CN112653063B - Lightning Protection Method for 10kV Overhead Line Using Coupling Ground Wire and Lightning Arrester - Google Patents

Abstract

The invention discloses a 10kV overhead line lightning protection method for matching use of a coupling ground wire and a lightning arrester, which comprises the following steps: firstly, considering the influence on the mechanical aspects such as the bearing of a line tower and the like after the coupling ground wires are additionally arranged, and checking the applicability of the coupling ground wires to obtain the installation number of the coupling ground wires. And secondly, under various extreme conditions (ice coating and windage yaw), ensuring that no discharge occurs between the coupling ground wire and the lead at the center of the span, so as to determine the installation position of the coupling ground wire, and further providing a method for testing the lightning resistance level of the 10kV overhead line containing the coupling ground wire. Aiming at the problem that the lightning withstand level is reduced after the coupling ground wire is erected in sections, a lightning protection method for matching the coupling ground wire sections with a lightning arrester is provided, a 10kV overhead line lightning overvoltage simulation calculation model is established by using simulation software, so that the lightning protection effect of matching the coupling ground wire sections with an MOA is tested under the condition that two-phase short circuit of a distribution line does not occur. The lightning protection method can further improve the lightning protection level of the 10kV distribution line and improve the operation reliability of the distribution network on the basis of the existing lightning protection design.

Description

Lightning Protection Method for 10kV Overhead Line Using Coupling Ground Wire and Lightning Arrester

technical field

The invention relates to the field of lightning protection of overhead lines of 10kV distribution network, in particular to a lightning protection method of 10kV overhead lines used in conjunction with a coupled ground wire and a lightning arrester (MOA).

Background technique

The 10kV distribution line is an important connection part between the transmission line and the user end, and the safe and stable operation of the distribution line is very important. At present, most of the 10kV overhead lines adopt typical designs. Due to their large insulation margin and relatively low tower height, most overhead lines do not need lightning protection measures. Take measures such as installing MOA and reducing grounding resistance. This measure can meet the lightning protection needs of most areas, but in some areas with strong lightning activities, the lightning resistance level still cannot meet the requirements.

In mountainous areas, mining areas and other places with strong lightning activities, the lightning protection measures adopted for 10kV overhead lines are basically the installation of line MOA, but the 10kV line MOA is prone to failures and forms short-circuit points. Maintenance costs are high. In addition, the towers that are prone to direct hits are generally due to terrain and other reasons. After the MOA is installed, the tower needs to be grounded to reduce the grounding resistance. There are problems of construction difficulties and high costs, and the usage of MOA needs to be reduced.

Coupling ground wire is a common lightning protection measure in transmission lines. It is installed at the junction between the conductor and the tower body. Through the coupling effect with each phase conductor and the shunting effect of lightning current, the lightning resistance level of the line is improved. In order to ensure the safe operation of the distribution line when erecting the coupled ground wire on the tower of a 10kV overhead distribution line, it is necessary to focus on two limitations: (1) Under various extreme conditions (icing and wind deflection), it should be ensured that There will be no discharge between the coupling ground wire and the wire at the center of the span; (2) After installing the coupling ground wire, make sure that the allowable range of the tower's load-bearing capacity is not exceeded. In order to ensure that the line will not exceed the load-bearing range of the tower after the coupling ground wire is installed.

The coupled ground wire has a good protection effect on the two types of lightning strikes, i.e. induction lightning and lightning strike cross arm. While it can bring a better lightning protection effect, it also has some drawbacks: in crossing roads, rivers and hillsides, due to the ground The height limit factor cannot be installed, and it needs to be erected in sections, which cannot improve the level of lightning resistance.

Therefore, it is necessary to combine the two lightning protection measures of the coupled ground wire and the arrester to comprehensively improve the lightning resistance level of the 10kV overhead line.

SUMMARY OF THE INVENTION

The invention provides a lightning protection method for a 10kV overhead line using a coupled ground wire and a lightning arrester, so as to solve the application method of the coupled ground wire in the 10kV overhead line, and proposes to install MOA at the segment of the coupled ground wire The method is used to solve the problem that the lightning resistance level of the line is reduced due to the segment of the coupled ground wire.

In order to solve the above-mentioned technical problems, the technical scheme proposed by the present invention is:

1. The application method of coupling ground wire in 10kV overhead line, including the following steps:

1.1 Calculate the applicability of the installation of the coupled ground wire according to the mechanical influence on the load-bearing of the line tower after the installation of the coupled ground wire, and obtain the installation quantity of the coupled ground wire.

