WO2021174747A1

WO2021174747A1 - Immersion electric shock prevention circuit and method

Info

Publication number: WO2021174747A1
Application number: PCT/CN2020/103157
Authority: WO
Inventors: 李向国; 王建新
Original assignee: 深圳市高视达电子有限公司
Priority date: 2020-03-05
Filing date: 2020-07-21
Publication date: 2021-09-10
Also published as: CN111193241A

Abstract

An immersion electric shock prevention circuit, comprising an alternating current power supply, a load circuit, an equivalent circuit in which a human body grounding point forms a loop relative to an indoor nearby grounding point, a voltage division circuit, a first switch (S1) and a second switch (S2). Two ends of the load circuit are respectively connected to a live wire and a null wire of the alternating current power supply; one end of the second switch (S2) is connected to the live wire, and the other end of the second switch is respectively connected to the equivalent circuit, one end of the first switch (S1) and one end of the voltage division circuit; 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 division circuit, the null wire and a ground wire. On the basis of the circuit, further provided is an electric shock prevention method, which is simple, reliable, effective and low in cost while achieving the effect that: when a bare terminal having strong current is soaked in water, power can still be supplied to the load and the danger that a human body is shocked during power use when being in direct contact with the water is avoided.

Description

Circuit and method for preventing electric shock due to water immersion

Technical field

The invention relates to the field of anti-leakage circuits, in particular to a water immersion anti-shock circuit and method.

Background technique

The power supply lines that are conventionally used for home installation and use on the market are the power supply form of general air switch or leakage protection switch + electric meter + multi-way leakage switch (opening) + wiring socket, although the line is simple, most of the wiring strips They do not have the function of flooding. Even after flooding, there will be a dangerous situation of electric shock caused by electric leakage. There are often sudden electric shocks or even serious tragedies that lead to death when people are using electricity. According to the statistics of the authoritative department, there are 3 to 3 per day on average. Five people died from electric shock accidents caused by electric leakage.

The existing water immersion methods or devices on the market for preventing electric shocks are relatively awkward and complex, with many components, high overall costs, and extremely high failure rates.

Some people have developed technology and products that can prevent electric shock when the terminal block socket is immersed in water, but most of them basically use input and output series connection terminals and anti-leakage conductors. The leakage conductors are surrounded by some terminals, and the leakage conductors are used To absorb the leakage current of the terminal so as to achieve the effect of preventing electric shock.

Almost all of the existing methods or devices for preventing electric shock from water immersion use a series circuit structure, and a transfer switch is added in the middle part of the input and output of the main power supply cable, which causes the practical application effect to be greatly reduced. Therefore, the maximum power of the load is also affected. The limitation of switching components, due to the limitation of the technology and cost of switching components, it is actually difficult to realize large-scale commercial and civilian production. If used improperly, such as short-circuiting the output load, it is easy to burn the switching components directly or even cause a vicious accident.

The traditional method uses a leakage-proof conductor to absorb current, and also restricts the relevant size, cross-sectional area, installation position, distance, etc. of the conductor. It is difficult to control the cost and quality of the product planned and designed under such harsh conditions. The degree is extremely poor, and the consistency is greatly compromised.

At present, there is no simple and low-cost circuit that can prevent leakage or electric shock from being immersed in water.

Summary of the invention

The present invention provides a circuit and method for preventing electric shock due to water immersion, aiming to solve the harm to the human body caused by leakage of electricity from metal terminals with strong electricity or mains electricity due to wet water due to equipment failure, operator error or other unknown physical contact.

The present invention provides a water immersion preventing electric shock circuit, which includes an AC power supply, a load circuit, an equivalent circuit formed by a human body grounding point relative to indoor perigee, a voltage divider circuit, a first switch, and a second switch, and both ends of the load circuit The live wire and the neutral wire of the AC power supply are respectively connected. One end of the second switch is connected to the live wire, and the other end of the second switch is respectively connected to one end of the equivalent circuit, one end of the first switch, and one end of the voltage divider circuit. Grounding, and the other end of the first switch is respectively connected to the other end of the voltage divider circuit, the neutral line, and the ground line.

