Immersion piping system integrating cooling fluid and bare electrical cable

Abstract

The present application relates to the technical field of liquid cooling, and provides an immersed pipeline system integrating cooling liquid and bare cable, which comprises an integrated pipeline, a plurality of immersed liquid-cooled battery packs, an immersed liquid-cooled unit, an immersed liquid-cooled energy storage converter and a liquid-cooled pump; the integrated pipeline is internally provided with bare electric wires and a cooling liquid channel; each immersed liquid-cooled battery pack is connected in series through the integrated pipeline; the immersed liquid-cooled energy storage converter is connected to a liquid inlet of the immersed liquid-cooled unit, and a negative electrode thereof is connected to a negative electrode of the immersed liquid-cooled battery pack at the tail of the series connection; the immersed liquid-cooled energy storage converter is connected to the immersed liquid-cooled battery pack at the head of the series connection, and a positive electrode thereof is connected to a positive electrode of the immersed liquid-cooled battery pack at the head of the series connection; the immersed liquid-cooled unit drives immersed cooling liquid to be circulated and cooled for each immersed liquid-cooled battery pack and the immersed liquid-cooled energy storage converter in series through the integrated pipeline. The immersed pipeline system can realize intelligent energy-saving temperature control, energy saving and efficiency improvement, and long-life operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid cooling, in particular to an immersion pipeline system integrating cooling liquid and bare cable. BACKGROUND

[0002] At present, the traditional liquid cooling pipeline system has the following technical problems:

[0003] The cable and the liquid cooling pipeline need to be separated: the traditional liquid cooling system only supports the flow channel of the cooling liquid, and the cable only supports the power transmission channel, and the two cannot be integrated, occupying the layout design space;

[0004] The cable has poor heat dissipation: the traditional cable generates a lot of heat when transmitting power, and only the increase of the cross-sectional area of copper / aluminum can ensure that the temperature rise does not exceed the range, and there is a lack of effective forced heat dissipation control.

[0005] The traditional liquid cooling system needs high protection design for the liquid cooling pipeline and the cable connector to ensure the dustproof, waterproof and moisture-proof requirements of the system, and the material cost is high.

[0006] The cable is thick and hard: the traditional cable is usually designed to be thick to ensure current carrying demand, and needs insulation and pressure resistant outer skin protection, resulting in thick and hard cable. SUMMARY

[0007] The purpose of the present application is to solve at least one of the technical problems in the background art, and to provide an immersion pipeline system integrating cooling liquid and bare cable.

[0008] To achieve the above purpose, the present application provides an immersion pipeline system integrating cooling liquid and bare cable, comprising: an integrated pipeline, a plurality of immersion liquid cooling battery packs, an immersion liquid cooling unit, an immersion liquid cooling energy storage converter and a liquid cooling pump;

[0009] The integrated pipeline is provided with a bare wire and a cooling liquid channel, and the immersion cooling liquid flows outside the bare wire through the cooling liquid channel;

[0010] The immersion liquid cooling battery packs are connected in series through the integrated pipeline, and the tail of the immersion liquid cooling battery pack is connected with the liquid outlet of the immersion liquid cooling unit through the cooling liquid channel in the integrated pipeline;

[0011] The immersion liquid cooling energy storage converter is connected with the liquid inlet of the immersion liquid cooling unit through the cooling liquid channel in the integrated pipeline, and the negative electrode is connected with the negative electrode of the immersion liquid cooling battery pack at the tail through the bare wire in the integrated pipeline;

[0012] The immersed liquid cooling energy storage converter is connected with the immersed liquid cooling battery pack behind in series through the cooling liquid channel in the integrated pipeline, and the positive electrode of the immersed liquid cooling energy storage converter is connected with the positive electrode of the immersed liquid cooling battery pack behind in series through the bare wire in the integrated pipeline;

[0013] The immersed liquid cooling unit drives the immersed cooling liquid to circulate and cool the immersed liquid cooling battery pack and the immersed liquid cooling energy storage converter in series through the integrated pipeline.

[0014] According to an aspect of the present application, the integrated pipeline comprises a first integrated pipeline, a second integrated pipeline, a third integrated pipeline, a fourth integrated pipeline and a fifth integrated pipeline.

