A distribution network cable early fault location system based on transient disturbance and its control method

Abstract

The present invention discloses a distribution network cable early fault location system based on transient disturbance and a control method thereof, wherein the system comprises an information transmission module, a transient disturbance signal detection module, a transient disturbance signal identification module, a fault warning module, a fault data processing module and a cable fault location module. The system is an efficient, low-cost, high-reliability cable early fault warning and location method, which can simplify and improve the efficiency of operation and maintenance work, effectively prevent cable faults, timely discover early cable faults, and avoid power outage losses caused by cable faults.

Description

Technical Field

[0001] The invention belongs to the technical field of electric power, and relates to a distribution network cable early fault location system based on transient disturbance and a control method thereof. Background Art

[0002] The distribution network is located at the end of the power system and is directly connected to the users. The power supply capacity and quality of the entire power system to users are realized and guaranteed by it. Therefore, the distribution network is not only the development foundation of the entire power system, but also its final destination, and is an important link in realizing the smart grid. At the same time, with the gradual expansion of urban scale, the load density of the distribution network continues to increase, and the requirements for its power supply reliability and power supply quality are getting higher and higher. However, at present, the mutual supply capacity of the power grid during high load periods is insufficient, and large-scale power outages are very likely to occur. Its power supply reliability and ability to resist natural disasters need to be improved urgently.

[0003] With the acceleration of urbanization, the proportion of cables in urban power supply has become increasingly important. They have gradually replaced overhead power supply lines and are widely used in distribution networks. Underground cables are safer than overhead lines in bad weather, more economical for short-distance transmission, and are not easily affected by the environment and easy to maintain, so they have been widely used. Power cables are mainly used for power lead-in lines of substations, power plants and industrial and mining enterprises. Their scope of use has gradually become wider and they have received attention. With the development of urban construction, overhead transmission lines have been gradually replaced by power cables, and their proportion in urban power supply has become larger and larger. With the widespread use of power cables, there will inevitably be an increase in cable faults. Underground cables are more likely to cause permanent faults due to partial discharge, flashover, etc., and fault finding is more difficult. They are the equipment with the highest failure rate in distribution network equipment. In order to ensure the safe and stable operation of power cables, early cable faults should be discovered and dealt with in a timely manner. Summary of the invention

[0004] To solve the above problems, the present invention provides a distribution network cable early fault location system based on transient disturbance and its control method. The system is an efficient, low-cost, and highly reliable cable early fault warning and location method, which can simplify and improve the efficiency of operation and maintenance work and effectively prevent cable failures. Therefore, it is necessary to study the degradation process of medium-voltage cables, establish standard parameters for the degree of degradation of medium-voltage distribution network cables, propose monitoring means and identification methods for early cable failures, realize fault type identification and severity assessment, timely discover early cable failures, and avoid power outage losses caused by cable failures.

[0005] The present invention is specifically a distribution network cable early fault location system based on transient disturbance, the system comprises an information transmission module, a transient disturbance signal detection module, a transient disturbance signal identification module, a fault warning module, a fault data processing module and a cable fault location module; the information transmission module transmits the information of the measurement point to the transient disturbance signal detection module and the fault data processing module; the transient disturbance signal detection module is connected to the transient disturbance signal identification module, the transient disturbance signal identification module identifies the detected transient disturbance signal and preliminarily determines the possibility of a fault; the transient disturbance signal identification module is connected to the fault warning module, the fault warning module sends a warning signal when the transient disturbance signal identification module identifies that the possibility of a fault is too high; the transient disturbance signal identification module is also connected to the fault data processing module, the fault data processing module further determines and processes the identified suspected fault information; the fault data processing module is connected to the cable fault location module, the cable fault location module locates the cable fault determined by the fault data processing module to quickly obtain the specific location of the cable fault point.

[0006] Furthermore, the transient disturbance signal detection module and the transient disturbance signal identification module are based on the operation of statistical pattern recognition of interference signals of the expert system to collect effective fault signals.

[0007] Furthermore, the information transmission module can perform signal conversion and data transmission on the fault signal collected by the measuring point between the modules.

[0008] Furthermore, the transient disturbance signal detection module can detect electrical characteristic quantities such as the grounding line current, zero-sequence voltage, and zero-sequence current of the cable that reflect the electrical characteristics of the cable.

[0009] Furthermore, the transient disturbance signal recognition module can use neural networks, support vector machines, etc. to recognize multiple types of disturbances on the signal.

