JP5154014B2 - Underground accident section evaluation device and underground accident section evaluation method - Google Patents

Description

The present invention relates to a ground fault section evaluation device and a ground fault section evaluation method for narrowing down a ground fault section in an underground electric line.

  In the overhead power line, a simple accident section rating device (fault sector) is introduced to narrow down the accident section when a ground fault occurs.

  In recent years, various technologies have been developed for underground cables, and those that detect discharge light that occurs when an abnormality occurs (see, for example, Patent Document 1), fix optical fibers along underground cables, One that utilizes the change in optical characteristics of the optical fiber due to the instantaneous expansion of the connecting portion when an accident occurs (see, for example, Patent Document 2), and the light in the optical fiber provided in the sensor due to a shock wave generated in the event of a cable accident (For example, refer to Patent Document 3).

In addition, there is a type in which a current induced in a ground line at the time of a ground fault occurs, a potential difference between both ends of a resistor is detected by an optical voltage sensor, and a detection result is transmitted by an optical fiber (for example, see Patent Document 4). ).
JP-A-8-101246 JP-A-10-267984 Japanese Patent No. 2569811 JP-A-8-43473

  However, the devices disclosed in Patent Documents 1 to 3 are devices that incorporate a current amplifier circuit, an arithmetic circuit, a communication control circuit, etc., in order to perform arithmetic analysis of the diversion ratio difference in the fault current circuit or to transmit information. It has a configuration. In addition, in the fault sector to be introduced into the overhead power line, it is necessary to detect a wide range of fault currents from a very small current (approximately several A) to a large current (approximately several hundreds of A). It is.

  Moreover, although the device disclosed in Patent Document 4 has a simple configuration including a current transformer, a resistance element, and an optical voltage sensor, the magnitude of the received light signal transmitted through the optical fiber is used to determine the accident section. It is necessary to determine the thickness and phase.

  Furthermore, since the above-described conventional apparatus is based on the premise that measurement results at a plurality of locations are monitored by a single monitoring center, the monitoring center and each measuring device must be optically or electrically connected. It is difficult to apply to underground cable lines that have already been buried.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is a simple and inexpensive device capable of narrowing down an accident section, and is used for underground cables that have already been buried. However, it is an object of the present invention to provide an underground line accident section rating apparatus and a ground line accident section rating method that can be easily installed and that can narrow down the accident section only by the magnitude of the current flowing through the grounding wire.

In order to achieve the above-described object, the underground line accident section evaluation device according to the present invention has an R phase, an S phase, and a T phase when a ground fault occurs in the underground electric line configured as follows. a phase detecting the magnitude of the fault current flowing through each of the ground lines to narrow down the ground fault generating section by device, a current detection unit, and the current display unit, the parallel resistor and the one of the base In preparation. The current detection unit has first and second output terminals, and outputs a secondary current between the first and second output terminals by electromagnetic induction with respect to the fault current. The current display unit is electrically connected between the first and second output terminals, and displays whether or not a secondary current of a predetermined magnitude or more has flowed between the first and second output terminals. . The parallel resistance element is electrically connected in parallel with the current display unit between the first and second output terminals. Furthermore, this underground cable accident section rating device is provided for each of the R-phase, S-phase, and T-phase ground wires.
The above-described underground electric line includes an R-phase wire having a plurality of R-phase shield wires insulated from the R-phase conductor and the R-phase conductor, and a plurality of insulated wires from the S-phase conductor and the S-phase conductor. An S-phase wire having an S-phase shield wire, and a T-phase wire having a T-phase conductor and a plurality of T-phase shield wires insulated from the T-phase conductor; The T-phase shield wire is grounded via a ground wire at a plurality of ground locations. The ground line is composed of an R-phase ground line connecting between the R-phase connection point where the two adjacent R-phase shield lines are connected to each other and the ground connection point, and two adjacent S-phase shield lines. The S-phase ground line connecting between the S-phase connection point and the ground connection point connected to each other, and the T connecting between the T-phase connection point and the ground connection point where two adjacent T-phase shield lines are connected to each other. A phase ground line, a ground connection point to which the R phase, S phase, and T phase ground lines are respectively connected, and a ground connection line that connects a ground terminal.

  In carrying out the above-described underground cable accident section evaluation device, it is preferable to provide a fault current detection current transformer as a current detection unit and a fuse as a current display unit.

  According to a preferred embodiment of the present invention, the current detection unit, the current display unit, and the parallel resistance element are preferably provided in a waterproof container having a transparent lid.

According to another preferred embodiment of the underground cable fault section evaluation device of the present invention, when a fault current caused by a ground fault flows through the ground line in the above-described underground cable line, the fault current is detected. A ground line accident section evaluation device that narrows down the section where a ground fault occurs, and includes a current detection unit, a rectifier circuit, a smoothing circuit, and a current display unit on one pedestal.

The current detection unit has first and second output terminals, and outputs a secondary current between the first and second output terminals by electromagnetic induction with respect to the fault current. The rectifier circuit full-wave rectifies the secondary current and outputs a rectified current. The smoothing circuit obtains a direct current from the rectified current. The current display unit further includes a relay circuit, a magnetic reversal indicator, and a Zener diode, and receives a direct current. When the DC current exceeds a preset reference value, the relay circuit enters an ON state in which the DC current flows through the magnetic reversal indicator. On the other hand, when the DC current is below the reference value, the DC current passes through the Zener diode. Is turned off. When a direct current flows, the magnetic reversal indicator reverses the display plate provided in the magnetic reversal display and displays whether the direct current has flowed. A current detection unit and a rectifier circuit are provided for each of the R-phase, S-phase, and T-phase ground lines, and outputs of the rectifier circuits are connected in series.
Further, according to a preferred embodiment of the present invention, in the above-described underground electric wire path, the difference in ground resistance at a plurality of ground locations should be within 5 times.
The underground accident section evaluation method according to the present invention narrows down the ground fault occurrence section when a ground fault occurs in the above-described underground electric line. That is, the underground accident section evaluation method includes the following first and second processes.
In the first process, when a ground fault occurs, a secondary current generated by electromagnetic induction with respect to a fault current flowing through each of the R-phase, S-phase, and T-phase ground lines is output.
In the second process, a fault display grounding location, which is a grounding location where one or more R-phase, S-phase, and T-phase grounding wires in which a secondary current of a predetermined magnitude or more flows, is located.
Then, the underground accident section is narrowed down to a section between two adjacent failure display ground locations.

