Fault positioning method based on carrier signal

Abstract

The invention discloses a fault positioning method based on a carrier signal, which is realized in a power line carrier remote meter reading system, the power line carrier remote meter reading system comprises a carrier machine with a carrier coupling unit and a network communication unit, and a power line, the carrier machine comprises a carrier host and at least one carrier extension, a high-speed data acquisition card for recording traveling wave signals and a data processing unit are additionally arranged in a carrier host, and the method comprises the specific steps that S1, the carrier host carries out clock time synchronization on each carrier extension; s2, all carrier extensions monitor signal waves on the power line by using the power line meter reading gap and send the signal waves to a carrier host; s3, the data processing unit filters the signal waves to obtain traveling wave signals, and the high-speed data acquisition card records the arrival time of the traveling wave signals; and S4, the data processing unit calculates corresponding fault point positions through the arrival time of the traveling wave signals in sequence, and then carries out comprehensive weighting processing on all the fault point positions to obtain accurate fault point positions.

Description

Technical Field

[0001] The invention belongs to the field of distribution network fault location, relates to a fault location method for an intelligent distribution network of an electric power system, and specifically relates to a fault location method based on a carrier signal. Background Art

[0002] With the rapid development of social economy and new power systems, users have higher and higher requirements for the reliability of power grids. The safety and reliability of distribution networks are directly related to the quality of national industrial and agricultural production, and directly affect the level of social economic development. With the development and continuous expansion of distribution networks, the occurrence of single-phase grounding faults directly affects the safety of urban electricity use. When a distribution network fails, the power supply unit needs to quickly and accurately find the fault location, take timely countermeasures to restore power supply, and reduce the economic losses caused by power outages caused by the fault. It can be seen that fast and accurate fault location technology is an important technology to ensure the safety and reliability of distribution networks, and plays a vital role in the development of smart distribution networks.

[0003] Due to its wide coverage, many nodes, and difficulty in construction, the smart distribution network requires an effective wide area communication network to transmit data and control and adjustment commands between the system master station and the distribution terminal unit or on-site intelligent device. The communication network for distribution is an important part of the power system network platform and a downward extension of the power backbone communication network. There are more and more new power grid smart terminals with a wide coverage. At present, communication technologies such as optical fiber and 4G / 5G wireless cannot adapt to scenes such as underground garages and buried cables. The power line carrier communication technology can make full use of the existing physical network of the power grid for communication, and has the characteristics of small investment, strong flexibility, and high network reliability. In addition, the carrier terminal can be connected to any measurement and control point in the power grid, especially the medium-voltage power line carrier terminal is installed near the transformer, so as to realize on-site fault monitoring.

[0004] Therefore, power line carrier communication is of great significance in smart distribution network communication and fault diagnosis application scenarios. Summary of the invention

[0005] The purpose of the present invention is to solve the problems that when a fault occurs in the intelligent distribution network, the manual line patrol mode is inefficient and seriously affects the power supply quality. A fault location method based on carrier signal is designed to perform fast and accurate positioning to improve the reliability of power grid operation and reduce economic losses.

[0006] The technical solution adopted by the present invention is a fault location method based on carrier signals, which is implemented in a power carrier remote meter reading system. The power carrier remote meter reading system includes a carrier machine having a carrier coupling unit and a network communication unit, and a power line. The key is that the carrier machine includes a carrier host and at least one carrier extension, and a high-speed data acquisition card and a data processing unit for recording traveling wave signals are added to the carrier host. On this basis, the specific steps of the fault location method are as follows:

[0007] S1. The carrier host synchronizes the clock of each carrier extension through the network communication unit;

[0008] S2, the carrier coupling units in all carrier extensions monitor all signal waves on the power line during the power line meter reading interval, and send all collected signal waves to the carrier host;

[0009] S3, the data processing unit of the carrier host filters all received signal waves to obtain the traveling wave signal generated by the power line fault, and at the same time the high-speed data acquisition card records the arrival time of the traveling wave signal sent by all carrier extensions;

[0010] S4. The data processing unit of the carrier host calculates the corresponding fault point location through the arrival time of the traveling wave signals sent by all carrier extensions in turn, and then performs comprehensive weighted processing on all fault point locations to obtain the accurate fault point location.

