A method and apparatus for repairing the main insulation of a high voltage power cable by external injection

Abstract

The present specification provides a high-voltage power cable transverse injection main insulation repair method and device, relates to the technical field of cable repair. The method comprises setting a repair groove in the area with defects of the main insulation layer, the repair groove penetrating the outer sheath and the metal sheath in turn, and the groove side wall of the repair groove away from the outer sheath being arranged at the position close to the main insulation layer of the water-blocking buffer layer; the repair liquid with targeted induction characteristics and penetration characteristics is injected into the cable in a pressurized manner through the repair groove; after the repair groove is blocked, the repair liquid is induced to diffuse towards the cable core direction in a manner of applying voltage to repair the defects existing in the main insulation layer. By setting the repair groove, the repair liquid with targeted induction characteristics and penetration characteristics is injected into the cable, and under the combined action of a specific electric field and a specific temperature, the dielectric induction repair liquid penetrates to the defect position of the main insulation layer to achieve the effect of local precise repair, which can effectively improve the construction efficiency and effect of cable repair.

Description

Technical Field

[0001] This invention relates to the field of cable repair technology, and more specifically, to a method and apparatus for repairing the main insulation of high-voltage power cables by external injection. Background Technology

[0002] As an indispensable and crucial component of power transmission lines, the reliability of power cables plays a decisive role in the stability and safety of the entire power system. Cross-linked polyethylene (XLPE) power cables, due to their excellent electrical and mechanical properties, account for a large proportion of the market, with many cable lines having been in operation for 20 years. To ensure the safe operation of transmission lines, cables with severe insulation problems can be replaced entirely, or hidden defects in the XLPE insulation can be repaired to extend the service life of the cable insulation. However, replacing the entire cable would consume enormous human, material, and financial resources, failing to meet the requirements of cost reduction and efficiency improvement. Power cable insulation repair technology, under limited cost conditions, can effectively repair defects in cables, enhance the insulation of existing aging power cable lines, and significantly extend their service life, possessing significant economic and social value.

[0003] Currently, the injection-type repair method for the main insulation of power cables typically involves installing adapters for injecting siloxane repair fluid at both ends of the cable, and then applying pressure using an air pump to inject the siloxane repair fluid into the gaps in the cable's aluminum core. Under air pressure, the repair fluid penetrates into the cable's insulation layer, seeping from the core outwards. Specifically, under pressure, the repair fluid gradually penetrates into the XLPE layer. Maintaining pressure for 4 to 12 hours allows the repair fluid to gradually penetrate the insulation layer and produce a repair effect. However, this method requires injection-type repair while the cable is out of service, necessitates re-fabricating the cable termination after repair, and the pressure-driven penetration repair from the core outwards can easily cause irreversible secondary damage to the cable. Summary of the Invention

[0004] Firstly, the purpose of this application is to provide a method for repairing the main insulation of high-voltage power cables by external injection, which can overcome the defects of the existing methods.

[0005] Secondly, another objective of this application is to provide a main insulation repair device for high-voltage power cables via external injection, which has all the advantages of the aforementioned main insulation repair method for high-voltage power cables via external injection.

[0006] The embodiments of this application are implemented as follows:

[0007] In a first aspect, this application provides a method for repairing the main insulation of a high-voltage power cable via external injection, mainly comprising:

[0008] Repair grooves are provided in areas where the main insulation layer is defective. The repair grooves penetrate the outer sheath and the metal sheath in sequence. The sidewalls of the repair grooves away from the outer sheath are located in the water-blocking buffer layer near the main insulation layer.

[0009] Repair fluid is injected into the cable under pressure through the repair groove; the repair fluid has targeted induction properties.

[0010] After sealing the repair groove, voltage is applied to induce the repair fluid to diffuse toward the cable core in order to repair the defects in the main insulation layer.

[0011] In some embodiments of this application, after sealing the repair groove, the step of inducing the repair fluid to diffuse towards the cable core by applying voltage to repair defects in the main insulation layer includes:

[0012] By applying an induced voltage with an effective value of 2kV~5kV and a frequency of 10 Hz~50Hz for 6h~10h, the repair fluid is induced to diffuse from the water-blocking buffer layer toward the cable core.