[0015] The immersed liquid cooling battery pack comprises a first immersed liquid cooling battery pack, a second immersed liquid cooling battery pack and a third immersed liquid cooling battery pack.

[0016] The positive electrode of the first immersed liquid cooling battery pack is connected with the positive electrode of the immersed liquid cooling energy storage converter through the bare wire in the first integrated pipeline, and is connected with the internal cooling channel of the immersed liquid cooling energy storage converter through the cooling liquid channel in the first integrated pipeline.

[0017] The negative electrode of the first immersed liquid cooling battery pack is connected with the positive electrode of the second immersed liquid cooling battery pack through the bare wire in the second integrated pipeline to form a series connection, and is connected with the internal cooling channel of the second immersed liquid cooling battery pack through the cooling liquid channel in the second integrated pipeline.

[0018] The negative electrode of the second immersed liquid cooling battery pack is connected with the positive electrode of the third immersed liquid cooling battery pack through the bare wire in the third integrated pipeline to form a series connection, and is connected with the internal cooling channel of the third immersed liquid cooling battery pack through the cooling liquid channel in the third integrated pipeline.

[0019] The negative electrode of the third immersed liquid cooling battery pack is connected with the negative electrode of the immersed liquid cooling energy storage converter through the bare wire in the fourth integrated pipeline and the bare wire in the fifth integrated pipeline, and is connected with the liquid outlet of the immersed liquid cooling unit through the cooling liquid channel in the fourth integrated pipeline.

[0020] The immersed liquid cooling energy storage converter is connected with the liquid inlet of the immersed liquid cooling unit through the cooling liquid channel in the fifth integrated pipeline.

[0021] According to an aspect of the present application, the immersed liquid cooling unit comprises a liquid cooling pump, which circulates and cools the immersed cooling liquid.

[0022] According to one aspect of the present application, the liquid cooling pump pumps out the immersion cooling liquid through the liquid outlet of the immersion liquid cooling unit, the immersion cooling liquid flows through the fourth integrated pipeline to the internal cooling channel of the third immersion liquid cooling battery pack to cool the third immersion liquid cooling battery pack, after the third immersion liquid cooling battery pack is cooled, the immersion cooling liquid flows through the third integrated pipeline to the internal cooling channel of the second immersion liquid cooling battery pack to cool the second immersion liquid cooling battery pack, after the second immersion liquid cooling battery pack is cooled, the immersion cooling liquid flows through the second integrated pipeline to the internal cooling channel of the first immersion liquid cooling battery pack to cool the first immersion liquid cooling battery pack, after the first immersion liquid cooling battery pack is cooled, the immersion cooling liquid flows through the first integrated pipeline to the internal cooling channel of the immersion liquid cooling energy storage converter to cool the immersion liquid cooling energy storage converter, after the immersion liquid cooling energy storage converter is cooled, the immersion cooling liquid flows through the fifth integrated pipeline into the immersion liquid cooling unit and is cooled by the liquid cooling pump.

[0023] According to one aspect of the present application, the integrated pipeline comprises a pipeline shell, a cooling liquid channel, a bare electric wire and a limiting fixing clamping column.

[0024] The limiting fixing clamping column is symmetrically arranged on the inner wall of the pipeline shell, and the bare electric wire is clamped between the two symmetrically arranged limiting fixing clamping columns.

[0025] The cooling liquid channel is symmetrically arranged on both sides of the overall structure formed by the bare electric wire and the two limiting fixing clamping columns inside the pipeline shell.

[0026] According to one aspect of the present application, the pipeline shell is made of PTFE material, and the insulation strength is 50kV / mm.

[0027] According to one aspect of the present application, the limiting fixing clamping column is made of PTFE material or PA material, and the dielectric strength is 50kV / mm.

[0028] According to the scheme of the present application, the integrated pipeline of the present application can replace the traditional cable and liquid cooling pipeline separation type design, which can effectively reduce the layout space by more than 50% and reduce the design cost by at least 20%;

[0029] The integrated pipeline design of the present application can realize simultaneous cooling and temperature control of the cable (bare electric wire), ensure that the cable can be maintained at 25℃-35℃, and prolong the service life of the power cable;

[0030] In the integrated pipeline of the present application, the overall pipeline and the bare electric wire are no longer solidly attached, which can increase the flexible layout of the overall cable pipeline and reduce the minimum bending radius of the cable.

