Insulator state early warning method based on full frequency domain leakage current characteristics

Abstract

The invention relates to the technical field of electrical equipment diagnosis, and provides an insulator state early warning method based on full-frequency-domain leakage current characteristics, which can comprehensively reflect the state of an insulator from multiple angles, accurately identify the aging and degradation conditions of the insulator and realize early warning by analyzing the full-frequency-domain leakage current characteristics. Through characteristic stage division of a high frequency band and a low frequency band and by combining comparison of a frequency characteristic value and an intensity value, accurate state evaluation and early warning judgment can be provided in each stage, and careful analysis is performed in each stage from an initial stage to a rapid development stage, so that accidents are prevented. According to the invention, through visual presentation of leakage current characteristics, an insulator state monitoring diagram is formed, frequency and intensity changes of discharge signals are visually displayed, and rapid determination is facilitated. The early warning mechanism is subdivided into two-level early warning and first-level emergency early warning levels, so that timely maintenance of the insulator before fault deterioration is ensured, and the safety and reliability of operation of a power system are improved.

Description

Technical Field

[0001] The invention relates to the technical field of power equipment diagnosis, and in particular to an insulator state early warning method based on full-frequency domain leakage current characteristics. Background Art

[0002] Insulators are widely used in power systems to support transmission lines and prevent current backflow. The insulation outside the power grid is exposed to the external environment for a long time. Under certain meteorological conditions, such as fog, dew, drizzle, ice melting, and snow melting, the conductivity of the insulators will increase, the insulation performance will decrease, and leakage current and surface discharge will easily occur, which may lead to flashover accidents. This will seriously affect the reliable operation of the power system and bring huge losses to economic and social life.

[0003] The leakage current can continuously, intuitively and comprehensively reflect the insulation condition and operation status of the insulator during its operation. At the same time, researchers can analyze the contamination development process by analyzing the characteristic value of the leakage current. Monitoring the insulator leakage current is of great significance for monitoring the aging status of the insulator, preventing the development of local arcs, and ensuring the safe and stable operation of the transmission line.

[0004] The researchers pointed out that time domain parameters such as the peak and pulse of the leakage current cannot directly and effectively reflect the surface state of the insulator and the characteristics of the discharge phenomenon. The method of extracting the characteristic parameters of the leakage current using the fast Fourier transformation (FFT) method has begun to be applied in the research.

[0005] Due to the heating effect of leakage current, the surface temperature of the insulator is unevenly distributed, so a dry area will be generated in the area with higher temperature and faster evaporation of water, and finally a dry zone will be formed. The local electric field distortion in the dry zone will be aggravated. At the same time, the possibility of corona discharge and local arc will be increased. However, traditional harmonic and spectrum analysis methods cannot directly and effectively analyze the relationship between leakage current and temperature, dry zone and local arc.

[0006] Therefore, there is an urgent need for an insulator status early warning method based on the full-frequency domain leakage current characteristics to quickly, comprehensively, promptly and multi-angle reflect the problem of insulator insulation aging status. Summary of the invention

[0007] The purpose of the present invention is to solve the deficiencies of the prior art and to provide an insulator status early warning method based on full-frequency leakage current characteristics, so as to quickly, comprehensively, promptly and multi-angle reflect the insulation aging status of the insulator.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] An insulator state early warning method based on full-frequency domain leakage current characteristics comprises the following steps:

[0010] Step (1), measuring the insulator leakage current;

[0011] Step (2), performing Fourier transform on the leakage current to divide the frequency band into a high frequency band and a low frequency band;

[0012] Step (3), analyzing the leakage current characteristics of the high frequency band and the low frequency band respectively, and recording the frequency characteristic values ​​and corresponding intensities at the initial time and the monitoring time;

[0013] In the low-frequency leakage current characteristic analysis, record the highest frequency f at the initial moment maxL , the highest intensity frequency f 1L and its corresponding intensity H 1L , and the highest frequency f' at the monitoring time maxL and intensity highest frequency f' 2L and f 1L The corresponding intensity H' 1L ;

[0014] Record the highest frequency f at the initial moment maxH , the highest intensity frequency f 1H and its corresponding intensity H 1H , and the highest frequency f' at the monitoring time maxH and intensity highest frequency f' 2H and f 1H The corresponding intensity H' 1H ;

[0015] Step (4), setting the characteristic stages of the high frequency band and the low frequency band;

[0016] Step (5), making an early warning judgment on the insulator state according to the characteristic frequency characteristic value and intensity value of the leakage current in the high frequency band and the low frequency band;

[0017] Step (6), visualization of insulator status.

