Device for testing dielectric strength of insulating oil

Abstract

The utility model belongs to the technical field of insulating oil detection, and discloses an insulating oil dielectric strength testing device which comprises a rack and a detection assembly arranged in the rack, and the detection assembly comprises a sealing vessel used for containing insulating oil and a detection unit used for dielectric strength detection; the motor is arranged on the rack; the clamping arm is used for clamping a vessel, and the clamping arm is fixedly connected with the output end of the motor; the air inlet valve is communicated with the vessel through a pipeline; the exhaust valve is communicated with the vessel through a pipeline; the nitrogen cylinder is communicated with the air inlet valve through a pipeline; according to the scheme, insulating oil is introduced into the vessel in an inclined mode, air in the vessel is replaced, the oxidation influence of oxygen and moisture on oil quality is reduced, and therefore abnormal discharge and data deviation caused by bubbles are reduced; the utility model solves the problem that the existing dielectric strength vessel is easy to cause bubbles to be mixed into the insulating oil.

Description

TECHNICAL FIELD

[0001] The present scheme belongs to the technical field of insulating oil detection, and particularly relates to an insulating oil dielectric strength testing device. BACKGROUND

[0002] Insulating oil is a kind of liquid insulating material used in power equipment (such as transformers, circuit breakers, etc.), which mainly functions to provide electrical insulation, heat dissipation and cooling, and arc extinguishing.

[0003] The insulating oil in the transformer needs to be tested for dielectric strength, which is a key indicator for measuring whether the insulating oil can withstand high voltage without breakdown under the action of an electric field. By testing the dielectric strength, the purity and performance of the insulating oil can be evaluated to ensure that it can effectively prevent arc and corona phenomena, thereby ensuring the safe operation of the transformer.

[0004] Referring to the document with the publication (announcement) number CN106093740A, an automatic constant temperature type insulating oil dielectric strength tester is disclosed, which includes a container device for containing insulating oil, a temperature control heating device arranged below the container device, and an electric control system; the container device includes a glassware for containing insulating oil and a center concave table arranged at the bottom of the glassware and protruding upward; a stirring paddle is arranged in the glassware on the sealing upper cover, and a circular baffle is arranged on the stirring shaft of the stirring paddle, which is above the stirring paddle.

[0005] The above tester makes the insulating oil uniformly heated by arranging the stirring paddle, and prevents the insulating oil from shaking and air from mixing into the insulating oil by the baffle. However, before the insulating oil is put into the glassware, there is air in the glassware. When the insulating oil contacts the glassware, due to the surface tension at the interface between the liquid and the air, the liquid will form air bubbles when entering the container. At the same time, due to the viscosity of the insulating oil itself, the liquid with high viscosity is more likely to wrap air during the flow process, forming air bubbles. When there are air bubbles in the insulating oil, since the dielectric strength of the air bubble is much lower than that of the insulating oil itself (the breakdown voltage of air is only 3 kV / mm, while the breakdown voltage of pure insulating oil can reach more than 60 kV / mm), in a high voltage electric field, the air bubble will ionize first and form a local discharge channel, resulting in a significant reduction in breakdown voltage and deviation in the dielectric strength test result. CONTENT OF THE UTILITY MODEL

[0006] The purpose of the present scheme is to provide an insulating oil dielectric strength testing device to solve the problem that the existing dielectric strength container easily causes air bubbles to mix into the insulating oil.

[0007] In order to achieve the above object, the scheme provides an insulating oil dielectric strength testing device, which comprises a rack and a detection assembly arranged in the rack, the detection assembly comprises a sealed container for containing insulating oil and a detection unit for dielectric strength detection; further comprising:

[0008] a motor arranged on the rack;

[0009] a clamping arm for clamping the container, the clamping arm being fixedly connected with the output end of the motor;

[0010] an air inlet valve communicated with the container through a pipeline;

[0011] an air outlet valve communicated with the container through a pipeline;

[0012] a nitrogen cylinder communicated with the air inlet valve through a pipeline.

[0013] The principle and effect of the scheme are that the motor drives the clamping arm to tilt the container by a certain angle, so that the insulating oil forms a liquid level gradient under the action of gravity, accelerates the internal bubbles to gather to the high position of the liquid level and float to the top of the container during the tilting movement, and high-purity nitrogen (≥99.99%) is injected into the container through the nitrogen cylinder, the residual air is gradually replaced and discharged from the container by using the characteristic that the density of nitrogen is higher than that of air, the bubbles formed by the surface tension or viscosity when the oil liquid contacts the container wall are eliminated, and the oxidation influence of oxygen and moisture on the oil quality is reduced, so as to reduce the abnormal discharge and data deviation caused by bubbles.

