Water electrolysis system and maintenance method for insulated pipe

Abstract

To evaluate soundness of an insulated pipe that electrically insulates a water electrolysis stack and piping, and to realize operation control according to a degree of deterioration in insulation.SOLUTION: A water electrolysis system 1 includes: one or more water electrolysis stacks 10; an insulated pipe 16 that electrically insulates the water electrolysis stack 10 and piping; a DC power supply 11 that drives the water electrolysis stack 10 by supplying DC power to the water electrolysis stack 10; a current measuring part 20 that measures leakage current flowing through the insulated pipe 16; and a control device 22 that controls output of the DC power supply. The control device 22 displays on a display part 44 a measurement value of the leakage current flowing through the insulated pipe 16 measured by the current measuring part 20, and controls the DC power supplied to the water electrolysis stack 10 based on the measurement value of the leakage current.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water electrolysis system and a maintenance method for insulating piping. [Background technology]

[0002] In recent years, with the increase in emissions of greenhouse gases such as carbon dioxide, environmental issues such as global warming and energy issues such as the depletion of petroleum resources have been attracting attention. From this perspective, hydrogen energy has been attracting attention as a clean alternative energy source. However, in order to replace existing fossil fuels with hydrogen energy, a large amount of hydrogen is required.

[0003] Water electrolysis is one method of producing hydrogen. Demonstration projects for large-scale water electrolysis are underway in an effort to curb global warming. In particular, a demonstration project for a hydrogen production system with a capacity of several tens of megawatts (MW) that uses electricity generated by offshore wind power is underway in Europe, and it is expected that water electrolysis systems will continue to grow in size in the future. When producing MW-class hydrogen using water electrolysis systems, the water electrolysis stack (electrolyzer) is characterized by its low voltage and high current characteristics of several hundred volts and several thousand amperes.

[0004] Furthermore, efforts are being made to increase the scale of water electrolysis systems in order to reduce the cost of hydrogen production, with the introduction of water electrolysis systems with a capacity of around 500 GW expected by 2050. This is expected to reduce equipment costs through the mass production efficiency of the water electrolysis stacks required for hydrogen production. However, as mentioned above, water electrolysis stacks need to be driven by large currents and low voltages, and the DC power supplies required to achieve this are specialized applications, so cost reductions are not expected to progress. This means that it will be necessary to reduce the cost of power sources.

[0005] In large-scale water electrolysis systems, the need to operate multiple water electrolysis stacks with a single power supply has been advocated for high-efficiency operation of power sources. One method for operating multiple water electrolysis stacks simultaneously is to electrically connect them in series (hereinafter referred to as "multiple series connection"). By connecting multiple water electrolysis stacks in series to increase the voltage, it may be possible to reduce the number of step-down transformers and rectifiers when drawing power from the power grid. This is thought to enable large-scale hydrogen production at low cost. However, when connecting multiple water electrolysis stacks in series to increase the voltage, electrical insulation between the high-voltage water electrolysis stacks and the ground or piping, which are at earth potential, becomes an issue.

[0006] Patent Document 1 describes an insulation configuration for obtaining high-voltage output in a fuel cell stack. In the technology described in Patent Document 1, an insulating plate is provided between the lower end plate (housing) of the fuel cell stack and the installation base (ground) to ensure electrical insulation of the fuel cell stack, and an insulating mechanism is provided in part of the metal piping for supplying fuel gas and air to the fuel cell stack. This insulating plate ensures electrical insulation between the lower end plate and the support frame. Furthermore, the insulating mechanism prevents electrical connection between the upper and lower end plates of each fuel cell stack via the metal piping in a fuel cell in which multiple fuel cell stacks are connected in series. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-87863 Summary of the Invention [Problem to be solved by the invention]

[0008] The fuel cell stack described in Patent Document 1 is a fuel cell that operates in a high-temperature atmosphere of 600°C or higher, like a solid oxide fuel cell, and is a system that does not contain water. On the other hand, a water electrolysis stack electrolyzes water to produce hydrogen, so it requires the circulation of pure water. Furthermore, in the system for hydrogen gas produced by water electrolysis, a small amount of pure water is entrained in the produced hydrogen gas and passes through a polymer membrane before being discharged. The resistivity of pure water is lower than that of gas, and is 17.5 to 18.2 MΩ·cm for ultrapure water.

[0009] Therefore, when a water electrolysis stack is operated at a high voltage using a configuration similar to that described in Patent Document 1, a current determined by the applied voltage and the volume resistivity of pure water flows. This current causes electrolytic corrosion in the metal piping. Metal ions eluted by electrolytic corrosion not only deteriorate the water electrolysis stack, but may also deposit on the insulating mechanism installed in the piping, reducing the insulating properties of the insulating mechanism. In particular, if the insulating properties of the insulating mechanism installed in the piping deteriorate and dielectric breakdown occurs, the entire water electrolysis system must be shut down. If a large-scale water electrolysis system is instantly disconnected from the power grid, it may cause a disturbance to the power grid. For this reason, a system is needed to prevent the entire water electrolysis system from being shut down due to dielectric breakdown.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to evaluate the soundness of insulating piping that electrically insulates a water electrolysis stack from piping, and to realize operation control of a water electrolysis system in accordance with the degree of deterioration of the insulation of the insulating piping. [Means for solving the problem]

[0011] To achieve the above object, one aspect of the present invention provides a water electrolysis system including one or more water electrolysis stacks, insulating piping that electrically insulates the water electrolysis stack from piping, a DC power supply that supplies DC power to the water electrolysis stack to drive the stack, a current measurement unit that measures a leakage current flowing through the insulating piping, and a control device that controls an output of the DC power supply. The control device displays a measurement value of the leakage current flowing through the insulating piping measured by the current measurement unit on a display unit, and controls the DC power supplied to the water electrolysis stack based on the measurement value of the leakage current. [Effects of the Invention]

