CN112147409B - Online impedance detection method and device for low-voltage distribution line - Google Patents
Online impedance detection method and device for low-voltage distribution line Download PDFInfo
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- CN112147409B CN112147409B CN202010871874.XA CN202010871874A CN112147409B CN 112147409 B CN112147409 B CN 112147409B CN 202010871874 A CN202010871874 A CN 202010871874A CN 112147409 B CN112147409 B CN 112147409B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
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- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
Abstract
The invention discloses a method and a device for detecting the online impedance of a low-voltage distribution line, comprising the following steps: s1, acquiring voltage and current signals of a target distribution line monitored by an electric energy meter in real time, and calculating the voltage and current change rate in a specified time period; s2, determining to obtain a loop impedance value of the target distribution line according to the calculated voltage change rate and current change rate; and S3, obtaining the loop impedance value obtained in the appointed time period, obtaining the loop impedance variation trend of the target distribution line, and determining the impedance variation state of the target distribution line according to the loop impedance variation trend. The method can realize the online detection of the impedance of the low-voltage distribution line and evaluate the impedance change state of the distribution line in real time, and has the advantages of simple realization method, low required cost, good real-time property, high detection precision and efficiency and the like.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a method and a device for detecting online impedance of a low-voltage distribution line.
Background
In an electric power system, the electric energy of a low-voltage distribution line is usually measured and counted by using an intelligent meter, the low-voltage distribution line can gradually have the problems of line aging or equipment aging and the like after being used for a long time, and the line aging or the equipment aging can generate power transmission faults to influence the stability and reliability of power transmission. In order to ensure the stability and reliability of the distribution line, special fault monitoring equipment is usually arranged at present to monitor the line aging or equipment aging faults, but the method is high in cost and complex in operation, the faults of the line can be monitored only after the faults occur, the faults cannot be predicted to be processed in time, and the faults cannot be avoided.
In the process of power distribution line aging or equipment aging, the corresponding line impedance changes gradually, but currently, only the intelligent electric energy meter is used as a metering terminal, and the impedance state of the power distribution line is not analyzed by fully utilizing the detection data of the electric energy meter. For the impedance of the power distribution and transmission line, the impedance is usually obtained by analyzing the electrical loss for the line at present, but the implementation of the method is complex, the line loss analysis has uncertain factors, the actual line loss is difficult to obtain correctly, and the impedance finally obtained by analyzing the electrical loss for the line is only an estimated value, so the accuracy is not high.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: aiming at the technical problems in the prior art, the invention provides the low-voltage distribution line online impedance detection method which is simple in implementation method, low in required cost, good in real-time performance, high in execution precision and high in efficiency, and can realize the online impedance analysis of the low-voltage distribution line and evaluate the impedance change state of the distribution line in real time.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
an online impedance detection method for a low-voltage distribution line comprises the following steps:
s1, acquiring voltage and current signals of a target distribution line monitored by an electric energy meter in real time, and calculating the voltage and current change rate in a specified time period;
s2, determining to obtain a loop impedance value of the target distribution line according to the calculated voltage change rate and current change rate;
and S3, obtaining the loop impedance value obtained in the appointed time period, obtaining the loop impedance variation trend of the target distribution line, and evaluating the impedance variation state of the target distribution line according to the loop impedance variation trend.
As a further improvement of the invention: the step S2 is as follows
And calculating to obtain the loop impedance value, wherein Δ V is the voltage change value of the detection electric energy meter at different moments, and Δ I is the current change value of the detection electric energy meter at different moments.
As a further improvement of the invention: the voltage change value is specifically an average change rate value of the voltage measurement value in a specified time period, and the current change value is an average change rate value of the current measurement value in a specified time period.
As a further improvement of the invention: and step S2, acquiring loop impedance value samples of the designated line at designated intervals to perform estimation processing, and estimating to obtain a single impedance estimation value of the designated line.
As a further improvement of the invention: the method further comprises a step of constructing a monitoring system before the step S1, and the specific steps comprise: the method comprises the steps that at least one total detection electric energy meter is arranged at a power end of a power grid, two detection branches respectively connected with the total detection electric energy meter are arranged, each detection branch is provided with at least one branch detection electric energy meter, the voltage and the current value of a power supply of the power grid are monitored through the total detection electric energy meter, and the voltage and the current value of each detection branch are monitored through each branch detection electric energy meter.
