A method for realizing residual current operated circuit breaker device and topology automatic identification method

Abstract

A method for realizing a residual current operated circuit breaker device and automatic topology identification includes a microprocessor, the microprocessor is connected to a clock circuit, a data storage circuit, a serial port to RS485 communication circuit, a key circuit, a display circuit, a tripping execution circuit, a power conversion circuit, a current and voltage acquisition circuit, and a current detection circuit. A method for identifying the network topology of a residual current operated circuit breaker, the steps include identifying the relationship between households and transformers and identifying branches. The present invention adopts the above design and method, the residual current operated circuit breaker device adopts an integrated design, which greatly reduces the volume of the circuit breaker device, is very convenient to install, reduces the time for configuring the power line, improves the efficiency of configuring the power line, and also reduces the maintenance and repair costs. The acquisition method has high accuracy, which fundamentally solves the problem of unclear area to which the meter belongs due to reasons such as crosstalk in the area and confusion of the relationship between the meters in the area.

Description

Technical field:

[0001] The invention relates to the field of electric power, and in particular to a residual current operated circuit breaker device and a topology automatic identification method. Background technology:

[0002] The residual current operated circuit breaker is a commonly used electrical device, which is mainly used to detect residual current, compare the residual current value with the reference value, and disconnect the main circuit contacts when the residual current value exceeds the reference value. At present, there are some problems with the residual current operated circuit breaker:

[0003] (1) The existing residual current operated circuit breaker is inconvenient to install. According to the electrical installation specifications on the low-voltage distribution network side, each medium- and low-voltage box node needs to be installed with a switch device. The residual current operated circuit breaker has a small installation space in the box. Due to the limited installation position and space, there is no reserved installation line, the installation line is relatively messy, and there are flying wires and broken wires, which poses a serious safety hazard to the entire medium- and low-voltage substation node.

[0004] (2) Existing conventional circuit breaker equipment has a single function, and only has the circuit breaker attribute function and residual current protection function of the residual current circuit breaker, and does not have the corresponding identification, analysis, and transmission functions to realize the substation network topology.

[0005] With the continuous expansion of the system scale, especially the formation of interconnected large power grids, the medium and high voltage transmission network lines have become relatively clear, and the role of medium and high voltage transmission network relationships has been relatively weakened, so the low and medium voltage network topology structure in the power system has become particularly important. Grid interconnection is an objective law of the development of the power industry in various countries and an inevitable trend of power development in various countries in the world. In such a large medium and low voltage area network, the number of nodes is huge, the connections are super complex, the changes are ever-changing, and the real-time requirements are extremely high. As a result, the network topology of the medium and low voltage area is difficult to draw in real time, and manual drawing requires a lot of manpower, and the drawn topology structure is difficult to correspond in real time, and the error is large.

[0006] Existing conventional circuit breakers cannot meet the needs of automatic identification of medium and low voltage power grids; if a low voltage network topology device is installed separately, the two will be installed at the same time, resulting in poor coordination, low integration, high cost and inconvenient maintenance, which will reduce the efficiency of the entire system.

[0007] (3) Even if the existing medium and low voltage area network topology device is integrated into the conventional circuit breaker, the existing medium and low voltage area network topology device still has many disadvantages: At present, the drawing of the network topology of the entire medium and low voltage area is very complicated and is a systematic project. The current implementation methods include partial implementation of the topology device and manual + topology device implementation.

[0008] If the partial implementation of the equipment is adopted, the functions of the topology device are used to check one by one, which has many problems in real-time and accuracy, and cannot achieve accurate results. In addition, the installation of the equipment requires power outage and installation, and the process is very complicated, inefficient, and the results are not ideal;

[0009] If the manual + equipment method is adopted, although the accuracy is improved, the real-time performance is poor. A manual survey takes a long time and cannot correspond to the real-time topological map, so the efficiency is low. Summary of the invention:

[0010] The invention provides a residual current operated circuit breaker device and a topology automatic identification method, which solves the problems existing in the prior art.

