AU2020289726B1

AU2020289726B1 - Insulator for preventing lightning-caused breaking and personal electric shock

Info

Publication number: AU2020289726B1
Application number: AU2020289726A
Authority: AU
Inventors: Zhen Fang; Jianping Hu; Zhenglong JIANG; Jiazheng LU; Wei Wu; Pengkang XIE
Original assignee: State Grid Corp of China SGCC; State Grid Hunan Electric Power Co Ltd; Disaster Prevention and Mitigation Center of State Grid Hunan Electric Power Co Ltd
Current assignee: State Grid Corp of China SGCC; State Grid Hunan Electric Power Co Ltd; Disaster Prevention and Mitigation Center of State Grid Hunan Electric Power Co Ltd
Priority date: 2020-05-25
Filing date: 2020-11-13
Publication date: 2021-08-05
Anticipated expiration: 2040-11-13

Abstract

Disclosed is an insulator. An epoxy resin insulated support is inside an insulation section and a lightning protection section; a plate-shaped electrode is on one side of the insulation section; a zinc oxide resistor disc is sleeved over the insulated support; one end of a spherical electrode leading-out part is connected to a spherical electrode, the other end electrically connected to the zinc oxide resistor disc; a silicone rubber umbrella cover is sleeved over the insulated support of the insulation section and the zinc oxide resistor disc; a distance from the spherical electrode to a standard straight line is dl, a distance from an edge of the plate-shaped electrode away from the standard straight line to the standard straight line is d2, a distance from an edge of an umbrella skirt away from the standard straight line to the standard straight line is d3, and dl>d2>d3.

Description

INSULATOR FOR PREVENTING LIGHTNING-CAUSED BREAKING AND PERSONAL ELECTRIC SHOCK FIELD

[0001] The present disclosure relates to the field of electric engineering technologies, more particular, to an insulator for preventing lightning-caused breaking and personal electric shock.

BACKGROUND

[0002] With the development of economy and society, the safety and reliability of power supply have been more highly demanded. More and more attention has been paid to the issue of preventing personal electric shock. At present, China's electrical safety technology is still insufficient, and prone to grid safety accidents caused by personal electric shock. According to incomplete statistics, the number of deaths caused by electric shock in China is as high as 8,000 every year, which exceeds the number of deaths caused by mining accidents worldwide every year. Personal electric shock leads to family tragedies, causing serious economic losses and adverse social impacts.

[0003] At present, insulated wires are widely used in a 10 kV distribution network to improve line insulation performance. Compared with conventional bare overhead wires, the insulated wires can increase the insulation level of lines. However, the insulated wires are more prone to lightning-caused breaking after being struck by lightning. Since a neutral point of the 10-kV distribution network is not grounded, a wire can run live for 2 hours after its single-phase broken fault and dropping to the ground. If the pedestrians touch or approach the live wire, it may cause electric shock casualties.

[0004] According to DL/T 815, IEC 6009-8 and other standards, a distribution network lightning arrester with 65-kA flow capacity is widely used in the world to prevent lightning caused breaking and personal electric shock. Due to the large amplitude of lightning current and the instantaneous power up to hundreds of megawatts, the flow capacity of existing distribution network arresters is insufficient and cannot bear the lightning energy, which leads to the frequent occurrence of lightning failure, lightning break and personal electric shock accidents of the distribution network arresters.

[0005] Based on this, it is urgent to develop lightning protection equipment to improve the security and reliability of grid supply.

SUMMARY

[0006] The present disclosure provides an insulator for preventing lightning-caused breaking and personal electric shock, which solves the problems such as lightning-caused breaking of insulated wires and personal electric shock casualty in the related arts.

[0007] The insulator for preventing lightning-caused breaking and personal electric shock provided in the present disclosure includes an insulation section and a lightning protection section arranged sequentially from top to bottom; the insulator further includes an epoxy resin insulated support, a plate-shaped electrode, a spherical electrode, a spherical electrode leading out part, a zinc oxide resistor disc, and a silicone rubber umbrella cover;

[0008] the epoxy resin insulated support is located inside the insulation section and the lightning protection section and makes the insulation section and the lightning protection section fixed as a whole; the plate-shaped electrode is located on one side of the insulation section away from the lightning protection section; at the lightning protection section, the zinc oxide resistor disc is sleeved over the epoxy resin insulated support; one end of the spherical electrode leading out part is electrically connected to the spherical electrode, and the other end is electrically connected to the zinc oxide resistor disc; the spherical electrode and the plate-shaped electrode are arranged at intervals; the silicone rubber umbrella cover is sleeved over an outer surface of the epoxy resin insulated support of the insulation section and an outer surface of the zinc oxide resistor disc of the lightning protection section; and the silicone rubber umbrella cover is provided with a plurality of umbrella skirts; and

[0009] a straight line where a symmetry axis of the epoxy resin insulated support is located is taken as a standard straight line, a distance from the spherical electrode to the standard straight line is a first distance dl, a distance from an edge of the plate-shaped electrode away from the standard straight line to the standard straight line is a second distance d2, a distance from an edge of the umbrella skirt away from the standard straight line to the standard straight line is a third distance d3, and dl>d2>d3.

