A Y-type double-gap lightning protection device for overhead transmission lines

Abstract

The invention discloses a Y-type double-gap lightning protection device for an overhead power transmission line, comprising: a voltage limiter, an original insulator string and a newly added insulator string; an electrode at the bottom end of the voltage limiter is connected to a top steel cap of the newly added insulator string through an electric conductor, the newly added insulator string is connected to an end steel foot of the original insulator string, and a discharge electrode is provided at the end of the newly added insulator string; a gap of the newly added insulator string is formed between the top steel cap of the newly added insulator string and the discharge electrode; the discharge electrode in the scheme adopts a double-gap structure design, an air gap and a parallel insulator string gap form an integrated parallel double-gap structure, the air gap distance can be accurately controlled after the insulator string gap is determined according to the voltage level, when there is a lightning overvoltage in the transmission line conductor, the double-gap structure ensures discharge along one of the gaps, the double gaps form a double insurance function, and avoid the situation where the overvoltage does not pass through the voltage limiter due to the dispersion of the gap discharge.

Description

Technical Field

[0001] The invention belongs to the field of lightning protection for power transmission lines, and in particular relates to a Y-type double-gap lightning protection device for overhead power transmission lines. Background Art

[0002] Lightning strikes are the main cause of tripping of overhead transmission lines. Frequent tripping of transmission lines will affect the safe and stable operation of the power grid. Operation experience shows that installing line arresters in line sections with strong lightning activity or high soil resistivity and difficulty in reducing grounding resistance is an effective way to reduce the lightning tripping rate. Line arresters can greatly improve the lightning resistance level of transmission lines and reduce the lightning flashover rate of transmission lines.

[0003] At present, line arresters are mainly of two types: with series gap and without series gap. Compared with arresters without gap, arresters with series gaps install series gaps so that the arrester body does not directly bear the power frequency voltage, and the aging rate of the valve plate is greatly reduced compared with arresters without gaps. At the same time, the arrester body is not affected by the operating overvoltage, the body reference voltage is low, and the arrester body can be designed with small volume and light weight. Existing series gaps mainly use gaps with supports or air gaps. The total length of the series gap support and the arrester body of the line arrester with support gap is generally greater than the line insulator, which is difficult to install and requires accurate insulation matching calculation; the series gap support is a synthetic insulator with a short structural height, and its service life is affected by the electric field strength and gap arcing during operation. The gap distance of the air gap line arrester changes under the action of strong winds, causing the lightning overvoltage breakdown voltage to change, affecting the insulation matching between the line arrester and the insulator, and may cause the arrester to fail. Summary of the invention

[0004] The purpose of the present invention is to provide a Y-type double-gap lightning protection device for overhead power transmission lines to address the problems that the gap distance of existing line lightning arresters with series gaps is difficult to accurately control, the service life of the series support gaps of synthetic materials is short, and the air gap spacing is affected by strong winds. The device adopts a double-gap structure, which can realize convenient and efficient installation of line lightning arresters, accurately control the gap distance, improve the installation stability of the line lightning arrester, and prolong its service life.

[0005] The technical solution provided by the present invention is as follows:

[0006] A Y-type double-gap lightning protection device for an overhead power transmission line comprises: a voltage limiter, an original insulator string and a newly added insulator string; an electrode at the bottom end of the voltage limiter is connected to a top steel cap of the newly added insulator string through an electric conductor, the newly added insulator string is connected to the end steel leg of the original insulator string, and a discharge electrode is provided at the end of the newly added insulator string; a gap of the newly added insulator string is formed between the top steel cap of the newly added insulator string and the discharge electrode;

[0007] The length of the air gap formed by the end of the discharge electrode and the bottom of the voltage limiter is L, the length of the newly added insulator string gap hardware string is L0, and L≤(0.963+3.89*L0) / (2.996-L0).

