JP7816941B2 - How to prevent accidental disconnection of live wires - Google Patents

Description

The present invention relates to a live wire accidental disconnection prevention method and live wire accidental disconnection prevention sensor that warns users, such as workers, against accidentally disconnecting live wires (i.e., electric wires with voltage applied), in order to prevent such users.

For example, when repairing or inspecting electrical equipment, it may be necessary to cut electrical wires.

When a worker or other user cuts an electric wire, they should first confirm that no voltage is being applied to the wire, i.e., that it is not live, before proceeding with the cutting work.

To confirm that the electric wire in question is not live, a voltage detector is generally used, which contacts the detector to confirm that no voltage is being applied to the wire in question (i.e., there is a power outage and the wire is not live).

Various types of voltage detectors are known for use in such electrical work, including types used as stand-alone detectors and types attached to tools such as pliers, as described in the following patent documents:

Japanese Patent Application Laid-Open No. 2002-148287 Japanese Patent Application Publication No. 11-33920 Patent No. 6467447

However, when using a detector alone, as in Patent Document 1, workers and other users must carry around many other devices and tools in addition to the detector when performing electrical work, making transportation cumbersome. Furthermore, the work process becomes cumbersome because the voltage detection and cutting of the electric wires must be performed separately. Furthermore, voltage detection must be performed before cutting, but there is a risk that the voltage detection will be forgotten.

Furthermore, in the case of tools that are attached to them, as in Patent Documents 2 and 3, it is often physically and economically difficult to attach a voltage detector to every cutting tool. This means that, depending on the cutting tool being used, workers and other users will need to attach the voltage detector to that cutting tool when cutting, which makes the process cumbersome. There is also a risk that the user may forget to attach the voltage detector in the first place.

To address the above-mentioned problems, the present invention aims to provide a live wire accidental disconnection prevention method and live wire accidental disconnection prevention sensor that can prevent accidentally disconnecting a live wire when cutting an electric wire.

In order to achieve the above object, the invention according to claim 1 comprises:
A method for preventing accidental disconnection of a live wire, comprising: measuring a voltage induced in a human body by holding a live wire with a hand using a first electrode of a detection circuit; and measuring a voltage relative to the ground using a second electrode of the detection circuit;
The current flowing due to the difference between the potential of the first electrode and the potential of the second electrode is detected by the detection circuit,
When a human body insulated from the ground holds the live wire with its hand , a signal is output from the detection circuit, thereby providing a method for preventing erroneous disconnection of the live wire.

The invention according to claim 2 is as follows:
The method for preventing accidental disconnection of a live wire as described in claim 1 is such that the first electrode is made of a plate having a certain area with a dielectric between it and the human body, and the second electrode has a shape that reduces the vertical projection area relative to the first electrode and increases the area relative to the ground.

The invention according to claim 3 is as follows:
The method for preventing accidental cutting of a live wire as described in claim 2 is such that the dielectric interposed between the human body is an insulating container that houses the first electrode and the second electrode, or a combination of the insulating container and any of work clothes, a helmet, shoes, or a belt.

The invention according to claim 4 is as follows:
The method for preventing erroneous disconnection of a live wire according to any one of claims 1 to 3 , wherein the first electrode is a flat plate, and the second electrode is a pole-shaped electrode standing on the flat plate of the first electrode.

The invention according to claim 5 is as follows:
The method for preventing erroneous disconnection of a live wire according to any one of claims 1 to 3 , wherein the first electrode is a flat plate, and the second electrode is a cylindrical electrode standing on the flat plate of the first electrode.

The invention according to claim 6 is as follows:
The method for preventing erroneous disconnection of a live wire according to any one of claims 3 to 5 is characterized in that the first electrode, the second electrode and the detection circuit are housed in an insulating container.

According to the inventions of claims 1 to 6 , by attaching the device somewhere on the body of a user such as a worker, a signal is output when the user such as a worker tries to cut a live wire with a cutting tool. Therefore, when a user such as a worker tries to cut a live wire by mistake during electrical work, etc., it is possible to call the user's attention and prevent the user from accidentally cutting the live wire, which is convenient.

Furthermore, according to the fourth and fifth aspects of the present invention, the voltage generated between the first electrode and the second electrode is increased, and the voltage induced in the human body can be detected reliably, which is convenient.

Furthermore, according to the invention of claim 6 , the first electrode, the second electrode, and the detection circuit are housed in the insulating container, which can be easily attached to a user such as an operator, which is convenient.