[0010] Further, in the insulator, an end portion of the lightning protection section away from the insulation section is installed on a tower cross arm through a screw hole, and an end portion of the insulation section away from the lightning protection section is provided with a wiring groove for placing an insulated wire.

[0011] Further, a diameter of the spherical electrode ranges from 5 cmto 7 cm.

[0012] Further, a distance from any point of the plate-shaped electrode to the spherical electrode is a fourth distance; and when the fourth distance takes a minimum value, a point corresponding to the fourth distance is a standard point;

[0013] a plane perpendicular to a symmetry axis of the epoxy resin insulated support is taken as a first plane, and an angle between a connection line of the standard point on the plate-shaped electrode and the spherical electrode and the first plane ranges from 30 to 45; and

[0014] a size of a gap between the spherical electrode and the plate-shaped electrode ranges from 40 cm to 60 cm.

[0015] Further, the silicone rubber umbrella cover is provided with a plurality of umbrella skirts; and the plurality of umbrella skirts are classified into two categories, which are a first type of umbrella skirts and a second type of umbrella skirts respectively; and

[0016] the first type of umbrella skirts and the second type of umbrella skirts are arranged at intervals along an extension direction of a symmetry axis of the epoxy resin insulated support, and an umbrella diameter of the first type of umbrella skirts is greater than that of the second type of umbrella skirts.

[0017] Further, in the insulator, both a creepage distance of the insulation section and a creepage distance of the lightning protection section are greater than or equal to 350 mm.

[0018] Further, in the insulator, a method for selecting the zinc oxide resistor disc includes the following steps:

[0019] calculating lightning energy tolerance and flow capacity required on the zinc oxide resistor disc in the insulator; and

[0020] selecting the zinc oxide resistor disc according to the lightning energy tolerance and the flow capacity required on the zinc oxide resistor disc.

[0021] Further, the calculating lightning energy tolerance and flow capacity required on the zinc oxide resistor disc in the insulator includes the following steps:

[0022] obtaining lightning activity distribution characteristics of a target area and expected lightning protection effect parameters, and determining a lightning resistance level Ix of a target line based on the lightning activity distribution characteristics of the target area and the expected lightning protection effect parameters;

[0023] establishing an electromagnetic transient simulation model to calculate a lightning current and overvoltage of a distribution network line when lightning current amplitude is Ix; and

[0024] calculating the lightning energy tolerance and the flow capacity of the zinc oxide resistor disc in the insulator according to the lightning current and overvoltage of the distribution network line.

[0025] Further, the lightning activity distribution characteristics include lightning current amplitude probability distribution of the target line;

[0026] the expected lightning protection effect parameters include a target lightning trip-out rate of a designated power transmission line; and

[0027] the determining a lightning resistance level Ix of a target line based on the lightning activity distribution characteristics of the target area and the expected lightning protection effect parameters includes:

[0028] determining the lightning resistance level Ix of the target line based on the lightning current amplitude probability distribution of the target line and the target lightning trip-out rate of the designated power transmission line.

[0029] Further, the calculating the lightning energy tolerance and the flow capacity of the zinc oxide resistor disc in the insulator according to the lightning current and overvoltage of the distribution network line includes:

[0030] calculating the lightning energy tolerance E of the zinc oxide resistor disc in the insulator according to the following formula:

T

EO= f i(t) - [eai(t)b + c]dt 0

[0031] calculating the flow capacity io(t) of the zinc oxide resistor disc in the insulator according to the following formula:

T

fi0 [eaio(t)+b + c] dt = EO 0

[0032] where t is time; T is lightning action time; EO is energy absorbed by the zinc oxide resistor disc in the insulator, i.e. the lightning energy tolerance; i(t) is a lightning current waveform at both ends of the insulator after an lightning current with the amplitude Ix strikes on s the wire, obtained by electromagnetic transient simulation; io(t) is a lightning current waveform

of 4/10 ps, and the amplitude of io(t) is the flow capacity of the zinc oxide resistor disc; a, b, and

c are constants; ande ai(t)+b ande aiO (t)+b are residual voltages at both ends of the zinc oxide resistor disc when a lightning current and a large impulse current flow through the insulator, respectively.

