JP5818062B2 - Cable measurement mode switching device - Google Patents

Description

  The present invention provides, for example, cable phase confirmation when laying a three-phase cable in underground cableway construction, cable soundness confirmation, and switching for grounding the cable as a safety measure during construction. The present invention relates to a measurement mode switching device.

  The underground cableway is laid underground, so it is directly buried or laid in a conduit / cave, and the phase sequence to be laid and the soundness of the cable cannot be visually confirmed. For this reason, electrical confirmation is performed at each stage before the work, on the way, and after the completion of the construction.

  Conventionally, in underground cable work for laying a three-phase cable, a circuit for phase confirmation as shown in FIG. 12 is assembled for the cable terminal at each construction, and at the intermediate connection point or the other terminal during construction, Construction is proceeding while confirming each phase and soundness from the first phase to the third phase.

  That is, a sense meter (see, for example, Patent Document 1) 2 is connected to the terminal end of the cable (ground cable) 1, for example, the first phase (black) 3 is grounded, and the second phase (red) 4 is 1 MΩ. Alternatively, the third phase (white) 6 is grounded via a 5 MΩ resistor 5 and the third phase (white) 6 is grounded via a 10 MΩ resistor 7. For this connection, for example, an IV (Indoor PVC) line having a withstand voltage of 600 V is used.

  Then, an insulation resistance meter (also referred to as a megger) 8 is sequentially connected between each phase of the cable end terminal on the other end side and the ground, and the resistance value is measured with a measurement voltage of about 100 V, so that the first phase to Confirm Phase 3. At this time, if properly connected, the ground resistance of the first phase is “0”, the ground resistance of the second phase is 1 MΩ or 5 MΩ, and the ground resistance of the third phase is 10 MΩ.

  Also, when confirming the soundness of the cable, such as connection failure, disconnection, ground fault or phase-to-phase short-circuit accident, etc., set the insulation resistance meter 8 to a measurement voltage of about 1000V. The sense meter 2 is removed and the end of the cable 1 is opened, and the insulation resistance of the cable line alone is measured.

  The cable phase check and soundness check described above must be performed not only at the terminal end of the cable 1, but also at the intermediate connection points 1a and 1b in the ground, power receiving devices, etc., and the phase of the sending substation. During construction and after construction, the above circuits are individually assembled to each terminal. Further, during construction, in order to prevent an electric shock accident or the like due to an induced current from another line to the cable 1, as a safety measure during construction, the cable construction is carried out with all phases grounded.

Japanese Utility Model Publication No. 3-125276

  As mentioned above, in underground cable work, it is necessary to check the cable phase, check the soundness of the cable, and ground the cable during the work to take safety measures, but the cable terminal (shipping substation or customer power station) ) It is necessary to attach and detach the resistors and wiring attached to), which takes time and effort.

  In addition, the operation of the power transmission / reception device is accompanied by the presence of an administrator each time.

  In addition, when checking the soundness of the cable, the frequency of switching the operation of the terminal at the end of each measurement and construction is high, and it is necessary to detach it each time.

  In addition, since many wires are used at the location where the sense meter 2 is attached, it is difficult to install differently or to take safety measures at the feet.

  The present invention has been made in view of the circumstances as described above. The purpose of the present invention is to confirm the cable phase, the soundness of the cable, and the grounding work of the cable while ensuring the safety of the worker. An object of the present invention is to provide a cable measurement mode switching device that can be simplified.

In the cable measurement mode switching device according to the present invention, the first and second resistors having different resistance values from the first to third connection terminals to which one ends of the first to third phase cables are respectively connected. And ground the first connection terminal in the first mode, and ground the second and third connection terminals via the first and second resistors, respectively, in the second mode. Switching means for setting the first to third connection terminals in an open state and grounding the first to third connection terminals in a third mode ;
When the switching means is in the first mode, an insulation resistance meter is connected to each phase on the other end side of the cable to check the cable phase. When the switching means is in the second mode, the other end side of the cable is connected. Check the soundness of the cable by connecting an insulation resistance meter to each phase, and work when the switching means is in the third mode,
The switching means is housed in the case, and a slit is formed on the side of the case, and a position confirmation member that can confirm the position of the switching means from the outside protrudes from the slit, thereby solving the above-described problem.

