Non-contact current sensor, fault monitoring device and method

Abstract

The present invention relates to a non-contact current sensor. The housing is columnar with a hollow interior and open ends at both ends, made of aluminum and longitudinally distributed. Two end caps respectively seal the ports at both ends of the housing, made of resin. The iron core is vertically arranged inside the housing and consists of an upper inner core and a lower inner core. The upper inner core is made of a high magnetic permeability material, and the lower inner core is made of a low magnetic permeability material. The enameled wire is wound around the upper inner core and the lower inner core, and an external tap is provided at the transition between the upper inner core and the lower inner core. One end of the first integrating resistor is electrically connected to the external tap, and the other end is electrically connected to the tap where the enameled wire winds out of the lower inner core. One end of the second integrating resistor is electrically connected to the tap where the enameled wire winds out of the upper inner core, and the other end is electrically connected to the common end of the tap where the enameled wire winds out of the lower inner core and the first integrating resistor. The beneficial effect of the present invention is that it can monitor small current signals in the power grid, ensure the accuracy of fault diagnosis, and facilitate subsequent effective pre-warning.

Description

Technical Field

[0001] The present invention relates to the technical field of power grids, and particularly to a non-contact current sensor, a fault monitoring device and a method. Background Art

[0002] The rapid development of the national economy has put extremely high requirements on the power supply stability of transmission lines. Transmission lines span long distances and the line corridor environment varies greatly. During the operation of transmission lines, they are extremely vulnerable to interference from factors such as lightning strikes and external damage, resulting in tripping. How to quickly restore power supply after a line trip and improve the satisfaction of power supply services has always been a concern in power grid operation and maintenance work.

[0003] On the other hand, with the implementation of the new enterprise standard for distributed fault monitoring devices of transmission lines in the State Grid, combined with the actual engineering requirements, it is necessary to give early warnings for some predictable faults during the operation of transmission lines to reduce the line failure rate. Therefore, there is a need to monitor the high-frequency small current generated by predictable faults.

[0004] At present, distributed fault monitoring devices for transmission lines are widely used in the power grid. This device is directly installed on the line body and can realize the real-time monitoring and diagnosis functions of transmission line faults based on traveling wave current monitoring technology. Since the distributed fault monitoring terminal is installed on the line body, the monitoring equipment is installed in the form of power outage operation. However, in actual engineering applications, some important lines cannot be powered off immediately, which leads to certain limitations of this device in engineering applications. And live working has the defect of high cost. Therefore, a device that is convenient for engineering installation and can effectively measure the fault current of transmission lines is needed to measure small signals of fault traveling wave current and discharge current. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a non-contact current sensor, a fault monitoring device and a method to overcome the above deficiencies in the prior art.

[0006] The technical solution of the present invention to solve the above technical problem is as follows: A non-contact current sensor, comprising:

[0007] A housing, which is a columnar shape with a hollow interior and open ends at both ends, made of aluminum and longitudinally distributed;

[0008] Two end caps, which respectively cover the ports at both ends of the housing, made of resin;

[0009] An iron core, which is vertically arranged in the housing and consists of an upper inner core and a lower inner core. The upper inner core is made of a high magnetic permeability material, and the lower inner core is made of a low magnetic permeability material;

[0010] An enameled wire is wound around an upper inner core and a lower inner core, and an external tap is provided at the transition between the upper inner core and the lower inner core;

[0011] A first integrating resistor, one end of which is electrically connected to the external tap, and the other end is electrically connected to the tap where the enameled wire winds out of the lower inner core;

[0012] A second integrating resistor, one end of which is electrically connected to the tap where the enameled wire winds out of the upper inner core, and the other end is electrically connected to the common end of the tap where the enameled wire winds out of the lower inner core and the first integrating resistor.

[0013] The beneficial effects of the present invention are:

[0014] Since it is necessary to measure the abnormal discharge current waveform, and the discharge current waveform usually has a very low amplitude, at the milliampere level, the upper inner core is made of a high magnetic permeability material to ensure that the discharge current waveform can be effectively collected;

[0015] Since it is necessary to measure the fault current, and the fault current usually has a relatively high amplitude, to prevent the coil from occurring magnetic saturation and causing the output waveform to be distorted, the lower inner core is made of a low magnetic permeability material;

[0016] The combination of the external tap of the enameled wire at the transition between the upper inner core and the lower inner core, the tap where the enameled wire winds out of the lower inner core, and the first integrating resistor is used to measure the fault traveling wave current and the power frequency current; the combination of the tap where the enameled wire winds out of the upper inner core, the tap where the enameled wire winds out of the lower inner core, and the second integrating resistor is used to measure the abnormal discharge traveling wave current; so that the sensor can monitor the small current signals in the power grid, ensure the accuracy of fault diagnosis, and facilitate subsequent effective early warning.

[0017] On the basis of the above technical solutions, the present invention can also be improved as follows.

[0018] Further, the high magnetic permeability material is permalloy; the low magnetic permeability material is ABS.

[0019] Further, the number of turns of the enameled wire wound around the upper inner core is 20 - 60 turns, and the number of turns of the enameled wire wound around the lower inner core is 300 - 500 turns; the resistance value of the first integrating resistor is 30 - 70 Ω, and the resistance value of the second integrating resistor is 800 - 1200 Ω.