[0012] According to at least one aspect of the present invention, a leakage current flowing through an insulating pipe that electrically insulates a water electrolysis stack from the piping is measured. Then, a deterioration in the insulation of the insulating pipe is detected from the measured leakage current value, and the amount of power supplied to the water electrolysis stack is controlled. In this way, it is possible to evaluate the soundness of the insulating pipe and control the operation of the water electrolysis system in accordance with the degree of deterioration in the insulation of the insulating pipe. Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiments of the invention. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing a schematic configuration example of a water electrolysis system according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating an example of the hardware configuration of each device constituting a water electrolysis system according to a first embodiment of the present invention. [Figure 3] FIG. 1 is a diagram showing an example of the configuration of ceramic insulating piping used in a water electrolysis system according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing an example of the configuration of an insulating resin pipe used in a water electrolysis system according to a first embodiment of the present invention. [Figure 5] 4 is a graph showing an example of changes over time in leakage current flowing through insulating pipes in the water electrolysis system according to the first embodiment of the present invention. [Figure 6]FIG. 2 is a diagram (part 1) showing a variation of the connection configuration of the water electrolysis stack in the water electrolysis system according to the first embodiment of the present invention. [Figure 7] FIG. 2 is a diagram (part 2) showing a variation of the connection configuration of the water electrolysis stack in the water electrolysis system according to the first embodiment of the present invention. [Figure 8] FIG. 4 is a diagram showing an example of the schematic configuration of an electric circuit in a water electrolysis system according to a second embodiment of the present invention. [Figure 9] FIG. 4 is a diagram showing an example of the schematic configuration of a water electrolysis system according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing an example of the schematic configuration of a water electrolysis system according to a third embodiment of the present invention. [Figure 11] 10 is a flowchart showing an example of a procedure for processing by a water electrolysis system according to a third embodiment of the present invention. [Figure 12] FIG. 10 is a diagram showing a schematic configuration example of a water electrolysis system according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, examples of modes for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the accompanying drawings. In this specification and the accompanying drawings, identical or similar components are given the same reference numerals, and redundant explanations may be omitted or only explanations focusing on the differences may be given. Furthermore, when there are multiple identical or similar components, they may be described using the same reference numerals with different subscripts. Note that when it is not necessary to distinguish between these multiple components, the subscripts may be omitted in the description. The number of each component may be singular or plural unless otherwise specified.

[0015] First Embodiment First, a water electrolysis system according to a first embodiment of the present invention will be described with reference to Figures 1 to 7. The water electrolysis system according to this embodiment is a multi-connection water electrolysis system configured by connecting a plurality of water electrolysis stacks (water electrolytic cells).

[0016] [Outline of water electrolysis system] FIG. 1 is a diagram showing a schematic configuration example of a water electrolysis system according to a first embodiment of the present invention. As shown in FIG. 1, the water electrolysis system 1 mainly includes a water electrolysis stack 10, a DC power supply 11, and auxiliary equipment such as a pure water supply system (not shown), a gas-liquid separator (not shown), and a gas tank (not shown).

[0017] The water electrolysis system 1 includes a water electrolysis stack 10 that electrolyzes water. The water electrolysis stack 10 is connected to a DC power supply 11 and a power cable 12. The DC power supply 11 is configured to supply DC power to the water electrolysis stack 10. Although FIG. 1 illustrates a configuration in which the water electrolysis stack 10 is connected in series to the DC power supply 11, the water electrolysis stack 10 may be connected alone or in parallel. In this figure, water electrolysis stacks 10-1, 10-2, . . . , 10-n are arranged as the water electrolysis stack 10. When there is no need to distinguish between the water electrolysis stacks 10-1, 10-2, . . . , 10-n, they will simply be referred to as "water electrolysis stack 10."

[0018] The water electrolysis stack 10 has a structure in which a plurality of thin components (water electrolysis cells) that electrolyze water to produce hydrogen and oxygen are stacked. The water electrolysis stack 10 is, for example, a device made by stacking water electrolysis cells (not shown) each including a proton-permeable membrane, and produces hydrogen and oxygen using water as a raw material. An example of a water electrolysis stack is a polymer electrolyte membrane (PEM)-type water electrolysis stack.

[0019] Pure water is supplied to the water electrolysis stack 10 from a pure water supply facility (not shown) through a pure water line 13. Oxygen gas and hydrogen gas generated by electrolysis in the water electrolysis stack 10 flow through an oxygen line 14 and a hydrogen line 15, respectively, and are supplied to a gas tank (not shown) or a supply destination (not shown) via a gas-liquid separator (not shown) and a dehumidifier (not shown) provided in each line. In this specification, the pure water line 13, oxygen line 14, and hydrogen line 15 will be simply referred to as "lines" unless they are to be particularly distinguished from one another.

[0020] When the number of water electrolysis cells (not shown) in the water electrolysis stack 10 is increased or when the water electrolysis stacks 10 are connected in series as shown in FIG. 1 , the voltage applied by the DC power supply 11 increases, and the water electrolysis stack 10 is at a high potential. In this case, the maximum voltage applied to the water electrolysis stack 10 is calculated as (number of cells in the water electrolysis stack) x (cell voltage). The voltage of a water electrolysis cell is dependent on the current, temperature, etc., and therefore varies depending on the current flowing through it and the operating temperature. The voltages applied to the water electrolysis stacks 10-1, 10-2, ..., 10-n are measured by voltmeters 18-1, 18-2, ..., 18-n connected to each of the water electrolysis stacks. When the voltmeters 18-1, 18-2, ..., 18-n are not to be distinguished from one another, they will simply be referred to as "voltmeter 18."

[0021] Generally, SUS (Steel Use Stainless Steel) is used for the piping of the pure water line 13, oxygen line 14, and hydrogen line 15 from the viewpoints of preventing pure water leakage, durability, etc. However, if the water electrolysis stack 10 reaches a high potential, and metal piping is directly connected to the water electrolysis stack 10, the metal piping may become electrically conductive, and workers may be electrocuted when they touch auxiliary equipment such as a pure water supply system (not shown) or a gas-liquid separator (not shown).

[0022] Therefore, it is necessary to ensure electrical insulation between the water electrolysis stack 10 and the pure water line 13, oxygen line 14, and hydrogen line 15, and therefore insulated piping is required. In FIG. 1, an insulated piping 16-kw for the pure water line 13, an insulated piping 16-ko for the oxygen line 14, and an insulated piping 16-kh for the hydrogen line 15 are arranged. "k" corresponds to "k" (k = 1 to n) in the water electrolysis stack 10-k. The pure water line 13 and the oxygen line 14 may be made of resin as long as they satisfy the physical specifications. In that case, the present invention applies only to the piping for the hydrogen line 15.

[0023] To explain FIG. 1 more specifically, an insulating pipe 16-1w is arranged on the pure water supply side of the pure water line 13 connected to the water electrolysis stack 10-1, an insulating pipe 16-1o is arranged on the oxygen output side of the oxygen line 14, and an insulating pipe 16-1h is arranged on the hydrogen output side of the hydrogen line 15. An insulating pipe 16-2w is arranged on the pure water supply side of the pure water line 13 connected to the water electrolysis stack 10-2, an insulating pipe 16-2o is arranged on the oxygen output side of the oxygen line 14, and an insulating pipe 16-2h is arranged on the hydrogen output side of the hydrogen line 15. In addition, an insulating pipe 16-nw is arranged on the pure water supply side of the pure water line 13 connected to the water electrolysis stack 10-n, an insulating pipe 16-no is arranged on the oxygen output side of the oxygen line 14, and an insulating pipe 16-nh is arranged on the hydrogen output side of the hydrogen line 15. When there is no need to distinguish between the insulated pipe 16-kw of the pure water line 13, the insulated pipe 16-ko of the oxygen line 14, and the insulated pipe 16-kh of the hydrogen line 15, they will be simply referred to as "insulated pipes 16." Furthermore, since insulation between the water electrolysis stack 10 and the ground is also required, insulators In1 and In2 (an example of an insulator) are provided between the water electrolysis stack 10 and the ground to ensure electrical insulation.