In order to ensure the safe and stable operation of the distribution line after the coupling ground wire is erected, the calculation of the load bearing of the tower is particularly important. After erecting the coupled ground wire, the vertical load on the tower will increase. The vertical load on the tower includes: (1) the gravity load of the wire, the coupled ground wire, the insulator string and the hardware; (2) the additional vertical load during installation and maintenance, including workers , the gravity load of the tool. Calculate the vertical load value G _Dk and the vertical load design value G _D after considering icing respectively, where

G _Dk =nγ ₁ AL _V +G _J +nγ ₂ AL _V +G _J (K-1) (1)

G _D =γ _G nγ ₁ AL _V +γ _G G _J +γ _Q nγ ₂ AL _V +γ _G G _J (K-1)+G _f (2)

In formulas (1) and (2), n is the number of wires; L _V is the vertical span of the tower, m: γ ₁ , γ ₂ are the vertical specific loads before and after icing, N/(m·mm ² ); K is the icing coefficient, and when the designed icing thickness is 5 mm, take 1.075; G _f is the additional vertical load during installation and maintenance

If G _Dk < G _D , and the minimum margin requirement can be met, the tower load-bearing requirement can be met after the coupled ground wire is erected.

According to the typical setting of tower type and material of 10KV line tower, generally 10KV line tower should be installed with a single coupling ground wire. In the present invention, the proposed application method of the coupled ground wire in the 10KV overhead line is a single coupled ground wire. As shown in Figure 1, it includes a coupling ground wire (1), the coupling ground wire (1) is arranged below the lower wire cross arm (2), and the coupling ground wire (1) is provided with a hoop (3), and the coupling ground wire (1) It is fixed by the hoop (3) and connected with the tower (4).

1.2 Determination of the installation position of the coupling ground wire

The installation position of the coupling ground wire used in the present invention in the 10kV overhead line tower is shown in Figure 1, and it should be located below the wire cross arm (2). The ground wire (1) is fixed by the hoop (3) and connected to the tower (4). The key is to determine the distance P below the cross arm.

The distance between the coupling ground wire and the wire must be greater than a certain safety distance, and the distance between the wire and the ground wire in the center of the span must meet the

S≥0.012L+1 (3)

In formula (3), S is the distance between the coupling ground wire and the conductor when the span is in the center; L is the span of the line.

By formula (3), the distance S between the coupling ground wire and the wire can be determined when the distance is in the center. Because both the overhead wire and the coupled ground wire have a certain sag, and the size of the sag is related to factors such as temperature and icing. After selecting the bare wire, insulated wire and coupled ground wire of the specific applicable model, the maximum sag H of various wire types under different spans under extreme conditions is found. Finally, the suspension position P of the coupled ground wire can be determined according to the geometric position relationship by the distance S and the maximum sag H from the center of the span.

The present invention obtains the installation position of the coupled ground wire of the 10KV line tower according to the above calculation method. For 10kV overhead bare conductor lines, hang the coupling ground wire at 4.2m directly below the bottom crossarm, that is, P=4.2m; for 10kV overhead insulated conductor lines, hang the coupling ground wire directly below the bottom crossarm 5.3m, namely P=5.3m. At this time, the distance between the bottom bare wire and the coupling ground wire is 2.13m in the center of the pitch, and the distance between the insulated wire and the coupling ground wire is 2.03m. This distance can meet the requirements of various extreme conditions. There is no discharge between the wire and the coupling ground wire. distance requirements.

The lightning protection method of the 10kV overhead line used in conjunction with the coupling ground wire and the arrester of the present invention also includes the simulation calculation for testing the lightning resistance level of the 10kV overhead line including the coupled ground wire, including the following steps:

In the test, the ATP-EMTP simulation software was used to establish the lightning overvoltage simulation calculation model of 10kV overhead lines, and the simulation models of 10kV single-circuit and double-circuit distribution lines were established in ATP-EMPT respectively. It includes a 9-base tower, the distance between lines is 80m, the leftmost is a 10kV three-phase AC power supply, the insulator flashover model is simplified to a voltage-controlled switch instead, and the 50% impulse breakdown voltage of the insulator is 139kV. In ATP-EMTP, the bare wire and coupled ground wire models are selected by the JMARTI model that can reflect the frequency characteristics in the LCC, and the insulated wire model is replaced by the single-core cable model.

Two typical circuit arrangements of single-circuit triangular and double-circuit linearly arranged conductors were tested respectively. Under the three lightning strike modes of induced lightning overvoltage, lightning strike to the tower top line and lightning strike to the cross arm, after erecting the coupled ground wire, the 10kV overhead bare conductor and insulation were tested. Influence law of lightning resistance level of conductors.