[0020] The effective effect of adopting the above two steps is: it can effectively ensure the measurement of the fault traveling wave current, the power frequency current, and the abnormal discharge traveling wave current.

[0021] A fault monitoring device: includes a host computer, a server communicatively connected to the host computer, and a plurality of monitoring terminals connected to the server;

[0022] The monitoring terminal includes a capacitive voltage divider sensor, a conditioning circuit, and a non-contact current sensor; the non-contact current sensor is vertically installed on the line tower, and the conditioning circuit is electrically connected to the tap of the lower inner core wound by the enameled wire, the tap of the upper inner core wound by the enameled wire, and the outer tap respectively; the capacitive voltage divider sensor is arranged below the energized three-phase conductors to be measured.

[0023] The further effective effects of adopting the above are as follows:

[0024] The monitoring terminals are distributed and installed on the towers, decomposing the long-distance line into several monitoring points, avoiding the fault location error caused by the attenuation of the traveling wave waveform after long-distance transmission to the upper computer, and effectively improving the positioning accuracy;

[0025] The non-contact current sensor is directly installed on the tower. The tower is at ground potential and has no electrical connection with the line body. Therefore, it can be installed while the line is energized and is not affected by the line power outage plan, making the engineering installation more flexible.

[0026] Further, the conditioning circuit includes a first-stage amplification circuit, a second-stage amplification circuit, a filtering circuit, a phase-shifting circuit, and a gain adjustment circuit. One output of the first-stage amplification circuit is sequentially connected to the filtering circuit, the phase-shifting circuit, and the gain adjustment circuit, and the other output of the first-stage amplification circuit is sequentially connected to the second-stage amplification circuit and the gain adjustment circuit.

[0027] Further, the capacitive voltage divider sensor includes:

[0028] A metal sheet, which is arranged below the line and forms a coupling capacitor C with the line 1 , and forms a capacitance to ground C with the ground 2 ;

[0029] A sampling capacitor C M1 , which is connected in series with a damping resistor R and then connected in parallel across the coupling capacitor C 1 at both ends.

[0030] The further effective effects of adopting the above are as follows: It has no electrical connection with the line body. Therefore, it can be installed while the line is energized and is not affected by the line power outage plan, making the engineering installation more flexible.

[0031] A fault monitoring method uses the above fault monitoring device; it specifically includes the following steps:

[0032] S100. The monitoring terminal regularly collects the traveling wave current and traveling wave voltage at non-fault moments of the line and temporarily stores them to obtain the traveling wave current waveform sequence xbdl 1 and the traveling wave voltage waveform sequence xbdy 1 ;

[0033] S200. The monitoring terminal fails and triggers to collect the traveling-wave current and traveling-wave voltage at the moment of line fault triggering, and stores them to obtain the traveling-wave current waveform sequence xbdl at the fault moment. 2 and the traveling-wave voltage waveform sequence xbdy 2 ;

[0034] S300. Calculate the correlation coefficients between the waveforms at the fault moment and the temporarily stored waveforms at non-fault moments to obtain the current correlation coefficient ρ dl1 and the voltage correlation coefficient ρ dy1 ;

[0035] S400. Convolve and reconstruct the waveform sequences stored at the fault moment to obtain a new traveling-wave current waveform sequence xbdl cz1 and the traveling-wave voltage waveform sequence xbdy cz1 , and calculate the current correlation coefficient ρ dl2 and the voltage correlation coefficient ρ dy2 ;

[0036] S500. Repeat step S400 n times to obtain the reconstructed traveling-wave current waveform sequence xbdl czn and the reconstructed traveling-wave voltage waveform group sequence xbdy czn , and each time it is repeated, calculate the correlation coefficients between the reconstructed waveform sequence and the non-fault moment waveform sequence ρ dln and ρ dyn , and respectively take the values with the largest absolute values of the correlation coefficients as the judgment reference data, denoted as max|ρ dln |, max|ρ dyn |;

[0037] S600. Take the maximum correlation coefficient of the traveling-wave voltage as the judgment basis;

[0038] Judge whether max|ρ dyn |≥k, 0≤k≤1;

[0039] If this condition is satisfied, the waveforms at the fault moment are all discarded. If not, enter S800;

[0040] If there is a situation where the traveling-wave voltage is not collected at the fault moment or non-fault moment, use the traveling-wave current as the judgment basis:

[0041] Judge whether max|ρ dln |≥k, 0≤k≤1;

[0042] If this condition is satisfied, the waveforms at the fault moment are all discarded. If not, enter S700;

[0043] S700. Amplify, filter, phase-shift, and adjust the gain of the traveling-wave current at the fault triggering moment, and transmit it to the server;

[0044] S800. Judge the polarities of the traveling-wave voltages returned by two monitoring terminals among all the monitoring terminals on the same line. If they are of the same polarity, discard them and select two monitoring terminals again for judgment. If they are of different polarities, upload the waveforms to the host computer;

[0045] If no traveling-wave voltage is returned by the terminal, use the traveling-wave current as the judgment basis, and the judgment method is the same as that for the traveling-wave voltage;

[0046] If there is no data for both the traveling-wave voltage and the traveling-wave current, discard the terminals without data and select other terminals on the line.

