Oil-filled electrical equipment electrical fault severity quantitative evaluation method based on carbon-hydrogen ratio

Abstract

The invention relates to an oil-filled electrical equipment electrical fault severity quantitative evaluation method based on a carbon-hydrogen ratio, and belongs to the field of oil-filled electrical equipment fault monitoring. The method comprises the following steps: acquiring the content of characteristic gas in insulating oil of fault electrical equipment; determining a weighting coefficient of the characteristic gas according to the generation of the characteristic gas; calculating the carbon hydrogen ratio in the characteristic gas according to the content of the characteristic gas and the weighting coefficient of the characteristic gas; and obtaining the fault severity of the oil-filled electrical equipment according to the hydrocarbon ratio of the characteristic gas. According to the method, the defects of a three-ratio method are overcome, and the precision and real-time performance of internal fault diagnosis of the oil-filled electrical equipment are improved.

Description

Technical Field

[0001] The invention belongs to the field of oil-filled electrical equipment fault monitoring and relates to a method for quantitatively evaluating the severity of electrical faults of oil-filled electrical equipment based on a carbon-hydrogen ratio. Background Art

[0002] Oil-filled electrical equipment is widely used in power systems, such as oil-immersed transformers, circuit breakers, current transformers, etc. Its internal faults may cause power supply interruption, equipment damage or even explosion accidents, posing a serious threat to the safe and stable operation of the power grid. Therefore, timely and accurate monitoring and diagnosis of internal faults of oil-filled electrical equipment is an important part of power system maintenance and management.

[0003] At present, the internal fault diagnosis method based on dissolved gas analysis (DGA) in oil is one of the most effective methods recognized internationally. The DGA method uses information such as the type, content and proportion of dissolved gas in oil to determine whether there is a fault inside the equipment and the type of fault. Among them, the three-ratio method is one of the most commonly used DGA methods. It calculates the three ratios of characteristic gases such as methane, ethylene, acetylene, and hydrogen in the dissolved gas in oil (C2H2 / C2H4, CH4 / H2, C2H4 / CH4), and divides them into six areas according to the international standard IEC 60599 or the national standard GB / T 17682, thereby determining the internal fault type of the transformer.

[0004] However, the three-ratio method has some defects and limitations, which are mainly manifested in the following aspects: (1) The three-ratio method can only classify the fault type but cannot reflect the fault severity; (2) The three-ratio method is prone to misjudgment or omission in certain special situations (such as low-energy discharge, mixed faults, multiple faults, etc.); (3) The three-ratio method is a discrete method and cannot continuously monitor and evaluate the development trend of internal faults of the transformer. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for quantitatively evaluating the severity of electrical faults in oil-filled electrical equipment based on the carbon-hydrogen ratio, which overcomes the shortcomings of the three-ratio method and improves the accuracy and real-time performance of internal fault diagnosis of oil-filled electrical equipment.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for quantitatively evaluating the severity of electrical faults of oil-filled electrical equipment based on a carbon-hydrogen ratio, the method comprising the following steps:

[0008] S1. Obtain the characteristic gas content in the insulating oil of the faulty electrical equipment;

[0009] S2. Determine the weighting coefficient of the characteristic gas according to the generation energy of the characteristic gas;

[0010] S3. Calculating the carbon-hydrogen ratio in the characteristic gas according to the characteristic gas content and the weighting coefficient of the characteristic gas;

[0011] S4. Determine the severity of faults in oil-filled electrical equipment based on the carbon-hydrogen ratios of several groups of characteristic gases.

[0012] Further, in step S1, the selected characteristic gases include methane CH4, ethane C2H6, ethylene C2H4, and acetylene C2H2 dissolved in the insulating oil, wherein the characteristic gas content is determined by degassing and gas chromatography in combination, and the process is as follows:

[0013] 1) Sampling: Collect oil samples from the equipment and store them in a sealed container for a period of time;

[0014] 2) Degassing: Separate the oil and gas to remove the dissolved gas in the insulating oil;

[0015] 3) Detection: Use gas chromatograph to separate and detect each gas component;

[0016] 4) Recording: Use a chromatography data processing device or recorder to record the test results and make analysis and calculations.

