CN114204536A

CN114204536A - Single-phase power supply plug socket with lightning protection function

Info

Publication number: CN114204536A
Application number: CN202111682581.8A
Authority: CN
Inventors: 陶显芳
Original assignee: Zuo Shengqiang
Current assignee: Zuo Shengqiang
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-03-18

Abstract

The invention relates to a single-phase power plug seat with a lightning protection function, which consists of gas discharge tubes G1, G2, G3 and G4, inductors L1 and L2, piezoresistors R1 and R2, an X capacitor C1, a Y capacitor C2 and a C3. The inductors L1 and L2 are common and differential mode surge pulse suppression inductors, and the X capacitor C1 and the Y capacitors C2 and C3 are all safety capacitors. This take single phase power plug seat of lightning protection function has the function of suppressing the high-pressure surge pulse of secondary thunderbolt and to the multiple wave group surge pulse, consequently, all kinds of alternating current electronic equipment that are connected with this take single phase power plug seat of lightning protection function all can avoid the harm that secondary thunderbolt and multiple wave group surge pulse caused alternating current electronic equipment, this single phase power plug seat is connected with special earth mat, still have the function of protecting to primary thunderbolt, this take single phase power plug seat of lightning protection function, the lightning protection who is particularly suitable for high alternating current electronic equipment.

Description

Single-phase power supply plug socket with lightning protection function

[ technical field ] A method for producing a semiconductor device

The present invention relates to a single-phase ac power plug socket with lightning protection function (refer to fig. 1, fig. 1 is a basic circuit structure diagram of a single-phase power plug socket with lightning protection function), which has a function of suppressing a secondary lightning high-voltage surge pulse generated by a power supply system and a multi-wave group surge pulse, and all kinds of ac electronic devices connected to the single-phase ac power plug socket with lightning protection function can avoid the secondary lightning high-voltage surge pulse generated by the power supply system, the single-phase power supply plug seat is connected with a special ground network and also has the function of protecting against one lightning stroke, and the single-phase AC power supply plug seat with the lightning protection function is particularly suitable for various advanced AC electronic equipment systems powered by an AC power network.

[ background of the invention ]

At present, many AC power supply plugs and sockets do not have a lightning protection function, namely, a function of preventing secondary lightning high-voltage surge pulse and multi-wave group surge pulse generated by a power supply system from damaging AC electronic equipment.

Because a three-phase four-wire system (TN-C) is adopted by a power transmission system of a power grid in China, namely three live wires and a neutral wire are adopted to supply power to an alternating current load, a high-voltage transmission line is generally of an overhead structure and is easy to be struck by lightning, so-called lightning strike is that charged clouds in the sky discharge to the earth, the charged clouds in the sky (called thundercloud for short) are equivalent to a charged capacitor, the earth is equivalent to a charged capacitor, when the potential difference of the two capacitors reaches a certain height, the two capacitors can mutually generate discharge, and the discharge process is called lightning strike (primary lightning strike).

Through a large amount of data statistics and calculation, the thundercloud can be regarded as an isolated capacitor with the capacity of about 10-100 microfarads, but the capacitance of the thundercloud is related to the structure and the volume of the cloud body, so that the capacity range of the thundercloud is very large in change, and the capacity of the thundercloud even far exceeds the range given above.

The capacity of the thundercloud isolated capacitor can be calculated according to the following formula:

in the above formula, u_cThe potential of the thundercloud, which is a function of time during the process of discharging with the earth, U_mThe initial voltage or the highest voltage for charging thundercloud, R is a lightning grounding resistor, wherein the lightning grounding resistor also comprises a gas discharge resistor, the value of the gas discharge resistor is about 4-10 ohms, and the size of the grounding resistor and the material structure of the earth surfaceThe resistance value of R is not a fixed value because of the dependence on the carrier density during the discharge of the Raynaud; c is a thundercloud capacitor, RC is a time constant in the thundercloud discharging process, and u is a time constant in the discharging process of the thundercloud and the earth_cThe capacity of the thundercloud capacitor can be estimated by indirect measurement of the voltage.

For u is paired_cAn indirect measurement of the voltage can be obtained by erecting a metal rod parallel to the rod beside the rod, as shown in fig. 2, when the rod is struck by lightning, by mutual induction, a pulse voltage waveform proportional to the discharge pulse of the rod will be induced in the parallel rod, and when the time Δ t is equal to the time constant RC, u is equal to_cExactly equal to U_m37% (i.e., 1/e), knowing that Δ t corresponds to 0.37U_mThe size range of the capacitor C can be easily estimated by the value of Δ t ═ RC and the resistance R (4 to 10 ohms, dynamic resistance).

Fig. 2 is a diagram of the operational principle of monitoring the thundercloud and earth discharge process and a graph of current (or voltage) waveforms. Fig. 2 shows on the left a schematic diagram of the operation of monitoring the current (or voltage) flowing through the lightning rod by means of electromagnetic induction with the current (or voltage) flowing through the metal rod; the waveform on the right of fig. 2 shows a current curve during thundercloud and earth discharge. In the process of discharging thundercloud and the earth, the number of ions is continuously increased at the beginning, the discharge intensity is continuously increased along with the increase of the number of the ions, after the amplitude of the waveform reaches the maximum value, the charge carried by the thundercloud starts to be continuously reduced, and the discharge intensity of the thundercloud starts to be reduced.

Because the number of the ions participating in the discharge is unstable, ionization is generated while compounding, so that the discharge waveform curve of the thundercloud in fig. 2 is slightly different from the general RC charge-discharge waveform curve, because the R value in the thundercloud discharge process is also unstable, but the estimation of the capacitor capacity is not influenced, in addition, the capacitance calculated by the waveform curve of fig. 2 belongs to dynamic capacitance, because the thundercloud discharges when the density of the ions is too low, the discharge is ended in advance, and at this time, the charges carried by the thundercloud are not completely discharged.

When the thundercloud and the earth generate discharge, the potential difference between the thundercloud and the earth is in direct proportion to the height from the surface of the earth, because the minimum value of the creepage distance of the air is about 1000V/1mm, the potential difference between the thundercloud and the earth can be easily calculated according to the distance between the thundercloud and the ground, for example, the distance between the thundercloud and the ground is 1000 meters, and the potential when the thundercloud and the earth generate discharge is about 10⁹In volts.

The charge of the cloud is related to the volume of the cloud, the density of water vapor in the cloud is generally high before the cloud discharges, and the cloud can be regarded as a solid, the larger the volume, the larger the surface area, and the larger the surface area, the more the cloud accumulates, because the charge density of the charged object is not uniformly distributed, the charge is mainly concentrated on the surface of the object, and the charge is equal to the surface area of the object multiplied by the charge density, or equal to the capacitance (isolated capacitance) multiplied by the potential difference. The more the charge of the cloud belt, the greater the intensity of the discharge, and the potential difference is the potential difference (voltage) between the surface of the isolated capacitor (charged body) and the center of the charged body, because the potential of the center of any charged body is equal to 0.

The earth also behaves as a charged isolated capacitor whose capacitance is equal to the surface area of the earth divided by the radius of the earth multiplied by the dielectric constant, i.e.:

the radius of the earth is equal to 6400km, and the dielectric constant epsilon of the air₀＝8.85×10^-12(F/m) is substituted into the above formula, the capacity of the earth isolated capacitance is about 71140 microfarads, but the medium on the earth surface is not completely pure air, and contains a large amount of water vapor, so that the dielectric constant ε in practice_rMuch larger than epsilon in the above formula₀Much larger, i.e., the capacity of the earth's isolated capacitance is much larger than 71140 microfarads, where we do not have to keep up with the actual dielectric constant ε at the earth's surface_rTo be more realistic, we only here aim to treat the earth as an isolated electricityAs will be appreciated.

Two isolated capacitors C₁、C₂Mutual inductance coefficient of electric field between C₁₂It is equal to the capacitance of a capacitor formed by the two isolated capacitances, whose value is equal to the series connection of the two isolated capacitances, i.e.:

in the above formula, C₁₂The capacitance (mutual inductance of electric fields), C, of a capacitor formed by two isolated capacitors₁、C₂The capacities of two isolated capacitors, respectively.

The earth surface is negatively charged, and can be obtained by measuring and calculating parameters such as potential gradient, current density, conductivity, charge density and the like on the earth surface.

According to experimental measurements, the magnitude of the electric field E perpendicular to the earth's surface is approximately equal to 100 v/m, but decreases with increasing altitude, and becomes very weak when the altitude reaches above approximately 50 km. This is because, on the one hand, the electric field intensity generated by the earth's surface electrification decreases with increasing distance, and on the other hand, an ionosphere having a high ion concentration exists in the air, and the inner layer of the ionosphere is positively charged and the outer layer is negatively charged, which corresponds to a capacitor charged between the earth's surface and the ionosphere, and therefore, the electric field intensity must be equal to 0 at a position between the earth's surface and the ionosphere.

Through experimental tests, the conductivity σ of the atmosphere near the ground₀About 3X 10^-14Siemens/m, and increases with increasing altitude, from which it is known that the current density j at the earth's surface, pointing towards the geocenter, has the magnitude:

j＝σ₀E——(4)

from this, the total current intensity I flowing from the atmosphere to the earth's surface is found to be:

I＝j4πr²——(5)

substituting the radius r of the earth into 6400km, the outer space per unit area can be obtainedThe current intensity injected into the earth at every moment is 1.5 multiplied by 10³Amperes, which corresponds to cosmic space providing approximately 615 megajoules of energy to the earth every second, and some of this energy is converted to lightning.