[0018] Preferably, in the frequency band division in step (2), the low frequency band is 0-1 kHz, and the high frequency band is 1-4 kHz.

[0019] Preferably, in step (4), the H of the low-frequency component of the leakage current in the low-frequency band is 1L / H' 1L The ratio and the highest intensity frequency f' 2L , setting the low-frequency current to three characteristic stages: normal stage, preheating stage, and rapid heating stage;

[0020] According to the high frequency component H of the leakage current in the high frequency band 1H / H' 1H The ratio and the highest intensity frequency f' maxH The high-frequency current is set into three characteristic stages: initial stage, intermittent development stage and rapid development stage.

[0021] Preferably, in the step (5) of early warning judgment of the insulator state:

[0022] If f' 2L >f 1L The insulator is considered to be in the rapid heating stage;

[0023] If f' 2L ≤f 1L , then continue to judge H 1L / H' 1L , if H 1L / H' 1L >1000, the insulator is considered to be in the rapid heating stage;

[0024] If H 1L / H' 1L ≤1000, then continue to judge f' maxL Is it greater than 50Hz? If so, the insulator is in the rapid heating stage; if not, the insulator is in the normal stage.

[0025] Preferably, in the step (5) of early warning judgment of the insulator state:

[0026] If f' maxH >2kHz and H 1H / H' 1H >1000, it is considered that the insulator flashover is in a rapid development period;

[0027] If f' maxH ≤2kHz or H 1H / H' 1H ≤1000, it is considered that the insulator flashover is in the intermittent development period;

[0028] If f' maxH ≤2kHz and H 1H / H' 1H ≤1000, the insulator is considered to be in the initial stage.

[0029] Preferably, in step (6), the insulator state visualization is achieved by the following steps:

[0030] 6.1. Normalize the intensity of the high frequency band and the low frequency band;

[0031] 6.2. Read the top 10 highest frequency values ​​of the leakage current in the entire frequency domain every 5 minutes;

[0032] 6.3. The low frequency band and high frequency band are used as the horizontal axis and vertical axis of the two-dimensional coordinate axis respectively, and a diagonal line is defined. The discharge signal frequency points in different time periods are plotted as an insulator status monitoring diagram according to their high and low frequency bands and intensities.

[0033] Preferably, in the insulator status monitoring diagram, 75% of the points below the diagonal line are in a stable operating state;

[0034] If the points above the diagonal account for 25% to 50%, it is a level 2 warning state;

[0035] When the points above the diagonal account for 50% to 75%, it is a Level 1 emergency warning state;

[0036] When the percentage of points above the diagonal line exceeds 75%, it is an emergency warning state.

[0037] Preferably, in the insulator status monitoring diagram, 75% below the diagonal line to 25% above the diagonal line is collectively referred to as a close monitoring state.

[0038] Preferably, after performing Fourier transform on the leakage current in step (2), a Hanning window function is applied to reduce spectrum leakage.

[0039] The present invention discloses an insulator state early warning method based on full-frequency domain leakage current characteristics, which has the following beneficial effects.