As a further improvement of the invention: in step S1, voltage and current measurement values of the total electric energy meter and the branch electric energy meter in different load states are respectively obtained, and voltage and current difference values of the total electric energy meter and the branch electric energy meter in different load states are respectively calculated;
in the step S2, the line impedance value of the corresponding detection branch is calculated from the voltage and current difference values correspondingly obtained by the branch detection electric energy meter, and the impedance attenuation value between the total electric energy meter and the branch detection electric energy meter is calculated from the voltage and current difference values correspondingly obtained by the total electric energy meter and the line impedance values of the detection branches.
As a further improvement of the invention: the calculating to obtain the line impedance of the corresponding detection branch comprises: calculating to obtain an initial line impedance value by using voltage and current difference values of the branch detection electric energy meter between two different load states, and counting the initial line impedance values obtained by calculation to obtain a final line impedance value;
the step of calculating the impedance between the total electric energy meter and the branch electric energy meter comprises: and respectively calculating to obtain an initial total impedance value according to the voltage and current difference values of the total electric energy meter between two different load states, counting the initial total impedance values obtained by calculation to obtain a final total impedance value, and subtracting the line impedance value of each detection branch circuit from the total impedance value to obtain an impedance attenuation value between the total electric energy meter and the branch circuit electric energy meter.
As a further improvement of the invention: the step S3 further includes determining an aging state of the target distribution line according to the impedance change state evaluation result obtained by the target distribution line within the specified time period.
As a further improvement of the present invention, said judging the aging state of the line includes: and respectively constructing a loop impedance change model when the distribution line is in an attenuation state and equipment is aged in advance, matching and comparing the impedance change state evaluation result with the loop impedance change model, and judging the attenuation state and the equipment aging state of the target distribution line.
The on-line impedance detection device for the low-voltage distribution line comprises an electric energy meter and a processor, wherein the electric energy meter is connected with the processor, the electric energy meter is used for monitoring voltage and current signals of a target distribution line in real time, and the processor is used for executing the steps of the method.
As a further improvement of the present invention, the monitoring system specifically includes at least one total detection electric energy meter arranged at a power end of the power grid, and two detection branches respectively connected to the total detection electric energy meter, each detection branch is provided with at least one branch detection electric energy meter, the voltage and the current values of the power grid power supply are monitored by the total detection electric energy meter, and the voltage and the current values of each detection branch are monitored by each branch detection electric energy meter.
Compared with the prior art, the invention has the advantages that:
1. according to the on-line impedance detection method for the low-voltage distribution line, the voltage and current signals of the target distribution line are monitored in real time, the loop impedance value is determined and obtained by utilizing the voltage change rate and the current change rate, the implementation mode is simple, the real-time electric energy measurement data can be fully utilized to monitor the impedance of the distribution line, meanwhile, the impedance change state of the target distribution line is evaluated by counting the loop impedance change trend of the distribution line, the impedance change monitoring of the distribution line can be realized, active operation and maintenance can be realized, and the power supply reliability is improved.
2. According to the on-line impedance detection method for the low-voltage distribution line, the aging state of the distribution line can be further evaluated by monitoring the impedance change state of the target distribution line, so that faults such as line aging or equipment aging can be judged in advance, early warning can be timely carried out, and the faults caused by line and equipment aging can be greatly reduced.
Drawings
Fig. 1 is a schematic flow chart of an implementation of the method for detecting the on-line impedance of the low-voltage distribution line according to the embodiment.
Fig. 2 is a schematic diagram of the principle of calculating the loop impedance according to the embodiment of the present invention.
Fig. 3 is a schematic diagram of a monitoring system constructed in an embodiment of the present invention.
Fig. 4 is a schematic diagram of the measurement data results of the electric energy meter obtained in the embodiment of the present invention.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
As shown in fig. 1, the method for detecting the on-line impedance of the low-voltage distribution line in the embodiment includes the following steps:
s1, acquiring voltage and current signals of a target distribution line monitored by an electric energy meter in real time, and calculating the voltage and current change rate in a specified time period;
s2, determining to obtain a loop impedance value of the target distribution line according to the calculated voltage change rate and current change rate;
and S3, obtaining the loop impedance value obtained in the appointed time period, obtaining the loop impedance variation trend of the target distribution line, and evaluating the impedance variation state of the target distribution line according to the loop impedance variation trend.