[0013] Alternatively, by restoring the cable to its original power-on state, the repair fluid can be induced to diffuse towards the cable core through the self-water-blocking buffer layer.

[0014] In some embodiments of this application, the total amount of the repair fluid injected into the repair tank is not less than 2L, and the injection time of the repair fluid is 10min~20min.

[0015] In some embodiments of this application, the repair solution comprises the following components by weight:

[0016] The main insulation layer repair component consists of 20 to 25 parts, the flowability modification component consists of 30 to 40 parts, the mixed stabilizer component consists of 0 to 5 parts, the catalyst consists of 3 to 5 parts, and the targeting inducer consists of 5 to 10 parts.

[0017] In some embodiments of this application, the targeting inducer is one or a combination of at least two of 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and hexamethylphosphoric triamine in any mass ratio.

[0018] In some embodiments of this application, the main insulation layer repair component is methylphenyldimethoxysilane, and the flowability modification component is trimethylmethoxysilane.

[0019] In some embodiments of this application, the mixed stabilizer is at least one of dimethyldibutoxysilane, methyldimethoxyethylphenylsilane and cyanomethyldimethoxysilane or any combination of them in any mass ratio.

[0020] In some embodiments of this application, the catalyst is one or at least two of the following in any mass ratio: titanium isopropoxide, titanium isopropoxy, titanium ethanol, titanium isopropoxide, titanium n-butoxide, titanium methyl methoxide, tetraisopropyl titanate, potassium hydroxide, and hydrochloric acid.

[0021] Secondly, this application provides a main insulation repair device for high-voltage power cables via external injection, which mainly includes a pressurizing device, a liquid storage device and an injection device connected in sequence. The liquid storage device is used to store repair liquid, and the pressurizing device can output a preset injection pressure to the liquid storage device.

[0022] The injection end of the injection device is located on the side wall of the repair tank away from the outer sheath, and the repair fluid stored in the liquid storage device can be injected into the cable through the injection device at a preset injection pressure.

[0023] In some embodiments of this application, the above-mentioned device further includes a control valve, a flow meter, and a protection valve; the protection valve, the flow meter, and the control valve are sequentially disposed on the connection link between the liquid storage device and the injection device, and the protection valve is disposed on the connection link between the pressurizing device and the liquid storage device.

[0024] The embodiments of this application have the following advantages or beneficial effects:

[0025] This high-voltage power cable main insulation repair method, involving external injection, involves creating a repair groove by drilling holes from the outside of the cable inwards. A repair fluid with targeted induction and penetration properties is injected into the cable. Under the combined action of a specific electric field and temperature, the dielectric induces the repair fluid to penetrate to the defect location in the main insulation layer, achieving precise local repair. This method effectively improves the construction efficiency and effectiveness of cable repair. Furthermore, by repairing localized areas, this method avoids irreversible structural damage to old or micro-cracked areas of the cable. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A schematic flowchart illustrating the external injection method for repairing the main insulation of high-voltage power cables provided in this application;

[0028] Figure 2 A schematic diagram of the high-voltage cross-linked polyethylene power cable structure and a schematic diagram of the repair groove setting method provided in this application;

[0029] Figure 3 This is a schematic diagram showing the location of the repair groove provided in this application;

[0030] Figure 4 A schematic diagram of the main insulation repair device for high-voltage power cables injected from the outside, as provided in this application;

[0031] Figure 5 A schematic diagram of the main insulation repair device for high-voltage power cables injected from the outside, provided in this application, in its operational state.

[0032] Icons: 1. Injection nozzle; 2. Control valve; 3. Flow meter; 4. Protection valve; 5. Liquid storage tank; 6. Air compressor; 7. Repair tank; 8. Outer sheath; 9. Metal sheath; 10. Water-blocking buffer layer; 11. Main insulation layer; 111. Insulation shielding layer; 112. Cross-linked polyethylene layer; 113. Conductor shielding layer; 12. Cable core. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Generally, the components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0034] Please refer to Figures 1 to 3 One embodiment of this application provides a method for repairing the main insulation of a high-voltage power cable via external injection, mainly including:

[0035] Step 102: Set a repair groove in the area of ​​the main insulation layer with defects. The repair groove passes through the outer sheath and the metal sheath in sequence. The groove sidewall away from the outer sheath is set in the water-blocking buffer layer near the main insulation layer.