1 is a diagram illustrating the principle of current flowing through a human body when the human body approaches a live line and current being generated from the human body. 1 is a schematic diagram illustrating the principle of a main circuit related to a voltage induced in a human body according to a first embodiment of the present invention; 1A is a schematic diagram showing the principle of a detection circuit of a sensor for preventing erroneous disconnection of a live wire according to a first embodiment of the present invention, and FIG. 1B is an equivalent circuit diagram of the same. 1 is a perspective view showing the appearance of a live wire erroneous disconnection prevention sensor according to a first embodiment of the present invention; 1 is a schematic vertical cross-sectional view showing the structure of a live wire erroneous disconnection prevention sensor according to a first embodiment of the present invention; 10 is a schematic vertical cross-sectional view showing another example of the live wire erroneous disconnection prevention sensor according to the first embodiment of the present invention; FIG. 10 is a schematic vertical cross-sectional view showing another example of an electrode of the live wire erroneous disconnection prevention sensor according to the first embodiment of the present invention. FIG. 10 is a schematic vertical cross-sectional view showing another example of the live wire erroneous disconnection prevention sensor according to the first embodiment of the present invention; FIG. 10 is a schematic vertical cross-sectional view showing another example of an electrode of the live wire erroneous disconnection prevention sensor according to the first embodiment of the present invention. FIG. 1A and 1B are side views showing a state in which a live wire erroneous disconnection prevention sensor according to a first embodiment of the present invention is attached to a helmet of a user such as a worker, in which FIG. 1A shows a clip-fastened state and FIG. 1B shows a band-fastened state. 1A and 1B are side views showing a state in which a live wire accidental disconnection prevention sensor according to a first embodiment of the present invention is attached to work shoes, in which (a) the live wire accidental disconnection prevention sensor is fastened to the heel with a clip, and (b) the live wire accidental disconnection prevention sensor is fastened to the toe with a band. 1 is a configuration diagram of a detection circuit of a live wire erroneous disconnection prevention sensor according to a first embodiment of the present invention; 1 is an explanatory diagram showing a state in which a user such as a worker is wearing a live wire erroneous disconnection prevention sensor according to the first embodiment of the present invention on his/her wrist while performing work to cut an electric wire. 1 is an explanatory diagram showing a state in which a user such as a worker is wearing a live wire erroneous disconnection prevention sensor according to the first embodiment of the present invention on his/her wrist while performing work to cut an electric wire.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the components described in these embodiments are merely examples and are not intended to limit the scope of the present invention to these components alone.

<First Embodiment>
First, before explaining the live wire erroneous disconnection prevention method and live wire erroneous disconnection prevention sensor according to the first embodiment of the present invention with reference to the drawings, the potential of each part of the human body was measured. Note that in the main circuit of the live wire erroneous disconnection prevention sensor according to the first embodiment, when indicating voltage or capacitance, "0" is inserted into V or C, but in the detection circuit, "0" is not inserted into V or C.

First, we investigated the potential distribution on the human body. To do this, we used an AC potential wireless meter (not shown) to measure the potential at both wrists, both ankles, and the head of a human body H approaching a live AC power line W, as shown in Figure 1.

The measurement results showed that, naturally, a potential would be generated in the hand extended toward the AC power line W, but it was also confirmed that a potential was generated in the opposite hand. Furthermore, there were many body positions in which the potential was greater on the feet than on the hand extended toward the AC power line W. This showed that a potential was generated throughout the entire human body H (i.e., a voltage was being induced). Furthermore, it was found that the human body H was floating above the ground G, at a different potential from the ground G, and that this potential was different in each part of the human body H.

However, considering that the human body H is a conductor of several kΩ and is isolated from the AC power lines W and the ground G by an impedance of several MΩ or more, it is unlikely that a potential difference of several tens of volts or more would occur within the human body H, enough to operate a wireless AC potential measuring device.

As a result of this investigation, it was found that the AC potential wireless measuring device does not detect the electrode potential from the ground G, but rather the current level (≒ current magnitude) passing through the electrode. Furthermore, the potential of the human body H is floating above the ground G, and is at a different potential from the ground G. However, it was found that the entire human body H is actually at the same potential, and the current values flowing through various parts of the human body H vary in magnitude depending on the surrounding impedance, and that the measurement values of the AC potential wireless measuring device change depending on this current value.

As shown in Figure 1, when a human body H approaches a live 100V AC power line W, currents i1, i2, and i3 flow into the human body H from the AC power line W through the arms, torso, and head. These currents cause the human body H to have an AC voltage from the ground G. In the example shown in Figure 1, the AC voltage generated at the potential of the human body H is 30V. Then, due to the potential of the human body H, currents i4, i5, i6, and i7 flow through the capacitance between the human body H and the ground G and through the arms, legs, and head on the opposite side of the AC power line W.

