Transformer cooling oil metal impurity detection system and method

Abstract

The invention discloses a transformer cooling oil metal impurity detection system and method, and belongs to the technical field of transformer fault detection. The system comprises a microwave heating cavity and a circular tube reactor, the microwave heating cavity is of a hollow columnar structure, through holes are formed in the middle of the top end and the middle of the bottom end of the microwave heating cavity, coupling connectors are symmetrically arranged at preset positions away from the through hole in the middle of the top end, and the coupling connectors are connected with a microwave generator; the circular tube reactor is axially inserted into the microwave heating cavity and penetrates through a through hole in the middle of the top end and a through hole in the middle of the bottom end of the microwave heating cavity, and a thermocouple temperature sensor is arranged in the circular tube reactor and connected with a temperature reading module. According to the invention, microwave heating is adopted, a detection system is simple, a constant magnetic oscillation mode (TM010) is adopted for microwave heating, the consistency of the sample temperature in the axial direction is good, the measurement precision is high, and volume phase measurement is adopted.

Description

Technical Field

[0001] The invention relates to the technical field of transformer fault detection, and in particular to a transformer cooling oil metal impurity detection system and method. Background Art

[0002] As the insulation and cooling medium of the transformer, the quality of transformer cooling oil is directly related to the safe and stable operation of the transformer. Due to the different materials of the transformer windings, cores, stampings, joints, etc., when the transformer is in an abnormal operating state such as overheating or discharge, the metal parts will produce electrochemical corrosion, causing some metal to enter the transformer cooling oil. In addition, during the long-term operation of the submersible pump, due to vibration and other reasons, it is inevitable that there will be stator and rotor sweeping failures. The fine metal particles generated by the friction of the sweeping enter the cooling oil, and further circulation into the winding will cause serious breakdown accidents. Therefore, timely and rapid detection of metal impurities in the transformer cooling oil is helpful to monitor or accurately judge the potential dangers and failures of the transformer, which is conducive to the safe and economical operation of the transformer.

[0003] The regular inspection of transformer cooling oil is mainly carried out by oil chromatograph. Based on the qualitative and quantitative analysis of hydrocarbon gases (such as methane, ethylene, ethane, etc.) dissolved in the cooling oil, the fault type and severity inside the transformer can be indirectly determined. However, the inspection process is complicated and the time is slow, and it is not possible to make timely diagnosis of serious faults such as submersible pump sweeping. The detection method specifically for metal impurities in transformer cooling oil is mainly filtration or adsorption. This method requires a long test cycle, and small particles and low content of metal impurities are not easy to be captured. There are problems such as large measurement errors and poor timeliness. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a transformer cooling oil metal impurity detection system and method, which can quickly determine whether the transformer cooling oil contains metal impurities by measuring the heating rate through microwave heating.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions: In one aspect, the present invention provides a transformer cooling oil metal impurity detection system, comprising a microwave heating cavity and a round tube reactor; The microwave heating cavity is a hollow columnar structure, with through holes in the middle of the top and the middle of the bottom, and coupling connectors are symmetrically arranged at preset positions away from the through holes in the middle of the top, and the coupling connectors are connected to the microwave generator; The circular tube reactor is axially inserted into the microwave heating cavity and penetrates through holes in the middle of the top and the middle of the bottom of the microwave heating cavity. A thermocouple temperature sensor is arranged in the circular tube reactor, and the thermocouple temperature sensor is connected to a temperature reading module. The microwave heating cavity is a hollow structure, which can support the overall strength of the detection system and prevent microwave leakage during the detection process.

[0006] Optionally, a tray for placing the cooling oil to be tested is provided in the circular tube reactor, and a preset distance is provided between the tray and the bottom of the circular tube reactor.

[0007] Optionally, the microwave heating cavity is cylindrical, and its height is less than 2.1 times of its radius, so as to ensure the anti-interference ability of the microwave heating cavity.

[0008] Optionally, the microwave heating cavity adopts a constant magnetic oscillation mode, and the resonance frequency of the microwave heating cavity matches the microwave frequency, so as to ensure that the electric field strength in the microwave heating cavity along the axial direction is uniform, and the electric field strength is related to the radius.