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, and one end of the first capacitor is respectively connected to the second switch and the indoor near ground, so The other end of the first capacitor is connected to the ground point of the human body.

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 connected to one end of the second resistor and one end of the second capacitor, and the other end of the first switch The other end of the second resistor and the other end of the second capacitor are respectively connected.

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

As a further improvement of the present invention, the first switch and the second switch are interlock switches.

The present invention also provides a method for preventing electric shock by immersion in water, which includes the following steps:

S1. During the positive half cycle of the sine wave generated by AC power, control the first switch to close, the second switch to open, 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. During the negative half cycle of the sine wave generated by AC power, control the first switch to open and the second switch to close. The two ends of the voltage divider circuit are respectively connected to the live wire and the neutral wire. The AC voltage charges the voltage divider circuit, one end of the equivalent circuit Ground, the other end of which is connected in series with the human body resistance, and the equivalent circuit charges the human body resistance.

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 during the positive half cycle of the alternating current, the resistor and capacitor formed by the second resistor and the second capacitor discharge themselves.

As a further improvement of the present invention, the step S2 includes: the equivalent circuit includes a first resistor and a first capacitor, and during the negative half cycle of the alternating current, the first capacitor is discharged through the first resistor and the human body resistance.

The beneficial effects of the present invention are: the most concise, reliable, effective and low-cost method is used to realize that when the exposed terminal with strong current is immersed in water, it can still supply power to the load, and at the same time, no electricity consumption occurs when the human body is directly in contact with water. Risk of electric shock at times. Even if the wiring block with mains power is directly thrown into the water, the human body can still touch the water and no longer cause serious electric shock damage to the human body. The product of this invention is equipped with a leakage protector, or a reclosing leakage protector or a multifunctional machine developed using the technology of the present invention, even when the switch socket on the wall is immersed by rainwater when it is electrified, it can ensure that it is suitable for the large Electricity safety for most households and military industries.

Description of the drawings

Figure 1 is a schematic diagram of the water immersion prevention electric shock circuit in the present invention;

Figure 2 is a schematic diagram of AC power generation;

Figure 3 is a power supply diagram of a single-phase transformer;

Figure 4 is the sinusoidal AC waveform of AC;

Figure 5 is a waveform diagram of the original sine voltage positive half cycle;

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

Figure 7 is a waveform diagram of the negative half cycle of the original sinusoidal voltage;

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

Figure 9 is the current trend diagram of the first half-wave cycle (positive half-cycle) after power-on;

Figure 10 is the current trend diagram of the second half-wave cycle (negative half-cycle) after power-on;

Figure 11 is a schematic diagram of the safety voltage exceeding 36V for 8mS in each half cycle in 220V 50HZ power;

Figure 12 is the current trend diagram of the third half-wave cycle (positive half-cycle) after power-on;

Figure 13 is an equivalent schematic diagram of the present invention in the positive half cycle;

14 is a schematic diagram of the current trend and voltage distribution in the positive half cycle of the present invention;

Figure 15 is an equivalent schematic diagram of the present invention in the negative half cycle;

Fig. 16 is a schematic diagram of the current trend and voltage distribution in the negative half cycle of the present invention.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and embodiments.

The circuit principle diagram of the present invention is shown in Fig. 1. The whole power supply is composed of four parts: the transformer remote line 1, the local terminal block 2, the newly added local electric shock prevention circuit 3, and the load terminal 4.

As shown in Figure 2, our commonly used alternating current, whether it is single-phase or 3-phase, the method of generating electrical energy is to drive the coil to cut the magnetic lines of force by power, and then through a series of transformation or matching, so as to output the load and Provide stable electrical energy.

Along with the power drive (the process of rotating the rotor around the spindle), a stable sine wave cycle is generated, which is divided into a positive half cycle and a negative half cycle. The amplitude represents the voltage output on the time axis. Take my country’s 220V alternating current for example, it is a 50Hz sine wave, and the corresponding period is T=20mS (changes 50 times in 1 second), as shown in the figure above, 0-π (or -10mS within T/2 Time) The phase angle corresponds to the positive half-cycle voltage output, and π-2π corresponds to the negative half-cycle voltage output. Therefore, the electrical energy transmitted on the wire, relative to the ground wire on the time axis, will be a positive voltage at one time and a negative voltage at the other.

