[0079] (2) Radio section configuration The configuration of the wireless unit 400 of this embodiment will be described with reference to Figures 1 and 3. In Figure 3, a cross-sectional view of the antenna 440 is shown.

[0080] As shown in FIGS. 1 and 3, the wireless unit 400 of this embodiment includes a signal processing unit 420, an antenna 440, and a coil 460, for example.

[0081] (Signal Processing Unit) The signal processing unit 420 is connected to the electric charge amount measuring unit 300, for example, inside the housing 500. The signal processing unit 420 is configured to generate a data signal including the electric charge amount data obtained by the electric charge amount measuring unit 300, and to supply the data signal to an antenna 440 described later.

[0082] On the other hand, the signal processing unit 420 is configured to process, for example, an external signal. Specifically, the signal processing unit 420 is configured to transmit the signal from the management center 60 to the charge amount measuring unit 300 and to execute a predetermined process based on the signal from the management center 60 when the signal is received from the management center 60 via an antenna 440 described later.

[0083] (antenna) The antenna 440 is, for example, connected to the signal processing unit 420, and configured to transmit a data signal generated by the signal processing unit 420 to the outside and to receive a signal from the outside.

[0084] In this embodiment, the antenna 440 is configured as, for example, a so-called sleeve antenna. Specifically, the antenna 440 has, for example, a first conductor (center conductor) 441, an antenna insulating layer 442, a second conductor (outer conductor) 443, and an antenna sheath (protective layer) 444.

[0085] The first conductor 441 is configured as, for example, a metal wire and is connected to the signal processing unit 420. The antenna insulating layer 442 includes, for example, an insulating material and is provided so as to surround the outer periphery of the first conductor 441. The second conductor 443 is configured as, for example, a metal layer such as a metal mesh, is separated from the first conductor 441 via the antenna insulating layer 442, and is provided so as to surround the outer periphery of the antenna insulating layer 442. The second conductor 443 is connected to, for example, the housing 500 which serves as a reference potential. The antenna sheath 444 includes, for example, an insulating material and is provided so as to surround a part of the outer periphery of the second conductor 443.

[0086] Here, a part of the first conductor 441 is exposed to the outside, for example, from an end of the antenna sheath 444 in the axial direction of the first conductor 441. On the other hand, the second conductor 443 is folded back at an end of the antenna sheath 444 in the axial direction of the first conductor 441. As a result, a part of the second conductor 443 is exposed outside the antenna sheath 444. The exposed length of the first conductor 441 from the antenna sheath 444 is, for example, λ / 4, where λ is the wavelength of the signal generated by the signal processing unit 420.

[0087] The data signal generated by the signal processing unit 420 can be transmitted to the outside by the first conductor 441 and the second conductor 443 of the antenna 440 having the above configuration.

[0088] (coil) The wireless unit 400 of this embodiment further includes a coil (inductor, reactor) 460, for example.

[0089] Here, in the power transmission line evaluation system 20 of this embodiment, as described above, the housing 500 that houses the charge amount measuring unit 300 and the wireless unit 400 has a potential equivalent to that of the positive electrode 202 of the power source 200 as a reference potential.

[0090] Under this circumstance, charge amount measuring section 300 measures the voltage (potential difference) between both electrodes caused by the accumulation of charge in capacitor 320. Therefore, even if one electrode of capacitor 320 and casing 500 are at a high potential, the potential difference between both electrodes of capacitor 320 is smaller than the applied voltage of power source 200, so there is no problem in measuring the amount of charge accumulated in capacitor 320.

[0091] On the other hand, as described above, antenna 440 of wireless unit 400 operates like a capacitor by having first conductor 441 and second conductor 443. In antenna 440, second conductor 443 connected to housing 500 has a high potential as a reference potential, while first conductor 441 may be in a floating state where the potential is not fixed. As a result, there is a possibility that unintended excess charge may accumulate in first conductor 441 and second conductor 443 of antenna 440.

[0092] Therefore, in this embodiment, the coil 460 is connected to the housing 500 as a reference potential, and is connected in parallel to the signal processing unit 420 and the antenna 440. That is, the coil 460 is connected to the first conductor 441 of the antenna 440 connected to the signal processing unit 420, and the second conductor 443 of the antenna 440 connected to the housing 500.