[0010] Furthermore, the fault data processing module and the cable fault locating module judge and locate early-stage cable faults based on transient disturbance signals.

[0011] The present invention also includes a control method for a distribution network cable early fault location system based on transient disturbance, characterized in that the control method comprises the following steps:

[0012] Step 1: For the installed transient voltage and current signal transformers, a combination of modeling analysis and experimental testing is used to conduct a systematic theoretical analysis of the transient traveling wave signal transmission characteristics generated by early faults;

[0013] Step 2: According to the basic principle of transient voltage and current signal transformer, establish its equivalent circuit model, conduct transmission test on fault transient traveling wave, and obtain the parameters such as transmission gain, response delay, waveform distortion, etc. of the transformer to the signal according to the test;

[0014] Step 3: Process the transient traveling wave signals on the primary and secondary sides, and conduct comparative analysis to reveal the nature of the changes in the secondary side signals when the transient traveling wave passes through the transformer. Process the secondary side fault signal to identify the information contained in the transient traveling wave head signal generated by the early fault.

[0015] Step 4: Determine the high-frequency component ω of the first wave head of the current traveling wave at each measuring point after the distribution network fails i The difference in the distribution of polarity η and energy E between the fault line section and the non-fault line section is used to construct the fault line section identification indicator factor ξ f As shown below:

[0016]

[0017] Among them, ξ f is the fault section identification indicator factor detected at each current traveling wave measurement point, η i and γ i is the corresponding weight, which is predetermined according to the actual fault situation and the influence of the mutual inductor on the traveling wave propagation characteristics; the measurement points corresponding to the first three largest fault section identification factor values ​​are selected as the section where the fault line is located;

[0018] Step 5: Using the early fault transient signals measured at all measuring points on the fault section line, considering the shortest propagation path and the corresponding time of the signal mutation point, reasonably determine the signal calculation data window length and the spectrum range of the high-frequency component to be extracted, and use S transform to extract the amplitude and phase information of the high-frequency component of the first wave head of the transient traveling wave signal at each measuring point; the frequency of the first wave head of the traveling wave detected at any measuring point A is ω i The high frequency signal is expressed by the following formula:

[0019]

[0020] in, and θ Ai =-β i x is the frequency of the traveling wave head signal obtained at the measuring point A, and ω i The amplitude and phase of the high-frequency signal;

[0021] Step 6: Using the virtual bus method, when a fault occurs at a certain position of the line between different measurement points, the difference between the theoretical high-frequency component amplitude ratio calculated according to the above formula and the actual amplitude ratio of the same high-frequency component calculated by S transform is considered. The idea of ​​iterative search is used to solve the hypothetical position corresponding to the minimum difference, and this position corresponds to the actual precise position of the fault;

[0022] Step 7: Considering that the results obtained by using a single amplitude information may contain pseudo roots, the theoretical phase difference and actual phase difference of the same high-frequency component of the corresponding measuring point are calculated while calculating the amplitude ratio of the corresponding measuring point. The precise fault location is solved in the same way, and then the intersection of the results calculated by the two methods is taken. This is sufficient to ensure that the precise fault location results do not contain pseudo roots in various situations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 To invent a structural schematic diagram of a distribution network cable early fault location system based on transient disturbance;

[0024] Figure 2 This is a schematic diagram of a typical topological structure of a distribution network. DETAILED DESCRIPTION

[0025] The following is a detailed description of a specific example of a distribution network cable early fault location system based on transient disturbance and a control method thereof in conjunction with the accompanying drawings.

[0026] like Figure 1 As shown, the distribution network cable early fault location system based on transient disturbance of the present invention includes an information transmission module, a transient disturbance signal detection module, a transient disturbance signal identification module, a fault warning module, a fault data processing module and a cable fault location module; the information transmission module transmits the information of the measurement point to the transient disturbance signal detection module and the fault data processing module; the transient disturbance signal detection module is connected to the transient disturbance signal identification module, and the transient disturbance signal identification module identifies the detected transient disturbance signal and preliminarily determines the possibility of a fault; the transient disturbance signal identification module is connected to the fault warning module, and the fault warning module sends a warning signal when the transient disturbance signal identification module identifies that the possibility of a fault is too high; the transient disturbance signal identification module is also connected to the fault data processing module, and the fault data processing module further determines and processes the identified suspected fault information; the fault data processing module is connected to the cable fault location module, and the cable fault location module locates the cable fault determined by the fault data processing module to quickly obtain the specific location of the cable fault point.