As shown in Figure 3, the single-phase alternating current 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 relative ground potential is 0V, while the live wire (Phase line) A sinusoidal voltage is periodically output with the operation of the rotor. Our commonly used AC mains power is 220V AC 50Hz sinusoidal alternating current in my country, and 110V 50Hz or 60Hz sinusoidal alternating current in some countries. All in all, most countries use sinusoidal AC waves, and the voltage fluctuations are shown in Figure 4 on the time axis.

For the sake of intuition, we can assume that the load mounted on the user end is a pure resistive load-pure resistance. Based on this, we can draw out the equivalent circuit diagrams of the entire power supply system in the positive half-cycle and negative half-cycle respectively: as shown in Figure 6, Figure 8.

As shown in Figure 5 to Figure 8, the neutral wire N and the ground wire G1 of this line structure are connected at the far end of the transformer, and both are connected to the earth ground, which is what we call the ground wire, which is relatively safe. . The load of a normal electrical appliance is connected between the live wire L and the neutral wire N, which is the load resistance R1.

The location where an electric shock occurs is the location of the human body. When the human body touches the fire line, the human body is equivalent to a resistance. Although there is no direct connection between the location of the human body and the indoor perigee, there is a high voltage due to the ground. When touched, it will form a circuit network composed of resistors and capacitors, but the resistors and capacitors are invisible to us. The current then returns to the ground of the transformer through the ground loop, forming a complete loop system. Electric shock incident.

The circuit formed by the human grounding point G3 relative to the indoor perigee G2 contains a resistor and a capacitor structure. The resistance value of the first resistor R2 depends on the degree of insulation of the ground, such as humidity, contact area, ground conductivity, distance, etc. Many factors are related. The resistance value is generally relatively large but must exist, and the resistance value is not fixed. At the same time, there is an equivalent capacitance in parallel with it, that is, the first capacitance C1. The ground is also equivalent to one polarity of the capacitance. An invisible capacitance will also be formed between the electrode and the human body, because it is the ground and the human body. Such a structure is formed. The circuit structure in which the first resistor R2 and the first capacitor C1 are connected in parallel is compared to a sufficiently high-voltage alternating current, it is a visually non-communication and the resistance and capacitance values are uncertain. A loop, since it is a loop, it can form a current. If the current is large enough or lasts long enough to reach the limit of human perception or endurance, then an electric shock accident will inevitably occur. It is worth noting that since there are resistors and capacitors, capacitors also have the function of energy storage, so a certain voltage (electromotive force) will also be generated at both ends of the capacitor. According to the first three half-wave cycles, the principle of electric shock can be derived:

As shown in FIG. 9, 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 a 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, the first capacitor C1 may be charged with a sufficiently high voltage in the positive half cycle.

As shown in Fig. 10, since the first capacitor C1 is charged in the first half-wave period, there is still a certain voltage value on the first capacitor C1 during the second half-wave period. From Fig. 8 We can see that the negative half cycle process has been cut at this time. At this time, the negative half cycle voltage provided by the line will be applied to both ends of the human body resistance, namely U1, together with the voltage stored on the first capacitor C1. Therefore, after the negative half-cycle, both ends of the human body bear a voltage much higher than the voltage originally provided by the line itself, that is, U1>>U, but the highest voltage will not exceed 2U, that is, twice the voltage. Excessive voltage applied to the resistance of the human body will cause the resistance of the human body to become smaller rapidly, 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 danger of electric shock. , If you can’t get rid of it, it will lead to fatal accidents, which is why we feel the tingling or paralysis caused by the electric shock.

For example, in a 220V AC system, the highest peak value of its DC transient can reach 220V

Times, namely

In this way, the human body must not be able to bear it at this moment. We know that the highest voltage that the human body can withstand is a safe voltage of 36V, a 50HZ cycle sine wave, and its half-wave cycle time is 10Ms, of which the voltage range over 36V is about 8mS, so every 1 second has a cumulative time voltage of 0.8 seconds All exceed the safety voltage of 36V, as shown in Figure 11.