Since the neutral point in the 10kV power distribution system adopts an ineffective grounding method, the line will trip immediately only when a two-phase or three-phase short circuit occurs. Therefore, the defined lightning resistance level is the minimum current amplitude at which the two-phase or three-phase line insulation flashover occurs in the distribution line when the line is struck by lightning. In the simulation test, a small current is first applied, the amplitude of the lightning current is gradually increased, and the flashover of the insulator is observed. When a 2-phase or 3-phase insulator flashover occurs, the corresponding minimum lightning current amplitude is recorded as the lightning resistance level of the line.

Taking the line shape, tower shape and span in the typical design of 10kV overhead line as a calculation example, the effect of adding coupled ground wire to the line's lightning resistance level is obtained. For the single-circuit delta-arranged line, after erecting the coupled ground wire, the lightning resistance level of the bare conductor line is up to 86.3%, and the lightning resistance level of the insulated conductor line is up to 90.8%; The lightning resistance level of bare conductor lines has been increased by up to 79.9%, and the lightning resistance level of insulated conductor lines has been increased by up to 112.7%.

After the coupling ground wire is used in sections, the lightning resistance level of the cross arm is the same as when the coupling ground wire is not erected. When the coupled ground wire is erected at a distance of 5 base poles, the lightning resistance level of the induced lightning is equivalent to the lightning resistance level of the uncoupled ground wire.

The lightning protection method of the 10kV overhead line used in conjunction with the coupling ground wire and the arrester of the present invention also includes a method for cooperating with the MOA at the segment of the 10kV overhead line coupling ground wire and testing the effect, including:

Since the MOA has the function of direct lightning strike protection, the present invention is mainly aimed at two types of lightning strikes: induction lightning and lightning strike cross arm. A single-circuit 10kV overhead distribution line simulation model is built in ATP-EMTP, including 13-base towers, MOA is simulated by nonlinear resistance, and the models of insulators, conductors and coupled ground wires are the same as the previous section.

In the simulation, the coupled ground wires between No. 6-8 towers and No. 5-9 towers are disconnected respectively. Taking the disconnection of the coupled ground wires between No. 5-9 towers as an example, the schematic diagram is shown in Figure 2. Considering the most serious situation, the lightning strike point of the direct lightning strike is set on the cross arm of the No. 7 tower, and the induction mine is set at a distance of 100m from the No. 7 tower. The lightning resistance level when MOA is installed in different phases of the 1-4 base towers on the left and right of the No. 7 tower is obtained by simulation calculation. In the simulation test, a small current is first applied, the amplitude of the lightning current is gradually increased, and the flashover of the insulator is observed. When a 2-phase or 3-phase insulator flashover occurs, the corresponding minimum lightning current amplitude is recorded as the lightning resistance level of the line.

After simulation calculation, Fig. 3 and Fig. 4 respectively show the variation law of lightning resistance level when the segmented coupling ground wire cooperates with B, C-phase and three-phase MOA when the cross arm is struck by lightning. Figure 5 and Figure 6 respectively show the variation law of lightning resistance level when the segmented coupling ground wire cooperates with B, C phase and three-phase MOA when lightning is induced.

It can be seen that (1) when lightning strikes the cross arm, the continuous installation of MOA at the segment of the coupling ground wire can make up for the problem of reduced lightning resistance level caused by the use of segmented erection of the coupling ground wire. Among them, the lightning resistance level of B and C-phase MOA installation is slightly higher than that of three-phase installation MOA, and B, C-phase installation of MOA has better economic benefits; (2) Under the action of induction lightning, when the coupled ground wire is opened When the breaking range is small (between No. 6-8 towers), the lightning protection effects of B and C-phase MOA and three-phase MOA are almost the same. When the breaking range of the coupling ground wire is expanded (between No. 5-9 towers) , The coordination effect of three-phase installation MOA and coupling ground wire is obviously better than that of B and C two-phase installation.

Therefore, when the ground wire is coupled with a segmented interval of 3 bases and within the tower, the present invention proposes to install MOA in the phase B and C (the highest phase and the side phase) of the step-by-step tower at the segmented interval (including 2 ends); when the coupled ground When the line segment interval is more than 3 bases, the present invention proposes three-phase installation of MOA in the step-by-step tower at the segment interval (including 2 ends).

The present invention has the following beneficial effects:

The lightning protection method of the 10kV overhead line used in conjunction with the coupling ground wire and the lightning arrester of the present invention takes into account the sag changes caused by extreme weather such as icing. The optimal installation position is designed, which can guide the installation of the device of the present invention safely, accurately and quickly.

