A lightning overvoltage protection method and device for oil and gas pipeline

Abstract

The present invention relates to the technical field of lightning overvoltage protection, and discloses a lightning overvoltage protection device for an oil and gas pipeline, comprising a metal pipeline, the outer side of the metal pipeline is wrapped with an insulating layer, the metal pipeline is connected with a monitoring and protection device through a wire, and the monitoring and protection device is connected with a lightning protection device through a metal wire. The lightning overvoltage protection method and device for the oil and gas pipeline can not only effectively discharge the pipeline lightning overvoltage, but also can stop the zinc oxide resistor from running when the direct current into the ground causes an overvoltage on the pipeline, thereby ensuring the safety of the zinc oxide resistor.

Description

Technical Field

[0001] The present invention relates to the technical field of lightning overvoltage protection, and in particular to a lightning overvoltage protection method and device for an oil and gas pipeline. Background Art

[0002] The ground near the buried oil and gas pipeline or the exposed part of the ground is prone to lightning strikes, causing lightning overvoltage on the oil and gas pipeline. The 3-PE layer of the oil and gas pipeline insulation is prone to breakdown failure under lightning overvoltage. Therefore, lightning protection devices are arranged on oil and gas pipelines. Traditional lightning protection devices connect the metal part of the oil and gas pipeline to the grounding body through zinc oxide resistors. Zinc oxide resistors are usually in a high resistance state, and in a low resistance state under pipeline lightning overvoltage, limiting the lightning overvoltage to a lower level.

[0003] In recent years, long-distance, large-capacity DC transmission projects and gas and oil pipeline projects have developed rapidly. my country's land resources are tight, and the grounding electrodes of DC transmission projects are very close to buried metal pipelines in many places. Natural gas metal pipelines are inevitably affected by the DC grounding electrode's ground current. When one pole of the DC transmission system fails or is under maintenance, the DC transmission system will temporarily adopt a single-pole loop operation mode. Under the single-pole loop operation mode of the DC transmission system, the DC grounding electrode will inject current into the soil, which will cause changes in the potential of the nearby soil. When a metal pipeline is buried in the nearby soil, the DC grounding electrode's ground current will generate an induced potential on the pipeline, causing a potential difference between the pipeline and the nearby soil, resulting in an excessively large potential difference between the pipeline and the ground, up to several hundred volts, and the potential of the pipeline increases rapidly.

[0004] The zinc oxide resistor will show a lower resistance state under a larger potential difference between the pipe and the ground, causing a large amount of DC grounding electrode current to flow into the earth through the zinc oxide resistor. The zinc oxide resistor has a good transient current capacity and discharges lightning current, but the continuous current capacity is very weak and discharges DC current. Under the action of the DC grounding electrode current, the heat capacity of a large number of zinc oxide resistors exceeds the standard, and the damage failure rate of the lightning protection device is very high. For this reason, we have proposed a lightning overvoltage protection method and device for oil and gas pipelines. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In view of the deficiencies in the prior art, the present invention provides a lightning overvoltage protection method and device for oil and gas pipelines, which solve the above-mentioned problems.

[0007] (II) Technical solution

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a lightning overvoltage protection device for an oil and gas pipeline, comprising a metal pipeline, the outer side of the metal pipeline is wrapped with an insulating layer, the metal pipeline is connected to a monitoring and protection device through a wire, and the monitoring and protection device is connected to a lightning protection device through a metal wire.

[0009] Preferably, the monitoring and protection device includes a current sensor, a timer and a controllable switch, the current sensor and the timer are both connected to the controllable switch, and the current sensor and the timer are connected to a wire connected to the metal pipe.

[0010] Preferably, the lightning protection device includes a sealed explosion-proof insulating shell, an insulating material and a zinc oxide resistor, the metal wire extends into the interior of the sealed explosion-proof insulating shell, the zinc oxide resistor is installed at the bottom of the sealed explosion-proof insulating shell, the insulating material is arranged above the zinc oxide resistor, and the zinc oxide resistor is connected to the ground.

[0011] Preferably, the insulating material is ceramic or glass.

[0012] A method for protecting an oil and gas pipeline from lightning overvoltage comprises the following steps:

[0013] Step 1: When a lightning overvoltage acts on a metal pipe, the insulating material is broken down, and the zinc oxide resistor is turned on to discharge the lightning current. When the lightning overvoltage is eliminated, the insulating material returns to the insulating state, and the zinc oxide resistor is disconnected from the metal pipe.

[0014] Step 2: When the metal pipeline is operating normally, the zinc oxide resistor is separated from the metal pipeline by the insulating material. When a DC grounding current flows into the ground, causing a large pipe-to-ground overvoltage, the pipe-to-ground overvoltage is much smaller than the flashover voltage of the insulating material and cannot break through the insulating material, so the zinc oxide resistor will not flow through the DC grounding current.

