On-line Monitoring Device and Method for Internal Insulation of Common-Box Bus Post Insulators

Abstract

The present invention relates to an on-line monitoring device and method for the internal insulation of a coaxial busbar support insulator, which includes a coaxial busbar. The coaxial busbar includes a housing and support insulators arranged inside the housing. It further includes a signal processing device, a current transformer arranged at the grounding end of the support insulator, and a temperature and humidity testing device arranged on the housing. The output ends of the current transformer and the temperature and humidity testing device are both connected to the input end of the signal processing device, so that the insulation of the support insulator enclosed inside the coaxial busbar and unable to be directly observed can be monitored online through current. It can provide big data support and reference for the operation, inspection and maintenance of power plants. When an unplanned outage occurs in a power generation enterprise, it can quickly and accurately judge whether the tripping is caused by the insulation of a certain support insulator, which helps the power generation enterprise quickly investigate the cause of the tripping, complete the replacement of the support insulator and the grid connection operation of the unit in the shortest time, and reduce the power quantity assessment of the grid dispatching department for the power generation enterprise.

Description

Technical Field

[0001] The present invention relates to a method for judging the internal insulation of a post insulator, in particular to an online monitoring device and method for judging the internal insulation of a common box busbar post insulator. Background Art

[0002] With the national energy sector's carbon peak and carbon neutrality goals, the installed capacity of traditional thermal power plants is declining. The average unit capacity of operating thermal power plants (including nuclear power plants) is generally above 600MW. Large hydropower stations, a traditional clean energy sector, also have a unit capacity of around 700MW. Existing power generation units should be future-proofed, enabling existing power generation methods to better adapt to the future intelligent society, energy revolution, and innovation.

[0003] The common box busbar is a busbar connecting the low-voltage side of the plant transformer to the plant distribution room in a power plant. It provides power to the distribution room and drives the various auxiliary equipment in the power plant. Located outdoors, the common box busbar is exposed to harsh conditions year-round, including wind, rain, and snow. It is an enclosed metal casing with three-phase busbar conductors enclosed. Common box busbars are typically supported by separate three-phase post insulators, with a smaller number utilizing three-phase, integrated epoxy resin panels. The insulation of the common box busbar is determined by the post insulators. Post insulators are divided into surface insulation and internal insulation. Surface insulation is significantly affected by air temperature, humidity, dust, and salt, while internal insulation is primarily affected by partial discharge, heat generation, breakdown, and insulation aging within the insulator. Under normal operation, the common box busbar is sealed with a metal cover that cannot be opened during operation. Therefore, defects in the post insulator insulation are difficult to detect immediately. If a single post insulator is defective, the cover must be opened and the problem must be checked individually, which is time-consuming and labor-intensive. Currently, the insulation quality of post insulators is only tested through preventive testing after a power outage. The insulation performance of the busbars in a running common box is not controllable. Existing infrared technology cannot perform real-time analysis due to the enclosed metal casing, and there is no intuitive and effective method to determine internal insulation problems of insulators during operation. Therefore, improvement and innovation are imperative. Summary of the Invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the purpose of the present invention is to provide an online monitoring device and method for the internal insulation of a common box busbar support insulator, which can effectively solve the problem that the insulation performance of the common box busbar support insulator cannot be monitored online during operation.

[0005] The technical solution provided by the present invention is:

[0006] An on-line insulation monitoring device for the internal insulation of a coaxial busbar support insulator, including a coaxial busbar, the coaxial busbar includes a housing and a support insulator arranged inside the housing, and further includes a signal processing device, a current transformer arranged at the grounding end of the support insulator, and a temperature and humidity testing device arranged on the housing. The output ends of the current transformer and the temperature and humidity testing device are both connected to the input end of the signal processing device, where:

[0007] The current transformer is used to measure the leakage current I of the overall support insulator 总 :

[0008] I 总 =I 内 +I 表面

[0009] I 内 =I 绝缘电阻 +I 电容

[0010] I[[ID=XX]] 总 =I 绝缘电阻 +I 电容 +I 表面

[0011] In the formula:

[0012] I 绝缘电阻 : The current flowing through the inside of the support insulator, which reflects the insulation level of the support insulator and is related to the insulation resistance of the support insulator. The calculation formula is: I 绝缘电阻 =U÷R 绝缘电阻 ;

[0013] I 电容 : The capacitive current inside the support insulator, which is related to the angular frequency ω, frequency f, system phase voltage U, and capacitance C0 of the support insulator for supporting the busbar. The calculation formula is: I 电容 =ωC0U = 2πfC0U;

[0014] I 表面 : The surface leakage current of the support insulator, which is related to the surface resistance R 表面 of the support insulator. The calculation formula is: I 表面 =U÷R 表面 ;

[0015] The temperature and humidity testing device is used to measure the temperature and humidity of the measurement environment of the coaxial busbar;

[0016] The signal processing device is used to receive the current signal measured by the current transformer and the temperature and humidity signal collected by the temperature and humidity testing device in real time, and calculate the current change Δη1 of the support insulator, the current change Δη2 of the support insulators in the same row and the same column, and the curve D-I max It should be noted that there seems to be a small error in the original text where "I 总 " is likely a mislabeled or incorrect notation. I've left it as is in the translation for the sake of following the original text exactly. If this is an important part that needs correction, please double-check the original source.The change in the tangent of the angle corresponding to the maximum current in the medium, △η3, and the change in the tangent of the angle corresponding to the total current in the D-I curve under the same temperature and humidity, △η4, are combined with the preset criteria to jointly judge the insulation condition of the coaxial busbar.

