JP3418255B2 - AC current detection display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC follow-up current that accompanies the occurrence of a dielectric breakdown due to a lightning strike on a transmission line tower, an overhead ground line, a distribution line, a train line, etc. The present invention relates to an alternating current detection indicator for detecting and displaying an alternating current leaked due to insulation breakdown of a power distribution device due to some cause.

[0002]

2. Description of the Related Art A lightning arrester is installed in order to prevent insulation breakdown of equipment from a lightning surge current caused by a lightning strike. If this lightning arrestor works satisfactorily, the lightning surge current is properly discharged and discharged to the ground, and when this is completed, the AC follow-up accompanying it (because of the lightning surge current, the current continues to flow thereafter). AC current) is immediately shut off, and no trouble occurs. However, if the lightning arrestor does not function sufficiently due to a failure or the like, there is a case where the AC follow-up current cannot be immediately interrupted due to a breakdown of the device due to a lightning surge current.

[0003]

A technique for detecting and displaying a transmission line tower or a concrete column that has been flashed due to a lightning strike is known, for example, as disclosed in Japanese Utility Model Laid-Open No. 4-79268. is there. However, simply receiving a lightning strike does not cause any trouble due to the action of the arrester. The problem is whether or not the device has a dielectric breakdown due to a lightning surge current, and it is important to detect and display the AC follow-up current associated with the dielectric breakdown.

Therefore, the applicant of the present patent application also discloses a technique for detecting only the AC follow current without detecting the lightning surge current.
Proposed in No. 93590. To briefly explain this technique, a CT sensor in which a voltage is induced by an AC follow current is provided, and the induced voltage is rectified to charge a capacitor,
The solenoid operates when the capacitor reaches a predetermined voltage.

In such a structure, C is applied to the lightning surge current.
The solenoid does not operate without saturation of the T-sensor and generation of high induced voltage. However, a high induced voltage is generated without being saturated with the AC follow-up current, and the AC follow-up current is 30 to 40 m.
If it continues for sec, the solenoid operates. As for the indication of detection, the display member is appropriately hung depending on the operation of the solenoid.

The above-mentioned technique is excellent in that it can detect only the AC follow-up current, but it requires a solenoid, a rectifying circuit, and the like as constituent elements, and is accordingly expensive.

The present invention has been made to improve the prior art, and an object thereof is to provide an alternating current detection display which has an extremely simple structure, is suitable for mass production, and can be manufactured at low cost.

[0008]

In order to achieve such an object, an AC current detection display of the present invention is a mass armature which is swingable around a horizontal swing axis, and the mass armature is attracted to a predetermined posture. A permanent magnet to be held, a display member that is engaged with the mass armature in the predetermined posture to prevent the mass armature from falling, and the mass armature is released from the predetermined posture with a rotation torque weaker than the attraction and holding by the permanent magnet. Disengagement urging means for urging the induction coil, an induction coil in which a voltage is induced by an alternating current, and a degaussing coil wound around the magnetic path of the permanent magnet and applied with an induction voltage in the induction coil, It consists of

Further, the induction coil may be fixed to a leg of a steel tower or a concrete column through which an alternating current to be detected can flow, by a holding member made of a magnetic material that penetrates the induction coil.

Further, the induction coil may be a CT sensor.

Further, the mass armature has a V-shape having a large opening angle with the opening facing upward, the swing shaft is disposed at the refraction point, and the display is provided at one free end of the V-shape. The member may be engaged and the other free end may be elastically biased by a spring in a direction of releasing the engagement.

Further, the mass armature, the permanent magnet, the display member in a state in which the drop is prevented, the engagement releasing biasing means, and the degaussing coil are housed in the housing, and when the engagement is released, the display member is It can also be configured to fall outside the housing by a predetermined amount to be in a suspended state.

Further, a pair of test terminals may be provided on the outer surface of the housing, and the pair of test terminals may be electrically connected to both ends of the degaussing coil.

