CN106066444A - Ground fault detection device and method based on capacitance partial pressure and big data analysis - Google Patents
Ground fault detection device and method based on capacitance partial pressure and big data analysis Download PDFInfo
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Abstract
The invention discloses a kind of ground fault detection device and method based on capacitance partial pressure and big data analysis, including sample processing unit and sampling unit, sampling unit includes the voltage sample module for gathering distribution line voltage-to-ground.The distribution line ground fault detection device of the present invention and monitoring method can be sampled the voltage-to-ground of supply line by using the voltage acquisition module with capacitance partial pressure, after tested distribution line generation earth fault, metastable sampled voltage can be obtained by the capacitance partial pressure acquisition module that capacitance resistance is constituted, this fault monitoring device and monitoring method relax the requirement to measurement instantaneity for the hardware, belong to steady state measurement technology after supply line's ground connection, line-to-ground fault can be identified quickly and accurately；Carrying out big data analysis by the data that break down supply line in history, each branch of supply line fault rate is asked in Dynamic Programming, in conjunction with actual track alarm condition, provides malfunction elimination path optimizing decision.
Description
Technical Field
The invention relates to the technical field of power line fault monitoring, in particular to a single-phase or multi-phase ground fault monitoring device and a monitoring method for a 10KV overhead line and a cable line based on capacitance partial pressure and big data analysis.
Background
In a power grid distribution line system, a 10KV system is a medium-voltage power grid, the medium-voltage power grid in China mostly adopts a neutral point non-effective grounding system, when a single-phase grounding fault occurs, the voltage of a neutral point is increased to be a fault phase voltage, the line voltage among A, B, C three phases is basically kept unchanged, and the fault current is small, so that the power grid can run for about 2 hours, and the power supply reliability is ensured. However, after a single-phase earth fault occurs, the line needs to be cut off or the fault needs to be eliminated in time, otherwise, after the power grid operates for a period of time with faults, the fault gradually develops into an interphase short-circuit fault due to partial discharge, and great damage is brought to a power supply line.
Due to the fact that neutral point grounding modes of the 10KV power distribution network are various, the judgment of the grounding fault is difficult. In order to monitor and find out the earth fault in time, there are several main methods of the earth fault monitoring commonly used at present, such as an injection signal method, a line-to-earth capacitance discharge method, a zero sequence current judgment method, a three-phase earth-to-earth voltage comparison method, and the like. The signal injection method needs an external signal source, extra fault hidden danger is brought to a power supply system, and the frequency selection of the injected signals also influences the correctness of line selection; the circuit-to-ground capacitive discharge method is greatly influenced by an external arc suppression coil of a neutral point, so that the accuracy of fault line selection is low; the zero sequence current judgment method is limited to be used in overhead lines, and the construction of the zero sequence current by adopting a mathematical vector synthesis technology is also limited by the performance of the current hardware equipment; the three-phase ground voltage comparison method needs to measure the three-phase ground voltages and determine the grounding phase according to the voltage value sorting, but it is very inconvenient to directly measure the ground voltages in the actual distribution line. The existing 10KV power distribution network earth fault monitoring technology cannot meet the requirement of rapidly identifying the line single-phase earth fault.
Disclosure of Invention
The invention provides a device and a method for monitoring a ground fault based on capacitance voltage division and big data analysis, which can quickly and accurately identify the occurrence of the ground fault of a line and overcome the defects of low speed and low accuracy rate of ground fault detection in the prior art.
In order to solve the above problems, the present invention provides a ground fault monitoring device based on capacitance voltage division and big data analysis, which comprises a sampling processing unit and a sampling unit, the sampling unit is characterized by comprising a voltage sampling module used for collecting the voltage to ground of the distribution line, the voltage sampling module comprises an input end used for being connected with a distribution line, the input end is sequentially connected with a first diode, a second resistor and a third resistor, the third resistor is grounded, a first capacitor is connected between the input end and the first diode, one end of the first capacitor is connected with the input end, the other end of the first capacitor is grounded, the two ends of the first capacitor are further connected with a first resistor in parallel, a first leading-out end connected with the sampling processing unit is arranged between the second resistor and the third resistor, and the sampling processing unit collects sampling voltage at the first leading-out end.