According to the invention, it can be measured that: for a single-circuit delta-arranged line, after erecting the coupled ground wire, the lightning resistance level of the bare wire line is increased by 43.2% at the highest, and the lightning resistance level of the insulated wire circuit is increased by 74.5% at the highest; for the double-circuit straight line arrangement , After the coupling ground wire is erected, the lightning resistance level of the bare wire line is increased by 44.7%, and the lightning resistance level of the insulated wire line is increased by 54.5%.

After being used in conjunction with the MOA at the coupled ground wire segment, the overvoltage across the insulators of the entire line can be greatly reduced, effectively solving the problem of the reduction in the lightning resistance level caused by the coupled ground wire segment.

In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail below with reference to the accompanying drawings.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached image:

FIG. 1 is a schematic diagram of a tower structure of a 10kV single-circuit overhead line with a coupled ground wire installed in a preferred embodiment of the present invention.

FIG. 2 is a schematic diagram of a segmented coupling ground wire erected on a No. 5-9 tower according to a preferred embodiment of the present invention.

3 is a schematic diagram of the variation law of the lightning resistance level of the segmented coupling ground wire and the B and C phase MOAs when the cross arm is struck by a preferred embodiment of the present invention;

4 is a schematic diagram of the variation law of the lightning resistance level of the segmented coupled ground wire and the three-phase MOA when the cross arm is struck by lightning according to the preferred embodiment of the present invention;

Fig. 5 is a schematic diagram of the variation law of the lightning resistance level when the segmented coupling ground wire and the B and C phase MOAs cooperate with the lightning-induced lightning according to the preferred embodiment of the present invention;

FIG. 6 is a schematic diagram of the variation law of the lightning resistance level when the segmented coupling ground wire and the three-phase MOA cooperate with the inductive lightning according to the preferred embodiment of the present invention;

7 is a schematic diagram of the voltage waveform at both ends of the insulator when the single-circuit bare wire is unprotected during lightning induction according to a preferred embodiment of the present invention;

8 is a schematic diagram of the voltage waveform across the insulator when the single-circuit bare wire is erected to couple the ground wire during inductive lightning according to the preferred embodiment of the present invention;

9 is a schematic diagram of the voltage waveforms at both ends of the insulator when the double-circuit bare wire is unprotected during lightning induction according to a preferred embodiment of the present invention;

10 is a schematic diagram of the voltage waveforms at both ends of the insulator when the double-circuit bare wire is erected to couple the ground wire during inductive lightning according to the preferred embodiment of the present invention;

The symbols in the figure represent:

1. Coupling ground wire; 2. Cross arm; 3. Metal hoop; 4. Pole tower.

Detailed ways

The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

1. The lightning protection method of the 10kV overhead line used in conjunction with the coupling ground wire and the arrester includes the following steps:

1.1 Calculate the applicability of the installation of the coupled ground wire according to the mechanical influence on the load-bearing of the line tower after the installation of the coupled ground wire, and obtain the installation quantity of the coupled ground wire.

According to formula (1) and formula (2), the vertical load value and vertical load design value of single- and double-circuit bare conductors and insulated conductors with different numbers of coupled ground wires can be obtained. The calculation results are shown in Table 1.

Table 1 Vertical loads of towers

It can be seen that the vertical load value after erecting a single coupled ground wire is less than the vertical load design value, and meets the margin requirements, which can meet the load-bearing needs of the tower. If two coupled ground wires are set, the vertical load value is greater than the vertical load design value, and the load bearing of the line tower cannot meet the requirements. Therefore, one coupling ground wire is used in the present invention.

1.2 Determination of the installation position of the coupling ground wire

The typical span of a 10kV distribution line is 80m, which can be obtained from formula (3): the distance S between the conductor and the ground wire at the center of the span should be greater than 1.96m. Taking the typical wire type selection standard of 10kV line as an example, the coupling ground wire is GJ-25 steel stranded wire, the bare wire is JL/G1A-70/10 steel core aluminum stranded wire, and the insulated wire is JKLYJ-10/70 aluminum core cross-connection wire. Linked polyethylene insulated overhead cable, the specific parameters are shown in Table 2.

Table 2 Wire parameters of 10kV distribution line

It can be obtained from the above calculation method that the coupled ground wire is hung 4.2m directly below the single-circuit and double-circuit bare conductor cross-arm, and 5.3m directly under the single-circuit and double-circuit insulated conductor cross-arm. The distance between the ground wire in the center of the gear distance is 2.13m, and the distance between the insulated wire and the coupled ground wire is 2.03m. This distance can meet the requirements of the distance between the wire and the coupled ground wire without discharge under various extreme conditions.