Further, there is provided an operation rod capable of rotating the mass armature from the state in which the predetermined posture attracted and held by the permanent magnet is released to the state in the predetermined posture, and one end of the operation rod is It is also possible to project from the housing and rotate the mass armature from the outside of the housing.

[0015]

[Operation] Normally, the mass armature is attracted and held by the permanent magnet, and the display member cannot fall. The lightning surge current has a duration of only several tens of microseconds, and even when the induced voltage induced by the induction coil is applied to the degaussing coil during that time, the magnetic field of the permanent magnet is offset and the attraction force is reduced. , It cannot operate instantaneously due to the inertia of the mass armature, and due to this operation delay, it cannot respond to the lightning surge current. However, as long as the magnetic field of the permanent magnet is canceled by the AC follow-up current that flows continuously after that due to the lightning surge current or the AC current that leaks from the distribution equipment whose insulation has been broken down for some reason, In the meantime, the attitude of the mass armature is changed by the disengagement urging means, and the display member can be disengaged and fall.

Further, if the induction coil is fixed to the legs of a steel tower or a concrete column with a holding member made of a magnetic material, this holding member serves as a magnetic path for a magnetic flux generated by an alternating current flowing through the legs or the column to induce the induction coil. An induced voltage can be efficiently generated in the coil.

If the induction coil is used as a CT sensor, only this CT sensor is installed at an appropriate position such as a steel tower or a pillar, and is connected to a main body provided at an appropriate position different from this by a lead wire. Good and free installation is possible.

If the mass armature is V-shaped and the display member is engaged with one free end of the mass armature, the engagement structure can be easily formed by providing a simple protrusion or the like on the display member.

Further, if the display member falls out of the housing when the engagement is released so as to be in a suspended state,
It can be used repeatedly by reengaging the display member with the mass armature in the housing.

Further, if a pair of test terminals electrically connected to the degaussing coil are provided on the outer surface of the housing,
By applying a DC voltage to the pair of test terminals so that the degaussing coil produces a magnetic field in a direction that cancels the AC voltage or the magnetic field of the permanent magnet, the test operation of operating the mass armature and dropping the display member is simple. Get to.

If an operation rod is provided so that the mass armature can be rotated from the outside of the housing to a predetermined posture in which it is attracted and held by a permanent magnet, the AC current detection indicator of the present invention detects an AC current. Alternatively, after the display member is dropped by the test operation, by operating the operation rod and pushing up the display member, the device can be set again to a state in which an alternating current can be detected.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a structural view of an embodiment of an alternating current detection display of the present invention with a housing cut away.
[Fig. 6] is a view for explaining the action of the degaussing coil. In the description of the embodiment, the AC follow current is detected.

In FIG. 1, a mass armature 14 is swingably arranged in a housing 10 by a horizontally swinging shaft 12. The mass armature 14 is made of a ferromagnetic material such as iron, and has a swing shaft 12 provided in a refraction point and has a V-shape with an opening directed obliquely upward and has a large opening angle, for example, 100 to 140. °. Further, the arm lengths of the mass armature 14 opened in the V shape are, for example, 15 to 25 mm, both of which are equal. Moreover, the attracting portion 14a is provided on the V-shaped outer portion of the mass armature 14, and the magnetic attracting and holding portion including the permanent magnet 16 and the magnetic paths 18 and 18 is provided facing the attracting portion 14a. The attracting portion 14a is attracted and held by the magnetic attracting and holding portion, and the mass armature is maintained in a predetermined posture.

A display member 20 is provided in the housing 10 so as to be freely dropped by its own weight, and both surfaces thereof are painted red as an example. A protrusion 20a is provided on the back surface of the display member 20, and one free end of the mass armature 14 in a predetermined posture is engaged with the protrusion 20a to prevent the protrusion due to its own weight. It should be noted that the housing 1 has an opening 1 through which the display member 20 can pass, but the protrusion 20a cannot pass.
0a is provided, and the protrusion 20a is caught on the bottom of the housing 10 to limit the drop of the display member 20 by a predetermined amount.