The ground fault monitoring device based on the capacitance voltage division and big data analysis provided by the invention also has the following technical characteristics:
furthermore, the sampling unit also comprises a current sampling module used for collecting current information of the distribution line, the current sampling module comprises a first mutual inductor for collecting current information of the distribution line, the two ends of the first mutual inductor are connected with a fourth resistor and a fifth resistor which are connected in series, two ends of the first mutual inductance coil are also connected with a first voltage stabilizing diode in parallel, one end of the first mutual inductance coil is grounded, a second leading-out terminal connected with the sampling processing unit is arranged between the fourth resistor and the fifth resistor, the sampling processing unit collects sampling current at the second leading-out end, a third capacitor is connected between the second leading-out end and the sampling processing unit, one end of the third capacitor is connected with the second leading-out end, the other end of the third capacitor is grounded, and two ends of the third capacitor are connected with a second voltage stabilizing diode in parallel.
Furthermore, a second capacitor is connected in parallel to two ends of the third resistor.
Furthermore, the sampling processing unit is also connected with a height sensor for acquiring the height of the distribution line and a humidity sensor for acquiring the humidity of the environment near the distribution line.
Furthermore, the sampling processing unit is also connected with a communication module.
Another objective of the present invention is to provide a ground fault monitoring method based on capacitive voltage division and big data analysis, which includes the following steps:
s10: collecting sampling voltage of a single-phase line in a distribution line by using the ground fault monitoring device;
s20: comparing the collected sampling voltage of the single-phase line with a first preset voltage, and if the sampling voltage is smaller than the first preset voltage, judging that the single-phase line is in a power failure state; if the sampling voltage is greater than or equal to a first preset voltage, comparing the sampling voltage with a second preset voltage, wherein the second preset voltage is greater than the first preset voltage;
s30: if the sampling voltage is greater than or equal to a second preset voltage, the single-phase line is judged to normally work, and the third preset voltage is greater than the second preset voltage; and if the sampling voltage is less than a second preset voltage, judging that the single-phase line has a ground fault.
The ground fault monitoring method based on the capacitance voltage division and big data analysis provided by the invention also has the following technical characteristics:
further, the step S10 further includes collecting a sampling current of a single-phase line in the distribution line;
step S20 is that, if the sampling voltage is less than a first preset voltage and the sampling current is equal to zero, it is determined that the single-phase line is in a power failure state; if the sampling voltage is greater than or equal to a first preset voltage and the sampling current is not equal to zero, comparing the sampling voltage with a second preset voltage;
step S30, if the sampling voltage is greater than or equal to a second preset voltage and the sampling current is not equal to zero, comparing the sampling voltage with a third preset voltage, and if the sampling voltage is greater than the third preset voltage, determining that the single-phase line works normally; and if the sampling voltage is less than a second preset voltage and the sampling current is not equal to zero, judging that the single-phase line has a ground fault.
Further, the step S30 further includes: and if the sampling voltage is greater than a third preset voltage, correcting the sampling voltage according to the height of the single-phase line and the environmental humidity, and judging that the single-phase line works normally if the corrected sampling voltage is greater than the third preset voltage.
Further, the step S30 further includes S31: if the sampling voltage is smaller than a second preset voltage, calculating a difference value between the sampling voltage of the single-phase line and the sampling voltages of other two-phase single-phase lines and a percentage value between the difference value and the sampling voltages of other two-phase single-phase lines, and if the percentage value is larger than a first preset threshold value, judging that the single-phase line has a ground fault.
Further, the step S30 further includes the step S32: and calculating the probability of the occurrence of the primary ground fault A from each power supply branch Li by using a Bayesian formula according to the frequency of the occurrence of the ground fault of each power supply branch in the power distribution network in history, the length of each power supply branch and the total length ratio of the whole power distribution network line.
The invention has the following beneficial effects: the ground fault monitoring device and the monitoring method based on the capacitance partial pressure and big data analysis can sample the voltage to ground of a power supply line through a voltage acquisition module, judge whether the power supply line has ground fault according to the change of the sampling voltage, and obtain relatively stable sampling voltage through a voltage acquisition module consisting of capacitance resistors by arranging a grounded first capacitor; by carrying out big data analysis on historical fault data of the power supply line, dynamically planning to obtain the fault occurrence probability of each branch of the power supply line, and further providing the optimal decision of a troubleshooting path by combining the alarm condition of the actual line.