[0033] In the insulator for preventing lightning-caused breaking and personal electric shock proposed in the present disclosure, the epoxy resin insulated support is located inside the insulation section and the lightning protection section and makes the insulation section and the lightning protection section fixed as a whole; the plate-shaped electrode is located on one side of the insulation section away from the lightning protection section; at the lightning protection section, the zinc oxide resistor disc is sleeved over the epoxy resin insulated support; one end of the spherical electrode leading-out part is electrically connected to the spherical electrode, and the other end is electrically connected to the zinc oxide resistor disc; the spherical electrode and the plate-shaped electrode are arranged at intervals; the silicone rubber umbrella cover is sleeved over an outer surface of the epoxy resin insulated support of the insulation section and an outer surface of the zinc oxide resistor disc of the lightning protection section; and the silicone rubber umbrella cover is provided with a plurality of umbrella skirts; and a straight line where a symmetry axis of the epoxy resin insulated support is located is taken as a standard straight line, a distance from the spherical electrode to the standard straight line is a first distance dl, a distance from an edge of the plate-shaped electrode away from the standard straight line to the standard straight line is a second distance d2, a distance from an edge of the umbrella skirt away from the standard straight line to the standard straight line is a third distance d3, and dl>d2>d3. When lightning strikes, an electrode gap breaks down, and the lightning current flows through a tower cross arm along the electrode gap and a zinc oxide resistor and finally enters the earth. After the lightning strike, the zinc oxide resistor disc recovers a high-impedance state, limits the amplitude of the power-flow current voltage, and finally extinguishes the power-flow current arc, which can prevent occurrence of lightning-caused breaking and personal electric shock accidents.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a time-varying curve of temperatures at the position of a lightning breakdown point of an insulated wire according to an embodiment of the present disclosure.

[0035] Figure 2 is a schematic structural diagram of an insulator for preventing lightning caused breaking and personal electric shock according to an embodiment of the present disclosure.

[0036] Figure 3 is an experimental device diagram for the experimental study on influences of a diameter of a spherical electrode in the insulator as provided in Figure 2 on impact discharge characteristics by simulating pollution, icing, rainfall, and other conditions;

[0037] Figure 4 is a flowchart of a method for calculating energy tolerance and flow capacity of a zinc oxide resistor disc in the insulator for preventing lightning-caused breaking and personal electric shock according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0038] Specific implementations of the present disclosure are described below in further detail with reference to the accompanying drawings and the description of embodiments, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the invention concept and technical solutions of the present disclosure.

[0039] Before the detailed introduction of this solution, the mechanism of lightning-caused breaking is expounded. Lightning strike easily leads to breakdown of insulated wires, and a power-flow current arc focuses on one point and bums, which leads to local melting and breaking. When lightning breaks through an insulated wire and generates a power-flow current arc, the heat generated by the arc and the heat absorbed by the wire can be expressed as the following formula (1)

10Ji1 (t)rdt =CmolSAT 0 (1)

[0040] In the formula (1), ii(t) is an arc current function, r is equivalent resistance of a wire heating part, to is current action time, C is specific heat capacity of the wire, mo is the density of

the wire, I is the length of the wire heating part, S is a cross-sectional area of the wire, and AT is

a variation in temperature rise of the wire.

[0041] In an example, if an aluminum wire is used as an insulated wire in a 10-kV distribution network, the density mo=2700 kg/m 3. The specific heat capacity of aluminum is C=0.88x103 J/(kg-°C), and the melting point is 660.37C. It is set that the length of the wire heating part 1=0.Im, the cross-sectional area of the wire S=50 mm2,2 and the equivalent resistance of the wire

heating part r--15 mQ. Lightning strike leads to breakdown of the insulated wire and generation

of a power-flow current arc. For single-phase breakdown grounding of the insulated wire caused by lightning strike, the insulated wire is applied to the 10-kV distribution network, and the natural ground resistance of the tower is up to thousands of ohms; therefore, the power current amplitude of the single-phase ground short circuit is 10 A. Based on the formula (1), the time varying curve of temperatures at the position of a wire breakdown point can be obtained, as shown in Figure 1. It can be seen from Figure 1 that with the increase of time, the temperature of the wire keeps rising and reaches the melting point of aluminum at about 1000s, and the wire starts to melt and finally fuses under tension of the wire. After the wire fuses and drops to the ground, the wire can run live after dropping to the ground because the neutral point of the distribution network is not grounded, and when a person contacts or gets close to the live wire, it may cause electric shock casualties.

[0042] Therefore, in order to put an end to lightning-caused breaking accidents and then prevent personal injury caused by electric shock, an insulator for preventing lightning-caused breaking and personal electric shock needs to be used to support the wire and extinguish a power-flow current arc to prevent the flow current arc from burning continuously at one point and leading to the breaking of the insulated wire and cause personal electric shock casualties.

