A medium voltage distribution network fault rapid positioning device and positioning method

Abstract

The present invention discloses a medium-voltage distribution network fault rapid positioning device in the field of electric power equipment, comprising a monitoring front end, a monitoring back end and a power supply module. The monitoring front end comprises a data acquisition module, a data processing module and a data transmission module. The monitoring back end comprises a server and a computer system. The output end of the data acquisition module is connected to the data transmission module via the data processing module. The data transmission module is connected to the monitoring back end. The power supply module supplies power to the monitoring front end and the monitoring back end. The present invention solves the problems of low accuracy, low reliability, complexity and time-consuming in traditional distribution network fault positioning methods, and can be used in distribution network monitoring.

Description

Technical Field

[0001] The present invention relates to a distribution network fault locating technology, and in particular to a distribution network fault rapid locating device and a locating method. Background Art

[0002] The distribution network operates directly in a complex natural environment, and various faults are unavoidable. When a distribution network fails, in order to improve the safety and reliability of the distribution network and minimize the damage to the power system, it is necessary to eliminate the fault in a timely manner and reduce the scope of power outage. The rapid and accurate location of the fault point is the prerequisite for timely troubleshooting.

[0003] The distribution network has a complex topology and many branches, and its fault location has always been a difficult point. In the past, manual line fault troubleshooting methods were labor-intensive and time-consuming, and easily led to the inability to restore power supply in the short term. At present, the fault location method based on transient traveling waves has strong adaptability and high positioning accuracy, and has been well applied in the fault location of transmission lines. However, for more complex distribution network structures, especially when the fault point is close to the distribution network branch node, the calculation error of the traditional single-end and double-end traveling wave location methods will significantly affect the reliability of the positioning results. Although the traditional multi-end traveling wave location method has strong applicability and does not have the problem of false fault points, it still requires complex matrix calculations and is difficult to apply effectively. Summary of the invention

[0004] The purpose of the present invention is to provide a medium voltage distribution network fault rapid location device and location method, so as to solve the problems that the traditional distribution network fault location method has low accuracy, low reliability and is complicated and time-consuming.

[0005] The object of the present invention is achieved as follows: a medium-voltage distribution network fault rapid positioning device and positioning method, the positioning device includes a monitoring front end, a monitoring back end and a power supply module, the detection front end includes a data acquisition module, a data processing module and a data transmission module, the monitoring back end includes a server and a computer system, the output end of the data acquisition module is connected to the data transmission module via the data processing module, the data transmission module is connected to the monitoring back end, and the power supply module supplies power to the monitoring front end and the monitoring back end;

[0006] The positioning method comprises the following steps:

[0007] Step 1) monitoring the traveling wave data of the terminal nodes and branch nodes of the transmission line in real time through a data acquisition module;

[0008] Step 2) When a fault occurs in the distribution network system, the traveling wave arrival time of the known monitoring nodes on the line and the traveling wave arrival time of the fault point are extracted, and the correlation coefficient is used to measure the proximity of the traveling wave arrival time series of the fault point location and the traveling wave arrival time series of the known nodes, so as to determine the location of the fault point range based on the proximity.

[0009] As a further limitation of the present invention, in the monitoring front end, the data acquisition module includes multiple high-speed data acquisition channels, which are used to send the operating status signal of the front-end line to the high-speed parallel data acquisition system via the voltage / current sensor, the signal conditioning circuit and the high-speed analog-to-digital conversion circuit, and the high-speed parallel data acquisition system is connected to the memory and the positioning module.

[0010] As a further limitation of the present invention, the voltage / current sensor uses a mutual inductance coil to achieve non-contact measurement of voltage / current on the transmission line, the signal conditioning circuit processes the voltage signal output by the voltage / current sensor to meet the analog voltage input range of the analog-to-digital conversion circuit, the analog-to-digital conversion circuit uses a 12-bit ADC with a sampling rate of 20MHz to meet the real-time high-speed conversion of the traveling wave signal, the high-speed parallel data acquisition system collects the obtained digital signal and makes a judgment, and when it is judged as a fault signal, the positioning module is called to obtain information such as the time and location of the fault, and stores it in a high-speed memory together with the fault voltage / current waveform data.