  In addition, the switching means includes a first changeover switch in which a first-phase cable is connected to the first movable contact, the first and second fixed contacts are grounded, and a second switch on the second movable contact. A phase change cable is connected, the third fixed contact is grounded via the first resistor, the fourth fixed contact is grounded, and the third movable contact is connected to the third phase. A third change-over switch connected to a cable, having a fifth fixed contact grounded via the second resistor, and a sixth fixed contact grounded, and in the first operation mode, The first to third movable contacts of the first to third changeover switches are connected to the first, third, and fifth connection terminals, respectively, and the first to third changeover switches are in the second operation mode. Each of the movable contacts is opened, and when the third operation mode, To third second movable contacts respectively of the switch, the fourth, that is connected to the connection terminals of the sixth and solve the problems also discussed above.

  In addition, the first to third changeover switches operate in conjunction with each other, the first to third movable contacts are connected to the first, third, and fifth fixed contacts, the open state, and The above-mentioned problem has been solved by further providing a lock mechanism that locks the second, fourth, and sixth fixed contacts in a connected state.

  In addition, the first and second variable resistance means for switching the resistance values of the first and second resistors to different values are further provided to solve the above-described problem.

  Further, the first and second variable resistance means each include a selection switch and a plurality of resistors having different resistance values, which are selected by the selection switch, thereby solving the above-described problem.

  According to the cable measurement mode switching device of the present invention, the switching phase is switched to the three circuit connection states corresponding to the first to third modes, thereby ensuring the safety of the operator and confirming the cable phase. And check the soundness of the cable and facilitate the grounding work of the cable.

  In addition, the cable phase check, cable soundness check, and cable grounding work can be performed with the switching device attached to the end of the cable, simplifying work, ensuring the safety of work personnel, preventing human errors, etc. The effect is obtained.

  Also, with the switching device attached to the terminal end of the cable, the cable phase check in the first mode, the soundness check of the cable in the second mode, and the grounding work of the cable in the third mode are performed safely and easily. be able to.

  In addition, if the switching means is composed of first to third changeover switches that operate in conjunction with each other, a reliable operation can be realized at low cost.

  Further, by providing a lock mechanism in the changeover switch, it is possible to prevent unnecessary operations and erroneous operation recognition.

  In addition, if the first and second variable resistance means are provided, the use range can be expanded.

  The first and second variable resistance means can be realized by a selection switch and a plurality of resistors having different resistance values.

It is a circuit diagram which shows the measurement mode switching apparatus of the cable which concerns on the 1st Embodiment of this invention. It is an external appearance perspective view which shows the structural example of the measurement mode switching apparatus of the cable shown in FIG. It is the perspective view which looked at the measurement mode switching device of the cable shown in Drawing 2 from the lower part. FIG. 3 is a perspective view showing an internal configuration by opening an upper lid of the cable measurement mode switching device shown in FIG. 2. (A) The perspective view which looked at the plate-shaped member which works as a lock mechanism from the bottom, (b) The figure is the perspective view which looked at the plate-shaped member from the upper part. c) The figure is a perspective view of a state where the plate-like member is mounted on the case. FIG. 5 is a perspective view illustrating a lock mechanism of the changeover switch in a state where the changeover switch is locked on the sense side. It is a perspective view of the state which is for explaining the lock mechanism of a changeover switch, and the changeover switch was locked in the open state. FIG. 5 is a perspective view illustrating a lock mechanism of the changeover switch in a state where the changeover switch is locked on the ground side. It is a side view which shows the modification of the measurement mode switching apparatus of the cable which concerns on the 1st Embodiment of this invention. It is a circuit diagram which shows the measurement mode switching apparatus of the cable which concerns on the 2nd Embodiment of this invention. It is the schematic in the case of showing the usage example of the measurement mode switching apparatus of a cable, and newly installing an underground electric line between two substations. It is for demonstrating the conventional cable phase confirmation and the soundness confirmation of a cable, and is the schematic of underground cable work.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to drawings.

  FIG. 1 is a circuit diagram showing a cable measurement mode switching device according to a first embodiment of the present invention. This device is connected to the first connection terminal 11 connected to the first phase (black) of the cable end terminal, the second connection terminal 12 connected to the second phase (red), and the third phase (white). The third connection terminal 13 is provided. These first to third connection terminals 11 to 13 are connected to the movable contacts 14a to 16a of the changeover switches 14 to 16, respectively.

  The movable contacts 14a to 16a of the changeover switches 14 to 16 are configured to be able to switch to three states in conjunction with each other, and are connected to the fixed contacts 14b to 16b in the first mode, respectively, and in the second mode. An open state (shown) is connected to the fixed contacts 14c to 16c in the third mode. Each of the change-over switches 14 to 16 is provided with a lock mechanism for preventing unnecessary operations and erroneous operations.