This current ratio varies greatly depending on the relationship between the AC power line W, the human body H, and the ground G, but when one hand is brought close to the AC power line W and there is a wall on the other side of the AC power line W, the current values are as shown in Figure 1. That is, i1 = 0.1 μA, i2 = 0.2 μA, i3 = 0.1 μA, i4 = 0.02 μA, i5 = 0.18 μA, i6 = 0.18 μA, i7 = 0.02 μA. As a result, it was found that measurements can be made even when the meter is held on the arm opposite the AC power line W, and that measurements can be made with better sensitivity on the leg than on the arm.

Conventional general-purpose measuring instruments and voltage detectors are designed to detect currents i1 and i2 from an AC power line at levels of around 0.1 to 0.2 μA when approaching the line, and are therefore unable to detect low-level currents such as i4 and i7, which are around 0.02 μA, flowing from the human body. Furthermore, because they are designed on the assumption that "human body potential = earth potential," they are unable to utilize the relatively large current levels of i5 and i6, which are around 0.18 μA. Note that Figure 1 shows the current distribution at a representative part of the human body H. In reality, current inputs and outputs occur at a much more diverse range of parts of the human body H.

Furthermore, if the insulation of the human body H is poor and the human body H is at the same potential as the ground G, only the inflow currents i1, i2, and i3 can be used, and the potential of the human body H cannot be detected. When measurements were actually taken with a barefoot person and the human body H at the same potential as the ground G, the measuring device on the other side of the AC power line W did not react.

In this way, when human body H approaches a live AC power line W, current flows from the voltage source into human body H through the arms, torso, and head. This current causes human body H to have an AC potential relative to the ground G, and the potential of human body H causes current to flow through the arms, legs, and head on the opposite side of the voltage source via the capacitance between human body H and the ground G.

This invention was made based on this principle. As shown in Figure 2, the combined capacitance C0 (series connection of C01 and _{C02 )} of the closed circuit (hereinafter referred to as the main circuit) flowing from the live AC power line W through the human body H to the ground G is expressed by the following equations 1 and 2. Note that _V0 is the potential of the AC power line W with respect to the ground G, _V01 is the potential due to the capacitance _C01 between the AC power line _W and the human body H, and _V02 is the potential due to the capacitance _C02 of the human body H with respect to the ground G.

Therefore, equations 3 and 4 are obtained, and it is found that the human body H has a potential (V ₀₂ ) relative to the ground G.

Furthermore, because of equations 5 and 6, the closer the human body H is to the live line (because d of _C01 becomes smaller and _C01 becomes larger), the larger _V02 becomes. As a result, if _V02 can be detected, it can be detected whether or not the AC power line W that the human (human body H) is trying to cut is live. Furthermore, because of equations 5 and 6, the closer the human body H is to the live part (because d of _C01 becomes smaller and _C01 becomes larger), the larger _V02 becomes. As a result, if _V02 can be detected, it can be detected that the human (human body H) is approaching the live part.

3(a) is a schematic diagram showing the detection principle of part A in FIG. 2, i.e., the live line accidental disconnection prevention sensor A according to the first embodiment. This live line accidental disconnection prevention sensor A is a wristwatch-type sensor worn around the wrist of a human body H, and is mainly composed of a first electrode 1 that measures the voltage induced in the human body when the human body approaches a live AC power line W, and a second electrode 2 that measures the voltage relative to the ground G. Here, _C1 is the capacitance between the human body H and the first electrode 1, _C21 is the capacitance between the first electrode 1 and the second electrode 2, _C22 is the capacitance between the human body H and the second electrode 2, _C31 is the capacitance between the first electrode 1 and the ground G, and _C32 is the capacitance between the second electrode 2 and the ground G.

In addition, a detection circuit 4 is provided between the first electrode 1 and the second electrode 2.

The structure of the wristwatch-type live wire accidental disconnection prevention sensor A will be described in detail. As shown in Figure 4, the live wire accidental disconnection prevention sensor A is configured in a wristwatch style, with a round, box-shaped insulating case (≒container) 15 mounted approximately in the center of a band-shaped body 5. As shown in Figure 5, a circular first electrode 1 is housed inside the insulating case 15, and a rod-shaped second electrode 2 is mounted vertically in the center of one surface of the first electrode 1. Furthermore, a detection circuit 4 is mounted between the first electrode 1 and the second electrode 2. As shown in Figure 4, a buckle 5a at one end of the band-shaped body 5 and multiple through-holes 5b at the other end allow the sensor to be worn on the wrist of a user such as a worker. The insulating case 15 acts as a dielectric between the sensor and the human body of the user such as a worker.

