Strong current impact protection method for buried pipeline near power transmission line tower in shared corridor

Abstract

The invention relates to a strong current impact protection method for a buried pipeline near a power transmission line tower in a shared corridor, and the method comprises the following steps: setting a passive protection means outside the buried pipeline, and / or setting an active protection means near a grounding electrode burying point of the power transmission line tower; the passive protection means comprises the steps that an insulating composite protection layer is arranged on the outer surface of the buried pipeline, and / or an insulating impermeable film is arranged on the periphery of the buried pipeline. The active protection means comprises the step of arranging an arc discharge device on a grounding electrode of a power transmission line tower and around the grounding electrode; wherein at least one passive protection means is selected, and when one passive protection means is selected, the active protection means needs to be adopted synchronously. The device has the advantages that the difficulty of strong current reaching the pipeline is improved, the strong current impact resistance of the pipeline is enhanced, the arc discharge device is adopted to provide a lower directional discharge channel for the arc, the effect of preventing the arc from reaching the pipeline is achieved, protection means are combined for use, and the safety protection level of the pipeline can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas pipeline corrosion control, and in particular to a method for protecting a buried pipeline near a power transmission line tower in a common corridor from strong electric shock. Background Art

[0002] my country's oil, gas and electric energy bases are mainly in the west, and energy consumption is mainly in the eastern coastal areas. In addition, my country has a large population and limited land resources, which leads to the common situation of oil and gas pipelines and power transmission lines sharing corridors. Data show that there have been many cases of power transmission line towers being struck by lightning or short circuit failures at home and abroad, resulting in the breakdown of the anti-corrosion layer of nearby buried pipelines and even ablation damage to the pipe body, posing a safety hazard to the safe operation of the pipeline. When oil and gas pipelines and power transmission lines are built adjacent to each other, due to space limitations in the shared corridor, the two are often forced to approach each other at close range, and sometimes special anti-strong electric shock measures are required to ensure the safety of the oil and gas pipelines. There are two main aspects of the strong electric shock of the transmission line in the shared corridor to the buried pipeline nearby. First, after the lightning strikes the lightning arrester of the nearby transmission line, it reaches the tower grounding grid through the tower grounding wire. Under the action of soil electrical conduction, the lightning current can reach the nearby buried pipeline, causing the pipeline anti-corrosion layer to break down, or even the pipe body to burn. Second, when a phase line short circuit occurs in the transmission line, the fault current will flow into the earth through the transmission line tower grounding electrode, causing similar strong electric shock damage to the nearby pipeline. The strong electric shock of the pipeline in the shared corridor is mainly to protect against these two strong electric hazards.

[0003] At present, the existing strong electric shock protection measures when pipelines are adjacent to transmission lines mainly include maintaining a safe distance and drainage grounding protection. The core approach to maintaining a safe distance is to increase the distance between the transmission line tower and the nearby pipeline. This approach is effective, but in the case of limited space, the increased distance is often limited; drainage grounding is to lay bare zinc strips in the same trench as the pipeline, and periodically connect the bare zinc strips to the pipeline to eliminate the potential difference between the pipeline and the ground, thereby reducing the impact of strong electric current. Existing data show that the drainage grounding measures of the pipeline cannot completely guarantee the interception of arcs. Therefore, under the existing protection measures, there is still a safety risk of breakdown of the pipeline anti-corrosion layer or even ablation or burning of the pipe body under strong electric shock.

[0004] In order to solve the above problems, this patent proposes a method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shocks, which will provide strong technical support for protecting buried pipelines from strong electric shocks and help improve the safety of pipelines. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for protecting underground pipelines near transmission line towers in a common corridor from strong electric shocks, which effectively overcomes the defects of the prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shocks adopts the following method:

[0008] Passive protection measures are installed outside the buried pipeline, and / or active protection measures are installed near the buried point of the grounding electrode of the transmission line tower;

[0009] The above passive protection means include providing an insulating composite protective layer on the outer surface of the buried pipeline, and / or providing an insulating anti-seepage membrane around the buried pipeline; the above active protection means include providing an arc discharge device on and around the grounding electrode of the transmission line tower;

[0010] Among them, at least one of the above passive protection measures is selected, and when one of the above passive protection measures is selected, active protection measures must be adopted simultaneously.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Furthermore, the above-mentioned insulating composite protective layer is an inner and outer double-layer structure, the inner layer is a scratch-resistant intermediate anti-corrosion layer coated on the outer surface of the original anti-corrosion layer of the buried pipeline, and the outer layer is a waterproof sealing layer coated outside the above-mentioned scratch-resistant intermediate anti-corrosion layer.