Drawings
Fig. 1 is a schematic structural diagram of a ground fault monitoring apparatus according to an embodiment of the present invention;
FIG. 2 is a circuit diagram of a ground fault monitoring device according to an embodiment of the present invention;
FIG. 3 is a flow chart of a method of ground fault monitoring according to an embodiment of the present invention;
FIG. 4 is a flow chart of a ground fault monitoring method according to another embodiment of the present invention;
fig. 5 is a flow chart of a ground fault monitoring method according to another embodiment of the invention.
Detailed Description
The invention will be described in detail hereinafter with reference to the accompanying drawings in conjunction with embodiments. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
In one embodiment of the ground fault monitoring device based on capacitive voltage division and big data analysis according to the present invention as shown in fig. 1 and fig. 2, the distribution line ground fault monitoring device includes a sampling processing unit 10 and a sampling unit 20, the sampling processing unit 10 includes a low power consumption CPU processing module, the sampling unit 20 includes a voltage sampling module 21 for collecting the voltage to ground of the distribution line, the voltage sampling module 21 includes an input end 211 for connecting with the distribution line, the input end 210 is connected with a first diode D1, a second resistor R2 and a third resistor R3 in sequence, the third resistor is connected to ground R3, a first capacitor C1 is further connected between the input end 211 and the first diode D1, one end of the first capacitor C1 is connected with the input end 211, the other end of the first capacitor C1 is connected to ground, the two ends of the first capacitor C1 are further connected in parallel with a first resistor R1, a first lead terminal connected with the sampling processing unit 10 is provided between the second resistor R2 and the third resistor R3, the sampling processing unit 10 collects the sampling voltage E at the first leading-out terminal. The distribution line ground fault monitoring device can sample the voltage to ground of a power supply line through the voltage acquisition module, judge whether the power supply line has ground fault according to the change of the sampling voltage, and by arranging the first capacitor which is grounded, after the measured distribution line has ground fault, the voltage acquisition module formed by the capacitor resistors can obtain relatively stable sampling voltage.
Specifically, as shown in fig. 2, the input end 211 of the ground fault monitoring device based on capacitance voltage division and big data analysis is directly connected to the bare conductor of a single-phase power supply line in a 10KV distribution line, the ground distributed capacitance of the single-phase power supply line is denoted as C4, because the height and ground medium of the power supply line change, C4 is a variable capacitance, and when the edge effect of the capacitor plate is neglected, the capacitance is:
wherein,0in order to have a dielectric constant in a vacuum,rthe relative dielectric constant of the medium, S is the relative area of the polar plates, and d is the distance between the polar plates, namely the distance between the power supply line and the ground. The voltage to ground of the 10KV power supply line is denoted as V, and the value of the voltage to ground V can be calibrated to 5774V according to the ground field form of the 10KV power supply line, in the case of a large R1, for example: r1 is 10M omega, the voltage at the two ends of the first capacitor C1 is denoted as Vc1, according to the capacitive impedance voltage division principle,
when the line normally works and no single-phase earth fault occurs, C1 and C4 are charged, voltage Vc1 passes through first diode D1, and is divided by second resistor R2 and third resistor R3, and a sampling voltage is output from a first leading-out terminal between second resistor R2 and third resistor R3, in this embodiment, C1 is 0.01uf, R2 is 2M Ω, R3 is 10M Ω, and a calculation formula of sampling voltage E is as follows:
E＝R3*Vc1/(R2+R3)；
when a 10KV power supply line connected with the input end 211 has a ground fault, the bare wire is directly connected with the ground, the ground distributed capacitor C4 of the single-phase power supply line disappears, that is, C4 is 0, at this time, the first capacitor C1 is grounded to directly discharge the charges, as can be known from the above formula, Vc1 is zero, and the sampling voltage E is zero, therefore, the distribution line ground fault monitoring device in the above embodiment can judge whether the power supply line has a ground fault according to the change of the sampling voltage, and can quickly and accurately identify the line ground fault.