[0011] As a further limitation of the present invention, in the monitoring front end, the data acquisition module uses an ARM chip to analyze and process the data information obtained by the data acquisition module, and then communicate with the monitoring background through the data transmission module. The data transmission module uses GPRS wireless communication.

[0012] As a further limitation of the present invention, in the monitoring front end, the system power supply module is compatible with the standard power supply interface provided by the remote terminal unit, obtains electrical energy from the remote terminal unit device, and provides power drive with corresponding conditions for each module.

[0013] As a further limitation of the present invention, the computer system and server of the monitoring background are used to provide a real-time monitoring and management system based on LABVIEW, receive, record and analyze the voltage / current waveform, time, location and other data information transmitted back by the front end, realize real-time online monitoring of the transmission line voltage / current and fault location based on the geographic information system, and issue corresponding control and protection instructions according to the real-time monitoring information and background work requirements.

[0014] As a further limitation of the present invention, the correlation coefficient in step 2) is selected from the Pearson correlation coefficient r, which is expressed as:

[0015]

[0016] Among them, the time sequence of the fault point traveling wave reaching all monitoring nodes is A = {a1, a2..a n}, it is known that the time sequence of a single monitoring node reaching all monitoring nodes is B = {b1, b2..b n}, n is the sequence length, a, b represents the average value of sequence A and sequence B. The closer the coefficient is to 1, the closer the fault point is to the known node. When the coefficient is 1, the fault point overlaps with the known node.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention adopts a mutual inductance coil as a voltage / current sensor to achieve non-contact measurement of electrical signals of a power transmission line;

[0019] The high-speed parallel data acquisition system is used as the core control chip of the high-speed data acquisition module. The high-speed parallel data acquisition system, a pure hardware system, works in parallel and is significantly superior to DSP, ARM and other control chips in terms of high-speed data acquisition. In addition, large-scale integrated circuits based on high-speed parallel data acquisition systems have developed rapidly in recent years. While the speed, scale and performance are continuously improved, the price is continuously reduced, and the cost performance is very high.

[0020] SDRAM is used as the memory. The access clock rate of the third-generation SDRAM can reach 800MHz, and the storage capacity is nearly several GB, which is very suitable for high-speed data caching;

[0021] At the same time, the front-end data acquisition module of this system has multiple data acquisition channels, and its GPS module can also provide information such as the time and location of the fault, so that the data of this fault location system can be further used for subsequent analysis and processing such as fault type judgment and fault point location;

[0022] ARM is used as the core control chip of the data processing module. The current ARM system has increasingly consolidated its position in the field of wireless communications with its low power consumption, high cost performance and strong data processing capabilities.

[0023] The positioning method does not have the problem of false fault points, has high accuracy, strong applicability, and avoids complex matrix calculations. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the positioning device in the present invention.

[0025] Figure 2 for Figure 1 The hardware system structure block diagram of the monitoring front end in the positioning device is shown.

[0026] Figure 3 It is a typical multi-branch power distribution network topology.

[0027] Figure 4 for Figure 3 System diagram of a device for quickly locating faults at a mid-port or branch node. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments.

[0029] like Figure 1 As shown, the present invention proposes a medium-voltage distribution network fault rapid positioning device, including a monitoring front end ① and a monitoring back end ②; the monitoring front end ① is composed of a data acquisition module 1, a data processing module 2, a data transmission module 3 and a corresponding system power supply module 4; the system power supply module 4 is connected to the data acquisition module 1, the data processing module 2 and the data transmission module 3, and is used to supply power to the data acquisition module 1, the data processing module 2 and the data transmission module 3; the output end of the data acquisition module 1 is connected to the data transmission module 3 through the data processing module 2, and the data transmission module 3 is connected to the monitoring back end ②; the monitoring back end ② is composed of a computer system and a server database system.