[0017] The signal processing device includes a controller, an AD converter, an alarm, a power supply, and a button. The signal output terminals of the current transformer and the temperature and humidity testing device are connected to the signal input terminal of the AD converter. The output terminal of the AD converter is connected to the input terminal of the controller. The output terminal of the controller is respectively connected to the input terminals of the display and the alarm.

[0018] An insulating spacer with a hollow middle is provided between the post insulator and the coaxial busbar housing (the housing is the grounding end). The hollow middle is for installing a wire at the bottom of the post insulator and at the same time reserving a position for installing the current transformer. At the same time, the current transformer measures the leakage current of the entire post insulator.

[0019] An on-line monitoring method for the internal insulation of a coaxial busbar post insulator includes the following steps:

[0020] Step 1: Install the on-line monitoring device

[0021] For the first installation or shutdown inspection of the coaxial busbar in the power plant, install the on-line monitoring device;

[0022] The on-line monitoring device includes a signal processing device, a current transformer arranged at the grounding end of the post insulator, and a temperature and humidity testing device arranged on the housing. The output terminals of the current transformer and the temperature and humidity testing device are both connected to the input terminal of the signal processing device;

[0023] The signal processing device is used to receive the current signal measured by the current transformer and the temperature and humidity signal collected by the temperature and humidity testing device in real time, and calculate the current change amount △η1 of the post insulator, the current change amount △η2 of the post insulators in the same row and the same column, the tangent of the angle corresponding to the maximum current in the curve D-I max The change in the tangent of the angle corresponding to the maximum current in the medium, △η3, and the change in the tangent of the angle corresponding to the total current in the D-I curve under the same temperature and humidity, △η4, are combined with the preset criteria to jointly judge the insulation condition of the coaxial busbar;

[0024] Step 2: On-line monitoring

[0025] When the coaxial busbar is operating normally, the current transformer collects the currents I1, I2,... I of each post insulator in real time n , and the temperature and humidity testing device collects the temperatures T1, T2,... T of each insulator in real time n , and the humidities S1, S2,... S n , store the data, and draw the curve D-I of the time and the maximum current of each post insulatormax ;

[0026] When the current of a certain post insulator I 内 increases, R 绝缘电阻 decreases or C0 decreases, it indicates that there may be a problem with the internal insulation, and the judgment mechanism is activated:

[0027] a. The current increases from I 内 to I 内1 , resulting in the current I 总 measured by the current transformer increasing to I 总1 . Compared with the maximum current I 总max of the post insulator one week ago using the formula △η1 = (I 总1 -I 总max )÷I 总max , when △η1 is between [100%, ∞], it indicates that the post insulator has changed significantly compared with I 总 one week ago. It can be judged that the insulator is a quasi-fault insulator, triggering a first-class pre-alarm signal and leading to the following 4 mechanisms for judgment;

[0028] b1. Call the currents I 总2 of the other two post insulators in the same row and the two adjacent post insulators in the same column of the quasi-fault insulator and compare them with the maximum currents I 总max1 of each one week ago using the formula △η2 = (I 总2 -I 总max1 )÷I 总max1 simultaneously. When △η2 are all within [0, 100%], trigger a second-class pre-alarm signal, indicating that the currents in the same row and the same column have not changed in the same way as the quasi-fault insulator, indicating that it is not the environment in the common box bus that causes the increase in I 总1 . This mechanism shows that the increase in I 总1 of the quasi-fault post insulator is caused by its own reasons and has nothing to do with the external conditions such as the temperature, humidity, and dirt of the common box bus;

[0029] b2. Call the currents I 总2 of the other two post insulators in the same row and the two adjacent post insulators in the same column of the quasi-fault insulator and compare them with the maximum currents I 总max2 of each one week ago using the formula △η2 = (I 总2 -I 总max1 )÷I 总max1 simultaneously. When △η2 is within [100%, ∞], trigger a third-class pre-alarm signal; indicating that the currents in the same row and the same column also increase, which is caused by the environment in the common box bus. This mechanism shows that the increase in I 总1 of the quasi-fault post insulator 总1The increase is caused by external conditions such as the temperature, humidity, and dirt of the common box busbar, and has nothing to do with the internal insulation of the post insulator;

[0030] c. When there is a problem inside a certain post insulator, I 内 increases, and the increase amount is I 内1 . According to the formula I 总max =I 内 +I 表面 +I 内1 causes I 总max to increase. In the curve D-I max , the angle corresponding to I 总max increases from θ1 to θ, and tanθ changes accordingly. According to the formula △η3=(tanθ - tanθ1)÷tanθ1, △η3 changes. When △η3 is between [50%, ∞], four types of pre-alarm signals are triggered;

[0031] d. When there is a problem inside a certain post insulator, I 内 increases, and the increase amount is I 内1 . Multiple groups of current data at the same temperature T and humidity S stored in the database are called, and the multiple groups of data are sorted according to time and the curve D-I of time and total current is plotted 总 . If it is affected by the temperature and humidity on the current I 总 of the post insulator, I 总 over time, at the same temperature and humidity, I 总 is affected by the surface resistance and will not cause the angle θ1 corresponding to I 总 in the D-I 总 curve to change, and tanθ1 will not change. When there is a problem inside a certain post insulator, I 内 increases, and the increase amount is I 内1 . According to the formula I 总 =I 内 +I 表面 +I 内1 causes I 总 to increase. In the D-I 总 curve, the angle corresponding to I 总 increases from θ1 to θ, and tanθ changes accordingly. According to the formula △η4=(tanθ - tanθ1)÷tanθ1, △η4 changes. When the change amount of the △η4 value is between [50%, ∞], it is determined that the post insulator is in a quasi-fault state, and five types of pre-alarm signals are triggered;

[0032] According to different combinations of alarm signals, it is finally decided whether to trigger the final alarm signal, as follows:

