Socket protection device of voltage-withstanding compensation type underwater wet-plugging electric connector

Abstract

The invention relates to a pressure-resistant compensation type underwater wet-plugging electric connector socket protection device which comprises a front shell, an outer-layer oil bag and an insulator are arranged in the front shell, the periphery of the insulator is matched and sealed with the front shell, and the front end of the insulator is matched and sealed with the rear end of the outer-layer oil bag; the oil-filled pressure-balanced jack is used for being adaptively plugged with a pin of a protected socket and is positioned and assembled in the insulator, the front end of the oil-filled pressure-balanced jack is positioned in the outer-layer oil bag, and the rear end of the oil-filled pressure-balanced jack extends out of the tail part of the insulator; the front end of the straight sleeve is open and the tail is closed; the front end of the straight sleeve is hermetically connected with the tail part of the front shell, and balance oil is injected into a cavity; the two ends of the inclined sleeve are open, the front end of the inclined sleeve is connected with the straight sleeve in a sealed mode, and a piston is arranged in the inclined sleeve in a sealed mode and can do reciprocating motion under the action of balance oil in the straight sleeve and external water pressure. The pressure-resistant compensation type underwater wet-plugging electric connector socket protection device not only can protect the contact pin of the wet-plugging electric connector socket, but also can meet the pressure requirement brought by a deep sea environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wet plug connectors, and particularly relates to a pressure-resistant compensation type underwater wet plug electrical connector socket protection device. BACKGROUND

[0002] The wet plug electrical connector is mainly applied to underwater production control systems, observation networks, FPSO oil well intervention riser system equipment and the like, and is a key connection component of deep sea equipment. When working, the plug and socket of the electrical connector are plugged to realize power transmission, and after being unplugged, the pins of the electrical connector are directly exposed to seawater. If no protection is provided, challenges such as seawater corrosion, silt intrusion and marine organism attachment will be faced, leading to pin rusting and further affecting the plug force and electrical performance of the electrical connector. SUMMARY

[0003] To solve the above problems, the application provides a pressure-resistant compensation type underwater wet plug electrical connector socket protection device, which can not only be adapted to the wet plug electrical connector socket and plugged to provide reliable protection for the electrical connector socket, but also can keep the balance of the internal and external pressures of the front and rear cavities of the protection device by setting an oil injection cavity at the tail and a device for keeping the pressure balance of the cavity.

[0004] The application is achieved by the following technical scheme. The pressure-resistant compensation type underwater wet plug electrical connector socket protection device according to the application comprises a front shell body 1, the front end of the front shell body 1 is used for being adapted to and plugged with a protected socket, and a plurality of through holes communicating the inside and outside are arranged on the circumference of the front shell body 1. An outer oil bag 2 is arranged in the front shell body 1, and the outer oil bag 2 is filled with balance oil. An insulator 7 is further arranged in the front shell body 1, the outer circumference of the insulator 7 is sealed with the front shell body 1, the front end of the insulator 7 is sealed with the outer oil bag 2, a charge oil pressure balance type jack 12 is used for being adapted to and plugged with the pins of the protected socket, the charge oil pressure balance type jack 12 is positioned and assembled in the insulator 7, the front end of the charge oil pressure balance type jack 12 is located in the outer oil bag 2, and the rear end of the charge oil pressure balance type jack 12 is extended from the tail of the insulator 7. A straight sleeve 3 is arranged, the front end of the straight sleeve 3 is open, and the tail of the straight sleeve 3 is closed. The front end of the straight sleeve 3 is sealingly connected with the tail of the front shell body 1. Balance oil is injected into the cavity surrounded by the straight sleeve 3, the insulator 7 and the front shell body 1. An inclined sleeve 4 is arranged, the two ends of the inclined sleeve 4 are open, the front end of the inclined sleeve 4 is sealingly connected with the straight sleeve 3 and communicates with the cavity in the straight sleeve 3. A piston 6 is sealingly arranged in the inclined sleeve 4, and the piston 6 can reciprocate under the action of the balance oil in the straight sleeve 3 and the external water pressure.

[0005] The application is further achieved by the following technical measures.