According to the underground accident section evaluation device and the underground accident section evaluation method of the present invention, since it is not necessary to provide a current amplifier circuit, a communication control circuit, etc., it is possible to narrow down the accident section with a simple and inexpensive device. it can.

Further, according to the underground line accident section evaluation device and underground line accident section evaluation method of the present invention, by using a fuse in the current display unit, by monitoring whether the fuse has blown, or by magnetic reversal Since the accident section is narrowed down by monitoring whether or not the display board included in the display is reversed, it is not necessary to supply power from an external power source. In addition, electrical or optical connection from each installation location to the monitoring center is not required, and it can be easily installed on underground cable paths that have already been buried.

  In addition, by providing each component of the underground cable accident section rating device in a waterproof container, it can be used in a humid environment such as a manhole.

Further, by making the container lid transparent, the inside can be easily seen, and daily maintenance becomes easy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, each component and arrangement relationship are merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described. However, numerical conditions and the like are merely preferred examples. Therefore, the present invention is not limited to the following embodiment.

  The outline of the ground fault will be described with reference to FIG. FIG. 1 is a schematic diagram schematically showing a method for determining a section of a ground fault in an underground electric line.

  The underground electric line buried in the ground is composed of a three-phase cable including three cable lines of an R-phase line, an S-phase line, and a T-phase line. The R-phase wire includes an R-phase conductor 14 and an R-phase shield wire 17 that is insulated from the R-phase conductor 14. The S phase wire includes an S phase conductor 15 and an S phase shield wire 18 that is insulated from the S phase conductor 15. The T-phase wire includes a T-phase conductor 16 and a T-phase shield wire 19 that is insulated from the T-phase conductor 16. A conventionally well-known, for example, cross-linked polyethylene insulated power (CV) cable can be used as the underground electric line. In this CV cable, an R-phase conductor 14, an S-phase conductor 15 and a T-phase conductor 16 are respectively covered with an insulator, and an R-phase shield wire 17, an S-phase shield wire 18 and a T-phase shield wire 19 are surrounded around each insulator. It has.

  The R-phase shield wire 17, the S-phase shield wire 18 and the T-phase shield wire 19 of the underground cable track are connected to the ground wire 20 (20a, 20b,..., 20h) at the ground location 70 (70a, 70b,..., 70h). Is grounded. In the case of an underground electric line, the grounding location 70 is provided for each manhole, for example, and the grounding wire 20 is connected to a grounding terminal (manhole grounding terminal) provided in each manhole. The ground line 20 includes an R-phase ground line 21, an S-phase ground line 22, a T-phase ground line 23, and a ground connection line 24 connected at a ground connection point 25. R-phase ground line 21, S-phase ground line 22 and T-phase ground line 23 connect R-phase shield line 17, S-phase shield line 18 and T-phase shield line 19 to ground connection line 24, respectively. .

  In the following, for simplicity of explanation, the R-phase shield wire 17, the S-phase shield wire 18 and the T-phase shield wire 19 are each assumed to have a configuration in which a plurality of shield wires are connected at a grounding location 70. . That is, the R phase shield wire 17 is composed of first to seventh R phase shield wires 17a to 17g, the S phase shield wire 18 is composed of first to seventh S phase shield wires 18a to 18g, and the T phase. The shield wire 19 includes first to seventh T-phase shield wires 19a to 19g. For example, the first R-phase shield wire 17a and the second R-phase shield wire 17b are connected at the second R-phase connection point 27b of the second ground location 70b, and further the second R-phase ground wire. 21b. Second R-phase ground line 21b is connected to second ground line 20b.

  When a ground fault occurs in the underground cable track, a fault current flows between the conductor and the shielded wire. Here, a ground fault occurs between the fifth grounding point 70e and the sixth grounding point 70f of the T-phase wire, and 240 A (provided that the T-phase conductor 16 and the fifth T-phase shielded wire 19e are not connected). , A represents an ampere), and a case where a ground fault current (indicated by an arrow X in the figure) flows will be described. Since the ground resistance at each ground point 70 is larger than the resistance of each of the R-phase, S-phase, and T-phase shield wires 17, 18 and 19, the ground fault current is the first to eighth ground points 70a to 70h. And is distributed in proportion to the reciprocal of the resistance value of the ground resistance, and flows through the first to eighth ground lines 20a to 20h toward the ground (indicated by an arrow B in the figure). When the ground resistances of the first to eighth ground lines 20a to 20h are all equal, the currents flowing through the respective ground lines 20 are also equal, and a current of 30A flows through each. As a result, the current (indicated by the arrow C in the figure) flowing from the ground fault location through the fifth T-phase shield wire 19e toward the fifth ground location 70e is applied to the first to fifth ground wires 20a to 20e. The sum of the flowing currents is 150A. Further, a current (indicated by an arrow D in the figure) that flows from the ground fault location through the fifth T-phase shield wire 19e toward the sixth ground location 70f flows through the sixth to eighth ground wires 20f to 20h. The total current becomes 90A.

  The resistance values of the R-phase shield wire 17, the S-phase shield wire 18 and the T-phase shield wire 19 with respect to the ground are determined by the value of the ground resistance, and the R-phase shield wire 17, the S-phase shield wire 18 and the T at a certain ground location 70 are determined. The resistance values of the phase shield wire 19 with respect to the ground are equal.

  At the fifth grounding point 70e, a current of 30A flows through the fifth grounding line 20e toward the ground. At the fifth grounding point 70e, the currents flowing toward the fifth grounding point 70e, except for the portion flowing through the fifth ground connection line 24e toward the ground, are equally distributed to the shield lines. Flowing. A current of 150A flows from the fifth T-phase shield wire 19e to the fifth grounding point 70e, of which 30A flows toward the ground via the fifth ground connection line 24e. Accordingly, the remaining 120A is divided into three equal parts, and 40A of current flows through the fourth R-phase shield wire 17d, the fourth S-phase shield wire 18d, and the fourth T-phase shield wire 19d to the fourth ground location. It flows toward 70d. As a result, at the fifth grounding point 70e, 40A out of the current 150A flowing through the fifth T-phase shield wire 19e flows through the fourth T-phase shield wire 19d toward the fourth grounding point 70d. The remaining 110A flows through the fifth T-phase ground line 23e toward the fifth ground connection point 25e. Of the current of 110A flowing to the fifth T-phase ground connection point 25e, a current of 30A flows toward the ground via the fifth ground connection line 24e, and a current of 40A is supplied to each of the fifth currents. It flows to the fourth R-phase shield line 17d via the R-phase ground line 21e and to the fourth S-phase shield line 18d via the fifth S-phase ground line 22e.