[0033] A. If a class I pre-alarm signal, a class II pre-alarm signal, a class IV pre-alarm signal, and a class V pre-alarm signal are triggered in sequence, and the class III pre-alarm signal is not triggered, the cause of the fault is determined as: the internal insulation of the post insulator is damaged, and the internal current increases. It is recommended to de-energize and inspect the located post insulator;

[0034] At the same time, an alarm signal for increased current is issued, and positioning is carried out;

[0035] B. If a class I pre-alarm signal and a class III pre-alarm signal are triggered in sequence, and the class II pre-alarm signal and the class IV pre-alarm signal are not triggered, the cause of the fault is determined as: the current increase is caused by dust and dirt on the surface of the post insulators in the entire common box bus. It is recommended to clean it when there is an opportunity for power outage;

[0036] At the same time, an alarm signal for increased current is issued;

[0037] C. If a class I pre-alarm signal and a class II pre-alarm signal are triggered in sequence, and the class III pre-alarm signal and the class IV pre-alarm signal are not triggered, the cause of the fault is determined as: the current increase is caused by external dirt on the located post insulator. It is recommended to check the insulator when there is an opportunity for power outage;

[0038] At the same time, an alarm signal for increased current is issued, and positioning is carried out.

[0039] Compared with the prior art, the on-line monitoring device of the present invention has a novel and unique structure, is simple and reasonable, easy to produce and operate, and can be modified on the basis of the existing common box bus. It can locate the position of the faulty insulator, provides reliable reference data for the operation of the equipment, reduces the risk of unplanned shutdown of the equipment, and can realize on-line monitoring of the insulation of the post insulator enclosed inside the common box bus through current. It can provide big data support and reference for the operation, inspection and maintenance of power plants. At the same time, when an unplanned outage occurs in a power generation enterprise, it can quickly and accurately judge whether the outage is caused by the insulation of a certain post insulator, which helps the power generation enterprise quickly investigate the cause of the outage and complete the replacement of the post insulator and the grid connection operation of the unit in the shortest time, reducing the power consumption assessment of the power generation enterprise by the power grid dispatching department. Thereby indirectly generating income for the power generation enterprise. The innovation of the present invention in on-line monitoring of the insulation state of post insulators in the common box bus fills the gap that the internal post insulators of the enclosed bus cannot be grasped during operation. It is convenient to use and has good effects. It is an innovation of the on-line monitoring device for the internal insulation of post insulators in the common box bus and has good social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the electrical schematic diagram of the present invention (all the equipment within the dashed box constitutes the common box bus).

[0041] Figure 2 It is the schematic diagram of the common box bus and the on-line detection device of the present invention.

[0042] Figure 3 This is the circuit principle block diagram of the signal processing device of the present invention.

[0043] Figure 4 This is the curve D-I of time and maximum current of the present invention max Schematic diagram.

[0044] Figure 5 This is the curve D-I of time and total current of the present invention 总 Schematic diagram.

[0045] Figure 6 This is the curve D-I of time and maximum current of the application example of the present invention max Schematic diagram.

[0046] Figure 7 This is the curve D-I of time and total current of the application example of the present invention 总 Schematic diagram.

[0047] Figure 8 This is the curve D-I of time and maximum current of the application example of the present invention max Schematic diagram. Detailed implementation manners

[0048] The following further describes in detail the detailed implementation manners of the present invention with reference to the accompanying drawings.

[0049] As Figures 1-3 shown, an on-line insulation monitoring device for a coaxial bus support insulator of the present invention includes a coaxial bus, the coaxial bus includes a housing and a support insulator disposed in the housing, and further includes a signal processing device, a current transformer disposed at the grounding end of the support insulator, and a temperature and humidity testing device disposed on the housing. The output ends of the current transformer and the temperature and humidity testing device are both connected to the input end of the signal processing device, wherein:

[0050] The current transformer is used to measure the leakage current I of the entire support insulator 总 :

[0051] I 总 = I 内 + I 表面

[0052] I 内 = I 绝缘电阻 + I 电容

[0053] I 总 = I 绝缘电阻 + I 电容 + I 表面

[0054] In the formula:

[0055] I 绝缘电阻 : The current flowing through the post insulator is an indication of the insulation level of the post insulator and is related to the insulation resistance of the post insulator. The calculation formula is: I 绝缘电阻 = U ÷ R 绝缘电阻 ;

[0056] I 电容 : The capacitive current inside the post insulator is related to the angular frequency ω, frequency f, system phase voltage U, and capacitance C0 of the post insulator supporting the busbar. The calculation formula is: I 电容 = ωC0U = 2πfC0U;

[0057] I 表面 : The surface leakage current of the post insulator is related to the surface resistance R 表面 of the post insulator. R 表面 is related to the surface dust, salt and other dirt problems of the post insulator, as well as the temperature and humidity of the environment. The calculation formula is: I 表面 = U ÷ R 表面 ;

[0058] If problems such as heating, partial discharge, breakdown, and insulation aging occur inside the insulator, resulting in an increase in I 内 The final result is obtained through the signal receiving and processing device by combining multiple criteria, and an alarm signal is sent.

[0059] The temperature and humidity test device is used to measure the environmental temperature and humidity of the common box busbar;

[0060] The signal processing device is used to receive the current signal measured by the current transformer collected in real time and the temperature and humidity signal collected by the temperature and humidity test device, and calculate the current change Δη1 of the post insulator, the current change Δη2 of the post insulators in the same row and the same column, the change Δη3 of the tangent of the angle tanθ corresponding to the maximum current in the curve D-I max The change Δη4 of the tangent of the angle tanθ corresponding to the total current in the D-I curve under the same temperature and humidity, and jointly judge the insulation condition of the common box busbar by combining the preset criteria.