  The fixed contact 14 b of the changeover switch 14 is grounded, the fixed contact 15 b of the changeover switch 15 is grounded via a resistor 17, and the fixed contact 16 b of the changeover switch 16 is grounded via a resistor 18.

  The resistance value of the resistor 17 is, for example, 1 MΩ or 5 MΩ, and the resistance value of the resistor 18 is 10 MΩ. The fixed contacts 14c to 16c of the changeover switches 14 to 16 are grounded.

  In the configuration as described above, when performing measurement or work, the selector switches 14 to 16 are selectively switched to the following three states.

  That is, when the cable phase is confirmed, the movable contacts 14a to 16a of the changeover switches 14 to 16 are connected to the fixed contacts 14b to 16b (first mode). Further, when the soundness of the cable is confirmed, the movable contacts 14a to 16a are opened (second mode). During the construction, the movable contacts 14a to 16a are connected to the fixed contacts 14c to 16c (third mode), respectively.

  Thereby, in the first mode, the connection terminal 11 is grounded, and the connection terminals 12 and 13 are grounded via the resistors 17 and 18 respectively. In the second mode, the connection terminals 11 to 13 are set to the open state. Further, in the third mode, the connection terminals 11 to 13 are grounded. As described above, the changeover switches 14 to 16 function as a changeover circuit (switching means) 19 for switching the first to third modes.

  Therefore, when the cable phase is confirmed, the first phase is grounded, and the second and third phases are grounded via resistors (1 MΩ and 10 MΩ) having different resistance values. When measuring the insulation resistance for confirming the soundness of the cable, the first to third phases are all open. During the construction, the first phase to the third phase are grounded.

  In this way, by selectively switching each of the changeover switches 14 to 16 to the three states, the cable phase check, the cable soundness check, and the cable grounding work can be selectively performed with the measurement mode switching device attached. It can be implemented, and effects such as simplification of work, ensuring safety of work personnel, and prevention of human error can be obtained.

  2 to 4 show configuration examples of the cable measurement mode switching device shown in FIG. 1, respectively. FIG. 2 is an external perspective view, FIG. 3 is a perspective view seen from below, and FIG. FIG. As shown in FIG. 2, a case (casing) 21 is provided with an upper lid 22 for protecting electronic components such as internal switches, wirings, resistors, and the like. IV lines 23 to 25 for (black), second phase (red), and third phase (white) are derived.

  The connection terminals 11 to 13 are provided at the ends of the IV lines 23 to 25, respectively, and can be easily connected to various wirings and terminals. Further, a grounding (green) IV line 26 is led out from the facing surface of the case 21. In this example, the IV lines 23 to 26 having a withstand voltage of 600V are used.

  As shown in FIG. 3, rubber feet 32 a to 32 d are attached to the bottom of the case 21, and slit-shaped openings 31 a to 31 d are provided on opposite side surfaces near the bottom. These openings 31a to 31d are for attaching and fixing the switching device to the member through a belt made of metal, rubber, resin or the like.

  As shown in FIG. 4, the case 21 accommodates the changeover switches 14 to 16, the resistors 17 and 18, wiring for connecting them, and the like. In this example, a knife switch 20 with a cover for three phases is used for the changeover switches 14-16.

  The knife switch 20 can be switched similarly to the switching circuit 19 in FIG. The IV lines 23 to 26 are connected to the electrodes 27 to 30, respectively. The knife switch 20, the resistors 17, 18 and the IV lines 23 to 26 realize the circuit connection as shown in FIG.

  The knife switch 20 is equipped with a lock mechanism. As shown in FIGS. 5 (a) and 5 (b), this locking mechanism is composed of a plate member 35 having an opening 35a for projecting the knob portion 20a of the knife switch 20, and screws 36 and 37. . Here, a transparent acrylic plate is used as the plate-like member 35.

  As shown in FIG. 5A, screws 36 and 37 are disposed on the plate-like member 35 constituting the lock mechanism in an inclined manner with a predetermined interval. As shown in FIGS. 4 and 5C, the screws 36 and 37 of the plate-like member 35 are arranged in an inclined manner with a predetermined interval in order to fix the cover on the knife switch 20 side. The screw holes 20b and 20c are inserted.

  Specifically, as shown in FIGS. 5B and 5C, in the state where the screws 36 and 37 of the plate-like member 35 are arranged on the lower side, the screw 36 of the plate-like member 35 is connected to the knife switch 20 side. The screw 37 of the plate-like member 35 is inserted into the screw hole 20c on the knife switch 20 side.