[0031] The integrated pipeline of the present application can release the protection requirements of the cable connector, can be directly locked and fixed by a bare crimping screw, and saves the high protection cable plug-in connector, thereby reducing the cost.

[0032] The integrated pipeline of the present application can be used with a traditional liquid cooling waterproof quick connector, and the internal bare cable can be directly screwed and locked with a copper bar or cable splicing, thereby releasing the protection requirements of the cable connector, saving the high protection cable plug-in connector, and reducing the cost.

[0033] The submerged pipeline system of the present application can realize intelligent energy-saving temperature control, energy-saving and efficiency-increasing, and long-life operation. The present application supports cable temperature control and reduces heat loss. For example, when the temperature is low in winter, the cable itself can be used to heat the cooling liquid to realize system temperature control and reduce system energy consumption. When the temperature is high in summer, the cooling liquid is used to cool the cable. The cable in the present application has strong temperature uniformity, which can effectively prolong the service life of the cable. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A structural arrangement diagram of a submerged pipeline system integrating cooling liquid and bare cable according to an embodiment of the present application is schematically shown;

[0035] Figure 2 A cross-sectional view of an integrated pipeline according to an embodiment of the present application is schematically shown;

[0036] In the figure: 1-pipeline shell, 2-cooling liquid channel, 3-bare wire, 4-limiting fixing clamping column, 5-first integrated pipeline, 6-second integrated pipeline, 7-third integrated pipeline, 8-fourth integrated pipeline, 9-fifth integrated pipeline, 10-first submerged liquid-cooled battery pack, 11-second submerged liquid-cooled battery pack, 12-third submerged liquid-cooled battery pack, 13-submerged liquid-cooled energy storage converter, 14-submerged liquid-cooled unit, 15-liquid-cooled pump. DETAILED DESCRIPTION

[0037] The present application will now be discussed with reference to exemplary embodiments. It should be understood that the discussed embodiments are merely to enable those of ordinary skill in the art to better understand and thus implement the present application, and are not intended to imply any limitation on the scope of the present application.

[0038] As used herein, the term "comprising" and variations thereof are to be construed as meaning "including, but not limited to". The term "based on" is to be construed as "based at least in part on". The terms "one embodiment" and "an embodiment" are to be construed as "at least one embodiment".

[0039] Figure 1A structural layout diagram of an integrated cooling liquid and bare cable immersion pipeline system according to an embodiment of the present application is schematically shown; Figure 2 A sectional view of an integrated pipeline according to an embodiment of the present application is schematically shown. In combination Figure 1 and Figure 2 As shown in the present application, the integrated cooling liquid and bare cable immersion pipeline system comprises: an integrated pipeline, a plurality of immersion liquid-cooled battery packs, an immersion liquid-cooled unit, an immersion liquid-cooled energy storage converter, and a liquid-cooled pump;

[0040] The integrated pipeline is provided with a bare wire and a cooling liquid channel, and the immersion cooling liquid flows outside (the outer wall) of the bare wire through the cooling liquid channel;

[0041] After the immersion liquid-cooled battery packs are connected in series through the integrated pipeline, the tail immersion liquid-cooled battery pack is connected to the liquid outlet of the immersion liquid-cooled unit through the cooling liquid channel in the integrated pipeline;

[0042] The immersion liquid-cooled energy storage converter is connected to the liquid inlet of the immersion liquid-cooled unit through the cooling liquid channel in the integrated pipeline, and the negative electrode thereof is connected to the negative electrode of the tail immersion liquid-cooled battery pack connected in series through the bare wire in the integrated pipeline;

[0043] The immersion liquid-cooled energy storage converter is connected to the head immersion liquid-cooled battery pack connected in series through the cooling liquid channel in the integrated pipeline, and the positive electrode thereof is connected to the positive electrode of the head immersion liquid-cooled battery pack connected in series through the bare wire in the integrated pipeline;

[0044] The immersion liquid-cooled unit drives the immersion cooling liquid to circulate and cool the immersion liquid-cooled battery packs and the immersion liquid-cooled energy storage converter connected in series through the integrated pipeline.