The earth's surface is negatively charged and its potential is approximately negative 41 tens of thousands of volts (relative to the earth's center), which can be obtained by the following two equations:

charge on the earth's surface:

epsilon in the above formula₀Is the dielectric constant of air, if₀＝8.85×10^-12(F/m) is substituted into the above formula, and the earth is regarded as an isolated capacitor, and the capacity is about 71140 microfarads, then the potential is obtained as:

but due to the dielectric constant epsilon of the earth's surface_rNot exactly equal to the dielectric constant ε of air₀But is slightly larger than epsilon₀Namely: epsilon_r＞ε₀Therefore, the capacity of the earth isolated capacitor is slightly larger than 71140 microfarads, and if the substances between the earth surface and the ionized layer can be regarded as the dielectric medium between the two plates of the capacitor, the earth surface and the ionized layer can be regarded as a charged capacitor.

The ionosphere is not strictly separated from the earth surface, is located in a space of 60-3000 km above the earth surface and consists of gas substances charged by ionization, can be regarded as a polarized charged layer, the outer layer of the polarized charged layer is negatively charged, and the inner layer of the polarized charged layer is positively charged, because the cosmos space continuously radiates negatively charged microparticles to the atmosphere, and the earth surface is negatively charged and two electric fields interact with each other.

If the earth surface and the ionosphere are regarded as two plates of a capacitor, since the dielectric medium between the two plates of the capacitor also belongs to a polarized charged body, there must be a potential equal to 0, and the capacitance of the capacitor is about 1.1 farad (the calculation process is omitted) according to the distance between the 0 potential and the earth surface and the value of the dielectric constant, so that the voltage of the earth surface with negative charge can be obtained as follows:

U_r≈-4.1×10⁵(volt) -relative to the Earth's center (8)

Where Ur and U₀Is not equal, and Ur < U₀This indicates that the capacitance of this isolated capacitor of the earth is actually much larger than 71140 microfarads due to the dielectric constant ε_rSpecific dielectric constant ε of air₀For the reason that the air contains a large amount of water vapor.

Because the earth surface is negatively charged, when thundercloud approaches the earth surface, firstly, the thundercloud is induced by an electric field generated on the earth surface to generate polarized charge, namely, the upper half part of the thundercloud is negatively charged, the lower half part of the thundercloud is positively charged, and the middle part of the thundercloud is uncharged, when the polarized charged thundercloud is separated into two parts under the action of wind force, the thundercloud generates separated charge, the originally polarized charged cloud is separated into two independent bodies with different charges, the upper part of the independent bodies is negatively charged, and the lower part of the independent bodies is positively charged, but as the thundercloud can also receive negatively charged microparticles which are continuously radiated to the earth by a cosmos space, the charge density of the negatively charged thundercloud is continuously improved, and the potential (absolute value) of the negatively charged thundercloud is also continuously improved, namely, the proportion of the negatively charged thundercloud is higher than that of the positively charged thundercloud.

When charged thunderclouds discharge to the earth, firstly, air is ionized to generate ions, the gas is ionized into two parts under the action of a strong electric field, one part is positively charged and is called positive ions, the other part is negatively charged and is called negative ions, when the potential difference between the two differently charged thunderclouds is large enough, the two differently charged thunderclouds can mutually discharge, bright light can appear in the process of discharging the gas, and the phenomenon is called lightning.

When the potential difference between the charged thundercloud and the earth is high enough, the thundercloud and the earth also discharge, and when the discharge is generated between the thundercloud and the earth, an object higher than the surface of the earth is firstly discharged, which is called as primary lightning stroke. The outdoor power grid transmission line is generally higher than the ground, and the relative distance between the outdoor power grid transmission line and the ground is longer, so that the probability that the outdoor power grid transmission line is struck by lightning is relatively higher, and secondary lightning strike is easily caused when the outdoor power grid transmission line is struck by lightning.

When the thundercloud and the power transmission line near the transformer substation generate discharge (primary lightning strike), hundreds of thousands of amperes of current are injected into the earth through a lightning protection device (generally a gas discharge tube) installed on the power transmission line, the grounding resistance of the lightning is generally about 4-10 ohms, hundreds of thousands of amperes of current generate tens of and millions of volts of grounding voltage (surge voltage) on the ground, and since a neutral line in the power transmission line is generally connected with the ground (in order to prevent a transformer coil from being broken down by the lightning), tens of and millions of grounding voltage pulses generated on the grounding resistance enter a power grid through the neutral line, so that secondary lightning strike is caused, as shown in fig. 3.

FIG. 3 is a diagram of the operation of a secondary lightning strike generated by a lightning impulse current through a ground resistance. As can be seen from the figure, the surge pulse voltage generated by the secondary lightning stroke is generated by the voltage drop generated on the grounding resistor by the grounding current and then transmitted to the load through the neutral line. The amplitude of the surge pulse voltage is related to the amplitude of the grounding current, the size of the grounding resistor and the distance from a lightning grounding point to a transformer substation (power transmission transformer), and the disaster caused by the secondary lightning stroke is more serious the closer the lightning grounding point is to the transformer substation.

In fig. 3, the lightning high voltage pulse on the neutral line is also transmitted to the live line by conducting discharge of 3 gas discharge tubes (shown by dotted lines) connected behind the secondary coil of the transmission transformer, and at the same time, the lightning high voltage pulse on the primary coil of the transformer is also transmitted to the secondary coil of the transformer by the distributed capacitance between the primary coil and the secondary coil of the transmission transformer, at this time, in the output circuit of the secondary coil of the transformer, a common mode surge pulse voltage and a differential mode surge pulse voltage are generated and propagated on the transmission line, but the amplitudes of the lightning high voltage pulses on the live line and the neutral line are different from each other with respect to the ground, and the energies are different from each other, and since the load resistance on the live line is much larger than the load resistance on the neutral line with respect to the ground, the attenuation speeds of the two common mode surge pulses are different, and the attenuation speed of the lightning high voltage pulse on the live line is slower than the attenuation speed of the lightning high voltage pulse on the neutral line, the energy is much smaller.

Fig. 4 is a probability curve of lightning surge current amplitude in our country, which is basically distributed according to the exponential function rule of e. From fig. 3, it can be known that the probability of 30 ten thousand amperes surge current generated by the first lightning stroke is about 0.1%, and the probability of 20 ten thousand amperes surge current is about 1.2%, which indicates that the risk of the ac electronic equipment being struck by the second lightning is still relatively large.

Most of lightning surge pulse voltages are only 50-100 microseconds (one lightning stroke), the wider the lightning surge pulse voltage is, the larger the energy contained in the lightning surge pulse voltage is, the speed of the amplitude attenuation of the lightning surge pulse voltage is related to the time constant of the thundercloud and the earth discharge and the speed of the surge current transmitted in a conductor, and because the lightning high-voltage pulse is transmitted on a line, the lightning high-voltage pulse is also discharging a ground resistor, so that the amplitude of the lightning high-voltage pulse is also continuously attenuated.

The speed at which the lightning surge pulse current propagates in the conductor may be determined by:

in the above formula: v_dFor the speed of current propagation in the transmission line, V_cAs the speed of light, μ is the magnetic permeability and ε is the dielectric constant. In practical application, V_dThe size of the magnetic permeability mu and the dielectric constant epsilon can be tested, for example, the telecommunication measurement of the fault of the underground communication cable is that the fault position of the cable is calculated through the phase of the pulse echo, and the magnetic permeability mu and the dielectric constant epsilon can be tested by using the instrument.

In thunderstorm days, the humidity of the air on the earth surface is relatively large, the air contains a large amount of water vapor, the dielectric constant epsilon is relatively large (the dielectric constant of water is 81), and the magnetic permeability mu of the substances on the earth surface is far greater than 1, so that the speed of the current propagating in the power transmission line is generally only a fraction to a tenth of the speed of light; the current travels more slowly in earth on the earth's surface, typically only a few tenths to a few hundredths of the speed of light, because there is not only moisture but also a large amount of other paramagnetic substances, especially ferromagnetic substances with high magnetic permeability.

The slower the current propagation speed, the faster the speed of its decay, because the propagation of the lightning surge pulse is propagated by the law of displacement current, which is proportional to the potential gradient dV/dX and inversely proportional to the magnitude of the load resistance R, where V is the potential and X is the distance, the potential gradient can also be written as Δ V/Δ X, i.e. the potential gradient is the ratio of the potential increment Δ V to the distance increment Δ X, also known as the potential difference per unit distance.

When the lightning surge pulse voltage completely enters the power transmission line, the displacement current can be transmitted along two directions, namely forward transmission and backward transmission, namely, the transmission directions of the two displacement currents are just opposite, and the corresponding displacement current is larger at a place where the slope (potential gradient) of the pulse voltage waveform is larger because the potential gradient signs of the front edge and the back edge of the lightning surge pulse are opposite; conversely, the smaller the slope of the pulse voltage waveform is, the smaller the corresponding displacement current is, and the displacement current is also equal to 0 since the potential gradient at this point is equal to 0 (the slope is equal to 0) at the maximum amplitude of the lightning surge pulse voltage.

Fig. 5 is a schematic diagram of two displacement currents with opposite directions generated in a power transmission line by secondary lightning surge pulses, namely, a surge pulse voltage waveform generated on a grounding resistor by lightning grounding pulse current and two displacement currents, namely, a forward propagating waveform and a backward propagating waveform.

Two displacement current pulses shown in FIG. 5 are each represented by i_fAnd i_bIs shown, wherein the displacement current pulse i_fPropagating forward, displacing current pulses i_bTo the rearSpreading; d represents distance, V represents velocity, and τ represents pulse width.

Two displacement current pulses propagated by lightning in a transmission line generally only one of the two displacement current pulses causes secondary lightning damage to electronic equipment, and the other displacement current pulse is propagated along the opposite direction of the high-voltage transmission line or along the surface of the earth after falling to the ground.