[0043] Figure 2 is a schematic structural diagram of an insulator for preventing lightning caused breaking and personal electric shock according to an embodiment of the present disclosure. The insulator includes an insulation section M and a lightning protection section N arranged sequentially from top to bottom. The insulator further includes an epoxy resin insulated support 1, a plate-shaped electrode 2, a spherical electrode 3, a spherical electrode leading-out part 4, a zinc oxide resistor disc 5, and a silicone rubber umbrella cover 6. The epoxy resin insulated support 1 is located inside the insulation section M and the lightning protection section N and makes the insulation section M and the lightning protection section N fixed as a whole. The plate-shaped electrode 2 is located on one side of the insulation section M away from the lightning protection section N. At the lightning protection section N, the zinc oxide resistor disc is sleeved over the epoxy resin insulated support 1. One end of the spherical electrode leading out part 4 is electrically connected to the spherical electrode 3, and the other end is electrically connected to the zinc oxide resistor disc 5. The spherical electrode 3 and the plate-shaped electrode 2 are arranged at intervals, that is, an electrode gap (in practice, the electrode gap may be filled with air, which may also be referred to as an air gap) is formed between the spherical electrode 3 and the plate-shaped electrode 2. The silicone rubber umbrella cover 6 is sleeved over an outer surface of the epoxy resin insulated support 1 of the insulation section M and an outer surface of the zinc oxide resistor disc 5 of the lightning protection section N. The silicone rubber umbrella cover 6 is provided with a plurality of umbrella skirts. A straight line where a symmetry axis of the epoxy resin insulated support 1 is located is taken as a standard straight line, a distance from the spherical electrode 3 to the standard straight line is a first distance dl, a distance from an edge of the plate-shaped electrode 2 away from the standard straight line to the standard straight line is a second distance d2, a distance from an edge of the umbrella skirt away from the standard straight line to the standard straight line is a third distance d3, and d>d2>d3.

[0044] In use, a lower end of the insulator (i.e. an end portion of the lightning protection section N away from the insulation section M) is installed on a tower cross arm through a screw hole, and an upper end of the insulator (i.e. an end portion of the insulation section M away from the lightning protection section N) is provided with a wiring groove 9 for placing an insulated wire. The epoxy resin insulated support 1 and the plate-shaped electrode 2 jointly support the insulated wire in the wiring groove 9 of the insulator.

[0045] Under normal working conditions, the insulated wire and the electrode gap bear the line operating voltage. When lightning strikes, an electrode gap breaks down, as shown by the dotted line arrows in Figure 2, and the lightning current flows through a tower cross arm along the electrode gap and a zinc oxide resistor 5 and finally enters the earth. After the lightning strike, the zinc oxide resistor disc 5 recovers a high-impedance state, limits the amplitude of the power- flow current voltage, and finally extinguishes the power-flow current arc, which can prevent occurrence of lightning-caused breaking and personal electric shock accidents.

[0046] Optionally, the spherical electrode 3 and the plate-shaped electrode 2 are both made of a metallic material.

[0047] In actual setting, it may be set according to a requirement that at the lightning protection section N, a plurality of zinc oxide resistor discs 5 are sleeved over the epoxy resin insulated support 1 (for example, a total of 4 zinc oxide resistor discs 5 are sleeved). The plurality of zinc oxide resistor discs 5 are sequentially arranged along an extension direction from the insulation section to the lightning protection section.

[0048] In this case, during implementation of "one end of the spherical electrode leading-out part 4 is electrically connected to the spherical electrode 3, and the other end is electrically connected to the zinc oxide resistor disc 5", optionally, still referring to Figure 2, one side of the zinc oxide resistor disc 5 closest to the insulation section M near the insulation section M is provided with a metal member 7. The metal member 7 is electrically connected to the zinc oxide resistor disc 5 closest to the insulation section M. One end of the spherical electrode leading-out part 4 is fixed and electrically connected to the spherical electrode 3, and the other end is fixed and electrically connected to the metal member 7. As the metal member 7 is electrically connected to the zinc oxide resistor disc 5 closest to the insulation section M, the spherical electrode leading-out part 4 is finally electrically connected to the zinc oxide resistor disc 5 closest to the insulation section M. The spherical electrode leading-out part 4 is made of a conductive material (such as metal).

[0049] Research shows that for the electrode gap, the higher the non-uniformity of a space electric field, the more stable the discharge. In the above solution, the setting of the spherical electrode 3 and the plate-shaped electrode 2 is conducive to improving the non-uniformity of the space electric field, which can improve the stability of discharge.

[0050] It should be noted that although the plate-shaped electrode 2 is referred to as plate shaped electrode in the present application, in actual setting, the plate-shaped electrode 2 may be set as a flat plate, or a part of a sphere, or a disk. This is not limited in the present application.

