CN111007315B - Circuit branch identification method based on current harmonic spectrum - Google Patents

Abstract

The invention proposes a line branch identification method based on the current harmonic spectrum. The line branch identification method is used for identifying whether the line branch belongs to a certain outlet line of the upper-level node. The method for identifying a line branch based on current harmonics measures the current harmonic spectrum of the branch line reference point and the point to be measured and calculates the distance, and identifies whether the point to be measured and the reference point are based on whether the distance exceeds a preset threshold. belong to the same line branch. The line branch identification device based on the current harmonic spectrum is composed of a clamp current transformer, an AD acquisition module, a main processing module, a communication module and a display module, and the currents of the reference point and the measured point are respectively measured for all branches. Harmonic spectrum and branch identification are performed to complete the topology identification of line branches in the area to which they belong. The method is a non-invasive measurement and will not affect the system operation; meanwhile, the reliability and accuracy are ensured due to the use of the current harmonic spectrum.

Description

A Line Branch Identification Method Based on Current Harmonic Spectrum

technical field

The invention belongs to the technical field of power transmission and distribution in power systems, and in particular relates to a line branch identification method based on a current harmonic map.

Background technique

The line branch referred to in the present invention refers to the topological path of the line from the power supply or the output side of the transformer to the next-level transformers or loads, especially the topological branches (station area) between the low-voltage transformer and the user meter. -phase-branch-household relationship). The branch identification referred to in the present invention is to confirm the one-to-one correspondence between the outgoing line of the branch node of the upper level and the line to be tested (especially the incoming line of the branch node of the next level).

Since the locations where line branches appear are mainly at the feeder outlet, T connection, branch pole, branch box, etc., the identification objects targeted by the present invention are also the incoming and outgoing lines of these locations and the incoming line positions of the user's meter terminal.

Due to the transformation of the power grid and the access of new energy sources, the topology of power lines has changed, which brings challenges to power maintenance and operation. In the process of power maintenance and line inspection, it is often necessary to confirm the outlet line to which a certain power line belongs. Especially for underground cables, pipeline orientation and line topology are often difficult to identify. An application scenario of the present invention is to confirm the direction of the cable in the power line inspection.

In the construction of the information system of the distribution network, the information inconsistency occurs from time to time due to the transformation of the station line in the low-voltage side power supply area of the 10kV/0.4kV distribution transformer, and the change of users. The file information is incomplete; or the topological relationship recorded by the user file information does not match the actual topological relationship. These errors will affect the normal operation of the business based on the topology of the distribution network. The traditional manual record modification consumes a lot of manpower and time, and cannot meet the needs of accuracy and efficiency. Identifying the line branches of the distribution network is another application scenario of the present invention.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the prior art, the present invention provides a line branch identification method based on a current harmonic spectrum, which uses the principle that the current harmonic characteristic spectrum of the same branch circuit is similar to realize the identification and verification of the line branch relationship, and solves the problem of electric power. The problem of line and cable branch topology identification provides technical support for scenarios such as power line inspection, maintenance, and station topology branch verification.

The technical scheme of the method of the present invention is applied to a line branch identification device based on current harmonics, which is characterized in that it comprises: a clamp current transformer, an AD acquisition module, a main processing module, a communication module, and a display module; the The clamp current transformer, the AD acquisition module, and the main processing module are connected in series in sequence; the main processing module is respectively connected with the communication module and the display module in sequence;

The clamp-shaped current transformer is used for the current signal of the reference point or the current signal of the point to be measured; the AD acquisition module is used to perform analog-to-digital conversion on the current signal to obtain the digital current signal of the on-site measurement reference point or the on-site measurement to be measured. The digital current signal of the point; the main processing module is used to carry out the line branch identification algorithm based on the current harmonic spectrum according to the digital current signal of the on-site measurement reference point or the digital current signal of the on-site measurement point to be measured, and display the branch results. into the display module; the communication module is used for data exchange and communication between the two sets of the current harmonic-based line branch identification devices, between the on-site measurement reference point and the on-site measurement to-be-measured point; the display module uses to display the recognition results.