In the process of transmitting two displacement current pulses generated by secondary lightning stroke, because the displacement current pulse load resistance transmitted backwards along the earth surface is a ground resistor, the resistance value is relatively small and is only 4-10 ohms, and the displacement current pulse load resistance transmitted forwards is relatively large, the descending amplitude and descending speed of the front edge and the rear edge of the surge pulse voltage waveform are different, and the speed of the surge current pulse transmission is related to the dielectric constant epsilon and the magnetic permeability mu (refer to formula (9)).

Therefore, the voltage amplitude of the surge pulse which correspondingly propagates forwards is slower than the voltage amplitude of the surge pulse which propagates backwards, but the attenuation rule of the voltage amplitude of the whole lightning surge pulse basically attenuates according to the exponential function rule, and the process is equivalent to that a fully charged capacitor discharges to a grounding resistor, and only the time constants (RC) of the front edge and the rear edge of the waveform which correspondingly discharge are different.

During the propagation process of the lightning surge pulse, although the lightning surge pulse is attenuated according to the law of an exponential function, the RC constant in the formula (1) is not the RC time constant when the thundercloud is initially discharged, because the thundercloud discharge process is basically finished, the RC time constant at the moment is mainly the RC time constant variable formed by the earth surface distributed resistance and the distributed capacitance, the RC time constant at the moment is a variable of a divergent formula, namely R is reduced along with time (or distance), and C is increased along with time (or distance).

The end result is that the amplitude of the whole lightning surge pulse voltage will decrease rapidly, the pulse width will increase continuously, and the amplitudes of the two displacement currents will decrease, because the potential gradient decreases with the decrease of the amplitude of the surge pulse voltage and the increase of the pulse width, and the speed of the amplitude decay of the lightning surge pulse voltage basically decays according to an exponential function law, only the time constant RC is also a variable.

In fig. 5, as the propagation distance increases or the time becomes longer, the amplitude of the lightning surge pulse voltage decreases and the pulse width widens, which can also be regarded as two displacement currents i_fAnd i_bAs a result of the force applied to the waveform (the waveform changes as shown by the dotted line), or in other words, during the transmission of the lightning surge pulse, the waveform is distorted, the amplitude is reduced, and the width is widened.

In order to estimate the effective distance of the lightning surge impulse voltage propagation, it is assumed that the amplitude of the lightning surge impulse voltage is linearly attenuated (actually, exponentially attenuated) along with the propagation distance or time, the initial width of the impulse voltage waveform is 100 microseconds (maximum), the propagation speed of the displacement current on the power transmission line is one tenth of the light speed, that is, the propagation speed of the displacement current is 30 meters per microsecond, and only one of the displacement currents causes secondary lightning damage to the alternating current electronic equipment due to the fact that the propagation directions of the two displacement currents are opposite.

Therefore, we can simply divide the pulse width of the lightning surge voltage into two parts, namely, one 50-microsecond surge pulse voltage is propagated forwards, and the other 50-microsecond surge pulse voltage is propagated backwards, and although the load resistances of the two surge pulse voltages are completely different, we do not consider the difference between the two surge pulse voltages.

Assuming that the amplitude of the lightning surge pulse voltage is reduced by 90% and the width of the corresponding lightning surge pulse voltage is also increased by 90%, that is, the width of the lightning surge pulse voltage is increased from 50 microseconds to 500 microseconds, therefore, it can be obtained that the effective propagation distance of the lightning surge pulse voltage on the power transmission line is 15 kilometers (the amplitude is reduced by 90%), that is, within 15 kilometers from the lightning landing point, all the alternating current electronic products connected with the power grid have the risk of being struck by a secondary lightning, but on the power transmission line of 15 kilometers, the amplitude of the lightning surge pulse voltage is different, the distance (or time) is farther, the amplitude of the lightning surge pulse voltage is larger, and as the distance (or time) increases, the amplitude of the lightning surge pulse voltage becomes smaller and smaller, theoretically, the distance of the lightning surge pulse voltage propagation is infinite, but as the distance of the lightning surge pulse voltage increases, its harm to the electronic equipment will also be less and less.

In the same way we estimate the maximum effective distance of backward propagation of the lightning surge pulse voltage, which is only 0.75 km above ground if we assume that the speed of propagation of the surge current at the earth's surface is 200 times lower than the speed of light. In addition, the lightning surge pulse voltage is lossy when propagating on the earth surface, and the loss is very large, because the lightning grounding resistance is only 4-10 ohms, according to experimental test data, the effective distance of the lightning surge pulse voltage propagating on the earth surface is less than 500 meters, but within the range of 30 meters from the lightning strike landing point, the maximum step voltage generated by the lightning surge pulse voltage is up to 2 ten thousand volts per meter (according to fig. 4).

In practical application, the secondary lightning surge pulse voltage applied to the power input end of the alternating current electronic equipment is the potential difference between the lightning surge pulse voltage on the power transmission line of the power grid and the lightning surge pulse voltage on the earth surface, so that the maximum value of the potential difference between the two surge voltage pulses is near the position 500 meters away from the lightning landing point.

The lightning surge pulse voltage is also lossy on the transmission line, but the loss generated by the transmission of the lightning surge pulse voltage on the earth surface is much smaller because the load impedance of the two is different, and in addition, the width of the lightning surge pulse voltage waveform cannot be simply divided into two halves, because the displacement current density relative to the grounding end of the neutral line is relatively larger, and the displacement current density relative to the other end of the neutral line for transmission is relatively smaller, which is equivalent to that the backward transmission power of the lightning surge pulse voltage is much larger than the forward transmission power, but the loss is basically provided by the whole lightning surge pulse electric energy, so that finally, the maximum effective distance of the transmission of the lightning surge pulse voltage on the transmission line is considered to be less than 15 kilometers, or the maximum distance is only 15 kilometers (the amplitude is attenuated by 90%).

According to the analysis, the secondary lightning stroke is mainly generated by the voltage drop generated by the lightning surge pulse current through the grounding resistor, the surge pulse voltage generated by the grounding resistor is mainly transmitted through the center line of the power transmission line, the maximum effective distance of the transmission is only about 15 kilometers (the amplitude is attenuated by 90%), and the effective distance of the transmission of the lightning surge pulse on the power transmission line is related to the transmission speed of the current.

At present, most of high-voltage transformer substations in big cities in China are built in suburbs of cities, and have a certain distance from residential areas of residents in the cities, and most of low-voltage lines are buried underground, which is beneficial to lightning protection.

In China, due to the fact that people have insufficient understanding on the principle of lightning production, lightning protection technology is relatively backward, and the economic loss caused by lightning strike is up to hundreds of billions of yuan or even hundreds of billions of yuan every year. For example, 22 months 6 in 1992, multiple computer interfaces of the Beijing national weather center are damaged by induced lightning, so that more than two thousand yuan are lost; in 2011, 23 nights in 7 months and D301 trains and D3115 trains on the Hangzhou deep railway line, rear-end accidents occur due to lightning strikes, and the direct economic loss is 4 hundred million and more; in 2011, in 1-8 months, economic direct loss caused by thunder and lightning in Shenzhen city reaches more than 6000 ten thousand yuan, and economic loss caused by thunder and lightning disasters increases every year, but until today, damage and protection of thunder and lightning by many people basically have no concept, and most people have insufficient knowledge on the concept.

The national understanding of lightning protection is relatively late, the national understanding is basically realized gradually only after a very large lightning accident, and particularly, the lightning protection awareness of people in China is continuously improved by carrying out technical communication with advanced technical countries after a WTO (wire train operator) is added.

At present, China has already made many technical standards for protecting electronic products against surge pulse voltage, such as GB/T17626.5-1999 (equivalent to international standard IEC61000-4-5-1995) and surge characteristic test technical specification (equivalent to international standard IEEE Std C62.41.2) in low-voltage alternating-current power supply (not higher than 1000V), and the technical requirements of the test standard on surge voltage are respectively: 0.5kV, 1kV, 1.5kV, 2kV, 4kV and 6kV and the current is 0.25-3 kA, but the technical standards for surge pulse protection are still relatively low in the aspect of lightning protection technology, and the lightning protection technical requirements of most electronic product users are difficult to meet.

Fig. 6 is a working principle diagram of a surge pulse voltage protection technical standard (GB/T17626.5-1999) widely adopted in China for testing electronic products, fig. 7 and 8 are voltage and current output waveforms of fig. 6, respectively, and a single pulse energy at 4kV is 100 joules.

In fig. 6, Cs is an energy storage capacitor (about 10uF, which corresponds to a thundercloud capacitor), Us is a high voltage power supply, Rc is a charging resistor, Rs is a pulse duration forming resistor (a discharge curve forming resistor), Rm is an impedance matching resistor, and Ls is a current rise forming inductor. The lightning surge immunity test has different parameter requirements on different products, and the parameters in the upper graph can be slightly changed according to different height requirements of the product technical standard.

Fig. 7 is the waveform and basic parameters of the output pulse voltage of fig. 6, the surge voltage pulse basic parameters require:

(1) open circuit output voltage: 0.5-6 kV, outputting in 5 grades, and determining the last grade by negotiation between a user and a manufacturer;

(2) short-circuit output current: 0.25-3 kA for different grades of tests;

(3) internal resistance Rm: 2 ohms, and

additional resistors

10, 12, 40 and 42 ohms for other tests of different grades;

(4) surge output polarity: positive/negative; when the surge output is synchronous with the power supply, the phase is shifted by 0-360 degrees;

(5) repetition frequency: at least once per minute.

Fig. 8 shows the waveform and basic parameters of the output lightning surge pulse current of fig. 6, and the requirements of the basic parameters of the surge voltage pulse can be classified into 5 grades according to the severity grade of the lightning surge immunity test:

level 1: better environment protection;

and 2, stage: the environment is protected to a certain extent;

and 3, level: common electromagnetic disturbance environment, no special installation requirement for equipment, such as industrial workplaces;

4, level: and in severely disturbed environments, such as civil overhead lines and unprotected high-voltage substations.

