Deterioration detection device and deterioration detection method

Abstract

This simple device enables continuous monitoring of partial discharges. [Solution] A deterioration determination device for determining the deterioration of components of high-voltage electrical equipment, comprising: a metal test piece that corrodes upon contact with nitric acid; a power supply unit that applies a voltage between one end and the other end of the metal test piece; a detection unit that detects a current or voltage in a closed circuit passing through the metal test piece and the power supply unit; and a determination unit that determines the deterioration of the component according to the current or voltage detected by the detection unit.

Description

Technical Field

[0001] The present invention relates to a deterioration determination device and a deterioration determination method for determining the deterioration of members of high-voltage electrical equipment.

Background Art

[0002] In high-voltage electrical equipment such as high-voltage or extra-high-voltage power receiving and distributing equipment and electric motors, in order to prevent accidents, predictive maintenance that focuses on the deterioration of equipment and precursor phenomena that cause accidents occurring in high-voltage electrical equipment and takes countermeasures in advance is important.

[0003] In high-voltage electrical equipment, partial discharge may occur when the insulation performance inside the equipment deteriorates. Partial discharge is a discharge from the nanosecond order to the millisecond order, also called microdischarge, and is called surface discharge, corona discharge, silent discharge, etc. depending on the occurrence form.

[0004] In partial discharge, since the movement of electrons is restricted, the discharge stops without progressing to arc discharge. Therefore, even if partial discharge occurs, there are no functional problems in high-voltage electrical equipment. However, if partial discharge occurs repeatedly, there is a problem that the members used in high-voltage electrical equipment gradually deteriorate and eventually lead to equipment damage and accidents.

[0005] For example, when partial discharge occurs repeatedly, the insulator of high-voltage electrical equipment gradually deteriorates and the insulation performance decreases. As a result, arc discharge occurs, and accidents such as short circuits and ground faults of power receiving and distributing equipment occur.

[0006] In addition to insulators, metal members used in high-voltage electrical equipment also deteriorate when partial discharge occurs repeatedly. For example, in high-voltage electrical equipment, metal members (fittings) are used for cable connection and fixation, but if these fittings are damaged due to deterioration, they can cause various accidents.

[0007] Therefore, in order to detect the deterioration of various components used in high-voltage electrical equipment such as power distribution equipment and motor stators, a technology has been proposed that focuses on partial discharge and determines the deterioration of components by detecting the occurrence of partial discharge.

[0008] For example, Patent Document 1 proposes a rotating machine diagnostic system that acquires a partial discharge signal distribution using a sensor attached to the rotating machine and determines the shape of the partial discharge pattern from the partial discharge signal distribution. This system can diagnose the insulation state of the rotating machine.

[0009] Patent Document 2 proposes a gas detection device for measuring the concentration of ozone or nitrogen oxides generated in the semiconducting layer constituting the stator coil of a rotating machine. This gas detection device can detect the gas generated by surface discharge due to the deterioration of the semiconducting layer, and as a result, it is possible to monitor the deterioration of the semiconducting layer.

[0010] Furthermore, Patent Document 3 proposes an electric motor system in which a discharge detection material such as potassium iodide is placed near the energized part of the electric motor. Since the discharge detection material changes color in reaction with the ozone gas generated by the discharge, the occurrence of a discharge can be detected indirectly. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2018-072304 [Patent Document 2] Japanese Patent Publication No. 2020-139811 [Patent Document 3] Japanese Patent Publication No. 2021-132480 [Overview of the project] [Problems that the invention aims to solve]

[0012] However, the conventional technologies described above had the following problems.

[0013] The rotating machinery diagnostic system proposed in Patent Document 1 requires a current transformer to be installed in the main circuit to detect minute current fluctuations caused by partial discharge. Therefore, ancillary equipment is needed to isolate and remove noise, resulting in a high overall system cost.

[0014] The gas detection device proposed in Patent Document 2 measures the concentration of ozone or nitrogen oxides based on the color change of a chemical agent. Therefore, periodic replacement of the chemical agent is required, and gas detection cannot be performed during the replacement work. In addition, equipment costs increase because it is necessary to suction the internal atmosphere gas of the rotating equipment containing the generated gas and send it to the container holding the chemical agent.