[0061] To ensure the use effect, the signal processing device includes a controller, an AD converter, an alarm, a power supply and a key. The signal output ends of the current transformer and the temperature and humidity test device are connected to the signal input end of the AD converter, the output end of the AD converter is connected to the input end of the controller, and the output end of the controller is respectively connected to the input ends of the display and the alarm.

[0062] The button is connected to the controller for inputting relevant instructions, the power supply is used to supply power to each component, and the AD converter is used for signal conversion; the controller can receive the current signal measured by the current transformer collected in real time and the temperature and humidity signals collected by the temperature and humidity testing device and store them, and calculate the current change Δη1 of the post insulator, the current change Δη2 of the post insulators in the same row and the same column, and the tangent tanθ change Δη3 corresponding to the maximum current value in the curve D-I max (the curve of time and the maximum current value), and the tangent tanθ change Δη4 corresponding to the total current in the D-I curve (the curve of time and the total current) under the same temperature and humidity, jointly judge the insulation condition of the gas-insulated busbar in combination with the preset criteria, and send out corresponding warning signals, and send out alarm signals according to the combination of different warning signals, and the alarm gives an alarm. This controller is a prior art, such as a single-chip microcomputer controller of model MCS-80960, etc.

[0063] The temperature and humidity testing device is a temperature sensor (temperature probe) and a humidity sensor (humidity probe), both of which are prior arts.

[0064] An insulating spacer with a hollow middle is arranged between the post insulator and the gas-insulated busbar housing (the housing is the grounding end). The hollow middle is for installing a wire at the bottom of the post insulator and at the same time reserving a position for installing the current transformer. At the same time, the current transformer measures the entire leakage current of the post insulator.

[0065] An on-line monitoring method for the internal insulation of the post insulator of a gas-insulated busbar includes the following steps:

[0066] Step 1: Install the on-line monitoring device

[0067] For the first installation or shutdown inspection of the gas-insulated busbar in the power plant, install the on-line monitoring device;

[0068] The on-line monitoring device includes a signal processing device, a current transformer arranged at the grounding end of the post insulator, and a temperature and humidity testing device arranged on the housing. The output ends of the current transformer and the temperature and humidity testing device are both connected to the input end of the signal processing device;

[0069] The signal processing device is used to receive the current signal measured by the current transformer collected in real time and the temperature and humidity signals collected by the temperature and humidity testing device, and calculate the current change Δη1 of the post insulator, the current change Δη2 of the post insulators in the same row and the same column, and the curve D-I 总max the tangent tanθ change Δη3 corresponding to the maximum current value in it, and the tangent tanθ change Δη4 corresponding to the total current in the D-I curve under the same temperature and humidity, jointly judge the insulation condition of the gas-insulated busbar in combination with the preset criteria;

[0070] Step 2: On-line monitoring

[0071] The enclosed bus operates normally, and the current transformers collect the currents I1, I2, … I of each post insulator in real time. n , and the temperature and humidity testing device collects the temperatures T1, T2, … T of each insulator in real time. n , and the humidities S1, S2, … S n , stores the data, and plots the curve D-I of the time and the maximum current of each post insulator. max (Taking equal-length time as the abscissa, taking the maximum current value within the equal-length time as the ordinate, the time interval is taken as weekly or daily, and can also be set by the user according to needs); taking the change rate of the slope of the time D and the maximum current I max as the judgment criterion;

[0072] When the current of a certain post insulator I 内 increases, indicating that R 绝缘电阻 decreases or C0 decreases, it indicates that there may be a problem with the internal insulation, and the judgment mechanism is started:

[0073] a. The current increases from I 内 to I 内1 , resulting in the current I 总 measured by the current transformer increasing to I 总1 , and comparing it with the maximum current I 总max of the post insulator one week ago using the formula △η1 = (I 总1 - I 总max ) ÷ I 总max . When △η1 is between [100%, ∞], it indicates that the post insulator has changed significantly compared to I 总 one week ago, and it can be judged that the insulator is a quasi-fault insulator. According to I 总 = I 内 + I 表面 + I 内1 , it is necessary to rule out whether it is the influence of I 表面 current. If it is not the influence of I 表面 current, then it is the influence of I 内 and I 内1 . To rule out the influence of I 表面 , a class of pre-alarm signals is triggered, and the following 4 mechanisms are introduced to judge it;

[0074] b1. Call the currents I 总2 of the other two post insulators in the same row and the two adjacent post insulators in the same column of the quasi-fault insulator and compare them with the maximum currents I 总max1 of each of them one week ago using the formula △η2 = (I 总2 - I 总max1 ) ÷ I 总max1At the same time, a comparison is made. Since there are 4 post insulators in the same row and the same column, and they are located in the same enclosed busbar, the external environment they are subjected to is the same, such as the same temperature, humidity, dirt, etc. When △η2 is within the range of [0, 100%], a second-class pre-alarm signal is triggered, indicating that the current in the same row and the same column does not change in the same way as that of the quasi-fault insulator, indicating that it is not caused by the environment in the coaxial busbar I 总1 increases, and this mechanism indicates that it is caused by the quasi-fault post insulator itself I 总1 increases and has nothing to do with the external conditions such as the temperature, humidity, and dirt of the coaxial busbar;