[0011] The technical solution adopted by the present invention to solve the above technical problems is:

[0012] A residual current operated circuit breaker device, comprising a microprocessor, wherein the microprocessor is connected to a clock circuit, a data storage circuit, a serial port to RS485 communication circuit, a key circuit, a display circuit, a tripping execution circuit, a power conversion circuit, a current and voltage acquisition circuit, and a current detection circuit;

[0013] The current detection circuit is connected to the current transformer and the drive circuit;

[0014] The power conversion circuit is connected to the broadband carrier communication circuit, and the broadband carrier communication circuit is connected to the current pulse circuit;

[0015] The clock circuit provides a working clock frequency for the microprocessor;

[0016] The data storage circuit is used to store valid data and codes;

[0017] The serial port to RS485 communication circuit is used for data exchange between the microprocessor data and the peripheral device;

[0018] The key circuit is used to set or correct the set parameters and states through manual operation;

[0019] The display circuit is used to display data, parameters and alarm information;

[0020] The tripping execution circuit is used to control the opening and closing states of the tripping device structure according to the instructions of the microprocessor or manual control actions;

[0021] The power conversion circuit is used to convert the on-site three-phase / single-phase power supply into a voltage that can be used by the equipment;

[0022] The current and voltage acquisition circuit is used to collect voltage and current data in the three-phase or single-phase switch output side environment;

[0023] The current detection circuit is used to convert the residual current signal into a voltage signal to obtain a sampling voltage;

[0024] The current pulse circuit is used to emit transient pulse current at the three-phase or single-phase voltage collection terminal;

[0025] The broadband carrier communication circuit is used for broadband carrier communication between devices in the low-voltage area power lines;

[0026] The microprocessor collects voltage information obtained by the current detection circuit, and sends instructions to the trip execution circuit according to the voltage information to control the tripper; at the same time, the current and voltage information obtained by the current and voltage collection circuit are collected to form a physical line correspondence in the low-voltage area.

[0027] The current transformer comprises an iron core and a current modulation circuit. The primary coil or the secondary coil of the current modulation circuit is wound on the iron core. The output end of the current modulation circuit is connected to the current detection circuit.

[0028] The display circuit includes an LCD display circuit and a digital display circuit, and the LCD display circuit and the digital display circuit are connected to a microprocessor;

[0029] The LCD display circuit includes: a backlight control circuit, a frequency control circuit and a low-frequency filter circuit; the backlight control circuit is used to control the LCD display contrast brightness parameter; the frequency control circuit is used to control the flashing frequency of the LCD screen; the low-frequency filter circuit is used to eliminate the crosstalk problem of the low-frequency signal on the display screen signal;

[0030] The digital display circuit comprises a single-digit or multi-digit digital tube group, and the control interface of the digital tube is connected to the A / D interface of the microprocessor.

[0031] A method for realizing automatic topology identification of a residual current operated circuit breaker device comprises the following steps:

[0032] (1) Identification of household change relationships:

[0033] A. Install circuit breakers: Install residual current operated circuit breakers in the distribution cabinet, branch box, and meter box;

[0034] B. The master node sends a command: The current pulse circuit of the residual current operated circuit breaker V set at the master node of the distribution cabinet W sends the broadcast station area identification command of the station area where it is located through the outgoing line side of the distribution cabinet switch. The identification command contains the ID number information and phase information of the distribution terminal;

[0035] C. Receiving instructions from the node: After all the residual current operated circuit breakers of the slave nodes at different levels under the power distribution cabinet W receive the identification instruction information of step B, they automatically save the ID number information and phase information in the identification instruction;

[0036] D. Slave node registration: The residual current operated circuit breaker of the slave node in step C sends a registration message through its broadband carrier communication circuit, and the registration message includes the ID number information and phase information in step C;

[0037] E. Slave node polling: The residual current operated circuit breaker V queries the registration information received in step D, and compares the ID number information and phase information in the registration information. If they are consistent with the identification information in step B, the slave node belongs to the current area. If they are not the same, the slave node does not belong to the current area and is deleted.

[0038] F. Report from the slave node: The residual current operated circuit breaker V of the master node reports the slave node connected to the network after step E to the master station;

[0039] (2) Branch Identification

[0040] G. Select a residual current operated circuit breaker X installed in the meter box, and the residual current operated circuit breaker X generates a branch identification signal on one of the phases. All residual current operated circuit breakers belonging to the branch line receive the branch identification signal. The residual current operated circuit breaker V of the master node can obtain the branch information to which the residual current operated circuit breaker X belongs by collecting the branch information of the circuit breakers that receive the branch identification signal.