[0015] Preferably, when the zinc oxide resistor overheats and fails, its resistance drops to a very small value, and after the lightning overvoltage breaks through the insulation gap, the metal pipe is grounded through the zinc oxide resistor. At this time, the zinc oxide resistor is very small and damaged, and the lightning current is very large. The current and duration can be measured by the current sensor and timer. When the current exceeds the set value, the controllable switch is disconnected, and the lightning current can be discharged through other normal lightning protection devices. At the same time, the disconnected state of the controllable switch shows that the lightning protection device with the insulation gap has a fault.

[0016] (III) Beneficial effects

[0017] Compared with the prior art, the present invention provides a method and device for lightning overvoltage protection of oil and gas pipelines, which has the following beneficial effects:

[0018] 1. The lightning overvoltage protection method and device for oil and gas pipelines can not only effectively discharge pipeline lightning overvoltage, but also shut down the zinc oxide resistor when the direct current into the ground causes pipe-to-ground overvoltage, thereby ensuring the safety of the zinc oxide resistor.

[0019] 2. The lightning overvoltage protection method and device for the oil and gas pipeline sets the gap breakdown voltage based on the surface insulation distance. Compared with the breakdown voltage of a pure air gap, the surface breakdown voltage is more stable and less dispersed, which is beneficial to reducing false operations.

[0020] 3. The lightning overvoltage protection method and device of the oil and gas pipeline are sealed with explosion-proof insulating shell. The sealing is mainly to protect the internal air from the influence of environmental humidity and to ensure that the surface breakdown voltage will not change due to humidity changes; the explosion-proof is mainly to ensure that the flashover breakdown arc does not affect the safety of the combustible gas inside the oil and gas pipeline, and the lightning protection device should have a large safety distance from the oil and gas pipeline.

[0021] 4. The lightning overvoltage protection method and device for oil and gas pipelines can effectively increase the service life of zinc oxide resistors and reduce the failure probability of zinc oxide.

[0022] 5. The lightning overvoltage protection method and device for the oil and gas pipeline, the lightning protection device with an insulating gap has its own fault monitoring and protection function, and is composed of a current measuring device, a timing device and a switch, which can not only ensure that excessive current does not flow through the pipeline, but also display the fault of the lightning protection device with an insulating gap through the disconnected state of the switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the present invention;

[0024] Figure 2 It is a schematic diagram of the lightning protection device of the present invention;

[0025] Figure 3 This is a schematic diagram of the operation of the lightning protection device of the present invention;

[0026] Figure 4 Schematic diagram of monitoring and protection device.

[0027] In the figure: 1. Metal pipe; 2. Insulation layer; 3. Monitoring and protection device; 4. Lightning protection device; 5. Current sensor; 6. Timer; 7. Controllable switch; 8. Metal wire; 9. Sealed explosion-proof insulating casing; 10. Insulation material; 11. Zinc oxide resistor. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1-4 A lightning overvoltage protection device for an oil and gas pipeline includes a metal pipeline 1, the outer side of the metal pipeline 1 is wrapped with an insulating layer 2, the metal pipeline 1 is connected to a monitoring and protection device 3 through a wire, and the monitoring and protection device 3 is connected to a lightning protection device 4 through a metal wire 8.

[0030] The monitoring and protection device 3 includes a current sensor 5 , a timer 6 and a controllable switch 7 . The current sensor 5 and the timer 6 are both connected to the controllable switch 7 , and the current sensor 5 and the timer 6 are connected to a wire connected to the metal pipe 1 .

[0031] The lightning protection device 4 includes a sealed explosion-proof insulating shell 9, an insulating material 10 and a zinc oxide resistor 11. The metal wire 8 extends to the inside of the sealed explosion-proof insulating shell 9. The zinc oxide resistor 11 is installed at the bottom of the sealed explosion-proof insulating shell 9. The insulating material 10 is arranged above the zinc oxide resistor 11. The zinc oxide resistor 11 is connected to the ground. When the metal pipeline 1 is operating normally, the air between the metal wire 8 and the zinc oxide resistor 11 and the insulating material 10 together form an insulating medium. The zinc oxide resistor 11 is insulated from the metal pipeline 1, ensuring that the metal pipeline 1 has good insulation and is not connected to the ground through the zinc oxide resistor 11, thereby ensuring the stability of the cathodic protection potential on the oil and gas pipeline.

[0032] The insulating material 10 is ceramic or glass.