[0024] Even if insulating piping 16 is inserted between the water electrolysis stack 10, which is at a high potential, and the piping at ground potential, a leakage current will flow that corresponds to the volume resistivity of the fluid flowing inside the insulating piping 16 and the potential difference between the water electrolysis stack 10 and the piping at ground potential. That is, if the volume resistivity of the fluid is ρ, the potential difference between the water electrolysis stack 10 and the piping at ground potential is V, the length of the insulating piping 16 is L, and the radius of the piping is r, when the insulating piping 16 is filled with a specific fluid, a leakage current I expressed by equation (1) will flow.

[0025] TIFF2025125652000002.tif18138

[0026] In the case of the insulating pipe 16 provided on the oxygen line 14 or the hydrogen line 15, pure water and oxygen, or pure water and hydrogen, are mixed in the insulating pipe 16. Generally, pure water has a lower volume resistivity than gas. Therefore, in this case, a leakage current roughly proportional to the volume resistivity of the pure water in the insulating pipe 16 flows.

[0027] The leakage current flowing through the insulating pipe 16 causes electrolytic corrosion in the metal housing and metal pipes of the water electrolysis stack 10, resulting in the elution of metal ions. When the eluted metal ions flow into the water electrolysis stack 10, they cause deterioration of the water electrolysis stack 10. Furthermore, when metal ions are precipitated in the insulating pipe 16, the insulating properties deteriorate. If the insulating properties of the insulating pipe 16 deteriorate and dielectric breakdown occurs, the high-potential water electrolysis stack 10 will have a ground fault, making it difficult to continue operating the water electrolysis system 1. Therefore, it is necessary to measure and monitor the leakage current flowing through the insulating pipe 16, and, depending on the amount of leakage current, reduce or stop the output of the DC power supply 11 and perform maintenance before dielectric breakdown occurs.

[0028] In this embodiment, to measure the leakage current flowing through the insulating piping 16 of each line, an ammeter 20 for measuring the leakage current is provided on the opposite side of the insulating piping 16 provided near the water electrolysis stack 10 from the water electrolysis stack 10. In FIG. 1 , the ammeters 20 include an ammeter 20w provided on the pure water line 13, an ammeter 20o provided on the oxygen line 14, and an ammeter 20h provided on the hydrogen line 15. The ammeter 20w measures the leakage current flowing through the insulating piping 16 of the pure water line 13 connected to the water electrolysis stack 10. The ammeter 20o measures the leakage current flowing through the insulating piping 16 of the oxygen line 14 connected to the water electrolysis stack 10. The ammeter 20h measures the leakage current flowing through the insulating piping 16 of the hydrogen line 15 connected to the water electrolysis stack 10. For example, these ammeters may be configured to measure the current value based on the result of measuring the potential difference across a shunt resistor.

[0029] To accurately measure the leakage current flowing through the insulating pipes 16, insulating pipes 17aw, 17ao, and 17ah are provided on the opposite side of the insulating pipes 16 from the water electrolysis stack 10 in each line. Preferably, an ammeter 20 is connected to leakage current measurement locations 24w, 24o, and 24h between each insulating pipe 16 and the insulating pipes 17aw, 17ao, and 17ah to measure the leakage current. The leakage current measurement locations 24w, 24o, and 24h are parts of the metal pipes 30 that constitute each line, and are the locations where the leakage current of each line is to be measured (for example, the current collecting unit 100, which will be described later). When the insulating pipes 17aw, 17ao, and 17ah are not to be distinguished from one another, they are simply referred to as "insulating pipes 17a."

[0030] 1, an insulating pipe 17aw is provided at leakage current measurement location 24w of the pure water line 13, an insulating pipe 17ao is provided at leakage current measurement location 24o of the oxygen line 14, and an insulating pipe 17ah is provided at leakage current measurement location 24h of the hydrogen line 15. By providing the insulating pipes 17aw, 17ao, and 17ah, safety during maintenance is ensured, and the location where leakage current flows in each line can be determined from the positional relationship with the insulating pipe 16. As will be described later, in a second embodiment, by providing multiple insulating pipes designated by the reference numeral 17xx (xx is any alphabet) at key locations on each line, the location where leakage current occurs in each line can be identified.

[0031] Here, the length of the insulating pipe 17a is selected so that the internal resistance of the ammeter 20 for measuring the leakage current is sufficiently smaller than the volume resistance of the fluid flowing through the insulating pipe 17a.

[0032] The leakage current value measured by the leakage current measuring ammeter 20 is then transmitted to the deterioration determination unit 23 via the signal line 21 shown by the dashed line, and is compared with a preset leakage current threshold value in the deterioration determination unit 23. In this embodiment, if a leakage current exceeding the threshold value is detected, the output of the DC power supply 11 is reduced or stopped via the control device 22, and the insulating pipe 16 is maintained. Note that the signal line 21 may be wired or wireless.

[0033] [Hardware configuration of each device that makes up the water electrolysis system] Next, the hardware configuration of each device constituting the water electrolysis system 1 will be described with reference to Fig. 2. Here, an example of the hardware configuration of the computer provided in the control device 22 and the deterioration determination unit 23 will be described.

[0034] FIG. 2 is a diagram showing an example of the hardware configuration of the computer provided in the control device 22 and the deterioration determination unit 23. As shown in FIG. 2, each block may be selected according to the function and purpose of each device. The computer 40 may be, for example, a personal computer or a microcontroller.

[0035] The computer 40 includes a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a non-volatile storage 46, and a communication interface 47. The components within the computer 40 are connected via a system bus so that they can send and receive data to and from each other.

[0036] The CPU 41, ROM 42, RAM 43, and non-volatile storage 46 constitute a control unit. This control unit is used as an example of a computer that controls the operation of the control device 22 or the deterioration determination unit 23. The CPU 41 reads out a software program that realizes the functions of the control device 22 and the deterioration determination unit 23 from the ROM 42, and loads the program into the RAM 43 for execution.