[0075] b2. Call the currents I of the other two post insulators in the same row as the quasi-fault insulator and the two adjacent post insulators in the same column 总2 and the maximum current I one week ago for each of them 总max1 Use the formula △η2 = (I 总2 -I 总max1 )÷I 总max1 At the same time, a comparison is made. Since the 4 post insulators in the same row and the same column are located in the same enclosed busbar, the external environment they are subjected to is the same, such as the same temperature, humidity, dirt, etc. When △η2 is within the range of [100%, ∞], a third-class pre-alarm signal is triggered; indicating that the current in the same row and the same column also increases, which is caused by the environment in the coaxial busbar I 总1 increases, and this mechanism indicates that it is the quasi-fault post insulator I 总1 The increase is caused by the external conditions such as the temperature, humidity, and dirt of the coaxial busbar and has nothing to do with the internal insulation of the post insulator;

[0076] c. The third type of judgment mechanism is based on the change amount △η3 of tanθ in the curve D-I max to judge. As Figure 4 shown, as time goes by, the surface of the post insulator is affected by external factors such as dust and salt dirt, and I 表面 the current increases slowly with time. According to I 总 =I 内 +I 表面 , I 内 =I 绝缘电阻 +I 电容 , where I 电容 remains unchanged, the capacitance C0 of the post insulator does not change. According to the formula: I 电容 =ωC0U = 2πfC0U, I 绝缘电阻 does not change, the insulation resistance of the post insulator remains unchanged. According to the formula: I 内 =U÷R 绝缘电阻 , so I 总 will increase similarly as I 表面 increases, I总 The increased rate is consistent with I 表面 The rate remains consistent. Similarly, I 总max The increased rate is consistent with I 表面 The rate remains consistent. When the internal insulation does not change, θ1 remains unchanged.

[0077] According to the formula:

[0078] tanθ = I 总max ÷D

[0079] △η3 = (tanθ - tanθ1) ÷ tanθ1

[0080] tanθ is a fixed value and will not cause △η3 to change.

[0081] When there is a problem inside a certain post insulator, I 内 increases, and the increase amount is I 内1 , according to the formula I 总max = I 内 + I 表面 + I 内1 causes I 总max to increase, and in the curve D - I max the I 总max corresponding angle increases from θ1 to θ, and tanθ changes accordingly. According to the formula △η3 = (tanθ - tanθ1) ÷ tanθ1, △η3 changes. When △η3 is between [50%, ∞], four types of pre-alarm signals are triggered; based on the change of △η3, the influence of problems such as dust and salt contamination of the post insulator due to external reasons can be excluded, and it can be determined that there is a problem inside the post insulator.

[0082] d. This criterion is used as a supplement to the c-class criterion, and a d-class criterion is introduced to judge the supplement of the criterion for the increase in I caused by internal insulation damage 总 for the increase criterion.

[0083] Based on the daily temperature T and humidity S collected by the signal processing device, a curve D - I of time and current is plotted 总 curve and stored in the database of temperature, humidity and current. When there is a problem inside a certain post insulator, I 内 increases, and the increase amount is I 内1 , multiple groups of current data at the same temperature T and humidity S stored in the database are called, and the multiple groups of data are sorted according to time and a curve D - I of time and total current is plotted 总 , as Figure 5 shown, according to the set reference time point, an equal length of time is taken as the abscissa, and the current corresponding to the equal length time point is taken as the ordinate;

[0084] If it is affected by temperature and humidity on the current I of the post insulator 总Influence, I 总 Over time, at the same temperature and humidity, I 总 Affected by the surface resistance, it will not cause D-I 总 In the curve of I 总 The corresponding angle θ1 changes, tanθ1 does not change. When there is a problem inside a certain post insulator, I 内 Increases, and the increase amount is I 内1 , according to the formula I 总 =I 内 +I 表面 +I 内1 Causes I 总 To increase, D-I 总 In the curve of I 总 The corresponding angle increases from θ1 to θ, and tanθ changes accordingly. According to the formula △η4=(tanθ - tanθ1)÷tanθ1, △η4 changes. Based on the change of △η4, the influence of temperature and humidity can be excluded, and it is determined that there is a problem inside the post insulator;

[0085] tanθ = I 总 ÷D

[0086] △η4=(tanθ - tanθ1)÷tanθ1

[0087] When the change amount of the △η4 value is within the range of [50%, ∞], it is determined that the post insulator is in a quasi-fault state, and five types of pre-alarm signals are triggered; according to the change of △η4, it can be judged that the post insulator is not affected by temperature and humidity, and it is a supplementary criterion for determining that there is a problem inside the post insulator;

[0088] According to different combinations of alarm signals, it is finally decided whether to trigger the final alarm signal, as follows:

[0089] A. Trigger the first-class pre-alarm signal, the second-class pre-alarm signal, the fourth-class pre-alarm signal, and the fifth-class pre-alarm signal in sequence, and the third-class pre-alarm signal is not triggered. Then the cause of the fault is determined as: the internal insulation of the post insulator is damaged, the internal current increases, and it is recommended to power off and detect the located post insulator;

[0090] At the same time, an alarm signal of increased current is sent out, and the location is sent out;

[0091] [

[0091] B. Trigger the first-class pre-alarm signal and the third-class pre-alarm signal in sequence, and the second-class pre-alarm signal and the fourth-class pre-alarm signal are not triggered. Then the cause of the fault is determined as: the current increases due to dust and dirt on the surface of the post insulator in the entire coaxial busbar, and it is recommended to clean it when there is a power-off opportunity;

[0092] At the same time, an alarm signal of increased current is sent out;

[0093] C. If a class I pre-alarm signal and a class II pre-alarm signal are triggered in sequence, and a class III pre-alarm signal and a class IV pre-alarm signal are not triggered, the cause of the fault is determined as follows: the external dirt of the located post insulator causes an increase in current. It is recommended to check the insulator when there is a power outage opportunity.

[0094] At the same time, an alarm signal for increased current is issued, and positioning is also issued.