[0011] Furthermore, in the above step S3, the specific method in which the data processing unit of the carrier host filters all received signal waves is:

[0012] S31, perform signal demodulation: the signal wave that can be demodulated is the carrier signal, and the signal wave that cannot be demodulated is regarded as a suspected traveling wave signal, and the next step of judgment is performed;

[0013] S32, periodicity judgment: if the suspected traveling wave signal is a non-periodic signal, continue to judge it as a suspected traveling wave signal in the next step, and exclude periodic signals;

[0014] S33, screening out suspected traveling wave signals with high energy density for further judgment, and excluding signal waves with low energy density;

[0015] S34, screening out suspected traveling wave signals in the high frequency band for further judgment, and excluding low frequency band signal waves;

[0016] S35, screening out suspected traveling wave signals belonging to asymmetric pulse signals as the final traveling wave signals generated by the power line fault, and excluding signal waves belonging to symmetric pulse signals.

[0017] Furthermore, in the above-mentioned step S33, the above-mentioned high energy density refers to energy density ≥90%, and the above-mentioned low energy density refers to energy density <90%; in the above-mentioned step S34, the above-mentioned high frequency band is frequency ≥1MHz, and the above-mentioned low frequency band is frequency <1MHz.

[0018] Furthermore, in the above step S4, the data processing unit of the carrier host calculates the corresponding fault point location through the arrival time of the traveling wave signal sent by all carrier extensions in turn, and then performs comprehensive weighted processing on all fault point locations to obtain the accurate fault point location. The specific processing method is as follows:

[0019] S41, time difference calculation: the data processing unit of the carrier host calculates the arrival time difference of all carrier extensions, and calculates the corresponding fault point location according to the arrival time difference;

[0020] S42, error preprocessing, eliminating abnormal values;

[0021] S43, positioning and solving: using Chan algorithm, Taylor series expansion or maximum likelihood estimation to solve the coordinates of the fault point;

[0022] S44, result optimization: Smoothly output the specific fault location through data fusion algorithm.

[0023] Preferably, a geometric constraint screening method is used in the above step S42.

[0024] Specifically, in the above step S1, the clock is synchronized to control the clock error within 1 microsecond.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] When an electromagnetic wave is incident on the surface of a conductor, since the electric field has a tangential component relative to the conductor surface, this will excite the surface current and propagate along the conductor surface to form a surface traveling wave. When this surface traveling wave encounters a discontinuity, it will radiate in all directions to form a backscattering field, which is one of the foundations of traveling wave detection. The principle of the traveling wave fault distance measurement method is to use the time it takes for the traveling wave signal generated by the fault to travel back and forth between the fault point and the busbar to calculate the fault distance. The essence of the traveling wave signal is the voltage wave and current wave propagating along the power line, which can be divided into steady-state traveling waves and transient traveling waves.

[0027] Among them, steady-state traveling waves are traveling waves generated by the power supply and propagating along the line when the power system is operating normally; transient traveling waves are traveling waves that suddenly appear and then gradually disappear when the power system encounters disturbances such as short circuits, circuit breaks, and lightning strikes. They are the characteristics of power system failures. The transient traveling waves at the fault point propagate to both ends of the line at the same time. When encountering impedance discontinuities, reflections and refractions will occur. This is the traveling wave theory of the power system. By detecting these reflected and refracted traveling waves, the location of the fault point can be determined.

[0028] The present invention utilizes the high-precision hardware timing module provided on the carrier machine, and the carrier machine host and slave machine can achieve a timing error of less than 1 microsecond. The specific method is to synchronize the clocks between the carrier machines with high precision. When a distribution line fails, the output traveling wave signal enters the carrier machine device through a coupler, and a high-speed data acquisition circuit unit is used to record the fault current traveling wave signal. The traveling wave single-end or double-end detection method is used to obtain the location of the fault point. After the data processing unit is installed on the carrier machine, the specific points are synchronized with the precise time at both ends of the carrier machine itself. At the same time, since the high-frequency signal of the carrier is sensitive to line faults, when encountering a fault point, the carrier machine can effectively distinguish the traveling waves and other interference signals generated by the fault by receiving the signal and analyzing it. In addition, the carrier terminal can be connected to any measurement and control point in the power grid, especially the medium-voltage power line carrier terminal is installed near the transformer, thereby realizing on-site fault monitoring. Therefore, power line carrier communication is of great significance in the application scenarios of intelligent distribution network communication and fault diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the fault location method of the present invention. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example

[0032] The fault location method based on carrier signal of the present invention needs to be implemented in a power carrier remote meter reading system. The power carrier remote meter reading system of the prior art includes a carrier machine having a carrier coupling unit and a network communication unit, and a power line. The carrier machine of the present invention needs to include a carrier host and at least one carrier extension. The present invention needs to add a high-speed data acquisition card and a data processing unit for recording traveling wave signals in the carrier host. On this basis, the specific steps of the fault location method of the present invention are as follows:

[0033] S1. The carrier host synchronizes the clock of each carrier extension through the network communication unit, and the clock synchronization controls the clock error within 1 microsecond.