2. Test the lightning protection effect of 10kV distribution line with coupled ground wire

In ATP-EMTP, the simulation models of 10kV single-circuit and double-circuit distribution lines are built respectively, including 9-base towers, the span between lines is 80m, the leftmost is 10kV three-phase AC power supply, and the insulator flashover model is simplified to one The voltage-controlled switch is replaced, and the 50% impulse breakdown voltage of the insulator is 139kV. In ATP-EMTP, the bare wire and coupled ground wire models are selected by the JMARTI model that can reflect the frequency characteristics in the LCC, and the insulated wire model is replaced by the single-core cable model. The wire type and parameters are shown in Table 2.

There are three main forms of lightning strikes that cause tripping of 10kV distribution lines: induction lightning, lightning strikes on conductors, and lightning strikes on poles and towers. Commonly used conductors for 10kV distribution lines are divided into bare conductors and insulated conductors, and the tower shape is divided into single-circuit lines and multi-circuit lines on the same tower. Thus, for 10kV distribution lines, 12 different typical lightning strike situations are set.

2.1 Effect of coupled ground wire on lightning resistance level of 10kV bare conductor

2.1.1 Induction lightning resistance level

In the simulation test, the inductive lightning strike point is set at one end of the line, 100m away from the first base tower. First apply a small current, gradually increase the amplitude of the lightning current, and observe the insulator flashover. When a 2-phase or 3-phase insulator flashover occurs, the corresponding minimum lightning current amplitude is recorded as the induced lightning resistance level of the line.

(1) Single-circuit line

When the amplitude of the induced lightning current is gradually increased to 37.2kA on the line, a two-phase flashover occurs on the line at this time, and the voltage waveform of the two terminals of the insulator when the single-circuit delta-arranged bare conductor is unprotected is shown in Figure 7. When the ground wire is coupled, the lightning resistance level of induction lightning is 37.2kA.

When erecting a coupled ground wire, in the same way, when an inductive lightning with an amplitude of 69.3kA acts on the line, a two-phase flashover occurs on the line, and the voltage waveform at the two terminals of the insulator is shown in Figure 8. Due to the coupling effect of the coupled ground wire, the overvoltage at both ends of the insulator string can be greatly reduced, and the lightning resistance level is increased by 86.3% after the coupled ground wire is erected.

(2) Double circuit line

When the double-circuit six-phase line is simultaneously subjected to inductive lightning with an amplitude of 36.9kA, a three-phase flashover occurs on the first circuit at this time, and the voltage waveform at the two terminals of the insulator when the double-circuit delta-arranged bare conductor is unprotected is shown in Figure 9 shown. Since there is no protective effect of the coupled ground wire, the lightning resistance level when the coupled ground wire is not erected is 36.9kA.

When the coupled ground wire is erected, in the same way, when the double-circuit six-phase line and the coupled ground wire are simultaneously subjected to inductive lightning with an amplitude of 66.4kA, a three-phase flashover occurs on the first circuit line. At this time, the insulator 2 ends The voltage waveform is shown in Figure 10. Compared with the non-coupling ground wire, the lightning resistance level of induction lightning is improved by 79.9% after the coupling ground wire is set up.

2.1.2 Lightning resistance level when lightning strikes the pole and tower cross arm (counterattack)

When lightning strikes the cross arm of the tower, set the point of direct lightning strike on the cross arm of the tower, gradually increase the amplitude of the lightning, and observe the flashover of the insulator. When 2-phase or 3-phase insulator breakdown occurs, the corresponding maximum lightning current amplitude is the lightning resistance level of the line. The lightning resistance levels of single and double circuit lines when lightning strikes conductors are summarized in Table 3 and Table 4.

2.1.3 Lightning resistance level when lightning strikes the wire

For the towers arranged in a single-circuit triangle, the intermediate phase is the B-phase conductor. For double-circuit linearly arranged towers, the highest phase is also the B-phase conductor. Therefore, at this time, it is only considered that the direct lightning strike acts on the B-phase wire, so as to obtain the lightning resistance level in each case, and the method for obtaining the lightning resistance level is the same as above. The lightning resistance levels of single and double circuit lines when lightning strikes conductors are summarized in Table 3 and Table 4.

2.1.4 Simulation result analysis of lightning resistance level of 10kV bare conductor

After the above simulation test, the lightning resistance level test results of single and double-circuit bare conductors are arranged in Table 3 and Table 4.