[0036] Step 104: Inject repair fluid into the cable through the repair tank under pressure. The repair fluid has targeted induction and penetration properties.

[0037] Step 106: After sealing the repair groove, apply voltage to induce the repair fluid to diffuse toward the cable core to repair the defects in the main insulation layer.

[0038] It should be noted that, to avoid confusion between parameters and structural labels, no labels are used in this embodiment.

[0039] In this embodiment, the cable includes, from the inside out, a cable core, a main insulation layer, a water-blocking buffer layer, a metal sheath, and an outer sheath.

[0040] Specifically, the above method involves drilling holes from the outside of the cable inward to form a repair groove, and then injecting a repair fluid with targeted induction and penetration properties into the cable. Under the combined action of a specific electric field and a specific temperature, the dielectric induces the repair fluid to penetrate to the defect location of the main insulation layer to achieve localized and precise repair, which can effectively improve the construction efficiency and effectiveness of cable repair.

[0041] In this embodiment, when voltage is applied, the repair fluid injected into the cable from the outside in is within an electric field. At a specific temperature, the repair fluid can undergo dielectric movement to penetrate to the defect location of the main insulation layer.

[0042] Compared with existing technologies, the above method does not require the cable to be out of service, meaning that the repair can be performed in situ. The cable only needs to be de-energized during repair, significantly shortening the time required to restore the cable to a usable state. Furthermore, the pressurization area in this method is a localized area with defects in the main insulation layer, rather than the entire cable or a whole section of cable. Therefore, this pressurization repair method will not cause irreversible structural damage to old or micro-cracked areas of the cable. In this embodiment, step 106 is specifically implemented as follows:

[0043] Step 112: By applying an induction voltage with an effective value of 2kV~5kV and a frequency of 10 Hz~50Hz for 6h~10h, the repair fluid is induced to diffuse from the self-water-blocking buffer layer toward the cable core.

[0044] Alternatively, in step 114, by restoring the cable to its original power-on state, the repair fluid is induced to diffuse towards the cable core through the self-water-blocking buffer layer.

[0045] In this embodiment, the main insulation layer, from the outside to the inside (from the outer sheath to the cable core), includes an insulating shielding layer, a cross-linked polyethylene layer, and a conductor shielding layer in sequence. The penetration and diffusion direction of the repair liquid under dielectric action is from the insulating shielding layer toward the conductor shielding layer.

[0046] In this embodiment, step 112 (i.e., applying a specific induced voltage) allows the repair fluid injected into the cable from the outside in to penetrate and diffuse from the insulation shield layer to the conductor shield layer, thereby repairing defects in the main insulation layer. Alternatively, a high-voltage test can be conducted according to the normal power transmission method of the cable, and power can be transmitted after the test is passed.

[0047] In this embodiment, the above-mentioned repair fluid can be induced to diffuse in an electric field with a working frequency of 50Hz, or it can be induced to diffuse in an electric field under normal power supply to locally repair the main insulation layer of the cable.

[0048] In this embodiment, after the main insulation layer is partially repaired through step 112 above, power can be restored in situ to resume power transmission.

[0049] In this embodiment, the total amount of repair fluid injected into the repair tank is not less than 2L, and the injection time of the repair fluid is 10min~20min.

[0050] In this embodiment, the applied voltage is preferably a DC voltage.

[0051] The specific settings for the induction voltage holding time, induction voltage, repair fluid injection volume, and repair fluid injection time described above can further enhance the induced penetration and diffusion effect of the repair fluid.

[0052] In this embodiment, the repair solution comprises the following components by weight:

[0053] The main insulation layer repair component consists of 20 to 25 parts, the flowability modification component consists of 30 to 40 parts, the mixed stabilizer component consists of 0 to 5 parts, the catalyst consists of 3 to 5 parts, and the targeting inducer consists of 5 to 10 parts.