The technical scheme of the method of the present invention is a line branch identification method based on a current harmonic spectrum, which specifically includes the following steps:

Step 1: Select the first section of a branch on the outlet side as the reference point, and the end of the line to be measured as the point to be measured, deploy the line branch identification device based on current harmonics at the reference point and the point to be measured, respectively, and collect Obtaining the digital current signal or the current signal sampling value sequence of the point to be measured, and further processing by the main processing module to obtain the current harmonic spectrum vectors of the reference point and the point to be measured respectively;

Step 2: Calculate the distance between the current harmonic vector of the reference point and the current harmonic vector spectrum of the point to be measured. When the distance is smaller than the distance threshold, it is considered that the point to be measured and the reference point belong to the same branch, otherwise they do not belong to the same branch;

Step 3: Take all branch outgoing lines as reference points in turn, and identify the ends of all lines to be tested through Step 1 and Step 2, and then confirm the topology of all branches.

Preferably, in step 1, the digital current signal or the current signal sampling value sequence of the point to be measured is collected and obtained respectively, specifically:

The current signal of the measurement reference point obtained through the synchronous acquisition of the clamp current transformer is: x ₁ (t), and the current signal of the point to be measured is x ₂ (t);

The current signal of the measurement reference point and the current signal of the to-be-measured point are respectively subjected to analog-to-digital conversion by the AD acquisition module, and the current signal sampling value sequence of the reference point is obtained respectively: x ₁ (n), the current signal of the to-be-measured point is sampled. The sequence of values is x ₂ (n);

The main processing module obtains the frequency domain components X ₁ (k) and X ₂ (k) by adopting FFT transformation on the sequences x ₁ (n) and x ₂ (n) respectively;

Obtain the current frequency domain component amplitude sequence at the reference point: {x _1n |n=1,2,…N}, and obtain the current frequency domain component phase angle sequence at the reference point: {θ _1n |n=1,2, ...N};

Obtain the current frequency domain component amplitude sequence of the point to be measured: {x _2n |n=1,2,…N}, and obtain the current frequency domain component phase angle sequence of the test point: {θ _2n |n=1, 2,...N}, form two sets of current harmonic spectrum vectors, that is, the current harmonic spectrum vector of the reference point is: IG ₁ , and the current harmonic spectrum vector of the point to be measured is: IG ₂

IG ₁ ={(x ₁₁ ,θ ₁₁ ),(x ₁₂ ,θ ₁₂ ),…,(x _1N ,θ _1N )}

IG ₂ ={(x ₁₁ ,θ ₁₁ ),(x ₁₂ ,θ ₁₂ ),…,(x _1N ,θ _2N )}

Preferably, the distance between the two groups of current harmonic spectra calculated in step 2 is D(IG ₁ , IG ₂ ), and the specific calculation method is:

The distance threshold described in step 2 is ε.

The beneficial effects of the present invention are:

accuracy. The line branch identification method based on the current harmonics provided by the present invention reflects the dynamic change characteristics of the load characteristics of different branches in theory, and is the essential feature of distinguishing different branches, so it has extremely high accuracy.

Non-invasive measurement. The device provided by the invention uses a clamp-shaped current transformer to measure the line, does not inject signals into the line, and does not affect the operation of the line and the existing load equipment.

Ease of use. The device used in the present invention can carry out portable and miniaturized design in specific implementation, and is easy to operate and easy to carry.

Description of drawings

FIG. 1 is a block diagram of the hardware implementation of the device involved in the present invention.

Figure 2: is the identification flow chart involved in the present invention.

Detailed ways

In order to more clearly illustrate the present invention and/or the technical solutions in the prior art, specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative efforts, and obtain other implementations.

The theoretical basis of this invention is Kirchhoff's current law. According to Kirchhoff's current law, the current on the same circuit is equal everywhere. However, the power frequency current is an alternating current whose instantaneous value changes dynamically with time. At the same time, since the load of each branch, especially the nonlinear load, is also changing dynamically, the current fundamental wave and harmonics on the line are dynamically changing with time. The present invention uses the current harmonic feature map to identify the line branch, assuming that different line branch lengths, load impedances, and operating states are different, so that the current harmonic feature maps of different branches have corresponding differences for identification. For different line branches, the greater the difference in dynamic operation characteristics, the greater the distance of the current harmonic spectrum.

To express the distance between the current harmonic profiles, the invention uses the Euclidean Distance using a two-dimensional vector for calculation. Let the current frequency domain component amplitude and phase angle sequence of the reference point and the point to be measured {x _1n |n=1,2,…N}, {θ _1n |n=1,2,…N}, {x _2n | n=1,2,...N}, {θ _2n |n=1,2,...N}, then the current harmonic spectra IG ₁ and IG ₂ are respectively:

IG ₁ ={(x ₁₁ ,θ ₁₁ ),(x ₁₂ ,θ ₁₂ ),…,(x _1N ,θ _1N )}

IG ₂ ={(x ₁₁ ,θ ₁₁ ),(x ₁₂ ,θ ₁₂ ),…,(x _1N ,θ _2N )}

The formula for calculating the distance between the reference point and the current harmonic spectrum of the point to be measured is:

In the embodiment of the present invention, the maximum current harmonic order N is taken as the 61st order.