[0045] Further, as Figure 2 shown in the present embodiment, the integrated pipeline comprises: a pipeline shell 1, a cooling liquid channel 2, a bare wire 3, and a limiting and fixing clamping column 4;

[0046] The limiting and fixing clamping column 4 is symmetrically arranged on the inner wall of the pipeline shell 1, and the bare wire 3 is clamped between the two symmetrically arranged limiting and fixing clamping columns 4;

[0047] The cooling liquid channel 2 is symmetrically arranged on both sides of the overall structure formed by the bare wire 3 and the two limiting and fixing clamping columns 4 inside the pipeline shell 1. In this way, the design layout space of the integrated pipeline is compact, the design cost is reduced, the integrated pipeline can integrate the cooling flow channel and the current channel, effectively reducing the system layout space; and the integrated design can weaken the protection level of the cable interface, reducing the design cost.

[0048] In this embodiment, the pipe shell 1 is made of PTFE material with an insulation strength of 50kV / mm and is located at the outermost edge of the system pipe. The coolant channel 2 meets the flow requirements of the submerged coolant, and the inner diameter of the channel is designed according to the different cable and flow channel requirements. The submerged coolant is a non-flammable hydrocarbon compound with good fluidity and insulation properties. The bare wire is a copper / aluminum bare cable, located at the innermost edge of the system, and is made of multi-core bare copper / aluminum wire for power transmission. The limiting and fixing pin 4 is located between the pipe shell and the cable, and is made of PTFE, PA, etc., with an insulation withstand voltage of 50kV / mm, and is used to limit the position of the bare wire 3 in the pipe.

[0049] Furthermore, such as Figure 1 As shown, in this embodiment, the integrated pipe includes: a first integrated pipe 5, a second integrated pipe 6, a third integrated pipe 7, a fourth integrated pipe 8, and a fifth integrated pipe 9.

[0050] The submersible liquid-cooled battery pack includes: a first submersible liquid-cooled battery pack 10, a second submersible liquid-cooled battery pack 11, and a third submersible liquid-cooled battery pack 12;

[0051] The positive terminal of the first submerged liquid-cooled battery pack 10 is connected to the positive terminal of the submerged liquid-cooled energy storage converter 13 through a bare wire in the first integrated pipe 5, and is connected to the internal cooling channel of the submerged liquid-cooled energy storage converter 13 through a coolant channel in the first integrated pipe 5.

[0052] The negative terminal of the first immersion liquid-cooled battery pack 10 is connected in series with the positive terminal of the second immersion liquid-cooled battery pack 11 through the bare wire in the second integrated pipe 6, and is connected to the internal cooling channel of the second immersion liquid-cooled battery pack 11 through the coolant channel in the second integrated pipe 6.

[0053] The negative terminal of the second immersion liquid-cooled battery pack 11 is connected in series with the positive terminal of the third immersion liquid-cooled battery pack 12 through the bare wire in the third integrated pipe 7, and is connected to the internal cooling channel of the third immersion liquid-cooled battery pack 12 through the coolant channel in the third integrated pipe 7.

[0054] The negative terminal of the third immersion liquid-cooled battery pack 12 is connected to the negative terminal of the immersion liquid-cooled energy storage converter 13 through the bare wires in the fourth integrated pipe 8 and the fifth integrated pipe 9, and is connected to the outlet of the immersion liquid-cooled unit 14 through the coolant channel in the fourth integrated pipe 8.

[0055] The submerged liquid-cooled energy storage converter 13 is connected to the inlet of the submerged liquid-cooled unit 14 through the coolant passage in the fifth integrated pipe 9.

[0056] Furthermore, such asFigure 1 As shown, in the present embodiment, the immersion liquid cooling unit 14 comprises a liquid cooling pump 15 for circulating and cooling the immersion coolant.