The ground fault monitoring device based on capacitance voltage division and big data analysis in the above embodiment further has the following technical characteristics:
the sampling unit 20 further comprises a current sampling module 22 for acquiring current information of the distribution line, the current sampling module 22 comprises a first mutual inductor L1 for acquiring the current information of the distribution line, two ends of the first mutual inductor L1 are connected in series with a fourth resistor R4 and a fifth resistor R5 which are connected in series, two ends of the first mutual inductor L1 are also connected in parallel with a first voltage stabilizing diode W1, one end of the first mutual inductor L1 is grounded, a second leading-out end connected with the sampling processing unit 10 is arranged between the fourth resistor R4 and the fifth resistor R5, the sampling processing unit 10 acquires a sampling current I at the second leading-out end, a third capacitor C3 is further connected between the second leading-out terminal and the sampling processing unit 10, one end of a third capacitor C3 is connected with the second leading-out terminal, the other end of the third capacitor C3 is grounded, and two ends of the third capacitor C3 are further connected with a second voltage stabilizing diode W2 in parallel. Specifically, according to the electric power operation regulations in China, when a single-phase earth fault occurs, the electric power circuit can operate for about 2 hours, namely, current still flows in a falling line which operates with a fault. When the power supply line works normally, the voltage sampling module 21 of the sampling unit 20 can collect a normal sampling voltage E, and the current sampling module 22 of the sampling unit 20 can collect a normal sampling current I. When a ground fault occurs, the sampling voltage E becomes zero theoretically, and the sampling current I changes instantly when the ground fault occurs. After the ground fault occurs, the sampling voltage E is theoretically zero within a certain time, and the sampling current I can be kept at a certain stable value. When the power supply line with the ground fault has power failure, the sampling voltage E and the sampling current I are simultaneously zero. The distribution lines earth fault monitoring device in this embodiment samples the voltage and the current information of power supply line simultaneously, when the sampling voltage is zero and the sampling current is non-zero, just can judge that the single-phase power supply line that links to each other with input 211 has taken place single-phase earth fault in this distribution lines, and the fault determination rate of accuracy is high, and this distribution lines earth fault monitoring device has relaxed the requirement of hardware system to measuring the instantaneity, belongs to a steady state measurement technique after ground connection, and is simple and easy, and the reliability is high, and the rate of accuracy is high.
In the above embodiment, the two ends of the third resistor R3 are further connected in parallel with the second capacitor C2, which is used to maintain the voltage across the third resistor R3 stable, so that the sampling voltage E output from the first output terminal between the second resistor R2 and the third resistor R3 is kept stable, and fluctuation of the sampling voltage caused by interference in the distribution line is avoided. When the power supply line has a ground fault, the third resistor R3 and the second capacitor C2 form an RC discharge loop to discharge the second capacitor C2. The sampling processing unit 10 is also connected with a height sensor 11 for acquiring the height of the distribution line and a humidity sensor 12 for acquiring the ambient humidity near the distribution line, so that the height information of the power supply line and the ambient humidity near the distribution line can be acquired in real time, the ground distributed capacitor C4 of the power supply line can be corrected, the accuracy of the sampling voltage E is improved, and the accuracy of the ground fault judgment is improved. The sampling processing unit 10 is also connected to a communication module 13. Specifically, each single-phase power supply line of the three-phase power supply lines of the power distribution line is respectively connected with the ground fault monitoring device of the power distribution line, the ground fault monitoring device of the power distribution line on each single-phase power supply line can communicate with the ground fault monitoring devices of the power distribution lines on the other two single-phase power supply lines through the communication module 13 to obtain the sampling voltages of the other two single-phase power supply lines, and calculate the difference value between the sampling voltage of the single-phase power supply line and the sampling voltages of the other two single-phase power supply lines and the percentage value between the difference value and the sampling voltages of the other two single-phase power supply lines, so as to further ensure the accuracy of ground fault judgment, specifically, if the percentage value between the difference value between the sampling voltage of the single-phase power supply line and the sampling voltages of the, the sampling voltage of the single-phase power supply line is abnormal, so that the accuracy of the ground fault judgment is further ensured. The distribution line ground fault monitoring may also communicate with a Data Transfer Unit (DTU) through the communication module 13 to perform information transmission, and transmit sampling Data or a fault alarm signal. In addition, the distribution line ground fault monitoring can be set on different branches or different sections of the distribution line, and the distribution line ground fault monitoring at different positions can be transmitted with a background server through a Data Transmission Unit (DTU) through the communication module 13.