[0041] H. The residual current operated circuit breaker set in the meter box performs step G in sequence to obtain the branch information of all residual current operated circuit breakers located in the meter box, and the residual current operated circuit breaker V of the master node reports all branch information to the master station;

[0042] (3) The master station aggregates the household change relationship information obtained in step (1) and the branch information obtained in step (2) to obtain a complete network topology structure.

[0043] The present invention adopts the above design and method, and has the following advantages:

[0044] (1) The residual current operated circuit breaker adopts an integrated design, and each circuit part is reasonably designed, which greatly reduces the size of the circuit breaker and is very convenient to install. It avoids the situation of messy installation lines, flying wires, and broken wires during installation, eliminating safety hazards;

[0045] (2) The circuit breaker attribute function and the residual current protection function are combined with the low-voltage area network topology identification function. When configuring the power, there is no need to install a low-voltage area network topology device separately. The high integration reduces the cost, reduces the power line configuration time, improves the power line configuration efficiency, and also reduces the maintenance and repair costs.

[0046] (3) The low-voltage substation network topology identification function combined with the residual current operated circuit breaker is cleverly designed. The substation network topology structure can be automatically acquired. When the topology in the distribution substation changes, the intelligent distribution transformer terminal can automatically identify the topology structure after the change. This method has high real-time performance and eliminates the need for manual inspections, saving labor costs. This acquisition method is highly accurate and fundamentally solves the problem of unclear substations to which meters belong due to crosstalk in substations and confusion in the relationship between substation meters. Description of the drawings:

[0047] Figure 1 It is a structural block diagram of the present invention;

[0048] Figure 2 It is a circuit principle diagram of the LCD display circuit of the present invention;

[0049] Figure 3 The schematic diagram of the broadband carrier communication circuit of the present invention is shown in FIG. Specific implementation method:

[0050] In order to clearly illustrate the technical features of the present solution, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0051] like Figure 1-3 As shown in, a residual current operated circuit breaker device includes a microprocessor, wherein the microprocessor is connected to a clock circuit, a data storage circuit, a serial port to RS485 communication circuit, a key circuit, a display circuit, a tripping execution circuit, a power conversion circuit, a current and voltage acquisition circuit, and a current detection circuit; the current detection circuit is connected to a current transformer and a drive circuit; the power conversion circuit is connected to a broadband carrier communication circuit, and the broadband carrier communication circuit is connected to a current pulse circuit;

[0052] Clock circuit, providing working clock frequency for microprocessor;

[0053] Data storage circuit, used for storing valid data and codes;

[0054] Serial port to RS485 communication circuit, used for data exchange between microprocessor data and peripherals;

[0055] A key circuit is used to set or correct the set parameters and status through manual operation;

[0056] Display circuit, used to display data, parameters and alarm information;

[0057] The tripping execution circuit is used to control the opening and closing states of the tripping device structure according to the instructions of the microprocessor or the manual control action;

[0058] Power conversion circuit, used to convert on-site three-phase / single-phase power supply into voltage available to the equipment;

[0059] Current and voltage acquisition circuit, used to collect voltage and current data in the outgoing line environment of three-phase or single-phase switch;

[0060] A current detection circuit is used to convert the residual current signal into a voltage signal to obtain a sampling voltage;

[0061] A current pulse circuit is used to emit a transient pulse current at a three-phase or single-phase voltage collection terminal;

[0062] Pulse current is also called pulsating current, which refers to the current with constant direction but constantly changing intensity. Strictly speaking, the current output by a DC generator is pulsating current. It's just that the degree of change in the intensity of this current is very small. Pulse current can also be said to be a unidirectional (cathode) current that is periodically interrupted by a series of open circuits (no current passing). It is different from the commutation current in that the plated part is not used as the anode, but the power supply is intermittently stopped. Due to the intermittent interruption of the current, the cathode potential changes periodically over time. Its waveforms include square waves, sine waves, triangle waves, and sawtooth waves. The wavelet detection method adopted by the present invention can ensure that the signal does not cross the transformer, and can ensure point-to-point communication without dead ends in the substation area, without the need for carrier relay, so all residual current circuit breakers in all meter boxes managed by the transformer can receive the distribution transformer terminal address and phase information broadcast by the substation identification instrument.