[0047] Furthermore, in S200, the monitoring terminal fault triggering is triggered by the power-frequency voltage change threshold, the power-frequency current change threshold, or the traveling-wave voltage threshold.

[0048] Furthermore, the method of in-roll recombination in S400 is as follows:

[0049] Move the last sampling point of the waveform sequence to the first sampling point of the waveform sequence, and move the rest of the sampling points one position backward.

[0050] Furthermore, S700 is specifically as follows:

[0051] S810. All monitoring terminals upload the terminal operating condition information to the server;

[0052] S820. The server sorts the monitoring terminals on the same line in descending order of power consumption according to the operating condition information uploaded by the monitoring terminals;

[0053] S830. The server selects two monitoring terminals with the highest power consumption to send the pending trigger instruction, and the monitoring terminals receive the instruction and wait to be triggered;

[0054] S840. The two monitoring terminals are fault-triggered;

[0055] S850. The two monitoring terminals send the trigger flag to the server and send the instruction to return the waveform polarity;

[0056] S860. The monitoring terminal determines the polarity of the waveform according to the voltage traveling wave and returns the polarity flag bit to the server. The positive polarity is 0 and the negative polarity is 1.

[0057] S870. The terminal monitors the voltage traveling wave waveform sequence, finds the point with the largest absolute value, and records the serial number of this point as index. Then, b sampling points are pushed forward and backward in turn, and it is judged whether its sign is the same as that of the point at index. If so, the rule is satisfied, and the polarity of the sampling point with the serial number index is the polarity of this waveform. If not, find the point with the second largest absolute value of the sampling point and perform the above determination again until the rule is satisfied;

[0058] S880. Sort all the monitoring terminals on the same line according to the electricity quantity, and let the two monitoring terminals with the best electricity quantity transmit the voltage traveling wave back. Determine the polarity of this voltage traveling wave. If they are of the same polarity, discard them and re-select the two monitoring terminals with the second best electricity quantity to repeat the judgment. If they are of different polarities, upload the waveform;

[0059] S890. If there is no traveling wave voltage transmitted back by the terminal, use the traveling wave current as the judgment basis, and the judgment method is the same as that of the traveling wave voltage;

[0060] If there is no data for both the traveling wave voltage and the traveling wave current, discard the terminal without data and re-select other terminals on the line.

[0061] The beneficial effects of the above four steps are as follows:

[0062] The monitoring terminal parameters can be dynamically adjusted according to different lines, and the line faults can be monitored personalized according to the different environments of the lines themselves, with higher pertinence and reliability;

[0063] Multichannel acquisition is adopted, and the waveforms collected are screened on the server, greatly reducing the amount of data that the monitoring terminal needs to upload, and the operation reliability of the monitoring terminal can be improved as a whole. Description of the Drawings

[0064] Figure 1 It is the wiring diagram of the non-contact current sensor and the conditioning circuit described in the present invention;

[0065] Figure 2 It is the layout diagram of the metal sheets in the capacitive voltage division sensor described in the present invention;

[0066] Figure 3 It is the schematic diagram of the capacitive voltage division sensor described in the present invention;

[0067] Figure 4 It is the schematic diagram of the conditioning circuit described in the present invention;

[0068] In the drawings, the list of components represented by each reference numeral is as follows:

[0069] 1. Non-contact current sensor, 110. Housing, 120. Upper inner core, 130. Lower inner core, 140. Enameled wire, 150. External tap, 160. First integrating resistor, 170. Second integrating resistor, 2. Capacitive voltage divider sensor, 210. Metal sheet, 3. Conditioning circuit, 310. First-stage amplifier circuit, 320. Second-stage amplifier circuit, 330. Filtering circuit, 340. Phase-shifting circuit, 350. Gain adjustment circuit. Detailed implementation mode

[0070] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0071] Embodiment 1

[0072] The non-contact current sensor 1 needs to measure fault traveling wave current (in the range of several amperes to thousands of amperes), abnormal discharge traveling wave current (in the range of several milliamperes to several amperes), and power frequency current (in the range of amperes);

[0073] Therefore, a non-contact current sensor 1 with a specific structure is designed, as Figure 1 shown, and its specific structure is as follows:

[0074] The non-contact current sensor 1 includes: housing 110, end caps, upper inner core 120, lower inner core 130, enameled wire 140, first integrating resistor 160, and second integrating resistor 170;

[0075] The housing 110 is a columnar shape with a hollow interior and open ends at both ends. The material of the housing 110 is aluminum. The housing 110 is vertically installed on the line tower, and the housing 110 can shield the interference signals of the external electromagnetic field;

[0076] Two end caps respectively seal the ports at both ends of the housing 110. The two end caps are made of a resin material with high strength and strong corrosion resistance to ensure that the magnetic field of the effective signal can pass through the interior for subsequent measurement;

[0077] The upper inner core 120 is vertically arranged inside the housing 110. Since the abnormal discharge current waveform needs to be measured, the amplitude of the discharge current waveform is usually extremely low, at the milliamperes level. Therefore, the upper inner core 120 is made of a high magnetic permeability material to ensure the effective acquisition of the discharge current waveform; the lower inner core 130 is vertically arranged inside the housing 110. Since the fault current needs to be measured, the amplitude of the fault current is usually relatively high. To prevent the coil from experiencing magnetic saturation and resulting in distorted output waveforms, the lower inner core 130 is made of a low magnetic permeability material;