The overall combined capacitance of this live line erroneous disconnection prevention sensor A is expected to be the following equation (7): Also, the voltage V _C2 generated between the first electrode 1 and the second electrode 2 is given by equation (8). This V _C2 is the voltage that enables detection.

From the above equation 8, if _C1 is increased and _C21 is decreased, V _C2 increases, and it is possible to obtain a V _C2 that is effective for detection. Furthermore, if _C32 is large, an even more effective V _C2 can be obtained. Furthermore, if _C22 is small, it is possible to increase the current flowing through the detection circuit 4, which is advantageous for detection.

Therefore, "S" in C = εS/d is increased and "d" is decreased to increase _C1 . For this reason, the first electrode 1 has a large area and the electrode shape that contacts the second electrode 2 is made thin to decrease "S" in C = εS/d and decrease _C21 . For this reason, in the live wire accidental disconnection prevention sensor A according to the first embodiment, the first electrode 1 is disc-shaped and has a large area, as shown in FIG.

On the other hand, the second electrode 2 needs to have a smaller vertical projection area relative to the first electrode 1 to reduce the "S" and thus reduce _C21 . It also needs to have a smaller vertical area relative to the human body to reduce the "S" and thus reduce _C22 . Furthermore, it is necessary to ensure an area (lateral area) relative to the space (ground), thereby increasing _C32 . Therefore, the second electrode 2 shown in FIG. 5 has a pole (cylinder) shape or a hollow cylindrical shape, and is configured to stand upright from approximately the center of the first electrode 1.

These configurations increase the voltage V _C2 generated between the first electrode 1 and the second electrode 2 , making it possible for the detection circuit 4 to detect it.

Note that the configuration of the live line accidental disconnection prevention sensor A is not limited to that shown in Figures 4 and 5. For example, as shown in Figures 6 and 7, a live line accidental disconnection prevention sensor B may be configured in which a first electrode 1 is housed inside a box-shaped insulating case 16, a pole-shaped second electrode 2 is provided vertically in the center of one surface of the first electrode 1, and a detection circuit 4 is provided between the first electrode 1 and second electrode 2. Note that a clip 16a is provided on the side of the insulating case 16.

Alternatively, as shown in Figures 8 and 9, a live wire accidental disconnection prevention sensor C may be configured in which a first electrode 1 is housed inside a box-shaped insulating case 16, a cylindrical second electrode 17 is provided vertically in the center of one surface of the first electrode 1, and a detection circuit 4 is provided between the first electrode 1 and second electrode 17. A clip 16a is provided on the side of the insulating case 16.

These live wire accidental disconnection prevention sensors B and C have an insulating case 16 attached to the rear of a work helmet 18 with a clip 16a, as shown in Figure 10(a). The clip 16a in Figure 10(a) is slightly different from the clips in Figures 6 and 8, but has the same gripping function. As shown in Figure 10(b), the insulating case 16 may also be attached to the work helmet 18 with a band 19. As shown in Figure 11(a), the insulating case 16 may also be attached to the heel of a work shoe 20 with a clip 16a. As shown in Figure 11(b), the insulating case 16 may also be attached to the top of the toe of a work shoe 20 with a band 21. In these cases, either the insulating case 16 and the work helmet 18 or the work shoe 20 act as a dielectric between the insulating case 16 and the user's body, such as a worker.

12, the detection circuit 4 is configured to include an amplifier circuit 6 that amplifies the voltage V _C2 generated by the current signal flowing through _C21 between the first electrode 1 and the second electrode 2, and a reference voltage generation circuit 7, and a comparison circuit 8 that compares the output signal of the amplifier circuit 6 with the output signal of the reference voltage generation circuit 7, and only when a signal is outputted does the sound generation circuit 9 and the lighting display circuit 10 operate. The detection circuit 4 is also provided with a power supply 11, and power is supplied to each circuit by turning on a switch 12 of the power supply 11.