[0030] like Figure 2 As shown in the figure, the hardware system configuration structure of the monitoring front end ① is as follows:

[0031] The data acquisition module 1 comprises a voltage / current sensor (1), a signal conditioning circuit (2), a high-speed analog-to-digital conversion circuit (3), a high-speed parallel data acquisition system (4) with FPGA as the core, a storage module (5) and a GPS positioning and timing module (6); the output end of the voltage / current sensor (1) is connected to the FPGA (4) through the signal processing circuit (2) and the analog-to-digital conversion circuit (3) in sequence, and the FPGA (4) is connected to the storage (5) and Beidou / GPS (6); the voltage / current sensor (1) is a non-contact sensor based on a mutual inductance coil, and the sensor has high detection accuracy and can manufacture a special fault voltage / current signal according to the fault voltage / current characteristics within the fault voltage / current spectrum range. The invention relates to a circuit for measuring the voltage of a voltage / current sensor and a circuit for measuring the voltage of a voltage / current sensor. The circuit for measuring the voltage of the voltage / current sensor is provided with a fixed coil and can realize non-contact measurement of electrical signals. The signal conditioning circuit (2) processes the voltage signal output by the voltage / current sensor so that the voltage signal meets the analog voltage input range of the analog-to-digital conversion circuit (3). The high-speed analog-to-digital conversion circuit (3) adopts a 12-bit ADC with a sampling rate of 20 MHz, which is sufficient to meet the real-time conversion of the traveling wave signal. After the front-end signal is converted into the analog-to-digital signal, the FPGA (4) collects the obtained digital signal and performs voltage / current signal judgment. When it is judged to be a fault voltage / current signal, the GPS module (6) is called to obtain the time, location and other information of the fault occurrence moment, and stores the information together with the fault voltage / current waveform data in the extended high-speed memory (5).

[0032] The data processing module 2 is based on ARM and controls the collection and transmission of voltage / current data at the transmission line nodes. ARM connects FPGA and data transmission module 3. Data transmission module 3 can use GPRS communication or other wireless communication technologies. When working in the online monitoring mode, the data processing module 2 transmits the data collected by the data acquisition module 1 to the monitoring background through the data transmission module 3 in real time②. The system power supply module 4 is compatible with the standard power supply interface provided by the RTU device, obtains power from the RTU switch device, and ensures the power supply requirements of other modules.

[0033] like Figure 3 As shown, the typical multi-branch distribution network topology is very complex, and the fault rapid location device monitoring front end ① provided by the present invention can be installed at its port or branch node.

[0034] like Figure 4 As shown, the monitoring front end ① is installed on the RTU cabinet, and its sensor coil is installed on the outdoor transmission line node. The monitoring front end ① can simultaneously collect the voltage / current waveforms of multi-phase lines, and transmit information with the monitoring background ② through wireless communication modes such as GPRS. The computer of the monitoring background ② receives, stores and analyzes the voltage / current waveform, time, location and other data information sent back by the monitoring front end ①, and realizes real-time online monitoring of the voltage / current of the transmission line and fault location based on GIS through the LABVIEW operating platform, and issues corresponding control and protection instructions according to the real-time monitoring information and background work requirements.

[0035] A method for quickly locating faults in a medium voltage distribution network comprises the following steps:

[0036] Step 1) monitoring the traveling wave data of the terminal nodes and branch nodes of the transmission line in real time through a data acquisition module;

[0037] Step 2) When a fault occurs in the distribution network system, the traveling wave arrival time of the known monitoring nodes on the line and the traveling wave arrival time of the fault point are extracted, and the proximity of the traveling wave arrival time series of the position fault point and the traveling wave arrival time series of the known node is measured by the correlation coefficient, and the fault point range is determined based on the proximity. The correlation coefficient is the Pearson correlation coefficient r, and its expression is:

[0038]

[0039] Among them, the time sequence of the fault point traveling wave reaching all monitoring nodes is A = {a1, a2..a n}, it is known that the time sequence of a single monitoring node reaching all monitoring nodes is B = {b1, b2..b n}, n is the sequence length, a, b represents the average value of sequence A and sequence B. The closer the coefficient is to 1, the closer the fault point is to the known node. When the coefficient is 1, the fault point overlaps with the known node.

