A water-immersion electric shock prevention circuit and method

Abstract

The present invention relates to the field of leakage prevention circuits, and in particular to a water-immersion anti-electric shock circuit, comprising an AC power supply, a load circuit, an equivalent circuit of a human body grounding point relative to an indoor near-ground point forming a loop, a voltage divider circuit, a first switch, and a second switch. The two ends of the load circuit are respectively connected to the live wire and the neutral wire of the AC power supply, one end of the second switch is connected to the live wire, and the other end thereof is respectively connected to the equivalent circuit, one end of the first switch, and one end of the voltage divider circuit. The two ends of the equivalent circuit are respectively grounded, and the other end of the first switch is respectively connected to the other end of the voltage divider circuit, the neutral wire, and the ground wire. A method for preventing electric shock is also provided based on the circuit. The most concise, reliable, effective, and low-cost method is used to achieve that when a bare terminal with strong electricity is immersed in water, power can still be supplied to the load, and the human body is not in danger of being electrocuted when using electricity when it is in direct contact with water.

Description

Technical Field

[0001] The present invention relates to the field of leakage prevention circuits, and in particular to a water immersion electric shock prevention circuit and method. Background Art

[0002] The conventional power supply lines on the market for home installation and use are all in the form of a main air switch or leakage protection switch + electric meter + multi-way leakage switch (sub-switch) + wiring strip. Although the lines are simple, most wiring strips do not have the function of immersion in water. Even after being immersed in water, leakage may occur, causing dangerous situations such as electric shock to people. People often suffer sudden electric shock accidents when using electricity, and even serious accidents may lead to death. According to statistics from authoritative departments, an average of 3 to 5 people die from electric shock accidents caused by leakage every day.

[0003] The existing water immersion protection against electric shock methods or devices on the market are relatively clumsy and complex in structure, with many components, high overall cost and extremely high failure rate.

[0004] Some people have developed technologies and products that can prevent electric shock when terminal strips and sockets are immersed in water, but most of them basically use input and output series connection terminals and anti-leakage conductors to surround some terminals. The leakage conductors are used to absorb the leakage current of the terminals to achieve the effect of preventing electric shock.

[0005] Existing methods or devices for preventing electric shock by water immersion almost all adopt a series circuit structure, adding a conversion switch in the middle of the input and output of the main power supply cable, which greatly reduces the actual application effect. Therefore, the maximum power of the load is also limited by the switch components. Due to the limitations of the switch component process and cost, it is actually difficult to truly achieve large-scale commercial and civilian production. If used improperly, such as short-circuiting the output load end, it is easy to directly burn the switch components or even cause a serious accident.

[0006] The traditional method uses leakage-proof conductors to absorb current, and also limits the conductor's relevant size, cross-sectional area, installation location, distance, etc. Products designed and planned under such harsh conditions are difficult to control cost and quality, have extremely poor controllability, and greatly reduced consistency.

[0007] There is no simple low-cost water-immersion circuit for preventing leakage or electric shock on the market yet. Summary of the invention

[0008] The present invention provides a water-immersion electric shock protection circuit and method, aiming to solve the harm to the human body caused by leakage of metal terminals carrying strong electricity or mains electricity due to equipment failure, human operation error or other unknown physical contact.

[0009] The present invention provides a water immersion electric shock protection circuit, comprising an AC power supply, a load circuit, an equivalent circuit of a human body grounding point relative to an indoor near-ground point forming a loop, a voltage divider circuit, a first switch, and a second switch. The two ends of the load circuit are respectively connected to a live wire and a neutral wire of the AC power supply, one end of the second switch is connected to the live wire, and the other end is respectively connected to the equivalent circuit, one end of the first switch, and one end of the voltage divider circuit, the two ends of the equivalent circuit are respectively grounded, and the other end of the first switch is respectively connected to the other end of the voltage divider circuit, the neutral wire, and the ground wire.