[0078] The enameled wire 140 is wound around the upper inner core 120 and the lower inner core 130, and an external tap 150 is provided at the transition of the enameled wire 140 between the upper inner core 120 and the lower inner core 130;

[0079] The tap where the enameled wire 140 winds out of the upper inner core 120, the tap where the enameled wire 140 winds out of the lower inner core 130, and the external tap 150 of the enameled wire 140 at the transition between the upper inner core 120 and the lower inner core 130 are respectively connected to the conditioning circuit 160;

[0080] One end of the first integrating resistor 160 is electrically connected to the external tap 150, and the other end of the first integrating resistor 160 is electrically connected to the tap where the enameled wire 140 winds out of the lower inner core 130;

[0081] One end of the second integrating resistor 170 is electrically connected to the tap where the enameled wire 140 winds out of the upper inner core 120, and the other end of the second integrating resistor 170 is electrically connected to the common end of the tap where the enameled wire 140 winds out of the lower inner core 130 and the first integrating resistor 160;

[0082] The combination of the external tap 150 of the enameled wire 140 at the transition between the upper inner core 120 and the lower inner core 130, the tap where the enameled wire 140 winds out of the lower inner core 130, and the first integrating resistor 160 is used to measure the fault traveling - wave current and the power - frequency current;

[0083] The combination of the tap where the enameled wire 140 winds out of the upper inner core 120, the tap where the enameled wire 140 winds out of the lower inner core 130, and the second integrating resistor 170 is used to measure the abnormal discharge traveling - wave current.

[0084] Embodiment 2

[0085] This embodiment is a further optimization based on Embodiment 1, and the details are as follows:

[0086] The high - permeability material is preferably permalloy; the low - permeability material is preferably non - magnetic ABS.

[0087] Embodiment 3

[0088] This embodiment is a further optimization based on Embodiment 1 or 2, and the details are as follows:

[0089] The number of turns of the enameled wire 140 wound on the upper inner core 120 is less than the number of turns of the enameled wire 140 wound on the lower inner core 130;

[0090] Under normal circumstances, the number of turns of the enameled wire 140 wound on the upper inner core 120 is 20 - 60 turns, and the number of turns of the enameled wire 140 wound on the lower inner core 130 is 300 - 500 turns.

[0091] The resistance value of the first integrating resistor 160 is less than the resistance value of the second integrating resistor 170;

[0092] Under normal circumstances, the resistance value of the first integrating resistor 160 is 30 to 70 Ω, and the resistance value of the second integrating resistor 170 is 800 to 1200 Ω to achieve the simultaneous measurement of the fault current, abnormal discharge current, and power frequency current.

[0093] Embodiment 4

[0094] As Figures 1 to 4 shown, a fault monitoring device includes a host computer, a server, and monitoring terminals; a plurality of monitoring terminals are respectively connected to the server, and the server is communicatively connected to the host computer;

[0095] The monitoring terminal includes a non-contact current sensor 1, a capacitive voltage divider sensor 2, and a conditioning circuit 3; the non-contact current sensor 1 is vertically installed on the line tower, and the conditioning circuit 3 is electrically connected to the tap of the lower inner core 130 wound by the enameled wire 140, the tap of the upper inner core 120 wound by the enameled wire 140, and the external tap 150 respectively; the capacitive voltage divider sensor 2 is arranged below the energized three-phase conductors to be measured; the capacitive voltage divider sensor 2 and the conditioning circuit 3 are respectively connected to the server.

[0096] Embodiment 5

[0097] As Figure 4 shown, this embodiment is a further optimization based on Embodiment 4, which is specifically as follows:

[0098] The conditioning circuit 3 includes a first-stage amplifier circuit 310, a second-stage amplifier circuit 320, a filter circuit 330, a phase-shifting circuit 340, and a gain adjustment circuit 350;

[0099] First-stage amplifier circuit 310: The output signal of the current sensor is used as the INPUT input signal of this circuit, and after amplification, it is OUTPUT;

[0100] Filter circuit 330: The OUTPUT output signal of the first-stage amplifier circuit 310 is used as the INPUT input signal of this circuit, and after filtering, the inherent noise waveform of the line is filtered out and output;

[0101] Phase-shifting circuit 340: The OUTPUT output signal of the filter circuit 330 is used as the INPUT input signal of this circuit, and after phase-shifting, it is OUTPUT;

[0102] Second-stage amplifier circuit 320: The OUTPUT output signal of the first-stage amplifier circuit 310 is used as the INPUT input signal of this circuit, and after being amplified again, it is OUTPUT;

[0103] Gain adjustment circuit 350:

[0104] Take the OUTPUT signal of the phase-shifting circuit 340 as the INPUT1 input signal 1 of this circuit, take the OUTPUT signal of the secondary amplification circuit 320 as the INPUT2 input signal 2 of this circuit, and restore the gain multiple of the acquired signal.

[0105] The specific circuit connection is as follows: One path of the output of the primary amplification circuit 310 is sequentially connected to the filtering circuit 330, the phase-shifting circuit 340, and the gain adjustment circuit 350, and the other path of the output of the primary amplification circuit 310 is sequentially connected to the secondary amplification circuit 320 and the gain adjustment circuit 350.