[0006] The aforementioned pressure-compensated underwater wet-plugging electrical connector socket protection device also includes an end cap 5 at the tail of the inclined sleeve 4, which prevents the piston 6 from being pressed out of the inclined sleeve 4; the end cap 5 is provided with several small holes for fluid to enter and exit.

[0007] The aforementioned pressure-compensated underwater wet-plugging electrical connector socket protection device also includes an inner step 41 on the inner side of the front end of the inclined sleeve 4 to prevent the piston 6 from being squeezed into the straight sleeve 3.

[0008] In the aforementioned pressure-compensated underwater wet-plugging electrical connector socket protection device, the piston 6 maintains a seal with the inner wall of the inclined sleeve 4 within its sliding stroke through at least one raised rib on its outer periphery or at least one sealing ring in its outer periphery groove.

[0009] In the aforementioned pressure-compensated underwater wet-plugging electrical connector socket protection device, the inclined sleeve 4 and the straight sleeve 3 are welded, threaded, or integrally formed by machining. In the aforementioned pressure-compensated underwater wet-plugging electrical connector socket protection device, the straight sleeve 3 is provided with an oil injection hole for injecting oil into its cavity, and this oil injection hole is sealed by a sealing screw 31.

[0010] The aforementioned pressure-compensated underwater wet-plug electrical connector socket protection device also has at least two axially extending locking arms 15 on the outer periphery of the front housing 1, which are locked in place by locking hooks on the locking arms 15 in conjunction with the protected socket.

[0011] The aforementioned pressure-compensated underwater wet-plug electrical connector socket protection device also includes a housing 17, which is fitted around the outer periphery of the front housing 1 and can drive the front housing 1 to move axially; the housing 17 has an opening in the circumference that connects the inside and outside of the cavity; the front end of the housing 17 has a guide structure for guiding the protected socket into the cavity; and the rear end of the housing 17 has a handle 19 for easy application of force.

[0012] The aforementioned pressure-compensated underwater wet-plug electrical connector socket protection device has a guiding structure that is a mating guide sleeve 18 fixed to the front end of the housing 17. The inner circumference of the mating guide sleeve is a tapered surface that tapers from front to back in terms of radial dimensions.

[0013] In the aforementioned pressure-compensated underwater wet-plug electrical connector socket protection device, the portion of the oil-filled pressure-balanced socket 12 extending out of the insulator 7 is protected by an insulating cap 1241 or by a short-circuiting wire 16. When the short-circuiting wire is used, the protection device can be used as a test head.

[0014] Compared with existing technologies, this invention has significant advantages and beneficial effects. Through the above technical solution, this invention achieves considerable technological advancement and practicality, and has broad industrial application value, possessing at least the following advantages:

[0015] The socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector can not only protect the pins of the wet-plug electrical connector socket, but also meet the pressure requirement brought by deep sea environment.

[0016] The front-end cavity of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector is balanced with oil bag, and the rear-end cavity is balanced with oil filling, increased inclined sleeve and piston, and the volume expansion and shrinkage behavior of silicone oil caused by temperature change is compensated, so that the front and rear cavities of the device can keep the internal and external pressure balance, the front and rear ends of the oil-filled pressure balance type jack are located in the cavity balanced with internal and external pressure, and the reliability of the protection device in high pressure environment is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a partial sectional view of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector;

[0018] Figure 2 is a sectional view of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector;

[0019] Figure 3 is a partial sectional view of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector;

[0020] Figure 4 is a schematic view of the piston structure of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector

[0021] Figure 5 is another schematic view of the piston structure of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector;

[0022] Figure 6 is still another schematic view of the piston structure of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector;

[0023] Figure 7 is a schematic view of the end cover structure of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector;

[0024] Figure 8 is a schematic view of the socket protection device of the pressure-resistant compensation type underwater wet-plug electrical connector as a test head.