[0037] The ROM 42 is used as an example of a non-volatile memory (recording medium). The ROM 42 stores an OS (Operating System), various parameters, programs for operating each device, etc. The RAM 43 is used as an example of a volatile memory. Variables, parameters, etc. generated during the arithmetic processing of the CPU 41 are temporarily written to the RAM 43. Instead of the CPU 41, another processor such as an MPU (Micro Processing Unit) may be used as the arithmetic processing device.

[0038] The nonvolatile storage 46 is an example of a recording medium and is capable of storing data used by programs and data obtained by executing programs. For example, the nonvolatile storage 46 stores information related to the operation and measurements of the water electrolysis system 1. The nonvolatile storage 46 may also store an OS or programs executed by the CPU 41. Examples of the nonvolatile storage 46 include a hard disk drive (HDD), a solid state drive (SSD), an optical or magnetic disk medium, and a semiconductor memory card. The programs may be provided to each device via a wired or wireless transmission medium such as a local area network (LAN), the Internet, or digital satellite broadcasting.

[0039] The communication interface 47 may be, for example, a network interface card (NIC). The communication interface 47 is configured to be able to transmit and receive various data to and from an external device via a communication network such as a LAN or the Internet to which a terminal is connected, or via a dedicated line. The communication means may be either wireless communication such as Wi-Fi (registered trademark) or LTE (Long Term Evolution) (registered trademark), or wired communication. The communication interface 47 realizes communication via the signal line 21.

[0040] A display device 44 and an input device 45, shown by dashed lines, may be connected to the computer 40. The display device 44 is a monitor such as a liquid crystal display, and displays a GUI screen, the results of processing performed by the CPU 41, etc. The input device 45 generates an input signal in response to an operation by an operator or the like, and outputs the signal to the CPU 41. The input device 45 may be, for example, a mouse or a keyboard, and the operator or the like can operate the input device 45 to input information and instructions. The display device 44 and the input device 45 may be integrated into a touch panel.

[0041] In addition, although the description has been given on the assumption that the control device 22 and the deterioration determination unit 23 each include the computer 40, the control device 22 and the deterioration determination unit 23 may be configured as a single device. For example, the functions of the control device 22 and the deterioration determination unit 23 may be realized by the computer 40 included in the control device 22.

[0042] [Configuration of insulated piping] Next, the configuration of the insulating pipe 16 used in the water electrolysis system 1 according to this embodiment will be described with reference to FIGS. The insulating pipe 16 may be a ceramic pipe or a resin pipe made of polyethylene, vinyl chloride, fluorine-based material, ethylene vinyl alcohol copolymer, glass fiber reinforced plastic, or the like.

[0043] (ceramic insulated piping) FIG. 3 is a diagram showing an example of the configuration of the ceramic insulating pipe 16. As shown in FIG. To ensure electrical insulation between the metal pipes 30, ceramic tubes 50 are arranged as insulating pipes 16. To simplify the leakage current measurement site 24 shown in FIG. 1, a current collecting unit 100 made of a conductor such as metal may be provided between the ceramic tubes 50. Connecting the current collecting unit 100 to a ground wire enables the leakage current flowing through the insulating pipes 16 to be measured with a simple structure. This allows the length of the metal pipes 30 of each line connected to the water electrolysis stack 10 to be shortened. For example, by using the current collecting unit 100 as the leakage current measurement site 24 of the metal pipe 30 (see FIG. 2), the voltage between the current collecting unit 100 and ground can be measured, and the value of the current (leakage current) flowing through the current collecting unit 100 can be calculated from the measured voltage and the resistance of the current collecting unit 100.

[0044] (Resin insulating piping) FIG. 4 is a diagram showing an example of the configuration of the insulating pipe 16 made of resin. When resin is selected as the insulating material, a typical structure is one in which a packing (a sealing member such as an O-ring) is sandwiched between a flange formed at the end of the metal pipe 30 and a flange provided at the end of the resin pipe, and the two are tightened with fastening bolts to form a seal. As with the ceramic insulating pipe, a metal current collecting part 100 may be provided in the middle of the resin pipe.

[0045] 4, a configuration is adopted in which resin pipes 51 and 52 are arranged between metal pipes 30 as insulating pipes 16. A current collecting unit 100 is arranged between resin pipes 51 and 52. More specifically, a packing 32 (sealing member) is sandwiched between a flange 31R of metal pipe 30 and a flange 51L provided on resin pipe 51, and fastened with fastening bolts 33. Further, a packing 32 is sandwiched between flange 31L of metal pipe 30 and flange 52R provided on resin pipe 52, and fastened with fastening bolts 33. Furthermore, a packing 32 is sandwiched between flange 51R of resin pipe 51 and current collecting unit 100, and between flange 52L of resin pipe 52 and current collecting unit 100, and fastened with fastening bolts 33.

[0046] The joints connecting the metal pipe 30 and the resin pipes 51, 52 are not limited to flange structures and may be mechanical joints or other joints that prevent leakage of the flowing fluid. An example of a mechanical joint is a means using a sealing member (packing) and a nut. Mechanical joints are preferably used for pipes with a diameter of 1 inch or less.

[0047] The insulating pipe 16 has been described above, but the insulating pipe 17a can also have the same configuration as the insulating pipe 16 except for the current collecting part 100. However, the current collecting part 100 may be disposed in the insulating pipe 17a and the insulating pipe 17xx shown in Fig. 9, which will be described later.

[0048] [Changes in leakage current over time] Fig. 5 is a graph showing an example of changes over time in the leakage current flowing through the insulating pipes 16 of the water electrolysis system 1. In Fig. 5, the horizontal axis represents the operation time of the water electrolysis stack, and the vertical axis represents the leakage current flowing through the insulating pipes 16.

[0049] As described above, when the water electrolysis stack 10 is operated, leakage current flows through the insulating piping 16, causing electrolytic corrosion of the metal piping. Metal ions eluted by electrolytic corrosion increase the conductivity of the pure water, resulting in a larger leakage current. In particular, the flow rate of pure water is low in the hydrogen line 15. Therefore, if the hydrogen line 15 is designed so that pure water accumulates in the insulating piping 16, the metal ion concentration in the pure water does not decrease, and the leakage current gradually increases. Therefore, as the operation time increases, the leakage current increases as shown in FIG. 5 , and eventually the leakage current value exceeds the output suppression threshold preset by the deterioration determination unit 23. When the leakage current value exceeds the output suppression threshold, the control device 22 suppresses the output of the DC power supply 11. This reduces the voltage applied to the water electrolysis stack 10, thereby reducing the amount of leakage current. Therefore, insulation breakdown of the insulating piping 16 can be prevented or the time until insulation breakdown occurs can be extended. During this time, appropriate maintenance methods can be considered and performed.