At the other free end of the mass armature 14, a spring 22 is provided as a disengagement biasing means so as to swing the mass armature 14 in the direction opposite to the direction of attraction by the magnetic attraction holder. To be done. The spring constant of the spring 22 is, for example, 1 to 5 g / mm, and the mass armature 14 is set so that the rotation torque of the mass armature 14 by the spring 22 is somewhat smaller than the rotation torque by the magnetic attraction by the magnetic attraction holder. 14
The arm length (for example, 20 mm) and the elastic extension amount of the spring 22 are set.

Further, a degaussing coil 24 is wound around one magnetic path 18. An induction coil 26 is provided in the housing 10, and a window 10b formed on the back side surface of the housing 10
The induction coil 26 is fixedly arranged along the leg portion 30 of the steel tower by the belt 28 as a holding member made of a ferromagnetic material such as soft iron. The belt 28 penetrates the induction coil 26 as shown in FIG.
Fix 0 as well. The lead wire 32 is electrically connected so that the induced voltage induced in the induction coil 26 is applied to the degaussing coil 24. In addition, instead of the legs 30 of the steel tower, the induction coil 2 is provided on a concrete column with a reinforcing bar through which an alternating current leaking due to insulation breakdown of a power distribution device flows.
6 may be provided.

Further, the casing 10 has a skirt shape in which the lower end of the side plate projects downward from the bottom plate and is opened slightly outward, so that rainwater, snow, dust or the like does not enter the casing 10 through the opening 10a. Is formed.

In this structure, normally, no current flows through the degaussing coil 24, and the magnetic field of the permanent magnet 16 holds the mass armature 14 in the predetermined posture shown in FIG.
One of the free ends is engaged with the protrusion 20a of the display member 20,
The display member 20 is stored in the housing 10.

When the AC follow-up current I flows through the leg portion 30 of the steel tower, the mass armature 14 changes its predetermined posture to drop the display member 20 for the following reason. First, a magnetic flux passing through the belt 28 is generated by the AC follow current I, which causes an induced voltage in the induction coil 26, which is applied to the degaussing coil 24. Then, a magnetic field as shown by the solid line in FIG. 2 is generated in the magnetic path 18 by the degaussing coil 24, and this is superposed on a constant magnetic field as shown by the broken line in FIG. 2 by the permanent magnet 16. Then, as shown by the alternate long and short dash line in FIG. 2, a period T of a small magnetic field occurs. During this period T, the suction holding force is small and the rotation torque by the spring 22 is superior. Then, this period T is several msec, the rotational torque reaches the inertia, the mass armature 14 swings, and the engagement of the protrusion 20a of the display member 20 is released. As a result, the display member 20 falls and the detection of the AC follow current is displayed.

However, with respect to the lightning surge current, the mass armature 14 does not change its predetermined posture because of the following reasons. First, the lightning surge current usually has a duration of only several tens of microseconds, and even if the force for attracting and holding the mass armature 14 decreases during that time, even if the spring 22 is elastically biased by the inertia of the mass armature 14. However, such a rapid operation cannot be performed and a delay occurs, and during this delay, the lightning surge current disappears, and the mass armature 14 is adsorbed and held again. Further, the induction coil 26 is saturated by a too steep lightning surge current, a high induced voltage is not generated, the magnetic field generated by the degaussing coil 24 is small, and the magnetic field generated by the permanent magnet 16 cannot be canceled.

When the AC follow-up current I is detected and displayed, and the inspection and repair of the equipment are completed, the display member 20 is pushed up into the housing 10 again and the mass armature 14 is pressed.
By rotating the to a predetermined posture, the protrusion 20a is engaged with one free end of the mass armature 14 in the predetermined posture. Therefore, it can be used repeatedly.