[0106] Embodiment 6

[0107] As Figure 2 、 Figure 3 shown, this embodiment is a further optimization based on Embodiment 4 or 5, and the details are as follows:

[0108] The capacitive voltage-dividing sensor 2 includes: a metal sheet 210, a sampling capacitor C M and a damping resistor R 1 ;

[0109] The metal sheet 210 is arranged below the energized three-phase conductors to be measured. A coupling capacitor C 1 will be formed between the energized three-phase conductors to be measured and the metal sheet 210. The metal sheet 210 forms a capacitance to ground C 2 , C 1 and C 2 will form a capacitive voltage-dividing capacitor. A sampling capacitor C 1 and a damping resistor R M are connected in parallel at both ends of C 1 to realize voltage measurement. The sampled voltage u m and the line voltage u satisfy the following relational expression to realize the measurement of the voltage signal;

[0110]

[0111] Embodiment 7

[0112] Due to the complex line environment, there are many interference waveforms on the line. These interference waveforms have the characteristic of stable waveform morphology. If these interference waveforms are not processed, it will cause the monitoring terminal to be mis-triggered, upload a lot of invalid signals, resulting in a large increase in the data volume and an increase in the power consumption of the monitoring terminal. Therefore, the present invention designs a fault monitoring method to eliminate the inherent interference waveforms of the line and ensure the low-power operation of the monitoring terminal;

[0113] It specifically includes the following steps:

[0114] S100. The monitoring terminal regularly collects traveling - wave current and traveling - wave voltage signals at non - fault moments of the line, temporarily stores them, and records the traveling - wave current waveform sequence xbdl 1 =[x 1 ,x 2 ,x 3 ...x n , and the traveling - wave voltage waveform sequence xbdy 1 =[y 1 ,y 2 ,y 3 ...y n ;

[0115] S200. The monitoring terminal operates normally. When a trigger is detected (the monitoring terminal fails and triggers), it collects the traveling - wave current and traveling - wave voltage at the moment of the line fault trigger, and stores them, recording the traveling - wave current waveform sequence xbdl 2 =[z 1 ,z 2 ,z 3 ...z n , and the traveling - wave voltage waveform sequence xbdy 2 =[w 1 ,w 2 ,w 3 ...w n ;

[0116] S300. Calculate the current correlation coefficient ρ dl1 and the voltage correlation coefficient ρ dy1 ;

[0117] S400. Re - organize the waveform sequences obtained at the fault moment by convolution to obtain a new traveling - wave current waveform sequence and a traveling - wave voltage waveform sequence and according to the re - organized waveform sequences

[0118]

[0119] the non - fault moment waveform sequences xbdl 1 =[x 1 ,x 2 ,x 3 ...x n and xbdy 1 =[y 1 ,y 2 ,y 3 ...y n , calculate the current correlation coefficient ρ dl2 and the voltage correlation coefficient ρ dy2 ;

[0120] Repeat step S400 for S500 for n times to obtain a waveform sequence of the reconstructed traveling wave current at the fault moment Sequence of reconstructed traveling wave voltage waveform groups

[0121] And each time a cycle is completed, calculate the correlation coefficient ρ between the reconstructed waveform sequence and the waveform sequence at the non-fault moment dln and ρ dyn , and respectively take the value with the largest absolute value of the correlation coefficient as the judgment reference data, denoted as max∣ρ dln ∣, max∣ρ dyn ∣;

[0122] S600. Take the maximum correlation coefficient of the traveling wave voltage as the judgment basis,

[0123] Judge whether max∣ρ dyn ∣≥k, 0≤k≤1;

[0124] If this condition is met, discard the waveforms at the fault moment. If not, enter S800;

[0125] If there is a situation where the traveling wave voltage is not collected at the fault moment or the non-fault moment, use the traveling wave current as the judgment basis,

[0126] Judge whether max∣ρ dln ∣≥k, 0≤k≤1;

[0127] If this condition is met, discard the waveforms at the fault moment. If not, enter S700;

[0128] S700. Amplify, filter, phase-shift, and adjust the gain of the traveling wave current at the fault trigger moment, and transmit it to the server;

[0129] S800. Judge the polarities of the traveling wave voltages returned by two monitoring terminals among all the monitoring terminals on the same line. If they are of the same polarity, discard them and re-select two monitoring terminals for re-judgment. If they are of different polarities, upload the waveforms to the host computer;

[0130] If the terminal does not return the traveling wave voltage, use the traveling wave current as the judgment basis, and the judgment method is the same as that for the traveling wave voltage;

[0131] If there is no data for both the traveling wave voltage and the traveling wave current, discard the terminal without data and re-select other terminals on the line.

[0132] Embodiment 8

[0133] This embodiment is a further optimization based on Embodiment 7, and the specific content is as follows:

[0134] In S200, the monitoring terminal failure trigger adopts the power frequency voltage change threshold trigger, the power frequency current change threshold trigger, or the traveling wave voltage threshold trigger.