[0050] This output suppression threshold may be the same as a threshold (for example, a threshold at the time of initial determination) that is compared with the measured value of the leakage current in step S2 shown in Fig. 11 (to be described later). Furthermore, the output control of the DC power supply 11 according to the leakage current value by the control device 22 in this embodiment may be applied to other embodiments.

[0051] At this time, the control device 22 displays the measurement value of the leakage current flowing through the insulating pipe 16, measured by the ammeter 20 or the like, on the display device 44. Then, the control device 22 controls the amount of DC power supplied from the DC power supply 11 to the water electrolysis stack 10 based on the measurement value of the leakage current.

[0052] [Water electrolysis stack connection configuration] Here, variations in the connection configuration of the water electrolysis stack 10 in the water electrolysis system 1 will be described with reference to Fig. 6 and Fig. 7. Although multiple water electrolysis stacks 10 are shown in Fig. 6 and Fig. 7, only one representative water electrolysis stack 10 is indicated by a reference numeral.

[0053] FIG. 6 is a diagram (part 1) showing a variation of the connection configuration of the water electrolysis stack 10 in the water electrolysis system 1. FIG. 7 is a diagram (part 2) showing a variation of the connection configuration of the water electrolysis stack 10 in the water electrolysis system 1. In the first embodiment (FIG. 1) described above, the water electrolysis stack 10 is connected in series to the DC power supply 11 as shown in FIG. 6A, but the present invention is not limited to this example. Any of the series-parallel configuration shown in FIG. 6B or FIG. 6C, the parallel configuration shown in FIG. 7D, or the single-unit configuration shown in FIG. 7E may also be used.

[0054] In the connection configuration shown in FIG. 6A, five water electrolysis stacks 10 are connected in series to a DC power supply 11. In the connection configuration shown in FIG. 6B, three water electrolysis stacks 10 are connected in parallel, and five of these parallel circuits are connected in series to a DC power supply 11. In the connection configuration shown in FIG. 6C, five water electrolysis stacks 10 are connected in series, and three of these series circuits are connected in parallel to a DC power supply 11. do. In the connection configuration shown in FIG. 7D, three water electrolysis stacks 10 are connected in parallel to a DC power supply 11. In the connection configuration shown in FIG. 7E, one water electrolysis stack 10 is connected to a DC power supply 11.

[0055] As described above, the water electrolysis system (water electrolysis system 1) according to this embodiment includes one or more water electrolysis stacks (water electrolysis stacks 10), insulating piping (insulating piping 16) that electrically insulates the water electrolysis stack from the piping, a DC power supply (DC power supply 11) that supplies DC power to the water electrolysis stack to drive the water electrolysis stack, a current measurement unit (e.g., ammeter 20, current collection unit 100) that measures leakage current flowing through the insulating piping, and a control device (control device 22) that controls the output of the DC power supply. The control device displays the leakage current flowing through the insulating piping measured by the current measurement unit on a display unit and controls the DC power supplied to the water electrolysis stack based on the measured leakage current.

[0056] With the above-described configuration, even when the operating voltage of the water electrolysis stack is high, deterioration in the electrical insulation of the insulating piping can be detected from the measured value of leakage current in the insulating piping that electrically insulates the water electrolysis stack from the piping of each line. Based on the detection result, the control device controls the amount of power supplied to the water electrolysis stack, thereby preventing the entire water electrolysis system from shutting down due to insulation breakdown. In this way, this embodiment makes it possible to evaluate the soundness of the insulating piping and realize operation control in accordance with the degree of deterioration in the insulating properties of the insulating piping.

[0057] <Second embodiment> A water electrolysis system according to a second embodiment of the present invention will be described with reference to Figures 8 and 9. The second embodiment is a modification of the first embodiment, and components that are the same as or similar to those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[0058] In the first embodiment described above, when the amount of leakage current flowing through the insulating pipe 16 exceeds a threshold value preset in the deterioration determination unit 23, the output of the DC power supply is suppressed by a control signal from the control device 22. In this case, the operating current of the entire water electrolysis system is reduced. The present embodiment aims to improve this aspect of operation.

[0059] [Configuration of the electrical circuit in the water electrolysis system] FIG. 8 is a diagram showing an example of the schematic configuration of an electric circuit in a water electrolysis system according to a second embodiment of the present invention. The water electrolysis system 1A shown in Fig. 8 has a configuration in which three water electrolysis stacks 10 are connected in parallel, and the three parallel circuits are connected in series to a DC power supply 11. The water electrolysis system 1A has a configuration in which a circuit switching unit 61 is provided on the positive electrode side of the water electrolysis stack 10, and a circuit switching unit 62 is provided on the negative electrode side thereof. The circuit switching units 61 and 62 are, for example, means capable of connecting and disconnecting a power transmission line, such as a disconnector or a switch. The circuit switching units 61 and 62 can be the same type of device.

[0060] In this embodiment, similar to the first embodiment, when the amount of leakage current flowing through the insulating pipe exceeds a threshold value preset in the deterioration determination unit 23, the control device 22 opens the circuit switching units 61, 62 to disconnect the water electrolysis stack 10b having the deteriorated insulating pipe from the electric circuit. After it is confirmed that the potential of the water electrolysis stack 10b having the deteriorated insulating pipe has sufficiently decreased, the deteriorated insulating pipe can be maintained. With this configuration, the water electrolysis stack 10b to be maintained can be separated from the electric circuit and insulated from the high voltage flowing through the power cable 12. Furthermore, in the case of a water electrolysis system having multiple water electrolysis stacks 10, it is not necessary to shut down the entire system.

[0061] In the example of Fig. 8, the circuit switching units 61, 62 are connected to each of the nine water electrolysis stacks 10, but the circuit switching units 61, 62 may be provided collectively for each maintenance unit of the water electrolysis stacks 10. For example, in the connection configuration of Fig. 6C, a series circuit of five water electrolysis stacks 10 is used as a maintenance unit (disconnection unit), and the circuit switching units 61, 62 are provided for each maintenance unit (disconnection unit). That is, for each series circuit of five water electrolysis stacks 10, the circuit switching unit 61 is connected to the positive electrode side of the DC power supply 11, and the circuit switching unit 62 is connected to the negative electrode side of the DC power supply 11. In the connection configuration of Fig. 6C, three circuit switching units 61 and three circuit switching units 62 are used.