[0093] When a DC voltage or a square wave voltage is applied from the power source 200, the frequency is zero or low, so that the impedance in the coil 460 is low. This causes no potential difference to occur between the first conductor 441 and the second conductor 443 of the antenna 440. As a result, unintended accumulation of excess charge in the first conductor 441 and the second conductor 443 of the antenna 440 can be suppressed.

[0094] On the other hand, when the antenna 440 transmits and receives a signal, the frequency is high according to the wireless communication standard, and therefore the impedance in the coil 460 is high. This makes it possible to consider that the first conductor 441 and the second conductor 443 of the antenna 440 are electrically insulated. As a result, the antenna 440 can stably transmit and receive signals.

[0095] (3) Transmission line evaluation method Next, the power transmission line evaluation method of the present embodiment will be described with reference to FIGS.

[0096] 5, the power transmission line evaluation method of the present embodiment includes, for example, a power transmission line preparation step S100, a system construction step S200, a voltage application step S300, a charge amount measurement step S400, a data communication step S500, and an evaluation step S600. The power transmission line evaluation method of the present embodiment may be considered as a method of using a charge amount measurement device (Q(t) meter). Hereinafter, the operation of each part of the power transmission line evaluation system 20 is controlled by a control unit 620 of a management center 60.

[0097] (S100: Power transmission line preparation process) First, prepare the power transmission line 10 including the power cable 100. At this time, the power transmission line 10 may be prepared, for example, in a state in which it will actually be laid on site, or in a state close to that.

[0098] (S200: System construction process) After the power transmission line 10 is prepared, a power transmission line evaluation system 20 including a power source 200, a charge amount measuring unit 300, a wireless unit 400, and a housing 500 is constructed.

[0099] At this time, in this embodiment, the charge amount measuring unit 300 is connected in series between the positive electrode 202 of the power source 200 and the conductor 101 of the power transmission line 10.

[0100] At this time, in this embodiment, the charge amount measuring unit 300 and a part of the wireless unit 400 are housed in the housing 500. The housing 500 is connected to the charge amount measuring unit 300 and the wireless unit 400 as a common reference potential. Furthermore, the housing 500 is connected between the positive electrode 202 of the power source 200 and the charge amount measuring unit 300, so that the housing 500 and the positive electrode 202 of the power source 200 are at the same potential.

[0101] Furthermore, at this time, in this embodiment, coil 460 of wireless unit 400 is connected to housing 500 as a reference potential, and is also connected in parallel to signal processing unit 420 and antenna 440.

[0102] (S300 and S400: voltage application process and charge amount measurement process) After the system construction step S200 is completed, the voltage application step S300 and the charge amount measurement step S400 are performed simultaneously or consecutively.

[0103] The power source 200 is controlled by the management center 60 to apply a voltage V(t) between the conductor 101 and the shielding layer 105 of the power transmission line 10 using the power source 200 connected to the power transmission line 10 .

[0104] At the same time as or immediately after the start of voltage application by the power source 200, a control signal for controlling the charge amount measuring unit 300 is transmitted from the management center 60 to the wireless unit 400. As a result, the charge amount measuring unit 300 connected in series between the power source 200 and the power transmission line 10 measures the charge amount Q(t), which is the integral value of the current I(t) flowing between the conductor 101 and the shielding layer 105 of the power transmission line 10.

[0105] Now, with reference to FIG. 6, an example of measuring the charge amount Q(t) will be described.

[0106] As shown in FIG. 6, for example, a square wave voltage V(t) is applied between the conductor 101 and the shielding layer 105 of the power transmission line 10.

[0107] When a square wave voltage V(t) is applied, a current I(t) calculated by the following equation (1) flows between the conductor 101 and the shielding layer 105 of the power transmission line 10. I(t)=Idisp(t)+Iabs(t)+Icond(t) ···(1) Where: Idisp(t) is the instantaneous charging current immediately after application of the square wave voltage V(t). Iabs(t) is the absorbed current associated with the accumulation and movement of space charge between the conductor 101 and the shielding layer 105 of the power transmission line 10. Icond(t) is the conduction current (leakage current) flowing between the conductor 101 and the shielding layer 105 of the power transmission line 10.