[0015] Similarly, in the electric motor system proposed in Patent Document 3, ozone is detected based on the discoloration of a discharge detection material such as potassium iodide, requiring periodic replacement of the discharge detection material. Furthermore, ozone is unstable in air and gradually decomposes. Therefore, depending on the timing, it may be difficult to detect partial discharges.

[0016] The present invention aims to solve the above problems by continuously monitoring the occurrence of partial discharge using a simple device and determining the deterioration of components of high-voltage electrical equipment based on that monitoring. [Means for solving the problem]

[0017] The gist of the present invention is as follows:

[0018] 1. A deterioration determination device for determining the deterioration of components of high-voltage electrical equipment, Metal test pieces that corrode upon contact with nitric acid, A power supply unit that applies voltage between one end and the other end of the metal test piece, A detection unit for detecting current or voltage in a closed circuit passing through the metal test piece and the power supply unit, A determination unit that determines the deterioration of the member according to the current or voltage detected by the detection unit, A deterioration determination device including

[0019] 2. The deterioration determination device according to item 1 above, wherein the metal test piece is copper or a copper alloy.

[0020] 3. The deterioration determination device according to item 1 or 2 above, wherein the detection unit includes at least one of a current measuring device and a relay.

[0021] 4. The deterioration determination device according to any one of items 1 to 3 above, wherein the power supply unit is a DC power supply.

[0022] 5. The deterioration determination device according to any one of items 1 to 4 above, further comprising an alarm that issues an alarm when the determination unit determines that the member has deteriorated.

[0023] 6. A deterioration determination method for determining the deterioration of a member of high-voltage electrical equipment using the deterioration determination device according to any one of items 1 to 5 above.

Advantages of the Invention

[0024] According to the present invention, it is possible to continuously monitor the occurrence status of partial discharge with a simple device and determine the deterioration of a member of high-voltage electrical equipment based on this.

Brief Description of the Drawings

[0025] [Figure 1] It is a block diagram showing the configuration of the deterioration determination device in one embodiment of the present invention. [Figure 2] [[ID=A38]]It is a schematic diagram showing an example of the change over time of the current value measured by the current measuring device.

Modes for Carrying Out the Invention

[0026] Hereinafter, the present invention will be specifically described with reference to the drawings. In each figure, the corresponding parts are denoted by the same reference numerals. Note that the following description is for an example of a preferred embodiment of the present invention, and the present invention is not limited to the embodiments described below.

[0027] It should be noted that there seems to be a misnumbering in the original text where "[[ID=A38]]" should probably be "". This has been corrected in the translation for clarity. [Deterioration determination device] Figure 1 is a block diagram showing the configuration of a deterioration detection device in one embodiment of the present invention. The deterioration detection device 100 of this embodiment comprises a metal test piece 10, a power supply unit 20, a detection unit 30, and a determination unit 40. Furthermore, as will be described later, an alarm device 50 may also be optionally included.

[0028] <Components> The deterioration determination device 100 of the present invention is a device for determining the deterioration of components of high-voltage electrical equipment. The component to be determined is not particularly limited and may be any component provided in high-voltage electrical equipment that deteriorates due to partial discharge. Examples of such components include insulators and metal components.

[0029] <Metal test piece> In this invention, a metal test piece 10 is used to continuously monitor the occurrence of partial discharge. Any metal material that corrodes when in contact with nitric acid can be used as the metal test piece 10. The reason for using a metal material that corrodes when in contact with nitric acid will be explained below.

[0030] As mentioned earlier, in partial discharge, electron movement is restricted, so the discharge stops before progressing to arc discharge. However, the electrons that have energy from the partial discharge collide with surrounding oxygen and water molecules, causing the decomposition of oxygen and water molecules. As a result, ozone, reactive oxygen species, hydroxyl radicals (OH radicals), etc. are generated. Because these are highly reactive radicals, they secondarily oxidize organic matter or react with nitrogen to form nitrate ions (NO3). - ) are produced. Then, nitrate ions react with water to produce nitric acid (HNO3).