[0063] The broadband carrier communication circuit is used for broadband carrier communication between devices in the low-voltage area power lines;

[0064] The broadband carrier communication circuit mainly includes a power line coupling unit, a zero-crossing detection unit, a power line signal modulation part (including a primary bandpass filter, a secondary bandpass filter circuit, and a low-frequency filter circuit), a carrier communication chip SPI level signal circuit, and a carrier communication chip basic circuit (including a clock circuit and a reset circuit). The power coupling unit is the output and input path of the carrier signal, and plays the role of isolating the 220V / 50Hz power frequency. T3 is used as a signal coupling transformer, and the impedance on the power line side is generally 3 to 30Ω. Then the turns ratio or impedance ratio of the primary and secondary coils is determined to be 12 / 21, which can reduce the impedance interference on the power line side to a certain extent; furthermore, the frequency transmitted by the signal coupling transformer T3 is relatively high (100 to 400kHz), which is much greater than the frequency of the power grid; the purpose of isolating high voltage from low voltage is achieved, so that the power carrier signal receiving and transmitting channel is unobstructed, and the high voltage can be isolated. The role of RC in the bandpass filter circuit is to discharge the capacitor when offline to prevent high voltage from appearing at both ends of the device plug. Furthermore, the out-of-band clutter is filtered out and the impedance matching between the front and rear circuits is ensured to ensure the stability and reliability of the power line carrier signal communication again. The zero-crossing detection unit is used to detect the triggering conditions of the power line communication channel; because the interference energy of the peaks and valleys is relatively large in the power carrier transmission, it is necessary to send and receive signals in the zero-point state of the power carrier waveform; after full-wave rectification by two reverse diodes, a pulsating DC waveform is formed, and after resistor voltage division, it is filtered by a capacitor to filter out the high-frequency components and form a voltage waveform at the transistor collector; when the collector voltage is greater than 0.7V, the transistor Q2 is turned on, and a low level is formed at the transistor collector; when the transistor collector voltage is lower than 0.7V, the transistor is turned off, and the transistor collector forms a high level through the pull-up resistor R87. In this way, through the repeated conduction and cutoff of the transistor, a 100Hz pulse waveform is formed at the zero-crossing detection port 15 of the carrier communication chip, and the chip detects the zero point of the power line voltage through judgment.

[0065] Broadband carrier communication uses carriers to transmit analog or digital signals at high speed.

[0066] The microprocessor collects the voltage information obtained by the current detection circuit, and sends instructions to the trip execution circuit according to the voltage information to control the trip device; at the same time, it collects the current and voltage information obtained by the current and voltage collection circuit to form a physical line correspondence in the low-voltage area.

[0067] The current transformer comprises an iron core and a current modulation circuit, a primary coil or a secondary coil of the current modulation circuit is wound on the iron core, and an output end of the current modulation circuit is connected to a current detection circuit.

[0068] The current modulation circuit includes: a comparison amplifier and a sampling resistor; the front end of the sampling resistor is respectively connected to the first end of the secondary coil, the inverting input end of the comparison amplifier and the current detection circuit, and the second end of the sampling resistor is grounded; the output end of the comparison amplifier is connected to the second end of the secondary coil.

[0069] The display circuit includes an LCD display circuit and a digital display circuit, and the LCD display circuit and the digital display circuit are connected to the microprocessor;

[0070] The LCD display circuit includes: a backlight control circuit, a frequency control circuit and a low-frequency filter circuit; the backlight control circuit is used to control the LCD display contrast brightness parameter; the frequency control circuit is used to control the flashing frequency of the LCD screen; the low-frequency filter circuit is used to eliminate the crosstalk problem of the low-frequency signal on the display screen signal;

[0071] The digital display circuit comprises a single-digit or multi-digit digital tube group, and the control interface of the digital tube is connected with the A / D interface of the microprocessor.

[0072] The residual current operated circuit breaker is installed at various nodes in the distribution cabinet, branch cabinet, and meter box. When working, the residual current operated circuit breaker collects current data through the current transformer. When a fault point appears in the line, an unbalanced residual current appears in the current transformer. After the residual current signal passes through the current modulation circuit, the current detection circuit converts the current signal into a voltage signal and obtains the sampled voltage; if the sampled voltage is greater than the voltage threshold data, the tripping circuit is controlled to execute the tripping operation.