[0008] The Y-type double-gap lightning protection device of the present invention is adopted. When the line is operating normally, the bottom of the lightning protection device and the high-voltage side transmission line conductor are insulated by the double gaps of the insulator string gap and the discharge electrode air gap. Compared with the traditional fixed gap or pure air gap lightning arrester, the equivalent capacitance of the two gaps of the insulator string gap and the discharge electrode air gap between the voltage limiter and the transmission line conductor is in parallel relationship, and the discharge electrode air gap is used in conjunction with the insulator string gap.

[0009] In this scheme, the gap between the insulator strings is only a spare gap. In order to avoid multiple discharges in the gap between the insulator strings, which may lead to zero value of the insulator, it is necessary to make the air gap discharge stably when a lightning overvoltage occurs.

[0010] When the line is struck by lightning, the lightning impulse breakdown voltage of the discharge electrode is lower than the lightning impulse breakdown voltage of the newly added insulator string. Therefore, when the overvoltage generated at both ends of the discharge electrode exceeds the operating voltage of the lightning protection device, the voltage limiter is used to limit the voltage at both ends of the protected insulator. When the air gap swings greatly under extreme wind conditions, causing the air gap to fail to discharge, the insulator string between the bottom of the lightning protection device and the transmission line conductor discharges and breaks down, and the voltage limiter is used to limit the voltage at both ends of the protected insulator. The discharge electrode air gap and the insulator string gap are a complete accessory. After selecting the insulator string gap structure height for transmission lines of different voltage levels, the discharge electrode air gap and the insulator string gap are installed as one, and the gap height can be precisely controlled. The lightning impulse breakdown voltage U of 50% of the insulator string gap length L050％ =533×L0+132, where L0 is in meters and U is in kilovolts. The air gap can be equivalent to the rod-plate discharge gap, and its 50% lightning impulse breakdown voltage U L50％ =1556 / (1+3.89 / L). The difficulty of the present invention is how to avoid multiple discharges in the gap of the insulator string, which leads to zero value of the insulator. When the lightning overvoltage is generated, the air gap needs to be stably discharged. The insulation coordination between the gap of the insulator string and the air gap is the key design point. Therefore, the present technical solution considers U L50％ ≤0.9U L050％ , the gap distance relationship must satisfy L≤(0.963+3.89*L0) / (2.996-L0).

[0011] Furthermore, a zinc oxide resistor is provided inside the voltage limiter.

[0012] Furthermore, umbrella skirt silicone rubbers with different diameters are arranged at intervals outside the pressure limiter.

[0013] Furthermore, the diameters of the shed silicone rubber disposed outside the pressure limiter are arranged in the order of large, small, medium, small, large and small, and the diameters of the large, medium and small shed silicone rubber are 300 mm, 240 mm and 180 mm respectively.

[0014] Furthermore, the end of the discharge electrode is tilted upward and forms a 90° angle with the bottom plate electrode of the voltage limiter.

[0015] The end of the discharge electrode is tilted upward to form a rod-plate discharge gap between the end and the bottom of the voltage limiter.

[0016] Furthermore, the discharge electrode is a high-voltage rod-shaped electrode, and is covered with an insulating jacket on the outside.

[0017] Since corona is generated at the root of the discharge electrode and discharges to the gap of the insulator string, an insulating jacket is provided in the section of the discharge electrode close to the insulator to prevent discharge from occurring in this section.

[0018] Furthermore, the discharge electrode is installed on the insulator steel foot of the newly added insulator string in a clamping manner.

[0019] Furthermore, the insulators on the newly added insulator string are tempered glass insulators.

[0020] Furthermore, the diameter of the first insulator of the newly added insulator string is larger than the diameters of the remaining insulators.

[0021] Furthermore, the relationship between the power frequency voltage and the number of insulators on the newly added insulator string is: U=70*N.

[0022] Among them, U is the power frequency voltage, and N is the number of insulators on the newly added insulator string.

[0023] The Y-type double-gap lightning protection device of the present invention forms an integrated parallel double-gap structure with the discharge electrode air gap and the parallel insulator string gap. When the number of insulator pieces on the newly added insulator string is determined, the length of the insulator string gap can be obtained, so the distance of the discharge electrode air gap can be accurately controlled. When there is a lightning overvoltage in the transmission line conductor, the double-gap structure ensures discharge along one of the gaps. The double gap forms a double insurance function to avoid the situation where the overvoltage does not pass through the voltage limiter due to the dispersion of the gap discharge. The installation process is simple, the installation cost is low, and the double-gap structure design ensures high reliability of the lightning protection device.