[0025]

MAIN ELEMENT SYMBOL EXPLANATION

[0026] 1: front shell; 2: outer oil bladder; 3: straight sleeve; 4: inclined sleeve; 5: end cover; 6: piston; 7: insulator; 8: bushing; 9: inner oil bladder; 10: first sealing ring; 11: fastening screw; 12: oil-filling pressure balance type socket; 13: insulating pressing plate; 14: check ring; 15: locking arm; 16: short-circuiting wire; 17: outer shell; 18: plug-in guide sleeve; 19: handle. DETAILED DESCRIPTION

[0027] In order to further illustrate the technical means and effects taken by the present application to achieve the predetermined object, the specific implementation, structure, features and effects of the pressure-compensated underwater wet-plug electrical connector socket protection device according to the present application are described in detail as follows in combination with the drawings and preferred embodiments.

[0028] Referring to Figures 1-4 which is a schematic diagram of the structure of each part of the pressure-compensated underwater wet-plug electrical connector socket protection device according to the present application. The protection device comprises a front shell 1, the front end of which is used to adapt to the front end of the protected socket for plugging. A plurality of through holes are provided on the front shell 1 to allow external seawater to enter the front shell 1 through the through holes. The front shell 1 has a cavity extending in the axial direction and open at both ends. The tail part of the front shell 1 is connected and fixed with a straight sleeve 3, the tail part of which is closed and the front end of which is open. The straight sleeve 3 and the front shell 1 are further sealed by cooperating with a first sealing ring 10. Preferably, the first sealing ring 10 has a plurality of first sealing rings 10, each of which is positioned and assembled in the annular groove on the outer periphery of the front shell 1.

[0029] In this embodiment, the straight sleeve 3 is connected and fixed with the tail part of the outer periphery of the front shell 1 by a fastening screw 11. Specifically, a plurality of through holes extending in the radial direction are provided on the outer periphery of the front end of the straight sleeve 3, and the outer periphery of the front shell 1 is provided with corresponding screw holes, which are blind holes.

[0030] An insulator 7 is assembled in the tail part cavity of the outer shell 1, which is sealed and cooperated with the outer shell 1 to separate the front end cavity of the outer shell 1 from the cavity of the straight sleeve 3. An outer oil bladder 2 is provided in the front end cavity of the outer shell 1, which forms an oil-filling cavity. The protection device further comprises an oil-filling pressure balance type socket 12, the front end of which is located in the oil-filling cavity formed by the outer oil bladder 2, and the rear end of which penetrates through the corresponding hole position on the insulator 7 and enters the front end cavity of the straight sleeve 3. The outer periphery of the oil-filling pressure balance type socket 12 and the insulator 7 are further sealed by cooperating with a sealing element.

[0031] The closed cavity formed between the straight sleeve 3, the outer shell 1 and the insulator 7 is filled with oil to prevent air in the closed cavity from being compressed and causing pressure imbalance between the inside and outside of the cavity, thus resulting in failure of the protection device. The straight sleeve 3 is provided with an oil injection hole for injecting oil into the cavity thereof, preferably, the oil injection hole is a threaded hole provided on the tail end surface of the straight sleeve 3 and penetrating through the tail end surface of the straight sleeve, and a sealing screw 31 screwed in the oil injection hole is used to block the oil injection hole. The sealing screw 31 and the oil injection hole are also sealed by a sealing member.

[0032] The straight sleeve 3 is also connected with a slant sleeve 4, the slant sleeve 4 is open at both ends, the front end of the slant sleeve 4 communicates with the inner cavity of the straight sleeve 3, and the slant sleeve 4 is also provided with a piston 6, the outer periphery of the piston 6 is sealed with the inner wall of the slant sleeve 4 and can reciprocate in the slant sleeve 4, so that the oil pressure in the straight sleeve 3 and the external water pressure are kept balanced. Preferably, the straight sleeve 3 and the slant sleeve 4 are integrally connected by welding, but in other embodiments, the straight sleeve 3 and the slant sleeve 4 can also be integrally connected by screwing or other means and sealed by a sealing member; the straight sleeve 3 and the slant sleeve 4 can also be integrally formed by machining.

[0033] In this embodiment, the oil in the straight sleeve 3 is silicone oil, which is more sensitive to temperature change than pressure, and the change of temperature will affect the volume of silicone oil, when the temperature rises, the silicone oil will expand, thus pushing the piston 6 to move backward (away from the straight sleeve), when the temperature decreases, the silicone oil shrinks, and the piston 6 will move forward (toward the straight sleeve), under the action of external seawater pressure, the cavity inside the straight sleeve 3 is always in a state of pressure balance.