The line impedance can be obtained by delta V and delta I change increment caused by corresponding relative time change, wherein delta V/delta I is caused by delta I change and load change, the load front-end line impedance comprising the power supply internal resistance can be obtained by delta V/delta I, the load property has no direct influence on the measured value, for example, the loop impedance can not be influenced even if power is reversed due to solar power generation, the value can be changed when other users in the same network go on or off, when the observed voltage drop amplitude is higher, the measured loop impedance can also be higher, and the influence can be reduced by taking the change rate. This embodiment utilizes above-mentioned characteristic, voltage through real-time supervision target distribution lines, current signal, utilize voltage change rate, the current change rate is confirmed and is obtained the return circuit impedance value, the implementation is simple, can make full use of real-time electric energy measured data realize the monitoring of distribution lines impedance, simultaneously through the return circuit impedance variation trend of statistics distribution lines, the impedance change state of aassessment target distribution lines, can realize the impedance state change monitoring of distribution lines, thereby can realize initiative fortune dimension, improve the power supply reliability.
The aging of the distribution line is a slow and gradual process, and the corresponding line impedance changes gradually in the process of the aging of the distribution line or equipment, and the impedance change is a main variable in the aging process. This embodiment is based on above-mentioned characteristic, through the impedance change state of target distribution lines, can further aassessment distribution lines's ageing state to judge in advance that the circuit takes place trouble such as ageing or equipment ageing, in time carry out the early warning in advance, the trouble that can the ageing cause of the circuit of significantly reducing and equipment takes place, thereby guides overall planning etc. of standard safety power consumption and whole circuit. This embodiment specifically carries out above-mentioned impedance analysis through the mass data of collecting the electric energy meter collection among the collection distribution lines, can obtain the real-time impedance of whole distribution network circuit, carries out effective monitoring to low pressure distribution lines return circuit impedance, can discern the line impedance change by the data statistics of appointed long time quantum, and then can analyze which belongs to the impedance change that the circuit is ageing to cause, realizes the prejudgement of circuit ageing trouble.
The electric energy meter of the embodiment can specifically use an intelligent electric energy meter so as to further improve the analysis efficiency and precision, and other types of electric energy meters can be adopted according to actual requirements.
In step S1, the voltage and current signal values measured by the detection electric energy meter at two or more times are obtained to calculate the voltage and current change rates, and the impedance is calculated according to the change rates, so that the deviation caused by the instantaneous measured values of the voltage and current can be reduced, and the impedance calculation accuracy can be improved. The voltage/current at a single moment is the load impedance, and in this embodiment, each impedance value is the loop impedance, not the load impedance.
Fig. 2 is a typical wiring diagram of a power distribution network, and further illustrates the above-mentioned method for detecting line impedance in this embodiment. Wherein the line impedance of different nodes of the distribution line is Rs, Rd, Rcsn, V supply For a power supply of a power grid, a loop impedance value is determined by measuring the change rate of voltage and current at two moments a and b, and the calculation formula of the loop impedance value is as follows:
wherein, Δ V is the voltage difference between a and b, i.e. Δ V ═ V NB -V NA Δ I is the difference between the currents at two times a and b, i.e. Δ I ═ I NB -I NA Then, there are:
at two moments a and B, respectively using thevenin's theorem, we can get:
V NB ＝V supply -(R s +R d +R csn )*I NB (3)
V NA ＝V supply -(R s +R d +R csn )*I NA (4)
suppose V supply Kept constant during the measurement, there are:
according to the formula, the loop impedance value of the distribution line can be calculated through the voltage difference value and the current difference value at two moments, when other users in the same network go on or off, the measured value changes, the measured loop resistance value of the line is higher, and the influence can be further reduced by averaging the change rate in subsequent calculation.
