Single-phase grounding fault line selection device for small-current grounding system

Abstract

The utility model discloses a single-phase earth fault line selection device for a small current grounding system, and belongs to the technical field of single-phase earth fault detection of an electric power system. Comprising a PT / CT analog input module, a signal conditioning module, a data acquisition module and a data processing and control module which are connected in sequence, the data acquisition module is further connected with a data buffer module, and the data processing and control module is further connected with a data storage module, a display module, an alarm module and a communication module; the signal conditioning module comprises a signal voltage regulating circuit and a signal filtering circuit, the data acquisition module is formed by connecting two A / D converters with an FPGA chip, and whether a single-phase earth fault occurs or not is judged by monitoring a zero-sequence voltage at a bus through the FPGA chip; the data processing and control module adopts an STM32 single-chip microcomputer to carry out data processing and analysis to select a fault line. According to the utility model, an FPGA + STM32 dual-core structure is adopted to replace a conventional single processing structure, so that faults can be rapidly detected, and fault lines can be accurately judged.

Description

Technical Field

[0001] This utility model belongs to the field of single-phase grounding fault detection technology in power systems, and specifically relates to a single-phase grounding fault selection device for low-current grounding systems. Background Technology

[0002] In my country, medium-voltage distribution networks ranging from 6kV to 35kV typically employ a neutral point non-effective grounding operation mode. This can be broadly categorized into ungrounded neutral point systems, neutral point grounded via an arc suppression coil, and neutral point grounded via high resistance. The design characteristic of this mode is that when a single-phase ground fault occurs, the phase voltage of the faulty phase becomes zero, while the phase voltage of the non-faulty phase rises to the line voltage. The three-phase line voltages remain symmetrical, allowing the system to operate with the fault for 1-2 hours. However, prolonged grounding operation can easily lead to two- or three-phase open circuits, causing equipment damage.

[0003] Currently, when a single-phase ground fault occurs in a low-current grounding system, the ground fault current is relatively small. The zero-sequence current of each line is affected by the distribution network structure and parameters, the neutral point grounding method, and the transition resistance during grounding. It is difficult for a low-current ground fault location device based on a single discrimination principle to accurately locate the fault in a resonant grounding system.

[0004] Therefore, there is an urgent need to design a single-phase grounding fault location device that can accurately detect phase-to-ground faults in low-current grounding systems. Utility Model Content

[0005] The purpose of this invention is to solve the problem of low detection accuracy of existing low-current grounding fault location devices, and to provide a single-phase grounding fault location device for low-current grounding systems that can quickly detect faults and accurately determine the faulty line.

[0006] To achieve the above objectives, this utility model adopts the following technical solution: A single-phase grounding fault selection device for a low-current grounding system, comprising a PT / CT analog input module, a signal conditioning module, a data acquisition module, and a data processing and control module connected in sequence. The data acquisition module is further connected to a data buffer module, and the data processing and control module is further connected to a data storage module, a display module, an alarm module, and a communication module. All modules except the PT / CT analog input module are powered by a power supply module. The PT / CT analog input module includes two analog signals, zero-sequence voltage and zero-sequence current, connected to the busbar. The signal conditioning module includes a signal voltage regulation circuit and a signal filtering circuit. The input terminal of the signal conditioning module is connected to the PT / CT analog input module to regulate and filter the received analog signals. The signal voltage regulation circuit includes a voltage transformer and a current transformer, and the signal filtering circuit uses a Butterworth low-pass filter. The system includes two resistors, two capacitors, and one operational amplifier. The data acquisition module consists of two A / D converters connected to an FPGA chip. The input of the data acquisition module is connected to the output of the signal conditioning module, converting the received, regulated, and filtered analog signal into a digital signal. The FPGA chip monitors the zero-sequence voltage at the bus to determine if a single-phase ground fault has occurred. The data buffer module stores data before and after the fault. The input of the data processing and control module is connected to the output of the data acquisition module to receive the fault signal. The data processing and control module uses an STM32 microcontroller for data processing and analysis, and the STM32 microcontroller transmits data to the FPGA chip via the FSMC communication protocol. The data processing and control module analyzes and processes the data (before and after the fault) stored in the data buffer module to select the faulty line. The data storage module is connected to the data processing and control module to store fault data for each fault occurrence.

[0007] Furthermore, in the data acquisition module, the FPGA chip monitors the zero-sequence voltage at the bus with a set threshold between 30V and 50V, and when the zero-sequence voltage at the bus exceeds the set threshold, it is determined that a single-phase grounding fault has occurred.