[0034] Please refer to Figure 4 In this embodiment, the piston 6 is in interference fit with the inner wall of the slant sleeve 4 through the outer circumferential convex rib structure to realize sliding sealing, and the outer periphery of the piston 6 has a plurality of convex ribs 61 distributed along the axial direction and extending along the circumferential direction.

[0035] Please refer to Figure 5 In another embodiment of the present application, the outer periphery of the piston 6 is provided with a ring groove 62, and a sealing ring 63 is arranged in the ring groove 62 to realize the sealing between the piston 6 and the slant sleeve 4.

[0036] Please refer to Figure 6 In still another embodiment of the present application, a plurality of ring grooves 62 are arranged on the outer periphery of the piston 6 along the axial direction, and a sealing ring 63 is arranged in each ring groove 62 to realize the sealing between the piston 6 and the slant sleeve 4 at multiple positions. Preferably, the sealing ring 63 is an O-ring, but it is not limited thereto.

[0037] The piston 6 can be made of metal material or rubber material.

[0038] In the embodiment of the present application, the oblique sleeve 4 is further provided with a stop limiting structure for limiting the reciprocating stroke of the piston 6, preventing the piston 6 from moving forward into the cavity of the straight sleeve 3 or moving backward out of the oblique sleeve 4. In this embodiment, the front end of the oblique sleeve 4 is provided with an inner step 41, which stops and limits the forward movement of the piston 6, preventing it from being squeezed into the cavity of the straight sleeve 3. The tail of the oblique sleeve 4 is provided with an end cover 5, which stops the backward movement of the piston 6, preventing it from being pressed out of the oblique sleeve 4. The end cover 5 is further provided with water inlet and outlet holes 51 for the external liquid to enter and exit the oblique sleeve 4. Preferably, the end cover 5 is locked with the threads on the inner periphery of the tail of the oblique sleeve 4 through threads.

[0039] Please refer to Figure 7 In this embodiment, the end face of the end cover 5 is provided with a plurality of small holes, each of which is a water inlet and outlet hole 51. The water inlet and outlet hole 51 can filter the water entering the oblique sleeve 4, allowing only seawater to enter and avoiding larger sand particles from entering. In deep water environment, seawater can enter the oblique sleeve 7 through the plurality of water inlet and outlet holes 5 on the end cover 5, thereby directly applying water pressure on the outer end face of the piston 6. Preferably, the tail end face of the end cover 5 is further provided with a one-word slot 52 for easy installation, disassembly and force application.

[0040] The outer periphery of the front end of the outer oil bladder 2 is further provided with a bushing 8, the front end face of which is axially stopped and limited by the retaining ring 1 on the inner wall of the front housing 1, and the outer periphery of which is radially limited by the inner wall of the front housing 1. The front end of the outer oil bladder 2 is further provided with an insulating pressing plate 13, which provides radial support for the outer oil bladder 2. The front end face of the outer oil bladder 2 is provided with a plurality of first hole positions 21, and the insulating pressing plate 13 is provided with a second hole position 131 adapted to the first hole position 21. The front end of the oil pressure charging and balancing type jack 12 passes through the second hole position 131 and the first hole position 21 from back to front, and maintains contact sealing with the first hole position 21 or / and the second hole position 131. In this embodiment, the inner periphery of the first hole position 21 and the second hole position 131 is provided with at least one convex rib, which realizes the cooperation and sealing with the oil pressure charging and balancing type jack 12.

[0041] In this embodiment, the front end of the first hole position 21 is in the shape of a horn, with the radial size gradually increasing from back to front, so as to guide the pins of the protected socket into the oil pressure charging and balancing type jack 12.

[0042] In this embodiment, the front end of the insulating pressboard 13 is provided with a protrusion 132 at each second hole site 131. Preferably, multiple protrusions 132 are provided at each second hole site 131, and the multiple protrusions are distributed in a circumferential or annular array around the second hole site 131. The face of the outer oil pocket 2 facing the front end of the insulating pressboard 13 is provided with a groove matching the protrusion 132. The insulating pressboard 13 and the outer oil pocket 2 are reliably positioned by the cooperation of the protrusion and the groove, so as to ensure that the corresponding first hole site 21 and the second hole site 131 can be coaxial and prevent radial deviation therebetween.