[0027] The transient disturbance signal detection module and the transient disturbance signal identification module are based on the operation of statistical pattern recognition of the interference signal of the expert system to collect effective fault signals.

[0028] The information transmission module can perform signal conversion and data transmission on the fault signals collected by the measuring points between the modules.

[0029] The transient disturbance signal detection module can detect electrical characteristic quantities such as the grounding line current, zero-sequence voltage, and zero-sequence current of the cable that reflect the electrical characteristics of the cable.

[0030] The transient disturbance signal recognition module can use neural networks, support vector machines, etc. to identify multiple types of disturbances in signals.

[0031] The fault data processing module and the cable fault locating module judge and locate the early-stage cable fault based on the transient disturbance signal.

[0032] like Figure 2 As shown, a distribution network cable early fault location system based on transient disturbance and its control method are further explained through a typical distribution network topology structure. The distribution network topology structure in the figure is equipped with a fault transient signal measurement unit (transformer) and a cable early fault occurrence point.

[0033] Step 1: For the installed transient voltage and current signal transformers, a combination of modeling analysis and experimental testing is used to conduct a systematic theoretical analysis of the transient traveling wave signal transmission characteristics generated by early faults;

[0034] Step 2: According to the basic principle of transient voltage and current signal transformer, establish its equivalent circuit model, conduct transmission test on fault transient traveling wave, and obtain the parameters such as transmission gain, response delay, waveform distortion, etc. of the transformer to the signal according to the test;

[0035] Step 3: Process the transient traveling wave signals on the primary and secondary sides, and conduct comparative analysis to reveal the nature of the changes in the secondary side signals when the transient traveling wave passes through the transformer. Process the secondary side fault signal to identify the information contained in the transient traveling wave head signal generated by the early fault.

[0036] Step 4: Determine the high-frequency component ω of the first wave head of the current traveling wave at each measuring point after the distribution network fails i The difference in the distribution of polarity η and energy E between the fault line section and the non-fault line section is used to construct the fault line section identification indicator factor ξ f As shown below:

[0037]

[0038] Among them, ξ fis the fault section identification indicator factor detected at each current traveling wave measurement point, η i and γ i is the corresponding weight, which is predetermined according to the actual fault situation and the influence of the mutual inductor on the traveling wave propagation characteristics; the measurement points corresponding to the first three largest fault section identification factor values ​​are selected as the section where the fault line is located;

[0039] Step 5: Using the early fault transient signals measured at all measuring points on the fault section line, considering the shortest propagation path and the corresponding time of the signal mutation point, reasonably determine the signal calculation data window length and the spectrum range of the high-frequency component to be extracted, and use S transform to extract the amplitude and phase information of the high-frequency component of the first wave head of the transient traveling wave signal at each measuring point; the frequency of the first wave head of the traveling wave detected at any measuring point A is ω i The high frequency signal is expressed by the following formula:

[0040]

[0041] in, and θ Ai =-β i x is the frequency of the traveling wave head signal obtained at the measuring point A, and ω i The amplitude and phase of the high-frequency signal;

[0042] Step 6: Using the virtual bus method, when a fault occurs at a certain position of the line between different measurement points, the difference between the theoretical high-frequency component amplitude ratio calculated according to the above formula and the actual amplitude ratio of the same high-frequency component calculated by S transform is considered. The idea of ​​iterative search is used to solve the hypothetical position corresponding to the minimum difference, and this position corresponds to the actual precise position of the fault;

[0043] Step 7: Considering that the results obtained by using a single amplitude information may contain pseudo roots, the theoretical phase difference and actual phase difference of the same high-frequency component of the corresponding measuring point are calculated while calculating the amplitude ratio of the corresponding measuring point. The precise fault location is solved in the same way, and then the intersection of the results calculated by the two methods is taken. This is sufficient to ensure that the precise fault location results do not contain pseudo roots in various situations.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not intended to limit the present invention. A person skilled in the art should understand that the specific implementation of the present invention can be modified or replaced by equivalents, but these modifications or changes are within the scope of protection of the pending claims.

