Method for warning of three-phase resistive current imbalance of surge protector based on curve similarity

Abstract

This invention provides a method for alarming three-phase resistive current imbalance of surge arresters based on curve similarity, including the following steps: Step 1: Using the measured data of the three-phase resistive current of the surge arrester, calculate the current imbalance before the monitoring point. n The difference between each pair of three-phase resistive currents in the data is divided by the average of each pair; Step 2: Calculate the values ​​before the monitoring point. n Step 3: Calculate the sum of the squares of the pairwise differences of the three-phase resistive currents in the data; n Step 4: Take the pairwise difference of the three-phase resistive currents in this data and divide it by the standard deviation of the pairwise averages; std AB , std AC , std BC The maximum value in the curve is used as the unbalance coefficient of the three-phase resistive current curve. This technical solution can be applied to analyze the similarity of the three-phase resistive current curves of the surge arrester, thereby making a preliminary judgment on the degree of insulation degradation of the surge arrester, issuing a timely three-phase unbalance alarm, and reminding the operation and maintenance unit to take timely action.

Description

Technical Field

[0001] This invention relates to the field of surge arrester technology, and in particular to a surge arrester three-phase resistive current imbalance alarm method based on curve similarity. Background Technology

[0002] Surge arresters are crucial high-voltage electrical devices in power systems, limiting lightning and switching overvoltages. Prolonged exposure to power frequency voltage can lead to defects such as aging of the valve plates and overall moisture absorption. In severe cases, this can result in the arrester losing its protective function and even exploding. Therefore, monitoring the operational status of surge arresters and promptly and effectively detecting aging and moisture defects is of paramount importance for ensuring the safe and stable operation of the power system.

[0003] During operation, surge arresters not only withstand long-term high-frequency voltage but are also affected by the natural environment. The internal valve plates of the surge arrester age. If the arrester's sealing is poor, water can easily seep into the internal valve plates, accelerating insulation deterioration and potentially causing an explosion during operation. Aging of the surge arrester leads to uneven potential distribution within the internal valve plates, causing additional temperature rise and further accelerating aging, creating a vicious cycle. When the insulation of the surge arrester deteriorates, the total current and resistive current, reflecting its insulation performance, will increase significantly, and there may also be significant differences in the data between the three phases. When the monitored data changes drastically or the three-phase differences are large, initial value difference and three-phase imbalance alarms will be triggered. Therefore, monitoring the operating status of surge arresters, analyzing the degree of three-phase imbalance, issuing three-phase imbalance alarms, and promptly and effectively detecting and eliminating surge arrester faults are crucial for the safe and stable operation of the power grid.

[0004] However, in practical applications, due to the small absolute values ​​of the resistive current and total current of the surge arrester, it is greatly affected by external factors, especially weather (temperature, humidity), large differences in the initial value of the surge arrester's resistive current (especially between different manufacturers), and the failure of a certain phase monitoring device. As a result, there are many false alarms in online monitoring, and the single alarm rule has significant limitations and needs further optimization. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for alarming three-phase resistive current imbalance of surge arresters based on curve similarity. This method can analyze the curve similarity of the three-phase resistive current of the surge arrester, thereby making a preliminary judgment on the degree of insulation degradation of the surge arrester, issuing a three-phase imbalance alarm in a timely manner, and reminding the operation and maintenance unit to take timely action.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a three-phase resistive current imbalance alarm method for surge arresters based on curve similarity, comprising the following steps:

[0007] Step 1: Using the measured data of the three-phase resistive current of the surge arrester, calculate the pairwise difference of the three-phase resistive current in the first n data points at the monitoring point, divided by the pairwise average. Taking phases A and B as an example, the calculation formula is: Similarly, BC is calculated. dif(i) and AC dif(i) ;

[0008] Step 2: Calculate the sum of the squares of the pairwise differences of the three-phase resistive currents in the first n data points of the monitoring point, divided by the sum of the squares of the pairwise averages. Taking phases A and B as an example, the calculation formula is: Similarly, R is calculated. BC and R AC ;