And (4) X level: as determined by user negotiation with the manufacturer.

GB/T shows that the standard is a recommended standard, and a user can select different technical requirements to execute according to the application environment of the user.

According to the previous process analysis of the generation of the secondary lightning stroke pulse, the waveform of the surge pulse generated in the power transmission line by the secondary lightning stroke is not as simple as the waveform of the surge pulse voltage (figure 7) and the current (figure 8) output by the equivalent circuit of figure 6, and if the secondary lightning stroke pulse is discharged through thundercloud and the ground, the ground current generates a voltage drop on the ground resistor and enters the power transmission line system through the grounded neutral line, the waveform of the pulse voltage and the current generated by the secondary lightning stroke is not as simple as the waveform of figures 7 and 8.

The amplitudes of the waveform pulse voltage and current waveforms of fig. 7 and 8 are relatively low, and if the lightning pulse is transmitted from a remote place, the amplitudes and widths of the waveform pulse voltage and current waveform will be different from the original input waveform and not proportional to the original input waveform, and after the lightning pulse voltage is transmitted from a remote place, the amplitude of the pulse waveform will be reduced to be very low, but the pulse width will be very wide. It can be concluded that the waveforms of fig. 7 and 8 are pulse voltage and current waveforms generated by surrounding transmission lines through electromagnetic induction when lightning strikes through a building (including a lightning rod) or a tree, and the waveforms are substantially similar to the operation principle and waveforms of fig. 2.

Therefore, the waveforms of fig. 7 and 8 are pulse voltage and current waveforms induced in the transmission line by the lightning through electromagnetic induction, and this lightning strike phenomenon we can refer to as an induction lightning.

It can be seen from this that the lightning stroke phenomenon corresponding to fig. 6 is only one of many lightning strokes, the waveform of the surge pulse voltage generated by the inductive lightning in the power transmission line is much simpler than that generated by other secondary lightning strokes, and the energy (100 joules) of the inductive lightning is much smaller than that generated by other secondary lightning strokes.

In recent years, a variety of ac power connectors with a lightning protection function as shown in fig. 9 and 10 have begun to be popularized in the market, and such power connectors are basically products imitating foreign technologies, but the internal structures and circuits are not completely the same, and mainly domestic products all use piezoresistors instead of gas discharge tubes. In foreign countries, people refer to the lightning arrester with the circuit structure as an SPD Surge protector (short lightning arrester), and the SPD is an abbreviation of the english alphabet of the Surge Protective Device and means the Surge protector.

Fig. 9 is an electrical schematic diagram of an ac power plug socket with lightning protection function, wherein the voltage dependent resistors VR1 and VR2 in fig. 9 belong to nonlinear semiconductor devices, the impedance thereof is nonlinear, when the voltage applied to two ends of the voltage dependent resistor exceeds a certain value, the voltage dependent resistor is turned on, the dynamic resistance thereof becomes very small, most of the surge current passes through a current loop formed by the voltage dependent resistors, and the functions of shunting the input circuit of the power plug socket and reducing the output voltage are performed, thereby performing the function of overvoltage protection on the electronic equipment connected with the ac power plug socket at the back.

The SPD surge protector shown in fig. 9 is, in principle, effective in protecting against the operating schematic diagram (fig. 6) used in the GB/T17626.5-1999 surge impulse voltage protection technical standard for testing electronic products, and the corresponding technical parameters shown in fig. 7 and 8.

For example, for the pulse generating circuit of fig. 6, the open-circuit voltage is 6kV, the maximum short-circuit current is 3kA, if both piezoresistors VR1, VR2 in fig. 9 select breakdown voltages of 450V, the SPD surge protector shown in fig. 9 outputs the highest surge pulse voltage amplitude of 900V, which is obviously higher than 6kV but much lower than 6 kV.

Capacitor C1 in fig. 9 is typically selected as an X-ampere capacitor, whose main function is to absorb and suppress surge current and voltage, for example, capacitor C1 is selected to have a capacity of 10uF, so that the maximum value of the pulse voltage output by the circuit of fig. 6 is only 3kV, and at the same time, the surge current flowing through the voltage dependent resistors VR1 and VR2 is almost halved or smaller.

Many lightning protection power socket products currently on the market are basically designed according to the SPD surge protector circuit shown in FIG. 9. Of course, if the technical parameters of the components are properly selected, the lightning protection power socket designed according to the SPD surge protector circuit shown in FIG. 9 can basically meet the basic technical requirements of the test circuit of GB/T17626.5-1999 surge pulse voltage protection technical standard.

However, the technical indexes of the lightning protection power sockets popular in the market at present are relatively low, most of the lightning protection power sockets can only meet the requirement of bearing the highest surge pulse voltage amplitude of 1500V, namely the requirement below the GB/T17626.5-1999 standard technology level 4, most of the lightning protection power sockets can not bear the highest high voltage of 4000V, because the highest voltage-resistant parameter of the piezoresistor is generally not high, the maximum current borne by the piezoresistor is not large enough, and the internal space of the power socket is limited, so that the requirement of the insulation voltage of more than 2000V is difficult to achieve. If a gas discharge tube is exchanged, the specification will of course be much higher, since the gas discharge tube can withstand very high currents, but the cost of the gas discharge tube is relatively high, which is why the manufacturer has to take into account.

For example, a lightning protection socket (EPP 10 MS-6) of lightning protection 6 holes called Yilong lightning protection is popular in the market]The maximum surge pulse voltage amplitude is 1500V_pThe maximum withstand surge current is 10 kA. Other similar products in the market, such as a bull power lightning protection socket, have poorer technical performance than the easy dragon lightning protection 6-hole power lightning protection socket.

In addition, if the SPD surge protector circuit shown in fig. 9 is regarded as a household electronic device, the power socket does not meet the requirements of the safety standard GB8898 in China. The safety standard GB8898 requires that when AC2000V/50Hz alternating current is respectively applied to the two ends (L, N) of a power input line to the ground, the leakage current cannot be larger than 0.35mAp, or when AC2000V/50Hz alternating current is applied to the ground in a short circuit (parallel connection) mode, the leakage current cannot be larger than 0.35mAp, so that when the shell of the electronic equipment is not grounded well, a human body can be prevented from touching the shell of the electronic equipment with electricity carelessly to get an electric shock.

The voltage dependent resistor has the great defect of electric leakage, the voltage dependent resistor is divided into direct current electric leakage and alternating current electric leakage, the direct current electric leakage belongs to pure resistor electric leakage, the alternating current electric leakage is because a great distributed capacitance exists between two poles of the voltage dependent resistor, the alternating current can generate electric leakage through the distributed capacitance, if the direct current electric leakage of the voltage dependent resistor is not considered, as long as the distributed capacitance of the voltage dependent resistor is larger than 2500pF, the electric leakage index is unqualified. The distributed capacitance of the general piezoresistor is larger than 2500pF, and direct current leakage is added, the leakage currents of the two parts are mutually superposed, the safety test result is definitely unqualified, and the two leakage indexes are related to the working temperature because the piezoresistor belongs to a nonlinear device, and the temperature coefficient of the piezoresistor is generally large.

If only considering the breakdown voltage of the piezoresistor, in order to meet the requirement of the GB8898 safety standard, the breakdown voltage values of the two piezoresistors VR1 and VR2 are required to be more than 3000V, at this time, the differential mode surge input voltage is inevitably more than 6000V, the two piezoresistors VR1 and VR2 are conducted, and the surge voltage is obviously too high for electronic equipment connected behind a plug seat, because the general electronic equipment cannot bear the lightning surge pulse voltage of more than 6000Vp, the SPD surge protector circuit shown in the figure 9 does not basically inhibit the voltage and current pulse waveforms output by the figure 6, namely, the power plug seat of the SPD surge protector popular in the market at present basically does not meet the requirement of the GB8898 safety standard.

In order to make the SPD surge protector circuit shown in fig. 9 play a role of safety protection for suppressing the generation of surge pulses output by the circuit shown in fig. 6 and meet the requirement of the safety standard of GB8898, the SPD surge protector circuit shown in fig. 9 must be technically improved to the circuit shown in fig. 10 or to the circuit shown in fig. 11, and the technical performance of the circuit shown in fig. 11 is superior to that of the circuit shown in fig. 10.

Fig. 10 is an electrical schematic diagram of an ac power plug with lightning protection function, which not only meets the requirements of the GB8898 safety standard, but also can suppress and protect surge pulse voltage, in the circuit shown in fig. 10, the effect of the varistor VR3 is mainly increased to meet the requirements of the GB8898 safety standard, and after the varistor VR3 is added, the breakdown voltage of the two original varistors VR1 and VR2 can be greatly reduced. For example, during normal operation, the voltage between the live line Li and the neutral line Ni is AC220V, if the sum of the breakdown voltages of the two voltage dependent resistors VR1 and VR2 is 2.2 times of the input voltage, the sum of the breakdown voltages of the two voltage dependent resistors VR1 and VR2 can be 484V, and in the actual application circuit, the breakdown voltages of the voltage dependent resistors VR1 and VR2 can be 284V respectively, or the breakdown voltage of the voltage dependent resistor VR1 is slightly larger than the breakdown voltage of the voltage dependent resistor VR 2.

In fig. 10, the sum of the breakdown voltage of the varistor VR3 and the breakdown voltage of the varistor VR1 (or VR2) must be greater than 3000V, which can meet the requirement of the safety standard GB8898, and the varistor VR3 also absorbs the common mode surge pulse or the common mode interference signal, but this is not essential, because the circuit shown in fig. 9 can also absorb the common mode surge pulse or the common mode interference signal, and the circuit shown in fig. 9 can absorb the common mode surge pulse or the common mode interference signal more effectively than the circuit shown in fig. 10.