[0009] In another aspect, the present invention provides a method for detecting metal impurities in transformer cooling oil, comprising: Putting the cooling oil sample to be tested into the round tube reactor, and immersing the bottom of the thermocouple sensor with the cooling oil sample to be tested; Turning on the microwave generator to generate constant magnetic oscillation microwaves, the constant magnetic oscillation microwaves are input into the microwave heating cavity through a coupling connector to heat the cooling oil sample to be tested in the round tube reactor; The temperature of the cooling oil sample to be tested is transmitted to the temperature reading module through a thermocouple temperature sensor; When the temperature of the cooling oil sample to be tested reaches a preset final temperature, the microwave generator is turned off, and a time-temperature curve of the cooling oil sample to be tested is plotted to obtain a heating rate of the cooling oil sample to be tested; The cooling oil metal impurity detection result is obtained according to the temperature rise rate of the cooling oil sample to be detected.

[0010] Optionally, obtaining the cooling oil metal impurity detection result according to the heating rate of the cooling oil sample to be detected includes: If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset final temperature is less than the preset first heating rate, the cooling oil sample to be tested does not contain water and metal impurities.

[0011] Optionally, obtaining the cooling oil metal impurity detection result according to the heating rate of the cooling oil sample to be detected includes: If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset first temperature is within the range of the preset first heating rate and the preset second heating rate, and the average heating rate of the cooling oil sample to be tested from the preset first temperature to the preset final temperature is less than the preset first heating rate, then the cooling oil to be tested includes water but does not include metal impurities.

[0012] Optionally, obtaining the cooling oil metal impurity detection result according to the heating rate of the cooling oil sample to be detected includes: If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset final temperature is greater than the preset second heating rate, the cooling oil to be tested includes metal impurities, and the heating rate is directly proportional to the particle mass of the metal impurities.

[0013] Optionally, the method further includes: if the cooling oil to be tested includes metal impurities and the submersible oil pump of the transformer has no faults, then the metal impurities in the cooling oil to be tested come from factors other than the submersible oil pump.

[0014] Optionally, the method further includes: if the cooling oil to be tested includes metal impurities and the submersible oil pump of the transformer is faulty, resampling after a preset time interval, performing metal impurity detection on the new cooling oil sample to be tested, and obtaining a new temperature rise rate; If the new average temperature rise rate is equal to the average temperature rise rate, the metal impurities in the cooling oil to be detected come from the submersible pump; otherwise, the metal impurities in the cooling oil to be detected come from factors other than the submersible pump.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses microwave heating, and the detection system is simple. The microwave heating adopts a constant magnetic oscillation mode (TM010). The sample temperature has good consistency in the axial direction, high measurement accuracy, and adopts bulk phase measurement. Through direct microwave heating detection of the transformer cooling oil sample, according to the difference in microwave absorption capacity of metal particles in the cooling oil, the temperature change after microwave irradiation can quickly determine whether the transformer cooling oil contains metal impurities and determine the source of the metal impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figure shows a schematic structural diagram of a transformer cooling oil metal impurity detection system in one embodiment of the present invention; Figure 2 FIG. 1 is a schematic structural diagram of another embodiment of a transformer cooling oil metal impurity detection system of the present invention; Figure 3The figure is a schematic diagram of a flow chart of a transformer cooling oil metal impurity detection method in one embodiment of the present invention; In the figure: 1-microwave heating cavity; 2-microwave generator; 3-coupling connector; 4-circular tube reactor; 5-thermocouple temperature sensor; 6-temperature reading module. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. The embodiments of the present invention and the technical features in the embodiments may be combined with each other unless there is a conflict.

[0018] The term "and / or" is only a description of the association relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " generally indicates that the related objects are in an "or" relationship.

[0019] Example 1

[0020] like Figure 1 As shown, this embodiment introduces a transformer cooling oil metal impurity detection system, which specifically includes a microwave heating cavity 1, a microwave generator 2, a coupling connector 3, a round tube reactor 4, a thermocouple temperature sensor 5 and a temperature reading module 6.

[0021] In order to support the overall strength of the detection system and prevent microwave leakage, the microwave heating cavity 1 is made of metal aluminum and is shaped like a hollow columnar structure. Through holes are provided in the middle of the top and the middle of the bottom. Coupling connectors 3 are symmetrically provided at preset positions away from the through holes in the middle of the top. The coupling connectors 3 are connected to the microwave generator 2. The coupling connectors 3 are located at one-third of the radius of the axis of the microwave heating cavity 1. Figure 2 In this embodiment, the microwave heating cavity 1 may be cylindrical, and the through hole may be a circular hole.

[0022] In this embodiment, the radius of the microwave heating cavity 1 is designed to be 4.65 cm. At the same time, in order to ensure the anti-interference ability of the microwave heating cavity, the height of the microwave heating cavity 1 is required to be less than 2.1 times its radius value. Under the premise of ensuring the amount of sample placement, the height of the microwave heating cavity 1 is 3-7 cm.