[0013] Furthermore, the scratch-resistant middle anti-corrosion layer is an epoxy fiberglass layer, and the waterproof sealing layer is a viscoelastic tape layer.

[0014] Furthermore, the above-mentioned insulating composite protective layer is arranged at the position where the vertical distance between the buried pipeline and the transmission line tower is the shortest, and extends toward both ends of the buried pipeline from the point with the shortest distance, and the extension length is at least twice the shortest vertical distance between the buried pipeline and the transmission line tower.

[0015] Furthermore, the insulating anti-seepage membrane surrounds the buried pipeline, and a filler capable of passing electricity is filled between the insulating anti-seepage membrane and the buried pipeline, wherein a straight strip of zinc strip sacrificial anode material is provided in the filler along the length of the pipe.

[0016] Furthermore, the above-mentioned insulating anti-seepage membrane is arranged at the position where the vertical distance between the buried pipeline and the transmission line tower is the shortest, and extends toward the two ends of the buried pipeline at the point where the distance is the shortest. The length of the above-mentioned zinc strip sacrificial anode material is less than the length of the above-mentioned insulating anti-seepage membrane, and both ends are in the above-mentioned insulating anti-seepage membrane.

[0017] Furthermore, the lengths of the insulating anti-seepage membrane extending from the shortest spacing point toward both ends of the buried pipeline are not less than twice the shortest vertical spacing between the buried pipeline and the transmission line tower.

[0018] Furthermore, the above-mentioned arc discharge devices are provided in plurality and are buried at intervals around the buried points of the grounding electrodes of the transmission line towers.

[0019] Furthermore, the grounding electrode of the transmission line tower is covered with petroleum coke backfill material on all sides, and the arc discharge device is arranged outside the area covered by the petroleum coke backfill material.

[0020] Furthermore, two arc discharge devices are provided, and are distributed at equal intervals on both sides of the buried point of the grounding electrode of the transmission line tower along the direction of the transmission line, and the buried depth of the grounding electrode of the transmission line tower is the same as the buried depth of the arc discharge device, and the spacing between a single arc discharge device and the grounding electrode of the transmission line tower is equal to the spacing between the grounding electrode of the transmission line tower and the buried pipeline.

[0021] The beneficial effects of the present invention are as follows: the purpose of protection is achieved by increasing the difficulty of strong electric current reaching the pipeline and enhancing the pipeline's ability to withstand strong electric shocks. At the same time, an arc discharge device is used to provide the arc with a lower directional discharge channel, which plays a role in intercepting the arc from reaching the pipeline. The combined use of protective measures can improve the pipeline safety protection level and greatly reduce the risk of breakdown of the pipeline anti-corrosion layer and ablation at defective points of the anti-corrosion layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a layer structure diagram of the insulating composite protective layer involved in the strong electric shock protection method of the buried pipeline near the transmission line tower in the shared corridor of the present invention;

[0023] Figure 2 It is a schematic structural diagram of the insulating anti-seepage membrane involved in the strong electric shock protection method for buried pipelines near power transmission line towers in a shared corridor of the present invention, which is arranged around the buried pipeline;

[0024] Figure 3 The invention relates to an arc discharge device involved in a method for protecting a buried pipeline near a transmission line tower in a shared corridor from strong electric shock.

[0025] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0026] 1. Insulating composite protective layer; 2. Insulating anti-seepage membrane; 3. Arc discharge device; 11. Scratch-resistant intermediate anti-corrosion layer; 12. Waterproof sealing layer; 21. Zinc strip sacrificial anode material. DETAILED DESCRIPTION

[0027] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0028] Example: Figure 1 ,2 As shown in FIG. 3 , the method for protecting underground pipelines near transmission line towers in a shared corridor from strong electric shocks in this embodiment adopts the following method:

[0029] Passive protection measures are installed outside the buried pipeline, and / or active protection measures are installed near the buried point of the grounding electrode of the transmission line tower;

[0030] The above passive protection means include providing an insulating composite protective layer 1 on the outer surface of the buried pipeline, and / or providing an insulating anti-seepage membrane 2 around the buried pipeline;

[0031] The above-mentioned active protection means include setting an arc discharge device 3 on and around the grounding electrode of the transmission line tower;

[0032] Among them, at least one of the above passive protection measures is selected, and when one of the above passive protection measures is selected, active protection measures must be adopted simultaneously.