If the V-shaped opening angle of the mass armature 14 is too small, when the arm to which the spring 22 is attached is horizontal, the tip of the other arm engages with the projection 20a of the display member 20. It is difficult to prevent the fall. If the opening angle is too large, the housing 1
When the dimension of 0 is constant, the vertical distance from the swing shaft 12 to the protrusion 20a of the display member 20 with which the mass armature 14 engages becomes short, and when the display member 20 falls, the housing 10 Display member 2 that is hung from the outside
The size of 0 becomes short and it becomes difficult to recognize the display.

If the spring constant of the spring 22 is too small, the mass armature 14 can be oscillated and displaced from a predetermined posture in a short period T when the magnetic field of the permanent magnet 16 is canceled by the magnetic field of the degaussing coil 24. Can not. If the spring constant is too large, the mass armature 1
The magnetic field of the permanent magnet 16 necessary for maintaining the No. 4 in a predetermined posture must be large, and the magnetic field of the degaussing coil 24 required to cancel this must also be large. However, the magnitude of the magnetic field that can be generated in the degaussing coil 24 is restricted by the magnitude of the AC follow current I to be detected. Therefore, too large a spring constant is not practical.

FIG. 3 is a structural view showing another embodiment of the alternating current detection indicator of the present invention. The induction coil 26 in the housing 10 is omitted, the housing 10 for accommodating the main body is arranged at a height where the legs 30 of the steel tower are easy to work, and the CT sensor 34 as the induction coil 26 is the feet of the steel tower. The CT sensor 34 and the degaussing coil 24 in the housing 10 are appropriately electrically connected to each other by a lead wire 32, which is arranged at an appropriate position where the AC follow-up current I of the portion 30 can flow. In another embodiment shown in FIG. 3, C
Since the T sensor 34 and the housing 10 can be provided at different locations, both the detection of the AC follow-up current I at an appropriate position, the confirmation of the display, and the installation of the housing 10 at a position where the operation is easy are achieved. it can. In the CT sensor 34, a ring 36 made of a magnetic material and which can be divided into two is fitted in a current flow path such as a leg portion 30 of an iron tower through which the AC follow current I flows, and a detection coil 38 is wound around the ring 36. It is a structure.

Still another embodiment of the present invention is shown in FIG.
It will be described with reference to FIGS. FIG. 4 is an external perspective view of still another embodiment of the alternating current detection display of the present invention, FIG. 5 is a structural view of a main part excluding a display member, and FIG. 6 is a mass armature and a display. It is a perspective view which shows the engagement of a member. 4 to 6, members that are the same as or equivalent to those in FIG. 1 are given the same reference numerals and redundant description will be omitted.

In yet another embodiment shown in FIGS. 4 to 6, the AC current detection display of the present invention can be made thin. As shown in FIG. 4, the housing 10
Is relatively thin, and an attachment auxiliary member 10c having a through hole is provided at the upper end thereof, and is hooked on a bolt 30a or the like protruding from the leg portion 30 of the steel tower. Further, windows 10b, 10b are provided on the side surface of the housing 10, a belt 28 made of a ferromagnetic material penetrates the housing 10, and the housing 10 is fixedly arranged on the leg portion 30 of the steel tower. Further, a pair of test terminals 40, 40 is provided on the side surface of the housing 10.

Further, the mass armature 14 has a housing 10
A swing shaft 12 which is horizontal in the front-rear direction is swingably disposed therein. Then, the attraction portion 14a provided so as to project from the mass armature 14 is attracted and held by the magnetic attraction holding portion that attracts in the lateral direction, and the mass armature 14 is maintained in a predetermined posture.

Then, one free end of the mass armature 14 engages with the projection 20a bent toward the back at the upper end of the display member 20 to prevent the display member 20 from falling. A spring 22 is arranged at the other free end of the mass armature 14 so as to swing the mass armature 14 in the direction opposite to the direction of attraction by the magnetic attraction holder. Further, the other free end of the mass armature 14 is engaged with one end of the operating rod 42 and hangs down. The other end of the operating rod 42 projects from the lower end of the housing 10. By pushing up the other end of the operating rod 40, the mass armature 14 is rotated against the elasticity of the spring 22 to be attracted. The portion 14a can be attracted and held by the magnetic attraction holder.