[0014] Further, the stirring assembly comprises a gas storage chamber, a fan blade and a stirring rod; the gas storage chamber is fixedly arranged in the inner wall of the top cover of the container, the gas storage chamber is provided with an air inlet and an air outlet, the air inlet is communicated with the nitrogen cylinder through a pipeline, one end of the rotating shaft of the fan blade is rotatably connected with the air outlet, and the free end of the rotating shaft of the fan blade is fixedly connected with the stirring rod.

[0015] The principle and effect of the scheme are that before the insulating oil is introduced into the container, the nitrogen cylinder fills nitrogen into the gas storage chamber through the air inlet, and the nitrogen is sprayed out through the air outlet, so as to drive the fan blade to rotate, the fan blade drives the stirring rod to rotate, the nitrogen is uniformly distributed in the container, and the nitrogen forms a vortex in the container, so as to accelerate the discharge of residual air in the container.

[0016] Further, a piston is slidably arranged in the gas storage chamber, the piston is connected with a spring, the free end of the spring is connected with the gas storage chamber, and the piston is arranged at the rear end of the air inlet.

[0017] The principle and effect of the scheme are that after nitrogen is filled into the gas storage chamber, the gas pushes the piston to move in the gas storage chamber and stretch the spring, so that the space of the gas storage chamber is increased, and a part of nitrogen is temporarily stored in the gas storage chamber in the process of continuously filling nitrogen. After the insulating oil is introduced into the vessel, the nitrogen cylinder stops delivering nitrogen to the vessel. Since there are originally bubbles in the insulating oil, at this time, the piston in the gas storage chamber is reset to the initial state under the driving of the spring pre-tightening force, so as to squeeze the pre-stored nitrogen in the gas storage chamber to the vessel through the gas outlet, and drive the fan blade to continue to rotate, so that the stirring rod stirs the insulating oil, generates vortex flow, makes the bubbles smaller and more dispersed, which helps the bubbles to float to the oil surface more quickly and accelerates the breaking of the bubbles.

[0018] Further, the defoaming assembly further comprises a driving chamber, the driving chamber is arranged at the bottom of the gas storage chamber, the driving chamber is communicated with the gas storage chamber through the gas outlet, and the driving chamber is provided with an exhaust port; the fan blade is arranged in the driving chamber, the stirring rod comprises a supporting rod, a movable rod and a cross rod, one end of the supporting rod is fixedly connected with the rotating shaft of the fan blade, the supporting rod is arranged in the inner wall of the movable rod, the movable rod passes through the driving chamber, one end of the movable rod arranged in the driving chamber is connected with a pressing plate, one end of the cross rod is fixedly connected with the free end of the movable rod, and the movable rod and the cross rod are made of a material with a density lower than that of the insulating oil.

[0019] The principle and effect of the scheme are that when the nitrogen cylinder fills nitrogen into the gas storage chamber and the piston squeezes the gas storage chamber, both of them make the gas act on the pressing plate, so as to press the pressing plate downward, so that the movable rod extends and drives the cross rod in the insulating oil, and under the driving of the fan blade, the cross rod stirs the insulating oil, so that the bubbles float to the oil surface. After the nitrogen cylinder stops filling nitrogen into the gas storage chamber and the piston is reset to the initial position, the pressing plate loses the external force, and since the movable rod and the cross rod are made of a material with a density lower than that of the insulating oil, the cross rod floats to the oil surface.

[0020] Further, at least part of the movable rod and the cross rod is arranged as a hollow structure, so that the overall density of the movable rod and the cross rod is lower than that of the insulating oil and floats on the liquid surface; the outer surfaces of the movable rod and the cross rod are provided with an oil-repellent coating.

[0021] The principle and effect of the scheme are that through the above arrangement, the cross rod can float to the oil surface of the insulating oil after the pressing plate loses the external force.

[0022] Further, the defoaming assembly further comprises a vacuum pump, the vacuum pump is communicated with the gas inlet through a pipeline.

[0023] The principle and effect of the scheme are that: in order to make the bubbles in the insulating oil be eliminated as soon as possible, the pressure of the vessel is reduced to 5-10 mbar through the vacuum pump, so that the external pressure on the bubbles in the insulating oil is reduced, thereby the bubbles rapidly expand and float to the oil surface.