As shown in FIG. 1 , the technical solution of the device in the specific embodiment of the present invention is a line branch identification device based on current harmonics, which is characterized in that it includes: a clamp current transformer, an AD acquisition module, a main processing module, a communication module and display module; the clamp current transformer, the AD acquisition module and the main processing module are connected in series in sequence; the main processing module is respectively connected with the communication module and the display module in sequence;

The clamp-shaped current transformer adopts the model ETCR030A-3V, which is used for the current signal of the reference point or the current signal of the point to be measured;

The AD acquisition module is selected as AD7607, which is used to perform analog-to-digital conversion on the current signal to obtain the digital current signal of the on-site measurement reference point or the digital current signal of the on-site measurement point to be measured;

The main processing module adopts the chip STM32F767, which is used to perform the line branch identification algorithm based on the current harmonic spectrum according to the digital current signal of the on-site measurement reference point or the digital current signal of the on-site measurement point to be measured, and display the branch results to the display. in the module;

The communication module is based on the LoRa module of the chip Sx1278, and is used for data exchange and communication between the two sets of the current harmonic-based line branch identification devices between the on-site measurement reference point and the on-site measurement to-be-measured point;

The display module adopts a serial LCD touch screen, which is used to display the recognition result.

As shown in FIG. 1 , the technical solution of the method in the specific embodiment of the present invention is a line branch identification method based on a current harmonic spectrum, which specifically includes the following steps:

Step 1: Select the first section of a branch on the outgoing line as the reference point, and the end of the line to be measured as the point to be measured, and deploy the line branch identification device based on current harmonics at the reference point and the point to be measured, respectively. Obtaining the digital current signal or the current signal sampling value sequence of the point to be measured, and further processing by the main processing module to obtain the current harmonic spectrum vectors of the reference point and the point to be measured respectively;

As described in step 1, the digital current signal or the current signal sampling value sequence of the point to be measured is respectively collected and obtained, specifically:

The current signal of the measurement reference point obtained through the synchronous acquisition of the clamp current transformer is: x ₁ (t), and the current signal of the point to be measured is x ₂ (t);

The current signal of the measurement reference point and the current signal of the to-be-measured point are respectively subjected to analog-to-digital conversion by the AD acquisition module, and the current signal sampling value sequence of the reference point is obtained respectively: x ₁ (n), the current signal of the to-be-measured point is sampled. The sequence of values is x ₂ (n);

The main processing module obtains the frequency domain components X ₁ (k) and X ₂ (k) by adopting FFT transformation on the sequences x ₁ (n) and x ₂ (n) respectively;

Obtain the current frequency domain component amplitude sequence at the reference point: {x _1n |n=1,2,…N}, and obtain the current frequency domain component phase angle sequence at the reference point: {θ _1n |n=1,2, ...N};

Obtain the current frequency domain component amplitude sequence of the point to be measured: {x _2n |n=1,2,…N}, and obtain the current frequency domain component phase angle sequence of the test point: {θ _2n |n=1, 2,...N}, form two sets of current harmonic spectrum vectors, that is, the current harmonic spectrum vector of the reference point is: IG ₁ , and the current harmonic spectrum vector of the point to be measured is: IG ₂

IG ₁ ={(x ₁₁ ,θ ₁₁ ),(x ₁₂ ,θ ₁₂ ),…,(x _1N ,θ _1N )}

IG ₂ ={(x ₁₁ ,θ ₁₁ ),(x ₁₂ ,θ ₁₂ ),…,(x _1N ,θ _2N )}

Among them, N=61 is the maximum current harmonic order.

Step 2: Calculate the distance between the current harmonic vector of the reference point and the current harmonic vector spectrum of the point to be measured. When the distance is less than the threshold, it is considered that the point to be measured and the reference point belong to the same branch, otherwise they do not belong to the same branch;

The distance between the two groups of current harmonic spectra calculated in step 2 is D(IG ₁ , IG ₂ ), and the specific calculation method is:

The distance threshold described in step 2 is ε.