[0054] In this embodiment, the permeability characteristics of the repair fluid in the main insulation layer are improved by setting a fluidity-modifying component, i.e., fluidity. That is, under specific electric field and specific temperature conditions, the targeting inducer can induce the repair fluid to permeate and diffuse from the insulating shield layer to the conductor shield layer (i.e., provide the permeation and diffusion force of the repair fluid), while the aforementioned fluidity-modifying component can ensure that the repair fluid permeates and diffuses within the main insulation layer under dielectric force.

[0055] In this embodiment, the targeting inducer is one or a combination of at least two of the following in any mass ratio: 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and hexamethylphosphoric triamine.

[0056] In this embodiment, the main insulation layer repair component is methylphenyldimethoxysilane, and the flowability modification component is trimethylmethoxysilane.

[0057] In this embodiment, the content of the above-mentioned trimethylmethoxysilane in the repair solution is at least 30%. By setting no less than 30% of small molecule siloxanes, combined with the methylphenyldimethoxysilane component, the above-mentioned repair solution can effectively improve the penetration and diffusion ability of the repair solution while ensuring the repair of the main insulation layer, thereby improving the repair efficiency and avoiding the need for harsh electric field conditions during repair, thus having a higher prospect for practical application.

[0058] In this embodiment, the mixed stabilizer is at least one of dimethyldibutoxysilane, methyldimethoxyethylphenylsilane and cyanomethyldimethoxysilane or any combination of them in any mass ratio.

[0059] In this embodiment, the catalyst is one or at least two of the following in any mass ratio: titanium isopropoxide, titanium isopropoxy, titanium ethanol, titanium isopropoxide, titanium n-butoxide, titanium methanol, tetraisopropyl titanate, potassium hydroxide, and hydrochloric acid.

[0060] In this embodiment, the preparation method of the above-mentioned repairing agent is as follows:

[0061] The above-mentioned main insulation layer repair component, flowability modification component, mixed stabilizer component and targeting inducer are mixed in accordance with the weight fractions and mixed under inert gas.

[0062] After mixing, add the catalyst in parts by weight and mix again;

[0063] After adding the catalyst, the solution was allowed to stand for at least 30 minutes at room temperature and under vacuum in the dark to obtain the above-mentioned repair solution.

[0064] In this embodiment, the above mixing method is achieved by a stirring device with a stirring speed of 60 rpm to 240 rpm. The first mixing time is not less than 15 minutes, and the second mixing time is not less than 20 minutes. Both the first and second mixing are carried out at room temperature.

[0065] In this embodiment, the inert gas is preferably nitrogen.

[0066] In this embodiment, the components of the above-mentioned repair solution are exemplified as follows:

[0067] Example 1: The above-mentioned repair solution comprises the following components by weight:

[0068] 20 parts of main insulation layer repair component, 30 parts of flowability modification component, 3 parts of catalyst, and 5 parts of targeting inducer;

[0069] The targeting inducer is 2,4-dihydroxybenzophenone, the main insulating layer repair component is methylphenyldimethoxysilane, the flowability modification component is trimethylmethoxysilane, and the catalyst is titanium isopropoxide.

[0070] Example 2: The above-mentioned repair solution comprises the following components by weight:

[0071] The main insulation layer repair component consists of 25 parts, the flowability modification component consists of 40 parts, the mixed stabilizer component consists of 5 parts, the catalyst consists of 5 parts, and the targeting inducer consists of 10 parts.

[0072] The targeting inducers are 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone (mass percentage 1:1), the main insulating layer repair component is methylphenyldimethoxysilane, the flowability modification component is trimethylmethoxysilane, the catalyst is titanium isopropoxide and titanium isopropoxysilane (mass percentage 1:1), and the mixed stabilizer is dimethyldibutoxysilane.