[0057] Further, as Figure 1 As shown, in the present embodiment, the liquid cooling pump 15 pumps out the immersion coolant through the liquid outlet of the immersion liquid cooling unit, and the immersion coolant flows through the fourth integrated pipeline 8 to the internal cooling channel of the third immersion liquid cooling battery pack 12 to cool the third immersion liquid cooling battery pack 12, and after the third immersion liquid cooling battery pack 12 is cooled, the immersion coolant flows through the third integrated pipeline 7 to the internal cooling channel of the second immersion liquid cooling battery pack 11 to cool the second immersion liquid cooling battery pack 11, and after the second immersion liquid cooling battery pack 11 is cooled, the immersion coolant flows through the second integrated pipeline 6 to the internal cooling channel of the first immersion liquid cooling battery pack 10 to cool the first immersion liquid cooling battery pack 10, and after the first immersion liquid cooling battery pack 10 is cooled, the immersion coolant flows through the first integrated pipeline 5 to the internal cooling channel of the immersion liquid cooling energy storage converter 13 to cool the immersion liquid cooling energy storage converter 13, and after the immersion liquid cooling energy storage converter 13 is cooled, the immersion coolant flows through the fifth integrated pipeline 9 to the immersion liquid cooling unit 14 and is circulated and cooled by the liquid cooling pump 15, and then the above-mentioned circulation cooling of the immersion liquid cooling battery packs and the immersion liquid cooling energy storage converter is performed.

[0058] According to the above-mentioned scheme of the present application, the integrated pipeline of the present application can replace the traditional cable and liquid cooling pipeline separation design, effectively reducing the layout space by more than 50%, and reducing the design cost by at least 20%;

[0059] The integrated pipeline design of the present application can realize simultaneous cooling and temperature control of the cable (bare wire), ensure that the cable can be maintained at 25-35℃, and prolong the service life of the power cable;

[0060] In the integrated pipeline of the present application, the overall pipeline and the bare wire are no longer solidly attached, which can increase the flexible layout of the overall cable pipeline and reduce the minimum bending radius of the cable;

[0061] The integrated pipeline of the present application can be matched with a conventional liquid cooling waterproof quick connector, the internal bare cable can be directly screwed to a copper bar or a cable splicing, the protection requirement of the cable connector can be released, the high-protection cable plug-in connector can be saved, and the cost is reduced.

[0062] The submerged pipeline system of the present application can realize intelligent energy-saving temperature control, realize energy-saving and efficiency-increasing, long service life operation, the present application supports cable temperature control, reduces heat loss, when the temperature is relatively low in winter, the cable itself can be used to heat the coolant to realize system temperature control, reduce system energy consumption; when the temperature is relatively high in summer, the coolant is used to cool the cable; the cable in the present application has strong temperature uniformity, which can effectively prolong the service life of the cable.

[0063] The above description is merely the preferred embodiment and the explanation of the technical principles of the present application. Those skilled in the art should understand that the scope of the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by any combinations of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features can be replaced with the technical features disclosed in the present application (but not limited to) having similar functions to form technical solutions.

[0064] It should be understood that the size of the serial number of each step in the summary and embodiments of the present application does not absolutely mean the order of execution, the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

Claims

1. Immersed piping system integrating cooling liquid and bare electrical cable, characterized in that, The application relates to an integrated pipeline, a plurality of immersed liquid-cooled battery packs, an immersed liquid-cooled unit, an immersed liquid-cooled energy storage converter and a liquid-cooled pump. The integrated pipeline is internally provided with bare wires and a cooling liquid channel, and immersed cooling liquid flows outside the bare wires through the cooling liquid channel. The immersed liquid-cooled battery packs are connected in series through the integrated pipeline, and the tail-end immersed liquid-cooled battery pack is connected with the liquid outlet of the immersed liquid-cooled unit through the cooling liquid channel in the integrated pipeline. The immersed liquid-cooled energy storage converter is connected with the liquid inlet of the immersed liquid-cooled unit through the cooling liquid channel in the integrated pipeline, and the negative electrode thereof is connected with the negative electrode of the tail-end immersed liquid-cooled battery pack through the bare wires in the integrated pipeline. The immersed liquid-cooled energy storage converter is connected with the head-end immersed liquid-cooled battery pack through the cooling liquid channel in the integrated pipeline, and the positive electrode thereof is connected with the positive electrode of the head-end immersed liquid-cooled battery pack through the bare wires in the integrated pipeline. The immersed liquid-cooled unit drives the immersed cooling liquid to circulate and cool the immersed liquid-cooled battery packs and the immersed liquid-cooled energy storage converter in sequence through the integrated pipeline. The integrated pipeline comprises a first integrated pipeline, a second integrated pipeline, a third integrated pipeline, a fourth integrated pipeline and a fifth integrated pipeline.