[0051] In consideration of possible influences of pollution, icing, rainfall, and other conditions on discharge characteristics, Figure 3 is an experimental device diagram for the experimental study on influences of a diameter of a spherical electrode in the insulator as provided in Figure 2 on impact discharge characteristics by simulating pollution, icing, rainfall, and other conditions. The results show that when the diameter of the spherical electrode is less than or equal to 7 cm, the breakdown voltage difference of multi-impact discharge is the smallest and the discharge voltage is the most stable. At the same time, the smaller the diameter of the spherical electrode, the more likely the corona phenomenon will occur under icing, rainfall, pollution, and other conditions, which affects the service life of the silicone rubber umbrella cover 6. Based on the above factors, the diameter of the spherical electrode is optionally set to a range of 5 cm to 7cm.

[0052] Due to the fact that bridging by icing or rainstorm easily occurs between the umbrella skirts and the electrode (such as the spherical electrode or plate-shaped electrode), between the spherical electrode and the plate-shaped electrode, and between the skirts in the insulator for preventing lightning-caused breaking and personal electric shock, an external insulation flashover accident under the action of power frequency voltage may occur. Moreover, due to the randomness of lightning discharge, lightning tends to develop along the outer surface of the insulator under pollution conditions without passing through the zinc oxide resistor, leading to lightning tripping power failure and electric shock accidents. In view of this, in the above technical solution, it is set that dl>d2>d3, with the purpose of making the umbrella skirts, the spherical electrode, and the plate-shaped electrode staggered from each other at a safe distance, so as to reduce the probability that the umbrella skirts and the electrode (such as the spherical electrode or plate-shaped electrode), the spherical electrode and the plate-shaped electrode, and the skirts are bridged due to icing or rainstorm, reduce the probability of external insulation flashover accidents, and then reduce the probability of lightning tripping power failure and electric shock accidents.

[0053] Further, still referring to Figure 2, the plate-shaped electrode 2 is regarded as a set of points, and a distance from any point on the plate-shaped electrode 2 to the spherical electrode 3 is a fourth distance. When the fourth distance takes a minimum value, a point corresponding to the fourth distance is a standard point A. A plane perpendicular to a symmetry axis of the epoxy resin insulated support 1 is taken as a first plane. Optionally, an angle between a connection line of the standard point A on the plate-shaped electrode 2 and the spherical electrode 3 and the first plane ranges from 300to 45°. The size of the electrode gap (i.e. the length of the connection line of the standard point A and the spherical electrode 3) ranges from 40 cm to 60 cm. In this way, the spherical electrode 3 and the plate-shaped electrode 2 are further staggered from each other at a safe distance, thereby preventing bridging of the electrode gap by rainstorm or icing and preventing flashover accidents under the action of power frequency voltage. At the same time, under the action of lightning impulse voltage, the electric field intensity between the plate shaped electrode 2 and the spherical electrode 3 is the largest, and a discharge arc preferentially develops along an air gap between the plate-shaped electrode 2 and the spherical electrode 3. The lightning current flows through the zinc oxide resistor 5 to ensure reliable arc extinguishing of the power-flow current.

[0054] Optionally, still referring to Figure 2, the silicone rubber umbrella cover 6 is provided with a plurality of umbrella skirts. The plurality of umbrella skirts are classified into two categories, which are a first type of umbrella skirts 61 and a second type of umbrella skirts 62 respectively. The first type of umbrella skirts 61 and the second type of umbrella skirts 62 are arranged at intervals along an extension direction of a symmetry axis of the epoxy resin insulated support 1, and an umbrella diameter of the first type of umbrella skirts 61 is greater than that of the second type of umbrella skirts 62. The setting is intended to prevent bridging of adjacent umbrella skirts by rainstorm or icing, and to prevent flashover accidents under the action of power frequency voltage. In this case, "a distance from an edge of the plate-shaped electrode 2 away from the standard straight line to the standard straight line is a second distance d2, a distance from an edge of the umbrella skirt away from the standard straight line to the standard straight line is a third distance d3, and d2>d3" hereinabove should be understood as that the umbrella diameter of the two categories of umbrella skirts is less than the diameter of the plate shaped electrode.

[0055] Based on the above technical solutions, in order to ensure that lightning does not flashover along the surface of the insulator under severe pollution conditions, an umbrella skirt distance shall ensure that the lightning discharge does not creep along the umbrella skirt, that is, it needs to ensure that a distance between the insulation section and the lightning protection section of the insulator is greater than or equal to 350 mm. The creepage distance of the insulation section of the insulator refers to the shortest path measured along an outer surface of the insulation section from an end portion of the insulation section away from the lightning protection section to an end portion of the insulation section connected to the lightning protection section. In Figure 2, the length of the dotted line Q is the creepage distance of the insulation section of the insulator. Similarly, the creepage distance of the lightning protection section of the insulator is the shortest path measured along an outer surface of the lightning protection section from an end portion of the lightning protection section connected to the insulation section to an end portion of the lightning protection section away from the insulation section. In Figure 2, the length of the dotted line Z is the creepage distance of the lightning protection section of the insulator. It needs to ensure that the insulator for preventing lightning caused breaking and personal electric shock does not discharge under the action of power frequency overvoltage and that the lightning breakdown discharge voltage is no more than 100 k. Test results show that by setting both the creepage distances of the insulation section and the lightning protection section of the insulator to be greater than or equal to 350 mm, the insulation strength of the insulated wire under the action of power frequency and impulse voltage can be enhanced by 30 to 40 k, compared with that of the bare wire.