[0033] The method for protecting buried pipelines near transmission line towers in the shared corridor of this embodiment from strong electric shock can be implemented in the following combinations:

[0034] 1) Passive protection means: Comprehensive protection is provided by providing an insulating composite protective layer 1 on the outer surface of the buried pipeline and an insulating anti-seepage membrane 2 around the buried pipeline.

[0035] 2) Passive + active protection means: Comprehensive protection is provided by providing an insulating composite protective layer 1 on the outer surface of the buried pipeline and an arc discharge device 3 on the grounding electrode and surrounding areas of the transmission line tower.

[0036] 3) Passive + active protection means: Comprehensive protection is provided by installing an insulating anti-seepage membrane 2 around the buried pipeline and installing an arc discharge device 3 around the grounding electrode of the transmission line tower.

[0037] 4) Passive + active protection means: Comprehensive protection is achieved by installing an insulating composite protective layer 1 on the outer surface of the buried pipeline, installing an insulating anti-seepage membrane 2 around the buried pipeline, and installing an arc discharge device 3 on and around the grounding electrode of the transmission line tower.

[0038] Any one of the above combinations can be selected for protection based on actual engineering practice.

[0039] The entire protection method achieves the purpose of protection by increasing the difficulty of strong electric current reaching the pipeline and enhancing the pipeline's ability to withstand strong electric shocks. At the same time, an arc discharge device is used to provide the arc with a lower directional discharge channel, which plays a role in intercepting the arc from reaching the pipeline. The combined use of protection measures can improve the pipeline safety protection level and greatly reduce the risk of breakdown of the pipeline anti-corrosion layer and ablation at the defective points of the anti-corrosion layer.

[0040] As a preferred embodiment, Figure 1 As shown, the above-mentioned insulating composite protective layer 1 is a double-layer structure of inner and outer layers, the inner layer is a scratch-resistant intermediate anti-corrosion layer 11 coated on the outer surface of the original anti-corrosion layer (represented by b in the figure) of the buried pipeline (represented by a in the figure), and the outer layer is a waterproof sealing layer 12 coated on the outside of the above-mentioned scratch-resistant intermediate anti-corrosion layer 11.

[0041] In the above embodiment, the inner layer adopts a scratch-resistant intermediate anti-corrosion layer 11, which has the function of preventing the anti-corrosion layer from having damage points and increasing the voltage resistance of the overall anti-corrosion system to high voltage shock, and preventing the arc from flashing to the weak defects of the anti-corrosion layer and causing the pipe body to be ablated; the outer layer adopts a waterproof sealing layer 12, which is used to prevent moisture in the soil medium from penetrating into the pipeline surface, resulting in a corrosive environment on the pipeline surface. In actual engineering, the length of the insulating composite protective layer 1 outside the buried pipeline is determined as follows:

[0042] The shortest vertical distance between the buried pipeline and the edge of the grounding electrode of the adjacent transmission line tower is set to D1, and the length of the insulating composite protective layer 1 starts from the point where the vertical distance between the adjacent transmission line tower and the buried pipeline is the shortest, and extends to the upstream and downstream of the buried pipeline respectively (that is, the insulating composite protective layer 1 is set at the position where the vertical distance between the buried pipeline and the transmission line tower is the shortest, and extends toward the two ends of the buried pipeline at the point with the shortest distance), and extends to both ends by a length of at least 2D1 (that is, the lengths of the insulating composite protective layer 1 extending from the point with the shortest distance toward the two ends of the buried pipeline are both at least twice the shortest vertical distance between the buried pipeline and the transmission line tower).

[0043] Among them, the scratch-resistant intermediate anti-corrosion layer 11 in this embodiment adopts the epoxy fiberglass layer of the prior art (which can be a coating applied on the surface of the buried pipeline), and the waterproof sealing layer 12 adopts the viscoelastic tape layer of the prior art.