  From the fourth R-phase shield wire 17d, the fourth S-phase shield wire 18d, and the fourth T-phase shield wire 19d, currents of 40 A (indicated by an arrow E in the figure) are supplied to the fourth ground point 70d. ), That is, a total current of 120 A flows. Among them, a current of 30 A flows toward the ground through the fourth ground connection line 24d. Therefore, the third R-phase shield wire 17c, the third S-phase shield wire 18c, and the third T-phase shield wire 19c are connected to the fourth ground wire from the current 120A flowing to the fourth ground location 70d. A current of 30A is obtained by dividing 90A into three equal parts, excluding the current of 30A flowing toward the ground at 20d. At this time, each of the fourth R-phase ground line 21d, the fourth S-phase ground line 22d, and the fourth T-phase ground line 23d has a current of 10 A toward the fourth ground connection point 25d. Flowing.

  Similarly, in the first to third grounding locations 70a to 70c, the first to third R-phase grounding wires 21a to 21c, the first to third S-phase grounding wires 22a to 22c, and the first to third T-phases. A current of 10 A flows through the ground lines 23a to 23c.

  90 A of current flows from the fifth T-phase shield wire 19 e to the sixth grounding point 70 f, and 30 A of the current flows toward the ground via the sixth grounding wire 20 f. Accordingly, the remaining 60A is divided into three equal parts, and each of the currents of 20A causes the sixth R-phase shield wire 17f, the sixth S-phase shield wire 18f, and the sixth T-phase shield wire 19f to pass through the seventh grounding point. It flows toward 70g. As a result, at the sixth ground location 70f, a current of 70A flows through the sixth T-phase ground wire 23f toward the sixth ground connection point 25f. The sixth R-phase ground line 21f and the sixth S-phase ground line 22f have a current of 20A toward the sixth R-phase shield line 17f and the sixth S-phase shield line 18f, respectively. Flowing.

  From the sixth R-phase shield wire 17f, the sixth S-phase shield wire 18f, and the sixth T-phase shield wire 19f, a current of 20A (indicated by an arrow H in the figure) is supplied to the seventh grounding point 70g. ) Flows. Among them, a total current of 30 A flows toward the ground through the seventh ground line 20 g. Accordingly, a current of 10 A flows through the seventh R-phase shield wire 17g, the seventh S-phase shield wire 18g, and the seventh T-phase shield wire 19g. At this time, a current of 10 A flows through the sixth R-phase ground line 21f, the sixth S-phase ground line 22f, and the sixth T-phase ground line 23f toward the ground.

  Similarly, at the eighth ground point 70h, a current of 10 A flows through the eighth R-phase ground line 21h, the eighth S-phase ground line 22h, and the eighth T-phase ground line 23h.

  At the grounding locations 70 at both ends of the ground fault location, a current of 30 A or more, which is a current value flowing toward the ground at each grounding location 70, flows through one or more grounding lines of R phase, S phase, and T phase. On the other hand, in the installation location 70 that is not adjacent to the ground fault location, only one third of 30A that is the current value flowing toward the ground at each ground location 70, that is, a current of 10A flows.

  Accident section rating device is attached to each ground connection line, and when a ground fault occurs, the current flowing through the ground connection line is detected to evaluate the accident section.

(First embodiment)
The configuration of the accident section rating device will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining a configuration example of the accident section rating device. FIG. 2 (A) is a schematic configuration diagram of the accident section rating device as viewed from the side, and FIG. 2 (B) is an equivalent circuit diagram of the accident section rating device.

  The accident section rating device 30 includes a fault current detection current transformer (CT) 40 as a current detection unit, a parallel resistance element 48, and a fuse 50 as a current display unit on one pedestal 35. Here, the fault current detection CT (hereinafter also referred to simply as the current detection CT) 40 and the parallel resistance element 48 are provided on the pedestal 35, and the fuse 50 is attached to the pedestal 35. It is provided on the fuse mount 37. Here, in order to reduce the area of the pedestal 35 of the accident section evaluation device 30, an example in which the fuse mounting base 37 is attached is shown, but the fuse 50 may be provided on the pedestal 35. The pedestal 35 and the fuse mounting base 37 are made of an insulating material.

  The output terminals 44 and 45 of the current detection CT 40 are electrically connected via a fuse 50. The parallel resistance element 48 is electrically connected in parallel with the fuse 50 between the output terminals 44 and 45 of the current detection CT 40. In FIG. 2A, the wiring for electrically connecting the current detection CT 40, the parallel resistance element 48, and the fuse 50 is not shown.

  A so-called penetration type CT is used as the current detection CT 40. One of the output terminals 44 and 45 is a first output terminal, and the other is a second output terminal. This penetration type CT is formed in the form of an air-core coil, and the accident section rating device 30 is installed so that the ground wires 21 (22, 23) of each phase pass through the through holes 42 as the ground wires. The When a primary current (indicated by an arrow L in the figure) flows as a fault current in the ground wires 21 (22, 23) of each phase, a secondary current (in the figure, an arrow M) is output from the output terminal 44 of the current detection CT 40. Is output). The secondary current M is divided into a first secondary current (indicated by an arrow N in the figure) and a second secondary current (indicated by an arrow P in the figure), and the first secondary current is distributed. N flows through the fuse 50, while the second secondary current P flows through the parallel resistance element 48.

  The fault current generated in the event of a ground fault in the underground cable line is defined by the current capacity (NGR current capacity) flowing through the neutral point ground resistance (NGR) of the substation, and is about 150 to 600A. The fault current flowing through each ground line 20 is determined at a rate determined according to the position of the accident occurrence location, and is connected to the ground locations (fifth ground location 70e and sixth ground location 70f in FIG. 1) on both sides of the accident occurrence zone. It is shunted towards. The fault current flowing through each ground connection line 21 (22, 23) is minimized because the fault current of 150A generated in the event of a ground fault is halved toward the ground locations 70 on both sides of the fault occurrence section. This is a case where the current is divided. On the other hand, the maximum value is the case where most of the fault current of 600 A generated in the event of a ground fault flows toward one grounding location, so the value is about 600 A. The magnitude of the current flowing through each ground connection line is determined according to the number of ground locations and the value of the ground resistance. Here, even if a current transformation ratio which is a ratio of the primary current L to the secondary current M is as large as about 100: 1, which is generally used in a distribution board device or the like, the secondary current M is The current amplifying circuit is unnecessary because it is about 0.1 to 1A.