[0023] In order to ensure that the electric field intensity in the microwave heating cavity 1 along the axial direction is uniform, and the electric field intensity is related to the radius, the microwave heating cavity 1 adopts a constant magnetic oscillation mode (TM010), requiring that the resonant frequency of the microwave heating cavity 1 matches the microwave frequency (2.45 GHz), and the microwave generator 2 is used to generate high-frequency microwaves with a resonant frequency of 2.45 GHz. The microwave generator 2 is connected to the top surface of the microwave heating cavity 1 through a coupling connector 3, and the generated high-frequency microwaves with a resonant frequency are input into the microwave heating cavity 1.

[0024] The circular tube reactor 4 is axially inserted into the microwave heating cavity 1 and passes through the circular holes in the middle of the top and the middle of the bottom of the microwave heating cavity 1. A tray for placing the cooling oil to be tested is provided at one third of the distance from the bottom of the circular tube reactor 4 in the vertical direction. The circular tube reactor 4 is a thin-walled container made of quartz material and is a slender cylindrical (height / diameter>50) structure.

[0025] The circular tube reactor 4 is also provided with a thermocouple temperature sensor 5, which is communicatively connected to a temperature reading module 6. The thermocouple temperature sensor 5 is arranged at the center of the circular tube reactor 4 and is used to measure the temperature of the cooling oil sample to be tested in the circular tube reactor 4; the temperature reading module 6 is used to read and record the temperature data of the cooling oil sample to be tested under microwave heating, and to draw a time-temperature curve online to obtain the heating rate data.

[0026] Example 2

[0027] like Figure 3 As shown, this embodiment introduces a transformer cooling oil metal impurity detection method, which is used to quickly detect whether the transformer cooling oil contains metal impurities and further determine the source of the metal impurities, and specifically includes the following steps: Take out 1-3g of cooling oil sample to be tested from the transformer sampling valve. The sampling process ensures the cleanliness of the oil sample and avoids mixing with external impurities. For details on the sampling method, please refer to the prior art.

[0028] The cooling oil sample to be tested is placed in the round tube reactor 4 , and the cooling oil sample to be tested submerges the bottom of the thermocouple sensor 5 .

[0029] The microwave heating cavity 1 is set to a constant magnetic oscillation mode (TM010), the microwave generator 2 is set to a microwave frequency of 2.45 GHz, a microwave power of 100-300 W, and the microwave generator 2 is turned on to generate a constant magnetic oscillation microwave, which is input into the microwave heating cavity 1 through a coupling connector 3 to generate a microwave field with a uniform and stable electric field intensity in the axial direction, thereby heating the cooling oil sample to be tested in the circular tube reactor 4.

[0030] The temperature of the cooling oil sample to be detected is transmitted to the temperature reading module 6 through the thermocouple temperature sensor 5 .

[0031] When the temperature of the cooling oil sample to be detected reaches the preset final temperature, the microwave generator 2 is turned off, and a time-temperature curve of the cooling oil sample to be detected is plotted to obtain the heating rate of the cooling oil sample to be detected, and the cooling oil metal impurity detection result is obtained according to the heating rate of the cooling oil sample to be detected. In this embodiment, the preset final temperature is [150, 200]°C.

[0032] If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset final temperature is less than the preset first heating rate, the cooling oil sample to be tested does not contain water and metal impurities. In this embodiment, the preset first heating rate is 5°C / min.

[0033] In a specific embodiment, the cooling oil sample to be tested heats up relatively evenly from the initial temperature to the final temperature range, and the average heating rate is less than 5°C / min, so it is determined that the transformer cooling oil does not contain moisture and metal impurities, the transformer cooling system has good sealing performance, and the submersible oil pump chamber sweeping failure is ruled out.

[0034] If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset first temperature is within the range of the preset first heating rate and the preset second heating rate, and the average heating rate of the cooling oil sample to be tested from the preset first temperature to the preset final temperature is less than the preset first heating rate, then the cooling oil to be tested contains water but does not contain metal impurities. In this embodiment, the preset second heating rate is 10°C / min.

[0035] In a second specific embodiment, the average heating rate of the cooling oil sample to be tested is within [5, 10]°C / min from the initial temperature to 100°C, and when the temperature is greater than 100°C, the average heating rate is reduced to less than 5°C / min, thereby determining that the transformer cooling oil contains moisture but no metal impurities, and moisture or air is mixed in the transformer cooling system, thereby eliminating the submersible oil pump chamber cleaning failure.

[0036] If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset final temperature is greater than the preset second heating rate, the cooling oil to be tested includes metal impurities, and the heating rate is directly proportional to the particle mass of the metal impurities.