Further, the pair of test terminals 40, 40 provided on the side surface of the housing 10 are electrically connected to both ends of the degaussing coil 24 by lead wires 44, 44.

The induction coil 26 is arranged at a position along with the belt 28 arranged so as to pass through the housing 10.

In yet another embodiment of such a structure, the AC follow-up current I flows through the leg portion 30 of the steel tower, and the induction coil 2
When an induced voltage is generated in 6, a magnetic field is generated by the degaussing coil 24, the magnetic field of the permanent magnet 16 is canceled to generate a small period of the magnetic field, the mass armature 14 swings, and the display member 20 falls. This is the same as the embodiment shown in FIG.

However, since the mass armature 14 is structured to swing laterally by the swing shaft 12 which is horizontal in the front-rear direction, the mass armature 14 and the display member 20.
The thickness of the structure in which the and are overlapped in the front-rear direction is thin, and the AC current detection display of the present invention can be configured to be relatively thin.
Further, by providing the test terminals 40, 40, by applying an appropriate AC voltage to the pair of test terminals as a test operation, an AC magnetic field can be generated in the degaussing coil 24, and the mass armature 14 can be produced. Can be appropriately swung to check whether the display member 20 falls.
The test operation can be performed even if a DC voltage is applied to the pair of test terminals 40, 40 with a polarity that causes the magnetic field of the demagnetizing coil 24 to cancel the magnetic field of the permanent magnet 16.
In the test operation of applying the DC voltage, a dry battery or the like can be used as the DC voltage source, and the test can be performed very easily.

Further, by pushing up the operation rod 42 from the outside of the housing 10, the mass armature 14 is resisted against the elasticity of the spring 22 and the magnetic attraction holding portion is attracted to the magnetic attraction holding portion 14.
It can be easily rotated to a predetermined posture in which a is adsorbed and held. Therefore, after detecting the AC follow-up current I or after the test operation, the display member 20 is pushed up and the operation rod 42
The device can be set to a state in which the AC follow-up current I can be detected again by operating.

In the above embodiment, the other free end of the mass armature 14 and the spring 22 form the engagement releasing biasing means. However, instead of the spring 22, a weight having an appropriate weight may be used. good. And the spring 22
Is not limited to the tension spring as in the embodiment, but may be formed by a compression spring, a spring, or the like. Further, a constant force spring or the like is also suitable. Further, the belt 28 as a holding member
Is not limited to a belt-shaped one, as long as it can efficiently generate an induced voltage in the induction coil 26 with the magnetic flux generated by the AC follow-up current I and fix the housing 10.

The magnetic attraction holder is not limited to the permanent magnet 16 and the magnetic paths 18, 18 as in the embodiment, but may be an I-shaped, U-shaped or U-shaped permanent magnet. . Further, the display member 20 is not limited to the one that is dropped by its own weight, and the display member 20 may be surely dropped and brought into a suspended state when the engagement is released by an appropriate spring or the like. Further, the mass armature 14 is not limited to the substantially V shape, and may have any shape as long as it has an appropriate mass, is provided with the suction portion 14a, and is provided with the engagement releasing means.

In addition, the induction coil 26 or CT
The sensor 34 is not limited to the one that detects the AC follow-up current I flowing through the leg portion 30 of the steel tower or the concrete column, and may be installed so as to detect any alternating current. For example, in FIG.
As shown in Fig. 3, the ring 3 made of a magnetic material is attached to the overhead ground wire 50.
6 may be fitted and the CT sensor 34 in which the detection coil 38 is wound may be provided, and the alternating current flowing through the overhead ground wire 50 may be detected by the alternating current detection indicator of the present invention. Further, the CT sensor 34 may be provided on the ground conductor of the lightning arrestor to detect a fault current of the lightning arrester.