[0031] For example, when a barrier discharge is induced by applying a 5μs pulse voltage to a gas mixture (80% N2, 20% O2), oxygen molecules decompose into oxygen atoms immediately after the voltage is applied, gradually generating ozone (O3) and reaching equilibrium. Nitrogen and oxygen react to produce NO, which then reacts with oxygen to produce NO2. NO2 then reacts with O3 to form NO3, and NO2 and NO3 react to produce N2O5. Furthermore, if water is present in the air, its dissociation energy is relatively low, making water decomposition (H2O → OH + H) more likely. This water decomposition reaction generates OH radicals. These generated OH radicals react with NO2 to produce HNO3. When a partial discharge occurs, these reactions take place within approximately 0.01 to 100 seconds.

[0032] The methods described in Patent Documents 2 and 3 detect ozone and nitrogen oxides generated by partial discharge as gases, thus detecting partial discharges occurring inside high-voltage electrical equipment as they occur. However, the occurrence of partial discharge is a precursor to a decrease in the insulation performance inside the equipment, and the occurrence of partial discharge does not immediately cause accidents such as short circuits or ground faults in the power distribution equipment. Therefore, although the methods described in Patent Documents 2 and 3 can detect the occurrence of partial discharge, they require periodic replacement of the chemical or discharge detection material, which means that partial discharge may not be detected depending on the timing.

[0033] In contrast, the present invention utilizes the fact that corrosion of a metal test piece gradually progresses due to the action of nitric acid generated by partial discharge, resulting in a change in the resistance value of the metal test piece. Therefore, the effects of partial discharge can be reliably detected. That is, since the corrosion of the metal test piece progresses cumulatively due to partial discharge, the occurrence of partial discharge can be determined by detecting the current or voltage in the closed circuit passing through the metal test piece. Based on the results, the deterioration of components of high-voltage electrical equipment can be determined.

[0034] The material of the metal test piece 10 is not particularly limited, and any metal that corrodes upon contact with nitric acid can be used. Typically, it may be at least one selected from iron, nickel, and copper, as well as their alloys, with copper or copper alloy being preferred. Copper and copper alloys have excellent reactivity and conductivity with nitric acid, and are also relatively inexpensive and readily available.

[0035] As described above, the metal test piece 10 corrodes by reacting with nitric acid, which is generated when partial electrical discharge occurs. As corrosion progresses, the electrical resistance of the metal test piece 10 increases as a result of the formation of corrosion products such as oxides and a decrease in weight (corrosion weight loss). Therefore, the generation of nitric acid can be monitored by detecting the current or voltage in the closed circuit passing through the metal test piece 10.

[0036] The shape of the metal test piece 10 is not particularly limited and may be any shape. Typically, it may be a flat plate, a round bar, a square bar, or the like.

[0037] The dimensions of the metal test piece 10 are not particularly limited. However, the cross-sectional area of ​​the metal test piece 10 is 0.2 mm². 2 If the cross-sectional area is less than 0.2 mm², the change in resistance due to corrosion will be large, which may lead to an overestimation of the degree of deterioration of the material. Therefore, the cross-sectional area is set to 0.2 mm². 2 It is preferable that the above is true. On the other hand, the cross-sectional area is 0.5 mm 2 If the cross-sectional area exceeds 0.5 mm², the change in resistance due to corrosion is small, making it difficult to detect the deterioration of the material early. Therefore, the cross-sectional area is 0.5 mm². 2 The following is preferable:

[0038] Here, the cross-sectional area of ​​the metal test piece 10 refers to the area of ​​the cross-section perpendicular to the direction of current flow of the metal test piece 10. If the area of ​​the metal test piece 10 is not constant, the minimum value of the cross-sectional area at each part of the metal test piece 10 shall be used as the cross-sectional area of ​​the metal test piece 10.