[0008] Furthermore, in the signal voltage regulation circuit, the voltage transformer is model TR1102-1C, the current transformer is model TR1102-2C, and the turns ratios of the voltage transformer and the current transformer are 220:5V and 5A:5V, respectively.

[0009] Furthermore, in the signal filtering circuit, the Butterworth low-pass filter used has a cutoff frequency of 4KHz, both resistors are 4K resistors, both capacitors are 0.01uf capacitors, and the operational amplifier is an LM324.

[0010] Furthermore, in the data acquisition module, both A / D converters are model AD7606, and the FPGA chip is model EP4CE10F17C8N.

[0011] Furthermore, the display module adopts the Kunlun Tongtai TPC7022EX touch screen. The display module receives control signals from the data processing and control module and displays the three-phase voltage and zero-sequence voltage values ​​at the bus, the status of each feeder, and the time of occurrence and end of the fault in real time. When the display module receives fault information, it displays the fault line number, and the indicator light of the corresponding fault line on the display page turns red.

[0012] Furthermore, the alarm module adopts a SIM900A GSM module. When a single-phase ground fault occurs, the data processing and control module sends fault information to the alarm module. The alarm module receives the alarm signal from the data processing and control module and sends the fault information to the staff in the form of SMS through the communication module.

[0013] Furthermore, the power module has an input voltage of 24V and output voltages of 15V, 5V, and 3.3V.

[0014] The beneficial effects of this utility model are: the device of this utility model adopts an FPGA+STM32 dual-core structure, replacing the previous single processing structure, which can quickly detect faults and accurately determine the faulty circuit. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the module connection of the fault selection device of this utility model;

[0016] Figure 2 This is a circuit connection diagram of the signal filtering circuit in the fault location device of this utility model;

[0017] Figure 3 This is a schematic diagram of the connection between the fault location device of this utility model and the power distribution network. Detailed Implementation

[0018] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0019] Example: Figure 1As shown, this utility model provides a single-phase grounding fault selection device for a low-current grounding system, including a PT / CT analog input module, a signal conditioning module, a data acquisition module, and a data processing and control module connected in sequence. The data acquisition module is also connected to a data buffer module, and the data processing and control module is also connected to a data storage module, a display module, an alarm module, and a communication module. Except for the PT / CT analog input module, all other modules are powered by a power supply module. The power supply module has an input voltage of 24V and output voltages of 15V, 5V, and 3.3V.

[0020] The PT / CT analog input module includes two analog signals, zero-sequence voltage and zero-sequence current, connected to the bus.

[0021] The signal conditioning module includes a signal voltage regulation circuit and a signal filtering circuit. The input terminal of the signal conditioning module is connected to the PT / CT analog input module to regulate and filter the received analog signal, converting the voltage and current signals into a range acceptable to the data acquisition module. The signal voltage regulation circuit includes a voltage transformer and a current transformer. The voltage transformer is model TR1102-1C, and the current transformer is model TR1102-2C. The turns ratios of the voltage transformer and the current transformer are 220:5V and 5A:5V, respectively.

[0022] The signal filtering circuit uses a Butterworth low-pass filter with a cutoff frequency of 4kHz; the filtering circuit is as follows: Figure 2 As shown, the filter circuit includes two 4K resistors, two 0.01uf capacitors, and an LM324 op-amp.

[0023] The data acquisition module consists of two A / D converters connected to an FPGA chip. Both A / D converters are model AD7606, and the FPGA chip is model EP4CE10F17C8N. The data acquisition module controls the ADC7606 through the FPGA to acquire data. The input terminal of the data acquisition module is connected to the output terminal of the signal conditioning module, converting the received regulated and filtered analog signal into a digital signal and storing it in the memory space built inside the FPGA, storing the data of the 20 cycles before the fault. The FPGA chip monitors the zero-sequence voltage at the bus to determine whether a single-phase ground fault has occurred. The set threshold for the zero-sequence voltage at the bus is between 30V and 50V. When the zero-sequence voltage at the bus exceeds the set threshold, a single-phase ground fault is determined to have occurred.

[0024] The data buffer module caches data before and after the fault occurred, and caches data from the previous 20 cycles at the current moment, for the data processing and control module to perform data analysis and processing.

[0025] The input terminal of the data processing and control module is connected to the output terminal of the data acquisition module to receive fault signals. The data processing and control module uses an STM32 microcontroller for data processing and analysis. The STM32 microcontroller transmits data to the FPGA chip through the FSMC communication protocol. The data processing and control module reads the pre-fault data and post-fault data cached by the data buffer module, analyzes and processes the data, and selects the faulty line.

[0026] The data storage module is connected to the data processing and control module to store fault data for each fault, and can store data information for 200 permanent single-phase grounding faults.