[0010] As a further improvement of the present invention, the equivalent circuit includes a first capacitor and a first resistor, the first capacitor is connected in parallel with the first resistor, one end of the first capacitor is respectively connected to the second switch and the indoor ground, and the other end of the first capacitor is connected to the human body grounding point.

[0011] As a further improvement of the present invention, the voltage divider circuit includes a second capacitor and a second resistor, one end of the first switch is respectively connected to one end of the second resistor and one end of the second capacitor, and the other end of the first switch is respectively connected to the other end of the second resistor and the other end of the second capacitor.

[0012] As a further improvement of the present invention, the first switch and the second switch are relays or thyristors.

[0013] As a further improvement of the present invention, the first switch and the second switch are interlocking switches.

[0014] The present invention also provides a method for preventing electric shock by immersion in water, comprising the following steps:

[0015] S1. During the positive half cycle of the sine wave generated by the alternating current, the first switch is controlled to be closed, the second switch is controlled to be opened, the two ends of the voltage divider circuit are short-circuited, the human body resistance is connected in series with the equivalent circuit, and the AC power supply charges the human body resistance and the equivalent circuit;

[0016] S2. In the negative half cycle of the sine wave generated by the alternating current, the first switch is controlled to be opened and the second switch is closed. The two ends of the voltage divider circuit are connected to the live wire and the neutral wire respectively. The AC voltage charges the voltage divider circuit. One end of the equivalent circuit is grounded and the other end is connected in series with the human body resistance. The equivalent circuit charges the human body resistance.

[0017] As a further improvement of the present invention, the step S1 includes: the voltage divider circuit includes a second resistor and a second capacitor, and in the positive half cycle of the alternating current, the resistor and capacitor formed by the second resistor and the second capacitor discharge themselves.

[0018] As a further improvement of the present invention, step S2 includes: the equivalent circuit includes a first resistor and a first capacitor, and in the negative half cycle of the alternating current, the first capacitor discharges through the first resistor and the human body resistance.

[0019] The beneficial effects of the present invention are: using the most concise, reliable, effective and low-cost method to achieve that when the exposed terminals with strong electricity are immersed in water, power can still be supplied to the load, and there is no danger of electric shock when the human body is in direct contact with water. Even if the terminal block with AC power is directly thrown into the water, the human body can still touch the water and no longer cause serious electric shock injuries to the human body. The product of this invention is matched with a leakage protector, or a reclosing leakage protector or a multi-function all-in-one developed using the technology of the present invention. Even if the wall switch socket is energized and soaked in rainwater, it can ensure the safety of electricity use suitable for most households and military industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the water immersion electric shock protection circuit in the present invention;

[0021] Figure 2 This is the principle diagram of AC power generation;

[0022] Figure 3 It is the power supply diagram of a single-phase transformer;

[0023] Figure 4 It is the sinusoidal AC waveform of alternating current;

[0024] Figure 5 It is the waveform diagram of the positive half cycle of the original sinusoidal voltage;

[0025] Figure 6 It is the equivalent circuit diagram corresponding to the positive half cycle of the original sinusoidal voltage;

[0026] Figure 7 It is the waveform of the negative half cycle of the original sinusoidal voltage;

[0027] Figure 8 It is the equivalent circuit diagram corresponding to the negative half cycle of the original sinusoidal voltage;

[0028] Fig. 9 This is the current trend diagram of the first half-wave cycle (positive half cycle) after power-on;

[0029] Fig.10 This is the current trend diagram of the second half-wave cycle (negative half cycle) after power-on;

[0030] Fig.11 This is a schematic diagram showing that in 220V 50HZ power, the safety voltage of 36V is exceeded for 8mS in each half cycle;

[0031] Fig.12 This is the current trend diagram of the third half-wave cycle (positive half cycle) after power-on;

[0032] Fig.13 It is an equivalent principle diagram of the present invention in the positive half cycle;

[0033] Fig.14 It is a schematic diagram of the current trend and voltage distribution in the positive half cycle of the present invention;

[0034] Fig.15 It is an equivalent principle diagram of the present invention in the negative half cycle;

[0035] Fig.16 It is a schematic diagram of the current trend and voltage distribution of the present invention in the negative half cycle. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0037] The circuit schematic diagram of the present invention is shown in Figure 1 The entire power supply consists of four parts: the transformer remote line 1, the local terminal block 2, the newly added local anti-electric shock circuit 3, and the load end 4.