Another objective of the embodiments of the present invention as shown in fig. 3 to 5 is to provide a ground fault monitoring method based on capacitive voltage division and big data analysis, the method comprising the following steps:
s10: collecting sampling voltage E of a single-phase line in a distribution line by using the ground fault monitoring device;
s20: comparing the collected sampling voltage E of the single-phase line with a first preset voltage E1, and if the sampling voltage E is smaller than the first preset voltage E1, judging that the single-phase line is in a power failure state; if the sampled voltage E is greater than or equal to a first preset voltage E1, comparing the sampled voltage with a second preset voltage E2, wherein the second preset voltage E2 is greater than the first preset voltage E1;
s30: if the sampling voltage E is greater than or equal to a second preset voltage E2, comparing the sampling voltage E with a third preset voltage E3, and if the sampling voltage E is greater than the third preset voltage E3, judging that the single-phase line works normally, wherein the third preset voltage E3 is greater than the second preset voltage E2; and if the sampling voltage E is less than a second preset voltage E2, judging that the single-phase line has a ground fault.
Specifically, the first preset voltage E1, the second preset voltage E2 and the third preset voltage E3 are all threshold values set according to actual system operation parameters of the 10KV distribution line, according to theoretical calculation, when the power supply line has a power failure, the sampling voltage E is zero, but considering factors such as ground distributed capacitance, mutual inductance voltage of adjacent phase lines and the like, the actual sampling voltage may not be zero, and in order to ensure accuracy of determination of the power failure state of the power supply line, the method sets the first preset voltage E1; when a power supply line has a ground fault, theoretically calculating a sampling voltage to be zero, considering that the ground distributed capacitance of the power supply line is not absolutely zero and current still exists when the power supply line is grounded, and the actual value of the sampling voltage E is not zero at the moment, in order to ensure the accuracy of ground fault judgment, a second preset voltage E2 is set according to system parameters and statistical data in the method; when the power supply line normally works, the sampling voltage E is theoretically calculated to be a certain value, but the sampling voltage E fluctuates due to factors such as height change caused by the swing of the power supply line, environment humidity change or power grid voltage fluctuation, and the like. In the above implementation, the first preset voltage E1 has a value of 30 volts, the second preset voltage E2 has a value of 70 volts, and the third preset voltage E3 has a value of 150 volts. The distribution line ground fault monitoring method in the example can judge whether the power supply line has ground fault according to the change of the sampling voltage, and by arranging the grounded first capacitor, after the measured distribution line has ground fault, the voltage acquisition module formed by the capacitor resistors can obtain relatively stable sampling voltage. Specifically, after a single-phase ground fault occurs in the power supply system, the system power supply can still work for about 2 hours, and in the 2 hours, the ground fault can be continuously generated, namely, the voltage to ground is always zero, and in addition, the grounding is intermittent grounding, and the voltage to ground of a grounding line is not always zero. In the ground fault monitoring device, the capacitor resistor forms a ground voltage sampling circuit in the discharging process, and the discharging process is millisecond-level, so that whether a power line is grounded or not can be determined by measuring the voltage of the capacitor; even if the capacitor is intermittently grounded, the voltage at two ends of the capacitor is in a charging and discharging state, and relatively stable sampling voltage can still be obtained due to the fact that the discharging process is in the millisecond level, and the requirement of hardware on measurement instantaneity is relaxed.
The ground fault monitoring method provided by the above embodiment further includes the following steps:
step S10 also includes collecting the sampling current I of the single-phase line in the distribution line;
step S20 is that if the sampling voltage E is less than a first preset voltage E1 and the sampling current I is equal to zero, it is determined that the single-phase line is in a power failure state; if the sampling voltage E is greater than or equal to a first preset voltage E1 and the sampling current I is not equal to zero, comparing the magnitude of the sampling voltage E with a second preset voltage E2;
in the step S30, if the sampling voltage E is greater than or equal to a second preset voltage E2 and the sampling current I is not equal to zero, comparing the sampling voltage E with a third preset voltage E3, and if the sampling voltage E is greater than the third preset voltage E3, determining that the single-phase line works normally; and if the sampling voltage E is less than a second preset voltage E2 and the sampling current I is not equal to zero, determining that the single-phase line has a ground fault.