[0062] [Water electrolysis system configuration] FIG. 9 is a diagram illustrating a schematic configuration example of a water electrolysis system 1A according to a second embodiment. The water electrolysis system 1A has a configuration that is basically the same as that of the water electrolysis system 1 according to the first embodiment (see FIG. 1 ). The water electrolysis system 1A differs from the water electrolysis system 1 according to the first embodiment in that the water electrolysis system 1A is provided with an ammeter for measuring the leakage current flowing through the insulating piping 16 of each line of the water electrolysis stacks 10-1, 10-2, ..., 10-n, and an insulating piping for accurately measuring the leakage current of each water electrolysis stack 10. Although not shown in FIG. 9 , the circuit switching unit 61 and the circuit switching unit 62 shown in FIG. 8 are connected to the insulating piping 16 on the positive electrode side of each water electrolysis stack 10 and the negative electrode side of each water electrolysis stack 10, respectively.

[0063] (Water electrolysis stack 10-1) In FIG. 9, an insulating pipe 17bw is provided on the pure water line 13 between the insulating pipe 16-1w (water electrolysis stack 10-1) and the insulating pipe 16-2w (water electrolysis stack 10-2). An insulating pipe 17bo is provided on the oxygen line 14 between the insulating pipe 16-1o (water electrolysis stack 10-1) and the insulating pipe 16-2o (water electrolysis stack 10-2). An insulating pipe 17bh is provided on the hydrogen line 15 between the insulating pipe 16-1h (water electrolysis stack 10-1) and the insulating pipe 16-2h (water electrolysis stack 10-2).

[0064] An ammeter 20-1w is connected between the insulating pipe 16-1w and the insulating pipe 17bw of the metal pipe 30 of the pure water line 13. An ammeter 20-1o is connected between the insulating pipe 16-1o and the insulating pipe 17ao of the metal pipe 30 of the oxygen line 14. An ammeter 20-1h is connected between the insulating pipe 16-1h and the insulating pipe 17ah of the metal pipe 30 of the hydrogen line 15.

[0065] (Water electrolysis stack 10-2) An insulating pipe 17cw is provided between the insulating pipe 16-2w (water electrolysis stack 10-2) of the pure water line 13 and the insulating pipe 16-3w (not shown) (water electrolysis stack 10-3). An insulating pipe 17co is provided between the insulating pipe 16-2o (water electrolysis stack 10-2) of the oxygen line 14 and the insulating pipe 16-3o (not shown) (water electrolysis stack 10-3) (not shown). An insulating pipe 17ch is provided between the insulating pipe 16-2h (water electrolysis stack 10-2) of the hydrogen line 15 and the insulating pipe 16-3h (not shown) (water electrolysis stack 10-3) (not shown).

[0066] An ammeter 20-2w is connected between the insulating pipe 16-2w and the insulating pipe 17cw of the metal pipe 30 of the pure water line 13. An ammeter 20-2o is connected between the insulating pipe 16-2o and the insulating pipe 17bo of the metal pipe 30 of the oxygen line 14. An ammeter 20-2h is connected between the insulating pipe 16-2h and the insulating pipe 17bh of the metal pipe 30 of the hydrogen line 15.

[0067] (Water Electrolysis Stack 10-n) Furthermore, an insulating pipe 17xw is provided between an insulating pipe 16-xw (not shown) of the pure water line 13 (water electrolysis stack 10-x) and an insulating pipe 16-nw (water electrolysis stack 10-n), where x is (n-1). An insulating pipe 17xo is provided between the insulating pipe 16-xo (not shown) of the oxygen line 14 (water electrolysis stack 10-x (not shown)) and the insulating pipe 16-no (water electrolysis stack 10-n). An insulating pipe 17xh is provided on the hydrogen line 15 between an insulating pipe 16-xh (not shown) (water electrolysis stack 10-x) and an insulating pipe 16-nh (water electrolysis stack 10-n).

[0068] An ammeter 20-nw is connected between the insulating pipe 16-nw and the insulating pipe 17aw of the metal pipe 30 of the pure water line 13. An ammeter 20-no is connected between the insulating pipe 16-no and the insulating pipe 17xo of the metal pipe 30 of the oxygen line 14. An ammeter 20-nh is connected between the insulating pipe 16-nh and the insulating pipe 17xh of the metal pipe 30 of the hydrogen line 15.

[0069] In this way, by providing the insulating pipes 16, 17 and the ammeter 20 at key points in the piping of each line (the pure water line 13, the oxygen line 14, and the hydrogen line 15) for each water electrolysis stack 10, it is possible to measure the leakage current flowing through the insulating pipes 16 of each line for each water electrolysis stack 10. That is, it is possible to measure the leakage current for each insulating pipe 16 arranged on each line of multiple water electrolysis stacks 10. Then, based on the comparison result between the leakage current value and a threshold, it is possible to identify the water electrolysis stack 10 with deteriorated insulation. As a result, the control device 22 can open the circuit switching units 61, 62 corresponding to the water electrolysis stack 10 with deteriorated insulation, and disconnect the water electrolysis stack 10 having the deteriorated insulating pipes 16 from the electric circuit.

[0070] With the above-described configuration, even when the operating voltage of the water electrolysis stack is high, a deterioration in the electrical insulation of the insulating piping can be detected from the measured value of the leakage current in the insulating piping that electrically insulates the water electrolysis stack from the piping of each line. Based on the detection result, the control device controls the amount of power supplied to the water electrolysis stack, thereby preventing the entire water electrolysis system from shutting down due to insulation breakdown. Furthermore, in this embodiment, only the water electrolysis stack with the deteriorated insulating piping can be shut down for maintenance, without shutting down the water electrolysis stack with the normal insulating piping.

[0071] Note that the closer the insulating pipe is to the water electrolysis stack, the more susceptible it is to electrolytic corrosion and the faster its insulation deteriorates. Therefore, in this embodiment and the previously described embodiments, the insulating pipe 16 closest to the water electrolysis stack 10 is assumed to be the object of maintenance, but the insulating pipe 17xx may also be included in the objects of maintenance in addition to the insulating pipe 16.

[0072] <Third embodiment> A water electrolysis system according to a third embodiment of the present invention will be described with reference to Figs. 10 and 11. In the third embodiment, components that are the same as or similar to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. However, the configuration of this embodiment can also be applied to the second embodiment.

[0073] FIG. 10 is a diagram showing a schematic configuration example of a water electrolysis system according to a third embodiment of the present invention. The water electrolysis system 1B according to this embodiment differs from the first and second embodiments in that it includes a display unit 25 for indicating when maintenance should be performed on the insulating pipes 16. The display unit 25 corresponds to the display device 44 shown in FIG. 2 .

[0074] The control device 22 has a function (output processing function) of receiving the result of the deterioration determination of the insulating pipe 16 from the deterioration determination unit 23 and notifying the operator U of the result of the deterioration determination. This notification is performed in the form of a display on the display screen of the display unit 25, but may also be made by a voice message, an alarm sound, or the like. The control device 22 also has an input processing function of generating an input signal in response to an operation of the operator U on the input device 45 (see FIG. 2).