[0056] The lightning protection effect of the insulator for preventing lightning-caused breaking and personal electric shock shown in Figure 2 depends on the energy tolerance and flow capacity of the zinc oxide resistor disc therein. Therefore, in order to ensure that the insulator for preventing lightning-caused breaking and personal electric shock shown in Figure 2 conforms to technical requirements of lightning protection, energy tolerance and flow capacity required on a zinc oxide resistor disc in the insulator need to be calculated first, and then a zinc oxide resistor disc with appropriate electrical performance parameters is selected according to the energy tolerance and the flow capacity required on the zinc oxide resistor disc.

[0057] Figure 4 is a flowchart of a method for calculating energy tolerance and flow capacity of a zinc oxide resistor disc in the insulator for preventing lightning-caused breaking and personal electric shock according to an embodiment of the present disclosure. Referring to Figure 4, the method for calculating energy tolerance and flow capacity of a zinc oxide resistor disc in the insulator for preventing lightning-caused breaking and personal electric shock includes mainly the following steps:

[0058] Si. Obtain lightning activity distribution characteristics of a target area and expected lightning protection effect parameters, and determine a lightning resistance level Ix of a target line based on the lightning activity distribution characteristics of the target area and the expected lightning protection effect parameters.

[0059] Optionally, the lightning activity distribution characteristics include lightning current amplitude probability distribution P(I) of the target line. If the lightning current amplitude at each lightning strike of a target transmission line is regarded as a data point, the lightning current amplitude probability distribution P(I) is a set of multiple data points. Therefore, the lightning current amplitude probability distribution P(I) of the target line may be regarded as a set of lightning current amplitude I at each lightning strike of the target line.

[0060] The expected lightning protection effect parameters include a target lightning trip-out

rate r (unit: times/100 km.a) of a designated power transmission line. The target lightning trip

out rate r (unit: times/100 km.a) of the designated power transmission line is determined

according to a desired lightning protection effect.

[0061] The lightning resistance level Ix of the target line means that when the lightning current amplitude is higher than Ix, the lightning current exceeds the lightning protection range of the insulator, and the insulator loses the function of lightning protection. If n is the number of lightning strikes per year on a 100-km long transmission line, how many lightning currents are allowed to exceed the lightning protection range of the insulator under the desired lightning

protection effect can be obtained by using r/n. Based on the lightning current amplitude probability distribution P(I), in determination of the value of Ix, the total number of lightning strikes with the lightning current amplitude greater than Ix is approximately equal to r/n. In this case, the value of Ix is the lightning resistance level Ix of the target line.

[0062] There are many methods to determine the number n of lightning strikes per year on the

100-km long transmission line. For example, if the flash density a (unit: times/km2 .a) along the

line and the lightning width Y (unit: m) of the tower are known, n can be calculated according to

n=axY/10.

[0063] S2. Establish an electromagnetic transient simulation model to calculate a lightning current and overvoltage of a distribution network line when lightning current amplitude is Ix.

[0064] The electromagnetic transient simulation model is established in PSCAD software.

Optionally, surge impedance of the line is set to 300 Q. The tower cross arm is a metal structure,

and the inductance of the tower is 0.1 uH/m. The ground resistance is natural grounding, which

is 3000 Q. A current source with lightning current amplitude of Ix and a waveform of 2.6/50 s

is injected into the power transmission line, and the lightning current and overvoltage at various locations of the distribution network line can be simulated and calculated according to a PSCAD transient simulation model.

[0065] S3. Calculate the lightning energy tolerance and the flow capacity of the zinc oxide resistor disc in the insulator according to the lightning current and overvoltage of the distribution network line.

[0066] The lightning energy tolerance E of the zinc oxide resistor disc in the insulator for preventing lightning-caused breaking and personal electric shock is calculated according to formula (2):

T

EO = f i(t) - Leai( t) b+ e]dt 0 (2)

[0067] The flow capacity io(t) of the insulator for preventing lightning-caused breaking and personal electric shock is calculated according to formula (3):

T

fi 0 (t)[e aio(t)+b + c] dt = EO 0 (3)

[0068] In the formulas (2) and (3), t is time; T is lightning action time; E is energy absorbed by the zinc oxide resistor disc in the insulator for preventing lightning-caused breaking and personal electric shock, i.e. the lightning energy tolerance; i(t) is a lightning current waveform at both ends of the insulator for preventing lightning-caused breaking and personal electric shock after an lightning current with the amplitude Ix strikes on s the wire, obtained by electromagnetic transient simulation; io(t) is a lightning current waveform of 4/10 ps, and the amplitude of io(t) is the flow capacity of the zinc oxide resistor disc; a, b, and c are constants; ande ai(t)+b and eaio(t)+b are residual voltages at both ends of the zinc oxide resistor disc when a lightning current and a large impulse current flow through the insulator for preventing lightning-caused breaking and personal electric shock, respectively.