[0038] like Figure 2 As shown, the AC power we commonly use, whether single-phase or three-phase, generates electricity by driving the coil to cut the magnetic lines of force, and then goes through a series of voltage conversion or matching to output and provide stable electricity to the load.

[0039] With the power drive (rotor rotating around the spindle), a stable sine wave cycle is generated, which is divided into positive half-cycle and negative half-cycle, and the amplitude represents the voltage output on the time axis. Take my country's 220V AC as an example, it is a 50Hz sine wave, and the corresponding period is T=20mS (50 changes in 1 second). As shown in the figure above, the phase angle of 0-π (or -10mS in T / 2 time) corresponds to the positive half-cycle voltage output, and π-2π corresponds to the negative half-cycle voltage output. Therefore, the electric energy transmitted on the wire is positive voltage and negative voltage on the time axis relative to the ground wire.

[0040] like Figure 3 As shown, single-phase AC is on one side of the transformer, the neutral line - N and the ground line - G are the common grounding points, which we call the remote ground or the ground of the transformer. The potential relative to the earth is 0V, and the live line (phase line) periodically outputs a sinusoidal voltage as the rotor rotates. The AC mains we commonly use is 220V AC 50Hz sinusoidal AC in my country, and 110V 50Hz or 60Hz sinusoidal AC in some countries. In short, most countries use sinusoidal AC waves, and the voltage fluctuations are expressed on the time axis as follows: Figure 4 shown.

[0041] For the sake of intuition, we can assume that the load mounted on the user end is a pure resistive load - a pure resistor. Based on this, we can draw the equivalent circuit diagrams of the entire power supply system corresponding to the positive half cycle and the negative half cycle respectively: Figure 8 .

[0042] like Figures 5 to 8 In this circuit structure, the neutral wire N and the ground wire G1 are connected at the far end of the transformer, and are connected to the ground of the earth, which is what we call the ground wire, and is relatively safe. The normal electrical load is connected between the live wire L and the neutral wire N, that is, the load resistor R1.

[0043] The location where electric shock occurs is where the human body is. When the human body touches the live wire, the human body is equivalent to a resistor. Although there is no direct line between the ground where the human body is and the near ground point in the room, because of the ground, when there is high voltage contact, a circuit network composed of resistors and capacitors will be formed. It's just that we can't see or touch this resistor and capacitor. The current then returns to the ground of the transformer through the ground wire loop, forming a complete loop system, which can cause electric shock.

[0044] The circuit formed by the human body grounding point G3 relative to the indoor near-ground point G2 contains a resistor and capacitor structure. The resistance value of the first resistor R2 depends on the insulation degree of the ground, such as humidity, contact area, conductivity of the ground, distance and many other factors. This resistance value is generally relatively large but must exist, and the resistance value is not fixed. At the same time, there is also an equivalent capacitor in parallel with it, namely the first capacitor C1. The earth is also equivalent to a polarity of the capacitor, and an invisible actual capacitor will be formed between the electrode of the human body. Due to such a structure formed by the earth and the human body, the circuit structure of the first resistor R2 and the first capacitor C1 in parallel is a circuit that is not visible and has uncertain resistance and capacitance values ​​relative to sufficiently high voltage alternating current. Since it is a circuit, it can form a current. When this current is large enough or lasts long enough to reach the limit of human perception or tolerance, then an electric shock accident will inevitably occur. It is worth noting that since there are resistance and capacitance, and the capacitor has the function of energy storage, a certain voltage (electromotive force) will also be generated at both ends of the capacitor. The principle of electric shock can be deduced from the first three half-wave cycles:

[0045] like Fig. 9As shown, when the power is just turned on, there is no voltage across the first capacitor C1 and the first resistor R2, so this process is the process of charging the first resistor R2 and the first capacitor C1. The resistance of the first resistor R2 is often large, and the capacitance of the first capacitor C1 is also large, so the first capacitor C1 will be charged quickly, but if the resistance of the first resistor R2 is relatively large, the discharge speed will be relatively slow. Therefore, a sufficiently high voltage may be charged to the first capacitor C1 in the positive half cycle.

[0046] like Fig.10 As shown, since the first capacitor C1 is charged in the first half-wave cycle, a certain voltage value still exists on the first capacitor C1 in the second half-wave cycle. Figure 8 We can see that the negative half cycle has been cut in. At this time, the negative half cycle voltage provided by the line will be applied to both ends of the human body resistance together with the voltage stored on the first capacitor C1, that is, U1. Therefore, after the negative half cycle, both ends of the human body are subjected to a voltage much higher than the voltage originally provided by the line itself, that is, U1>>U, but the maximum will not exceed 2U, that is, 2 times the voltage. Excessive voltage applied to the human body resistance will rapidly reduce the resistance of the human body resistance, forming a larger current. When this current exceeds the safety current of the human body and continues for a continuous period of time, there will be a risk of electric shock. If it cannot be escaped, it will lead to death. This is why we feel the stinging pain of electric shock or paralysis from electric shock that we cannot bear.

[0047] For example, in a 220V AC system, the DC transient peak value can reach times of 220V, that is, the human body cannot withstand it at this moment. We know that the highest voltage that the human body can withstand is a safe voltage of 36V. The half-wave period of a 50HZ sine wave is 10Ms, of which the voltage range exceeding 36V is about 8mS. Therefore, the voltage exceeds the safe voltage of 36V for 0.8 seconds every second. Fig.11 .

[0048] The third half-wave cycle is Fig.12 As shown, the voltage U sent by the line is reversed again, part of the current flows through the load resistor R1, and the other part flows through the first resistor R2 and the first capacitor C1 through the human body resistance, charging the first capacitor C1 in reverse. However, because the voltage U2 remains on the first capacitor C1 in the previous cycle and has not been discharged, the current U1=U2+U flowing through the human body at this moment still far exceeds the original line voltage and is unbearable. The subsequent waveforms are similar.

[0049] To sum up, except for the first half-wave cycle of power-on when the human body is subjected to a lower voltage, in the subsequent sine wave, when the human body touches the live wire L in the circuit, the human body actually withstands a voltage far exceeding the original circuit. In a higher voltage environment, the human body's resistance is broken down and its resistance value becomes lower, aggravating the accident of electric shock injury or even death, so it is unsafe.

[0050] Based on the above principles, the present invention improves the circuit. Through the improved design, when the human body touches the live wire or has leakage contact or is immersed in water, the voltage applied to both ends of the human body resistance is reduced, so that the electric shock accident can be effectively reduced or prevented, and the entire circuit becomes relatively safe.

[0051] Embodiment 1:

[0052] like Figures 13 to 16 As shown, an improved circuit for preventing electric shock during immersion in water of the present invention comprises an AC power supply, a load circuit, an equivalent circuit of a human body grounding point relative to an indoor near ground point forming a loop, a voltage divider circuit, a first switch S1, and a second switch S2. The two ends of the load circuit are respectively connected to the live wire and the neutral wire of the AC power supply, one end of the second switch S2 is connected to the live wire, and the other end thereof is respectively connected to the equivalent circuit, one end of the first switch S1, and one end of the voltage divider circuit, the two ends of the equivalent circuit are respectively grounded, and the other end of the first switch S1 is respectively connected to the other end of the voltage divider circuit, the neutral wire, and the ground wire.