[0009] Step 3: Calculate the pairwise difference of the three-phase resistive current in the first n data points of the monitoring point, divided by the standard deviation of the pairwise average. The calculation formula is: Similarly, std is calculated. BC and std AC ;

[0010] Step 4: Get std AB std AC std BC The maximum value in the value is used as the unbalance coefficient of the three-phase resistive current curve, reflecting the degree of similarity between the three-phase resistive current curves, that is:

[0011] std ABC =max{std AB std AC std BC}, std ABC Compared with the threshold, when std ABC When the value is less than the threshold, the surge arrester and monitoring device operate normally and no alarm is issued; when std ABC If the value exceeds the threshold, it is considered that the monitoring device is abnormal or the surge arrester is defective, and an alarm should be issued to remind the operation and maintenance unit to take timely action.

[0012] In a preferred embodiment, the alarm method is based on the following theoretical basis: the three-phase imbalance alarm data caused by weather influences show good consistency in the trend of the three-phase data, while the three-phase resistive current of the monitoring device or surge arrester itself has poor consistency. Therefore, the alarm cause is automatically identified by the curve similarity of the three-phase resistive current data.

[0013] In a preferred embodiment, in step 2, R AB R represents the distance between the parametric curves of phases A and B. AB The smaller the value, the closer the parameter curves of phases A and B are.

[0014] In a preferred embodiment, in step 3, the std AB std BC std AC To measure the similarity between the two-phase resistive current curves, std AB The smaller the value, the more similar the trends of the parameter curves of phases A and B; similarly, std BC The smaller the value, the more similar the trend of the parameter curves of phases B and C; std AC The smaller the value, the more similar the trend of the parameter curves of phases A and C.

[0015] In a preferred embodiment, in step 4, the std ABC The standard deviation (std) represents the degree of similarity between three-phase resistive current curves. AB std AC std BC The maximum value among them; std ABC The smaller the value, the more similar the trend of the parameter curves of phases A, B, and C.

[0016] In a preferred embodiment, the three-phase resistive current imbalance alarm refers to the fact that when the insulation of the surge arrester deteriorates, the resistive current reflecting its insulation performance will increase significantly, and there may also be significant differences in the data between the three phases; when the monitoring data changes drastically or the differences between the three phases are large, a three-phase imbalance alarm is triggered.

[0017] In a preferred embodiment, the three-phase resistive current imbalance alarm refers to the surge arrester alarming when the imbalance coefficient of the three-phase resistive current curve is greater than a certain value, indicating poor consistency in the trend of the three-phase resistive current. The causes of the three-phase imbalance alarm are basically pollution, equipment failure, or surge arrester deterioration, and an alarm should be issued to remind the operation and maintenance unit to handle it in a timely manner.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The three-phase unbalance alarm method only requires calculating the three-phase unbalance coefficient of the surge arrester resistive current and comparing its value with the threshold, making the process simple and convenient.

[0020] 2. It can perform curve trend consistency analysis of the three-phase resistive current of the surge arrester, reducing the false alarm rate of three-phase imbalance caused by factors such as environmental humidity.

[0021] 3. The proposed alarm rule for three-phase resistive current imbalance of surge arresters based on curve similarity can be integrated with other alarm rules to form a comprehensive alarm rule, thereby improving the correct alarm rate of online monitoring of surge arresters and reducing the false alarm rate. Attached Figure Description

[0022] Figure 1This is a flowchart illustrating a preferred embodiment of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] See Figure 1 This invention provides a method for alarming three-phase resistive current imbalance of surge arresters based on curve similarity. The theoretical basis of this method is that the three-phase imbalance alarm data caused by weather influence shows that the three-phase data trend is relatively consistent, while the three-phase resistive current of the monitoring device or surge arrester itself is less consistent. Therefore, the cause of the alarm can be automatically identified by the curve similarity of the three-phase resistive current data.