[0040] The present invention can comprehensively and multi-angle reflect the state of the insulator by analyzing the leakage current characteristics of the full frequency domain, accurately identify the aging and deterioration of the insulator, and realize early warning. Through the characteristic stage division of the high frequency band and the low frequency band, and combined with the comparison of the frequency characteristic value and the intensity value, the present invention can provide accurate state evaluation and early warning judgment at each stage, and conduct detailed analysis from the initial stage to the rapid development stage to prevent accidents. The present invention forms an insulator state monitoring diagram through the visualization of the leakage current characteristics, intuitively displays the frequency and intensity changes of the discharge signal, and facilitates rapid judgment. The early warning mechanism is subdivided into a second-level early warning and a first-level emergency early warning level, which helps to ensure that the insulator is maintained in time before the fault worsens, and improves the safety and reliability of the operation of the power system. The method provided by the present invention can timely monitor the development of the leakage current dry zone and the local arc under the condition of only frequency domain transformation, and gives the corresponding thresholds and early warning methods under different frequency bands, which can make reliable judgments on the comprehensive condition of the insulator. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The figure is a schematic diagram of the insulator heating state monitoring process based on the low-frequency leakage current characteristics of the present invention.

[0042] Figure 2The figure is a schematic diagram of the monitoring process of the local arc state of an insulator based on the high-frequency leakage current characteristics of the present invention.

[0043] Figure 3 This is the insulator status monitoring diagram of the present invention. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0045] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are 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 operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0046] Example 1

[0047] The invention discloses an insulator state early warning method based on full-frequency domain leakage current characteristics, and a scenario for performing insulator state early warning.

[0048] like Figure 1 and Figure 2 As shown, an insulator state early warning method based on full-frequency leakage current characteristics includes the following steps:

[0049] Step (1), measuring the insulator leakage current, measuring the insulator leakage current by a Rogowski coil and wirelessly transmitting the measured current to a computer;

[0050] Step (2), performing Fourier transform on the leakage current signal on a computer, converting it into the frequency domain, and applying a Hanning window function to reduce spectrum leakage, while dividing the frequency band into a high frequency band and a low frequency band; the low frequency band is 0-1 kHz, and the high frequency band is 1-4 kHz;

[0051] It is worth noting that the frequency band of leakage current is divided into high-frequency and low-frequency bands with 1kHz as the dividing line because the frequency of continuous current signals is generally up to 3 or 5 times the power frequency. Leakage current signals exceeding 1kHz generally exist in the form of pulses. Using 1kHz as the dividing line can be used to classify the continuous state of leakage current. The presence of a higher frequency band signal of leakage current is a sign of insulator flashover. The total energy of leakage current in the low-frequency stage increases with the increase of humidity. As the conductivity of the insulator increases, the leakage current increases and the insulator heats up.

[0052] Step (3), analyzing the leakage current characteristics of the high frequency band and the low frequency band respectively, and recording the frequency characteristic values ​​and corresponding intensities at the initial time and the monitoring time;

[0053] In the low-frequency leakage current characteristic analysis, record the highest frequency f at the initial moment maxL , the highest intensity frequency f 1L and its corresponding intensity H 1L , and the highest frequency f' at the monitoring time maxL and intensity highest frequency f' 2L and f 1L The corresponding intensity H 1L ;

[0054] Record the highest frequency f at the initial moment maxH , the highest intensity frequency f 1H and its corresponding intensity H 1H , and the highest frequency f' at the monitoring time maxH and intensity highest frequency f' 2H and f 1H The corresponding intensity H' 1H .

[0055] Step (4), setting the characteristic stages of the high frequency band and the low frequency band; based on the H of the low frequency component of the leakage current in the low frequency band 1L / H' 1L The ratio and the highest intensity frequency f' 2L , setting the low-frequency current to three characteristic stages: normal stage, preheating stage, and rapid heating stage;

[0056] Step (5), make an early warning judgment on the insulator status according to the characteristic frequency characteristic value and intensity value of the leakage current in the high frequency band and the low frequency band; if f' 2L >f 1L The insulator is considered to be in the rapid heating stage;

[0057] If f' 2L ≤f 1L , then continue to judge H 1L / H' 1L , if H 1L / H' 1L >1000, the insulator is considered to be in the rapid heating stage;

[0058] If H 1L / H' 1L ≤1000, then continue to judge f' maxL Is it greater than 50Hz? If so, the insulator is in the rapid heating stage; if not, the insulator is in the normal stage;