[0024] Beneficial Effects

[0025] The technical solution of the present invention provides a Y-type double-gap lightning protection device for overhead transmission lines, including: a voltage limiter, an original insulator string and a newly added insulator string; the electrode at the bottom end of the voltage limiter is connected to the top steel cap of the newly added insulator string through an electric conductor, the newly added insulator string is connected to the end steel foot of the original insulator string, and the end of the newly added insulator string is provided with a discharge electrode; a gap of the newly added insulator string is formed between the top steel cap of the newly added insulator string and the discharge electrode; the discharge electrode in the scheme adopts a double-gap structure design, the air gap and the parallel insulator string gap form an integrated parallel double-gap structure, the air gap distance can be accurately controlled after the insulator string gap is determined according to the voltage level, and when there is a lightning overvoltage in the transmission line conductor, the double-gap structure ensures discharge along one of the gaps, and the double gap forms a double insurance function to avoid the situation where the overvoltage does not pass through the voltage limiter due to the dispersion of the gap discharge. The installation process is simple, the installation cost is low, and the double-gap structure design ensures high reliability of the lightning protection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of a Y-type double-gap lightning protection device for overhead power transmission lines according to an example of the present invention;

[0027] Among them: 1-voltage limiter, 2-voltage limiter electrode, 3-connecting wire, 4-discharge electrode, 5-transmission line wire, 6-newly added insulator string, 7-original insulator string. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] like Figure 1 As shown, a Y-type double-gap lightning protection device for an overhead transmission line comprises: a voltage limiter, an original insulator string and a newly added insulator string; the electrode at the bottom end of the voltage limiter is connected to the top steel cap of the newly added insulator string through an electric conductor, the newly added insulator string is connected to the end steel leg of the original insulator string, and a discharge electrode is provided at the end of the newly added insulator string; a gap of the newly added insulator string is formed between the top steel cap of the newly added insulator string and the discharge electrode;

[0030] The length of the air gap formed by the end of the discharge electrode and the bottom of the voltage limiter is L, the length of the newly added insulator string gap hardware string is L0, and L≤(0.963+3.89*L0) / (2.996-L0).

[0031] The electrode at the bottom of the voltage limiter is connected to the top steel cap of the newly added insulator string through an electric conductor, so that the entire body of the lightning protection device and the steel cap on the top insulator of the newly added insulator string form an equipotential;

[0032] In this example, the connecting wire 3 is designed with soft copper wire, one end of which is installed at the bottom of the voltage limiter 1 and the other end is sleeved on the insulator steel cap at the top of the newly added insulator. Its length is determined according to the insulation matching check and windage check, and is slightly longer than the air insulation length.

[0033] 50% lightning impulse breakdown voltage U of the insulator string gap length L050％ =533×L0+132, where L0 is in meters and U is in kilovolts. The air gap can be equivalent to the rod-plate discharge gap, and its 50% lightning impulse breakdown voltage U L50％ =1556 / (1+3.89 / L). The difficulty of the present invention is how to avoid multiple discharges in the gap of the insulator string, which leads to zero value of the insulator. When the lightning overvoltage is generated, the air gap needs to be stably discharged. The insulation coordination between the gap of the insulator string and the air gap is the key design point. Therefore, the present technical solution considers U L50％ ≤0.9U L050％ , the gap distance relationship must satisfy L≤(0.963+3.89*L0) / (2.996-L0).

[0034] The voltage limiter is provided with a zinc oxide resistor inside. When subjected to overvoltage, the zinc oxide resistor limits the residual voltage of the lightning protection device to be lower than the flashover voltage of the original insulator string 7 on the line through its nonlinear resistance characteristics. The original insulator string is the insulator string that needs to be protected.