[0017] Furthermore, in step S2, the weighting coefficient of the corresponding characteristic gas is calculated according to the generation energy of the characteristic gas, and the generation energy of a certain characteristic gas is taken as a reference, and the generation energy of each gas is normalized to obtain the weighting coefficient.

[0018] Further, in step S3, the carbon-hydrogen ratio in each set of characteristic gases is calculated as follows:

[0019]

[0020] In the formula, N(C) i Represents the number of carbon atoms in the chemical formula of the characteristic gas in the ith position, N(H) i represents the number of hydrogen atoms in the chemical formula of the characteristic gas in the ith position; c i is the content of the i-th characteristic gas, w i is the weighting coefficient corresponding to the i-th characteristic gas.

[0021] Further, in step S4, the fault severity is determined according to the carbon-hydrogen ratio, wherein the larger the carbon-hydrogen ratio of the characteristic gas is, the higher the fault severity is, and the corresponding fault severity level is determined according to a preset carbon-hydrogen ratio value range.

[0022] The beneficial effects of the present invention are:

[0023] The present invention quantitatively evaluates the severity of internal faults in oil-filled electrical equipment by the carbon-hydrogen ratio of characteristic gases. The evaluation method based on the carbon-hydrogen ratio of characteristic gases effectively overcomes the defects and limitations of the existing fault diagnosis method based on the three-ratio method, and improves the accuracy and real-time performance of fault diagnosis.

[0024] The method of the present invention is relatively simple to calculate, and can effectively, accurately and continuously evaluate the severity of faults, making up for the shortcomings of the three-ratio method such as missed judgment and discontinuity, and is of great significance for the monitoring and diagnosis of internal discharge faults in oil-filled electrical equipment.

[0025] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0027] Figure 1 It is a schematic diagram of the correlation curve between the weighted carbon-hydrogen ratio of the characteristic gas and the severity of the fault according to the present invention. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0029] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0030] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0031] See also Figure 1 , which is a quantitative assessment method for the severity of electrical faults in oil-filled electrical equipment based on the carbon-hydrogen ratio.

[0032] This embodiment provides a detailed implementation process of a method for quantitatively evaluating the severity of electrical faults of oil-filled electrical equipment based on the carbon-hydrogen ratio. Specifically, the method includes the following steps:

[0033] S1. Obtain the characteristic gas content in the insulating oil of the faulty electrical equipment;

[0034] S2. Determine the weighting coefficient of the characteristic gas according to the generation energy of the characteristic gas;

[0035] S3. Calculating the carbon-hydrogen ratio in the characteristic gas according to the characteristic gas content and the weighting coefficient of the characteristic gas;

[0036] S4. Determine the severity of faults in oil-filled electrical equipment based on the carbon-hydrogen ratios of several groups of characteristic gases.

[0037] In step S1 of the present embodiment, when the insulating oil is destroyed, hydrogen H2, methane CH4, ethane C2H6, ethylene C2H4, and acetylene C2H2 are produced. However, there are two problems with using hydrogen as a fault severity indicator. First, hydrogen can be produced in large quantities through processes unrelated to the fault, such as electrolysis of water and the reaction of acidic substances with galvanized metals. Hydrogen can also come from stray gases in transformer oil. Second, hydrogen is a very small diatomic molecule that escapes from mineral oil at a high speed. Therefore, when evaluating the severity of the fault, the present embodiment only considers hydrocarbon gases methane CH4, ethane C2H6, ethylene C2H4, and acetylene C2H2 as characteristic gases of the present invention.