[0040] The principle of this positioning method is as follows:

[0041] 1. Relationship between traveling wave arrival time and fault distance

[0042] Typical multi-branch distribution network topology is as follows: Figure 3 As shown in the figure, the line end measurement node is represented by Oi (i = 1, 2…n), and the line branch node is represented by Pj (j = 1, 2…m). A synchronous traveling wave measurement device is installed at the line end measurement node to obtain the traveling wave signal. Considering the complexity of traveling wave propagation in the distribution network, this paper only analyzes the propagation characteristics of the initial traveling wave.

[0043] Given an arbitrary position G, assuming that the time t of the traveling wave starting from point G to reach a certain measurement node Oi in the network is i Satisfies the following relationship:

[0044]

[0045] Where, t i represents the time when the traveling wave reaches the measurement node Oi, t0 represents the time when the fault occurs, l i represents the distance from point G to point Oi, v GOi It represents the speed of the traveling wave propagating along the path GOi. The speed of the traveling wave is related to the line parameters. In a single-line distribution network, the speed of the fault traveling wave in each branch line is the same, and the speed of the traveling wave can be represented by a constant v. Then formula (1) can be simplified as:

[0046] l i =kt i +b (2)

[0047] In the formula, k=v, b=-vt0.

[0048] The time it takes for the traveling wave to reach all the measurement nodes starting from point G can be expressed as the sequence T = {t1, t2..t n}, and the distance from point G to all measurement nodes can be represented by the sequence L = {l1,l2...l n}. Then T and L satisfy the relationship:

[0049] L=kT+b (3)

[0050] 2. Fault location principle

[0051] For any two points M and N on the distribution network, the distances to all measurement nodes can form a distance sequence X = {x1, x2..xn}, Y={y1,y2..y n}. The similarity of two distance sequences can measure the proximity of two points. When two points coincide, their similarity is 100%. The Pearson correlation coefficient r is used to characterize the similarity of two sequences, and its expression is:

[0052]

[0053] In the formula, n is the sequence length, Represents the average value of the sequence x(n), y(n). The expression of the average value is:

[0054]

[0055] From formulas (1) and (2), we can see that when the sequence X and T are in a linear relationship, that is: i =kt i +b(i=1,2...n), and k>0, then sequence T is used to replace sequence X, and the value of its Pearson correlation coefficient r remains unchanged. This relationship is defined as the replacement condition.

[0056] If M represents the fault point, its distance sequence L to the measurement node is an unknown quantity; N represents a known point on the line, and its distance sequence L' to the measurement node is a known quantity; the time when the fault traveling wave arrives at each measurement node can be obtained by obtaining the fault traveling wave through the synchronous traveling wave measurement device and analyzing the traveling wave signal, and its time sequence T to the measurement node is a known quantity; from the analysis in the previous section, it can be seen that the sequences L and T meet the replacement condition. That is, the similarity between the distance sequence of the fault point M and the distance sequence of the known point N is equivalent to the similarity between the time series of the fault point and the distance sequence of the known point.

[0057] Based on the above analysis, the fault point location problem is transformed into: set a series of nodes on the distribution network line, find one of the nodes so that the correlation coefficient between the distance series of the point and the time series of the fault point is 1, then the fault point coincides with the node; since the nodes are selected as discrete points, it is very likely that they cannot completely coincide with the fault point, then the node with the correlation coefficient closest to 1 is closest to the fault point, and this node is considered to be the fault point.

[0058] 3. Selection of known nodes

[0059] If a series of equidistant nodes are directly taken on the line, and the correlation coefficient between the distance sequence of each node and the fault traveling wave time series is solved, the amount of calculation will be very large. For this reason, some special nodes are first selected for correlation analysis to narrow the solution range of the fault point. All measurement nodes and branch nodes are selected to calculate the correlation between their distance sequence and the fault traveling wave time series. If the node with the largest absolute value of the correlation is the end measurement node, the fault point must be on the only branch line where the end measurement node is located; if the node with the largest absolute value of the correlation is a branch node, the fault point is on the three branch lines where the branch node is located.