[0035] Shelter silicone rubbers of different diameters are arranged at intervals on the outside of the voltage limiter, and the diameters of the shelter silicone rubbers arranged on the outside of the voltage limiter are arranged in the order of large, small, medium, small, large and small, and the diameters of the large, medium and small shelter silicone rubbers are 300 mm, 240 mm and 180 mm respectively; the effective value of the power frequency voltage that can be withstood by a group of large, small, medium, small, large and small shelter silicone rubbers is 20 kilovolts, and when the voltage level on the transmission line is high, multiple groups of shelter silicone rubbers are arranged; this design of different diameters of adjacent shelter silicone rubbers can effectively increase the creepage distance and spacing of the shelter of the outer side of the lightning protection device, increase the creepage distance of the surface arc, prevent surface flashover caused by ice, bird droppings or foreign matter, and ensure that the charge transfer path of the lightning overvoltage passes through the zinc oxide resistor.

[0036] The end of the discharge electrode is tilted upward, forming a 90° angle with the plate electrode at the bottom of the voltage limiter. The end of the discharge electrode is tilted upward so that a rod-plate discharge gap is formed between the end and the bottom of the voltage limiter. The size of the gap should be calculated, and the 50% discharge voltage under the lightning overvoltage should be less than the discharge voltage of about 10% of the gap of the insulator string corresponding to the newly added insulator string, so that the lightning overvoltage generates an arc through the discharge electrode 4 to the voltage limiter 1. In order to prevent the arc generated by the discharge electrode 4 from developing toward the insulator string, the electrode set at the bottom of the voltage limiter 1 is a ring-shaped discharge electrode with a larger diameter, so that the arc develops to the bottom of the voltage limiter 1 through the ring-shaped discharge electrode.

[0037] The discharge electrode is a high-voltage rod-shaped electrode with an insulating jacket on the outside. Since corona is generated at the root of the discharge electrode and discharges to the gap of the insulator string, an insulating jacket is provided in the section of the discharge electrode close to the insulator to prevent discharge in this section.

[0038] The discharge electrode is installed on the insulator steel foot of the newly added insulator string in a clamping manner.

[0039] The diameter of the first insulator of the newly added insulator string is larger than the diameters of the other insulators, which can further ensure protection against ice flashover, bird droppings or foreign body flashover, etc.

[0040] The relationship between the power frequency voltage and the number of insulator pieces on the newly added insulator string is: U=70*N; wherein U is the power frequency voltage, and N is the number of insulator pieces on the newly added insulator string.

[0041] The Y-type double-gap lightning protection device of the present invention forms an integrated parallel double-gap structure with the discharge electrode air gap and the parallel insulator string gap. When the number of insulator pieces on the newly added insulator string is determined, the length of the insulator string gap can be obtained, so the distance of the discharge electrode air gap can be accurately controlled. When there is a lightning overvoltage in the transmission line conductor, the double-gap structure ensures discharge along one of the gaps. The double gap forms a double insurance function to avoid the situation where the overvoltage does not pass through the voltage limiter due to the dispersion of the gap discharge. The installation process is simple, the installation cost is low, and the double-gap structure design ensures high reliability of the lightning protection device.

[0042] The number of gaps and dry arc distance of the insulator string are designed according to the voltage level of the transmission line. The gap of the insulator string should be able to withstand the maximum power frequency overvoltage and operating overvoltage of the system. For example, for a 35 kV line, the gap of the insulator string should be able to withstand a maximum voltage of 51 kV. Considering the flexible adjustment of the insulator gap and the convenience of maintenance, glass insulators are selected for the insulators on the newly added insulator string.

[0043] When the discharge gap formed by the discharge electrode 4 and the voltage limiter 1 fails to discharge under the lightning overvoltage, the lightning overvoltage causes the insulator string gap to discharge and break down, and the voltage limiter 1 operates through the connecting wire 23 .

[0044] The Y-type double-gap lightning protection device of the present invention is adopted. When the line is operating normally, the bottom of the lightning protection device and the high-voltage side transmission line conductor are insulated by the double gaps of the insulator string gap and the discharge electrode air gap. Compared with the traditional fixed gap or pure air gap lightning arrester, the equivalent capacitance of the two gaps of the insulator string gap and the discharge electrode air gap between the voltage limiter and the transmission line conductor is in parallel relationship, and the discharge electrode air gap is used in conjunction with the insulator string gap.