[0044] As a preferred embodiment, Figure 2 As shown, the insulating anti-seepage membrane 2 surrounds the buried pipeline, and the space between the insulating anti-seepage membrane 2 and the buried pipeline is filled with a filler (such as fine soil, etc.) that can pass electricity, and a straight zinc strip sacrificial anode material 21 is provided in the filler along the length of the pipe.

[0045] In the above implementation scheme, installing an insulating anti-seepage membrane 2 on the buried pipeline near the transmission line tower in the shared corridor can play two roles. First, the insulating anti-seepage membrane 2 can prevent the impact current from flowing into the pipeline. Second, once the buried pipeline is damaged and leaks, the insulating anti-seepage membrane 2 can prevent the oil from spreading and polluting the soil. Among them, the insulating anti-seepage membrane 2 is installed between the buried pipeline and the soil. In order to ensure that the wrapped (buried pipeline) pipe section can obtain sufficient cathodic protection current, a linear zinc strip sacrificial anode material 21 (such as magnesium strip or zinc strip) needs to be installed in the insulating anti-seepage membrane 2. In actual engineering, the length of the insulating anti-seepage membrane 2 constructed outside the buried pipeline is determined as follows:

[0046] The shortest vertical distance between the buried pipeline and the edge of the grounding electrode of the adjacent transmission line tower is set to D2, and the length of the insulating and anti-seepage membrane 2 starts from the point where the vertical distance between the adjacent transmission line tower and the buried pipeline is shortest, and extends toward the upstream and downstream of the buried pipeline respectively (that is, the insulating and anti-seepage membrane 2 is set at the position where the vertical spacing between the buried pipeline and the transmission line tower is the shortest, and extends toward the two ends of the buried pipeline at the point with the shortest spacing), and extends to both ends by a length of not less than 2D2 (that is, the lengths of the insulating and anti-seepage membrane 2 extending toward the two ends of the buried pipeline at the point with the shortest spacing are not less than twice the shortest vertical spacing between the buried pipeline and the transmission line tower).

[0047] In addition, the length of the zinc strip sacrificial anode material 21 is less than (shorter than) the length of the insulating anti-seepage membrane 2, and both ends are located inside the insulating anti-seepage membrane 2 (that is, both ends of the zinc strip sacrificial anode material 21 do not extend out of the insulating anti-seepage membrane 2).

[0048] As a preferred embodiment, the above-mentioned arc discharge devices 3 are provided in plurality and are buried at intervals around the buried point of the grounding electrode (denoted by d in the figure) of the transmission line tower (denoted by c in the figure).

[0049] In the above-mentioned embodiment, the zinc strip sacrificial anode material 21 is made of bare metal material, which can strengthen the grounding, provide a lower directional discharge channel for the arc, and play a role in intercepting the arc from reaching the pipeline. When the voltage between the buried pipeline and the grounding electrode of the adjacent transmission line tower reaches the level of arc generation, it is easier to generate an arc between the grounding electrode of the transmission line tower and the additional arc discharge device 3. When the voltage between the buried pipeline and the grounding electrode of the transmission line tower reaches the level of arc generation, it is easier to generate an arc between the grounding electrode of the transmission line tower and the arc discharge device 3, discharging the energy of the strong electric shock deep into the earth, reducing the energy reaching the pipeline, and reducing the risk of the pipeline anti-corrosion layer breaking through and burning through the pipe wall. The advantages of this method are low cost, reduction or no need to install surface mitigation facilities, no need to be electrically connected to the pipeline and the transmission line tower, and maintaining the independence of the pipeline and the transmission line tower.

[0050] In this embodiment, Figure 3 As shown, the arc discharge device 3 is provided with two, and is distributed at equal intervals along the direction of the transmission line on both sides of the grounding electrode buried point of the transmission line tower. Specifically, during the project implementation, the installation position of the arc discharge device 3 is determined by the following method:

[0051] Assuming that the closest distance between the buried pipeline and the grounding electrode of the adjacent transmission line tower is D3, the distance between the single arc discharge device 3 and the grounding electrode of the transmission line tower is equal to the distance between the grounding electrode of the transmission line tower and the buried pipeline.