[0060] 4. Fault location process

[0061] (1) After a fault occurs in the distribution network line, the synchronous traveling wave measurement device installed at the end of the line obtains the fault traveling wave waveform and absolute time stamp, and transmits the node location and traveling wave information of the device back to the central station.

[0062] (2) The central station processes the traveling wave signals returned by each measurement node and obtains the traveling wave head time of each measurement node.

[0063] (3) Based on the distribution network structure and the traveling wave head time of each measurement node, the fault location algorithm is used to solve and obtain the location result.

[0064] The method of the present invention is further verified and explained below through simulation.

[0065] In order to verify the method described in this paper, a 10KV distribution network simulation model is built using MATLAB / Simulink. Its topology is as follows: Figure 3 As shown; the lines in the simulation model are all distributed parameter models of overhead lines, and the line lengths are shown in Table 1; the measurement nodes O1~O7 are located at the distribution transformers at the end of each line, and the voltage traveling waves are collected with a sampling rate of 10MHz.

[0066] Table 1 Line length

[0067]

[0068]

[0069] 3.2 Simulation Results

[0070] This paper uses the wavelet transform method to extract the traveling wave head time. It is assumed that a single-phase grounding fault occurs on line c at a distance of 1.259 km from the starting point of the line, the initial time of the fault is t = 0.012s, and the grounding resistance Rg = 10Ω; in the fault location algorithm, the spacing of the known nodes is set to 200m, 100m and 50m respectively, and the location results are shown in Table 2.

[0071] Table 2 Positioning results of different node spacing

[0072]

[0073] As shown in Table 2, reducing the node spacing is beneficial to reducing the positioning error; however, the smaller the spacing, the more nodes there are, and the greater the amount of calculation. Since there is inevitably a difference between the given distribution network line length in the positioning system and the actual line length, it is meaningless to set the node spacing too small. When the node spacing is 50m, the positioning error does not exceed 50m. Therefore, the node spacing is set to 50m in the subsequent analysis.

[0074] In order to verify the robustness of the method described in this paper, a certain time error is added to the initial traveling wave arrival time of the O1 measurement node; the simulation results are shown in Table 3. It can be seen that with the increase of time error, the positioning error increases; the time error mainly comes from the time synchronization error of the traveling wave measurement device and the traveling wave head time extraction error. Therefore, this fault location method based on the traveling wave arrival time has high requirements on the synchronization of the traveling wave measurement device.

[0075] Table 3 Positioning results with different time errors

[0076]

[0077] 3.3 Accuracy Analysis

[0078] Among the faults in the distribution network, single-phase grounding faults account for about 80% of the total. Therefore, the present invention first takes the single-phase grounding fault as an example to verify the accuracy of the positioning method. Due to limited space, only the simulation results when the fault point is located at the middle line c and the end line h are given, as shown in Table 4.

[0079] Table 4. Location results of different fault locations

[0080]

[0081] According to Table 4, when the fault point is located at different positions of different lines, especially when the fault point is located near the branch node of the distribution network, it can be accurately located. It can be seen that this method does not have the problem of false fault points.

[0082] 3.4 Applicability Analysis

[0083] In order to verify the applicability of the method described in the present invention, fault points are set at several random locations in the distribution network, and the following parameters in the simulation model are changed in turn: 1) fault type; 2) initial time of fault occurrence; 3) fault grounding resistance, and the positioning results are analyzed.

[0084] The fault point is set on line d, 1.229 km away from the starting point of the line. The initial time of the fault is t = 0.012s, and the grounding resistance is Rg = 10Ω. In the simulation model, the fault types are modified to single-phase grounding, two-phase grounding, phase-to-phase short circuit, and three-phase short circuit faults. The positioning results are all: the line number of the fault point is d, and the fault point is 1.2 km away from the starting point of the line. It can be seen that this method is applicable to different fault types.