[0095] Specifically, it is shown in the following table:

[0096]

[0097] Through actual application, the present invention has achieved good technical effects. The application examples are as follows:

[0098] In the laboratory, an external excitation transformer is used to generate a high voltage of 30 kV, which is applied to the busbar of the post insulator to simulate the operating state; the signal acquisition device for measuring the current signal is clamped to the grounding end of the post insulator; the voltage signal is taken from the high-voltage winding of the excitation transformer, and a voltage divider is used to measure the voltage of the high-voltage winding. Using several existing post insulators in the laboratory in different states for simulation, the equipment is connected according to the device of the present invention, and numerical acquisition and on-line monitoring are carried out by the method of the present invention. The on-line test data in the laboratory are shown in Table 1:

[0099] Table 1 On-line test data of post insulator simulation

[0100]

[0101]

[0102] In the table, working condition 1 corresponds to the data measured after the first installation or shutdown inspection of the common box busbar in the power plant and the installation of the on-line monitoring device. Working condition 2 corresponds to the increase in surface pollution degree simulated with the passage of time, and the surface pollution degree is changed, and the current value is measured with the passage of time, and the current value increases accordingly.

[0103] The first type of alarm signal

[0104] I. For working condition 3, the internal insulation of post insulator A is reduced from R to 3 / 4R, and the measured current of A increases from I 总max = 0.017 to I 总1 = 0.041. According to the formula △η1 = (I 总1 - I 总max ) ÷ I 总max calculate △η1 = (0.041 - 0.017) ÷ 0.017 * 100% = 141%,

[0105] When △η1 is between [100%, ∞], it indicates that the post insulator has a current increase compared to I one week ago 总Great changes have occurred, and it can be judged that the insulator is a quasi-fault insulator. Trigger a class I pre-alarm signal, and the following 4 mechanisms are introduced to judge it.

[0106] Second, call the currents I of the other two post insulators in the same row and the two adjacent post insulators in the same column of the quasi-fault insulator 总2 and the maximum current value I one week ago for each of them 总max1 Use the formula △η2 = (I 总2 - I 总max1 ) ÷ I 总max1 to make a comparison at the same time. The data is as follows:

[0107] Two: △η2 = (0.016 - 0.011) ÷ 0.011 * 100% = 45%

[0108] Three: △η2 = (0.016 - 0.010) ÷ 0.010 * 100% = 60%

[0109] Four: △η2 = (0.017 - 0.011) ÷ 0.011 * 100% = 55%

[0110] Five: △η2 = (0.016 - 0.011) ÷ 0.011 * 100% = 45%

[0111] When △η2 is within the range of [0, 100%], trigger a class II pre-alarm signal.

[0112] Third, according to the formula △η3 = (tanθ - tanθ1) ÷ tanθ1, combined with Figure 6 ;

[0113] Calculated according to working condition 2: tanθ = 0.041 ÷ 4 = 0.01025

[0114] tanθ1 = 0.017 ÷ 3 = 0.0057

[0115] △η3 = (tanθ - tanθ1) ÷ tanθ1

[0116] △η3 = (0.01025 - 0.0057) ÷ 0.057 * 100% = 79.8%

[0117] △η3 has changed. When △η3 is within the range of [50%, ∞], trigger a class IV pre-alarm signal;

[0118] Fourth, call multiple groups of current data at the same temperature T and humidity S stored in the database, sort the multiple groups of data according to time, and draw the curve D-I of time and total current 总 Combined with Figure 7 ;

[0119] Combined with operating conditions 3 and 4 and the formula:

[0120] tanθ = I 总 ÷D

[0121] △η4 = (tanθ - tanθ1)÷tanθ1

[0122] tanθ = 0.041÷4 = 0.01025

[0123] tanθ1 = 0.017÷3 = 0.0057

[0124] △η4 = (0.01025 - 0.0057)÷0.057*100% = 79.8%

[0125] When the change amount of the △η4 value is between [50%, ∞], it is determined that the post insulator is in a quasi-fault state, and a type-five pre-alarm signal is triggered;

[0126] Combined with the type-one pre-alarm signal, type-two pre-alarm signal, type-four pre-alarm signal, and type-five pre-alarm signal issued by the equipment, a type-one alarm signal is issued.

[0127] Type-two alarm signal

[0128] Combined with operating conditions 1 and 5

[0129] 1. The test current of post insulator A increases from I 总max = 0.017 to I 总1 = 0.036. According to the formula △η1 = (I 总1 -I 总max )÷I 总max Calculate △η1 = (0.036 - 0.017)÷0.017*100% = 111.7%. When △η1 is between [100%, ∞], it indicates that the post insulator has changed significantly compared with I 总 one week ago. It can be judged that the insulator is a quasi-fault insulator, and a type-one pre-alarm signal is triggered;

[0130] 2. Call the currents I 总2 of the other two post insulators in the same row and the two adjacent post insulators in the same column of the quasi-fault insulator 总max1 and compare them with the maximum current I 总2 -I 总max1 )÷I 总max1 of each of them one week ago at the same time. The △η2 of the other four post insulators:

[0131] Two: △η2 = (0.037 - 0.016)÷0.011*100% = 131%

[0132] Three: Δη2 = (0.038 - 0.016) ÷ 0.010 * 100% = 138%

[0133] Four: Δη2 = (0.036 - 0.017) ÷ 0.011 * 100% = 112%

[0134] Five: Δη2 = (0.038 - 0.016) ÷ 0.011 * 100% = 138%

[0135] When Δη2 is within [100%, ∞], three types of pre - alarm signals are triggered; it indicates that the current in the same row and the same column also increases, which is caused by the environment in the common - box busbar I 总1 Increased, this mechanism indicates a quasi - fault post insulator I 总1 The increase is caused by external conditions such as the temperature, humidity, and dirt of the common - box busbar, which has nothing to do with the internal insulation of the post insulator, and the second - type alarm signal is issued.