By analyzing from the schematic diagram alone, many people cannot notice the leakage problem of the voltage dependent resistors VR1, VR2 and VR3, especially the alternating current leakage problem of VR1, VR2 and VR3, namely the leakage of the distributed capacitance. In fig. 9, if both of the distributed capacitances of the two varistors VR1, VR2 are greater than 2500pF, then the test in accordance with the GB8898 safety standard fails, and the varistor fails even further due to dc leakage, which is highly likely because the varistor is a non-linear device with a very high temperature coefficient.

Fig. 11 is an ac power plug socket with lightning protection function using a combination of gas discharge tube and voltage dependent resistor, and the key technology in fig. 11 is to connect a discharge tube in series in the current loop of each voltage dependent resistor, which is used to make up for the deficiency of the voltage dependent resistor. Discharge tube G1 is a 3 end discharge tube, it can be equivalent to 3 discharge tubes and assemble together, 3 discharge tube's distributed capacitance is nearly zero, direct current leakage is also nearly zero, consequently, discharge tube G1 has the function of blocking 3 piezo-resistor VR1, VR2, the alternating current of VR3, direct current leakage to reduce piezo-resistor VR1, VR2, VR 3's leakage loss, another more important effect is that guarantee circuit accords with the requirement of GB8898 safety technical standard.

In addition, the gas discharge tube G1 also plays a role in preventing the power socket from being broken down and short-circuited by the high-voltage surge pulse, because when the piezoresistor is broken down by the high-voltage surge pulse, the piezoresistor is generally short-circuited due to the over-large current, and at the moment, the gas discharge tube G1 can prevent the input circuit from being short-circuited. According to the working principle of the lightning pulse shown in the figure 3, the secondary lightning surge pulse voltage generated by the lightning surge pulse through the ground resistor enters the power transmission line mainly through the neutral line, the amplitude of the lightning surge pulse voltage is generally up to thousands of volts or even tens of thousands of volts, the current intensity of the lightning surge pulse voltage is mostly thousands of or even more than tens of thousands of amperes, except for the gas discharge tube, other devices are generally difficult to bear the high voltage and current, and the probability of the phenomenon is still very high according to the probability curve of the lightning current amplitude shown in the figure 4.

However, the gas discharge tube also has a disadvantage that an ignition delay time is required when the gas discharge tube is turned on, the gas inside the gas discharge tube is ionized into ions, the discharge and the conduction can be performed after the concentration of the ions reaches a certain density, the time is about 2-8 microseconds, that is, the gas discharge tube does not work during 2-8 microseconds, and at this time, the voltage dependent resistor does not work, but in fig. 11, the capacitor C1 completely compensates for the disadvantages of the gas discharge tube and the voltage dependent resistor, the capacitor C1 can work before the gas discharge tube and the voltage dependent resistor do not work, as long as the capacity of the capacitor C1 is large enough to ensure that the voltage across the capacitor C1 does not exceed the limiting voltage of the gas discharge tube and the voltage dependent resistor before the gas discharge tube and the voltage dependent resistor do not work.

Although many new EMC technical standards including surge protection technical standards have been established for electronic products in our country for many years, these technical standards require relatively low magnitude for protection against surge impulse voltage, such as GB/T17626.5-1999 (equivalent to international standard IEC61000-4-5-1995) and surge characteristic specification (equivalent to international standard IEEE Std C62.41.2) in low voltage ac power supply (not higher than 1000V), the test standards require the magnitude of surge voltage and current to be respectively: 0.5kV, 1kV, 1.5kV, 2kV, 4kV and 6kV, and the current is 0.25-3 kA.

In practical application, the alternating current electronic equipment is often damaged by high-voltage surge pulses generated by the induction lightning corresponding to the figure 6, and under many conditions, the alternating current electronic equipment is also damaged by secondary lightning strokes with higher surge pulse voltage, even by primary lightning strokes with extremely high surge pulse amplitude, the damage degree of the primary lightning strokes to the electronic equipment is more severe than the damage degree of the secondary lightning strokes, and only the probability that the primary lightning strokes occur is relatively not as high as the probability that the secondary lightning strokes occur.

The so-called one-time lightning stroke is that thundercloud with high voltage charge directly discharges to a high-rise building, and the ground current generated by strong high-voltage pulse generates very high surge voltage pulse through a ground resistance, so that all alternating current electronic equipment in the building is seriously damaged by overvoltage through a power grid connection network or electric and magnetic induction.

GB/T shows that the standard is a recommended standard and is not a mandatory standard, the relative requirements of the standard are not very high for users, and therefore, the users can select different technical requirements to execute according to own application environments. If the AC electronic equipment is implemented according to the requirement of the technical standard, the AC electronic equipment within 15 kilometers of the lightning strike landing point in the field is still easily damaged by the lightning strike, so that the AC electronic equipment damaged by the lightning strike each year is very many, and the maintenance cost is very high, especially in suburbs and rural areas of cities.

The invention provides a power socket product with a primary lightning stroke protection function according to the requirements of users, but because the relative requirements of the installation and use technology of the power socket product with the primary lightning stroke protection function are higher, people can install services at home according to the requirements of users.

In summary, most of the existing lightning protection power sockets can only meet the following technical requirements of class 4 in the technical standard for surge pulse voltage protection of GB/T17626.5-1999 (equivalent to the international standard IEEE Std C62.41.2), that is, when the lightning protection power socket is tested by using the test circuit shown in fig. 6, the highest protection surge voltage is mostly only about 2000V, and the lightning protection power socket can only protect the surge pulse voltage generated by an induction lightning, that is, the maximum energy is less than 100 joules, the maximum pulse width is less than 100 microseconds, and most of the lightning protection power sockets do not meet the technical requirements of the safety standard of GB 8898.

[ summary of the invention ]

Aiming at the defects of poor technical performance, low surge pulse voltage and low surge current amplitude of the lightning protection power socket in the current market, the single-phase power socket with the lightning protection function overcomes the defects that the lightning protection power socket in the current market has low surge pulse voltage and surge current amplitude and is easy to be broken and damaged by lightning high-voltage surge pulses, and the like, and the single-phase power socket with the lightning protection function can bear 6kV_pThe surge pulse voltage is impacted, and the surge pulse current impact of tens of thousands of amperes can be borne, so that the risk that the alternating current electronic equipment is damaged by lightning stroke is avoided.

Referring to fig. 1, a single-phase power plug socket with a lightning protection function according to the present invention includes: (1) gas discharge tubes G1, G2, G3, G4; (2) surge pulse suppression inductors L1 and L2; (3) piezoresistors R1, R2; (4) an X safety capacitor C1; (5) y-type capacitors C2 and C3; (6) power grid input voltage socket U_i1(ii) a (7) A fuse F; (8) AC output voltage socket U_o1、U_o2、U_onN represents an arbitrary number, U_onA plurality of three-core sockets or a plurality of two-core sockets are shared;

wherein: power grid input socket U_i1The 1 end of the fuse F is connected with a live wire Li input by a power grid, and the 1 end of the fuse F is connected with a power grid input socket U_i1The 1 end of the fuse F is connected with the 1 end of the gas discharge tube G1 and the 1 end of the surge pulse suppression inductor L1;

the 2 ends of gas discharge tube G1 are connected to the 1 end of gas discharge tube G2 and the 1 end of gas discharge tube G3, respectively; terminal 2 of gas discharge tube G2 and power network input connector U _i13 end of the power grid input socket U_i1Is connected with the ground G;

2 ends of gas discharge tube G3 are respectively connected with power grid input socket U_i1And the 2 terminal of the surge suppression inductor L2, and a power grid input connector U_i1The 2 end of the power grid is connected with a central line Ni of the power grid input;

the 2 terminal of the surge pulse suppression inductor L1 is connected with the 1 terminal of the voltage dependent resistor R1, the 1 terminal of the X safety capacitor C1 and the 1 terminal of the Y safety capacitor C2 respectively, and the 1 terminal of the Y safety capacitor C2 is also connected with the AC output voltage plug socket U respectively_o1、U_o2、U_onThe 1 end of the Y safety capacitor C2 is connected with the 1 end of the Y safety capacitor C3 and the AC output voltage socket U respectively_o1、U_o2、U_onIs connected with the 3 end of the socket U for outputting voltage_o1、U_o2、U_onThe 3 ends of the two are respectively connected with the ground G;

the 2 ends of the piezoresistor R1 are respectively connected with the 1 end of the piezoresistor R2 and the 1 end of the gas discharge tube G4, the 2 ends of the gas discharge tube G4 are connected with the ground G, the 4 ends of the surge pulse suppression inductor L2 are respectively connected with the 2 ends of the piezoresistor R2 and the X safety capacitor C1, the 2 ends of the Y safety capacitor C3 and an AC output voltage socket U_o1、U_o2、U_onThe 2 ends of the two are connected;