  As the current detection CT 40, a commercially available one can be used, and the rated primary current is 100 A, the rated secondary current is 1 A, and the accident section rating device 30 is simplified and reduced in size. A standard whose allowable input current is 500% of the rated primary current can be selected. The CT 40 for current detection is connected to the ground in the event of a ground fault such as the NGR current capacity of the substation, the number of grounding locations, and the value of grounding resistance, which supplies power to the underground cable conduit to which the accident section evaluation device 30 is attached. It is selected according to the magnitude of the fault current flowing through the wire.

  The fuse 50 is blown when the first secondary current M generated when the fault current L flows through the ground line 20 becomes equal to or higher than the fusing standard.

  When the secondary current M output from the current detection CT 40 is set to 0.7 to 5 A, the condition that the fuse 50 should satisfy is that the secondary current M should be operated or blown at about 0.7 A. . On the other hand, even when it is normal, a current of about 3 A flows through the grounding wire 20, so that it is also necessary not to operate below the secondary current corresponding to 3 A.

  In addition, when a ground fault occurs, power transmission is immediately interrupted by the operation of the equipment at the substation, so the time during which the fault current flows is usually about 0.1 seconds. Therefore, the fuse 50 must be blown within 0.1 seconds when a primary current L of 0.7 A or more flows.

  The fuse will be described with reference to FIG. FIG. 3 is a schematic view of the fuse as viewed from above. A display unit 54 is provided on the display surface 52 that is the upper surface of the fuse 50. The display unit 54 can visually recognize the presence or absence of operation, for example, by changing the color before and after the fuse is blown.

  Any suitable fuse can be used as the fuse satisfying the above conditions. For example, a fuse of the type MP032 (trade name) manufactured by Daito Tsushinki Co., Ltd. can be used. The MP032 melts in about 0.07 seconds when a current of 0.7 A flows, and the rated current is 0.32 A. Therefore, the MP032 does not operate at 0.03 A. The MP032 includes a display surface 52 as shown in FIG. 3, and the color of the display unit 54 changes from black to white before and after the fuse 50 is blown, that is, before and after the operation. The fuse 50 is attached to the fuse mount 37 (see FIG. 2A) with the display surface 52 facing upward so that the presence or absence of fusing can be easily recognized. In addition, although the structure provided with the display part 54 on the display surface 52 was demonstrated here as an example, it is not limited to this structure. As the fuse 50, a fuse having an arbitrary structure in which the presence or absence of fusing can be visually recognized can be used.

  The parallel resistance element 48 is provided to prevent the output terminals 44 and 45 of the current detection CT 40 from being opened when the fuse 50 malfunctions. As described above, even if it is normal, a current of about 3 A at the maximum flows through the ground line 20. In this state, when the output terminals 44 and 45 of the current detection CT 40 are opened due to malfunction of the fuse 50. The output terminals 44 and 45 are charged and dangerous. In the accident section rating device 30 of the present invention, the parallel resistance element 48 is provided in parallel with the fuse 50. Therefore, even if the fuse 50 is blown due to malfunction or the like, the secondary current flows through the parallel resistance element 48, so that the output terminals 44 and 45 of the current detection CT 40 are not opened.

  The resistance value of the parallel resistance element 48 is determined according to the occupational safety and health regulations that the fuse 50 operates reliably in the event of a ground fault and that the induced voltage generated in the parallel resistance element 48 by the second secondary current P is It is determined in consideration of the danger value (300V) or less.

  In order to operate the fuse 50 reliably, it is necessary to make the first secondary current N flowing through the fuse 50 larger than the fusing current of the fuse 50 when a ground fault occurs. On the other hand, in order to reduce the induced voltage, it is necessary to reduce the resistance value of the parallel resistance element 48. When MP032 is used as the fuse 50, considering that the resistance value of the fuse 50 is about 1.4Ω, the resistance value of the parallel resistance element 48 may be set to 50Ω.

  According to the accident section evaluation apparatus of the present invention described above, it is possible to narrow down the accident sections with a simple and inexpensive device that does not include a current amplifier circuit or a communication control circuit. In addition, by using a fuse in the current display section and narrowing down the accident section by monitoring whether the fuse has blown or not, electrical or optical connection from each installation location to the monitoring center becomes unnecessary, It can be installed easily even for underground cables that have already been buried.

  Since the accident section rating device is installed in a wet and flooded environment such as a manhole, for example, a waterproof device storage container is prepared and each component of the accident section rating device is stored in the device storage container. It is good to install in.

  With reference to FIG. 4, the installation method of the accident area determination apparatus is demonstrated. FIG. 4 is a schematic view of the accident section rating device in which each component is stored in the device storage container as viewed from above. FIG. 4 shows a state in which the lid of the device storage container 60 is removed. The accident section rating device 30 whose side view is shown in FIG. 2A is fixed in a waterproof device storage container 60. Since the grounding wire 20 passes through the device storage container 60, the waterproof property is improved by covering the grounding wire 20 with the heat shrinkable tube 62 at a portion where the grounding wire 20 passes through the device storage container 60. In addition, for the convenience of daily maintenance, the lid of the device storage container 60 is preferably transparent in order to facilitate visual recognition of the internal state such as the fusing of the fuse 50.

  As described above, the accident section rating device of the present invention does not require a power source and does not use consumables with a limited period, so that it is maintenance-free after grounding. Even if the fuse needs to be replaced due to malfunction or the like, the output terminal of the current detection CT is not opened by the parallel resistance element, so that the fuse can be replaced without stopping power transmission.

  With reference to FIGS. 5, 6, and 7, the operation confirmation test of the accident section rating device of the present invention will be described. FIG. 5 is a diagram showing a test circuit for performing an operation confirmation test of the accident section rating device of the present invention.