[0034] S2. The carrier coupling units in all carrier extensions monitor all signal waves on the power line during the power line meter reading intervals, and send all collected signal waves to the carrier host.

[0035] S3. The data processing unit of the carrier host filters all received signal waves to obtain the traveling wave signal generated by the power line fault. At the same time, the high-speed data acquisition card records the arrival time of the traveling wave signal sent by all carrier extensions: The specific filtering process is:

[0036] S31, perform signal demodulation: the signal wave that can be demodulated is the carrier signal, and the signal wave that cannot be demodulated is regarded as a suspected traveling wave signal, and the next step of judgment is performed;

[0037] S32, periodicity judgment: if the suspected traveling wave signal is a non-periodic signal, continue to judge it as a suspected traveling wave signal in the next step, and exclude periodic signals;

[0038] S33, screening out suspected traveling wave signals with high energy density for the next step of judgment, and excluding signal waves with low energy density. The high energy density of the present invention refers to an energy density ≥ 90%, and the low energy density refers to an energy density < 90%;

[0039] S34, screening out suspected traveling wave signals in the high frequency band for the next step of judgment, and excluding low frequency band signal waves. The high frequency band of the present invention is a frequency ≥ 1 MHz, and the low frequency band of the present invention is a frequency < 1 MHz;

[0040] S35, screening out suspected traveling wave signals belonging to asymmetric pulse signals as the final traveling wave signals generated by the power line fault, and excluding signal waves belonging to symmetric pulse signals.

[0041] S4, the data processing unit of the carrier host calculates the corresponding fault point location through the arrival time of the traveling wave signal sent by all carrier extensions in turn, and then performs comprehensive weighted processing on all fault point locations to obtain the accurate fault point location, which specifically includes the following steps:

[0042] S41, time difference calculation: the data processing unit of the carrier host calculates the arrival time difference of all carrier extensions, and calculates the corresponding fault point location according to the arrival time difference;

[0043] S42, error preprocessing, eliminating abnormal values;

[0044] S43, positioning and solving: using Chan algorithm, Taylor series expansion or maximum likelihood estimation to solve the coordinates of the fault point;

[0045] S44, result optimization: Smoothly output the specific fault location through data fusion algorithm.

[0046] The above steps are further described below with a more specific embodiment:

[0047] In a certain power carrier remote meter reading system, there are carrier host A and carrier extension B. 1 、Carrier extension B 2 and carrier extension B 3 Each of the above-mentioned carrier machines includes a carrier machine with a carrier coupling unit and a network communication unit. The power carrier remote meter reading system in this embodiment also includes a power line. In addition, this embodiment adds a high-speed data acquisition card and a data processing unit for recording traveling wave signals in the carrier host.

[0048] A high-speed data acquisition card is a device used to convert analog signals into digital signals and collect and transmit data at a high rate. High-speed data acquisition cards usually have a high sampling rate and can capture rapidly changing signals. In this embodiment, the QT12136DC of Kunchi Technology is used. The high-speed data acquisition card has a sampling rate of 1GS / s and can provide high-resolution analog-to-digital conversion (ADC) to ensure data accuracy. It also has a 14-bit vertical resolution, 8GB storage space, and a large-capacity onboard memory to ensure that data can be stored and processed quickly and efficiently.

[0049] In order to meet the requirements of high-frequency signal transmission, the carrier frequency of each carrier machine is set to 100 kHz in this embodiment.

[0050] On the basis of the above, the process of the fault location method of the present invention is shown in the attached Figure 1 , the specific steps are:

[0051] S1, carrier host A to carrier extension B 1 、Carrier extension B 2 To carrier extension B M Clock synchronization is performed through a network communication unit, with a time synchronization accuracy of 0.1 microseconds.

[0052] S2, carrier extension B1, carrier extension B 2 To carrier extension B M The carrier coupling unit in the power line uses the power line meter reading gap to monitor all signal waves on the power line and sends all collected signal waves to the carrier host A.