[0038] The most mature method for detecting dissolved gas components in oil-filled equipment is the method of combining degassing and gas chromatography. That is, first use the degassing equipment to remove the gas in the insulating oil from the oil sample and then detect and analyze the removed gas. The test steps of this method can be summarized as follows:

[0039] 1) Sampling. Collect oil samples from the equipment and take sealing measures to store them for a period of time;

[0040] 2) Degassing. Separate the oil and gas and remove the dissolved gas in the insulating oil;

[0041] 3) Detection. Use gas chromatograph to separate and detect each gas component;

[0042] 4) Record. Use a chromatography data processing device or recorder to record the test results and make analysis and calculations.

[0043] In step S2 of this embodiment, the same volume of methane and acetylene are generated. Although the total gas content is constant, the generation of acetylene requires more energy than the generation of methane, and the severity of the fault is more serious. Therefore, in order to more reasonably characterize the severity of the fault, the relative energy of each gas in Table 2 is used as a weighting coefficient, wherein the weighting coefficient is determined according to the generation energy of the characteristic gas, and the determination method is: taking the generation energy of CH4 as a reference, the generation energy of each gas is normalized to obtain the weighting coefficient, as shown in Table 1.

[0044] Table 1

[0045]

[0046] In step S3 of this embodiment, different characteristic gases have different chemical formulas. In different discharge types, as the discharge intensity increases, the proportion of high-energy gas will increase significantly, and the proportion of low-energy gas will gradually decrease. In the same discharge type, as the discharge intensity increases, the proportion of high-energy gas will gradually increase. That is, as the discharge intensity increases, the proportion of hydrocarbon gas roughly follows the order of CH4→C2H6→C2H4→C2H2. As shown in Table 2, the ratio of the number of carbon atoms to the number of hydrogen atoms (carbon-hydrogen ratio) of different characteristic gases is different. The carbon-hydrogen ratio gradually increases in the order of CH4→C2H6→C2H4→C2H2, which is consistent with the order of characteristic gas proportion. Therefore, based on the above two points, according to the characteristic gas carbon-hydrogen ratio gradually increases with the order of gas relative content percentage, it can be seen that there is a certain correlation between the total carbon-hydrogen ratio of the characteristic gas and the discharge intensity. According to the characteristic that the carbon-hydrogen ratio of hydrocarbon gas gradually increases with the order, it can be seen that the greater the severity of the fault, the higher the carbon-hydrogen ratio of the characteristic gas.

[0047] Table 2

[0048]

[0049] Therefore, in this embodiment, it is proposed to use the characteristic gas weighted carbon-hydrogen ratio to diagnose the severity of the fault, and the expression is as follows:

[0050]

[0051] In the formula, N(C) i Represents the number of carbon atoms in the chemical formula of the characteristic gas in the ith position, N(H) i represents the number of hydrogen atoms in the chemical formula of the characteristic gas in the ith position; c i is the content of the i-th characteristic gas, w i is the weighting coefficient corresponding to the i-th characteristic gas. That is:

[0052]

[0053] Where R CH It represents the ratio of the total number of carbon atoms to the total number of hydrogen atoms of the characteristic gas; wi (i=1~4) and c(CH4), c(C2H6), c(C2H4), c(C2H2) represent the weighting coefficients and contents of methane, ethane, ethylene, and acetylene, respectively.

[0054] In step S4 of this embodiment, the fault severity is divided into the intervals of 0 to 0.4, 0.4 to 0.7, and 0.7 to 1.0. CH When it is between 0 and 0.4, its severity is mild; when it is between 0.4 and 0.7, its severity is moderate; when it is between 0.7 and 1.0, its severity is dangerous.