Specifically, according to the electric power operation regulations in China, when a single-phase earth fault occurs, the electric power circuit can operate for about 2 hours, namely, current still flows in a falling line which operates with a fault. The distribution line ground fault monitoring method in the embodiment simultaneously samples the voltage and current information of the power supply line, when the sampling voltage is greater than or equal to a first preset voltage and less than a second preset voltage, and the sampling current is not zero, the single-phase ground fault of the single-phase power supply line can be judged, the fault judgment accuracy is high, the distribution line ground fault monitoring device relaxes the requirement of a hardware system on measurement instantaneity, and the distribution line ground fault monitoring device belongs to a steady-state measurement technology after grounding, is simple and easy to implement, high in reliability and high in accuracy.
Further, in the above embodiment, the step S30 further includes: and if the sampling voltage E is greater than a third preset voltage E3, correcting the sampling voltage E according to the height H and the environmental humidity M of the single-phase line, and determining that the single-phase line works normally if the corrected sampling voltage E is greater than the third preset voltage E3. For example, when the height H is greater than 15m, the sampling voltage is verified; when the environmental humidity M is greater than 80%, verifying the sampling voltage; in addition, if the power supply line samples the insulated wire, the voltages to ground of the bare wire and the insulated wire can be measured adaptively in the process of comparing the sampling voltage E with the third preset voltage E3 according to the difference between the voltages to ground of the bare wire and the insulated wire which are compared in advance, and the voltages to ground of the bare wire and the insulated wire can be calibrated to be in an ideal state.
Further, the step S30 further includes S31: if the sampling voltage E is smaller than a second preset voltage E2, calculating the difference value between the sampling voltage E of the single-phase line and the sampling voltages E of other two-phase single-phase lines and the percentage value between the difference value and the sampling voltages of other two-phase single-phase lines, and if the percentage value is larger than a first preset threshold value, judging that the single-phase line has the ground fault, thereby further ensuring the accuracy of ground fault judgment. Specifically, the first preset threshold may be determined according to system parameters or statistical data, for example, the first preset threshold is 10%, 15%, or 20% of the value of the sampled voltage E when the power supply line is operating normally, so as to avoid erroneous determination, and eliminate the influence of environmental factors and power grid fluctuations on the sampled voltage.
Further, the step S30 further includes the step S32: and calculating the probability of the occurrence of the primary ground fault A from each power supply branch Li by using a Bayesian formula according to the frequency of the occurrence of the ground fault of each power supply branch in the power distribution network in history, the length of each power supply branch and the total length ratio of the whole power distribution network line. Specifically, the background system gives the fault probabilities of different alarm paths according to the historical fault frequencies of different lines and by combining with the position indication of the actual alarm signal, for example: the probability of the No. 1 line failing is 16%, and the probability of the No. 2 line failing is 7%, so that maintenance personnel can conveniently and quickly locate the failed line and position.
The fault statistics of a power supply line managed by a certain power supply station for a plurality of years is as follows: 1, the fault probability of the line is P1, and the length of the line is L1 (unit is kilometer); line 2, the probability of line fault is P2, and the length of line is L2 (unit is kilometer); h. -; line N, with a line fault probability of PN and a line length of LN (in kilometers). And (3) carrying out probability analysis by using a Bayesian formula, wherein the probability of the occurrence of the primary ground fault A from the line Li (i is more than or equal to 1 and less than or equal to N) is as follows:
the Bayesian formula is used for predicting the faults, and when fault alarm occurs, fault troubleshooting can be carried out according to an actual alarm path and the predicted fault probability of the line, so that the fault removal efficiency is improved. Therefore, the earth fault monitoring method carries out big data analysis by adopting statistical data of faults occurring in the distribution line within a plurality of years by adopting a capacitance voltage division principle, effectively solves the problem of single-phase earth fault alarm, and has timely earth fault alarm and high accuracy.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A ground fault monitoring device based on capacitance voltage division and big data analysis comprises a sampling processing unit and a sampling unit, the sampling unit is characterized by comprising a voltage sampling module used for collecting the voltage to ground of the distribution line, the voltage sampling module comprises an input end used for being connected with a distribution line, the input end is sequentially connected with a first diode, a second resistor and a third resistor, the third resistor is grounded, a first capacitor is connected between the input end and the first diode, one end of the first capacitor is connected with the input end, the other end of the first capacitor is grounded, the two ends of the first capacitor are further connected with a first resistor in parallel, a first leading-out end connected with the sampling processing unit is arranged between the second resistor and the third resistor, and the sampling processing unit collects sampling voltage at the first leading-out end.