[0135] Power frequency voltage change trigger threshold

[0136] Set the normal operating voltage U of the measured energized three-phase wire. According to the requirements of the power grid for the operating voltage quality of the line, the sum of the absolute values of the positive and negative voltage deviations does not exceed 10% of the rated value. Then, the change threshold of this part is taken as ΔU 1 = 0.1U;

[0137] Since the output of the capacitive voltage divider sensor 2 is related to the distance, and the installation point of the monitoring terminal and the position of the upper wire will not be absolutely symmetrical, the voltage change threshold caused by the installation point asymmetry should be considered and can be calculated according to the following formula;

[0138] Calculate the voltage change threshold ΔU 2 ;

[0139]

[0140] In the formula: d A , d B , d C are the distances between the installation point of the capacitive voltage divider sensor 2 and the measured energized three-phase wires respectively, is the average value of d A , d B , d C , that is

[0141] To minimize the false triggering of the monitoring terminal and achieve the purpose of reducing power consumption and data transmission volume, a reliability coefficient μ of the threshold can be set. The value of μ is 1 to 1.2 and can be adjusted according to the operating conditions. The initial value is 1. Then, the power frequency voltage change threshold:

[0142] Δu = μ * (ΔU 1 + ΔU 2 );

[0143] Power frequency current change trigger threshold

[0144] Considering the measurement error of the non-contact current sensor, according to the actual error value p% of the designed non-contact current sensor (the measurement error range of the sensor given in the present invention is 10%), the trigger threshold coefficient Δν 1 = 1 + p%;

[0145] The output of the non-contact current sensor is related to the installation point of the monitoring terminal. The change current caused by the installation point asymmetry should be considered, and the coefficient Δν caused by the installation point asymmetry 2 ;

[0146]

[0147] where: d A , d B , d C are the distances between the installation points of the non-contact current sensor (1) and the energized three-phase conductors to be measured, respectively is the average value of d A , d B , d C , that is

[0148] Since the non-contact current sensor is installed on the tower and collects the three-phase synthetic voltage, the zero-sequence current in the power grid relay protection can be used as the reference quantity, and the trigger threshold is set. The zero-sequence current can be queried from the relay protection, and the maximum value is taken. Let the query value be Δi l , then the trigger threshold setting value for the power frequency current change is: Δi = Δν 1 *Δν 2 *Δi l ;

[0149] Traveling wave voltage trigger threshold

[0150] Set the amplitude of the inherent interference traveling wave voltage waveform collected by the traveling wave voltage acquisition circuit to Then the trigger threshold for the traveling wave voltage change is set to

[0151] Example 9

[0152] This example is a further optimization based on Example 7, and the details are as follows:

[0153] The method for calculating the current correlation coefficient in S300 is:

[0154]

[0155] The method for calculating the voltage correlation coefficient in S300 is:

[0156]

[0157] Example 10

[0158] This example is a further optimization based on Example 7, and the details are as follows:

[0159] The method for inner scroll recombination in S400 is:

[0160] The last sampling point of the waveform sequence is moved to the first sampling point of the waveform sequence, and the remaining sampling points are all shifted backward by one position. If the traveling wave current waveform after the fault is recombined according to this rule, the new waveform sequence is After the traveling wave voltage is reorganized according to this rule, the new waveform sequence is

[0161] Example 11

[0162] This example is a further optimization based on Example 7 or 10, and the details are as follows:

[0163] The calculation method of the current correlation coefficient ρ dl2 and the voltage correlation coefficient ρ dy2 after reorganizing the waveform in S400 is:

[0164]

[0165]

[0166] Example 12

[0167] This example is a further optimization based on Example 7, and the details are as follows:

[0168] Since the action range of the transmission line fault monitoring terminal only targets the line section between two installation points, there is no need to perform fault diagnosis on the lines outside the monitored section. Therefore, the present invention further determines the effectiveness of the collected data to reduce the data volume.

[0169] Assume that the line installation points are in the order from the small-numbered station to the large-numbered station. The voltage traveling wave waveform sequence collected by the 1# monitoring terminal is u xb1 = [a 1 , a 2 , a 3 ... a n , and the traveling wave voltage waveform sequence collected by the 2# monitoring terminal is u xb2 = [b 1 , b 2 , b 3 ... b n , and so on. Since the monitoring terminal needs to operate with low power consumption, and the power consumption of the data transmission module of the monitoring terminal is relatively high, each monitoring terminal will upload signals in the following manner after collecting the trigger waveform.

[0170] S800 is specifically as follows:

[0171] S810: All monitoring terminals upload the terminal operating condition information to the server;

[0172] S820: The server sorts the monitoring terminals on the same line from high to low according to the power consumption based on the operating condition information uploaded by the monitoring terminals;

[0173] S830. The server selects two monitoring terminals with the highest power levels to send a to-be-triggered instruction. The monitoring terminal receives the instruction and awaits triggering.

[0174] S840. The two monitoring terminals are triggered due to a fault.

[0175] S850. The two monitoring terminals send a trigger flag to the server and send a backhaul waveform polarity instruction.

[0176] S860. The monitoring terminal determines the waveform polarity based on the voltage traveling wave and sends a polarity flag bit back to the server. The positive polarity is 0 and the negative polarity is 1.