[0108] In the charge amount measuring unit 300, the capacitor 320 accumulates the charge flowing between the conductor 101 and the shielding layer 105 of the power transmission line 10. The voltmeter of the charge amount measuring unit 300 measures the voltage between both electrodes of the capacitor 320 transmitted from the buffer circuit. As a result, the charge amount Q(t), which is the integral value of the current I(t) flowing between the conductor 101 and the shielding layer 105 of the power transmission line 10, can be calculated by the following equation (2).

[0109]

number

[0110] Where: Qdisp(t) is the charge (electrode charge) due to the instantaneous charging current, and is calculated as the charge Q(0) at t = 0. Qabs(t) and Qcond(t) are the absorbed and conducted charges, respectively.

[0111] In this way, the charge amount measuring unit 300 can obtain the charge amount Q(t), which is the integral value obtained by integrating the current I(t) after the rise of the square wave voltage V(t). Furthermore, by continuously measuring the charge amount Q(t) at a predetermined time interval using the charge amount measuring unit 300, it is possible to obtain information on the change over time of the charge amount Q(t). The charge amount data, which is information on the charge amount Q(t), is used in the evaluation step S600 described later.

[0112] Once the charge amount data has been obtained in this manner, the voltage application by the power supply 200 and the measurement of the charge amount by the charge amount measuring unit 300 are terminated.

[0113] (S500: Data communication process) The data communication step S500 is performed at a timing when the charge amount data becomes necessary in the management center 60. For example, the data communication step S500 may be performed after the voltage application step S300 and the charge amount measurement step S400 are completed. Alternatively, for example, the data communication step S500 may be performed in real time while the voltage application step S300 and the charge amount measurement step S400 are being performed.

[0114] The data communication step S500 of this embodiment includes, for example, a request signal transmission / reception step S520 and a data transmission / reception step S540.

[0115] (S520: Request signal transmission / reception process) When the management center 60 requires the charge amount data, it transmits a request signal to the wireless unit 400. The wireless unit 400 receives the request signal from the management center 60 via the antenna 440.

[0116] (S540: Data transmission and reception process) When the wireless unit 400 receives a request signal from the management center 60 via the antenna 440, the signal processing unit 420 of the wireless unit 400 generates a data signal including the charge amount data measured by the charge amount measuring unit 300. After the data signal is generated, the data signal is transmitted to the management center 60 via the antenna 440 of the wireless unit 400.

[0117] The management center 60 receives the data signal from the wireless unit 400 via the center wireless unit 640. As a result, the management center 60 acquires the data signal including the charge amount data.

[0118] (S600: Evaluation process) When the management center 60 receives the data signal from the wireless unit 400, the management center 60 evaluates the state of the power transmission line 10 based on the charge amount data obtained from the data signal.

[0119] At this time, in this embodiment, the charge Qdisp(t)=Q(0) at the start of application of the square wave voltage V(t) (t=0) is calculated as shown in Fig. 6. In this way, in the current integral charge method, Q(0) can be clearly calculated as the initial value of the charge Q(t).

[0120] At this time, in this embodiment, the charge Q(tm) after the time tm from the start of application of the square wave voltage V(t) t=0 is calculated. Furthermore, the charge ratio Rc (=Q(tm) / Q(0)) of the charge Q(tm) after the time tm has elapsed to the charge Q(0) as the initial value is calculated. The charge ratio Rc allows the change over time of the charge Q(t) to be quantitatively evaluated.

[0121] The management center 60 evaluates the state of the power transmission line 10 based on at least one of the initial charge amount Q(0), the charge amount Q(tm) after the lapse of time tm, and the charge amount ratio Rc obtained as described above.

[0122] This completes the evaluation of the power transmission line 10 of this embodiment.

[0123] (4) Summary of this embodiment According to this embodiment, one or more of the following advantages are achieved.