Further, in another embodiment shown in FIGS. 4 to 6, if the bolt 30a is appropriately provided on the leg portion 30 of the steel tower, the through hole of the attachment auxiliary member 10c should be inserted therein. It ’s good, but a suitable bolt 30 for the leg 30 of the tower
If a is not projected, an appropriate hole is formed in the leg portion 30 of the steel tower, and the hole of the leg portion 30 and the auxiliary mounting member 10c are attached.
The through hole may be fixed by tightening the bolt and the nut together. Furthermore, if the alternating current detection indicator of the present invention is arranged on a concrete pillar or the like, a belt is wound around the concrete pillar or the like, and a bolt is projected on the belt or the belt and the attachment auxiliary member 10c are used as bolts. You may fix with a nut. Further, the AC current detection indicator of the present invention may be held on the leg portion 30 of the tower by the belt 28 without using the attachment auxiliary member 10c. Moreover, the attachment auxiliary member 10c may be integrated with the housing 10 or may be formed as a separate member, or may not be provided. If it is a separate member, it can be detachably attached to the housing 10. It may be configured.

[0048]

As described above, since the alternating current detection display device of the present invention is constructed, the following special effects are obtained.

In the alternating current detection indicator according to the first aspect, the lightning surge current is not detected, but it is detected with respect to the alternating current following the lightning surge current, and the alternating current leaking from the distribution equipment is detected. It is detected and displayed. Further, it has a simple structure, does not require a power source such as a battery, can be manufactured at low cost, and can be maintained at low cost.

Further, in the alternating current detection indicator according to the second aspect, the holding member can efficiently generate an induced voltage in the induction coil by the alternating current flowing through the legs of the steel tower or the concrete column. The reliable detection of alternating current is possible. Moreover, the AC current detection indicator can be fixed by this holding member, and the installation work is simple.

Further, in the alternating current detection indicator according to the third aspect of the present invention, since the housing for accommodating the CT sensor and the main body can be installed at different positions, it is an optimum position for detecting the alternating current. The CT sensor is provided in the housing, and the housing is provided in a safe position where the display can be confirmed and the work is easy, and proper detection and easy and safe work can be obtained, which is suitable for maintenance management.

Further, in the alternating current detection indicator according to the fourth aspect, the engaging structure for engaging the display member by the mass armature to prevent the falling is extremely simple, and the entire structure is simple. Therefore, it can be mass-produced at low cost.

Further, in the alternating current detection indicator according to the fifth aspect, after the alternating current is detected, if the display member is pushed up into the housing, it can be engaged with the mass armature, which is repeated. It is possible to use.

Further, in the alternating current detection indicator according to the sixth aspect, by applying an alternating voltage or a direct voltage having a proper polarity to the test terminal, the mass armature is swung to drop the display member. Can be made. Therefore, it is possible to easily test whether or not this device can operate properly, and maintenance is easy. Moreover, if a test operation is performed by applying a DC voltage to the test terminal, a dry battery or the like can be used as the DC voltage source, and the test operation is extremely easy.

Further, in the alternating current detection indicator according to the seventh aspect of the present invention, the display member is pushed up and the operation rod is operated from the state in which the device detects the alternating current or the test operation is performed and the display member falls. By doing so, the device can be set to a state in which the alternating current can be detected again, and its operation is easy for repeated use.

[Brief description of drawings]

FIG. 1 is a structural view in which a housing of an embodiment of an alternating current detection display of the present invention is cut away.

FIG. 2 is a diagram for explaining the action of a degaussing coil.

FIG. 3 is a structural diagram showing another embodiment of the alternating current detection indicator of the present invention.

FIG. 4 is an external perspective view of still another embodiment of the alternating current detection indicator of the present invention.

FIG. 5 is a structural diagram of a main part excluding a display member.