Claims

1. A distribution network cable early fault location system based on transient disturbance, characterized in that: The system includes an information transmission module, a transient disturbance signal detection module, a transient disturbance signal identification module, a fault warning module, a fault data processing module and a cable fault locating module; the information transmission module transmits the information of the measuring point to the transient disturbance signal detection module and the fault data processing module; the transient disturbance signal detection module is connected to the transient disturbance signal identification module, the transient disturbance signal identification module identifies the detected transient disturbance signal and preliminarily determines the possibility of a fault; the transient disturbance signal identification module is connected to the fault warning module, the fault warning module sends a warning signal when the transient disturbance signal identification module identifies that the possibility of a fault is too high; the transient disturbance signal identification module is also connected to the fault data processing module, the fault data processing module further determines and processes the identified suspected fault information; the fault data processing module is connected to the cable fault locating module, the cable fault locating module locates the cable fault determined by the fault data processing module to quickly obtain the specific location of the cable fault point; The control method of the distribution network cable early fault location system comprises the following steps: Step 1: For the installed transient voltage and current signal transformers, a combination of modeling analysis and experimental testing is used to conduct a systematic theoretical analysis of the transient traveling wave signal transmission characteristics generated by early faults; Step 2: According to the basic principle of transient voltage and current signal transformer, establish its equivalent circuit model, conduct transmission test on fault transient traveling wave, and obtain the transmission gain, response delay and waveform distortion parameters of the transformer to the signal according to the test; Step 3: Process the transient traveling wave signals on the primary and secondary sides, and conduct comparative analysis to reveal the nature of the changes in the secondary side signals when the transient traveling wave passes through the transformer. Process the secondary side fault signal to identify the information contained in the transient traveling wave head signal generated by the early fault. Step 4: Determine the high-frequency component ω of the first wave head of the current traveling wave at each measuring point after the distribution network fails i The difference in the distribution of polarity η and energy E between the fault line section and the non-fault line section is used to construct the fault line section identification indicator factor ξ f As shown below: Among them, ξ f is the fault section identification indicator factor detected at each current traveling wave measurement point, η i and γ i is the corresponding weight, which can be predetermined according to the actual fault situation and the influence of the mutual inductor on the traveling wave propagation characteristics; the measurement points corresponding to the first three largest fault section identification factor values ​​are selected as the section where the fault line is located; Step 5: Using the early fault transient signals measured at all measuring points on the fault section line, considering the shortest propagation path and the corresponding time of the signal mutation point, reasonably determine the signal calculation data window length and the spectrum range of the high-frequency component to be extracted, and use S transform to extract the amplitude and phase information of the high-frequency component of the first wave head of the transient traveling wave signal at each measuring point; the frequency of the first wave head of the traveling wave detected at any measuring point A is ω i The high frequency signal can be expressed as follows: in, and θ Ai =-β i x is the frequency of the traveling wave head signal obtained at the measuring point A, and ω i The amplitude and phase of the high-frequency signal; Step 6: Using the virtual bus method, when a fault occurs at a certain position of the line between different measurement points, the difference between the theoretical high-frequency component amplitude ratio calculated according to the above formula and the actual amplitude ratio of the same high-frequency component calculated by S transform is considered. The idea of ​​iterative search is used to solve the hypothetical position corresponding to the minimum difference, and this position corresponds to the actual precise position of the fault; Step 7: Considering that the results obtained by using a single amplitude information may contain pseudo roots, the theoretical phase difference and actual phase difference of the same high-frequency component of the corresponding measuring point are calculated while calculating the amplitude ratio of the corresponding measuring point. The precise fault location is solved in the same way, and then the intersection of the results calculated by the two methods is taken. This is sufficient to ensure that the precise fault location results do not contain pseudo roots in various situations.

2. A distribution network cable early fault location system based on transient disturbance according to claim 1, characterized in that: The transient disturbance signal detection module and the transient disturbance signal identification module are based on the operation of statistical pattern recognition of the interference signal of the expert system to collect effective fault signals.

3. The distribution network cable early fault location system based on transient disturbance according to claim 1 is characterized in that: The information transmission module can perform signal conversion and data transmission on the fault signals collected by the measuring points between the modules.

4. A distribution network cable early fault location system based on transient disturbance according to claim 1, characterized in that: The transient disturbance signal detection module can detect the grounding line current, zero-sequence voltage, and zero-sequence current of the cable, which are electrical characteristic quantities reflecting the electrical characteristics of the cable.

5. The distribution network cable early fault location system based on transient disturbance according to claim 1 is characterized in that: The transient disturbance signal recognition module can use neural networks and support vector machines to identify multiple types of disturbances on signals.

6. A distribution network cable early fault location system based on transient disturbance according to claim 1, characterized in that: The fault data processing module and the cable fault locating module judge and locate the early-stage fault of the cable based on the transient disturbance signal.

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