[0059] According to the high frequency component H of the leakage current in the high frequency band 1H / H' 1H The ratio and the highest intensity frequency f' maxH , setting the high-frequency current in three characteristic stages: initial stage, intermittent development stage, and rapid development stage;

[0060] It should be noted that since the leakage current also contains a large number of pulse components, the pulses are often concentrated in the high-frequency band. The high-frequency band energy analysis in the frequency domain can reflect the contamination condition of the insulator and the increase in the overall energy of the leakage current with the increase in the degree of contamination. There is a sharper spectral peak in the frequency range greater than 1kHz, indicating that a large number of pulses with repetitive frequency have appeared at this time, and they have great energy.

[0061] The degree of contamination of insulators can be characterized by high-frequency band analysis. The idea is similar to that of low-frequency band analysis. First, find the frequency corresponding to the maximum leakage current at the current stage, and then compare it with the initial value (under safe operating conditions) to determine whether the maximum frequency corresponding to the leakage current at the current stage exceeds 2kHz. At the same time, see whether the amplitude corresponding to the maximum frequency in the initial state increases sharply. If these two conditions are met at the same time, it indicates that the insulator flashover is in a rapid development period. If one of them is met, it indicates that the insulator flashover is in an intermittent development period. If neither of them is met, it is considered that there is no flashover phenomenon for the time being.

[0062] Step (5) Early warning judgment of insulator status:

[0063] If f' maxH >2kHz and H 1H / H' 1H >1000, it is considered that the insulator flashover is in a rapid development period;

[0064] If f' maxH ≤2kHz or H 1H / H' 1H ≤1000, it is considered that the insulator flashover is in the intermittent development period;

[0065] If f' maxH ≤2kHz and H 1H / H' 1H ≤1000, the insulator is considered to be in the initial stage.

[0066] The leakage current in both the low-frequency band and the high-frequency band can reflect the health status of the insulator insulation system to some extent, but the joint analysis of the two frequency bands can characterize and explain its operating status, surface contamination and humidity conditions, and can more accurately predict and judge the operating status of the insulator, providing a reference for operators and inspectors on the operating status of the insulator.

[0067] Step (6), visualization of insulator status.

[0068] 6.1. Normalize the intensity of the high frequency band and the low frequency band;

[0069] 6.2. Read the top 10 highest frequency values ​​of the leakage current in the entire frequency domain every 5 minutes;

[0070] 6.3. The low frequency band and high frequency band are used as the horizontal axis and vertical axis of the two-dimensional coordinate axis respectively, and a diagonal line is defined. The discharge signal frequency points in different time periods are plotted as an insulator status monitoring diagram according to their high and low frequency bands and intensities.

[0071] In the insulator status monitoring diagram, 75% of the points below the diagonal line are in stable operation status;

[0072] If the points above the diagonal account for 25% to 50%, it is a level 2 warning state;

[0073] When the points above the diagonal account for 50% to 75%, it is a Level 1 emergency warning state;

[0074] If the points above the diagonal account for more than 75%, it is an emergency warning state;

[0075] In the insulator status monitoring diagram, 75% below the diagonal line to 25% above the diagonal line is collectively referred to as the close monitoring status.

[0076] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The substitution may be a substitution of a part of the structure, device, method step, or a complete technical solution. The equivalent replacement or change according to the technical solution and the inventive concept of the present invention shall be covered within the protection scope of the present invention.