[0024] Further, the crossbar is a hollow structure, the crossbar is communicated with the vacuum pump through a pipeline, the free end of the crossbar is a wedge-shaped through hole, the crossbar is provided with a sealing ball for sealing the wedge-shaped through hole, the sealing ball is connected with a return spring, and the free end of the return spring is fixedly connected with the crossbar.

[0025] The principle and effect of the scheme are that: when the crossbar floats on the oil surface, the pipeline connected with the vacuum pump is communicated, under the action of suction, the sealing ball is away from the wedge-shaped through hole and compresses the return spring, so that the micro bubbles on the oil surface are sucked away through the crossbar. Then the vacuum pump is closed, the return spring drives the sealing ball to abut against the sealing wedge-shaped through hole. Finally, nitrogen is continuously introduced into the vessel at a low flow rate again, so that the crossbar is in the insulating oil, and dielectric detection is carried out, and the insulating oil is continuously stirred, which is beneficial to heating and avoids oil stratification.

[0026] Further, the inner wall of the movable rod is slidably connected with the outer wall of the supporting rod; and the driving chamber is provided with a sliding groove, and the pressing plate is slidably connected with the sliding groove.

[0027] The principle and effect of the scheme are that: the movable rod and the supporting rod slide, the movable rod can be retracted outside the supporting rod, so that the movable rod drives the crossbar to move to the oil surface; and the sliding groove is used for positioning and guiding the movement of the pressing plate.

[0028] Further, a first one-way valve is arranged on the pipeline connected with the gas inlet of the nitrogen cylinder; and a second one-way valve is arranged on the pipeline connected with the gas inlet of the vacuum pump.

[0029] The principle and effect of the scheme are that: the one-way valves are arranged, so that the gas in the pipeline flows in a preset direction.

[0030] Further, a limiting block is arranged in the gas storage chamber, and the limiting block is arranged at the upper end of the gas inlet.

[0031] The principle and effect of the scheme are that: the limiting block is used for limiting the limit position of the piston reset, so as to avoid that the piston moves below the gas inlet, thereby causing that the nitrogen cannot send the gas into the vessel through the gas inlet, and the vacuum pump cannot draw the vessel to negative pressure through the gas inlet. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structural schematic view of the insulating oil dielectric strength testing device.

[0033] Figure 2This is a schematic diagram of the internal structure of the vessel of this utility model;

[0034] Figure 3 This is a schematic diagram of the internal structure of the stirring assembly and defoaming assembly of this utility model. Figure 1 ;

[0035] Figure 4 This is a schematic diagram of the internal structure of the stirring assembly and defoaming assembly of this utility model. Figure 2 ;

[0036] Figure 5 This is a schematic diagram of the internal structure of the stirring assembly and defoaming assembly of this utility model. Figure 3 ;

[0037] Figure 6 This is a schematic diagram of the internal structure of the free end of the crossbar of this utility model.

[0038] The corresponding labels in the attached diagram are named as follows: Frame 1, Detection Component 2, Vessel 21, Motor 22, Clamping Arm 23, Stirring Component 3, Gas Storage Chamber 31, Air Inlet 311, Air Outlet 312, Limiting Block 313, Stirring Rod 32, Support Rod 321, Movable Rod 322, Cross Rod 323, Wedge-shaped Through Hole 324, Fan Blade 33, Piston 34, Spring 35, Defoaming Component 4, Drive Chamber 41, Exhaust Port 411, Pressing Plate 42, Sealing Ball 43, Reset Spring 44. Detailed Implementation

[0039] The following will describe the concept and technical effects of this utility model clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are all within the scope of protection of this utility model.

[0040] Example:

[0041] Please see Figure 1 and Figure 2The utility model relates to an insulating oil dielectric strength testing device, including frame 1 and the detection component 2 in frame 1, and the detection component 2 includes the sealed vessel 21 for containing insulating oil and the detection unit for dielectric strength detection, and the detection unit is prior art, and the electrode and other remaining parts can refer to the automatic constant temperature type insulating oil dielectric strength tester of CN106093740B, and here, too much is not repeated. The utility model mainly solves the elimination bubble in the vessel 21 and the stirring to insulating oil in dielectric detection. The material of vessel 21 is borosilicate glass (temperature range of resistance-50~300 DEG C), and the volume is 500ml. The top of vessel 21 is equipped with screw thread sealing cover (with O type rubber ring, diameter 80mm), and the electrode is arranged in vessel 21 through the sealing cover and is connected with external high voltage generator (output voltage 0~100kV, step precision 1kV) and ground terminal respectively, and the detection unit is integrated voltage acquisition module (sampling rate 1kHz) and breakdown judgment circuit (response time <1ms), and data is transmitted to host computer through RS485 interface. The outer wall of vessel 21 is equipped with the clamping arm 23 for clamping vessel 21, and the end clamping part of clamping arm 23 is wrapped with silica gel layer, and motor 22 is arranged on frame 1, and 57 step motor (torque 1.2 N.m) is selected, and the driving shaft is equipped with photoelectric encoder (resolution 1000 P / R), and the control inclination angle precision is ±0.5 DEG, and the driving shaft of motor 22 is fixedly connected with clamping arm 23. Vessel 21 is connected with inlet valve and exhaust valve (not shown), and electromagnetic proportional valve (model SMC VEF3120) is used, and the inlet is connected with nitrogen cylinder (volume 40L, pressure 15MPa) through phi 6mm polytetrafluoroethylene hose, and the outlet is connected with the gas inlet interface (inner diameter 4mm) on the top of vessel 21, and the exhaust valve adopts normally closed pneumatic ball valve (model FESTO MS6-LR), and is installed at the bottom of vessel (21), and is connected with external waste recovery tank through phi 8mm hose, and the exhaust flow can be adjusted by PLC (range 0.5~5L / min).

[0042] Specific working procedure: through motor 22 drive clamping arm 23 drive vessel 21 to tilt to 15 DEG, last 5 minutes, make insulating oil form liquid level gradient under the action of gravity, accelerate internal bubble to gather to liquid level high position and float to the top of vessel 21 along with the tilt movement, and open inlet valve, and inject nitrogen (purity >=99.99%) to vessel 21 at 0.3MPa pressure, while exhaust valve is at 3L / min flow rate exhaust air, last 5 minutes. Double effect eliminates the bubble that insulating oil is wrapped when contacting with the wall due to surface tension or viscosity, and reduces the oxidation influence of oxygen and moisture to oil quality, thereby reducing the abnormal discharge and data deviation caused by bubble

[0043] Please refer to Figures 2-4It also comprises a stirring assembly 3, which comprises a gas storage chamber 31, a fan blade 33 and a stirring rod 32; the gas storage chamber 31 is fixedly arranged in the inner wall of the top cover of the vessel 21 and located at the center of the inner wall of the top cover, the gas storage chamber 31 is provided with an air inlet 311 (inner diameter 5 mm) and an air outlet 312 (inner diameter 0.5 mm), the air inlet 311 is communicated with the nitrogen cylinder through a pipeline, a first one-way valve is arranged on the pipeline connected with the air inlet 311, the fan blade 33 is designed with two groups of six-blade turbines (blade inclination angle 45°) and is rotationally connected with the air outlet 312 through a bearing, the free end of the rotating shaft of the fan blade 33 is fixedly connected with the stirring rod 32 through a coupling, a piston 34 is slidably arranged in the gas storage chamber 31, the piston 34 is connected with a spring 35, the free end of the spring 35 is connected with the gas storage chamber 31, the piston 34 is arranged at the rear end of the air inlet 311, and a limiting block 313 is arranged in the gas storage chamber 31 and located at the upper end of the air inlet 311.

[0044] Specific working process: before the insulating oil is introduced into the vessel 21, the nitrogen cylinder fills nitrogen into the gas storage chamber 31 through the air inlet 311 at a pressure of 0.5 MPa, which is sprayed out through the air outlet 312, so as to drive the fan blade 33 to rotate, the fan blade 33 drives the stirring rod 32 to rotate, so that the nitrogen is uniformly distributed in the vessel 21 and forms a vortex in the vessel 21, thereby accelerating the discharge of residual air in the vessel 21. At the same time, after the nitrogen enters the gas storage chamber 31, it will drive the piston 34 to move in the gas storage chamber 31 and stretch the spring 35 (see Figure 3 ), so as to increase the space of the gas storage chamber 31, and in the process of continuously introducing nitrogen, a part of the nitrogen will be temporarily stored in the gas storage chamber 31. After the insulating oil is introduced into the vessel 21, the nitrogen cylinder stops delivering nitrogen to the vessel 21. Since there are originally bubbles in the insulating oil, at this time, the piston 34 in the gas storage chamber 31 is reset to the initial state under the driving of the pre-tightening force of the spring 35, so as to squeeze the pre-stored nitrogen in the gas storage chamber 31 to the vessel 21 through the air outlet 311, and drive the fan blade 33 to continue rotating at 250 rpm, so that the stirring rod 32 stirs the insulating oil to generate a vortex, which lasts for 2 minutes, so that the bubbles are smaller and more dispersed, which helps the bubbles to float to the oil surface faster and accelerate the breaking of the bubbles.