[0073] Example 3: The above-mentioned repair solution comprises the following components by weight:

[0074] The composition includes 23 parts of main insulation layer repair component, 35 parts of flowability modification component, 3 parts of mixed stabilizer component, 4 parts of catalyst, and 8 parts of targeting inducer.

[0075] The targeting inducers are 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and hexamethylphosphoric triamine (mass percentage 1:1:1), the main insulating layer repair component is methylphenyldimethoxysilane, the flowability modifying component is trimethylmethoxysilane, the catalyst is titanium isopropoxide, titanium ethanolate, and titanium isopropoxide (mass percentage 1:1:1), and the mixed stabilizers are dimethyldibutoxysilane and methyldimethoxyethylphenylsilane.

[0076] The repair solutions prepared in Examples 1-3 above were used for multi-effect repair of cables. A 110kV power cable that had been decommissioned due to an accident after 16 years of operation was selected. Three 1.5-meter sections of cable with intact insulation were cut. Following the repair steps described above, a hole was drilled in the middle for repair. Injection was carried out at a pressure of 0.15 MPa for 30 minutes, followed by a 120-hour settling period. The performance of the repaired cable was then tested. The insulation resistance and dielectric loss of the three selected cable sections showed improvement. Further analysis of the diffusion of the main components of the repair solution in the main insulation of the repaired cable was conducted. The cable was cut approximately 0.5 meters from the injection hole, and infrared spectroscopy analysis revealed characteristic peaks of the siloxane component.

[0077] Please refer to Figure 4 and Figure 5 Based on the previous embodiment, another embodiment of this application provides a main insulation repair device for high-voltage power cables injected from the outside, which mainly includes a pressurizing device, a liquid storage device and an injection device connected in sequence. The liquid storage device is used to store repair liquid, and the pressurizing device can output a preset injection pressure to the liquid storage device.

[0078] The injection end of the injection device is located on the side wall of the repair tank 7 away from the outer sheath. The repair fluid stored in the liquid storage device can be injected into the cable through the injection device at a preset injection pressure.

[0079] In this embodiment, the repair groove can be prepared in conjunction with a drill bit limiter to ensure that the groove depth is the expected depth.

[0080] In this embodiment, the cable includes, from the inside out, a cable core 12, a main insulation layer 11, a water-blocking buffer layer 10, a metal sheath 9, and an outer sheath 8. The main insulation layer 11 includes, from the outside in (from the outer sheath to the cable core), an insulating shielding layer 111, a cross-linked polyethylene layer 112, and a conductor shielding layer 113.

[0081] In this embodiment, the injection device includes an injection nozzle 1. When injecting the repair fluid, the injection end of the injection nozzle 1 can be embedded in the water-blocking buffer layer 10 and can pass through the water-blocking buffer layer 10 at the bottom of the repair groove 7. It is located on the main insulation layer (i.e., on the side of the main insulation layer 11 close to the water-blocking buffer layer 10), specifically on the side of the insulating shield layer 111 close to the water-blocking buffer layer. The injection end of the injection nozzle 1 does not cause structural damage to the main insulation layer 11 (specifically the insulating shield layer 111).

[0082] In this embodiment, the liquid storage device is preferably a liquid storage tank 5. Similarly, a liquid storage tank with a pressure measuring component or a liquid storage tank with a flow rate control component can be selected according to actual application requirements.

[0083] In this embodiment, the pressurization device is preferably an air compressor 6, and the air compressor 6, the liquid storage tank 5, and the injection nozzle 1 are all connected by hoses.

[0084] In this embodiment, the above-mentioned device further includes a control valve 2, a flow meter 3, and a protection valve 4; the protection valve 4, the flow meter 3, and the control valve 2 are sequentially arranged on the connection link between the liquid storage device and the injection device, and the protection valve 4 is arranged on the connection link between the pressurizing device and the liquid storage device.

[0085] In this embodiment, the injection state of the repair fluid in the injection nozzle 1 can be controlled by setting the control valve 2, and the flow meter 3 can control the flow rate and velocity of the repair fluid.

[0086] In this embodiment, a pressure relief valve or a pressure regulating valve may be provided between the air compressor 6 and the liquid storage tank 5 to control the pressurization pressure in real time, and at the same time improve the safety performance of the device.