  Here, the first to sixth cables 80a to 80f having a length of 8 m are connected in series at the first to fifth grounding locations 70a to 70e to form a cable having a length of 48 m. The 1st-5th grounding location 70a-70e respond | corresponds to a manhole, and the state which provided 5 manholes every 8 m is simulated by this structure. As the first to sixth cables 80a to 80f, triplex-type cross-linked polyethylene insulated power (CVT) cables composed of three single-core cables are used.

  Usually, in power transmission, power is transmitted in three phases of R phase, S phase, and T phase. The three single-core cables provided in each of the first to sixth cables 80a to 80f are first to sixth R-phase wires 11a to 11f that perform power transmission in the R-phase, and first to first that perform power transmission in the S-phase, respectively. 6 S-phase wires 12 a to 12 f and first to sixth T-phase wires 13 a to 13 f that perform T-phase power transmission. In the following description, the first to sixth R-phase wires 11a to 11f are represented as R-phase wires 11, and the first to sixth S-phase wires 12a to 12f are represented as S-phase wires 12. In addition, the first to sixth T-phase wires 13a to 13f may be referred to as the T-phase wire 13 as a representative. As described with reference to FIG. 1, the R-phase wire 11, the S-phase wire 12, and the T-phase wire 13 are the R-phase conductor 14, the S-phase conductor 15 and the T-phase conductor 16, and the R-phase shield wire 17, S A phase shield wire 18 and a T phase shield wire 19 are provided.

  The first to sixth R-phase wires 11a to 11f, the first to sixth S-phase wires 12a to 12f, and the first to sixth T-phase wires 13a to 13f included in the first to sixth cables 80a to 80f. Each cable includes the first to fifth R-phase connection portions 71a to 71e, the first to fifth S-phase connection portions 72a to 72e, and the first to fifth grounding portions 70a to 70e. The T-phase connection parts 73a to 73e are connected to each other.

  In the first to fifth R-phase connection portions 71a to 71e, the R-phase shield wire 17 is connected to the first to fifth R-phase ground wires 21a to 21e, and in the first to fifth S-phase connection portions 72a to 72e. The S-phase shield wire 18 is connected to the first to fifth S-phase ground wires 22a to 22e, and in the first to fifth T-phase connection portions 73a to 73e, the T-phase shield wire 19 is connected to the first to fifth S-phase ground wires 22a to 22e. 5 T-phase ground lines 23a to 23e.

  As the accident section rating devices, the first to fifth R-phase ground lines 21a to 21e, the first to fifth S-phase ground lines 22a to 22e, and the first to fifth T-phase ground lines 23a to 23e, First to fifth R-phase rating devices 31a to 31e, first to fifth S-phase rating devices 32a to 32e, and first to fifth T-phase rating devices 33a to 33e are attached.

  Both ends of a cable formed by connecting six first to sixth cables 80a to 80f in series are connected to the input end and the output end of the AC power supply 90, respectively. Using the AC power supply 90, power having a voltage of 200V and a current of 450A is supplied to the first to sixth cables 80a to 80f connected in series for 0.1 second. At the point of the accident, a ground fault is simulated by directly connecting the conductor and the shield wire with a copper wire.

  6 (A) and 6 (B) are diagrams showing operation states in a ground fault simulation test performed using the test circuit described with reference to FIG. 6 (A) and 6 (B), the horizontal axis shows the measurement points as the input and output terminals (CH1, CH2) of the AC power supply 90 and the first to fifth grounding points 70a to 70e (MH1 to MH5). The vertical axis indicates the current value (A: ampere) flowing through the ground line of each phase. It should be noted that an ammeter (not shown) is attached to the input end and output end of the AC power supply 90 and each ground location 70, and the ground line current flowing through each of the R-phase, S-phase, and T-phase ground lines is supplied. taking measurement. 6A and 6B, the ground line current for each phase of the R phase (●, dotted line I), the S phase (■, one-dot broken line II), and the T phase (Δ, solid line III), and the AC power supply 90 And the sum (x, broken line IV) of the R-phase, S-phase, and T-phase ground line currents is shown for each of the first to fifth ground locations 70a to 70e.

  FIG. 6A shows a current value when a ground fault occurs on the S-phase line 12 of the third grounding point 70c (the portion indicated by MH3 in FIG. 6A). Here, it is assumed that the current at the input end and the output end of the AC power supply is not distinguished from the current at the input end and the output end, and flows through the input end. In addition, the ground resistance at each ground location is assumed to be equal. A current of about 60 A flows through each grounding location. The remaining current of 390A flows through each of the R-phase, S-phase, and T-phase shield wires into three equal portions of 130A. In this case, a current of about 300 A flows from the shield line of the third S-phase connection portion 72c to the ground connection point via the third S-phase ground line 22c. As a result, the third S-phase rating device 32c attached to the third S-phase ground line 22c operates. At this time, even in the third R-phase ground line 21c and the third T-phase ground line 23c other than the ground line connected to the S-phase line 12 at the third ground point 70c where the accident has occurred, 100A About current flows. As a result, the third R-phase rating device 31c and the third T-phase rating device 33c attached to the third R-phase ground wire 21c and the third T-phase ground wire 23c also operate. In order to narrow down the accident section, it is understood that a ground fault has occurred in the vicinity of the third ground contact point 70c, so there is no problem.

  FIG. 6B shows a current value when a ground fault occurs on the S-phase line 12 (the portion indicated by MH5 in FIG. 6B) of the fifth grounding point 70e. Similar to the case where the ground fault occurred in the S-phase line 12 of the third grounding point 70c described with reference to FIG. 6A, the S-phase grounding of the fifth grounding point 70e where the accident occurred. Not only the fifth S-phase rating device 32e attached to the line 22e but also the fifth R-phase rating device 31e and the fifth T-phase rating device 33e are operating.

  FIGS. 7A and 7B are diagrams showing the results of an operation test performed using the test circuit described with reference to FIG. 5 and showing an operation state due to variations in ground resistance. In FIGS. 7A and 7B, as in FIGS. 6A and 6B, the horizontal axis indicates the measurement point, the input and output ends of the AC power supply 90, and the first to fifth grounding points. 70a to 70e are shown, and the vertical axis indicates the current value (A) flowing through the ground line of each phase. Here, the ground resistance is determined by the resistance of the ground wire or the ground electrode itself, the resistance indicated by the soil around the ground electrode, or the like. 7A and 7B, the ground line current for each phase of the R phase (●, dotted line I), S phase (■, one-dot broken line II), and T phase (Δ, solid line III), and the AC power supply 90 And the sum (x, broken line IV) of the R-phase, S-phase, and T-phase ground line currents is shown for each of the first to fifth ground locations 70a to 70e.