[0069] It should be noted that in the prior art, a residual voltage calculation formula is nonlinear, and a discrete formula is generally used for residual voltage calculation, which makes the calculation method complicated. Since the resistor disc works mainly in a large current section under the action of lightning current, in the present application, characteristics of residual

voltage in the large current section are fitted in the formulas (2) and (3) to obtained ai(t)+b and

aio(t)+b, so that the calculation is more convenient. Since the energy tolerance and the flow capacity of the zinc oxide resistor disc in the insulator for preventing lightning-caused breaking and personal electric shock can be calculated according to the formulas (2) and (3), an insulator for preventing lightning-caused breaking and personal electric shock conforming to technical requirements of lightning protection can be obtained by selecting an appropriate zinc oxide resistor disc.

[0070] In the above technical solutions, in order to ensure that the lightning current does not damage the zinc oxide resistor disc, a method for selecting flow capacity parameters is designed by statistics on lightning current amplitude distribution characteristics to obtain electrical performance parameters of the conforming zinc oxide resistor. For the tower modified by natural grounding, when the flow capacity of the impact current of 4/10 s is more than 100 kA, the lightning energy tolerance is 60 kJ, which can reduce the lightning trip-out rate to below 0.06 times /100 km. a, effectively avoiding personal electric shock accidents due to lightning-caused breaking.

[0071] The present disclosure analyzes that the mechanism of lightning-caused breaking lies in that a lightning strike easily causes breakdown of an insulated wire, and a power-flow current arc focuses on one point and bums, which leads to local melting and breaking. The use of the insulator for preventing lightning-caused breaking and personal electric shock provided in the embodiments of the present disclosure can extinguish the power-flow current arc and prevent the continuous burning of the arc at one point that may lead to the breaking of the insulated wire and cause personal electric shock casualties.

[0072] In order to ensure that the lightning current does not damage the zinc oxide resistor disc, the present disclosure conducts statistics on lightning amplitude distribution characteristics and designs a method for selecting flow capacity parameters, which can reduce the lightning trip-out rate to below 0.06 times /100 km. a, avoiding lightning-caused breaking and personal electric shock accidents.

[0073] In order to ensure that the lightning current passes through the zinc oxide resistor, the present disclosure further designs an insulator for preventing lightning-caused breaking and personal electric shock to ensure that lightning discharge breaks through along a metal electrode and passes through a zinc oxide resistor disc. The insulator for preventing lightning-caused breaking and personal electric shock is composed of an insulation section and a lightning protection section. An epoxy resin insulated support runs entirely through the insulation section and the lightning protection section to support the weight of the wire. The zinc oxide resistor disc is installed in the lightning protection section for discharging lightning energy. The plate-shaped electrode and the spherical electrode form a staggered electrode structure, which can effectively control a lightning discharge path, ensure breakdown discharge of air gap between the electrodes, and make the lightning flow through the zinc oxide resistor disc.

[0074] The above are only preferred embodiments of the present disclosure. The protection scope of the present disclosure is not limited to the above embodiments. Any technical solutions belonging to the thought of the present disclosure belong to the protection scope of the present disclosure. It should be noted that one having the ordinary skill in the art can make improvements and modifications without departing from the principle of the present disclosure. These improvements and modifications should also come within the protection scope of the present disclosure.