[0085] In the simulation model, a single-phase grounding fault point is set on line e at a distance of 3.823 km from the starting point of the line, and the grounding resistance Rg = 10Ω is given; the initial fault time t is set to 0.05s, 0.07s, 0.10s and 0.12s respectively to correspond to four different initial fault angles. The positioning results are all: the line number of the fault point is e, and the fault point is 3.8 km away from the starting point of the line. This shows that this method is not affected by the initial fault angle.

[0086] The magnitude of the fault grounding resistance has an important influence on fault location. To further verify the applicability of this method, a single-phase grounding fault point is set on line f at a distance of 6.225 km from the starting point of the line, and the initial fault time t = 0.012s. When the grounding resistance Rg is 10Ω, 50Ω, 100Ω and 200Ω respectively, the positioning results are all: the line number of the fault point is f, and the fault point is 6.2km away from the starting point of the line. This shows that this method is not affected by the magnitude of the fault grounding resistance.

[0087] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A method for quickly locating a fault in a medium-voltage distribution network, using a device for quickly locating a fault in a medium-voltage distribution network, comprising a monitoring front end, a monitoring back end and a power supply module, wherein the monitoring front end comprises a data acquisition module, a data processing module and a data transmission module, the monitoring back end comprises a server and a computer system, the output end of the data acquisition module is connected to the data transmission module via the data processing module, the data transmission module is connected to the monitoring back end, and the power supply module supplies power to the monitoring front end and the monitoring back end; In the monitoring front end, the data acquisition module includes a plurality of high-speed data acquisition channels, which are used to send the operation status signal of the front-end line to the high-speed parallel data acquisition system via the voltage / current sensor, the signal conditioning circuit and the high-speed analog-to-digital conversion circuit. The high-speed parallel data acquisition system is connected to the memory and the positioning module; The voltage / current sensor adopts a mutual inductance coil to realize non-contact measurement of voltage / current on the transmission line. The signal conditioning circuit processes the voltage signal output by the voltage / current sensor to meet the analog voltage input range of the analog-to-digital conversion circuit. The analog-to-digital conversion circuit adopts a 12-bit ADC with a sampling rate of 20MHz to meet the real-time high-speed conversion of the traveling wave signal. The high-speed parallel data acquisition system collects the obtained digital signal and makes a judgment. When it is judged as a fault signal, the positioning module is called to obtain the time and location of the fault, and store it in the high-speed memory together with the fault voltage / current waveform data; In the monitoring front end, the data acquisition module uses an ARM chip to analyze and process the data information obtained by the data acquisition module, and then communicate with the monitoring background through the data transmission module. The data transmission module uses GPRS wireless communication; The computer system and server of the monitoring background are used to provide a real-time monitoring management system based on LABVIEW, receive, record and analyze the voltage / current waveform, time and position sent back by the front end, realize the real-time online monitoring of the voltage / current of the transmission line and the fault location based on the geographic information system, and issue corresponding control and protection instructions according to the real-time monitoring information and the background work requirements, which is characterized by comprising the following steps: Step 1) real-time monitoring of the traveling wave data of the terminal nodes and branch nodes of the transmission line through the data acquisition module; Step 2) When a fault occurs in the distribution network system, the arrival time of the traveling waves of the known monitoring nodes on the line and the arrival time of the traveling waves at the fault point are extracted, and the proximity of the traveling wave arrival time series of the fault point to the traveling wave arrival time series of the known nodes is measured by the correlation coefficient. The fault point range is determined based on the proximity. The correlation coefficient is the Pearson correlation coefficient r, and its expression is: ； Among them, the time series of the fault point traveling wave reaching all monitoring nodes is: , it is known that the time series of a single monitoring node reaching all monitoring nodes is , n sequence length, , It represents the average value of sequence A and sequence B. The closer the coefficient is to 1, the closer the fault point is to the known node. When the coefficient is 1, the fault point overlaps with the known node.

Images