Step S2 of the present embodiment is specifically described
And calculating to obtain loop impedance values of the distribution line, wherein the delta V is a voltage change value measured by the detection electric energy meter at different moments, and the delta I is a current change value measured by the detection electric energy meter at different moments. The delta V can be obtained by measuring the electric energy meter at two momentsDelta I is a current difference value measured by the electric energy meters at two moments; the delta V can also be used for obtaining an average change rate value of the voltage measurement value in a specified time period, the delta I is used for obtaining an average change rate value of the current measurement value in a specified time period, the deviation caused by the instantaneous measurement values of the voltage and the current is further reduced by the average change rate value, and the impedance calculation precision is improved.
In this embodiment, a mathematical statistics method is further applied, and loop impedance value samples of the designated line are collected at designated intervals for estimation, so that a single impedance estimation value of a certain line can be estimated, and the confidence level increases with the increase of the estimation number. In a specific application embodiment, an estimation method based on a weighted least square method can be adopted, a measurement weight matrix is set by utilizing normal distribution parameters, a 95% confidence interval of a state is estimated, and an impedance estimation result is described by a reasonable interval rather than a determined numerical value, so that a line impedance value can be described more accurately.
Assuming that the time difference between the above-mentioned a and b is 5 minutes, it may be set that 144 impedance estimation values are collected each day, and the average value of each impedance estimation value sample is taken as the impedance estimation value of the last day, that is, the impedance estimation value of the day is the median (impedance estimation value sample). Assuming the data is normally distributed, Student's-t distribution can be used to test to estimate the confidence interval of the results, based on
And wherein
If a ═ t (0.05, n-1) ≈ 2, the confidence is 95% if the sample size is greater than 30. Namely, the line impedance value can be described more accurately through the estimation processing of the loop impedance value sample.
In this embodiment, before step S1, a step of constructing a monitoring system is further included, and the specific steps include: the method comprises the steps that at least one total electric energy meter is arranged at a power supply end of a power grid, two detection branches connected with the total electric energy meter are arranged, each detection branch is provided with at least one branch electric energy meter, the voltage and the current of a power grid power supply are monitored through the total electric energy meter, and the voltage and the current of each detection branch are monitored through each branch electric energy meter. The constructed monitoring system can monitor the total electric energy data of the distribution line at the power end of a power grid and the electric energy data of each branch after the total electric energy is branched in real time, and the impedance value of each node in the line can be obtained through the measurement data of each electric energy meter, so that the monitoring of the impedance state of each node is realized.
In this embodiment, in step S1, voltage and current measurement values of each total electric energy meter and each branch electric energy meter in different load states are specifically and respectively obtained, where the load states include an unloaded state and different load value states, and voltage and current difference values of each total electric energy meter and each branch electric energy meter in different load states are respectively calculated;
in step S2, the line impedance value of the corresponding detection branch is calculated from the voltage and current difference values correspondingly obtained by the branch detection electric energy meter, and the impedance value between the total electric energy meter and the branch electric energy meter is calculated from the voltage and current difference values correspondingly obtained by the total electric energy meter and the line impedance value of each detection branch, so that the impedance state monitoring of each node between each detection branch and the electric energy meter can be realized.
In this embodiment, the above calculating to obtain the line impedance of the corresponding detection branch specifically includes: calculating to obtain an initial line impedance value by the voltage and current difference value of the branch electric energy meter between two different load states, and counting the initial line impedance values obtained by calculation to obtain a final line impedance value;
the impedance between the total electric energy meter and the branch electric energy meter obtained through the calculation is specifically as follows: and respectively calculating to obtain an initial total impedance value according to the voltage and current difference values of the total electric energy meter between two different load states, counting each initial total impedance value obtained by calculation to obtain a final total impedance value, and subtracting the line impedance value of each detection branch circuit from the total impedance value to obtain an impedance attenuation value between the total electric energy meter and the branch circuit electric energy meter.
In the above steps of this embodiment, the impedance value is calculated by integrating the measured values of the electric energy of each electric energy meter in various different load states, so that the information of different load states can be fully considered, and the impedance detection precision is further improved, thereby realizing the accurate detection of the impedance of each node.
In a specific application embodiment, an initial line impedance value can be calculated according to the voltage and current difference value of the branch electric energy meter between every two different load states, and then the average value of the initial line impedance values is taken as a final line impedance value; and calculating an initial total impedance value according to the voltage and current difference value of the total electric energy meter between every two different load states, taking the average value of the initial total impedance values as a final total impedance value, and subtracting the branch impedance values from the total impedance value to obtain the impedance attenuation value between the total electric energy meter and the branch electric energy meters.