[0039] As described later, the metal test piece 10 needs to be connected to the power supply unit 20 and the detection unit 30 to form a closed circuit, so it can be connected to the power supply unit 20 and the detection unit 30 with wires as appropriate. In this case, the metal test piece 10 may be directly connected to the wire, but it is preferable to provide a clamping part at the end of the wire to make it easier to install and replace the metal test piece 10. For example, a first clamping part is provided at the end of the wire connected to the power supply unit 20, and one end of the metal test piece 10 is clamped by the first clamping part. Also, a second clamping part is provided at the end of the wire connected to the detection unit 30, and the other end of the metal test piece is clamped by the second clamping part. The clamping part may be a structure in which the metal test piece 10 is clamped by multiple members biased by an elastic member such as a spring, or it may be a structure in which the metal test piece 10 is clamped by tightening multiple members with bolts and nuts.

[0040] The installation location of the metal test piece 10 is not particularly limited and can be installed at any location on the high-voltage electrical equipment. If the high-voltage electrical equipment has a housing, such as the cubicle-type high-voltage power receiving equipment described later, the metal test piece 10 can be installed inside the housing.

[0041] While the entire deterioration detection device can be installed inside the high-voltage electrical equipment, it is preferable, as shown in Figure 1, to install only the metal test piece 10 inside the high-voltage electrical equipment 200 and the other equipment (power supply unit 20, detection unit 30, determination unit 40, alarm 50) outside the high-voltage electrical equipment. Alternatively, in addition to the metal test piece 10, at least one of the power supply unit 20, detection unit 30, determination unit 40, and alarm 50 may be installed inside the high-voltage electrical equipment, with the others installed outside.

[0042] <Power supply section> The power supply unit 20 is not particularly limited and any power source can be used. The power supply unit 20 may be either a DC power supply or an AC power supply. Furthermore, a primary battery or a secondary battery may be used as the DC power supply. If the high-voltage electrical equipment 200 has a power supply, that power supply can also be used as the power supply unit 20 of the deterioration determination device 100.

[0043] Furthermore, it is preferable that the power supply unit 20 is a DC power supply. That is, nitrate ions generated by partial discharge accumulate on the anode side of the metal test piece 10, and as a result, corrosion preferentially occurs on the anode side of the metal test piece 10. Therefore, when using DC, changes in current or voltage can be detected more easily than when using AC.

[0044] <Detection Unit> The detection unit 30 detects the current or voltage in the closed circuit passing through the metal test piece 10 and the power supply unit 20. The detection unit 30 may typically be at least one of a current meter and a relay.

[0045] By using an ammeter, the current flowing through the closed circuit can be measured. When measuring the current, the change in electrical resistance due to corrosion of the metal test piece 10 can be continuously measured, thus allowing for continuous monitoring of the occurrence of partial discharge in high-voltage electrical equipment. In this case, the current value data measured by the ammeter can be sent to the determination unit 40.

[0046] On the other hand, any relay capable of detecting changes in current or voltage can be used. For example, a relay that operates when the voltage meets a predetermined condition (voltage detection relay) may be used, or a relay that operates when the current meets a predetermined condition (current relay) may be used. When a relay is used, a signal indicating that the relay has operated (turned ON) is sent to the determination unit 40.

[0047] <Judgment part> The determination unit 40 determines the deterioration of components of the high-voltage electrical equipment according to the current or voltage detected by the detection unit 30.

[0048] For example, if a current measuring instrument is used as the detection unit 30, the determination unit 40 can periodically acquire data on the measured current value and make a determination based on that data. Figure 2 is a schematic diagram showing an example of the change in the current value measured by the current measuring instrument over time. As in this example, the measured current value gradually decreases over time (usually on a monthly or yearly scale). Therefore, for example, if the measured current value falls below a predetermined limit current value, it can be determined that the component has deteriorated.