[0136] The third - type alarm signal

[0137] Combining working condition 1 and working condition 6

[0138] 1. The test current of post insulator A increases from I 总max = 0.010 to I 总1 = 0.022. According to the formula Δη1 = (I 总1 - I 总max ) ÷ I 总max Calculate Δη1 = (0.022 - 0.010) ÷ 0.010 * 100% = 120%. When Δη1 is within [100%, ∞], it indicates that this post insulator has changed significantly compared with a week ago I 总 A large change has occurred, and it can be judged that this insulator is a quasi - fault insulator, triggering a first - type pre - alarm signal;

[0139] 2. Call the currents I 总2 of the other two post insulators in the same row as the quasi - fault insulator and the two adjacent post insulators in the same column 总max1 Compare them with the maximum current I 总2 of each of them a week ago using the formula Δη2 = (I 总max1 ) ÷ I 总max1 at the same time. The data is as follows:

[0140] Two: Δη2 = (0.016 - 0.011) ÷ 0.011 * 100% = 45%

[0141] Three: Δη2 = (0.016 - 0.010) ÷ 0.010 * 100% = 60%

[0142] Four: Δη2 = (0.017 - 0.011) ÷ 0.011 * 100% = 55%

[0143] Five: Δη2 = (0.016 - 0.011) ÷ 0.011 * 100% = 45%

[0144] When Δη2 is all within [0, 100%], a secondary pre-alarm signal is triggered;

[0145] III. According to the formula Δη3 = (tanθ - tanθ1) ÷ tanθ1, combined with Figure 8 ;

[0146] Calculated according to working condition 2: tanθ = 0.022 ÷ 3 = 0.0073

[0147] tanθ1 = 0.011 ÷ 2 = 0.0055

[0148] Δη3 = (tanθ - tanθ1) ÷ tanθ1

[0149] Δη3 = (0.0073 - 0.0055) ÷ 0.0055 * 100% = 32.7%

[0150] When Δη3 is within [0, 50%], a four - category pre - alarm signal is not triggered, indicating that the increase in current is caused by external dirt on the located post insulator. It is recommended to check the insulator when there is a power outage opportunity. The details are shown in the following table:

[0151]

Claims

1. An on-line monitoring device for the internal insulation of a coaxial bus support insulator, comprising a coaxial bus, the coaxial bus including a housing and a support insulator disposed within the housing, characterized in that, It also includes a signal processing device, a current transformer arranged at the grounding end of the post insulator, and a temperature and humidity testing device arranged on the housing. The output ends of the current transformer and the temperature and humidity testing device are both connected to the input end of the signal processing device, where: The current transformer is used to measure the leakage current I of the entire post insulator 总 : I 总 = I 内 + I 表面 I 内 = I 绝缘电阻 + I 电容 I 总 = I 绝缘电阻 + I 电容 + I 表面 Where: I 绝缘电阻 : The current flowing through the post insulator is an indication of the insulation level of the post insulator and is related to the insulation resistance of the post insulator. The calculation formula is: I 绝缘电阻 = U÷R 绝缘电阻 ; I 电容 : The capacitive current inside the post insulator is related to the angular frequency ω, frequency f, system phase voltage U of the post insulator supporting the busbar, and the capacitance C0 of the post insulator. The calculation formula is: I 电容 = ωC0U = 2πfC0U; I 表面 : The surface leakage current of the post insulator and the surface resistance R of the post insulator 表面 are related. The calculation formula is: I 表面 = U ÷ R 表面 ; The temperature and humidity testing device is used to measure the ambient temperature and humidity of the gas-insulated busbar; The signal processing device is used to receive the leakage current I measured by the current transformer during real-time acquisition 总 of the current signal and the temperature and humidity signals collected by the temperature and humidity test device, and calculate the current change Δη1 of the post insulator, the current change Δη2 of the post insulators in the same row and column, and the curve D-I max of the leakage current I 总 in the maximum current value corresponding to the change in the tangent of the included angle tanθ Δη3, and the change in the tangent of the included angle tanθ Δη4 corresponding to the leakage current I in the D-I curve under the same temperature and humidity, and jointly judge the insulation condition of the common box bus according to the preset criteria. 总 ​ 2. The on-line insulation monitoring device for the internal insulation of the coaxial bus support insulator according to claim 1, characterized in that, The signal processing device includes a controller, an AD converter, an alarm, a power supply, and a key. The signal output ends of the current transformer and the temperature and humidity testing device are connected to the signal input end of the AD converter. The output end of the AD converter is connected to the input end of the controller. The output end of the controller is respectively connected to the input ends of a display and an alarm.

3. The on-line insulation monitoring device for the internal insulation of the coaxial bus support insulator according to claim 1, characterized in that, An insulating spacer with a hollow middle is arranged between the post insulator and the housing of the gas-insulated busbar. The hollow middle is for installing a wire at the bottom of the post insulator and at the same time reserving a position for installing the current transformer; meanwhile, the current transformer can measure the entire leakage current of the post insulator.