2. The submerged piping system integrating cooling liquid and bare electrical cable according to claim 1, characterized in that, The immersed liquid-cooled battery packs comprise a first immersed liquid-cooled battery pack, a second immersed liquid-cooled battery pack and a third immersed liquid-cooled battery pack. The positive electrode of the first immersed liquid-cooled battery pack is connected with the positive electrode of the immersed liquid-cooled energy storage converter through the bare wires in the first integrated pipeline, and is connected with the internal cooling channel of the immersed liquid-cooled energy storage converter through the cooling liquid channel in the first integrated pipeline. The negative electrode of the first immersed liquid-cooled battery pack is connected with the positive electrode of the second immersed liquid-cooled battery pack through the bare wires in the second integrated pipeline to form a series connection, and is connected with the internal cooling channel of the second immersed liquid-cooled battery pack through the cooling liquid channel in the second integrated pipeline. The negative electrode of the second immersed liquid-cooled battery pack is connected with the positive electrode of the third immersed liquid-cooled battery pack through the bare wires in the third integrated pipeline to form a series connection, and is connected with the internal cooling channel of the third immersed liquid-cooled battery pack through the cooling liquid channel in the third integrated pipeline. The negative electrode of the third immersed liquid-cooled battery pack is connected with the negative electrode of the immersed liquid-cooled energy storage converter through the bare wires in the fourth integrated pipeline and the fifth integrated pipeline, and is connected with the liquid outlet of the immersed liquid-cooled unit through the cooling liquid channel in the fourth integrated pipeline. The immersed liquid-cooled energy storage converter is connected with the liquid inlet of the immersed liquid-cooled unit through the cooling liquid channel in the fifth integrated pipeline. The immersed liquid-cooled unit comprises a liquid-cooled pump which circulates and cools the immersed cooling liquid.

3. The submerged piping system integrating cooling fluid and bare electrical cable of claim 2, wherein, ​ 4. The submerged piping system integrating cooling liquid and bare electrical cable according to claim 3, characterized in that, The liquid cooling pump pumps out the immersion cooling liquid through the liquid outlet of the immersion liquid cooling unit, the immersion cooling liquid flows through the fourth integrated pipeline to the internal cooling channel of the third immersion liquid cooling battery pack to cool the third immersion liquid cooling battery pack, after the third immersion liquid cooling battery pack is cooled, the immersion cooling liquid flows through the third integrated pipeline to the internal cooling channel of the second immersion liquid cooling battery pack to cool the second immersion liquid cooling battery pack, after the second immersion liquid cooling battery pack is cooled, the immersion cooling liquid flows through the second integrated pipeline to the internal cooling channel of the first immersion liquid cooling battery pack to cool the first immersion liquid cooling battery pack, after the first immersion liquid cooling battery pack is cooled, the immersion cooling liquid flows through the first integrated pipeline to the internal cooling channel of the immersion liquid cooling energy storage converter to cool the immersion liquid cooling energy storage converter, after the immersion liquid cooling energy storage converter is cooled, the immersion cooling liquid flows through the fifth integrated pipeline into the immersion liquid cooling unit to be cooled by the liquid cooling pump.

5. The immersed pipe system of integrated cooling liquid and bare electrical cable according to any of claims 1-4, characterized in that, The integrated pipeline comprises a pipeline shell, a cooling liquid channel, a bare wire and a limiting and fixing clamping column; The limiting and fixing clamping column is symmetrically arranged on the inner wall of the pipeline shell, and the bare wire is clamped between the two symmetrically arranged limiting and fixing clamping columns; The cooling liquid channel is symmetrically arranged on both sides of the overall structure formed by the bare wire and the two limiting and fixing clamping columns inside the pipeline shell.

6. The submerged piping system integrating cooling liquid and bare electrical cable according to claim 5, characterized in that, The pipeline shell is made of PTFE material, and the dielectric strength thereof is 50kV / mm.

7. The submerged piping system of claim 5, wherein, The limiting and fixing clamping column is made of PTFE material or PA material, and the insulation strength thereof is 50kV / mm.

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