Table 3 Lightning resistance level of single-circuit bare conductor

Table 4 Lightning resistance level of double-circuit bare conductors

It can be seen from Table 3 and Table 4 that after erecting the coupled ground wire, it has a significant effect on improving the lightning resistance level of the bare conductor induced lightning and the lightning strike on the cross arm of the tower. When induction lightning acts on the line, the lightning resistance level of induction lightning for single-circuit and double-circuit bare conductors can be increased by 86.3% and 79.9% respectively after the coupling ground wire is erected. When lightning strikes the cross arm of the tower, the lightning resistance level of the single-circuit and double-circuit bare conductors can be increased by 36.2% and 44.7% respectively after the coupling ground wire is erected.

However, the effect of improving the lightning resistance level when the phase conductor is directly struck is not obvious. After the coupled ground wire is erected, the lightning resistance level of the single-circuit and double-circuit bare conductors can only be increased by 4% and 13.6%, respectively.

2.2 Effect of coupled ground wire on lightning resistance level of 10kV insulated conductor

For the 10kV overhead insulated conductor, in the simulation model of the insulated conductor, according to the same method as the previous section, when different conductor arrangements are calculated, the direct lightning strikes the cross arm, the direct lightning strikes the conductor and the induction lightning, the lines before and after the coupling ground wire are erected. level of lightning resistance. Similarly, the minimum current amplitude of two-phase or three-phase line insulation flashover in distribution lines is taken as the lightning resistance level.

Table 5 Lightning resistance level of single-circuit insulated wire

Table 6 Lightning resistance level of double-circuit insulated wire

It can be seen from Table 5 and Table 6 that after erecting the coupled ground wire, it also has a significant effect on improving the lightning resistance level of the 10kV insulated wire and the lightning resistance level when the lightning strikes the cross arm of the tower. When the induction lightning acts on the insulated wire, the lightning resistance level of induction lightning for the single-circuit and double-circuit insulated conductors can be increased by 90.8% and 112.7% respectively after the coupling ground wire is erected. When the lightning strikes the cross arm of the tower, the lightning resistance level of the single-circuit and double-circuit insulated conductors can be increased by 74.5% and 53.2% respectively after the coupling ground wire is erected.

However, the effect of improving the lightning resistance level when the insulated conductor is directly hit is still not obvious. After the coupling ground wire is erected, the lightning resistance level of the single-circuit and double-circuit bare conductors can only be increased by 7% and 13.6%, respectively.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

3. The test of lightning protection effect, including the following steps:

3.1 Construction of Simulation Test Platform

A single-circuit 10kV overhead distribution line simulation model is built in ATP-EMTP, including 13-base towers, the span between lines is 80m, and the leftmost side is a 10kV three-phase AC power supply. The insulator flashover model is simplified to a voltage-controlled switch. Instead, the 50% impulse breakdown voltage of the insulator is 139kV. In ATP-EMTP, the model of bare wire and coupled ground wire is the JMARTI model that can reflect the frequency characteristics in LCC. The wire type and parameters are shown in Table 2.

3.2 Test the effect of installing MOA on the lightning overvoltage at the coupling ground section of the 10kV overhead line.

Taking the single-circuit delta-arranged bare conductor as an example, the model of a 10kV distribution line with a single coupled ground wire is simulated in the simulation software. In the simulation, a small current is firstly applied, the amplitude of the lightning current is gradually increased, and the flashover of the insulator is observed. When a 2-phase or 3-phase insulator flashover occurs, the corresponding minimum lightning current amplitude is recorded as the lightning resistance level of the line. After simulation calculation, the lightning resistance levels under different coupling ground wire erection methods under the condition of lightning strike cross arm and induction lightning are obtained, as shown in Table 7.

Table 7 Lightning resistance levels under different coupling ground wire erection methods

It can be seen that when the coupled ground wire is erected with a 5-base pole tower, the lightning resistance level of the cross-arm and induced lightning is equivalent to the lightning resistance level of the uncoupled ground wire. Therefore, only the coupling ground wire interval of 3 bases and the interval of 5 bases are considered in the simulation test. Happening.

3.2.1 The lightning protection effect of the use of segmented coupling ground wire and MOA when lightning strikes the cross arm

(1) Installation method of MOA's B and C phases (the highest phase and the side phase)

In order to verify the lightning protection effect of the segmented coupled ground wire used in conjunction with the B and C-phase MOAs when the cross arm is struck by lightning, according to the above simulation model, the two cases of the coupling ground wire interval of 3 bases and the interval of 5 bases are considered respectively. Set on the cross arm of the No. 7 tower, first apply a small current, gradually increase the amplitude of the lightning current, and observe the insulator flashover. When a 2-phase or 3-phase insulator flashover occurs, the corresponding minimum lightning current amplitude is recorded as the lightning resistance level of the line.