[0087] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of this application.

Claims

1. A method for repairing the main insulation of a high-voltage power cable via external injection, used to repair the cable, wherein the cable comprises, from the inside out, a cable core, a main insulation layer, a water-blocking buffer layer, a metal sheath, and an outer sheath, characterized in that, include: Repair grooves are provided in areas where the main insulation layer has defects. The repair grooves penetrate the outer sheath and the metal sheath in sequence. The sidewalls of the repair grooves away from the outer sheath are located in the water-blocking buffer layer near the main insulation layer. A repair fluid is injected into the cable through the repair groove under pressure. The repair fluid has targeted induction and penetration properties. After sealing the repair groove, voltage is applied to induce the repair fluid to diffuse from the water-blocking buffer layer toward the cable core to repair the defects in the main insulation layer.

2. The method for repairing the main insulation of high-voltage power cables via external injection according to claim 1, characterized in that, After sealing the repair groove, the process of inducing the repair fluid to diffuse towards the cable core by applying voltage to repair defects in the main insulation layer includes: By applying an induced voltage with an effective value of 2kV~5kV and a frequency of 10 Hz~50Hz for 6h~10h, the repair fluid is induced to diffuse from the water-blocking buffer layer toward the cable core. Alternatively, by restoring the cable to its original power-on state, the repair fluid can be induced to diffuse towards the cable core through the self-water-blocking buffer layer.

3. The method for repairing the main insulation of high-voltage power cables via external injection according to claim 1, characterized in that, The total amount of the repair solution injected into the repair tank shall not be less than 2L, and the injection time of the repair solution shall be 10min~20min.

4. The method for repairing the main insulation of high-voltage power cables via external injection according to claim 1, characterized in that, The repair solution comprises the following components by weight: The main insulation layer repair component consists of 20 to 25 parts, the flowability modification component consists of 30 to 40 parts, the mixed stabilizer component consists of 0 to 5 parts, the catalyst consists of 3 to 5 parts, and the targeting inducer consists of 5 to 10 parts.

5. The method for repairing the main insulation of high-voltage power cables via external injection according to claim 4, characterized in that, The targeting inducer is one or a combination of at least two of the following in any mass ratio: 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and hexamethylphosphoric triamine.

6. The method for repairing the main insulation of a high-voltage power cable via external injection according to claim 5, characterized in that, The main insulation layer repair component is methylphenyldimethoxysilane, and the flowability modification component is trimethylmethoxysilane.

7. The method for repairing the main insulation of high-voltage power cables via external injection according to claim 4, characterized in that, The mixed stabilizer is one or a combination of at least two of dimethyldibutoxysilane, methyldimethoxyethylphenylsilane and cyanomethyldimethoxysilane in any mass ratio.

8. The method for repairing the main insulation of a high-voltage power cable via external injection according to claim 4, characterized in that, The catalyst is one or at least two of the following in any mass ratio: titanium isopropoxide, titanium isopropoxy, titanium ethanol, titanium isopropoxide, titanium n-butoxide, titanium methyl methoxide, tetraisopropyl titanate, potassium hydroxide, and hydrochloric acid.

9. A device for repairing the main insulation of a high-voltage power cable via external injection, used to implement the method for repairing the main insulation of a high-voltage power cable via external injection as described in any one of claims 1-8, characterized in that, It includes a pressurizing device, a liquid storage device, and an injection device connected in sequence. The liquid storage device is used to store the repair fluid, and the pressurizing device can output a preset injection pressure to the liquid storage device. The injection end of the injection device is located on the side wall of the repair tank away from the outer sheath, and the repair fluid stored in the liquid storage device can be injected into the cable through the injection device at a preset injection pressure.

10. The high-voltage power cable main insulation repair device via external injection according to claim 9, characterized in that, It also includes a control valve, a flow meter, and a protection valve; the protection valve, the flow meter, and the control valve are sequentially arranged on the connection link between the liquid storage device and the injection device, and the protection valve is arranged on the connection link between the pressurizing device and the liquid storage device.

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