[0177] S870. The terminal monitors the voltage traveling wave waveform sequence u xb1 =[a 1 ,a 2 ,a 3 ...a n . Find the point with the largest absolute value. The serial number of this point is denoted as index. To exclude some spike-type interference items in the line, b sampling points are pushed forward and backward in sequence (the value is taken according to different sampling rates. In this embodiment, it is recommended to take points with a length of 5 us as the judgment points). Determine whether its sign is the same as that of the point at index. If so, the rule is satisfied, and the polarity of the sampling point with the serial number index is the waveform polarity. If not, find the point with the second largest absolute value of the sampling point and perform the above determination again until the rule is satisfied.

[0178] S880. Sort all the monitoring terminals on the same line according to their power levels, and let the two monitoring terminals with the best power levels backhaul the voltage traveling wave. Determine the polarity of this voltage traveling wave. If they have the same polarity, discard them and re-select the two monitoring terminals with the next best power levels to repeat the judgment. If they have different polarities, upload the waveform.

[0179] Among them, the same polarity means that the fault point is not within the monitoring sections of these two terminals, and the opposite polarity means that the fault point is located within the monitoring section.

[0180] S890. If the terminal does not backhaul the traveling wave voltage, use the traveling wave current as the judgment basis, and the judgment method is the same as that for the traveling wave voltage.

[0181] If there is no data for both the traveling wave voltage and the traveling wave current, discard the terminals with no data and re-select other terminals on the line.

[0182] Embodiment 13

[0183] This embodiment is a further optimization based on Embodiment 12, which is specifically as follows:

[0184] To facilitate the understanding of the content of S870, an example is given:

[0185] The terminal monitors the voltage traveling wave waveform sequence u xb1 = [a 1 , a 2 , a 3 ... a n . The corresponding serial numbers of these points are [1, 2, 3,..., n]. Assume that the serial number of the point with the largest absolute value of the sampled point value is the 100th, and the sign is negative.

[0186] Then determine whether the signs of the values of the sampled points with serial numbers [100 - b, 100 - b + 1, 100 - b + 2,..., 100, 100 + 1, 100 + 2,..., 100 + b] are all negative. If so, the polarity of the voltage traveling wave waveform sequence is negative. If not, find the point with the second largest absolute value of the sampled point value and perform the above operation again until a point that meets the requirements is found to determine the waveform polarity.

[0187] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. Fault monitoring method, characterized in that, the fault monitoring device used includes: a host computer, a server communicatively connected to the host computer, and multiple monitoring terminals connected to the server; the monitoring terminal includes: a capacitive voltage divider sensor (2), a conditioning circuit (3) and a non-contact current sensor (1), the non-contact current sensor (1) is vertically installed on the line tower, and the capacitive voltage divider sensor (2) is arranged below the three energized phase conductors to be measured; the non-contact current sensor (1) includes: a housing (110), which is a columnar shape with a hollow interior and open ends at both ends, made of aluminum and longitudinally distributed; two end caps, which respectively seal the ports at both ends of the housing (110), made of resin; an iron core, which is vertically arranged inside the housing (110) and is composed of an upper inner core (120) and a lower inner core (130), and the upper inner core (120) is made of a high magnetic permeability material, and the lower inner core (130) is made of a low magnetic permeability material; an enameled wire (140), which is wound around the upper inner core (120) and the lower inner core (130), and an external tap (150) is provided at the transition between the upper inner core (120) and the lower inner core (130); a first integrating resistor (160), one end of which is electrically connected to the external tap (150), and the other end is electrically connected to the tap where the enameled wire (140) winds out of the lower inner core (130); a second integrating resistor (170), one end of which is electrically connected to the tap where the enameled wire (140) winds out of the upper inner core (120), and the other end is electrically connected to the common end of the tap where the enameled wire (140) winds out of the lower inner core (130) and the first integrating resistor (160); the conditioning circuit (3) is respectively electrically connected to the tap where the enameled wire (140) winds out of the lower inner core (130), the tap where the enameled wire (140) winds out of the upper inner core (120), and the external tap (150); The fault monitoring steps are as follows: S100. The monitoring terminal regularly collects the traveling-wave current and traveling-wave voltage at non-fault moments of the line, temporarily stores them, and obtains the traveling-wave current waveform sequence xbdl at non-fault moments 1 and the traveling-wave voltage waveform sequence xbdy 1 ; S200. The monitoring terminal fails and triggers to collect the traveling wave current and traveling wave voltage at the moment when the line fault is triggered, and stores them to obtain the traveling wave current waveform sequence xbdl at the fault moment 2 and the traveling wave voltage waveform sequence xbdy 2 ; S300. Calculate the correlation coefficient between the waveform at the fault moment and the temporarily stored waveform at the non-fault moment to obtain the current correlation coefficient ρ dl1 and the voltage correlation coefficient ρ dy1 ; S400. Recombine the waveform sequence stored at the fault moment by convolution to obtain a new traveling wave current waveform sequence xbdl cz1 , a traveling wave voltage waveform sequence xbdy cz1 , and calculate the current correlation coefficient ρ dl2 and the voltage correlation coefficient ρ dy2 ; Repeat step S400 for n times to obtain the waveform sequence xbdl of the reconstructed traveling wave current at the fault moment czn and the waveform group sequence xbdy of the reconstructed traveling wave voltage czn . And each time it is repeated, calculate the correlation coefficient ρ between the reconstructed waveform sequence and the waveform sequence at the non-fault moment dln and ρ dyn . Respectively, take the value with the largest absolute value of the correlation coefficient as the judgment reference data, denoted as max∣ρ dln ∣, max∣ρ dyn ∣; S600. Take the maximum correlation coefficient of the traveling wave voltage as the judgment basis; Determine max|ρ dyn |≥k, 0 ≤ k ≤ 1; If this condition is met, the waveforms at the fault moment are all discarded. If not, enter S800; If there is a situation where the traveling wave voltage is not collected at the fault moment or non-fault moment, the traveling wave current is used as the judgment basis: Determine max|ρ dln |≥k, 0≤k≤1; If this condition is met, the waveforms at the fault moment are all discarded. If not, enter S700; S700. Amplify, filter, phase-shift, and adjust the gain of the traveling wave current at the fault trigger moment, and transmit it to the server; S800. Judge the polarities of the traveling wave voltages returned by two monitoring terminals among all the monitoring terminals on the same line. If they are of the same polarity, discard them and re-select two monitoring terminals to re-judge. If they are of different polarities, upload the waveforms to the host computer; If no traveling wave voltage is returned by the terminal, the traveling wave current is used as the judgment basis, and the judgment method is the same as that of the traveling wave voltage judgment method; If there is no data for both the traveling wave voltage and the traveling wave current, the terminal without data is discarded, and other terminals on the line are re-selected.