The monitoring system constructed in the specific application embodiment of the invention is shown in fig. 3, wherein the auxiliary meter is a main loop measuring meter which can visually reflect the output value of the low-voltage power supply, the auxiliary meter is a main electric energy meter, the first electric meter and the auxiliary meter belong to a loop and reflect the measurement of the same group of detection branch circuits, and the second electric meter and the auxiliary meter belong to a group of measurement loops and reflect the measurement of the other group of detection branch circuits. The monitoring data of each electric energy meter obtained at a certain moment is shown in fig. 4, wherein no load is no load in a loop, the current obtained by the auxiliary meter II is caused by the power consumption of the meter, the load I is a linear resistor of 150 ohms, the load II is a linear resistor of 75 ohms, delta is a relative difference value obtained by two times of acquisition of metering points in the same group and is divided into voltage and current, the ratio of the difference values of the voltage and the current is input total impedance, and the line impedance obtained by the ratio of the difference values of the voltage and the current of the auxiliary meter II is R n +R n1 +R n2 +R n4 The line impedance obtained by the ratio of the difference value between the voltage and the current of the auxiliary meter three and the auxiliary meter four is R n +R n1 +R n2 +R n3 +R n4 And subtracting the line impedance measured by the auxiliary meter three and the auxiliary meter four from the auxiliary meter two respectively to obtain the impedance attenuation between the auxiliary meter three and the auxiliary meter two.
Step S3 of this embodiment further includes determining the aging status of the target distribution line according to the evaluation result of the impedance change status of the target distribution line in the specified time period. When line aging or equipment aging occurs in the distribution line, the loop impedance can be changed in a certain trend, after the input impedance value of the line is calculated by utilizing real-time measurement data of an electric energy meter, the impedance change trend and rule can be obtained within a certain time period, the impedance change state is estimated according to the impedance change trend and rule, the aging state of the distribution line is judged according to the impedance change state, the attenuation characteristic trend of the line can be judged in advance, the line aging trend can be researched and judged early, and the safety and reliability of power utilization are improved.
The present embodiment determines the aging state of the line as follows: and respectively constructing loop impedance change models of the distribution line in the attenuation state and the equipment aging state in advance, matching and comparing the impedance change state evaluation result with the loop impedance change models, and judging the attenuation state and the equipment aging state of the target distribution line. A large amount of historical data in the operation process of the distribution line can be used for constructing a loop impedance change model, the impedance change trend of the distribution line during line aging or equipment aging is reflected by the loop impedance change model, and the attenuation state and the equipment aging state of the distribution line can be judged quickly and accurately by matching and comparing the loop impedance change model with the loop impedance change model after the loop impedance change monitored in real time.
This embodiment specifically constructs the return circuit impedance change model when different positions are in the decay state in the distribution lines respectively, when different equipment is in the ageing state, and the return circuit impedance change that will monitor in real time matches the comparison with this return circuit impedance change model, can predetermine the decay state and the equipment ageing state of current distribution lines, can discern specific ageing fault type simultaneously, realizes the fault location, can determine which partial circuit takes place to age or which partial equipment takes place to age the trouble.
The embodiment also provides an online impedance detection device for the low-voltage distribution line, which comprises an electric energy meter and a processor which are connected with each other, wherein the electric energy meter is used for monitoring voltage and current signals of the target distribution line in real time, and the electric energy meter processor is used for executing the steps of the method. The electric energy meter is specifically arranged in each distribution circuit to be monitored, and the processor performs online impedance detection according to the method to obtain the impedance state of each distribution circuit.
As shown in fig. 3, the monitoring system in this embodiment specifically includes at least one total detection electric energy meter arranged at a power end of the power grid, and two detection branches connected to the total detection electric energy meter, where each detection branch is provided with at least one branch detection electric energy meter, and monitors the voltage and the current of the power grid through the total detection electric energy meter, and monitors the voltage and the current of each detection branch through each branch detection electric energy meter, as specifically described above.
The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.