[0075] 11 is a flowchart showing an example of the procedure of the process performed by the water electrolysis system 1B according to this embodiment. The flowchart shown in FIG. 11 includes a flow up to determining when to perform maintenance on the insulating pipe 16.

[0076] After the water electrolysis system 1A starts operating, the deterioration determination unit 23 obtains the amount of leakage current in the insulating pipe 16 using the leakage current measurement ammeter 20 (S1). Since the leakage current in the insulating pipe 16 is expected to increase due to a decrease in insulation caused by electrolytic corrosion, as described above, the measurement may be performed at intervals of several minutes or several hours.

[0077] After measuring the leakage current of the insulating pipe 16, the deterioration determination unit 23 compares (S2) the measurement data of the leakage current with a threshold value (corresponding to a first threshold value in the first measurement) preset in the deterioration determination unit 23. If the amount of leakage current is equal to or less than the threshold value (NO determination in S2), the deterioration determination unit 23 continues measuring the amount of leakage current in step S1.

[0078] On the other hand, if the amount of leakage current is greater than the threshold (YES in S2), the control device 22 displays the maintenance timing for the insulating pipe 16 on the display unit 25 (S3). The control device 22 is an example of an output unit. When the control device 22 determines that the electrical insulation of the insulating pipe 16 has deteriorated, it calculates the maintenance timing before the insulation breakdown of the insulating pipe 16 based on the measured leakage current value, and displays (presents) the maintenance timing on the display unit 25. For example, from the relationship between the rising curve of the leakage current shown in FIG. 5 and the threshold, it is possible to predict the time until the leakage current value greater than the threshold reaches a value that is expected to cause insulation breakdown in the insulating pipe 16. The maintenance timing needs to be set based on this predicted time (time) so that it is a time before the insulation breakdown of the insulating pipe 16 occurs.

[0079] Next, the operator U checks the maintenance timing output on the display unit 25, formulates a maintenance plan (S4), and determines whether to stop operation of the corresponding water electrolysis stack 10 (S5). For example, if the displayed maintenance timing is still far in the future and the measured leakage current value does not indicate that insulation breakdown of the insulating pipe 16 will occur in the near future, the operator U determines to continue operation, but if not, determines to stop operation.

[0080] If the operator U determines to continue operation of the water electrolysis stack 10 (NO in S5), the operator U operates the input device 45 (see FIG. 2) to reset the threshold value (second threshold value) for outputting the next maintenance timing (S6). In resetting the threshold value in step S6, the deterioration determination unit 23 may reset the threshold value (second threshold value) by adding a preset current amount (step width) to the current threshold value (first threshold value). After resetting the threshold value, the deterioration determination unit 23 returns to step S1 of measuring the leakage current.

[0081] The first threshold value is a leakage current value that takes into consideration a predetermined tolerance for dielectric breakdown of the insulating pipe 16. For example, if the leakage current value that is expected to cause dielectric breakdown is 100% and the tolerance is 30%, the first threshold value is set to 70% of that leakage current value.

[0082] The second threshold is a leakage current value based on a smaller margin (e.g., 25%) than the first threshold. For example, if the leakage current value at which dielectric breakdown is expected to occur is 100% and the margin is 25%, the second threshold is set to 75% of that leakage current value.

[0083] The second threshold may be set to a current value that requires the water electrolysis system (or a specific water electrolysis stack) to be immediately stopped. In this case, if the leakage current amount is determined to be greater than the threshold in the next determination process of step S2, an alert is output to the display unit 25, and the operator U (or the control device 22) immediately commands the operation to be stopped. At least the first threshold is determined in advance by experiment or simulation and stored in the ROM 42 or the like. The step width of the threshold may also be set in advance and stored in the ROM 42 or the like.

[0084] As described above, in this embodiment, a first threshold value is set as the threshold value used for comparison, taking into consideration the tolerance for the value of leakage current at which insulation breakdown of the insulating pipe 16 is expected to occur, and when the measured value of the leakage current exceeds the first threshold value, a second threshold value is set based on a tolerance smaller than the tolerance of the first value. This setting operation is assumed to be performed by the operator U, but may also be performed automatically by the control device 22 in accordance with the determination result of the leakage current and the threshold value.

[0085] On the other hand, if the operator U determines to stop the operation of the water electrolysis stack 10 (YES determination in S5), the operator U operates the input device 45 to input an operation stop command to the control device 22. As described in the first and second embodiments, the control device 22 stops the power supply from the DC power source 11 in accordance with the operation stop command, or disconnects only the water electrolysis stack 10b (see FIG. 8) with an increased leakage current from the electric circuit (S7). After the processing of step S7, this processing ends.

[0086] Since the water electrolysis stack retains a potential even after it is shut down, the potential is monitored by a voltmeter 18 installed in the water electrolysis stack 10 until the potential drops to prevent electric shock. After confirming that the potential of the water electrolysis stack 10 has dropped, the insulating piping with reduced insulation is replaced or maintenance such as cleaning is performed. In addition, the pure water accumulated in the piping of the hydrogen line 15 of the shut down water electrolysis stack 10 is discharged (or highly pure water is supplied). This prevents the conductivity of the pure water in the insulating piping 16 of the hydrogen line 15 from increasing.

[0087] As described above, the maintenance method for the insulated pipe 16 by the water electrolysis system 1B includes a process (S1) of measuring the leakage current flowing through the insulated pipe 16 using a current measurement unit (ammeter 20, current collector 100, etc.), a process (S2) of comparing the measured value of the leakage current with a threshold value using the deterioration determination unit 23 to determine whether the electrical insulation of the insulated pipe 16 has deteriorated, and a process (S3) of determining, if it is determined that the electrical insulation of the insulated pipe 16 has deteriorated, the timing of maintenance before insulation breakdown of the insulated pipe 16 by the output unit (control device 22) and outputting the maintenance timing to the display unit 25.

[0088] With the above configuration, even if the operating voltage of the water electrolysis stack increases, a decrease in the electrical insulation of the insulating piping, which electrically insulates the water electrolysis stack from the piping of each line, can be detected from the measured leakage current of the insulating piping, and the result can be displayed to the operator U for maintenance. That is, information related to a maintenance plan for the insulating piping can be obtained. Then, the operator U can formulate a maintenance plan based on the displayed content (maintenance timing) and take the necessary measures (step S6 or S7), thereby preventing the entire water electrolysis system from being shut down due to insulation breakdown.