AC output voltage socket U_o1、U_o2、U _on1 pin (hot line Lo) and 2 pins (cold line No) (n is an arbitrary value), and 3 pins (earth G) connected to the live line and neutral line and the ground line in the subscriber's socket, respectively;

the surge pulse suppression inductors L1 and L2 are inductance devices which are respectively formed by installing two inductance coils on the same iron core, the iron core adopts a structure in a shape of a Chinese character 'quan', three windows are formed, one window in the middle is shared by the two inductance coils L1 and L2, and the two inductance coils have the functions of suppressing differential mode surge pulse voltage and common mode surge pulse voltage;

the surge pulse suppression inductors L1 and L2 can be replaced by a plurality of inductors with the same structure in series connection, so that the withstand voltage and the inductance are improved, and the distributed capacitance between electrodes can be reduced;

gas discharge tubes G1, G2, G3 may be replaced by a three-terminal gas discharge tube, with the 1 end of G1 corresponding to the 1 leg of the three-terminal gas discharge tube, the 2 end of G2 corresponding to the 2 leg (middle leg) of the three-terminal gas discharge tube, and the 2 end of G3 corresponding to the 3 legs of the three-terminal gas discharge tube;

the voltage dependent resistors R1 and R2 can be respectively replaced by two TVS tubes D1 and D2, and the breakdown voltage of the TVS tubes is basically the same as that of the voltage dependent resistors, so that the technical performance of the circuit is improved, the electric leakage is reduced, and the service life of the device is prolonged;

gas discharge tube G1, G2, G3 can also be replaced by directly designing three electrode devices with saw tooth shapes respectively on the PCB, gas gaps are reserved between every two electrodes, the 1 end of G1 corresponds to the first electrode of the three-end gas discharge tube of the PCB (connected with the 2 end of a fuse F), the 2 end of G2 corresponds to the 2 nd electrode of the three-end gas discharge tube of the PCB (connected with the ground G), and the 2 end of G3 corresponds to the 3 rd electrode of the three-end gas discharge tube of the PCB (connected with the U)_i1Ni) of the 2-terminal, the breakdown voltage between the electrodes can be changed by changing the distance of each gas gap;

the gas discharge tube G4 can also be replaced by directly designing two electrode devices with saw tooth shapes on a PCB, an air gap is left between the two electrodes, one electrode corresponds to the 1 end of G4, the other electrode corresponds to the 2 end of G4, and the breakdown voltage between the two electrodes can be changed by changing the distance of the air gap;

single-phase power supply connector and power grid input voltage connector U with lightning protection function for one lightning stroke _i13 must be connected with the ground in the building structure of the user buildingAnd the ground grid is connected with the common ground of the power transmission system at multiple positions, all grounding points ensure good connection with the ground, and the distance between two connecting points is less than 20 meters.

The ground net is also called equipotential body, which is woven by strip-shaped metal wires, and the metal net woven by metal wires is generally buried in the ground, so the ground net is called ground net. In practical application, the ground net is a reinforced cement plate at the bottommost layer in a building structure, and the requirement on contact resistance between the reinforced cement plate and the ground is relatively low so as to reduce the voltage drop of lightning surge current on a grounding resistor; a plurality of connectors connected with other ground wires outside are reserved on the reinforced cement board so as to be capable of being connected with a single-phase power supply connector U with a lightning protection function_i1Is connected to the 3-terminal (ground G), and fig. 12 is an operational schematic diagram of the interconnection of the equal potential, the transmission line and the ac electronic device.

As shown in fig. 12, when the high-voltage surge pulse of the secondary lightning stroke is transmitted to the user terminal through the neutral line, since the neutral line is connected to the ground grid, it is equivalent to the same potential of the whole ground grid and the neutral line, and is also equivalent to the same potential of the ground terminal of the ac electronic device connected to the single-phase power plug socket with the lightning protection function of the present invention, thereby reducing the risk of the ac electronic device being struck by the high-voltage secondary lightning.

Fig. 12 is a simple schematic illustration, in practical application, the neutral line in the power plug socket is not directly connected to the ground grid, but is connected to the neutral line through the gas discharge tubes (G2 and G3 in fig. 1), because under normal operation, the potential of the neutral line is not necessarily equal to zero, and especially when the three-phase line is disconnected, or the load is unbalanced, the neutral line is charged, although the center tap (neutral line) of the three-phase power transformer is grounded, because there is resistance between two grounds, or when the ground is not well grounded, the ground terminal of the load is charged, the gas discharge tubes G2 and G3 in fig. 1 can serve as isolation between the neutral line and the ground, so as to prevent the neutral line from being charged and affecting personal safety, when a high-voltage pulse lightning arrives, the gas discharge tubes G2 and G3 are conducted, and when G2 and G3 are conducted, the residual voltage at both ends is relatively low, the neutral line connector in the plug seat is connected with the earth screen and has the same potential with the earth screen.

Fig. 13 is a simple structure diagram of an earth network, if overvoltage protection is to be implemented on high-voltage surge pulses generated by one lightning stroke for all ac electronic devices, it is required that a lightning rod on the top of a building must be connected with the earth network, three live wires L1, L2, L3 and a neutral wire N must be buried underground, and an iron pipe must be sleeved in the iron pipe, and the length of the iron pipe must be greater than 100 meters to prevent the high-voltage lightning surge pulses from being transmitted to other transmission lines through a local transmission line (mainly the neutral wire) to generate secondary lightning strikes for the ac electronic devices in other transmission lines, or to generate high-voltage surge pulses in the transmission lines through electromagnetic induction (induced lightning strikes), and the use method of the iron pipe is shown in fig. 14.

Fig. 14 is a schematic diagram of a system operating on an ac electronic device with a lightning strike protection function, when a lightning rod is hit by a lightning, since the lightning rod is connected to a ground grid and a resistor (about 4 to 10 ohms) is provided between the ground grid and the ground, the high voltage thundercloud discharges the lightning rod to generate a strong surge pulse current of several tens of thousands of amperes, and a high voltage surge pulse of several hundreds of thousands of volts is generated on a ground resistor and enters a power transmission system through a central line.

Because the two ends of the input and output connection wires of the power grid are respectively connected with gas discharge tubes Gx1, Gx2, Gy1 and Gy2 in a grounding mode, and the single-phase power supply plug seat with the lightning protection function has the functions of the gas discharge tubes G1, G2, G3 and G4 and piezoresistors R1 and R2, when high-voltage surge pulses of hundreds of thousands of volts are applied to the two ends of the Gy1, Gy2, G1, G2, G3, G4, R1 and R2, the high-voltage surge pulses are conducted, only relatively low residual voltage is left at the two ends of the high-voltage surge pulses, and the high-voltage surge voltage power supply plug seat is equivalent to various electronic equipment connected with the ground grid, and the potential difference among the original circuits of the high-voltage surge pulses basically keeps unchanged, so that the high-voltage surge pulses directly impact the electronic equipment is avoided.

Meanwhile, when the lightning rod is discharged by the high-voltage thundercloud, hundreds of thousands of volts of high-voltage surge pulses generated on the ground network can be transmitted to other transmission lines through the power grid connection (mainly a neutral line) if the high-voltage surge pulses are not inhibited, so that secondary lightning strike is generated on electronic equipment on other transmission lines.

In order to reduce the lightning high-voltage surge pulse generated by the local network, the transmission line is conducted through the connection line between the grounds so as to reduce the influence of the lightning surge current pulse on other equipment on the transmission line, and an effective method is needed to be adopted to isolate the local transmission network from the transmission line of the external network so as to prevent the lightning high-voltage surge pulse generated on the local network from generating secondary lightning stroke on other electronic equipment through the transmission line.

Fig. 14 is a schematic diagram of a circuit for isolating a local power transmission network from an external power transmission line to prevent a secondary lightning strike, in which a key device is a 100-meter long iron pipe buried underground, and the power transmission line (including other communication lines) must pass through the iron pipe.

Since, within a limited pulse width, the amplitude (or speed) of the lightning high voltage surge pulse attenuated in the transmission line is inversely proportional to the transmission speed, because the lightning high-voltage surge pulse is propagated on the line in a displacement current manner, one forward, one backward, while the backward propagating displacement current pulse is discharging the ground resistor all the time (the thundercloud discharges the earth's surface through the ground resistor), the amplitude attenuation speed of the lightning high-voltage surge pulse on the power transmission line is far higher than the amplitude attenuation speed of the displacement current pulse which is transmitted forwards, the speed of transmitting the lightning high-voltage surge pulse on the power transmission line is mainly reduced, the displacement current pulse which is transmitted forwards gains time in the attenuation process, and the power transmission line is sleeved in the iron pipe so as to reduce the speed of transmitting the lightning high-voltage surge pulse in the power transmission line.

Why the length of the iron pipe is selected to be about 100 meters or more, which is mainly determined by the speed of the surge current propagating in the conductor, which can be determined by the formula (9) above:

in the above formula: v_dFor the speed of current propagation in the transmission line, V_cAs the speed of light, μ is the magnetic permeability and ε is the dielectric constant.

Because the magnetic permeability of the iron pipe is very high, the value of mu is generally more than 8000, the value of epsilon is generally more than 50, and the speed of the surge current propagating in the conductor is easily estimated to be about 0.5 meter per microsecond according to the formula (9). Knowing the speed at which the surge current propagates in the conductor, the length of the iron pipe can be calculated according to the following formula:

d＝V_d×τ——(10)

the width tau of most lightning surge pulse voltage is only 50-100 microseconds, when the time is equal to tau and is equal to 100 microseconds, the length of the iron pipe is about 50 meters according to the formula (10) and the formula (1), and the corresponding u is obtained_c＝0.63U_mThat is, when the length of the iron pipe is about 50 meters, the amplitude of the lightning surge pulse voltage is attenuated by 0.63 times, or when the length of the iron pipe is increased to 2.3 times of 50 meters (i.e., 115 meters), the amplitude of the lightning surge pulse voltage is attenuated by 90%, so that the length of the iron pipe is preferably more than 100 meters.

In relation to the principle that the amplitude (or speed) of the lightning surge high voltage pulse decays in the transmission line is inversely proportional to the propagation speed, we have analyzed before and we will not repeat here.