Step 3: Take all branch outgoing lines as reference points in turn, and identify the ends of all lines to be tested through Step 1 and Step 2, and then confirm the topology of all branches.

It should be understood that the parts not described in detail in this specification belong to the prior art.

It should be understood that the above description of the preferred embodiments is relatively detailed, and therefore should not be considered as a limitation on the scope of the patent protection of the present invention. In the case of the protection scope, substitutions or deformations can also be made, which all fall within the protection scope of the present invention, and the claimed protection scope of the present invention shall be subject to the appended claims.

Claims (2)

1. a line branch identification method based on current harmonic spectrum is characterized in that: The line branch identification method based on the current harmonic spectrum is applied to a line branch identification device based on the current harmonic spectrum, and the line branch identification device based on the current harmonic spectrum includes: a clamp current transformer, an AD acquisition module , a main processing module, a communication module, and a display module; the clamp current transformer, the AD acquisition module, and the main processing module are connected in series in sequence; the main processing module is respectively connected with the communication module and the display module in sequence; The clamp-shaped current transformer is used to collect the current signal of the reference point or the current signal of the point to be measured; the AD acquisition module is used to perform analog-to-digital conversion on the current signal to obtain the digital current signal of the reference point for on-site measurement or the current signal to be measured on-site. The digital current signal of the measuring point; the main processing module is used to carry out the line branch identification algorithm based on the current harmonic spectrum according to the digital current signal of the on-site measurement reference point or the digital current signal of the on-site measurement point to be measured, and the branch results. display in the display module; the communication module is used for data exchange and communication between the two sets of the line branch identification devices based on the current harmonic spectrum, and between the on-site measurement reference point and the on-site measurement to-be-measured point; the display The module is used to display the recognition result; Step 1: Select the head end of a branch on the outlet side as the reference point, and the end of the line to be measured as the point to be measured, and deploy the line branch identification device based on the current harmonic spectrum at the position of the reference point and the point to be measured, respectively. Collecting the digital current signal or the current signal sampling value sequence of the point to be measured, and further processing by the main processing module to obtain the current harmonic spectrum vectors of the reference point and the point to be measured respectively; Step 2: Calculate the distance between the current harmonic spectrum vector of the reference point and the current harmonic spectrum vector of the point to be measured, when the distance is smaller than the threshold value, it is considered that the point to be measured and the reference point belong to the same branch, otherwise they do not belong to the same branch; Step 3: Take all branch outgoing lines as reference points in turn, and identify the ends of all lines to be tested through Step 1 and Step 2, and then confirm the topology of all branches. 2. the line branch identification method based on current harmonic spectrum according to claim 1 is characterized in that: As described in step 1, the digital current signal or the current signal sampling value sequence of the point to be measured is respectively collected and obtained, specifically: The current signal of the measurement reference point obtained through the synchronous acquisition of the clamp current transformer is: x ₁ (t), and the current signal of the point to be measured is x ₂ (t); The current signal of the measurement reference point and the current signal of the point to be measured are respectively subjected to analog-to-digital conversion by the AD acquisition module, and the current signal sampling value sequence of the reference point is obtained respectively as follows: x ₁ (n), the current signal of the point to be measured is as follows: The sequence of sampled values is x ₂ (n); The main processing module obtains the frequency domain components X ₁ (k) and X ₂ (k) by adopting FFT transformation on the sequences x ₁ (n) and x ₂ (n) respectively; Obtain the current frequency domain component amplitude sequence at the reference point: {x _1n |n=1,2,…N}, and obtain the current frequency domain component phase angle sequence at the reference point: {θ _1n |n=1,2, ...N}; Obtain the current frequency domain component amplitude sequence of the point to be measured: {x _2n |n=1,2,…N}, and obtain the current frequency domain component phase angle sequence of the test point: {θ _2n |n=1, 2,...N}, form two sets of current harmonic spectrum vectors, that is, the current harmonic spectrum vector of the reference point is: IG ₁ , and the current harmonic spectrum vector of the point to be measured is: IG ₂ ; IG ₁ ={(x ₁₁ ,θ ₁₁ ),(x ₁₂ ,θ ₁₂ ),…,(x _1N ,θ _1N )} IG ₂ ={(x ₁₁ ,θ ₁₁ ),(x ₁₂ ,θ ₁₂ ),…,(x _1N ,θ _2N )} In step 2, the distance between the two groups of current harmonic spectra is calculated as D(IG ₁ , IG ₂ ), and the specific calculation method is:

The distance threshold described in step 2 is ε.

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