[0027] The method includes the following steps:

[0028] Step 1: Using the measured data of the three-phase resistive current of the surge arrester, calculate the pairwise difference of the three-phase resistive current in the first n data points at the monitoring point, divided by the pairwise average. Taking phases A and B as an example, the calculation formula is: Similarly, BC can be calculated. dif(i) and AC dif(i) .

[0029] Step 2: Calculate the sum of the squares of the pairwise differences of the three-phase resistive currents in the first n data points of the monitoring point, divided by the sum of the squares of the pairwise averages. Taking phases A and B as an example, the calculation formula is: Similarly, R can be calculated. BC and R AC .

[0030] Wherein, the R AB The parametric curve distance between phases A and B is represented by R, which borrows the idea from the Friesian distance. AB The smaller the value, the closer the parameter curves of phases A and B are.

[0031] Step 3: Calculate the pairwise difference of the three-phase resistive current in the first n data points of the monitoring point, divided by the standard deviation of the pairwise average. The calculation formula is: Similarly, std can be calculated. BC and std AC .

[0032] Wherein, std AB std BC std AC To measure the similarity between the two-phase resistive current curves, std AB The smaller the value, the more similar the trends of the parameter curves of phases A and B; similarly, std BC The smaller the value, the more similar the trend of the parameter curves of phases B and C; std AC The smaller the value, the more similar the trend of the parameter curves of phases A and C.

[0033] Step 4: Get std AB std AC std BC The maximum value in std is used as the unbalance coefficient of the three-phase resistive current curve, reflecting the degree of similarity between the three-phase resistive current curves, i.e.: std ABC =max{std AB std AC std BC}, std ABC Compared to the threshold (0.05), when std ABC When std < 0.05, the three-phase imbalance is considered to be caused by fluctuations in environmental parameters such as weather; the surge arrester and monitoring device are operating normally and no alarm is issued; when std ABC When the value is ≥0.05, it is considered that the monitoring device is abnormal or the surge arrester is defective, and an alarm should be issued to remind the operation and maintenance unit to take timely action.

[0034] The three-phase resistive current imbalance alarm refers to the situation where, when the insulation of the surge arrester deteriorates, the resistive current, which reflects its insulation performance, will increase significantly, and there may also be significant differences in the data between the three phases. A three-phase imbalance alarm is triggered when the monitoring data changes drastically or the differences between the three phases are large.

[0035] When the imbalance coefficient of the three-phase resistive current curve is greater than a certain value, the trend consistency of the three-phase resistive current is poor, and the surge arrester alarms. The causes of three-phase imbalance alarms are basically pollution, equipment failure, or surge arrester deterioration. An alarm should be issued to remind the operation and maintenance unit to deal with it in a timely manner.

[0036] The following example, a 110kV three-phase surge arrester in XX City, XX Province in 2022, further illustrates the beneficial effects of the present invention.

[0037] 1) Obtain the resistive current data of a 110kV three-phase surge arrester in XX City, XX Province, as shown in Table 1;

[0038] 2) Calculate the pairwise difference of the three-phase resistive current in the first 6 data points of the monitoring point, divided by the pairwise average value AB. dif(6) BC dif(6) and AC dif(6) The results are shown in Table 2.

[0039] 3) Calculate the sum of the squares of the pairwise differences of the three-phase resistive currents in the first 6 data points of the monitoring point, divided by the sum of the squares of the pairwise averages, R. AB R BC and R AC The results are shown in Table 3.

[0040] 4) Calculate the pairwise difference of the three-phase resistive current in the first 6 data points of the monitoring point, divided by the standard deviation (std) of the pairwise average. AB std BC and std AC The results are shown in Table 3.

[0041] 5) Get std AB std AC std BC The maximum value is used as std ABC Get std ABC =0.0522>0.05, thus triggering a three-phase imbalance alarm. After on-site inspection and verification, it was found that the B-phase surge arrester itself was abnormal. After power outage and replacement of the B-phase surge arrester, the data returned to normal. The alarm situation and the on-site situation showed good consistency.