[0037] If the cooling oil to be tested includes metal impurities and the submersible oil pump of the transformer has no faults, the metal impurities in the cooling oil to be tested come from factors other than the submersible oil pump.

[0038] If the cooling oil to be tested includes metal impurities and the submersible oil pump of the transformer is faulty, re-sampling is performed after a preset time interval, and the new cooling oil sample to be tested is tested for metal impurities to obtain a new temperature rise rate; if the new average temperature rise rate is equal to the average temperature rise rate, the metal impurities in the cooling oil to be tested come from the submersible oil pump; otherwise, the metal impurities in the cooling oil to be tested come from factors other than the submersible oil pump.

[0039] In a third specific embodiment, the average heating rate of the cooling oil sample to be tested from the initial temperature to the final temperature range reaches more than 10°C / min, and has a large heating rate in the entire temperature range, so it is determined that the transformer cooling oil contains metal impurities, and the heating rate is positively proportional to the mass fraction of metal particles.

[0040] At this time, under the premise of determining that the transformer cooling oil contains metal impurities, combined with the transformer submersible pump current and vibration test, if the submersible pump current and vibration test show that the submersible pump has no fault, it is determined that the metal impurities in the cooling oil come from other factors besides the submersible pump, and the submersible pump sweeping fault is ruled out; If the submersible pump current and vibration tests show that the submersible pump is faulty, continue to sample the transformer cooling oil after a period of time (1-2 h), and test it again using the above-mentioned microwave heating method to obtain a new heating rate. If the new average heating rate is equal to the average temperature rise rate of the previous test, it is determined that the metal impurities in the cooling oil come from factors other than the submersible pump, and the submersible pump chamber cleaning failure is ruled out. Otherwise, it is determined that the metal impurities in the cooling oil come from the submersible pump and the submersible pump chamber cleaning failure is caused. Example

[0041] Based on Examples 1 and 2, this example introduces a specific experimental design of a method for detecting metal impurities in transformer cooling oil, including the following steps: Take out 2g transformer cooling oil sample from the transformer sampling valve, set the microwave heating cavity 1 to constant magnetic oscillation mode (TM010), set the microwave generator 2 to microwave frequency of 2.45 GHz, and microwave power of 200 W; put 2g cooling oil sample into the circular tube reactor 4, turn on the microwave generator 2, generate constant magnetic oscillation microwave, and input it into the space of the microwave heating cavity 1 through the coupling connector 3 at the top of the cavity of the microwave heating cavity 1, generate a microwave field with uniform and stable electric field intensity along the axial direction, and the cooling oil sample temperature is transmitted to the temperature reading module 6 through the thermocouple temperature sensor 5. When the cooling oil sample temperature reaches the set final temperature of 180℃, microwave heating is stopped, and the temperature reading module 6 draws the time-temperature curve online to obtain the heating rate data. It is found that the cooling oil sample has an average heating rate of 8.5℃ / min from the initial temperature of 25℃ to 100℃, and an average heating rate of 3.4℃ / min from the temperature of 100℃ to 180℃. It is determined that the transformer cooling oil contains water but no metal impurities, and the submersible pump sweeping fault is ruled out.

[0042] Example 4

[0043] Based on Examples 1 and 2, this example introduces another specific experimental design of a method for detecting metal impurities in transformer cooling oil, including the following steps: 3 g transformer cooling oil sample was taken from the transformer sampling valve, microwave heating cavity 1 was set to constant magnetic oscillation mode (TM010), microwave generator 2 was set to microwave frequency of 2.45 GHz, microwave power of 250 W; 3g cooling oil sample is placed in the circular tube reactor 4, the microwave generator 2 is turned on, constant magnetic oscillation microwave is generated, and the microwave is input into the space of the microwave heating cavity 1 through the coupling connector 3 at the top of the microwave heating cavity 1, so as to generate a microwave field with uniform and stable electric field intensity in the axial direction, and the cooling oil sample temperature is transmitted to the temperature reading module 6 through the thermocouple temperature sensor 5. When the cooling oil sample temperature reaches the set final temperature of 180°C, the microwave heating is stopped, and the temperature reading module 6 draws the time-temperature curve online to obtain the heating rate data, and it is found that the heating rate is fast within the final temperature range of 180°C from the initial temperature of 25°C, and the average heating rate reaches 12°C / min, and it is determined that the transformer cooling oil contains metal impurities; further, the submersible pump is tested for current and vibration, and abnormalities are found. After an interval of 1.5h, 3g transformer cooling oil sample is taken out from the transformer sampling valve again, and the above microwave heating test process is repeated. It is found that the average heating rate reaches 14°C / min, indicating that the content of metal impurities in the cooling oil increases with the operation of the submersible pump, and it is determined that the metal impurities in the cooling oil come from the submersible pump, and the submersible pump has a chamber cleaning failure.