The third half-wave cycle is shown in Figure 12. The voltage U sent by the line is reversed again. A 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 body resistance. The reverse is The first capacitor C1 is charged, but because the voltage U2 remaining on the first capacitor C1 in the previous cycle has not been discharged, the current U1 flowing through the human body at this moment U1 = U2 + U, still far exceeds the original line voltage , It is also unbearable. The subsequent waveforms can be deduced by analogy.

In summary, in addition to the lower voltage that the human body bears during the first half-wave cycle of power-on, in the subsequent sine wave, when the human body touches the live wire L in the circuit, the human body actually bears much more than the original voltage. With the voltage of the line, the resistance of the human body is broken down in a higher voltage environment to make its resistance value lower, which aggravates the accident of being injured by electric shock and even causing death, so it is unsafe.

Based on the above-mentioned principle, the present invention improves the circuit. Through the improved design, when the human body touches the live wire or has a leakage contact or is immersed in water, the effect of reducing the voltage applied to both ends of the human body resistance is achieved, so that it can effectively reduce electric shock or accidents without electric shock, and the entire line becomes relatively Safety.

Example one:

As shown in Figures 13-16, an improved circuit for preventing electric shock when immersed in water includes an AC power supply, a load circuit, an equivalent circuit formed by a human ground point relative to the indoor perigee, a voltage divider circuit, and a first switch. S1, the second switch S2, the two ends of the load circuit are respectively connected to the live wire and the neutral line of the AC power supply, one end of the second switch S2 is connected to the live wire, and the other end is respectively connected to the equivalent circuit, one end of the first switch S1, and the voltage divider circuit The two ends of the equivalent circuit are grounded respectively, and the other end of the first switch S1 is respectively connected to the other end of the voltage divider circuit, the neutral line, and the ground line.

The equivalent circuit includes a first capacitor C1 and a first resistor R2. 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. The first capacitor C1 The other end 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. The other end of the first switch S1 is respectively connected to the second resistor R3. The other end, the other end of the second capacitor C2.

The first switch S1 and the second switch S2 are interlock switches, which can be switches such as relays or thyristors. .

Embodiment two:

As shown in Figure 13, on the basis of the original power circuit, the first switch S1 and the second switch S2 are added. The switches can be in the form of a relay or a thyristor: in the positive half cycle, we control it through the circuit Let the first switch S1 close, and the second switch S2 open; in the negative half cycle, we use the circuit control to make the first switch S1 open and the second switch S2 closed. 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 indeed be affected or sacrificed, but overall it does not affect the actual leakage detection function of the original line .

In the positive half of the cycle, the first switch S1 is closed, the remote ground G1 of the transformer and the indoor perigee G2 are short-circuited, the second capacitor C2 and the second resistor R3 constitute a self-discharge; the indoor perigee G2 and the live line (phase line) L The second switch S2 in the middle is turned off, and U charges the first capacitor C1 through the resistance of the human body.

The current trend and voltage distribution in the positive half cycle are shown in Figure 14. U is the human body resistance and the first resistor R2, the first capacitor C1 parallel circuit for series charging, U2 is the indoor perigee G2 and the human body ground point G3. Voltage, U1 is the voltage across the resistance of the human body, then U=U1+U2, the voltage carried on both ends of the human body is U1=U-U2, which is less than U. At this time, there is no difference from the voltage carried on both ends of the human body in the positive half cycle of Fig. 9. All subsequent The positive half of the cycle is exactly the same as the first positive half of the power-on before the improvement is U1=U-U2. The load voltage across the human body in the subsequent positive half of the cycle before the improvement is shown in Figure 12 as U1=U2+ U, this is also a very different point of improvement.

Embodiment three:

As shown in Figure 15, in the negative half cycle, the first switch S1 is turned off, that is, the remote ground G1 of the transformer is disconnected from the indoor perigee G2, but there still exists a ground resistance, that is, the second resistance R3 and the ground capacitance, that is, the second The capacitor C2 is connected in parallel and then connected in series between the remote ground G1 and the indoor perigee G2; the second switch S2 between the indoor perigee G2 and the live line (phase line) L is closed; the human body ground point G3 passes through the parallel first resistor R2 and the second switch S2 A capacitor C1 is connected in series.