[0043] The oil-filled pressure balance jack 12 comprises a sleeve 121, an inner oil pocket 122, a movable top rod 123, a connecting rod 124, and an elastic member 125. The inner oil pocket 122 is sleeved on the sleeve 121, and the front end of the inner oil pocket 122 is inserted into the groove in the rear end of the insulating pressboard 13, and is axially and radially limited by the groove. The groove is in communication with the corresponding second hole site 131. The gap 1222 between the inner oil pocket 122 and the sleeve 121 is filled with pressure balance oil. The sleeve 121 is further provided with a slot 1211 for connecting the gap 1222 and the inner space of the jack contact 121, so as to realize the flow of oil in the two spaces.

[0044] The movable top rod 123 is slidably arranged in the sleeve 121 in the front-rear direction. The connecting rod 124 is connected to the rear end of the sleeve 121, and is positioned and assembled in the insulating body 7, and the tail portion penetrates the insulating body 7 into the cavity of the straight sleeve 3. The elastic member 125 is further provided between the movable top rod 123 and the connecting rod 124. The elastic member 125 provides a forward thrust to the movable top rod 123, so as to close the first hole site 21 and the second hole site 131 when the protection device is not combined with the socket to be protected, thereby preventing external liquid from entering the inner oil pocket. The outer wall of the movable top rod 123 is provided with a circumferentially extending flange 1231, which is axially stopped and cooperated with the limiting platform arranged on the inner wall of the jack contact 121, so as to prevent the movable top rod 123 from being pulled out of the sleeve 121.

[0045] The rear end of the outer oil pocket 2 is sealingly cooperated with the front end of the insulating body 7. Specifically, the rear end of the outer oil pocket 2 has a sealing boss, and the outer periphery of the insulating body 7 is provided with a sealing ring groove. The sealing boss is embedded in the sealing ring groove to form an interference seal.

[0046] In the embodiment, the sleeve 121 and the connecting rod 124 are conductors, and the tail of the connecting rod 124 is sleeved with an insulating cap 1241. The inner part of the front end of the sleeve 121 is further provided with an elastic inner sleeve 126 which is in elastic contact with the element and is used for elastic contact and conduction with the pin of the socket to be protected. The elastic contact element can be a wire spring hole, a crown spring, etc. to improve the contact stability of the pin and the sleeve 121. Preferably, the front end of the sleeve 121 is further provided with an outer sleeve 127 which is sleeved on the elastic contact element, the outer sleeve 127 is used for radially supporting the inner layer oil bag 122, maintaining the shape of the front end opening of the inner layer oil bag 122, avoiding the diameter of the front end opening of the inner layer oil bag from becoming smaller, and the front end opening of the inner layer oil bag 122 is in sealed sliding fit with the movable top rod 123. At this time, the protection device can also short-circuit the tails of different connecting rods 124 through the short-circuiting wire 16. After the short-circuiting socket and the socket pin are inserted, a loop can be formed. At this time, the protection device can be used as a test head for testing the performance of the socket. Please refer to Figure 8 In other embodiments of the application, the oil-filled pressure balance type socket 12 can be made of non-conductive materials. At this time, the protection device is only used for protection.

[0047] In the embodiment of the application, at least two locking arms 15 are further fixed on the outer periphery of the front shell 1. The locking arms 15 can be locked with the socket to be protected through the clamps on the inner side of the front end.

[0048] In the embodiment of the application, the insulator 7 is further provided with an oil injection hole which is in communication with the outer layer oil bag and the inner cavity of the straight sleeve. The outer layer oil bag can be injected with oil through the oil injection hole. The oil injection hole is sealed with a sealing plug.

[0049] The outer shell 17 is further sleeved on the outer periphery of the front shell 1. The outer shell 17 is provided with a long hole for communicating the internal cavity with the outside. The tail of the outer shell 17 is fixed with a handle 19, and the front end is provided with an insertion guide sleeve 18. The inner diameter of the insertion guide sleeve 18 is in a tapered structure which gradually shrinks from front to back, which is used for guiding the socket to be protected into the outer shell 17. In the embodiment, the insertion guide sleeve 18 is made of plastic material, and can also play a role in anti-collision protection when the protection device is inserted with the socket to be protected.