2. The fault monitoring method according to claim 1, characterized in that: the high magnetic permeability material is permalloy; the low magnetic permeability material is ABS.

3. The fault monitoring method according to claim 1 or 2, characterized in that: The number of turns of the enameled wire (140) wound around the upper inner core (120) is 20 to 60 turns, and the number of turns of the enameled wire (140) wound around the lower inner core (130) is 300 to 500 turns; the resistance value of the first integrating resistor (160) is 30 to 70 Ω, and the resistance value of the second integrating resistor (170) is 800 to 1200 Ω.

4. The fault monitoring method according to claim 1, characterized in that: The conditioning circuit (3) includes a first-stage amplifying circuit (310), a second-stage amplifying circuit (320), a filtering circuit (330), a phase-shifting circuit (340) and a gain adjustment circuit (350). One output of the first-stage amplifying circuit (310) is sequentially connected to the filtering circuit (330), the phase-shifting circuit (340) and the gain adjustment circuit (350), and the other output of the first-stage amplifying circuit (310) is sequentially connected to the second-stage amplifying circuit (320) and the gain adjustment circuit (350).

5. The fault monitoring method according to claim 1 or 4, characterized in that: The capacitive voltage-dividing sensor (2) includes: A metal sheet (210) is arranged below the circuit and forms a coupling capacitor C with the circuit 1 , and forms a capacitance C to the ground with the ground 2 ; Sampling capacitor C M1 , after being connected in series with damping resistor R, is connected in parallel across coupling capacitor C 1 at both ends.

6. The fault monitoring method according to claim 1, characterized in that: In the S200, the monitoring terminal fault trigger adopts a power frequency voltage change threshold trigger, a power frequency current change threshold trigger, or a traveling wave voltage threshold trigger.

7. The fault monitoring method according to claim 1, characterized in that: The method of inner roll recombination in the S400 is: The last sampling point of the waveform sequence is moved to the first sampling point of the waveform sequence, and the rest of the sampling points are all shifted backward by one position.

8. The fault monitoring method according to claim 1 or 6 or 7, characterized in that: The S800 is specifically: S810: All monitoring terminals upload the terminal operation condition information to the server; S820: The server sorts the monitoring terminals on the same line according to the power consumption from high to low according to the operation condition information uploaded by the monitoring terminals; S830: The server selects the two monitoring terminals with the highest power consumption to send a pending trigger instruction, and the monitoring terminals receive the instruction and wait to be triggered; S840: The two monitoring terminals are fault-triggered; S850: The two monitoring terminals send a trigger flag to the server and send a waveform polarity instruction for feedback; S860: The monitoring terminal determines the waveform polarity according to the voltage traveling wave and sends a polarity flag bit back to the server. The positive polarity is 0 and the negative polarity is 1; S870: When the monitoring terminal detects the voltage traveling wave waveform sequence, find the point with the largest absolute value. The serial number of this point is recorded as index, and b sampling points are pushed forward and backward in turn to judge whether its sign is the same as that of the point of index. If so, the rule is satisfied, and the polarity of the sampling point with the serial number of index is the waveform polarity. If not, find the point with the second largest absolute value of the sampling point and perform the above determination again until the rule is satisfied; S880: Sort all the monitoring terminals on the same line according to the power consumption, and let the two monitoring terminals with the best power consumption send back the voltage traveling wave to determine the polarity of the voltage traveling wave. If they are of the same polarity, discard them and re-select the two monitoring terminals with the second best power consumption to repeat the judgment. If they are of different polarities, upload the waveform. S890. If there is no traveling wave voltage feedback from the terminal, the traveling wave current shall be used as the judgment basis, and the judgment method is the same as that for traveling wave voltage; If there is no data for both the traveling wave voltage and the traveling wave current, the terminal without data shall be discarded and other terminals on the line shall be reselected.

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