[0049] The current limit should be predetermined to a current value that does not cause ground faults or burnout of the high-voltage electrical equipment, corresponding to the degree of deterioration of components occurring inside the equipment. The current limit can be set appropriately according to the material, shape, and dimensions of the metal test piece, but it is generally recommended to set the current limit to (0.3~0.5) × A0 relative to the initial current value A0, which is the current value when no corrosion has occurred in the metal test piece. If the current limit is less than 0.3A0, the deterioration of the components will progress to a considerable extent, resulting in a higher risk of ground faults and burnout. On the other hand, if the current limit is greater than 0.5A0, inspections and repairs of the high-voltage electrical equipment will be carried out at a stage where the deterioration of the components is relatively minor, which is not economical.

[0050] Furthermore, the determination unit 40 may determine that the component has deteriorated if the slope (change per unit time) of the measured current value is greater than a preset limit value. This is because the slope increases as the frequency of partial discharge increases.

[0051] On the other hand, when a relay is used as the detection unit 30, the determination unit 40 receives a signal indicating that the relay has operated (turned ON) when the current or voltage meets predetermined conditions. Upon receiving this signal, the determination unit 40 determines that the component has deteriorated. For example, if the relay is a current relay, it is preferable to set the current value at which the current relay operates to 0.3 to 0.5 times the initial current value A0 of the metal test piece before corrosion occurs.

[0052] Furthermore, if the metal test piece 10 corrodes and breaks, current will no longer flow to the relay, and the coil of the relay will become de-energized. Therefore, the deterioration of the components can be determined by utilizing the fact that the make-break state of the relay contacts switches depending on the presence or absence of current.

[0053] Any device capable of performing the above determination can be used as the determination unit 40. Typically, a general-purpose computer or a PLC (programmable logic controller) can be used as the determination unit 40.

[0054] <Alarm> The deterioration detection device 100 may further include an alarm device 50 that issues an alarm when the detection unit 40 determines that a component has deteriorated. When an alarm is issued by the alarm device 50 connected to the detection unit 40, the manager responsible for managing the high-voltage electrical equipment can easily recognize the deterioration of the component. As a result, ground faults and short-circuits in the high-voltage electrical equipment can be prevented.

[0055] Furthermore, the deterioration detection device 100 may also include a display device that displays the detection result from the detection unit 40. The display device connected to the detection unit 40 can inform the manager responsible for managing the high-voltage electrical equipment of the detection result. Based on the detection result, the manager can inspect and repair the high-voltage electrical equipment that has been determined to be deteriorated. This helps to prevent ground faults and short-circuits in the high-voltage electrical equipment.

[0056] A thermometer and / or a hygrometer may be installed inside the high-voltage electrical equipment, and the temperature and humidity inside the equipment measured by these devices may be sent to the determination unit 40. The determination unit 40 may then adjust the determination based on either the temperature or humidity. For example, when making a determination based on current, the current limit value may be corrected according to either the temperature or humidity or both. This is because, even if the frequency of partial discharge is the same, high temperatures inside the high-voltage electrical equipment tend to accelerate corrosion and weight loss of electrode members. Similarly, even if the frequency of partial discharge is the same, high humidity inside the high-voltage electrical equipment tends to increase the number of water molecules attracted to the electrode members, making it easier for nitric acid to be produced and accelerating corrosion.

[0057] <High-voltage electrical equipment> By using such a deterioration detection device, the deterioration of components of high-voltage electrical equipment can be determined. In this invention, high-voltage electrical equipment refers to electrical equipment that has the function of receiving high-voltage or extra-high-voltage electricity. Examples of such high-voltage electrical equipment include power distribution equipment, substations, and electric motors. Power distribution equipment is equipment that distributes high-voltage or extra-high-voltage electricity received from power plants, etc. Substations are equipment that transforms high-voltage or extra-high-voltage electricity to different voltage levels. Electric motors are electric motors that receive high-voltage or extra-high-voltage electricity and convert electrical energy into mechanical energy. All of these pieces of equipment have the function of receiving high-voltage or extra-high-voltage electricity.

[0058] Here, "high voltage" refers to a voltage class of over 750V to 7000V for DC and over 600V to 7000V for AC, while "extra-high voltage" refers to a voltage class of over 7000V for both DC and AC. Equipment receiving high-voltage or extra-high-voltage electricity is prone to deterioration due to partial discharge.