[0050] The above is only the preferred embodiment of the application, and does not limit the application in any form. Although the application has been disclosed as above with the preferred embodiment, it is not intended to limit the application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the application, and any simple modification, equivalent change and modification of the above embodiment based on the technical essence of the application are still within the scope of the technical solution of the application.

Claims

1. A pressure-compensating underwater wet-mate electrical connector receptacle guard, characterized by: The front shell is used to be inserted into the protected socket, and a plurality of through holes are arranged on the circumference of the front shell for communication between the inside and outside; an outer oil bag and an insulator are arranged in the front shell, and the outer circumference of the insulator is sealed with the front shell, and the front end is sealed with the rear end of the outer oil bag; the outer oil bag is filled with balance oil; The oil-filled pressure balance plug is used to be inserted into the pin of the protected socket; the plug is positioned and assembled in the insulator, and the front end is located in the outer oil bag, and the rear end is extended from the tail of the insulator; The straight sleeve is open at the front end and closed at the tail; the front end of the straight sleeve is sealed and connected with the tail of the front shell; the cavity surrounded by the straight sleeve, the insulator and the front shell is filled with balance oil; The oblique sleeve is open at both ends, and the front end is sealed and connected with the straight sleeve and communicates with the cavity in the straight sleeve; the piston is arranged in the oblique sleeve and can reciprocate under the action of balance oil and external water pressure in the straight sleeve.

2. The pressure-compensated underwater wet-mate electrical connector receptacle guard of claim 1, wherein: The tail of the oblique sleeve is also provided with an end cap, which can prevent the piston from being pressed out of the oblique sleeve; a plurality of small holes are arranged on the end cap for fluid inlet and outlet.

3. The pressure-compensated underwater wet-mate electrical connector receptacle guard of claim 2, wherein: The inner side of the front end of the oblique sleeve is also provided with an inner step for preventing the piston from being extruded into the straight sleeve.

4. The pressure-compensated underwater wet-mate electrical connector receptacle guard of any of claims 1-3, wherein: The piston is sealed with the inner wall of the oblique sleeve through at least one convex rib on the outer circumference or at least one sealing ring in the ring groove on the outer circumference in the sliding stroke.

5. The pressure rated, compensation type, underwater, wet mateable electrical connector receptacle guard of claim 4, wherein: The oblique sleeve and the straight sleeve are welded, fixed by threads or integrally formed by machining.

6. The pressure rated, compensation type, underwater, wet mateable electrical connector receptacle guard of claim 1, wherein: The straight sleeve is provided with an oil injection hole for injecting oil into the cavity, and the oil injection hole is blocked by a sealing screw.

7. The pressure rated, compensation type, underwater wet mateable electrical connector receptacle guard of claim 1, wherein: The outer circumference of the front shell is also provided with at least two locking arms extending in the axial direction, and the locking arms are locked with the protected socket through the locking hooks on the locking arms.

8. The pressure equalizing underwater wet mateable electrical connector receptacle shield of any of claims 1-3, 5-7, further comprising: The outer shell is sleeved on the outer circumference of the front shell and can drive the front shell to move axially; the outer shell is circumferentially provided with an opening for communication between the cavity and the outside; the front end of the outer shell has a guide structure for guiding the protected socket to enter; the tail of the outer shell is provided with a handle for easy force application.

9. The pressure rated, compensation type, underwater wet mateable electrical connector receptacle guard of claim 8, wherein: The guide structure is an insertion guide sleeve fixed on the front end of the outer shell, and the inner circumference of the insertion guide sleeve is a tapered surface with a contraction from front to back.

10. The pressure equalizing underwater wet mateable electrical connector receptacle guard of any of claims 1-3, 5-7, 9, further comprising: The part of the oil-filled pressure balance plug extending out of the insulator is protected by an insulating cap or short-circuited by a short-circuit wire, and when the short-circuit wire is used, the protection device can be used as a test head.

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