[ description of the drawings ]

FIG. 1 is a basic circuit structure diagram of a single-phase power plug socket with lightning protection function;

FIG. 2 is a schematic diagram of the operation of monitoring the thundercloud and earth discharge processes and a graph of current waveforms;

FIG. 3 is a working diagram of a secondary lightning stroke caused by a pulse voltage generated by a lightning pulse current through a ground resistor;

FIG. 4 is a probability curve of lightning surge current amplitude in China;

FIG. 5 is a schematic diagram of two displacement currents with opposite directions generated in a power transmission line by secondary lightning surge pulses;

FIG. 6 is a functional diagram for testing electronic products (GB/T17626.5-1999);

FIG. 7 is a waveform and basic parameters of the output lightning surge pulse voltage of FIG. 6;

FIG. 8 is a waveform and basic parameters of the output lightning surge pulse current of FIG. 6;

fig. 9 is an electrical schematic diagram of an ac power plug and socket with lightning protection;

fig. 10 is an electrical schematic diagram of an ac power plug and socket with lightning protection function meeting the requirements of the safety standard of GB 8898;

fig. 11 is an electrical schematic diagram of an alternative ac power plug socket with a lightning protection function, which meets the requirements of the safety standard of GB 8898;

fig. 12 is a schematic diagram of the interconnection of the equal potential to the transmission line and the ac electronic device;

FIG. 13 is a simplified block diagram of a counterpoise;

FIG. 14 is a schematic diagram of a system for primary lightning strike protection for AC electronic devices;

FIG. 15 is a basic circuit of a single-phase power plug with lightning protection;

fig. 16 is an equivalent circuit and frequency characteristic diagram of the inductances L1, L2 and the X capacitor;

FIG. 17 is a schematic diagram of a TVS diode in place of a varistor;

fig. 18 is an equivalent schematic diagram relating the inductances L1 and L2 and the X capacitance C1.

[ embodiment ] A method for producing a compound

Fig. 15 is a basic circuit of a single-phase power plug socket with a lightning protection function designed according to the basic circuit structure of fig. 1. In fig. 15, the live line L and the neutral line N of the grid transmission line are connected to the input port U of the single-phase power plug with lightning protection function through the two-wire electromagnetic switch K (with leakage protection function) and the common ground line PE by means of a plug-in or directly_i1As a load, the AC electronic device canSingle-phase power supply plug and socket output end U with lightning protection function through plug-in unit_o1And (4) connecting.

The input end of general AC electronic equipment is connected with diode rectifier filter circuit, and the rectifier circuit can be used for converting AC voltage into DC voltage and outputting it so as to supply power to other electronic circuits.

The withstand voltage of the rectifier diode is usually selected to be about 1000V, and the rectified input voltage is usually AC220V/50Hz, the AC peak voltage is 311Vp, or the maximum value of the rectified and filtered output voltage is DC 311V. In normal operation, the reverse voltage experienced by the rectifier diode is equal to the superposition of the input voltage and the rectified output voltage, the highest reverse voltage is twice 311V, i.e. 622V, or the highest amplitude of the surge pulse voltage input by the rectifier diode circuit cannot exceed 689Vp, which is the highest voltage value across the capacitor C1 in fig. 15.

At ordinary times, the voltage across the capacitor C1 is a sine wave, and its maximum voltage amplitude is usually only 311Vp, and only when the high voltage pulse of the lightning surge is input, its maximum voltage amplitude may exceed 311 Vp. When differential mode surge high-voltage pulses are input into a power transmission line, the highest voltage values of two ends of a capacitor C1 are mainly determined by gas discharge tubes G1 and G3, inductors L1 and L2, piezoresistors R1 and R2 and other devices, the suppression capability on the amplitude of the surge high-voltage pulses is realized, G4, C2 and C3 mainly play a role in suppressing common mode surge high-voltage pulses, and the suppression effect on the differential mode surge high-voltage pulses is relatively small.

When a lightning surge high-voltage pulse is input, the gas discharge tubes G1, G2 and G3 need a certain time for ignition, namely, the gas is not conductive and needs to be ionized, so that the electric ions can be discharged and conducted after reaching a certain concentration, and the time for ionizing the gas is about 2-8 microseconds. Therefore, before 8 microseconds, the circuit for suppressing the high-voltage pulse of the lightning surge mainly comprises the inductors L1 and L2, the following piezoresistors R1 and R2, the gas discharge tube G4, the capacitors C1, C2 and C3 and the like.

Since the inductors L1 and L2 have distributed capacitance and the capacitor C1 also has distributed inductance, the inductors L1 and L2 and the capacitor C1 do not substantially inhibit the lightning surge high-voltage pulse or have small inhibition effect before 8 microseconds, so that the lightning surge high-voltage pulse is mainly inhibited by the piezoresistors R1 and R2 before 8 microseconds, and fig. 16 is an equivalent working principle diagram of the inductors L1 and L2 and the X capacitor C1.

Fig. 16(a) shows equivalent circuit and frequency characteristics of inductors L1, L2, in which Rs shows internal resistance (dc resistance) of the inductor, Cs shows distributed capacitance of the inductor, L shows pure inductor, Z shows impedance, F shows operating frequency, and Fc shows cutoff frequency, or resonant frequency; fig. 16(b) shows an equivalent circuit and frequency characteristics of the capacitor C1. In the figure, Ls represents the distributed inductance of the capacitor, Es_RDenotes the internal resistance of the capacitor, IR denotes the leakage resistance of the capacitor, and C denotes the pure capacitance.

Moving the distribution parameters of the inductor and the capacitor in fig. 16 to fig. 15 for analysis, it can be easily seen that, when a surge pulse with a width of 2-8 microseconds and an amplitude of tens of thousands of volts impacts the circuit in fig. 15, due to the existence of the distribution capacitor Cs in the inductor, the high-voltage pulse is directly output to the two ends of the capacitor C1 through the distribution capacitor Cs; meanwhile, because of the existence of the distributed inductance Ls in the capacitor C1, the high-voltage pulse voltage basically falls at two ends of Ls, at this time, if the piezoresistors R1 and R2 do not exist, the high-voltage pulse amplitude output at two ends of the capacitor C1 is very high, that is, the high-voltage pulse amplitude applied to the alternating current electronic equipment is very high, and the rectifier diode is easily broken down, so that the whole alternating current electronic load equipment is damaged.

How are the parameters of the electronic components selected in the circuit of fig. 15? First we say from the parameters of the piezoresistors R1, R2. According to the previous analysis, if the withstand voltage of the rectifier diode is 1000V, the maximum amplitude of the surge pulse voltage cannot exceed 689Vp, and the maximum breakdown voltage across the varistor R1 or R2 cannot exceed 344Vp, which is a voltage that is safe for extreme conditions such as a short circuit due to breakdown of one of the varistors due to the isolation of the discharge tube G4.

The discharge tube G4 is used for absorbing or suppressing the common mode surge pulse voltage, when the amplitude of the common mode surge pulse voltage exceeds the breakdown voltage of the discharge tube G4, G4 is conducted with the ground, the common mode surge pulse current is led into the ground, and the common mode surge pulse output voltage of the power plug socket is ensured not to be higher than the sum of the series voltage drops of G4 and R1 or R2. For example, when the voltage across the voltage dependent resistor R1 or R2 is 344Vp, and the breakdown voltage of the discharge tube G4 is 2700Vp, the amplitude of the common mode surge output voltage does not exceed 3044Vp, which is guaranteed by the safety standard requirements of general electronic devices.

In fig. 15, the two Y capacitors C2 and C3 mainly absorb or suppress the common mode high frequency spike voltage, and since a certain time is required for the discharge tube G4 to ignite and break down, the common mode high frequency spike voltage can be absorbed only by the two Y capacitors C2 and C3 during the ignition and break down of the discharge tube G4.

According to the requirements of national safety standard GB8898, when AC2000V/50Hz alternating voltage is applied to the ground of a power input lead wire of alternating current electronic equipment, the leakage current is less than 0.35mAp, so that the total capacity of two Y capacitors C2 and C3 connected in parallel cannot exceed 5000PF, and 2200PF can be respectively adopted in practical application.

In addition, the reason why the sum of the breakdown voltage of the discharge tube G4 and the breakdown voltage of the varistor R1 or R2 is selected to be greater than 3000Vp is also set here according to the requirements of the national safety standard GB8898, i.e., the leakage current cannot be greater than 0.35mAp when AC2000V/50Hz AC voltage is applied to the power input lead of an AC electronic device to ground.

Since the high-voltage lightning surge pulse voltage input by the power grid has both a common mode and a differential mode, in fig. 15, the three gas discharge tubes G1, G2 and G3 mainly have the function of absorbing the common-mode and differential-mode high-voltage lightning surge pulses input by the power grid. When secondary lightning surge high-voltage pulses are input into the lightning protection plug base through a power grid transmission line, 3 gas discharge tubes G1, G2 and G3 are subjected to breakdown discharge by the surge high-voltage pulses to introduce lightning surge current into the ground, so that a rear circuit is prevented from being impacted by the high-voltage lightning surge pulses.

From the safety aspect, the breakdown voltage of the gas discharge tubes G1, G3 should be greater than 1.7 times the maximum value of the mains supply input voltage, or 2.2 times the effective value, i.e. the breakdown voltage of the gas discharge tubes G1, G3 should be greater than 484V, if the voltage fluctuations of the mains are considered together plus and minus 15%, the breakdown voltage of the gas discharge tubes G1, G3 should be greater than 560V, i.e. the minimum breakdown voltage values of the two gas discharge tubes G1 and G3 are required to be greater than 280V, respectively.

The breakdown voltage of the gas discharge tube G2 must also be selected to meet the requirements of the national safety standard GB8898, i.e. when AC2000V/50Hz AC voltage is applied to the power input lead of AC electronics to ground, the leakage current is less than 0.35mAp, so that the sum of the breakdown voltages of the gas discharge tubes G2 and G1 (or G3) must not be less than 3000Vp, i.e. the breakdown voltage of G2 must be greater than 2700V.