[0073] A method for realizing automatic topology identification of a residual current operated circuit breaker device comprises the following steps:

[0074] (1) Identification of household change relationships:

[0075] A. Install circuit breakers: Install residual current operated circuit breakers in the distribution cabinet, branch box, and meter box;

[0076] B. Master node sends command: Based on the broadcast transmission and response mechanism between the microprocessors of the residual current operated circuit breaker, the current pulse circuit of the residual current operated circuit breaker V set at the master node of the distribution cabinet W sends the broadcast station area identification command of the station area where it is located through the outgoing line side of the switch of the distribution cabinet. The identification command contains the ID number information and phase information of the distribution terminal;

[0077] When sending the identification command, it is sent to phase A, phase B, and phase C respectively. It takes 60 seconds to send the signal. In order to ensure that all nodes in the substation area receive the identification command signal, it is sent twice for each phase.

[0078] Due to the non-cross-station characteristics of the current pulse signal, the signal will not be sent to other residual current operated circuit breakers outside the station area;

[0079] C. Receiving instructions from the node: After all the residual current operated circuit breakers set at different levels of the slave nodes under the power distribution cabinet W receive the identification instruction information of step B, the microprocessor will automatically save the ID number information and phase information in the identification instruction, and the information will not be lost even if the power is off;

[0080] D. Slave node registration: In step C, the residual current operated circuit breaker of the slave node sends registration information through its broadband carrier communication circuit. The registration information includes the ID number information and phase information in step C. At this time, the registration information sent by the broadband carrier communication circuit includes all the information automatically saved in step C. The sent registration information is received by the residual current operated circuit breaker V of the master node;

[0081] E. Slave node polling: The residual current operated circuit breaker V queries the registration information received in step D, and compares the ID number information and phase information in the registration information. If they are consistent with the identification information in step B, the slave node belongs to the current area. If they are not the same, the slave node does not belong to the current area and is deleted.

[0082] Since the transmission mechanism of the broadband carrier communication circuit may cause the problem of cross-station area, all the slave nodes registered by the master node in step D may not be the slave nodes of the current station area, so screening is required. According to the ID number information and phase information in the registration information, it can be clearly determined whether the slave node is a slave node in the current station area.

[0083] F. Report from the slave node: The residual current operated circuit breaker V of the master node reports the slave node connected to the network after step E to the master station;

[0084] (2) Branch Identification

[0085] G. Select a residual current operated circuit breaker X installed in the meter box, and the residual current operated circuit breaker X generates a branch identification signal on one of the phases. All residual current operated circuit breakers belonging to the branch line receive the branch identification signal. The residual current operated circuit breaker V of the master node can obtain the branch information to which the residual current operated circuit breaker X belongs by collecting the branch information of the circuit breakers that receive the branch identification signal.

[0086] Based on the KCL current total loop conservation theorem, that is, when a load current is generated on a phase of the terminal device, all branch lines supplying power to the meter box will increase an equivalent current, while the current of other branch lines will not change. Therefore, through step G, it can be obtained which nodes are included in the branch where the residual current operated circuit breaker X is located.

[0087] H. The residual current operated circuit breaker set in the meter box performs step G in sequence to obtain the branch information of all residual current operated circuit breakers located in the meter box, and the residual current operated circuit breaker V of the master node reports all branch information to the master station;

[0088] After the branch information of all residual current operated circuit breakers located in the meter box is obtained, the main node will perform inference calculations based on the branch intersection conditions of each residual current operated circuit breaker to obtain a complete branch structure and hierarchical structure.

[0089] (3) The master station aggregates the household change relationship information obtained in step (1) and the branch information obtained in step (2) to obtain a complete network topology structure.

[0090] The above specific implementation manner cannot be used as a limitation on the protection scope of the present invention. For those skilled in the art, any substitution, improvement or change made to the implementation manner of the present invention falls within the protection scope of the present invention.