Claims

1. An insulator status early warning method based on full-frequency leakage current characteristics, characterized in that: The steps include: Step (1), measuring the insulator leakage current; Step (2), performing Fourier transform on the leakage current to divide the frequency band into a high frequency band and a low frequency band; Step (3), analyzing the leakage current characteristics of the high frequency band and the low frequency band respectively, and recording the frequency characteristic values ​​and corresponding intensities at the initial time and the monitoring time; In the low-frequency leakage current characteristic analysis, record the highest frequency f at the initial moment maxL , the highest intensity frequency f 1L and its corresponding intensity H 1L , and the highest frequency f' at the monitoring time maxL and intensity highest frequency f' 2L and f 1L The corresponding intensity H' 1L ; Record the highest frequency f at the initial moment maxH , the highest intensity frequency f 1H and its corresponding intensity H 1H , and the highest frequency f' at the monitoring time maxH and intensity highest frequency f' 2H and f 1H The corresponding intensity H' 1H ; Step (4), setting the characteristic stages of the high frequency band and the low frequency band; Step (5), making an early warning judgment on the insulator state according to the characteristic frequency characteristic value and intensity value of the leakage current in the high frequency band and the low frequency band; Step (6), visualization of insulator status.

2. The insulator status early warning method based on full-frequency leakage current characteristics according to claim 1, characterized in that: In the frequency band division in step (2), the low frequency band is 0-1 kHz, and the high frequency band is 1-4 kHz.

3. The insulator status early warning method based on full-frequency leakage current characteristics according to claim 1, characterized in that: In the step (4), the low frequency component H of the leakage current in the low frequency band is 1L / H' 1L The ratio and the highest intensity frequency f' 2L , setting the low-frequency current to three characteristic stages: normal stage, preheating stage, and rapid heating stage; According to the high frequency component H of the leakage current in the high frequency band 1H / H' 1H The ratio and the highest intensity frequency f' maxH The high-frequency current is set into three characteristic stages: initial stage, intermittent development stage and rapid development stage.

4. The insulator status early warning method based on full-frequency leakage current characteristics according to claim 1, characterized in that: Step (5) Early warning judgment of insulator status: If f' 2L >f 1L The insulator is considered to be in the rapid heating stage; If f' 2L ≤f 1L , then continue to judge H 1L / H' 1L , if H 1L / H' 1L >1000, the insulator is considered to be in the rapid heating stage; If H 1L / H' 1L ≤1000, then continue to judge f' maxL Is it greater than 50Hz? If so, the insulator is in the rapid heating stage; if not, the insulator is in the normal stage.

5. The insulator status early warning method based on full-frequency leakage current characteristics according to claim 1, characterized in that: In the step (5) of early warning judgment of the insulator status: If f' maxH >2kHz and H 1H / H' 1H >1000, it is considered that the insulator flashover is in a rapid development period; If f' maxH ≤2kHz or H 1H / H' 1H ≤1000, it is considered that the insulator flashover is in the intermittent development period; If f' maxH ≤2kHz and H 1H / H' 1H ≤1000, the insulator is considered to be in the initial stage.

6. The insulator status early warning method based on full-frequency leakage current characteristics according to claim 1, characterized in that: In step (6), the insulator state visualization is achieved by the following steps: 6.

1. Normalize the intensity of the high frequency band and the low frequency band; 6.

2. Read the top 10 highest frequency values ​​of the leakage current in the entire frequency domain every 5 minutes; 6.

3. The low frequency band and high frequency band are used as the horizontal axis and vertical axis of the two-dimensional coordinate axis respectively, and a diagonal line is defined. The discharge signal frequency points in different time periods are plotted as an insulator status monitoring diagram according to their high and low frequency bands and intensities.

7. The insulator state early warning method based on full-frequency leakage current characteristics according to claim 1, characterized in that: In the insulator status monitoring diagram, 75% of the points below the diagonal line are in a stable operating state; If the points above the diagonal account for 25% to 50%, it is a level 2 warning state; When the points above the diagonal account for 50% to 75%, it is a Level 1 emergency warning state; When the percentage of points above the diagonal line exceeds 75%, it is an emergency warning state.

8. The insulator status early warning method based on full-frequency leakage current characteristics according to claim 1, characterized in that: In the insulator status monitoring diagram, 75% below the diagonal line to 25% above the diagonal line is collectively referred to as a close monitoring state.

9. The insulator status early warning method based on full-frequency leakage current characteristics according to claim 1, characterized in that: In the step (2), after Fourier transforming the leakage current, a Hanning window function is applied to reduce spectrum leakage.

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