The current trend and voltage distribution during the negative half cycle are shown in Figure 16. U is the second resistor R3 and the second capacitor C2 charging, at this time U=U3; since L is short-circuited with the human body ground point G3, the first capacitor C1 Discharge through the first resistor R2 and the human body resistance. At this time, the human body carries a voltage U1=U2, which is also less than U.

The subsequent cycles repeat the above positive and negative half-week regular cycle. From this we can see that after the improvement, regardless of the positive half-cycle or the negative half-cycle, the voltage actually carried on both ends of the human body resistance is much smaller than before the improvement. So as to reduce the damage of being electric shocked or not, so as to prevent accidents caused by electric shock.

Through the principle analysis of the invention and the actual application effect test results, it is finally found that the reason why the existing line structure layout will cause a more serious electric shock accident is mainly because the fixed position of the human body ground point causes the human body to withstand a long distance. The voltage exceeding the power supply causes the occurrence of electric shock, which is also determined by this fixed power supply structure. However, we can change the relative position of the grounding point where the human body is located in the power line loop. By reducing the leakage voltage loaded on the resistance of the human body, and by changing the power supply structure of the original line as much as possible, the flow in the unit time can be reduced accordingly. The current of the human body to reduce the electric shock or the inability to perceive the electric shock.

Through actual improvements and application tests, we will improve the power supply wiring board device, in the case of bare power supply, immersed in water can also be used to supply power to various loads in normal operation. At this time, as long as the human body does not touch the live wire at the same time In the case of (phase wire) and neutral wire, people reach out to touch water or a single wire, and 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 more leakage and electric shock accidents caused by water immersion and other reasons.

The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, a number of 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

An electric shock prevention circuit when immersed in water, which is characterized in that it comprises an AC power supply, a load circuit, an equivalent circuit formed by a human body grounding point relative to the indoor perigee, a voltage divider circuit, a first switch, a second switch, and the load circuit The two ends of the second switch are respectively connected to the live wire and the neutral line of the AC power supply, one end of the second switch is connected to the live wire, and the other end of the second switch is connected to the equivalent circuit, one end of the first switch, and one end of the voltage divider circuit. The two ends 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 line, and the ground line.
The electric shock prevention circuit when immersed in water according to claim 1, wherein the equivalent circuit includes a first capacitor and a first resistor, the first capacitor is connected in parallel with the first resistor, and one end of the first capacitor is respectively The second switch is connected to the indoor ground, and the other end of the first capacitor is connected to the human body ground point.
The electric shock prevention circuit when immersed in water according to claim 1, wherein the voltage divider circuit includes a second capacitor and a second resistor, and one end of the first switch is respectively connected to one end of the second resistor and the second capacitor. At one end, 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.
The electric shock prevention circuit when immersed in water according to claim 1, wherein the first switch and the second switch are relays or thyristors.
The electric shock prevention circuit when immersed in water according to claim 1, wherein the first switch and the second switch are interlock switches.
A method for preventing electric shock when immersed in water is characterized in that it comprises the following steps:

S1. During the positive half cycle of the sine wave generated by AC power, control the first switch to close, the second switch to open, 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. During the negative half cycle of the sine wave generated by AC power, control the first switch to open and the second switch to close. The two ends of the voltage divider circuit are respectively connected to the live wire and the neutral wire. The AC voltage charges the voltage divider circuit, one end of the equivalent circuit Ground, the other end of which is connected in series with the human body resistance, and the equivalent circuit charges the human body resistance.
The method for preventing electric shock when immersed in water according to claim 6, wherein the step S1 comprises: the voltage divider circuit includes a second resistor and a second capacitor, and in the positive half cycle of the alternating current, the second resistor and the second capacitor constitute The RC discharges by itself.
The method for preventing electric shock when immersed in water according to claim 6, wherein the step S2 comprises: the equivalent circuit includes a first resistor and a first capacitor, and during the negative half cycle of the alternating current, the first capacitor passes through the first resistor and the first capacitor. Human body resistance discharges.