  By attaching the upper lid 22 to the case 21 in this state, the upward movement of the plate-like member 35 is restricted, and the knob portion 20a of the knife switch 20 is locked.

  If the screws 36 and 37 of the plate-like member 35 are screwed into the screw holes 20b and 20c on the knife switch 20 side, the plate-like member 35 is more firmly attached to the knife switch 20 portion. This is preferable for locking the knob portion 20a.

  FIG. 6 shows a state in which the knife switch 20 is switched to the sense side (a state used as a sense meter for checking the phase of the cable) and locked, and the knob portion 20a of the knife switch 20 is covered with a plate-like member 35. Switching operation is prohibited.

  FIG. 7 shows a state in which the knife switch 20 is locked in an open state (a state used for checking the soundness of the cable), and the knob portion 20a of the knife switch 20 is fixed in the opening 35a so that the switching operation can be performed. prohibited.

  FIG. 8 shows a state in which the knife switch 20 is switched to the ground side (a state in which all phases are grounded) and locked, and the knob switch 20a of the knife switch 20 is covered with a plate-like member 35 to switch the state. Operation is prohibited.

  According to the above configuration, the circuit shown in FIG. 1 can be realized with a simple structure and at a low cost. Moreover, the state of the knife switch 20 can be visually confirmed by using a transparent acrylic board as the plate-shaped member 35 which comprises a locking mechanism. For example, by marking “sense side”, “grounding side” or the like on the side surface of the knob portion 20a in the knife switch 20, it is possible to prevent erroneous operation more reliably by visually checking this.

  FIG. 9 shows a modification of the above-described first embodiment, in which a fan-shaped slit 46 is provided on the side surface of the case 21 so that the position of the knob portion 20a of the knife switch 20 can be confirmed from the outside. It is. The knob 20 a of the knife switch 20 is provided with a protrusion protruding into the slit 46 and a bar-like position confirmation member 47.

  According to such a configuration, the position confirmation member 47 moves in accordance with the operation of the knife switch 20, as indicated by the arrow in FIG. Therefore, even when used with the upper lid 22 closed as shown in FIG. 2, the position of the knob portion 20a of the knife switch 20 can be visually confirmed from the outside, and the usability can be improved.

  Further, the first to third modes may be displayed mechanically linked to the knife switch 20. Of course, if the upper lid 22 of the case 21 is formed of a transparent material so that the inside can be visually confirmed, even when the upper lid 22 is used in a closed state, the display function is unnecessary and the waterproofness is improved. be able to.

  FIG. 10 is a circuit diagram showing a cable measurement mode switching device according to the second embodiment of the present invention. In the first embodiment, the case where the resistors 17 and 18 have fixed resistance values has been described as an example. However, in the second embodiment, the resistance values of the resistors 17 and 18 are set. Make it variable. 10, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  That is, the plurality of resistors 38 to 40 having different resistance values are selected by the selection switch 44, and the plurality of resistors 41 to 43 having different resistance values are selected by the selection switch 45. Thereby, it can be used as variable resistance means whose resistance value changes. In this example, the resistance values of the resistors 38 to 40 are 1 MΩ, 5 MΩ, and 10 MΩ, respectively, and the resistance values of the resistors 41 to 43 are 1 MΩ, 5 MΩ, and 10 MΩ, respectively.

  In this manner, by selecting the plurality of resistors 38 to 43 having different resistance values by the selection switches 44 and 45, the use range can be expanded and versatility can be enhanced.

  In the first and second embodiments described above, an example in which the changeover switch is configured by using the mechanical knife switch 20 to form the changeover circuit 19 is shown. However, a semiconductor switch such as a thyristor or a power transistor, or A similar circuit can be configured using a relay.

  In this case, by providing a control circuit for controlling the operation of the semiconductor switch, measurement and switching can be automated, and notification of each mode by lighting an LED or the like is also possible.

  Next, underground cableway construction using the cable measurement mode switching device as described above will be described with reference to FIG. Here, an example in which cables 53-1 to 53-3 are newly provided between the substation 51 and the substation 52 (when matching is performed on the substation 51 side) will be described. Both substations 51 and 52 are terminated in the air, and the cables 53-1 to 53-3 use 66KV CVT (Triplex-type cross-linked polyethylene vinyl sheath cable).