[0044] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0045] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0046] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0047] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0048] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A transformer cooling oil metal impurity detection system, characterized in that: It comprises a microwave heating cavity (1) and a circular tube reactor (4); The microwave heating cavity (1) is a hollow columnar structure, with through holes provided in the middle of the top end and the middle of the bottom end, and coupling connectors (3) are symmetrically provided at preset positions away from the through holes in the middle of the top end, and the coupling connectors (3) are connected to the microwave generator (2); The circular tube reactor (4) is axially inserted into the microwave heating cavity (1) and passes through the through holes in the middle of the top end and the middle of the bottom end of the microwave heating cavity (1). A thermocouple temperature sensor (5) is provided in the circular tube reactor (4), and the thermocouple temperature sensor (5) is connected to a temperature reading module (6).

2. The transformer cooling oil metal impurity detection system according to claim 1 is characterized in that: The circular tube reactor (4) is provided with a tray for placing the cooling oil to be tested, and a preset distance is provided between the tray and the bottom of the circular tube reactor (4).

3. The transformer cooling oil metal impurity detection system according to claim 1 is characterized in that: The microwave heating cavity (1) is cylindrical, and its height is less than 2.1 times its radius.

4. The transformer cooling oil metal impurity detection system according to claim 1, characterized in that: The microwave heating cavity (1) adopts a constant magnetic oscillation mode, and the resonance frequency of the microwave heating cavity (1) matches the microwave frequency.

5. A method for detecting metal impurities in transformer cooling oil, characterized in that: include: Putting a cooling oil sample to be tested into a circular tube reactor (4), and immersing the cooling oil sample to be tested at the bottom of the thermocouple sensor (5); Turning on the microwave generator (2) to generate constant magnetic oscillation microwaves, the constant magnetic oscillation microwaves are input into the microwave heating cavity (1) through the coupling connector (3) to heat the cooling oil sample to be tested in the circular tube reactor (4); The temperature of the cooling oil sample to be tested is transmitted to a temperature reading module (6) via a thermocouple temperature sensor (5); When the temperature of the cooling oil sample to be tested reaches a preset final temperature, turning off the microwave generator (2), drawing a time-temperature curve of the cooling oil sample to be tested, and obtaining a heating rate of the cooling oil sample to be tested; The cooling oil metal impurity detection result is obtained according to the temperature rise rate of the cooling oil sample to be detected.

6. The method for detecting metal impurities in transformer cooling oil according to claim 5, characterized in that: According to the heating rate of the cooling oil sample to be tested, the cooling oil metal impurity detection result is obtained, including: If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset final temperature is less than the preset first heating rate, the cooling oil sample to be tested does not contain water and metal impurities.

7. The method for detecting metal impurities in transformer cooling oil according to claim 5, characterized in that: According to the heating rate of the cooling oil sample to be tested, the cooling oil metal impurity detection result is obtained, including: If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset first temperature is within the range of the preset first heating rate and the preset second heating rate, and the average heating rate of the cooling oil sample to be tested from the preset first temperature to the preset final temperature is less than the preset first heating rate, then the cooling oil to be tested includes water but does not include metal impurities.

8. The method for detecting metal impurities in transformer cooling oil according to claim 5, characterized in that: According to the heating rate of the cooling oil sample to be tested, the cooling oil metal impurity detection result is obtained, including: If the average heating rate of the cooling oil sample to be tested from the initial temperature to the preset final temperature is greater than the preset second heating rate, the cooling oil to be tested includes metal impurities, and the heating rate is directly proportional to the particle mass of the metal impurities.

9. The method for detecting metal impurities in transformer cooling oil according to claim 8, characterized in that: The method also includes: if the cooling oil to be detected includes metal impurities and the submersible oil pump of the transformer has no fault, the metal impurities in the cooling oil to be detected come from other factors except the submersible oil pump.

10. The method for detecting metal impurities in transformer cooling oil according to claim 8, characterized in that: The method further includes: if the cooling oil to be tested includes metal impurities and the submersible oil pump of the transformer is faulty, re-sampling after a preset time interval, performing metal impurity detection on the new cooling oil sample to be tested, and obtaining a new temperature rise rate; If the new average temperature rise rate is equal to the average temperature rise rate, the metal impurities in the cooling oil to be detected come from the submersible pump; otherwise, the metal impurities in the cooling oil to be detected come from factors other than the submersible pump.

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