[0089] In this embodiment, the operator U formulates a maintenance plan and determines whether to stop operation based on the maintenance timing output on the display unit 25, but the present invention is not limited to this example. In parallel with outputting the maintenance timing on the display unit 25, the control device 22 may formulate a maintenance plan and determine whether to stop operation based on the maintenance timing and preset conditions.

[0090] <Fourth embodiment> A water electrolysis system according to a fourth embodiment of the present invention will be described with reference to FIG. The water electrolysis system according to this embodiment is an example in which one or more hydroelectric stacks are housed in a large housing (hereinafter referred to as a "container") to simplify installation work.

[0091] In the fourth embodiment, the same or similar parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. However, the configuration of this embodiment can also be applied to the second and third embodiments.

[0092] FIG. 12 is a diagram showing a schematic configuration example of a water electrolysis system according to a fourth embodiment of the present invention. In a water electrolysis system 1C according to this embodiment, two water electrolysis stacks are housed as a set in a container. Fig. 12 shows an example in which two water electrolysis stacks 10-1 and 10-2 are housed in a container 70. In addition, in the water electrolysis system 1C, insulating piping is provided to electrically insulate the equipment inside the container 70 (the water electrolysis stacks 10-1 and 10-2, and the metal piping 30 of each line) from the outside of the container 70.

[0093] On the other hand, outside the container 70 (the pure water supply side), an insulating pipe 17cw is arranged in the pure water line 13, an insulating pipe 17co is arranged in the oxygen line 14, and an insulating pipe 17ch is arranged in the hydrogen line 15. These are the insulating pipes that were also arranged in the second embodiment (see FIG. 9). On the other hand, outside the container 70 (the oxygen and hydrogen discharge side), an insulating pipe 17ao is disposed in the oxygen line 14, and an insulating pipe 17ah is disposed in the hydrogen line 15. These are the insulating pipes that were also disposed in the first embodiment (see FIG. 1).

[0094] The insulating pipes 17a and 17c of these lines electrically insulate the equipment inside the container 70 (the water electrolysis stack 10 and the metal pipes 30) from the metal pipes 30 outside the container 70. This ensures safety when performing maintenance on the equipment inside the container 70.

[0095] As described above, the present invention is not limited to the above-described embodiments, and various other modifications and applications are possible without departing from the spirit of the invention as defined in the claims. For example, the above-described embodiments have been described in detail and specifically to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the components described. Furthermore, it is possible to replace part of the configuration of one embodiment with a component of another embodiment. It is also possible to add a component of another embodiment to the configuration of one embodiment. It is also possible to add, replace, or delete other components from part of the configuration of each embodiment.

[0096] Furthermore, the above-described configurations, functions, processing units, etc. may be partially or entirely realized in hardware, for example, by designing them as integrated circuits, etc. As the hardware, a broad processor device such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used. [Explanation of symbols]

[0097] 1...water electrolysis system, 10, 10-1 to 10-n...water electrolysis stack, 11...DC power supply, 13...pure water line, 14...oxygen line, 15...hydrogen line, 16, 16-1w, 16-1o, 16-1h, 16-2w, 16-2o, 16-2h, 16-nw, 16-no, 16-nh...insulating piping, 17...insulating piping, 18-1, 18-2, 18-n...voltmeter, 19...ammeter, 20, 20w, 20o, 20h...ammeter (for measuring leakage current), 22...deterioration determination unit, 23...control device, 24...leakage current measurement area, 30...metal piping, 40...computer, 44...display device, 100...current collecting unit, In1, In2...insulator

Claims

1. one or more water electrolysis stacks; an insulating pipe that electrically insulates the water electrolysis stack from a pipe; a DC power supply that supplies DC power to the water electrolysis stack to drive the water electrolysis stack; a current measuring unit that measures a leakage current flowing through the insulating pipe; a control device for controlling an output of the DC power supply; A water electrolysis system comprising: The control device displays a measurement value of the leakage current flowing through the insulating pipe measured by the current measuring unit on a display unit, and controls the DC power supplied to the water electrolysis stack based on the measurement value of the leakage current. Water electrolysis system.

2. a degradation determination unit that compares a measurement value of the leakage current flowing through the insulating pipe, measured by the current measurement unit, with a threshold value to determine whether or not the electrical insulation of the insulating pipe has deteriorated, The control device displays on the display unit a result of the determination made by the deterioration determination unit as to whether or not the electrical insulation of the insulating pipe has deteriorated. The water electrolysis system according to claim 1 .

3. a current collecting portion made of a conductor for measuring leakage current flowing through the insulating pipe, the current collecting portion being provided in a part of the insulating pipe; The water electrolysis system according to claim 1 or 2.

4. a circuit switching unit connected to a positive electrode side and a negative electrode side of the DC power supply in the water electrolysis stack and performing an opening and closing operation; When it is determined that the leakage current flowing through the insulating pipe is greater than a threshold value, the control device opens the circuit switching unit to separate the water electrolysis stack from the circuit to which the DC power is supplied. The water electrolysis system according to claim 1 or 2.

5. a first threshold value is set as the threshold value to be compared with the measured value of the leakage current, taking into consideration a tolerance for a value of leakage current at which a dielectric breakdown of the insulating pipe is expected to occur; When the measured value of the leakage current is greater than the first threshold, a second threshold is set based on a tolerance smaller than the tolerance of the first threshold. The water electrolysis system according to claim 4.

6. When it is determined that the electrical insulation of the insulating pipe has deteriorated, the control device calculates the maintenance timing before the insulation of the insulating pipe breaks down, and displays the maintenance timing on the display unit. The water electrolysis system according to claim 5 .

7. an input unit for inputting a command for DC power to be supplied to the water electrolysis stack to the DC power source. The water electrolysis system according to claim 1 .

8. An insulator is provided to insulate the housing of the water electrolysis stack from the ground. The water electrolysis system according to claim 1 .

9. A maintenance method for insulating piping in a water electrolysis system including one or more water electrolysis stacks, insulating piping that electrically insulates the water electrolysis stack from piping, a DC power supply that supplies DC power to the water electrolysis stack to drive the water electrolysis stack, a current measurement unit, a control device that controls an output of the DC power supply, a deterioration determination unit, and an output unit, comprising: a process of measuring a leakage current flowing through the insulating pipe by the current measuring unit; a process of comparing the measured value of the leakage current with a threshold value by the deterioration determination unit to determine whether or not the electrical insulation of the insulating pipe has deteriorated; and when it is determined that the electrical insulation of the insulating pipe has deteriorated, a process is included in which the output unit calculates a maintenance timing before insulation breakdown of the insulating pipe occurs and outputs the maintenance timing. How to maintain insulated piping.

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