  FIG. 7A shows the S-phase line 12 of the third grounding point 70c (FIG. 7A when the grounding resistance at the first grounding point 70a is 1/10 of the third grounding point 70c. ), The current value when a ground fault occurred is shown in the part indicated by MH3). In this case, not only the third R-phase ground line 21c, the third S-phase ground line 22c, and the third T-phase ground line 23c of the third grounding point 70c where the ground fault has occurred, A current of about 100 A flows also in the first R-phase ground line 21a, the first S-phase ground line 22a, and the first T-phase ground line 23a at one ground location 70a. As a result, the first R-phase rating device 31a, the first S-phase rating device 32a, and the first T-phase rating device 33a provided at the first grounding point 70a also operate. This is because the ground line of the first ground point 70a having a low ground resistance, that is, the first R-phase ground line 21a, the first S-phase ground line 22a, and the first T-phase ground line 23a. This is because the current flowing through the ground line is prorated according to the reciprocal of the resistance value of the ground resistance, so that a larger current flows than at other ground locations.

  FIG. 7B shows the S-phase line 12 of the third ground point 70c (FIG. 7B when the ground resistance at the first ground point 70a is 1/5 of the third ground point 70c. ), The portion indicated by MH3) shows the ground line current when a ground fault occurs. In this case, a current of about 50 A is flowing not only in the third grounding location 70c where the ground fault occurred but also in the first grounding location 70a. Here, since the accident section rating device is set to operate when a current of 70 A flows through the grounding wire, the first grounding point 70 a has a lower grounding resistance than the other grounding wires. Even if a large current flows, the accident section rating device does not operate.

  Thus, if the difference in grounding resistance between the point of failure and the point other than the point of failure is within 5 times, it will not be affected by the variation in grounding resistance, but if the variation is large, it will exceed 10 times, for example. In this case, in addition to the accident location, the accident section rating device may operate at a location where the ground resistance is low. Therefore, when installing the device, it is necessary to know the accurate grounding resistance at the installation location.

(Second Embodiment)
With reference to FIG. 8, the underground line accident section rating apparatus of 2nd Embodiment is demonstrated. FIG. 8 is a schematic diagram for explaining another configuration example of the accident section rating device.

  The underground accident section evaluation device according to the second embodiment is configured to include a current detection unit 140, a rectification circuit 180, a smoothing circuit 190, and a current display unit 150 on one pedestal.

  As the current detection unit 140, a current detection CT can be used as in the first embodiment. The current detection CT has first and second output terminals, and outputs a secondary current between the first and second output terminals 144 and 145 by electromagnetic induction with respect to the fault current. The ratio of the secondary current of the current detection CT to the primary current is set to about 1/3000. In this case, when the current flowing through the R-phase, S-phase, or T-phase ground line 21 (22, 23) is 100 A, a current of 33 mA is output as a secondary current.

  The fault current is an alternating current, and therefore the secondary current output from the current detection CT is also an alternating current. The rectifier circuit 180 full-wave rectifies the secondary current that is an alternating current and outputs a rectified current. As the rectifier circuit 180, a conventionally known bridge type rectifier circuit using four diodes 182 can be used. Three current detectors 140 and rectifier circuits 180 are provided corresponding to the connection lines of the R phase, the S phase, and the T phase. Here, an example in which the outputs of the rectifier circuit 180 are connected in series and one smoothing circuit 190 and one current display unit 150 are provided will be described, but the present invention is not limited to this example. The outputs of the rectifier circuit 180 may be connected in parallel, or the outputs of the rectifier circuit 180 are not connected to each other, and the smoothing circuit 190 and the current display unit 150 are provided in each of the R phase, the S phase, and the T phase. May be.

  The rectified current output from the rectifier circuit 180 includes a ripple that is an AC component. In order to reduce ripples, a smoothing circuit 190 is provided. As the smoothing circuit 190, for example, a conventionally known capacitor input type smoothing circuit can be used. In this case, the smoothing circuit 190 includes a capacitor 192 and a resistance element 194 that are electrically connected in parallel. The smoothing circuit 190 reduces ripples by charging and discharging the capacitor 192 and obtains a direct current from the rectified current.

  The current display unit 150 includes a resistance element 154, a relay circuit 160, a magnetic reversal display 170, and a Zener diode 156. The relay circuit 160 includes first and second input terminals 167a and 167b, and first, second and third output terminals 168a, 168b and 168c. As will be described later, when the direct current flowing between the first and second input terminals 167a and 167b exceeds a preset reference value, the relay circuit 160 is connected between the first and second output terminals 168a and 168b. The third and second output terminals 168c and 168b are electrically connected to each other. On the other hand, in the case of the reference value or less, between the first and second output terminals 168a and 168b, and the third and second output terminals. The output terminals 168c and 168b are electrically disconnected from each other.

  The current display unit 150 includes a first terminal 152a and a second terminal 152b. The first terminal 152 a of the current display unit 150 and the first input terminal 167 a of the relay circuit 160 are electrically connected via a resistance element 154. The second terminal 152 b of the current display unit 150 and the second input terminal 167 b of the relay circuit 160 are electrically connected via a Zener diode 156. Here, the direct current obtained by the smoothing circuit 190 flows through the current display unit 150 from the first terminal 152a toward the second terminal 152b. The Zener diode 156 is provided in a direction opposite to the current direction.

  As the relay circuit 160, for example, any suitable known well-known photoMOS relay can be used. Here, an example in which a photo MOS relay is used as a relay circuit will be described with reference numeral 160 attached to the photo MOS relay. The first input terminal and the second input terminals 167 a and 167 b of the photo MOS relay 160 are electrically connected via a light emitting diode 162. The photo MOS relay 160 includes two NMOSs, a first NMOS 164 and a second NMOS 166. Two NMOS sources are connected to each other. The first output terminal 168 a of the photo MOS relay 160 is connected to the drain of the first NMOS 164, and the second output terminal 168 b of the photo MOS relay 160 is connected to the sources of the first and second NMOSs 164 and 166. Further, the third output terminal 168 c of the photoMOS relay 160 is connected to the drain of the second NMOS 166. A light receiving element (not shown) such as a photodiode is provided opposite to the light emitting diode 162, and the output of the light receiving element is input to the gates of the first and second NMOSs 164 and 166. When the current flowing between the first input terminal 167a and the second input terminal 167b of the photo MOS relay 160 exceeds a reference value, that is, a current necessary for causing the light emitting diode 162 to emit light, the light emitting diode 162 emits light. The light emitted from the light emitting diode 162 is received by the light receiving element, and the output of the light receiving element is input to the gates of the first and second NMOSs 164 and 166.