Figure 3 shows the variation law of the lightning resistance level of the segmented coupling ground wire and the B and C phase MOA when the cross arm is struck by lightning. The simulation results show that (1) when lightning strikes the cross arm, only MOA is installed on the vulnerable tower, and when the MOA installation density does not extend to the tower at the coupled ground wire segment, the lightning protection level of the segmented coupled ground wire is not as good as that of the whole line erection. ; (2) When the MOA installation density extends to the tower where the coupled ground wire is disconnected, the overall lightning resistance level of the line is slightly better than that of the coupled ground wire erected across the line.

(2) Three-phase installation method of MOA

According to the same method, verify the lightning protection effect of the segmented coupling ground wire and the three-phase MOA when the cross arm is struck by lightning. Figure 4 shows the variation law of the lightning resistance level of the segmented coupled ground wire and the three-phase MOA when the cross arm is struck by lightning.

The simulation results show that (1) when lightning strikes the cross arm, the lightning protection effect of the segmented coupled ground wire and the three-phase MOA is obviously better than that of the three-phase MOA; (2) after the MOA is continuously installed at the segment, the The lightning protection effect of the segment coupling ground wire used in conjunction with the three-phase MOA is roughly the same as the effect of the full-line coupling ground wire used in conjunction with the MOA.

To sum up, the lightning resistance level of MOA installed in B and C phases is slightly higher than that of three-phase installation MOA, and the installation of MOA in B and C phases has better economic benefits. Therefore, in view of the lightning strike crossarm, the continuous installation of B and C phase MOA at the coupling ground segment has better lightning protection effect.

3.2.2 Lightning protection effect of using segmented coupling ground wire with MOA when lightning is induced

The induction lightning adopts the MODELS induction lightning module in ATP. Assuming that the lightning current channel is perpendicular to the ground, the lightning return speed is 3×10 ⁸ m/s, and the soil resistivity is 1000Ω·m. In the simulation, the coupled ground wires between the No. 6-8 towers and the No. 5-9 towers are also disconnected respectively. Considering the most serious situation, the lightning-induced lightning strike point is set at a distance of 100m from the No. 7 tower.

(1) Installation method of MOA's B and C phases (the highest phase and the side phase)

The lightning-induced lightning strike point is set at a distance of 100m from the No. 7 tower, and the lightning resistance level under the MOA installed on the B and C phases of the 1-4 base towers on the left and right of the No. 7 tower is obtained. Figure 5 shows the variation law of the lightning resistance level under the cooperation of the segmented coupled ground wire and the B and C phase MOAs when lightning is induced.

The simulation results show that (1) for induction lightning, when the segmented range of the coupled ground wire is small (between No. 6 and No. 8 towers), when MOA is installed on the B and C phases of the three-base towers on the left and right of the lightning strike tower, its anti-fighting effect will be reduced. The lightning effect is the same as when the coupled ground wire is erected on the whole line; (2) when the segmented range of the coupled ground wire is large (between No. 5-9 towers), after gradually increasing the installation density of B and C phase MOA, the The lightning effect is still not as good as setting up a coupling ground wire across the board.

(2) Three-phase installation method of MOA

According to the same method, verify the lightning protection effect of using the segmented coupling ground wire and the three-phase MOA under the induction lightning. Figure 6 shows the variation law of the lightning resistance level of the segmented coupled ground wire and the three-phase MOA when the cross arm is struck by lightning.

The simulation results show that (1) for the induction lightning, when the MOA installation density is two bases on the left and right of the lightning strike tower and below, the larger the segmented range of the coupled ground wire, the lower the lightning resistance level of the induction lightning. And under this installation density, the lightning protection effect is not as good as that of erecting the coupling ground wire on the whole line; (2) When installing MOA on the three-phase of each three-base tower on the left and right of the tower, the three-phase MOA is continuously installed at the segment of the coupling ground wire. , and a three-phase MOA is also installed at the adjacent base tower at the subsection. At this time, the lightning protection effect is the same as when the coupled ground wire is erected on the whole line.