[0033] A method for protecting an oil and gas pipeline from lightning overvoltage comprises the following steps:

[0034] Step 1: When a lightning overvoltage acts on the metal pipe 1, the insulating material 10 is broken down, and the zinc oxide resistor 11 is turned on to discharge the lightning current. When the lightning overvoltage is eliminated, the insulating material 10 recovers the insulation state, and the zinc oxide resistor 11 is disconnected from the metal pipe 1;

[0035] Step 2: When the metal pipe 1 operates normally, the zinc oxide resistor 11 is isolated from the metal pipe 1 by the insulating material 10. When a DC grounding current flows into the ground causing a large pipe-to-ground overvoltage, the pipe-to-ground overvoltage is much smaller than the flashover voltage of the insulating material 10 and cannot break through the insulating material 10, so that the zinc oxide resistor 11 will not flow through the DC grounding current.

[0036] When the metal pipe 1 is disturbed by the direct current into the ground, assuming that the potential difference between the oil and gas pipeline and the ground is U, the maximum currently measured is 300 volts, and the length of the insulating material 10 is adjusted to be set to L, so that the surface flashover voltage of the insulating material 10 is 2-3U, thereby ensuring that the insulating material 10 does not flash over along the surface under the action of the pipe-ground potential difference, ensuring that the zinc oxide resistor 11 is insulated from the insulating material 10, so that the direct current into the ground does not flow through the zinc oxide resistor 11, thereby ensuring the safety of the zinc oxide resistor 11 under the action of the direct current into the ground;

[0037] Step 3: When the lightning overvoltage is eliminated, the surface flashover arc is extinguished, the surface insulation recovers to a good insulation state, the zinc oxide resistor 11 is disconnected from the oil and gas pipeline, and the lightning protection device 4 stops operating.

[0038] When the zinc oxide resistor 11 overheats and fails, its resistance drops to a very small value. After the lightning overvoltage breaks through the insulation gap, the metal pipe 1 is grounded through the zinc oxide resistor 11. At this time, the zinc oxide resistor is very small and has been damaged. The lightning current is very large. The current sensor 5 and the timer 6 can measure the current and duration. When the current exceeds the set value, the controllable switch 7 is disconnected. This can ensure that excessive current does not flow through the metal pipe 1, and the lightning current can be discharged through other normal lightning protection devices. At the same time, the disconnected state of the controllable switch 7 can also display the failure of the lightning protection device with the insulation gap.

[0039] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lightning overvoltage protection device for oil and gas pipelines, characterized in that: It comprises a metal pipe (1), the outer side of the metal pipe (1) is wrapped with an insulating layer (2), the metal pipe (1) is connected to a monitoring and protection device (3) via a wire, and the monitoring and protection device (3) is connected to a lightning protection device via a metal wire (8); The lightning protection device (4) comprises a sealed explosion-proof insulating shell (9), an insulating material (10) and a zinc oxide resistor (11); the metal wire (8) extends into the sealed explosion-proof insulating shell (9); the zinc oxide resistor (11) is installed at the bottom of the sealed explosion-proof insulating shell (9); and the insulating material (10) is arranged above the zinc oxide resistor (11); the zinc oxide resistor (11) is connected to the earth; when the metal pipe (1) operates normally, the air between the metal wire (8) and the zinc oxide resistor (11) and the insulating material (10) together form an insulating medium; the zinc oxide resistor (11) is insulated from the metal pipe (1), thereby ensuring that the metal pipe (1) has good insulation and is not connected to the earth through the zinc oxide resistor (11); When the metal pipeline (1) is disturbed by a direct current entering the ground, the pipe-to-ground potential difference U of the oil and gas pipeline is determined so that the surface flashover voltage of the insulating material (10) is 2-3U; The monitoring and protection device (3) comprises a current sensor (5), a timer (6) and a controllable switch (7); the current sensor (5) and the timer (6) are both connected to the controllable switch (7), and the current sensor (5) and the timer (6) are connected to a wire connected to the metal pipe (1).

2. The lightning overvoltage protection device for oil and gas pipelines according to claim 1 is characterized in that: The insulating material (10) is ceramic or glass.

3. A method for implementing lightning overvoltage protection for oil and gas pipelines using the lightning overvoltage protection device for oil and gas pipelines as claimed in claim 1, characterized in that: The following steps are involved: The first step: when a lightning overvoltage acts on the metal pipe (1), the insulating material (10) is broken down, and the zinc oxide resistor (11) is turned on to discharge the lightning current. When the lightning overvoltage is eliminated, the insulating material (10) recovers the insulation state, and the zinc oxide resistor (11) is disconnected from the metal pipe (1); Step 2: When the metal pipe (1) operates normally, the zinc oxide resistor (11) is isolated from the metal pipe (1) by the insulating material (10). When a DC grounding current flows into the ground causing an overvoltage between the pipe and the ground, the overvoltage between the pipe and the ground is smaller than the flashover voltage of the insulating material (10) and cannot break through the insulating material (10). Therefore, the zinc oxide resistor (11) will not flow with the DC grounding current.

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