  First, the cables 53-1 to 53-3 are pulled into the laying place. In this example, the end terminal on one end side of the cable 53-3 is laid on the ground of the substation 52, and the end terminal on the other end side is laid in the pipeline or the cave. Further, the cable 53-2 is laid in a pipeline or a sinus, the terminal end on one end side of the cable 53-1 is laid on the ground of the substation 51, and the terminal end on the other end side is laid in the conduit or a sinus. doing.

  After the installation of the cables 53-1 to 53-3, the terminal terminal of the cable 53-3 on the substation 52 side is connected. After the connection is completed, the above-described cable measurement mode switching device 100 of the present invention is attached to the end of the cable 53-3.

  Next, for example, in the manhole, the cables 53-3 and 53-2 are connected at the intermediate connection point 53a on the substation 52 side. At this time, before connecting the cable, the switching device 100 is set to the first mode to check the phase of the cable 53-3, and the first phase (black), the second phase (red), and the third phase (white) are set. Work after displaying. In this connection operation, the switching device 100 is set to the third mode, and the operation is performed with all phases grounded.

  After the connection is completed, the switching device 100 is set to the first mode, and phase confirmation is performed before the connection at the intermediate connection point 53b side at the substation 51 side. In the phase confirmation, the insulation resistance meter 200 is sequentially connected between each phase of the terminal end of the cable 53-2 at the intermediate connection point 53b and the ground, and the resistance value is measured with a measurement voltage of about 100 V, so that the first phase to Confirm Phase 3. If properly connected, the ground resistance of the first phase is “0”, the ground resistance of the second phase is 1 MΩ or 5 MΩ, and the ground resistance of the third phase is 10 MΩ. After the phase confirmation is completed, the switching device 100 is set to the third mode and all phases are grounded.

  Next, the cables 53-2 and 53-1 are connected at the intermediate connection point 53b on the substation 51 side. Also in this case, before the connection of the intermediate connection point 53b, the switching device 100 is set to the first mode, the phase of the cable 53-2 is confirmed, and the first phase to the third phase are displayed and then connected. At the time of connection, the switching device 100 is set to the third mode, and the work is performed with all phases grounded.

  Next, the end terminal connection of the cable 53-1 is performed on the ground on the substation 51 side. Also in this case, the switching device 100 is set to the first mode before the connection, the phase of the terminal terminal of the cable 53-1 is confirmed, and the first phase to the third phase are displayed and then connected. At the time of connection, the switching device 100 is set to the third mode, and the work is performed with all phases grounded.

  After the end-terminal connection is completed, phase confirmation is performed through the entire section of the newly installed cable. In the phase confirmation, the insulation resistance meter 200 is sequentially connected between each phase of the terminal end of the cable 53-1 and the ground on the substation 51 side ground, and the resistance value is measured with a measurement voltage of about 100V. Confirm Phase 1 to Phase 3.

  If properly connected, the ground resistance of the first phase is “0”, the ground resistance of the second phase is 1 MΩ or 5 MΩ, and the ground resistance of the third phase is 10 MΩ. After the phase confirmation is completed, the switching device 100 is set to the third mode and all phases are grounded.

  Then, the switching device 100 is set to the second mode and all phases are opened. In this state, the insulation resistance meter 200 is set to a measurement voltage of about 1000 V for each phase at the terminal end of the cable 53-1 on the substation 51 side, and the cable insulation resistance is measured to confirm the soundness of the cable. After the confirmation, the switching device 100 is set to the third mode and all phases are grounded.

  Thereafter, the measurement mode switching device 100 is removed. Then, the entire cable is subjected to a power-charging test (trial charge), and after all inspections are completed, power is applied to start use.

  In this way, it is no longer necessary to directly touch the line when checking the cable phase, and the cable phase check is grounded or resistance grounded and is not measured in an open state. Can improve safety. Moreover, since it can be implemented by the changeover operation of the changeover switch, the device can be attached and detached only at the time of installation at the start of construction and at the time of removal after the completion of construction.

  In addition, since work and attendance during the middle of construction can be omitted and the changeover operation can be performed, the work time can be reduced, the number of workers can be reduced, and a human error (attachment error) can be prevented when attaching / detaching the sense meter. Furthermore, it is possible to check the soundness of the cable while the switching device is connected.

  In addition to the case where a new underground power line is installed between the two substations described above, when an existing power receiving facility is switched to the new power receiving facility, for example, in order to replace a part of the cable due to an accident, etc. The present invention can be similarly applied to a case where a part of the facility is newly installed, and the same effect can be obtained.