  As the light-emitting diode 162, any suitable known one can be used, and here, a light-emitting diode that emits light when a current of 0.5 mA flows is used. The resistance value of the resistance element 154 is set to 1 kΩ, and the breakdown (zener) voltage of the Zener diode 156 is set to 5V. The voltage drop due to the internal resistance of the light emitting diode 162 when a current of 0.5 mA flows through the light emitting diode 162 is assumed to be 1.2V.

  In this case, when a voltage exceeding 6.7 V is applied between the first terminal 152a and the second terminal 152b of the current display unit 150, a current of 0.5 mA flows through the light emitting diode 162, and as a result, The first and second NMOSs 164 and 166 are turned on.

  When the first NMOS 164 is turned on, the charge stored in the capacitor 192 of the smoothing circuit 190 passes through the magnetic reversal display 170 and the first NMOS 164 of the photo MOS relay 160 from the first terminal 152a to the second NMOS 164. To the terminal 152b.

  The magnetic reversal display 170 includes a magnetized display plate 172, a fixed pin 174 that holds the display plate 172 rotatably about a rotation shaft 173, and an electric wire 176 wound around the fixed pin 174 in a coil shape. I have.

  When a current flows through the coiled electric wire 176, the fixed pin 170 is magnetized. When the fixing pin 170 is magnetized, the display plate 172 is inverted.

  When the light emitting diode 162 emits light, the second NMOS 166 is also turned on, and the current flowing through the light emitting diode 162 does not pass through the Zener diode 156 but passes through the second NMOS 166 and the third output of the photo MOS relay 160. The current flows from the terminal 168c toward the second terminal 152b of the current display unit 150. Accordingly, once the photo MOS relay 160 is turned on, the photo MOS relay 160 is turned on until the voltage applied between the first and second terminals 152a and 152b of the current display unit 150 falls below 1.7V. Maintain state.

  Since the photo MOS relay 160 is turned on when a ground fault occurs, the ratio of the secondary current of the current detection CT 140 to the primary current is set to about 1/3000. In this case, when the current flowing through the R-phase, S-phase, or T-phase ground line 21 (22, 23) is 100 A, a current of 33 mA is output as a secondary current. Since the voltage of 6.7 V is applied between the first terminal 152a and the second terminal 152b of the current display unit 150 when the secondary current is 33 mA, the resistance value R of the resistance element 194 is What is necessary is just to set to about 200 (ohm) (= 6.7V / 33mA).

  The pulse width of the current required for operating the magnetic reversal display 170 is about 1 msec, and the required current value is about 50 mA. Accordingly, the amount of charge required during this period is 50 μC (= 50 mA × 1 msec). As a capacitor 192 that can discharge 50 μC from 6.7 V to 1.7 V, the capacitance C of this capacitor 192 can be set to 10 μF (= 50 μC / (6.7 V-1.7 V)). it can.

  Since the current interruption time of the substation is about 0.1 seconds, the charge amount Q supplied from the current detection CT to the capacitor 192 is 3.3 mC (= 33 mA × 0.1 sec), and the magnetic reversal display Sufficient charge can be stored to operate 170.

  According to the accident section evaluation apparatus of the second embodiment described above, the accident sections can be narrowed down with a simple and inexpensive device that does not include a current amplifier circuit or a communication control circuit. In addition, by using a magnetic reversal indicator in the current display section and monitoring whether the display plate of the magnetic reversal indicator is reversed, the accident section is narrowed down. Or optical connection is not required, and it can be easily installed even for underground cables that have already been buried.

  In addition, when a magnetic reversal display is used for the current display unit, the magnetic reversal display can invert the display plate in operation by passing a reset current, that is, in a direction opposite to that at the time of detecting a fault current. There is no need to replace the magnetic reversal display after an accident.

  Since the accident section rating device is installed in a wet and flooded environment such as a manhole, for example, a waterproof device storage container is prepared and each component of the accident section rating device is stored in the device storage container. It is good to install in.

It is a schematic diagram which shows roughly the section determination method of the ground fault accident of this invention . It is the schematic for demonstrating the structure of an accident area rating apparatus. It is the schematic which looked at the fuse from the upper surface. It is the schematic which looked at the accident area evaluation apparatus from the upper surface. It is a figure which shows the test circuit for performing the operation confirmation test of an accident area evaluation apparatus. It is a figure which shows the operation | movement condition in a ground fault simulation test. It is a figure which shows the operation condition by the dispersion | variation in ground resistance. It is the schematic for demonstrating the other structural example of an accident area rating apparatus.

Explanation of symbols

11, 11a-11f Cable line (R phase line)
12, 12a-12f Cable line (S phase line)
13, 13a-13f Cable line (T phase line)
14 R phase conductor 15 S phase conductor 16 T phase conductor 17 R phase shield wire 18 S phase shield wire 19 T phase shield wire 20, 20a-20h Ground wire 21, 21a-21h R phase ground wire 22, 22a-22h S Phase ground wire 23, 23a to 23h Phase T ground wire 24, 24a to 24h Ground connection wire 25, 25a to 25h Ground connection point 30 Accident section rating device 31, 31a to 31e R phase rating device 32, 32a to 32e S Phase rating device 33, 33a to 33e T phase rating device 35 Base 37 Fuse mounting base 40 Fault current detection current transformer (CT for current detection)
42 Through-hole 44, 45, 144, 145 Output terminal 48 Parallel resistance element 50 Fuse 52 Display surface 54 Display part 60 Device storage container 70, 70a-70h Grounding location 71, 71a-71h R phase connection part 72, 72a-72h S Phase connection unit 73, 73a to 73h T phase connection unit 80, 80a to 80f CVT cable 90 AC power supply 140 Current detection unit 150 Current display unit 154 Resistance element 156 Zener diode 160 Relay circuit (photo MOS relay)
162 Light-emitting diode 164, 166 NMOS
170 Magnetic reversal display 172 Display board 173 Rotating shaft 174 Fixed pin 176 Electric wire 180 Rectifier circuit 182 Diode 190 Smoothing circuit 192 Capacitor 194 Resistance element