[0053] S3, the data processing unit of the carrier host A filters the received traveling wave signal to obtain the traveling wave signal generated by the power line fault, and at the same time the high-speed data acquisition circuit unit records the arrival time of the traveling wave signal generated by the fault, specifically including:

[0054] S31, perform signal demodulation: the signal wave that can be demodulated is the carrier signal, and the signal wave that cannot be demodulated is regarded as a suspected traveling wave signal, and the next step of judgment is performed;

[0055] S32, periodicity judgment: if the suspected traveling wave signal is a non-periodic signal, continue to judge it as a suspected traveling wave signal in the next step, and exclude periodic signals;

[0056] S33, screening out suspected traveling wave signals with high energy density for the next step of judgment, and excluding signal waves with low energy density. The high energy density of the present invention refers to an energy density ≥ 90%, and the low energy density refers to an energy density < 90%;

[0057] S34, screening out suspected traveling wave signals in the high frequency band for the next step of judgment, and excluding low frequency band signal waves. The high frequency band of the present invention is a frequency ≥ 1 MHz, and the low frequency band of the present invention is a frequency < 1 MHz;

[0058] S35, screening out suspected traveling wave signals belonging to asymmetric pulse signals as the final traveling wave signals generated by the power line fault, and excluding signal waves belonging to symmetric pulse signals.

[0059] This is because the traveling wave signal is a transient process, while the carrier signal is a man-made signal with complete coding, modulation, and demodulation rules; the traveling wave signal is a non-periodic transient pulse, while the carrier signal is a periodic continuous waveform; the traveling wave signal energy is concentrated in the high frequency band, and the amplitude decays with frequency, while the carrier signal energy is concentrated near the carrier frequency, and the spectrum is symmetrical. Therefore, the traveling wave signal and the carrier signal can be distinguished based on these distinguishing features.

[0060] S4. The data processing unit of the carrier host calculates the corresponding fault point location through the arrival time of the traveling wave signals sent by all carrier extensions in turn, and then performs comprehensive weighted processing on the locations of all fault points to obtain the accurate fault point location:

[0061] S41, time difference calculation: The data processing unit of the carrier host calculates the arrival time difference of all carrier extensions, that is, TDOA, and the calculation formula is Δt ij =t i -t j , i and j represent any carrier extension, and the corresponding fault point location is calculated according to the arrival time difference:

[0062] Assume that the coordinates of the fault point are (1500,2000), and the fault point generates a traveling wave signal, which travels at the speed of light (about 3×10 5 km / s) along the line to carrier A point (0,0) and carrier B 1 Point (3000,0), B 2 point(0,4000) propagation;

[0063] Using the data acquisition card of the carrier extension, collect and calculate the traveling wave signal to reach the carrier machine B 1 The time of the point is △t 2 ≈2.35μs

[0064] Using the data acquisition card of the carrier extension, collect and calculate the traveling wave signal to reach the carrier machine B 2 The time of the point is △t 3 ≈3.01μs

[0065] Use the traveling wave signal to reach the carrier machine B 1 Point and carrier machine B 2 The coordinates of the fault point are calculated at the time of point (1015.2,1523.8), which is the initial estimate.

[0066] S42, error preprocessing, eliminating outliers:

[0067] In this embodiment, geometric constraint screening is used to remove abnormal values. The principle is: according to the geometric relationship between each host and extension, the physical reasonable range of the distance difference Ti1=c·△t corresponding to each TDOA measurement value is calculated; if it exceeds this range, it is regarded as an abnormal value and removed. The specific steps are:

[0068] Step 1: Calculate the relative distance between each host and extension:

[0069] A(0,0) and B 1 The distance DAB of (3000,0) 1 =3000 m;

[0070] A(0,0) and B 2 (0,4000) distance DAB 2 =4000 meters.

[0071] Step 2: Set the distance difference threshold:

[0072] For △t 2 (B 1 Relative to the TDOA of A), requiring |r 21 |≤DAB 1 ;

[0073] For △t3(B 2 Relative to the TDOA of A), requiring |r 31 |≤DAB 2 .

[0074] Step 3: Eliminate outliers:

[0075] If | r 21 |>3000m or |r 31|>4000 meters, the corresponding △t is discarded and the valid measurement value is retained for subsequent positioning.

[0076] If the input △t2=13.33μs (corresponding to r=4.0km), since 4.0km>DAB 1 =3.0 km, it was determined to be an outlier and was removed.

[0077] S43, positioning and solving: using Chan algorithm, Taylor series expansion or maximum likelihood estimation to solve the coordinates of the fault point. This embodiment uses Chan algorithm as an example for explanation:

[0078] Step 1: Calculate the distance difference, expressed as T:

[0079] T 21 =c·△t2=0.3×2350=705 meters,

[0080] T 31 =c·△t3=0.3×3010=903 meters.