<Operation method of live wire erroneous disconnection prevention sensor A>
When a user, such as a worker, wearing the live wire accidental disconnection prevention sensor A, starts work, he or she turns on the switch 12 of the detection circuit 4. Then, as shown in FIG. 13 , if the user holds an electric wire 22 in his or her left hand while wearing the live wire accidental disconnection prevention sensor A and attempts to cut the electric wire 22 with a manual cutting tool 23, such as pliers, in his or her right hand, if the electric wire 22 is energized, a minute current flows into the user through the left hand. Then, as shown in FIG. 3( b ), this current causes the electric potential of the user's body H to reach _V02 (≒ a voltage is induced). The first electrode 1 is divided from the electric potential _V02 via the electrostatic capacitance _C1 to reach the electric potential _V2 . The second electrode 2 has a potential obtained by dividing the current i flowing out due to the electric potential _V2 by _C21 and _C32 . The detection circuit 4 detects the potential difference V _C2 across the capacitance _C21 caused by this outflow current i, and if the output signal related to V _C2 amplified by the amplifier circuit 6 is greater than the reference voltage, the sound generation circuit 9 emits a warning sound and the indicator circuit 10 lights up. This alerts the user and informs them that the electric wire 22 is live and that they have made a mistake in cutting the wire. Note that even if a user such as an operator holds the electric wire 22, which is not applied with voltage, in their hand and tries to cut it while the switch 12 is on, the sound generation circuit 9 and indicator circuit 10 will not operate.

Note that the above explanation was based on the case where an electric wire 22 is to be cut using a manual cutting tool 23 such as pliers, but it goes without saying that the live wire accidental cut prevention sensor A will operate in the same way even if an electric cutting tool 24 such as an electric cutter is used, as shown in Figure 14.

Furthermore, in the above-described first embodiment, the live line accidental disconnection prevention sensor A is provided with the sound generating circuit 9 and the lighting display circuit 10, but either the sound generating circuit 9 or the lighting display circuit 10 may be provided in the live line accidental disconnection prevention sensor A. Alternatively, without providing these circuits, the output signal from the comparison circuit 8 may be received by a transmitter (not shown) and output to the outside as a wireless signal or the like, which may be received by a communication device or terminal device provided separately from the live line accidental disconnection prevention sensor A and a warning may be issued or displayed by that device. In other words, it is sufficient that the detection circuit 4 outputs a signal when the voltage V _C2 generated by the current signal flowing through _C21 between the first electrode 1 and the second electrode 2 exceeds a predetermined value or is equal to or greater than a predetermined value.

Furthermore, in the above-mentioned first embodiment, an example of using a wristwatch-type live wire accidental disconnection prevention sensor A wrapped around the wrist of a human body H was shown, but this configuration is not limited to this. For example, it may be worn around the wrist over work clothes, or it may be worn around the belt of a user such as a worker. In these cases, the work clothes or belt also serve as a dielectric.

A Live wire accidental disconnection prevention sensor B Live wire accidental disconnection prevention sensor C Live wire accidental disconnection prevention sensor G Earth H Human body W AC power line
1 First electrode 2 Second electrode 4 Detection circuit 5 Strip
5a Buckle 5b Through hole
6 Amplification circuit 7 Reference voltage generation circuit
8 Comparison circuit 9 Sound generation circuit
10 Lighting display circuit 11 Power supply
12 Switch 15 Insulation case
16 Insulation case 16a Clip
17 Second electrode 18 Work helmet
19 Band 20 Work shoes
21 Band 22 Electric wire
23 Manual cutting tools 24 Electric cutting tools

Claims (6)

A method for preventing accidental disconnection of a live wire, comprising: measuring a voltage induced in a human body by holding a live wire with a hand using a first electrode of a detection circuit; and measuring a voltage relative to the ground using a second electrode of the detection circuit;
The current flowing due to the difference between the potential of the first electrode and the potential of the second electrode is detected by the detection circuit,
A method for preventing accidental disconnection of a live wire, characterized in that a signal is output from said detection circuit when a human body insulated from the ground holds said live wire with a hand . 2. The method for preventing accidental disconnection of a live wire as described in claim 1, characterized in that the first electrode is made of a plate having a certain area with a dielectric between it and the human body, and the second electrode has a shape that reduces the vertical projection area relative to the first electrode and increases the area relative to the ground. 3. The method for preventing accidental disconnection of a live wire according to claim 2, wherein the dielectric interposed between the human body and the first electrode and the second electrode is an insulating container that houses the first electrode and the second electrode, or a combination of the insulating container and any of work clothes, a helmet, shoes, and a belt. 4. The method for preventing accidental disconnection of a live wire according to claim 1 , wherein the first electrode is a flat plate, and the second electrode is a pole-shaped electrode standing on the flat plate of the first electrode . 4. The method for preventing accidental disconnection of a live wire according to claim 1 , wherein the first electrode is a flat plate, and the second electrode is a cylindrical electrode standing on the flat plate of the first electrode . 6. The method for preventing erroneous disconnection of a live wire according to claim 3 , wherein the first electrode, the second electrode, and the detection circuit are housed in an insulating container.