[0124] (a) In the power transmission line evaluation system 20 of the present embodiment, a power source 200 connected to the power transmission line 10 is configured to be able to apply a voltage between the conductor 101 and the shielding layer 105 of the power transmission line 10. Furthermore, the charge amount measuring unit 300 is connected in series between the power source 200 and the power transmission line 10, and is configured to measure a charge amount Q(t) which is an integral value of a current I(t) flowing between the conductor 101 and the shielding layer 105 of the power transmission line 10. Such a power transmission line evaluation system 20 can evaluate the charge amount characteristics of the power transmission line 10 including the power cable 100 actually laid at the site. This makes it possible to evaluate the state of the power transmission line 10 based on the charge amount characteristics of the power transmission line 10.

[0125] (b) In this embodiment, the power supply is configured to be capable of applying a DC voltage or a square wave voltage of 10 kV or more between the conductor 101 and the shielding layer 105 of the transmission line 10. This makes it possible to measure the amount of charge Q(t) of the transmission line 10 under conditions similar to those during the actual operation of the transmission line 10. As a result, it becomes possible to find out in advance, based on the amount of charge Q(t) of the transmission line 10, any malfunction of the transmission line 10 that may occur during the operation of the transmission line 10.

[0126] (c) In this embodiment, the electric charge measuring unit 300 is connected in series between the positive electrode 202 of the power source 200 and the conductor 101 of the power transmission line 10. In other words, the electric charge measuring unit 300 is not disposed at a position closer to the earth than the power transmission line 10 to be evaluated, but is disposed at a position closer to the positive electrode 202 of the power source 200 than the power transmission line 10 and at a high potential.

[0127] The above-described arrangement of the electric charge measuring unit 300 makes it possible to suppress the propagation of noise from the earth to the electric charge measuring unit 300 even in a situation where the noise level from the earth is high, such as in a factory outside the power transmission line evaluation system 20. This makes it possible to suppress a decrease in the measurement accuracy of the electric charge measuring unit 300 caused by noise from the earth.

[0128] The above-mentioned arrangement of the charge amount measuring unit 300 allows the shielding layer 105 of the power transmission line 10 to be reliably grounded to earth. This makes it possible to prevent the reference potential of the power transmission line 10 from being in a floating state. In other words, it becomes possible to stabilize the grounding of the power transmission line 10.

[0129] Furthermore, due to the above-mentioned arrangement of the electric charge measurement unit 300, even if an electrical malfunction occurs in the electric charge measurement unit 300, it is possible to suppress a change in the ground system for the power transmission line 10. This makes it possible to suppress an unexpected current from flowing through the power transmission line 10 or an unexpected voltage from being applied thereto. As a result, it is possible to suppress the influence of an electrical malfunction on the entire power transmission line evaluation system 20.

[0130] In this way, the power transmission line evaluation system 20 makes it possible to stably evaluate the state of the power transmission line 10.

[0131] (d) In this embodiment, the power transmission line evaluation system 20 further includes a wireless unit 400 capable of wirelessly transmitting the charge amount data measured by the charge amount measurement unit 300 to the outside. As a result, even if the charge amount measurement unit 300 is placed at a position close to the positive electrode 202 of the power source 200 and at a high potential, the charge amount data can be obtained wirelessly in a stable and safe manner.

[0132] (e) In this embodiment, the housing 500 housing the charge amount measuring unit 300 and part of the wireless unit 400 is connected between the positive terminal 202 of the power source 200 and the charge amount measuring unit 300, and is at the same potential as the positive terminal 202 of the power source 200.

[0133] Here, in a situation where the metallic housing 500 is not grounded to the earth, floating electrostatic capacitance may occur between the housing 500 and the earth. For example, when the housing 500 is connected between the charge amount measuring unit 300 and the conductor 101 of the power transmission line 10, the capacitor formed by the conductor 101 and the shielding layer 105 of the power transmission line 10 to be evaluated and the floating capacitor formed by the housing 500 and the earth are in a state of being paralleled at a position closer to the earth than the charge amount measuring unit 300. Therefore, the measurement result by the charge amount measuring unit 300 includes not only the charge amount component based on the electrostatic capacitance generated between the conductor 101 and the shielding layer 105 of the power transmission line 10 to be evaluated, but also the charge amount component based on the floating electrostatic capacitance generated between the housing 500 and the earth. As a result, the accuracy of the measurement of the charge amount of the power transmission line 10 by the charge amount measuring unit 300 may be reduced.