2. The ground fault monitoring device of claim 1, wherein the sampling unit further comprises a current sampling module for collecting current information of a distribution line, the current sampling module comprises a first mutual inductor for collecting current information of the distribution line, a fourth resistor and a fifth resistor which are connected in series with each other are connected in series with two ends of the first mutual inductor, a first voltage stabilizing diode is further connected in parallel with two ends of the first mutual inductor, one end of the first mutual inductor is grounded, a second leading-out terminal connected with the sampling processing unit is arranged between the fourth resistor and the fifth resistor, the sampling processing unit collects sampling current at the second leading-out terminal, a third capacitor is further connected between the second leading-out terminal and the sampling processing unit, and one end of the third capacitor is connected with the second leading-out terminal, the other end of the third capacitor is grounded, and two ends of the third capacitor are also connected with a second voltage stabilizing diode in parallel.
3. The ground fault monitoring device according to claim 1 or 2, wherein a second capacitor is further connected in parallel across the third resistor.
4. The ground fault monitoring device of claim 1 or 2, characterized in that a height sensor for acquiring the height of the distribution line and a humidity sensor for acquiring the humidity of the environment near the distribution line are further connected to the sampling processing unit.
5. The ground fault monitoring device according to claim 1 or 2, wherein the sampling processing unit is further connected with a communication module.
6. A ground fault monitoring method based on capacitance voltage division and big data analysis is characterized by comprising the following steps:
s10: collecting sampling voltage of a single-phase line in a distribution line by using the ground fault monitoring device;
s20: comparing the collected sampling voltage of the single-phase line with a first preset voltage, and if the sampling voltage is smaller than the first preset voltage, judging that the single-phase line is in a power failure state; if the sampling voltage is greater than or equal to a first preset voltage, comparing the sampling voltage with a second preset voltage, wherein the second preset voltage is greater than the first preset voltage;
s30: if the sampling voltage is greater than or equal to a second preset voltage, the single-phase line is judged to normally work, and the third preset voltage is greater than the second preset voltage; and if the sampling voltage is less than a second preset voltage, judging that the single-phase line has a ground fault.
7. The ground fault monitoring method of claim 6,
the step S10 further comprises the steps of collecting the sampling current of the single-phase line in the distribution line;
step S20 is that, if the sampling voltage is less than a first preset voltage and the sampling current is equal to zero, it is determined that the single-phase line is in a power failure state; if the sampling voltage is greater than or equal to a first preset voltage and the sampling current is not equal to zero, comparing the sampling voltage with a second preset voltage;
step S30, if the sampling voltage is greater than or equal to a second preset voltage and the sampling current is not equal to zero, comparing the sampling voltage with a third preset voltage, and if the sampling voltage is greater than the third preset voltage, determining that the single-phase line works normally; and if the sampling voltage is less than a second preset voltage and the sampling current is not equal to zero, judging that the single-phase line has a ground fault.
8. The ground fault monitoring method according to claim 6 or 7, wherein the step S30 further comprises: and if the sampling voltage is greater than a third preset voltage, correcting the sampling voltage according to the height of the single-phase line and the environmental humidity, and judging that the single-phase line works normally if the corrected sampling voltage is greater than the third preset voltage.
9. The ground fault monitoring method according to claim 6 or 7, wherein the step S30 further comprises S31: if the sampling voltage is smaller than a second preset voltage, calculating a difference value between the sampling voltage of the single-phase line and the sampling voltages of other two-phase single-phase lines and a percentage value between the difference value and the sampling voltages of other two-phase single-phase lines, and if the percentage value is larger than a first preset threshold value, judging that the single-phase line has a ground fault.
10. The ground fault monitoring method of claim 9, wherein the step S30 further comprises the step S32: and calculating the probability of the occurrence of the primary ground fault A from each power supply branch Li by using a Bayesian formula according to the frequency of the occurrence of the ground fault of each power supply branch in the power distribution network in history, the length of each power supply branch and the total length ratio of the whole power distribution network line.
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