To sum up, the lightning protection method of the 10kV overhead line using the coupling ground wire and the lightning arrester of the present invention is significantly improved compared with the lightning protection effect of only installing the MOA under the two lightning strike forms of lightning strike cross arm and induction lightning. When the coupling ground segment interval is 3 bases and the tower is within, install MOA on the B and C phases (the highest phase and the side phase) of the step-by-step tower at the segment interval (including 2 ends); when the coupling ground segment interval is 3 When the tower is above the foundation, the MOA is installed in three phases of the step-by-step tower at the segment interval (including 2 ends). It can effectively solve the problem of the reduction of the lightning resistance level caused by the segmented coupling ground wire.

Claims (5)

1. the lightning protection method of the 10kV overhead line that a coupling ground wire and lightning arrester cooperate to use, is characterized in that, comprises: S1: Calculate the applicability of the line tower after adding the coupled ground wire, and obtain the installation quantity of the coupled ground wire; the calculation of the applicability of the line tower after the addition of the coupled ground wire includes the following steps: Calculate the vertical load value G _{Dk after erecting the coupling ground wire; the vertical load value G Dk after} the coupling ground wire is erected is the sum of the vertical loads of the conductor, the coupling ground wire, the insulator string and the hardware after the icing; consider the installation and maintenance The additional vertical load and the effect of icing at the time of calculation, _calculate the vertical load design value _{G D} of the _{tower ;} After the ground wire can meet the load-bearing requirements of the tower; The vertical load value G _Dk and the vertical load design value G _D of the tower after the coupling ground wire is erected are calculated by the following formulas: G _Dk =nγ ₁ AL _V +G _J +nγ ₂ AL _V +G _J (K-1) (1) G _D =γ _G nγ ₁ AL _V +γ _G G _J +γ _Q nγ ₂ AL _V +γ _G G _J (K-1)+G _f (2) In formulas (1) and (2), n is the number of wires; L _V is the vertical span of the tower, m: γ ₁ , γ ₂ are the vertical specific loads before and after icing, N/(m·mm ² ); K is the icing coefficient; G _f is the additional vertical load during installation and maintenance; A is the cross-sectional area of the wire, in mm ² ; G _J is the vertical load of the fittings; γ _G is the permanent load partial coefficient; γ _Q is the variable load partial factor; S2: Under the extreme conditions of icing and wind deflection, according to the requirement that no discharge occurs between the coupling ground wire and the conductor at the center of the span, determine the installation position of the coupling ground wire, and conduct the 10kV overhead line with the coupling ground wire. Lightning resistance level test; S3: Use simulation software to establish a simulation calculation model for lightning overvoltage of 10kV overhead line, so that the distribution line does not have two-phase short-circuit as a condition, test the lightning protection effect of the coupling ground wire segment used in conjunction with the arrester. 2 . The lightning protection method for a 10kV overhead line using a coupled ground wire and a surge arrester according to claim 1 , wherein the coupled ground wire is set as a single coupled ground wire in the 10KV overhead line. 3 . 3. The lightning protection method of the 10kV overhead line used in conjunction with the coupling ground wire and the arrester according to claim 1, wherein said determining the installation position of the coupling ground wire comprises the following steps: When the coupling ground wire is erected on the tower of the 10kV overhead distribution line, the distance S between the coupling ground wire and the conductor at the center of the span satisfies: S≥0.012L+1 (3) In formula (3), S is the distance between the coupling ground wire and the conductor when the span is in the center; L is the span of the line; By formula (3), the distance S between the coupling ground wire and the conductor can be determined at the center of the span; after selecting the bare wire, insulated wire and coupled ground wire of the specific applicable model, it can be found that under extreme conditions, various wire types are different in different sizes. The maximum sag H under the span; the suspension position P of the coupled ground wire is determined according to the geometric position relationship from the distance S and the maximum sag H from the center of the span. 4. The lightning protection method of the 10kV overhead line used in conjunction with the coupling ground wire and the arrester according to claim 3, it is characterized in that, for the 10kV overhead bare wire line, the coupling ground wire is hung on the lowermost cross arm 4.2 m; for 10kV overhead insulated conductor lines, hang the coupling ground wire at 5.3m directly below the lowest cross arm. 5. The lightning protection method of the 10kV overhead line used in conjunction with the coupling ground wire and the arrester according to claim 1, is characterized in that, the installation method of the arrester at the coupling ground wire segment is: (1) For the two types of lightning strikes of induction lightning and lightning strike cross arm, when the coupling ground wire is segmented at 3 bases and within the tower, install lightning arresters at the segment interval and the B and C phases of the step-by-step tower at both ends; (2) When the coupling ground wire has a segment interval of more than 3 bases, install lightning arresters at the segment interval and the three-phase towers at both ends.

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