[0134] In contrast, in this embodiment, since the housing 500 is connected between the positive electrode 202 of the power source 200 and the charge amount measuring unit 300, it is possible to arrange a state in which only a capacitor formed by the conductor 101 and the shielding layer 105 of the transmission line 10 to be evaluated is arranged at a position closer to the earth than the charge amount measuring unit 300. This makes it possible to suppress superposition of a charge amount component based on a floating electrostatic capacitance generated between the housing 500 and the earth in the measurement result of the charge amount measured by the charge amount measuring unit 300. As a result, it is possible to suppress a decrease in the measurement accuracy of the charge amount of the transmission line 10 by the charge amount measuring unit 300.

[0135] (f) In this embodiment, the housing 500 housing the charge amount measuring unit 300 and a part of the wireless unit 400 has a common reference potential that is equipotential with the positive electrode 202 of the power source 200. Under such circumstances, the coil 460 of the wireless unit 400 is connected to the housing 500 as the reference potential, and is also connected in parallel to the signal processing unit 420 and the antenna 440.

[0136] When a DC voltage or a square wave voltage is applied from the power source 200, as described above, the impedance in the coil 460 is low. This makes it possible to suppress unintended accumulation of excess charge in the antenna 440. As a result, it becomes possible to suppress the occurrence of wireless communication failures caused by charge accumulation in the antenna 440 of the wireless unit 400.

[0137] On the other hand, as described above, when transmitting and receiving a signal by the antenna 440, the impedance in the coil 460 becomes high. This allows stable transmission and reception of signals between the antenna 440 of the wireless unit 400 and the management center 60.

[0138] In this manner, by stably performing wireless communication using the wireless unit 400 having the coil 460, it becomes possible to stably evaluate the state of the power transmission line 10.

[0139] <Other embodiments of the present disclosure> Although the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit and scope of the present disclosure.

[0140] In the above embodiment, the case where the management center 60 is connected by wiring from the I / O port 628 to the power source 200 and configured to control the power source 200 has been described, but the present disclosure is not limited to this case. The management center 60 may be configured to control the power source 200 by wireless communication using the center wireless unit 640.

[0141] In the above embodiment, a case has been described in which the management center 60 is configured to control the power source 200 and also to control the charge amount measuring unit 300 and the wireless unit 400 through wireless communication with the wireless unit 400, but the present disclosure is not limited to this case. The management center 60 may, for example, separately have a power source control unit that controls the power source 200 and a measurement system control unit that controls the charge amount measuring unit 300 and the wireless unit 400 through wireless communication with the wireless unit 400.

[0142] In the above embodiment, the antenna 440 is configured as a sleeve antenna, but the present disclosure is not limited to this. The antenna 440 may be configured as, for example, a dipole antenna.

[0143] In the above embodiment, a case has been described in which a square wave voltage is applied to the power transmission line 10 and the charge amount measurement step S400 is performed to measure the charge amount of the power transmission line 10, but the present disclosure is not limited to this case. In the voltage application step S300 and the charge amount measurement step S400, the charge amount of the power transmission line 10 may be measured while increasing the DC voltage applied to the power transmission line 10 in a stepwise manner.

[0144] <Additional Notes> The following appended notes are related to aspects of the present disclosure. The appended notes are related to aspects described in the section entitled "Embodiments of the present disclosure."

[0145] [8] the antenna has a first conductor connected to the signal processing unit, and a second conductor connected to the housing and spaced apart from the first conductor to serve as the reference potential; The coil is connected to the first conductor and the second conductor of the antenna. [6] A power transmission line evaluation system as described in.

[0146] [9] a management center that receives the data signal from the wireless unit and evaluates a state of the power transmission line based on the charge amount data obtained from the data signal. The power transmission line evaluation system according to any one of [4], [5], [6] and [8].

[0147]

[10] The management center is configured to control the power source, and to control the charge amount measuring device and the wireless unit through wireless communication with the wireless unit. [9] The power transmission line evaluation system described in.