[0045] Please refer to Figures 2-6Further comprising a defoaming assembly 4, the defoaming assembly 4 comprising a driving chamber 41, the driving chamber 41 being arranged right below the gas storage chamber 31, the driving chamber 41 being in communication with the gas storage chamber 31 through the gas inlet 312, the driving chamber 41 being provided with a gas outlet 411; the fan blade 33 being arranged in the driving chamber 41, the stirring rod 32 comprising a support rod 321, a movable rod 322 and a cross rod 323, one end of the support rod 321 being fixedly connected with the rotating shaft of the fan blade 33, the support rod 321 being arranged through the inner wall of the movable rod 322, the inner wall of the movable rod 322 being in sliding connection with the outer wall of the support rod 321, the movable rod 322 passing through the driving chamber 41, one end of the movable rod 322 arranged in the driving chamber 41 being connected with a pressing plate 42, one end of the cross rod 323 being fixedly connected with the free end of the movable rod 322, a sliding groove (not shown) with a width of 12 mm and a depth of 5 mm being arranged in the driving chamber 41, the pressing plate 42 being in sliding connection with the sliding groove; the movable rod 322 and the cross rod 323 being made of a material with a density lower than that of the insulating oil, at least part of the movable rod 322 and the cross rod 323 being arranged in a hollow structure, so that the overall density of the movable rod 322 and the cross rod 323 is lower than that of the insulating oil and they float on the liquid surface; the outer surface of the movable rod 322 and the cross rod 323 being provided with an oil-repellent coating, the material of the movable rod 322 and the cross rod 323 being polypropylene (density 0.90 g / cm³), the outer diameter being 10 mm and the wall thickness being 1 mm. The defoaming assembly 4 further comprises a vacuum pump (not shown), a rotary vane vacuum pump (limiting vacuum 5 mbar, pumping speed 10 L / min) being adopted, the vacuum pump being in communication with the gas inlet 311 through a pipeline, a second one-way valve being arranged on the pipeline connected with the gas inlet 311 to prevent the reverse flow of gas. The cross rod 323 is in a hollow structure, the cross rod 323 being in communication with the vacuum pump through a pipeline, the free end of the cross rod 323 being a wedge-shaped through hole 324 (opening angle 30°), the cross rod 323 being provided with a sealing ball 43 for sealing the wedge-shaped through hole 324, the sealing ball 43 being connected with a return spring 44, the free end of the return spring 44 being fixedly connected with the cross rod 323.

[0046] Specific workflow: when the nitrogen cylinder fills nitrogen into the gas storage chamber 31 and the piston 34 extrudes the gas storage chamber 31, both of them make the gas act on the pressing plate 42, thereby pressing the pressing plate 42 downward, so that the movable rod 322 extends and drives the cross rod 323 in the insulating oil, and under the drive of the fan blade 33, the cross rod 323 stirs the insulating oil, so that the bubbles float to the oil surface. After the nitrogen cylinder stops filling nitrogen into the gas storage chamber 31 and the piston 34 resets to the initial position, the pressing plate 42 loses the external force, and because the movable rod 322 and the cross rod 323 are made of materials with lower density than the insulating oil, the cross rod 323 floats to the oil surface. Then start the vacuum pump to depressurize the vessel 21 to 5mbar, which is beneficial to the bubble discharge, and the suction force overcomes the elastic force of the reset spring 44, so that the sealing ball 43 is separated from the wedge-shaped through hole 324, and the small bubbles not absorbed by the vacuum pump are sucked into the cross rod 323 through the wedge-shaped through hole 324 and discharged through the pipeline. After the vacuum pump is closed, the reset spring 44 drives the sealing ball 43 to seal the wedge-shaped through hole 324. Finally, nitrogen is continuously filled into the vessel 21 at a lower flow rate, so that the cross rod 3 is in the insulating oil and performs dielectric detection, continuously stirs the insulating oil, which is beneficial to heating and avoids oil stratification.

[0047] The above is only an embodiment of the present application, and the specific structure and characteristics of the scheme known in the art are not described in detail. It should be pointed out that for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, and these will not affect the effect and practicality of the present application. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.