Claims

CLAIMS: 1. An insulator for preventing lightning-caused breaking and personal electric shock, wherein the insulator comprises an insulation section and a lightning protection section arranged sequentially from top to bottom; the insulator further comprises an epoxy resin insulated support, a plate-shaped electrode, a spherical electrode, a spherical electrode leading-out part, a zinc oxide resistor disc, and a silicone rubber umbrella cover; the epoxy resin insulated support is located inside the insulation section and the lightning protection section and makes the insulation section and the lightning protection section fixed as a whole; the plate-shaped electrode is located on one side of the insulation section away from the lightning protection section; at the lightning protection section, the zinc oxide resistor disc is sleeved over the epoxy resin insulated support; one end of the spherical electrode leading-out part is electrically connected to the spherical electrode, and the other end of the spherical electrode is electrically connected to the zinc oxide resistor disc; the spherical electrode and the plate-shaped electrode are arranged at intervals; the silicone rubber umbrella cover is sleeved over an outer surface of the epoxy resin insulated support of the insulation section and an outer surface of the zinc oxide resistor disc of the lightning protection section; and the silicone rubber umbrella cover is provided with a plurality of umbrella skirts; and a straight line where a symmetry axis of the epoxy resin insulated support is located is taken as a standard straight line, a distance from the spherical electrode to the standard straight line is a first distance dl, a distance from an edge of the plate-shaped electrode away from the standard straight line to the standard straight line is a second distance d2, a distance from an edge of the umbrella skirt away from the standard straight line to the standard straight line is a third distance d3, and dl>d2>d3.
2. The insulator according to claim 1, wherein in the insulator, an end portion of the lightning protection section away from the insulation section is installed on a tower cross arm through a screw hole, and an end portion of the insulation section away from the lightning protection section is provided with a wiring groove for placing an insulated wire.
3. The insulator according to claim 1, wherein a diameter of the spherical electrode ranges from 5 cm to 7 cm.
4. The insulator according to claim 1, wherein a distance from any point of the plate-shaped electrode to the spherical electrode is a fourth distance; and when the fourth distance takes a minimum value, a point corresponding to the fourth distance is a standard point; a plane perpendicular to the symmetry axis of the epoxy resin insulated support is taken as a first plane, and an angle between a connection line of the standard point on the plate-shaped electrode and the spherical electrode and the first plane ranges from 30 to 45; and a size of a gap between the spherical electrode and the plate-shaped electrode ranges from cm to 60 cm.
5. The insulator according to claim 1, wherein the silicone rubber umbrella cover is provided with a plurality of umbrella skirts; and the plurality of umbrella skirts are classified into two types, which are a first type of umbrella skirts and a second type of umbrella skirts respectively; and the first type of umbrella skirts and the second type of umbrella skirts are arranged at intervals along an extension direction of the symmetry axis of the epoxy resin insulated support, and an umbrella diameter of the first type of umbrella skirts is greater than that of the second type of umbrella skirts.
6. The insulator according to claim 1, wherein in the insulator, both a creepage distance of the insulation section and a creepage distance of the lightning protection section are greater than or equal to 350 mm.
7. The insulator according to claim 1, wherein in the insulator, a method for selecting the zinc oxide resistor disc comprises the following steps: calculating lightning energy tolerance and flow capacity required on the zinc oxide resistor disc in the insulator; and selecting the zinc oxide resistor disc according to the lightning energy tolerance and the flow capacity required on the zinc oxide resistor disc.
8. The insulator according to claim 7, wherein the calculating lightning energy tolerance and flow capacity required on the zinc oxide resistor disc in the insulator comprises the following steps: obtaining lightning activity distribution characteristics of a target area and expected lightning protection effect parameters, and determining a lightning resistance level Ix of a target line based on the lightning activity distribution characteristics of the target area and the expected lightning protection effect parameters; establishing an electromagnetic transient simulation model to calculate a lightning current and overvoltage of a distribution network line when lightning current amplitude is Ix; and calculating the lightning energy tolerance and the flow capacity of the zinc oxide resistor disc in the insulator according to the lightning current and overvoltage of the distribution network line.
9. The insulator according to claim 8, wherein: the lightning activity distribution characteristics comprise lightning current amplitude probability distribution of the target line; the expected lightning protection effect parameters comprise a target lightning trip-out rate of a designated power transmission line; and the determining a lightning resistance level Ix of a target line based on the lightning activity distribution characteristics of the target area and the expected lightning protection effect parameters comprises: determining the lightning resistance level Ix of the target line based on the lightning current amplitude probability distribution of the target line and the target lightning trip-out rate of the designated power transmission line.
10. The insulator according to claim 8, wherein the calculating the lightning energy tolerance and the flow capacity of the zinc oxide resistor disc in the insulator according to the lightning current and overvoltage of the distribution network line comprises: calculating the lightning energy tolerance E of the zinc oxide resistor disc in the insulator according to the following formula:

T

EO= f e ai+ b + c]dt 0 calculating the flow capacity io(t) of the zinc oxide resistor disc in the insulator according to the following formula:

T

Ji0 [eaio(t)+b + c]dt = EO 0 where t is time; T is lightning action time; EO is energy absorbed by the zinc oxide resistor disc in the insulator, i.e. the lightning energy tolerance; i(t) is a lightning current waveform at both ends of the insulator after an lightning current with the amplitude Ix strikes on the wire,

obtained by electromagnetic transient simulation; io(t) is a lightning current waveform of 4/10 ps,

and an amplitude of io(t) is the flow capacity of the zinc oxide resistor disc; a, b, and c are constants; ande ai(t)+b ande aiO(t)+b are residual voltages at both ends of the zinc oxide resistor disc when a lightning current and a large impulse current flow through the insulator, respectively.