[0052] In this embodiment, the arc discharge device 3 is a horizontally arranged linear component, and its two ends are respectively connected to vertical grounding rods, and the lower end of the grounding rod is buried in the ground, and the burial depth is the same as the burial depth of the grounding electrode of the above-mentioned transmission line tower. The extension direction of the arc discharge device 3 is perpendicular to the extension direction of the transmission line (that is, the extension direction of the arc discharge device 3 is perpendicular to the routing direction of the transmission line). Of course, the number of grounding rods is not limited to two, and one or more grounding rods can also be added in the middle area of ​​the arc discharge device 3. In addition, the grounding electrode of the above-mentioned transmission line tower is covered with petroleum coke backfill material all around (specifically, the petroleum coke backfill material is backfilled at the local position where the grounding electrode is located), and the covering thickness is about 5 cm. The above-mentioned arc discharge device 3 is arranged outside the coverage area of ​​the petroleum coke backfill material.

[0053] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0054] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0055] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0057] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0058] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for protecting underground pipelines near transmission line towers in a shared corridor from strong electric shocks, characterized in that: Use the following method: Passive protection measures are installed outside the buried pipeline, and / or active protection measures are installed near the buried point of the grounding electrode of the transmission line tower; The passive protection means comprises providing an insulating composite protective layer (1) on the outer surface of the buried pipeline, and / or providing an insulating anti-seepage membrane (2) around the buried pipeline; The active protection means comprises arranging an arc discharge device (3) on and around the grounding electrode of the transmission line tower; Among them, at least one of the passive protection means is selected, and when one of the passive protection means is selected, an active protection means must be used simultaneously.

2. A method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shocks according to claim 1, characterized in that: The insulating composite protective layer (1) is an inner and outer double-layer structure, wherein the inner layer is a scratch-resistant intermediate anti-corrosion layer (11) coated on the outer surface of the original anti-corrosion layer of the buried pipeline, and the outer layer is a waterproof sealing layer (12) coated outside the scratch-resistant intermediate anti-corrosion layer (11).

3. A method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shocks according to claim 2, characterized in that: The scratch-resistant middle anti-corrosion layer (11) is an epoxy glass fiber reinforced plastic layer, and the waterproof sealing layer (12) is a viscoelastic tape layer.

4. The method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shock according to claim 1, characterized in that: The insulating composite protective layer (1) is arranged at the position where the vertical distance between the buried pipeline and the transmission line tower is the shortest, and extends from the point where the distance is the shortest towards both ends of the buried pipeline, and the extension length is at least twice the shortest vertical distance between the buried pipeline and the transmission line tower.

5. The method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shock according to claim 1, characterized in that: The insulating anti-seepage membrane (2) surrounds the buried pipeline, and a filler capable of passing electricity is filled between the insulating anti-seepage membrane (2) and the buried pipeline, wherein a straight zinc strip sacrificial anode material (21) is arranged in the filler along the length direction of the pipeline.

6. A method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shocks according to claim 5, characterized in that: The insulating anti-seepage membrane (2) is arranged at a position where the vertical distance between the buried pipeline and the transmission line tower is the shortest, and extends toward the two ends of the buried pipeline at the point where the distance is the shortest. The length of the zinc strip sacrificial anode material (21) is less than the length of the insulating anti-seepage membrane (2), and both ends are located inside the insulating anti-seepage membrane (2).

7. A method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shocks according to claim 6, characterized in that: The lengths of the insulating anti-seepage membrane (2) extending from the shortest spacing point toward the two ends of the buried pipeline are not less than twice the shortest vertical spacing between the buried pipeline and the transmission line tower.

8. A method for protecting underground pipelines near transmission line towers in a shared corridor from strong electric shocks according to any one of claims 1 to 7, characterized in that: A plurality of arc discharge devices (3) are provided and are buried at intervals around the buried points of the grounding electrodes of the transmission line towers.

9. A method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shocks according to claim 8, characterized in that: The grounding electrode of the transmission line tower is covered with petroleum coke backfill material on all sides, and the arc discharge device (3) is arranged outside the area covered by the petroleum coke backfill material.

10. A method for protecting buried pipelines near transmission line towers in a shared corridor from strong electric shocks according to claim 9, characterized in that: Two arc discharge devices (3) are provided and are distributed at equal intervals along the direction of the transmission line on both sides of the buried point of the grounding electrode of the transmission line tower, and the buried depth of the grounding electrode of the transmission line tower is the same as the buried depth of the arc discharge device (3), and the distance between a single arc discharge device (3) and the grounding electrode of the transmission line tower is equal to the distance between the grounding electrode of the transmission line tower and the buried pipeline.

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