FIG. 6 is a perspective view showing the engagement between the mass armature and the display member.

FIG. 7 is a structural diagram of an example of an alternating current detection display of the present invention in which a CT sensor is provided on an overhead ground wire.

[Explanation of symbols]

10 housing 10a opening 10b window 12 swing axis 14 Mass Armature 14a adsorption part 16 permanent magnet 18 magnetic path 20 Display member 20a protrusion 22 spring 24 Degaussing coil 26 induction coil 28 belts 30 Steel tower legs 32,44 lead wires 34 CT sensor 40 test terminals 42 Operation rod

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Liang Jiangdong Wuhan City, Hubei Province, Wuhan City, Hubei Province (No Address) Wuhan High Voltage Research Institute, New Technology Corp. (72) Inventor, Guo Ke Wu, Hubei Province, People's Republic of China City Wu Chang Lu (No house number) Wuhan High Voltage Research Institute New Technology Ltd. (72) Inventor Lee Ken-Ken Wuhan City, Hubei Province, People's Republic of China Wu Chang City Wuhan City Research Institute New Technology Ltd (72) ) Inventor Xiang Qingqing Wuchang Mountain, Wuhan City, Hubei Province, People's Republic of China (No address) Inside Wuhan Sui University (72) Inventor Yuzo Yamamoto 1-8-1, Hisamoto, Takatsu-ku, Kawasaki City, Kanagawa Prefecture Asahi Electric Co., Ltd. (72) Inventor's car Koken 1-8-1, Hisamoto, Takatsu-ku, Kawasaki-shi, Kanagawa Asahi Electric Co., Ltd. (56) Reference JP-A-1-287479 (JP, A) Furukaihei 4-79268 (JP, U) Furukaihei 6-53980 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 19/00-19/32 G01R 31/02 G01R 15/18 H02H 3/16

Claims (7)

(57) [Claims] 1. A mass armature that is swingable about a horizontal swing axis, a permanent magnet that attracts and holds the mass armature in a predetermined posture, and the mass armature in the predetermined posture is engaged to prevent falling. Display member, engagement disengagement urging means for urging the mass armature to be released from the predetermined posture with a rotational torque weaker than the attraction and holding by the permanent magnet, and an induction coil in which a voltage is induced by an alternating current. And an degaussing coil which is wound around the magnetic path of the permanent magnet and to which the induced voltage of the induction coil is applied. 2. The alternating current detection indicator according to claim 1, wherein the induction coil is mounted on a leg of a steel tower or a concrete column through which an alternating current to be detected can flow, and a holding member made of a magnetic material penetrating the induction coil. An alternating current detection indicator characterized by being fixed. 3. The alternating current detection display according to claim 1, wherein the induction coil is a CT sensor. 4. The alternating current detection display according to claim 1, wherein the mass armature has a V-shape with a large opening angle with the opening facing upward, and the swing shaft is arranged at a bending point thereof. , An alternating current detection display characterized in that one of the V-shaped free ends is engaged with the display member and the other free end is elastically biased by a spring in a direction of releasing the engagement. . 5. The alternating current detection indicator according to claim 1, wherein the mass armature, the permanent magnet, the display member in a state where dropping is prevented, the disengagement biasing means, and the degaussing coil are housed in a housing. An alternating current detection display characterized in that, when disengaged, the display member is configured to fall outside the housing by a predetermined amount to be in a suspended state. 6. The alternating current detection indicator according to claim 5, wherein a pair of test terminals are provided on an outer surface of the housing, and the pair of test terminals are electrically connected to both ends of the degaussing coil. An alternating current detection display characterized in that 7. The alternating current detection display according to claim 5, wherein the mass armature can be rotated from the state in which the predetermined posture attracted and held by the permanent magnet is released to the state in the predetermined posture. An alternating current detection display characterized in that a bar is provided, and one end of the operation bar is projected from the housing so that the mass armature can be rotated from the outside of the housing.