[0148]

[11] the management center is configured to transmit a request signal to the wireless unit; The wireless unit is configured to transmit the data signal including the charge amount data to the management center when the request signal is received from the management center via the antenna. The power transmission line evaluation system according to [9] or

[10] . [Explanation of symbols]

[0149] 10 Power Lines 10a 1st end 10b 2nd end 20 Transmission Line Evaluation System 60 Management Center 90 Insulation Material Evaluation System 100 Power Cable 101 Conductor 103 Insulating layer 105 Shielding layer 120 Termination 122 Pipe 124 Lower bracket 140 Intermediate joint 192 High voltage shield ring 194 Low voltage shield ring 200 power supply 202 Positive electrode 204 Negative electrode 300 Charge measurement section 320 Capacitor 400 Radio Section 420 Signal Processing Unit 440 Antenna 441 First Conductor 442 Antenna insulation layer 443 Second Conductor 444 Antenna Sheath 460 Coil 500 cabinet 620 Control Unit 622 CPU 624 RAM 626 Storage device 628 I / O ports 640 Center Radio Section 910 seats 912 1st electrode 914 2nd electrode 916 Guard Electrode 920 power supply 922 Switch 924 Switch 930 Charge measurement section 932 Capacitor 934 Switch

Claims

1. A power transmission line is connected to a power cable having a conductor, an insulating layer, and a shielding layer in this order in the radial direction of the conductor, and a power source capable of applying voltage between the conductor and the shielding layer, A charge quantity measuring unit is connected in series between the power supply and the transmission line, and measures the charge quantity which is the integral value of the current flowing between the conductor and the shielding layer of the transmission line. A wireless unit connected to the charge quantity measuring unit and capable of wirelessly transmitting charge quantity data measured by the charge quantity measuring unit to an external device, A housing that houses the charge measurement unit and a part of the wireless unit, and is connected to the charge measurement unit and the wireless unit as a common reference potential, Equipped with, The aforementioned power supply is The positive electrode connected to the conductor of the power transmission line, The negative electrode of the transmission line is grounded to earth together with the shielding layer, It has, The charge quantity measuring unit is connected in series between the positive electrode of the power supply and the conductor of the power transmission line. The housing is connected between the positive electrode of the power supply and the charge measurement unit, and is configured to be at the same potential as the positive electrode of the power supply. Power transmission line evaluation system.

2. The power supply is configured to apply a DC voltage of 10 kV or more or a square wave voltage between the conductor and the shielding layer of the transmission line. The power transmission line evaluation system according to claim 1.

3. The aforementioned wireless unit is Within the housing, a signal processing unit is connected to the charge quantity measuring unit, generates a data signal including the charge quantity data, and processes external signals. An antenna connected to the signal processing unit transmits the data signal to the outside and receives the signal from the outside, A coil connected to the housing as the reference potential and connected in parallel to the signal processing unit and the antenna, has A power transmission line evaluation system according to claim 1 or claim 2.

4. A step of preparing a power transmission line including a power cable having a conductor, an insulating layer, and a shielding layer in this order in the radial direction of the conductor, Steps to construct a power transmission line evaluation system comprising: a power supply connected to the power transmission line; a charge quantity measuring unit connected in series between the power supply and the power transmission line; a wireless unit connected to the charge quantity measuring unit and capable of wirelessly transmitting charge quantity data measured by the charge quantity measuring unit to an external party; and a housing that houses the charge quantity measuring unit and a part of the wireless unit and is connected to the charge quantity measuring unit and the wireless unit as a common reference potential; A step of applying a voltage between the conductor and the shielding layer using the aforementioned power supply, A step of using the charge quantity measuring unit to measure the charge quantity, which is the integral value of the current flowing between the conductor and the shielding layer of the power transmission line, Equipped with, In the process of constructing the aforementioned power transmission line evaluation system, The power supply is configured to have a positive electrode connected to the conductor of the power transmission line and a negative electrode grounded to earth together with the shielding layer of the power transmission line. The charge quantity measuring unit is connected in series between the positive electrode of the power supply and the conductor of the power transmission line. The housing is connected between the positive electrode of the power supply and the charge measurement unit, and configured to be at the same potential as the positive electrode of the power supply. Methods for evaluating power transmission lines.

Images