[0091] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A residual current operated circuit breaker device, characterized in that: It includes a microprocessor, and the microprocessor is connected with a clock circuit, a data storage circuit, a serial port to RS485 communication circuit, a key circuit, a display circuit, a tripping execution circuit, a power conversion circuit, a current and voltage acquisition circuit, and a current detection circuit; The current detection circuit is connected to the current transformer and the drive circuit; The power conversion circuit is connected to the broadband carrier communication circuit, and the broadband carrier communication circuit is connected to the current pulse circuit; The clock circuit provides a working clock frequency for the microprocessor; The data storage circuit is used to store valid data and codes; The serial port to RS485 communication circuit is used for data exchange between the microprocessor data and the peripheral device; The key circuit is used to set or correct the set parameters and states through manual operation; The display circuit is used to display data, parameters and alarm information; The tripping execution circuit is used to control the opening and closing states of the tripping device structure according to the instructions of the microprocessor or manual control actions; The power conversion circuit is used to convert the on-site three-phase / single-phase power supply into a voltage that can be used by the equipment; The current and voltage acquisition circuit is used to collect voltage and current data in the three-phase or single-phase switch output side environment; The current detection circuit is used to convert the residual current signal into a voltage signal to obtain a sampling voltage; The current pulse circuit is used to emit transient pulse current at the three-phase or single-phase voltage collection terminal; The broadband carrier communication circuit is used for broadband carrier communication between devices in the low-voltage area power lines; The microprocessor collects voltage information obtained by the current detection circuit, and sends instructions to the trip execution circuit according to the voltage information to control the trip device; at the same time, the current and voltage information obtained by the current and voltage collection circuit are collected to form a physical line correspondence in the low-voltage area; The current transformer comprises an iron core and a current modulation circuit, wherein the current modulation circuit is used to adjust the current, the primary coil or the secondary coil of the current modulation circuit is wound on the iron core, and the output end of the current modulation circuit is connected to the current detection circuit; The display circuit includes an LCD display circuit and a digital display circuit, and the LCD display circuit and the digital display circuit are connected to a microprocessor; The LCD display circuit includes: a backlight control circuit, a frequency control circuit and a low-frequency filter circuit; the backlight control circuit is used to control the LCD display contrast brightness parameter; the frequency control circuit is used to control the flashing frequency of the LCD screen; the low-frequency filter circuit is used to eliminate the crosstalk problem of the low-frequency signal on the display screen signal; The digital display circuit comprises a single-digit or multi-digit digital tube group, and the control interface of the digital tube is connected to the A / D interface of the microprocessor.

2. A method for realizing automatic topology identification of a residual current operated circuit breaker device as claimed in claim 1, comprising: (1) Identification of household change relationships: A. Install circuit breakers: Install residual current operated circuit breakers in the distribution cabinet, branch box, and meter box; B. The master node sends a command: The current pulse circuit of the residual current operated circuit breaker V set at the master node of the distribution cabinet W sends the broadcast station area identification command of the station area where it is located through the outgoing line side of the distribution cabinet switch. The identification command contains the ID number information and phase information of the distribution terminal; C. Receiving instructions from the node: After all the residual current operated circuit breakers of the slave nodes at different levels under the power distribution cabinet W receive the identification instruction information of step B, they automatically save the ID number information and phase information in the identification instruction; D. Slave node registration: The residual current operated circuit breaker of the slave node in step C sends a registration message through its broadband carrier communication circuit, and the registration message includes the ID number information and phase information in step C; E. Slave node polling: The residual current operated circuit breaker V queries the registration information received in step D, and compares the ID number information and phase information in the registration information. If they are consistent with the identification information in step B, the slave node belongs to the current area. If they are not the same, the slave node does not belong to the current area and is deleted. F. Report from the slave node: The residual current operated circuit breaker V of the master node reports the slave node connected to the network after step E to the master station; (2) Branch identification G. Select a residual current operated circuit breaker X installed in the meter box, and the residual current operated circuit breaker X generates a branch identification signal on one of the phases. All residual current operated circuit breakers belonging to the branch line receive the branch identification signal. The residual current operated circuit breaker V of the master node can obtain the branch information to which the residual current operated circuit breaker X belongs by collecting the branch information of the circuit breakers that receive the branch identification signal. H. The residual current operated circuit breaker set in the meter box performs step G in sequence to obtain the branch information of all residual current operated circuit breakers located in the meter box, and the residual current operated circuit breaker V of the master node reports all branch information to the master station; (3) The master station aggregates the household change relationship information obtained in step (1) and the branch information obtained in step (2) to obtain a complete network topology structure.

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