[0045] In this scheme, the gap between the insulator strings is only a spare gap. In order to avoid multiple discharges in the gap between the insulator strings, which may lead to zero value of the insulator, it is necessary to make the air gap discharge stably when a lightning overvoltage occurs.

[0046] When the line is struck by lightning, the lightning impulse breakdown voltage of the discharge electrode is lower than the lightning impulse breakdown voltage of the newly added insulator string. Therefore, when the overvoltage generated at both ends of the discharge electrode exceeds the action voltage of the lightning protection device, the voltage limiter is used to limit the voltage at both ends of the protected insulator. When the air gap swings greatly under extreme wind conditions, causing the air gap to fail to discharge, the insulator string between the bottom of the lightning protection device and the transmission line conductor discharges and breaks down, and the voltage limiter is used to limit the voltage at both ends of the protected insulator. The discharge electrode air gap and the insulator string gap are a complete accessory. After selecting the insulator string gap structure height for transmission lines of different voltage levels, the discharge electrode air gap and the insulator string gap are installed as one, and the gap height can be precisely controlled.

[0047] The above content is a further detailed description of the specific implementation methods of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as the patent protection scope of the present invention determined by the submitted claims.

Claims

1. A Y-type double-gap lightning protection device for overhead power transmission lines, characterized in that: include: Voltage limiters, original insulator strings, and newly added insulator strings; The electrode at the bottom end of the voltage limiter is connected to the top steel cap of the newly added insulator string through an electric conductor, the newly added insulator string is connected to the end steel leg of the original insulator string, and a discharge electrode is provided at the end of the newly added insulator string; a gap of the newly added insulator string is formed between the top steel cap of the newly added insulator string and the discharge electrode; The length of the air gap formed by the end of the discharge electrode and the bottom of the voltage limiter is L, the length of the newly added insulator string gap hardware string is L0, and L≤(0.963+3.89*L0) / (2.996-L0).

2. A Y-type double-gap lightning protection device for overhead power transmission lines according to claim 1, characterized in that: A zinc oxide resistor is arranged inside the voltage limiter.

3. A Y-type double-gap lightning protection device for overhead power transmission lines according to claim 2, characterized in that: The outside of the pressure limiter is provided with shed silicone rubbers with different diameters at intervals.

4. A Y-type double-gap lightning protection device for overhead power transmission lines according to claim 3, characterized in that: The diameters of the shed silicone rubber arranged outside the pressure limiter are arranged in the order of large, small, medium, small, large and small. The diameters of the large, medium and small shed silicone rubber are 300 mm, 240 mm and 180 mm respectively.

5. The Y-type double-gap lightning protection device for overhead power transmission lines according to claim 1, characterized in that: The end of the discharge electrode is tilted upward and forms a 90° angle with the bottom plate electrode of the voltage limiter.

6. A Y-type double-gap lightning protection device for overhead power transmission lines according to claim 1, characterized in that: The discharge electrode is a high-voltage rod-shaped electrode with an insulating jacket on the outside.

7. A Y-type double-gap lightning protection device for overhead power transmission lines according to claim 1, characterized in that: The discharge electrode is installed on the insulator steel foot of the newly added insulator string in a clamping manner.

8. The Y-type double-gap lightning protection device for overhead power transmission lines according to claim 1, characterized in that: The insulators on the newly added insulator string are tempered glass insulators.

9. The Y-type double-gap lightning protection device for overhead power transmission lines according to claim 1, characterized in that: The diameter of the first insulator of the newly added insulator string is larger than the diameters of the remaining insulators.

10. The Y-type double-gap lightning protection device for overhead power transmission lines according to claim 1, characterized in that: The relationship between the power frequency voltage and the number of insulators on the newly added insulator string is: U = 70*N; Among them, U is the power frequency voltage, and N is the number of insulators on the newly added insulator string.

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