4. An on-line monitoring method for the internal insulation of a coaxial bus support insulator, characterized in that, It includes the following steps: Step 1: Install the on-line monitoring device For the first installation or shutdown inspection of the power plant gas-insulated busbar, install the on-line monitoring device; The on-line monitoring device includes a signal processing device, a current transformer arranged at the grounding end of the post insulator, and a temperature and humidity testing device arranged on the housing. The output ends of the current transformer and the temperature and humidity testing device are both connected to the input end of the signal processing device; The signal processing device is used to receive the leakage current I measured by the current transformer during real-time acquisition 总 of the current signal and the temperature and humidity signals collected by the temperature and humidity test device, and calculate the current change amount Δη1 of the post insulator, the current change amount Δη2 of the post insulators in the same row and column, and the curve D-I max of the leakage current I 总 in the maximum current value corresponding to the change amount Δη3 of the tangent of the included angle tanθ, and the change amount Δη4 of the tangent of the included angle tanθ corresponding to the leakage current I in the D-I curve under the same temperature and humidity, and jointly judge the insulation condition of the common box bus according to the preset criteria; 总 ​ Step 2: On-line monitoring The common-box busbar operates normally, and the current transformers collect the currents I1, I2, … I of each post insulator in real time n , and the temperature and humidity testing device collects the temperatures T1, T2, … T of each insulator in real time n , and the humidities S1, S2, … S n , stores the data, and plots the curve D-I of the time and the maximum leakage current I 总 of each post insulator max ; When a certain post insulator I 内 increases, indicating that R 绝缘电阻 decreases or the capacitance C0 of the post insulator decreases, indicating that there may be a problem with the internal insulation, and the judgment mechanism is started: a. The current increases from I 内 to I 内1 , resulting in the current I measured by the current transformer 总 increasing to I 总1 , which is compared with the maximum current value I of the post insulator a week ago 总max Using the formula △η1 = (I 总1 - I 总max ) ÷ I 总max for comparison. When △η1 is between [100%, ∞], it indicates that the post insulator has changed significantly compared with I a week ago 总 . It can be judged that the insulator is a quasi-fault insulator, triggering a type-I pre-alarm signal, and the following 4 mechanisms are introduced to judge it; b1. Call the currents I of the other two post insulators in the same row and the two adjacent post insulators in the same column of the quasi-fault insulator 总2 and the maximum current I one week ago for each of them 总max1 Apply the formula △η2 = (I 总2 - I 总max1 ) ÷ I 总max1 At the same time, make a comparison. When △η2 is all within [0, 100%], trigger a type-II pre-alarm signal, indicating that the currents in the same row and the same column do not change in the same way as the quasi-fault insulator, indicating that it is not caused by the environment in the common box bus 总1 increase. This mechanism indicates that the quasi-fault post insulator is caused by its own reasons 总1 increase, and has nothing to do with external conditions such as the temperature, humidity, and dirt of the common box bus; b2. Call the currents I of the other two post insulators in the same row and the two adjacent post insulators in the same column of the quasi-fault insulator 总2 and their maximum current values I one week ago respectively 总max1 Apply the formula △η2 = (I 总2 - I 总max1 ) ÷ I 总max1 for comparison at the same time. When △η2 is within [100%, ∞], trigger three types of pre-alarm signals; it indicates that the currents in the same row and the same column also increase, which is caused by the environment in the coaxial busbar 总1 The increase is due to the quasi-fault post insulator 总1 The increase is caused by external conditions such as the temperature, humidity, and dirt of the coaxial busbar, and has nothing to do with the internal insulation of the post insulator; c. When there is a problem inside a certain post insulator, I 内 increases, and the increase amount is I 内1 . According to the formula I 总max = I 内 + I 表面 + I 内1 causes I 总max to increase. In the curve D-I max , the angle corresponding to I 总max increases from θ1 to θ, and tanθ changes accordingly. According to the formula △η3 = (tanθ - tanθ1) ÷ tanθ1, △η3 changes. When △η3 is between [50%, ∞], four types of pre-alarm signals are triggered; d. When a problem occurs inside a certain post insulator, I 内 increases, and the increase amount is I 内1 , call multiple groups of current data stored in the database at the same temperature T and humidity S, sort the multiple groups of data according to time, and draw the curve D-I total of time and total current If the current I of the post insulator is affected by temperature and humidity 总 affected, I 总 over time, at the same temperature and humidity, I 总 affected by the surface resistance, will not cause the angle θ1 corresponding to I in the D-I 总 curve to change, tanθ1 will not change. When there is a problem inside a certain post insulator, I 总 increases, and the increase amount is I 内 , according to the formula I 内1 =I 总 +I 内 +I 表面 +I 内1 causes the total I to increase. The angle corresponding to the total I in the D-I total curve increases from θ1 to θ, and tanθ changes accordingly. According to the formula △η4=(tanθ - tanθ1)÷tanθ1, △η4 changes. When the change amount of the △η4 value is within the range of [50%, ∞], it is determined that the post insulator is in a quasi-fault state, and five types of pre-alarm signals are triggered; According to different combinations of alarm signals, it is finally decided whether to trigger the final alarm signal, specifically as follows: A. Trigger the first type of pre-alarm signal, the second type of pre-alarm signal, the fourth type of pre-alarm signal, and the fifth type of pre-alarm signal in sequence, and the third type of pre-alarm signal is not triggered. Then the fault cause is determined as: the internal insulation of the post insulator is damaged, the internal current increases, and it is recommended to power off and inspect the located post insulator; At the same time, an alarm signal of increased current is issued, and the location is issued; B. Trigger the first type of pre-alarm signal and the third type of pre-alarm signal in sequence, and the second type of pre-alarm signal and the fourth type of pre-alarm signal are not triggered. Then the fault cause is determined as: the current increases due to dust and dirt on the surface of the post insulator in the entire gas-insulated busbar, and it is recommended to clean it when there is a power-off opportunity; At the same time, an alarm signal of increased current is issued; C. Trigger the first type of pre-alarm signal and the second type of pre-alarm signal in sequence, and the third type of pre-alarm signal and the fourth type of pre-alarm signal are not triggered. Then the fault cause is determined as: the current increases due to dirt outside the located post insulator, and it is recommended to check the insulator when there is a power-off opportunity; At the same time, an alarm signal of increased current is issued, and the location is issued.

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