[0042] Table 1

[0043]

[0044] Table 2

[0045]

[0046] Table 3

[0047]

[0048] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for warning of three-phase resistive current imbalance of a surge arrester based on curve similarity, characterized in that, The method comprises the following steps: Step 1: Using the measured data of three-phase resistive current of the lightning arrester, the two-by-two difference divided by the two-by-two average of the three-phase resistive current in the previous n data of the monitoring point is calculated, taking phases A and B as an example, the calculation formula is: , and BC dif(i) and AC dif(i) are calculated in the same way. Step 2: Calculate the sum of the square of the pairwise difference divided by the pairwise average of the three-phase resistive current in the last n data of the monitoring point, taking phases A and B as an example, the calculation formula is: , and R BC and R AC are calculated in the same way; R AB represents the parameter curve distance of phases A and B. Step 3: Calculate the standard deviation of the pairwise difference divided by the pairwise average of the three-phase resistive current in the last n data of the monitoring point, the calculation formula is: , and std BC and std AC are calculated in the same way; Step 4: Take the maximum value in std AB , std AC , std BC as the unbalance coefficient of the three-phase resistive current curve, reflecting the degree of similarity between the three-phase resistive current curves, that is: , std ABC is compared with a threshold value, when std ABC is less than the threshold value, the operating state of the lightning arrester and the monitoring device is normal, and no alarm is issued; when std ABC is greater than the threshold value, it is considered that the monitoring device is abnormal or the lightning arrester has defects, and an alarm should be given to remind the operation and maintenance unit to deal with it in time; The theoretical basis of the alarm method is that the three-phase unbalanced alarm data caused by weather influence has good consistency in the trend of three-phase data, while the three-phase resistive current consistency of the monitoring device or the lightning arrester itself is poor. Therefore, the alarm reason is automatically identified by the curve similarity of the three-phase resistive current data.

2. The method for warning of three-phase resistive current imbalance of a surge protector based on curve similarity according to claim 1, characterized in that, In step 2, R AB The smaller, the closer the parameter curve distance between the two phases A and B represents.

3. The method for warning of three-phase resistive current imbalance of a surge protector based on curve similarity according to claim 1, characterized in that, std AB , std BC , std AC is the similarity degree between the two-phase resistive current curves, std AB is smaller, indicating that the parameter curve trends of phases A and B are more similar; similarly, std BC is smaller, indicating that the parameter curve trends of phases B and C are more similar; std AC is smaller, indicating that the parameter curve trends of phases A and C are more similar.

4. The method for warning of three-phase resistive current imbalance of a surge protector based on curve similarity according to claim 1, characterized in that, The std ABC in step 4 represents the similarity degree between the three-phase resistive current curves, and is std AB , std AC , std BC , and std ABC The smaller the maximum value among std ABC , std AC , std BC , and std ABC , the more similar the parameter curve trends of the three phases A, B, and C are.

5. The method for warning of three-phase resistive current imbalance of a surge protector based on curve similarity according to claim 1, characterized in that, The three-phase resistive current unbalanced alarm refers to that when the insulation of the lightning arrester device deteriorates, the resistive current reflecting the insulation performance will increase significantly; when the monitoring data changes sharply or the three-phase difference is large, the three-phase unbalanced alarm.

6. The method for warning of three-phase resistive current imbalance of a surge protector based on curve similarity according to claim 1, characterized in that, The three-phase resistive current unbalanced alarm refers to that when the unbalanced coefficient of the three-phase resistive current curve is greater than a certain value, the trend consistency of the three-phase resistive current is poor, and the lightning arrester alarms. The three-phase unbalanced alarm reason is basically pollution, device failure or lightning arrester deterioration, which should be alarmed to remind the operation and maintenance unit to deal with it in time.

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