[0081] Step 2: Construct a linear equation system and linearize the TDOA equation:

[0082]

[0083] In matrix form:

[0084]

[0085] Step 3: First step weighted least squares (WLS 1 )

[0086] Assuming the covariance matrix W = I, the initial estimate is:

[0087]

[0088] Step 4: The second step is weighted least squares (WLS 2 )

[0089] Calculate the initial distance:

[0090]

[0091] Update equation:

[0092]

[0093] Solving for the final estimate:

[0094]

[0095] S44. Result optimization:

[0096] The specific fault location is smoothly output through the data fusion algorithm. The result comparison and accuracy analysis are shown in Table 1.

[0097] Table 1: Results comparison and accuracy analysis table

[0098]

[0099] Conclusion: Through the two-step optimization of Chan algorithm, the positioning error is significantly reduced, and the final estimated value is closer to the actual fault point coordinates.

[0100] It can be seen that through the above steps, this embodiment obtains a more accurate fault point location, and can notify the operation and maintenance personnel to go to the site for inspection and processing, repair the fault in time and restore the normal operation of the line, which greatly improves the fault handling efficiency and power supply reliability of the distribution network, and reduces power outage time and economic losses.

Claims

1. A fault location method based on carrier signal, implemented in a power carrier remote meter reading system, the power carrier remote meter reading system comprising a carrier machine having a carrier coupling unit and a network communication unit, and a power line, characterized in that: The carrier machine includes a carrier host and at least one carrier extension. A high-speed data acquisition card and a data processing unit for recording traveling wave signals are added to the carrier host. On this basis, the specific steps of the fault location method are as follows: S1. The carrier host synchronizes the clock of each carrier extension through the network communication unit; S2, the carrier coupling units in all carrier extensions monitor all signal waves on the power line during the power line meter reading interval, and send all collected signal waves to the carrier host; S3, the data processing unit of the carrier host filters all received signal waves to obtain the traveling wave signal generated by the power line fault, and at the same time the high-speed data acquisition card records the arrival time of the traveling wave signal sent by all carrier extensions; S4. The data processing unit of the carrier host calculates the corresponding fault point location through the arrival time of the traveling wave signals sent by all carrier extensions in turn, and then performs comprehensive weighted processing on all fault point locations to obtain the accurate fault point location.

2. A fault location method based on carrier signal according to claim 1, characterized in that: In step S3, the specific method in which the data processing unit of the carrier host filters all received signal waves is: S31, perform signal demodulation: the signal wave that can be demodulated is the carrier signal, and the signal wave that cannot be demodulated is regarded as a suspected traveling wave signal, and the next step of judgment is performed; S32, periodicity judgment: if the suspected traveling wave signal is a non-periodic signal, continue to judge it as a suspected traveling wave signal in the next step, and exclude periodic signals; S33, screening out suspected traveling wave signals with high energy density for further judgment, and excluding signal waves with low energy density; S34, screening out suspected traveling wave signals in the high frequency band for further judgment, and excluding low frequency band signal waves; S35, screening out suspected traveling wave signals belonging to asymmetric pulse signals as the final traveling wave signals generated by the power line fault, and excluding signal waves belonging to symmetric pulse signals.

3. A fault location method based on carrier signal according to claim 2, characterized in that: In the step S33, the high energy density refers to energy density ≥ 90%, and the low energy density refers to energy density < 90%; in the step S34, the high frequency band is frequency ≥ 1 MHz, and the low frequency band is frequency < 1 MHz.

4. The fault location method based on carrier signal according to claim 1, characterized in that: In step S4, the data processing unit of the carrier host calculates the corresponding fault point location through the arrival time of the traveling wave signal sent by all carrier extensions in turn, and then performs comprehensive weighted processing on all fault point locations to obtain the accurate fault point location. The specific processing method is as follows: S41, time difference calculation: the data processing unit of the carrier host calculates the arrival time difference of all carrier extensions, and calculates the corresponding fault point location according to the arrival time difference; S42, error preprocessing, eliminating abnormal values; S43, positioning and solving: using Chan algorithm, Taylor series expansion or maximum likelihood estimation to solve the coordinates of the fault point; S44, result optimization: Smoothly output the specific fault location through data fusion algorithm.

5. A fault location method based on carrier signal according to claim 4, characterized in that: In step S42, a geometric constraint screening method is used.

6. A fault location method based on carrier signal according to claim 1, characterized in that: In step S1, the clock is synchronized to control the clock error within 1 microsecond.

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