[0053] The equivalent circuit includes a first capacitor C1 and a first resistor R2, wherein the first capacitor C1 is connected in parallel with the first resistor R2, one end of the first capacitor C1 is respectively connected to the second switch S2 and the indoor ground, and the other end of the first capacitor C1 is connected to the human body grounding point. The voltage divider circuit includes a second capacitor C2 and a second resistor R3, one end of the first switch S1 is respectively connected to one end of the second resistor R3 and one end of the second capacitor C2, and the other end of the first switch S1 is respectively connected to the other end of the second resistor R3 and the other end of the second capacitor C2.

[0054] The first switch S1 and the second switch S2 are interlocking switches, which may be switches such as relays or thyristors.

[0055] Embodiment 2:

[0056] like Fig.13As shown, on the basis of the original power line, a first switch S1 and a second switch S2 are added, and the switch can be a relay or a thyristor. In the positive half cycle, we control the first switch S1 to close and the second switch S2 to open through circuit control; in the negative half cycle, we control the first switch S1 to open and the second switch S2 to close through circuit control. In this way, the leakage detection of the original line will not be affected in the positive half cycle, but the leakage detection in the negative half cycle will be affected or sacrificed, but generally speaking, it does not affect the actual leakage detection function of the original line.

[0057] During the positive half cycle, the first switch S1 is closed, the remote earth G1 of the transformer and the indoor near-ground G2 are short-circuited, and the resistance-capacitance formed by the second capacitor C2 and the second resistor R3 discharges itself; the second switch S2 between the indoor near-ground G2 and the live wire (phase wire) L is disconnected, and U charges the first capacitor C1 through the human body resistance.

[0058] The current trend and voltage distribution in the positive half cycle are as follows Fig.14 As shown, U is the human body resistance and the first resistor R2 and the first capacitor C1 are connected in parallel for series charging, U2 is the voltage between the indoor perigee G2 and the human body grounding point G3, and U1 is the voltage across the human body resistance. Then U=U1+U2, and the voltage across the human body is U1=U-U2, which is less than U. At this time, Fig. 9 There is no difference in the voltage carried by the human body at both ends in the positive half cycle. All subsequent positive half cycles are exactly the same as the first positive half cycle when powered on before the improvement, which are all U1=U-U2. The voltage carried by the human body at both ends in the subsequent positive half cycles before the improvement is as follows Fig.12 As shown, U1=U2+U, which is also a very different improvement point.

[0059] Embodiment three:

[0060] like Fig.15 As shown, during the negative half cycle, the first switch S1 is disconnected, that is, the remote earth G1 of the transformer and the indoor near-point G2 are disconnected, but there is still an earth resistance, that is, the second resistor R3 and the earth capacitance, that is, the second capacitor C2 are connected in parallel and then in series between the remote earth G1 and the indoor near-point G2; the second switch S2 between the indoor near-point G2 and the live wire (phase line) L is closed; the human body grounding point G3 is connected in series through the parallel first resistor R2 and the first capacitor C1.

[0061] The current trend and voltage distribution in the negative half cycle are as follows Fig.16 As shown, U is charged by the second resistor R3 and the second capacitor C2, and at this time U=U3; since L is short-circuited with the human body grounding point G3, the first capacitor C1 is discharged through the first resistor R2 and the human body resistance. At this time, the voltage carried across the human body is U1=U2, which is also less than U.

[0062] Subsequent cycles repeat the above positive and negative half-cycle regular cycle. From this we can see that after the improvement, whether it is the positive half-cycle or the negative half-cycle, the actual voltage carried by both ends of the human body resistance is much smaller than before the improvement. This achieves the goal of reducing the damage caused by electric shock or not, thereby preventing accidents caused by electric shock.