[0059] Examples of high-voltage or extra-high-voltage power receiving equipment include cubicle-type high-voltage power receiving equipment. Cubicle-type high-voltage power receiving equipment is equipment that houses devices such as sectionalizing switches, disconnectors, circuit breakers, transformers, protective relays, control devices, measuring instruments, and low-voltage power distribution equipment in a metal box (enclosure).

[0060] When applying the present invention to a cubicle-type high-voltage power receiving facility, the metal test piece 10 can be installed inside the cubicle-type high-voltage power receiving facility. The installation location is not particularly limited and can be installed near the component whose deterioration you wish to monitor. In particular, it is preferable to install it in either the busbar room or the cable head room, or both. The busbar room is a compartment where busbar conductors that receive power from the power supply side are installed, and the cable head room is a compartment provided for connecting high-voltage cables that have undergone termination processing.

[0061] When installing a metal test piece 10 inside a cubicle-type high-voltage power receiving equipment, it is preferable to install the metal test piece 10 at a distance of 0.2 to 1.0 m from the high-voltage live parts. If the distance is less than 0.2 m, there is a risk of short circuit. Also, if the distance is greater than 1.0 m, it is difficult to secure installation space.

[0062] Furthermore, examples of high-voltage or extra-high-voltage power receiving equipment include electric motors that receive high-voltage or extra-high-voltage electricity and convert electrical energy into mechanical energy. Typically, such electric motors comprise a main body including a rotor, stator, etc., and a frame that houses the main body.

[0063] When applying the present invention to an electric motor, the metal test piece 10 can be placed inside the equipment frame. The placement is not particularly limited and can be placed near the component whose deterioration you wish to monitor. In particular, it is preferable to place it near the stator coil. In some electric motors, a circulating airflow may be configured to flow near the stator coil. In that case, it is preferable to place the metal test piece 10 along the path of the circulating airflow.

[0064] When installing the metal test piece 10 inside the electric motor, it is preferable to install it at a distance of 0.2 to 1.0 m from the stator coil. If the distance is less than 0.2 m, there is a risk of short circuit. Also, if the distance is greater than 1.0 m, it is difficult to secure installation space. [Explanation of Symbols]

[0065] 10 Metal test pieces 20 Power supply section 30 Detection unit 40 Judgment section 50 Alarm 100 Deterioration determination device 200 High-voltage electrical equipment

Claims

1. A deterioration determination device for determining the deterioration of components of high-voltage electrical equipment, Metal test pieces that corrode upon contact with nitric acid, A power supply unit that applies voltage between one end and the other end of the metal test piece, A detection unit for detecting current or voltage in a closed circuit passing through the metal test piece and the power supply unit, A determination unit that determines the deterioration of the member according to the current or voltage detected by the detection unit, A deterioration detection device, including one.

2. The deterioration determination device according to claim 1, wherein the metal test piece is copper or a copper alloy.

3. The deterioration determination device according to claim 1, wherein the detection unit comprises at least one of a current measuring instrument and a relay.

4. The deterioration determination device according to claim 2, wherein the detection unit comprises at least one of a current measuring instrument and a relay.

5. The deterioration determination device according to any one of claims 1 to 4, wherein the power supply unit is a DC power supply.

6. The deterioration determination device according to any one of claims 1 to 4, further comprising an alarm device that issues an alarm when the determination unit determines that the member has deteriorated.

7. The deterioration determination device according to claim 5, further comprising an alarm device that issues an alarm when the determination unit determines that the member has deteriorated.

8. A method for determining deterioration of components of high-voltage electrical equipment, using a deterioration determination device described in any one of claims 1 to 4.

9. A method for determining deterioration of components of high-voltage electrical equipment using the deterioration determination device described in claim 5.

10. A method for determining deterioration of components of high-voltage electrical equipment using the deterioration determination device described in claim 6.

11. A method for determining deterioration of components of high-voltage electrical equipment using the deterioration determination device described in claim 7.

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