Claims (8)
1. An online impedance detection method for a low-voltage distribution line is characterized by comprising the following steps:
s1, acquiring voltage and current signals of a target distribution line monitored by an electric energy meter in real time, and calculating the voltage and current change rate in a specified time period;
s2, determining to obtain a loop impedance value of the target distribution line according to the calculated voltage change rate and current change rate;
s3, obtaining the loop impedance value obtained in a specified time period, obtaining the loop impedance variation trend of the target distribution line, and determining the impedance variation state of the target distribution line according to the loop impedance variation trend;
the method further comprises a step of constructing a monitoring system before the step S1, and the specific steps comprise: arranging at least one total detection electric energy meter at a power end of a power grid, and arranging two detection branches respectively connected with the total detection electric energy meter, wherein each detection branch is provided with at least one branch detection electric energy meter, the voltage and the current value of the power supply of the power grid are monitored through the total detection electric energy meter, and the voltage and the current value of each detection branch are monitored through each branch detection electric energy meter;
in step S1, obtaining voltage and current measurement values of each of the total detected electric energy meter and the branch electric energy meter in different load states, and calculating voltage and current difference values of each of the total detected electric energy meter and the branch electric energy meter in different load states;
in the step S2, the line impedance value of the corresponding detection branch is calculated from the voltage and current difference values correspondingly obtained by the branch detection electric energy meter, and the impedance attenuation value between the total detection electric energy meter and the branch detection electric energy meter is calculated from the voltage and current difference values correspondingly obtained by the total detection electric energy meter and the line impedance values of the detection branches.
2. The on-line impedance detection method for the low-voltage distribution line according to claim 1, wherein: the step S2 is as follows
And calculating to obtain the loop impedance value, wherein Δ V is the voltage change value of the detection electric energy meter at different moments, and Δ I is the current change value of the detection electric energy meter at different moments.
3. The on-line impedance detection method for the low-voltage distribution line according to claim 2, wherein: the voltage change value is specifically an average change rate value of the voltage measurement value in a specified time period, and the current change value is an average change rate value of the current measurement value in a specified time period.
4. The on-line impedance detection method for the low-voltage distribution line according to claim 1, wherein: and step S2, acquiring loop impedance value samples of the designated line at designated intervals to perform estimation processing, and estimating to obtain a single impedance estimation value of the designated line.
5. The on-line impedance detection method for the low-voltage distribution line according to claim 1, wherein: the calculating to obtain the line impedance of the corresponding detection branch comprises: calculating to obtain an initial line impedance value by using voltage and current difference values of the branch detection electric energy meter between two different load states, and counting the initial line impedance values obtained by calculation to obtain a final line impedance value;
the step of obtaining the impedance between the total detection electric energy meter and the branch electric energy meter through calculation comprises the following steps: and respectively calculating to obtain an initial total impedance value according to the voltage and current difference values of the total detection electric energy meter between two different load states, counting the initial total impedance values obtained by calculation to obtain a final total impedance value, and subtracting the line impedance value of each detection branch circuit from the total impedance value to obtain an impedance attenuation value between the total detection electric energy meter and the branch circuit electric energy meter.
6. The method for detecting the on-line impedance of the low-voltage distribution line according to any one of claims 1 to 4, wherein the step S3 further comprises the step of judging the aging state of the target distribution line according to the estimation result of the impedance change state of the target distribution line in a specified time period, wherein the judging the aging state of the line comprises: and respectively constructing loop impedance change models of the distribution line in an attenuation state and equipment aging in advance, matching and comparing the impedance change state evaluation result with the loop impedance change models, and judging the attenuation state and the equipment aging state of the target distribution line.
7. The utility model provides an online impedance detection device of low pressure distribution lines which characterized in that: the method comprises a monitoring system and a processor which are connected with each other, wherein the monitoring system comprises an electric energy meter which is used for monitoring voltage and current signals of a target distribution line in real time, and the processor is used for executing the steps of the method according to any one of claims 1-6.
8. The on-line impedance detection device for low-voltage distribution lines of claim 7, wherein: the monitoring system specifically comprises at least one total detection electric energy meter arranged at a power end of a power grid and two detection branches respectively connected with the total detection electric energy meter, wherein each detection branch is provided with at least one branch detection electric energy meter, the voltage and the current of the power grid are monitored through the total detection electric energy meter, and the voltage and the current of each detection branch are monitored through each branch detection electric energy meter.
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