[0055] This embodiment also verifies the rationality of the method of the present invention based on 130 sets of characteristic gas data, uses the existing energy weighted MEA (EWMEA) and MEA ratio to determine the severity of the transformer fault to calculate the fault severity, and then uses the method of the present invention to calculate the value of the weighted carbon-hydrogen ratio, and then analyzes the correlation between the two, performs linear fitting, and obtains the following: Figure 1 The graph shows the correlation curve between the weighted carbon-hydrogen ratio of the characteristic gas and the severity of the fault. It can be seen from the figure that the goodness of fit R 2 It reaches 0.994, showing a strong correlation, which proves the accuracy and rationality of the evaluation method of the present invention.

[0056] At present, the three-ratio method is widely used to judge the internal fault type of the transformer. Due to the limited ratio coding and the overlap and omission of fault defects and coding, the relationship between the characteristic gas content, ratio and fault severity has not been established. It is difficult to characterize and quantitatively evaluate the fault severity represented by the gas production characteristics, which is not conducive to accurate evaluation of the oil-filled equipment status.

[0057] The quantitative assessment method for the severity of electrical faults in oil-filled electrical equipment based on the carbon-hydrogen ratio proposed in the present invention is relatively simple to calculate, and can effectively, accurately and continuously assess the severity of faults, making up for the shortcomings of the three-ratio method such as missed judgment and discontinuity, and is of great significance for the monitoring and diagnosis of internal discharge faults in oil-filled electrical equipment.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A quantitative evaluation method for the severity of electrical faults in oil-filled electrical equipment based on the carbon-hydrogen ratio, characterized in that: The method comprises the following steps: S1. Obtain the characteristic gas content in the insulating oil of the faulty electrical equipment; S2. Determine the weighting coefficient of the characteristic gas according to the generation energy of the characteristic gas; S3. Calculating the carbon-hydrogen ratio in the characteristic gas according to the characteristic gas content and the weighting coefficient of the characteristic gas; S4. Determine the severity of faults in oil-filled electrical equipment based on the carbon-hydrogen ratios of several groups of characteristic gases.

2. The method for quantitatively evaluating the severity of electrical faults of oil-filled electrical equipment based on the carbon-hydrogen ratio according to claim 1 is characterized in that: In step S1, the selected characteristic gases include methane CH4, ethane C2H6, ethylene C2H4, and acetylene C2H2 dissolved in the insulating oil, wherein the characteristic gas content is determined by degassing and gas chromatography in combination, and the process is as follows: 1) Sampling: Collect oil samples from the equipment and store them in a sealed container for a period of time; 2) Degassing: Separate the oil and gas to remove the dissolved gas in the insulating oil; 3) Detection: Use gas chromatograph to separate and detect each gas component; 4) Recording: Use a chromatography data processing device or recorder to record the test results and make analysis and calculations.

3. The method for quantitatively evaluating the severity of electrical faults of oil-filled electrical equipment based on the carbon-hydrogen ratio according to claim 2 is characterized in that: In step S2, the weighting coefficient of the corresponding characteristic gas is calculated according to the generation energy of the characteristic gas, and the generation energy of a certain characteristic gas is used as a reference to obtain the weighting coefficient after normalizing the generation energy of each gas.

4. A method for quantitatively evaluating the severity of electrical faults of oil-filled electrical equipment based on carbon-hydrogen ratio according to claim 3, characterized in that: In step S3, the carbon-hydrogen ratio in each set of characteristic gases is calculated as follows: In the formula, N(C) i Represents the number of carbon atoms in the chemical formula of the characteristic gas in the ith position, N(H) i represents the number of hydrogen atoms in the chemical formula of the characteristic gas in the ith position; c i is the content of the i-th characteristic gas, w i is the weighting coefficient corresponding to the i-th characteristic gas.

5. A method for quantitatively evaluating the severity of electrical faults of oil-filled electrical equipment based on carbon-hydrogen ratio according to claim 4, characterized in that: In step S4, the fault severity is determined according to the carbon-hydrogen ratio, wherein the larger the carbon-hydrogen ratio of the characteristic gas is, the higher the fault severity is, and the corresponding fault severity level is determined according to a preset carbon-hydrogen ratio value range.

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