Claims (7)

An R-phase wire having an R-phase conductor and a plurality of R-phase shield wires insulated from the R-phase conductor, and an S-phase conductor and a plurality of S-phase shield wires insulated from the S-phase conductor. And a T-phase wire having a T-phase conductor and a plurality of T-phase shield wires insulated from the T-phase conductor,
The R-phase, S-phase, and T-phase shield wires are grounded via ground wires at a plurality of ground locations,
The ground wire is connected to the R-phase ground wire connecting between the R-phase connection point where the two adjacent R-phase shield wires are connected to each other and the ground connection point, and the two adjacent S-phase shield wires are connected to each other. The S-phase ground line connecting between the S-phase connection point and the ground connection point, and the T-phase connection point between the T-phase connection point where the two adjacent T-phase shield lines are connected to each other and the ground connection point. In the underground electric line comprising: a phase ground line; and a ground connection line that connects the ground connection point and the ground terminal to which the R phase, S phase, and T phase ground lines are respectively connected .
Underground fault section evaluation device that detects the magnitude of a fault current flowing through each of the R-phase, S-phase, and T-phase ground lines when a ground fault occurs, and narrows down the section where the ground fault occurred. Because
A current detection unit having first and second output terminals and outputting a secondary current between the first and second output terminals by electromagnetic induction with respect to the fault current;
A current that is electrically connected between the first and second output terminals and indicates whether or not the secondary current of a predetermined magnitude or more has flowed between the first and second output terminals. A display unit;
Between the first and second output terminals, a parallel resistance element electrically connected in parallel with the current display unit is provided on one pedestal ,
The underground cable accident section rating device is provided for each of the R-phase, S-phase, and T-phase ground wires .   2. The underground line fault section evaluation device according to claim 1, further comprising a fault current detection current transformer as the current detection unit, and a fuse as the current display unit. The underground line accident section rating according to claim 1 or 2, wherein the current detection unit, the current display unit, and the parallel resistance element are provided in a waterproof container having a transparent lid. apparatus. An R-phase wire having an R-phase conductor and a plurality of R-phase shield wires insulated from the R-phase conductor, and an S-phase conductor and a plurality of S-phase shield wires insulated from the S-phase conductor. And a T-phase wire having a T-phase conductor and a plurality of T-phase shield wires insulated from the T-phase conductor,
The R-phase, S-phase, and T-phase shield wires are grounded via ground wires at a plurality of ground locations,
The ground wire is connected to the R-phase ground wire connecting between the R-phase connection point where the two adjacent R-phase shield wires are connected to each other and the ground connection point, and the two adjacent S-phase shield wires are connected to each other. The S-phase ground line connecting between the S-phase connection point and the ground connection point, and the T-phase connection point between the T-phase connection point where the two adjacent T-phase shield lines are connected to each other and the ground connection point. In the underground electric line comprising: a phase ground line; and a ground connection line that connects the ground connection point and the ground terminal to which the R phase, S phase, and T phase ground lines are respectively connected .
Underground fault section evaluation device that detects the magnitude of a fault current flowing through each of the R-phase, S-phase, and T-phase ground lines when a ground fault occurs, and narrows down the section where the ground fault occurred. Because
A current detection unit having first and second output terminals and outputting a secondary current between the first and second output terminals by electromagnetic induction with respect to the fault current;
A rectifier circuit for full-wave rectifying the secondary current and outputting a rectified current;
A smoothing circuit for obtaining a direct current from the rectified current;
The pedestal includes a current display unit to which the direct current is input,
The current display unit further includes a relay circuit, a magnetic reversal indicator, and a Zener diode,
When the direct current exceeds a preset reference value, the relay circuit enters an on state in which the direct current flows through the magnetic reversal indicator, while when the direct current is equal to or less than the reference value, The DC current flows through the Zener diode and enters an off state.
When the direct current flows, the magnetic reversal indicator displays whether the direct current flows by reversing a display plate provided in the magnetic reversal display ,
The current detector and the rectifier circuit are provided in each of the R-phase, S-phase, and T-phase ground lines, and outputs of the rectifier circuits are connected in series. Underground accident section evaluation device. The underground current accident section according to claim 4, wherein the current detection unit, the rectifier circuit, the smoothing circuit, and the current display unit are provided in a waterproof container having a transparent lid. Rating device. The ground line accident section rating device according to any one of claims 1 to 5, wherein a difference in grounding resistance at the plurality of grounding locations is within 5 times.   An R-phase wire having an R-phase conductor and a plurality of R-phase shield wires insulated from the R-phase conductor, and an S-phase conductor and a plurality of S-phase shield wires insulated from the S-phase conductor. And a T-phase wire having a T-phase conductor and a plurality of T-phase shield wires insulated from the T-phase conductor,
  The R-phase, S-phase, and T-phase shield wires are grounded via ground wires at a plurality of ground locations,
  The ground wire is connected to the R-phase ground wire connecting between the R-phase connection point where the two adjacent R-phase shield wires are connected to each other and the ground connection point, and the two adjacent S-phase shield wires are connected to each other. The S-phase ground line connecting between the S-phase connection point and the ground connection point, and the T-phase connection point between the T-phase connection point where the two adjacent T-phase shield lines are connected to each other and the ground connection point. A ground fault has occurred in a ground electric line comprising a phase ground wire, and a ground connection wire that connects the ground connection point and the ground terminal to which the R phase, S phase, and T phase ground wires are respectively connected. Underground accident section evaluation method that narrows down the section where the ground fault occurred when it occurred,
  A process of outputting a secondary current generated by electromagnetic induction with respect to a fault current flowing through each of the R-phase, S-phase, and T-phase ground lines when a ground fault occurs;
  A step of investigating a fault indication grounding location that is a grounding location where one or more of the R-phase, S-phase, and T-phase grounding wires through which the secondary current of a predetermined magnitude or more flows is located
  Narrow down the underground line accident section to the section between two adjacent fault indication ground locations
Underground accident section evaluation method characterized by this.

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