  The cable measurement mode switching device according to the present invention can be used in underground cable work for checking the cable phase, checking the soundness of the cable, and grounding the cable during the work to take safety measures.

1 ... Cable (ground cableway)
DESCRIPTION OF SYMBOLS 1a ... Intermediate connection location 1b ... Intermediate connection location 2 ... Sense meter 3 ... 1st phase (black)
4 ... Second phase (red)
5 ... Resistor 6 ... Third phase (white)
DESCRIPTION OF SYMBOLS 7 ... Resistor 8 ... Insulation resistance meter 11 ... Connection terminal 12 ... Connection terminal 13 ... Connection terminal 14 ... Changeover switch 15 ... Changeover switch 16 ... Changeover switch 14a ... Movable contact 15a ... Movable contact 16a ... Movable contact 14b ... Fixed contact 15b ... Fixed contact 16b ... Fixed contact 14c ... Fixed contact 15c ... Fixed contact 16c ... Fixed contact 17 ... Resistor 18 ... Resistor 19 ... Switching circuit (switching means)
DESCRIPTION OF SYMBOLS 20 ... Knife switch 20a ... Knob part 20b ... Screw hole 20c ... Screw hole 21 ... Case 22 ... Upper lid 23 ... IV wire 24 ... IV wire 25 ... IV wire 26 ... IV wire 27 ... Electrode 28 ... Electrode 29 ... Electrode 30 ... Electrode 31a ... Opening 31b ... Opening 31c ... Opening 31d ... Opening 32a ... Rubber feet 32b ... Rubber feet 32c ... Rubber feet 32d ... Rubber feet 35 ... Plate members 35a ... Opening 36 ... Screw 37 ... Screw 38 ... Resistors DESCRIPTION OF SYMBOLS 39 ... Resistor 40 ... Resistor 41 ... Resistor 42 ... Resistor 43 ... Resistor 44 ... Selection switch 45 ... Selection switch 46 ... Slit 47 ... Position confirmation member 51 ... Substation 52 ... Substation 53-1 ... Cable ( Underground cableway)
53-2. Cable (underground cableway)
53-3 ... Cable (underground cableway)
53a ... Intermediate connection point 53b ... Intermediate connection point 100 ... Cable measurement mode switching device 200 ... Insulation resistance meter

Claims (5)

First to third connection terminals to which one ends of first-phase to third-phase cables are respectively connected, first and second resistors having different resistance values, and the first connection in the first mode The terminal is grounded, the second and third connection terminals are grounded via the first and second resistors, respectively, and the first to third connection terminals are opened in the second mode. Switching means for setting and grounding the first to third connection terminals in the third mode ,
When the switching means is in the first mode, an insulation resistance meter is connected to each phase on the other end side of the cable to check the cable phase. When the switching means is in the second mode, the other end side of the cable is connected. Check the soundness of the cable by connecting an insulation resistance meter to each phase, and work when the switching means is in the third mode,
A cable measurement mode switching device, characterized in that a switching means is accommodated in the case, a slit is provided on the side of the case, and a position confirmation member that can confirm the position of the switching means from the outside protrudes from the slit .   The switching means includes a first changeover switch in which a first phase cable is connected to the first movable contact, the first and second fixed contacts are grounded, and a second phase cable to the second movable contact. Is connected, the third fixed contact is grounded via the first resistor, the fourth fixed contact is grounded, and the third phase cable is connected to the third movable contact. A third changeover switch having a fifth fixed contact grounded via the second resistor and a sixth fixed contact grounded, and wherein the first to the second operation switches in the first operation mode. The first to third movable contacts of the three changeover switches are connected to the first, third, and fifth connection terminals, respectively, and the movable contacts of the first to third changeover switches when in the second operation mode. Are in an open state, and the first to the second are at the time of the third operation mode. The second movable contact, each of the switch, the fourth, and being connected to the connection terminal of the sixth, measuring mode switching device of a cable according to claim 1.   The first to third changeover switches operate in conjunction with each other, the first to third movable contacts being connected to the first, third, and fifth fixed contacts, the open state, and the first The cable measurement mode switching device according to claim 2, further comprising a lock mechanism that locks the second, fourth, and sixth fixed contacts in a connected state.   The cable measurement mode switching device according to claim 1, further comprising first and second variable resistance means for switching the resistance values of the first and second resistors to different values, respectively. .   5. The cable measurement according to claim 4, wherein each of the first and second variable resistance means includes a selection switch and a plurality of resistors having different resistance values selected by the selection switch. Mode switching device.

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