In fig. 15, the gas discharge tube G2 may be omitted, and it is directly short-circuited to ground, but the minimum breakdown voltage of both gas discharge tubes G1 and G3 is required to be more than 3000V. Thus, the threshold of the amplitude of the differential mode surge pulse is increased, namely, the amplitude is increased from 560V to 6000V, namely, the amplitude is increased by more than 10 times, which is very disadvantageous to the following surge suppression circuit.

In addition, the piezoresistor in fig. 15 can be replaced by a TVS diode, fig. 17 is a schematic diagram of replacing the piezoresistor by a TVS diode, and D1 and D2 in the diagram are TVS diodes replacing the piezoresistor. The technical performance of the TVS diode is much better than that of the piezoresistor, because the dynamic internal resistance of the TVS diode is far smaller than that of the piezoresistor, and the service life of the TVS diode is far longer than that of the piezoresistor.

Finally we analyze the selection of inductance L1 and L2 and X capacitor C1 parameters. In fig. 15, when 3 gas discharge tubes G1, G2, and G3 have not been broken down, the amplitude of the surge pulse applied to the input terminals of inductors L1 and L2 may reach several tens of thousands of volts, while when 3 gas discharge tubes G1, G2, and G3 are broken down, the amplitude of the differential mode surge pulse applied to the input terminals of inductors L1 and L2 is 560V at the highest, and the amplitude of the common mode surge pulse is 3000V at the highest.

Therefore, in fig. 11, when we select the parameters of the inductors L1 and L2 and the X capacitor C1, the parameters of the inductors L1 and L2 and the X capacitor C1 for surge pulse suppression before the breakdown of G1, G2 and G3 is mainly considered, that is, the parameters of the inductors L1 and L2 and the X capacitor C1 are mainly considered when the surge pulse amplitude is tens of thousands of volts and the maximum pulse width is 8 microseconds.

For simplicity, we equate the circuit associated with the inductances L1 and L2 and the X capacitor C1 in fig. 15, which act as a suppressor for surge pulses, to the circuit of fig. 18(a), where L is the same as L_1-2The differential-mode inductance values of L1 and L2 are represented, and are equivalent to two equivalent differential-mode inductances of L1 and L2 which are connected in series.

Now we assume that the high voltage surge pulse is a square wave because the form factor (the ratio of the average value to the effective value) of the square wave is equal to 1, the factors of the other forms are all less than 1, and the square wave is intuitive and is particularly simple to calculate. The square wave is input from an A, B port of the circuit, is output from a C, D port after being filtered, and the amplitude of the square wave (high-voltage surge pulse) is set as U_pThe pulse width is τ and the output voltage across capacitor C1 is Uc.

Here we can see Uc as a sine wave (maximum 312V) and high voltage surge pulse through inductor L_1-2The superposition of the filtered output voltages, of course, is much less probable than 1. According to the previous analysis, the maximum value of Uc cannot be greater than 689 Vp. FIG. 18(b) shows an inductance L_1-2Voltage and current waveforms at both ends, U_LmIs an inductance L_1-2The maximum value of the voltage across it.

When a square wave is applied across the inductor, the current flowing through the inductor is a sawtooth wave with a width equal to 2 τ, i.e.:

the maximum current flowing through the inductor is:

the average current flowing through the inductor during 2 τ is:

from this, the voltage change amount of the C1 capacitor during 2 τ is determined as:

or

In the above formula, L represents the sum of the differential mode inductances L1 and L2 in FIG. 15, C represents the X capacitor C1, U represents_pFor the amplitude of the lightning surge pulse, U_cThe maximum voltage (the maximum voltage of the filtered output) across the X capacitor C1, τ is the width of the lightning surge pulse, which is the time width before the gas discharge tube is turned on in practical applications.

Or

Calculation examples: assuming the amplitude U of the lightning surge pulse_p30000V, the width tau of the lightning surge pulse is 8uS, and the maximum voltage U across the X capacitor C1_cWhen C1 is 1uF at 600V, L can be obtained from (15)_1-2Approximately equal to 3 mH.

It should be noted that, in the process of selecting or calculating the parameters of the inductances L1, L2 and the X capacitor C1, the functions of the two piezoresistors R1 and R2 in fig. 15 are not taken into consideration, and if the functions of the two piezoresistors R1 and R2 are also taken into consideration, the lightning protection effect is stronger, and the lightning protection effect is far higher than 30000V as a result of the above calculation.

In practical applications, since the inductors L1 and L2 are too high in voltage, the inductors L1 and L2 may be connected in series.

Claims

1. The utility model provides a take single-phase power plug and socket of lightning protection function which characterized in that: the single-phase power supply plug and socket with the lightning protection function comprises: (1) gas discharge tubes G1, G2, G3, G4; (2) surge pulse suppression inductors L1 and L2; (3) piezoresistors R1, R2; (4) an X safety capacitor C1; (5) y-type capacitors C2 and C3; (6) power grid input voltage socket U_i1(ii) a (7) A fuse F; (8) AC output voltage socket U_o1、U_o2、U_onN represents an arbitrary number, U_onA plurality of three-core sockets or a plurality of two-core sockets are shared;

the 2 ends of gas discharge tube G1 are connected to the 1 end of gas discharge tube G2 and the 1 end of gas discharge tube G3, respectively; terminal 2 of gas discharge tube G2 and power network input connector U_i13 end of the power grid input socket U_i1Is connected with the ground G;

2 ends of the gas discharge tube G3 are respectively connected with 2 ends of a power grid input connector Ui1 and 3 ends of surge pulse suppression inductors L2, and 2 ends of the power grid input connector Ui1 are connected with a neutral line Ni of power grid input;

the 2 terminal of the surge pulse suppression inductor L1 is connected with the 1 terminal of the voltage dependent resistor R1, the 1 terminal of the X safety capacitor C1 and the 1 terminal of the Y safety capacitor C2 respectively, and the 1 terminal of the Y safety capacitor C2 is also connected with the AC output voltage plug socket U respectively_o1、U_o2、U_onThe end 1 of the Y safety capacitor C2 is connected with the Y safety capacitorTerminal 1 of device C3, and AC output voltage socket U_o1、U_o2、U_onIs connected with the 3 end of the socket U for outputting voltage_o1、U_o2、U_onThe 3 ends of the three-way valve are respectively connected with the ground G;

AC output voltage socket U_o1、U_o2、U_onThe 1 pin (hot line Lo) and the 2 pin (cold line No) (n is an arbitrary value), and the 3 pin (ground G) are connected to the live line and the neutral line and the ground line in the subscriber plug receptacle, respectively.

2. A single-phase power plug with lightning protection function as claimed in claim 1, further characterized in that: the surge pulse suppression inductors L1 and L2 are inductance devices respectively formed by installing two inductance coils on the same iron core, the iron core adopts a structure in a shape of a Chinese character 'quan', three windows are formed, the middle window is shared by the two inductance coils L1 and L2, and the two inductance coils have the functions of suppressing differential mode surge pulse voltage and common mode surge pulse voltage.

3. A single-phase power plug with lightning protection function as claimed in claim 1, further characterized in that: the surge pulse suppression inductors L1 and L2 can be replaced by a plurality of inductors with the same specification in series connection, so that the withstand voltage and the inductance of the inductors are improved, the distributed capacitance between electrodes can be reduced, and the requirements of users on safety technology are met.

4. A single-phase power plug with lightning protection function as claimed in claim 1, further characterized in that: gas discharge tubes G1, G2, G3 may be replaced by a three-terminal gas discharge tube, with the 1 terminal of G1 corresponding to the 1 leg of the three-terminal gas discharge tube, the 2 terminal of G2 corresponding to the 2 leg (middle leg) of the three-terminal gas discharge tube, and the 2 terminal of G3 corresponding to the 3 legs of the three-terminal gas discharge tube.

5. A single-phase power plug with lightning protection function as claimed in claim 1, further characterized in that: the voltage dependent resistors R1 and R2 can be replaced by two TVS tubes D1 and D2 respectively, pins of the two TVS tubes D1 and D2 correspond to pins of the voltage dependent resistors R1 and R2 respectively, and the breakdown voltage of the TVS tubes is basically the same as that of the voltage dependent resistors, so that the technical performance of the circuit is improved, the electric leakage of the device is reduced, and the service life of the device is prolonged.

6. A single-phase power plug with lightning protection function as claimed in claim 1, further characterized in that: gas discharge tube G1, G2, G3 can also be replaced by directly designing three electrode devices with saw tooth shapes respectively on the PCB, gas gaps are reserved between every two electrodes, the 1 end of G1 corresponds to the first electrode of the three-end gas discharge tube of the PCB (connected with the 2 end of a fuse F), the 2 end of G2 corresponds to the 2 nd electrode of the three-end gas discharge tube of the PCB (connected with the ground G), and the 2 end of G3 corresponds to the 3 rd electrode of the three-end gas discharge tube of the PCB (connected with the U)_i1Ni) of 2 terminal, the breakdown voltage between the electrodes can be changed by changing the distance of each gas gap;

the gas discharge tube G4 can also be replaced by directly designing two electrode devices with saw tooth shapes on a PCB, an air gap is left between the two electrodes, one electrode corresponds to the 1 end of G4, the other electrode corresponds to the 2 end of G4, and the breakdown voltage between the two electrodes can be changed by changing the distance of the air gap.

7. A single-phase power plug with lightning protection function as claimed in claim 1, further characterized in that: single-phase power supply connector and power grid input voltage connector U with lightning protection function for one lightning stroke_i1Must be connected with the earth grid in the building structure of the user building, and the earth grid must be connected with a plurality of places of the common ground of the power transmission system, soThe grounding point ensures good connection with the ground.