[0063] Through the principle analysis of the invention and the test results of the actual application effect, it is finally found that the main reason why the existing line structure layout causes relatively serious electric shock accidents is that the fixed position of the human body grounding point causes the human body to bear a voltage far exceeding the power supply, which leads to electric shock. This is also determined by this fixed power supply structure. However, we can change the relative position of the human body's grounding point in the power line loop, reduce the leakage voltage loaded on both ends of the human body resistance, and change the power supply structure of the original line as much as possible, so as to reduce the current flowing through the human body per unit time, so as to achieve the purpose of reducing electric shock or not being able to perceive electric shock.

[0064] Through actual improvement and application testing, we have improved the power supply wiring board device, and when it is exposed and energized, it can be immersed in water and can still supply power to various loads normally. At this time, as long as the human body does not touch the live wire (phase wire) and the neutral wire at the same time, when people reach out to touch the water or a single wire, most people can no longer feel the electric shock. It proves that our invention is indeed feasible and effective. For example, we can design this device into various socket switches, and there will be no leakage electric shock accidents caused by immersion in water.

[0065] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A circuit for preventing electric shock when immersed in water, characterized in that: It includes an AC power supply, a load circuit, an equivalent circuit of a human body grounding point relative to an indoor near-ground point forming a loop, a voltage divider circuit, a first switch, and a second switch, wherein the two ends of the load circuit are respectively connected to the live wire and the neutral wire of the AC power supply, one end of the second switch is connected to the live wire, and the other end thereof is respectively connected to the equivalent circuit, one end of the first switch, and one end of the voltage divider circuit, the two ends of the equivalent circuit are respectively grounded, and the other end of the first switch is respectively connected to the other end of the voltage divider circuit, the neutral wire, and the ground wire; The method of preventing electric shock during immersion in water includes the following steps: S1. In the positive half cycle of the sine wave generated by the alternating current, the first switch is controlled to be closed, the second switch is opened, the two ends of the voltage divider circuit are short-circuited, the human body resistance is connected in series with the equivalent circuit, and the AC power supply charges the human body resistance and the equivalent circuit; S2. In the negative half cycle of the sine wave generated by the alternating current, the first switch is controlled to be opened and the second switch is closed. The two ends of the voltage divider circuit are connected to the live wire and the neutral wire respectively. The AC voltage charges the voltage divider circuit. One end of the equivalent circuit is grounded and the other end is connected in series with the human body resistance. The equivalent circuit charges the human body resistance.

2. The water-immersion protection circuit according to claim 1, characterized in that: The equivalent circuit includes a first capacitor and a first resistor, the first capacitor is connected in parallel with the first resistor, one end of the first capacitor is respectively connected to the second switch and the indoor ground, and the other end of the first capacitor is connected to the human body grounding point.

3. The water-immersion protection circuit according to claim 1, characterized in that: The voltage divider circuit includes a second capacitor and a second resistor. One end of the first switch is respectively connected to one end of the second resistor and one end of the second capacitor. The other end of the first switch is respectively connected to the other end of the second resistor and the other end of the second capacitor.

4. The water-immersion protection circuit according to claim 1, characterized in that: The first switch and the second switch are relays or thyristors.

5. The water-immersion protection circuit according to claim 1, characterized in that: The first switch and the second switch are interlocking switches.

6. The water-immersion protection circuit according to claim 1, characterized in that: The step S1 includes: the voltage divider circuit includes a second resistor and a second capacitor, and during the positive half cycle of the alternating current, the resistor and capacitor formed by the second resistor and the second capacitor discharge themselves.

7. The water-immersion protection circuit according to claim 1, characterized in that: The step S2 includes: the equivalent circuit includes a first resistor and a first capacitor, and in the negative half cycle of the alternating current, the first capacitor discharges through the first resistor and the human body resistor.

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