Claims

1. An insulating oil dielectric strength testing device, comprising a rack (1) and a detection assembly (2) arranged in the rack (1), the detection assembly (2) comprising a vessel (21) for containing insulating oil and a detection unit for dielectric strength detection; characterized in that, Also include: Motor (22), the motor (22) is arranged on the rack (1); Clamping arm (23), the clamping arm (23) is used for clamping utensil (21), the clamping arm (23) is fixedly connected with the output end of motor (22); Air inlet valve, the air inlet valve is communicated with utensil (21) by pipeline; Exhaust valve, the exhaust valve is communicated with utensil (21) by pipeline; Nitrogen cylinder, the nitrogen cylinder is communicated with air inlet valve by pipeline.

2. The insulating oil dielectric strength testing device according to claim 1, characterized in that: Also include stirring assembly (3), the stirring assembly (3) includes gas storage chamber (31), fan blade (33) and stirring rod (32);The gas storage chamber (31) is fixedly arranged in the inner wall of the top cover of utensil (21), the gas storage chamber (31) is provided with air inlet (311) and air outlet (312), the air inlet (311) is communicated with nitrogen cylinder by pipeline, the pivot end of fan blade (33) is rotatably connected with air outlet (312), and the free end of the pivot of fan blade (33) is fixedly connected with stirring rod (32).

3. The device for testing the dielectric strength of insulating oil according to claim 2, characterized in that: The piston (34) is slidably arranged in the gas storage chamber (31), the piston (34) is connected with spring (35), the free end of spring (35) is connected with gas storage chamber (31), and the piston (34) is arranged at the rear end of air inlet (311).

4. The insulating oil dielectric strength testing device according to claim 3, characterized in that: Also include defoaming assembly (4), the defoaming assembly (4) includes drive chamber (41), the drive chamber (41) is arranged at the bottom of gas storage chamber (31), the drive chamber (41) is communicated with gas storage chamber (31) through air outlet (312), and the drive chamber (41) is provided with exhaust port (411);The fan blade (33) is arranged in the drive chamber (41), the stirring rod (32) includes support rod (321), movable rod (322) and cross bar (323), one end of the support rod (321) is fixedly connected with the pivot of fan blade (33), the support rod (321) is arranged in the inner wall of movable rod (322), the movable rod (322) passes through the drive chamber (41), one end of the movable rod (322) is connected with the pressing plate (42) arranged in the drive chamber (41), one end of the cross bar (323) is fixedly connected with the free end of movable rod (322), and the movable rod (322) and the cross bar (323) are made of material with density lower than that of insulating oil.

5. The device for testing the dielectric strength of an insulating oil according to claim 4, characterized in that: At least part of the movable rod (322) and the cross bar (323) is provided as a hollow structure, so that the overall density of the movable rod (322) and the cross bar (323) is less than that of insulating oil and floats on the liquid surface;The outer surface of the movable rod (322) and the cross bar (323) is provided with an oil-repellent coating.

6. The device for testing the dielectric strength of an insulating oil according to claim 4, characterized in that: The defoaming assembly (4) further includes a vacuum pump, which is communicated with the air inlet (311) by pipeline.

7. The device for testing the dielectric strength of an insulating oil according to claim 6, characterized in that: The cross bar (323) is a hollow structure, the cross bar (323) is communicated with the vacuum pump through a pipeline, the free end of the cross bar (323) is a wedge-shaped through hole (324), the cross bar (323) is internally provided with a sealing ball (43) for sealing the wedge-shaped through hole (324), the sealing ball (43) is connected with a reset spring (44), and the free end of the reset spring (44) is fixedly connected with the cross bar (323).

8. The insulating oil dielectric strength testing device according to claim 7, characterized in that: The inner wall of the movable rod (322) is slidably connected with the outer wall of the supporting rod (321); and the driving chamber (41) is internally provided with a sliding groove, and the pressing plate (42) is slidably connected with the sliding groove.

9. The device of claim 6, wherein: A first one-way valve is arranged on the pipeline connected between the nitrogen cylinder and the air inlet (311); and a second one-way valve is arranged on the pipeline connected between the vacuum pump and the air inlet (311).

10. The device for testing the dielectric strength of insulating oil according to claim 6, characterized in that: The air storage chamber (31) is internally provided with a limiting block (313), and the limiting block (313) is arranged at the upper end of the air inlet (311).

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