[0027] The display module uses the Kunlun Tongtai TPC7022EX touch screen. The display module receives control signals from the data processing and control module and displays the three-phase voltage and zero-sequence voltage values ​​at the bus, the status of each feeder, and the time of occurrence and end of the fault in real time. When the display module receives fault information, it displays the fault line number, and the indicator light of the corresponding fault line on the display page turns red.

[0028] The alarm module uses a SIM900A GSM module. When a single-phase ground fault occurs, the data processing and control module sends the fault information to the alarm module. The alarm module receives the alarm signal from the data processing and control module and sends the fault information to the staff via SMS through the communication module.

[0029] The communication module primarily uses serial communication and RS485 (using the SP485 chip) for communication. The STM32 transmits fault information to the display module via RS485 communication, and the display module shows the fault information. The SIM900A GSM module interacts with the STM32 through its built-in serial port. In the event of a single-phase ground fault, the STM32 controls the SIM900A GSM module to send fault information to staff via SMS.

[0030] like Figure 3 The diagram shows the connection between the fault location device and the distribution network. In the diagram, BUS is the distribution network bus, L1, L2, L3, and L4 are four outgoing lines of the distribution network, PT is a zero-sequence voltage transformer, and CT is a zero-sequence current transformer. The fault location device is connected to the distribution network through the zero-sequence current transformer and the zero-sequence voltage transformer respectively, collecting zero-sequence voltage and current signals. The single-phase ground fault location device for low-current systems continuously monitors the zero-sequence voltage at the bus to determine whether a single-phase ground fault has occurred. Once a fault occurs, the device automatically activates its fault location function to select the faulty line.

[0031] This utility model device adopts an FPGA+STM32 dual-core structure, replacing the previous single processing structure, which can quickly detect faults and accurately identify faulty circuits.

[0032] The above description is only used to illustrate the technical solution of this utility model and is not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of this utility model, as long as they do not depart from the spirit and scope of the technical solution of this utility model, should be covered within the scope of the claims of this utility model.

Claims

1. A single-phase grounding fault location device for a low-current grounding system, characterized in that: It includes a PT / CT analog input module, a signal conditioning module, a data acquisition module, and a data processing and control module connected in sequence. The data acquisition module is also connected to a data buffer module, and the data processing and control module is also connected to a data storage module, a display module, an alarm module, and a communication module. Except for the PT / CT analog input module, all other modules are powered by a power supply module. The PT / CT analog input module includes two analog signals, zero-sequence voltage and zero-sequence current, connected to the busbar. The signal conditioning module includes a signal voltage regulation circuit and a signal filtering circuit. The input terminal of the signal conditioning module is connected to the PT / CT analog input module to regulate and filter the received analog signal. The signal voltage regulation circuit includes a voltage transformer and a current transformer. The signal filtering circuit adopts a Butterworth low-pass filter and includes two resistors, two capacitors and an operational amplifier. The data acquisition module consists of two A / D converters connected to an FPGA chip. The input end of the data acquisition module is connected to the output end of the signal conditioning module to convert the received voltage-regulated and filtered analog signal into a digital signal. The FPGA chip monitors the zero-sequence voltage at the bus to determine whether a single-phase grounding fault has occurred. The data buffer module caches data before and after the fault occurs. The input terminal of the data processing and control module is connected to the output terminal of the data acquisition module to receive fault signals. The data processing and control module uses an STM32 microcontroller for data processing and analysis, and the STM32 microcontroller transmits data to the FPGA chip through the FSMC communication protocol. The data processing and control module reads the pre-fault data and post-fault data cached by the data buffer module, analyzes and processes the data, and selects the faulty line. The data storage module is connected to the data processing and control module and stores the fault data each time a fault occurs.

2. A single-phase grounding fault location device for a low-current grounding system according to claim 1, characterized in that: In the data acquisition module, the FPGA chip monitors the zero-sequence voltage at the busbar with a set threshold of 30V~50V, and determines that a single-phase grounding fault has occurred when the zero-sequence voltage at the busbar exceeds the set threshold.

3. A single-phase grounding fault location device for a low-current grounding system according to claim 1, characterized in that: In the signal voltage regulation circuit, the voltage transformer is model TR1102-1C, the current transformer is model TR1102-2C, and the turns ratios of the voltage transformer and the current transformer are 220:5V and 5A:5V, respectively.

4. A single-phase grounding fault location device for a low-current grounding system according to claim 1, characterized in that: The signal filtering circuit uses a Butterworth low-pass filter with a cutoff frequency of 4kHz, two 4K resistors, two 0.01uf capacitors, and an LM324 operational amplifier.

5. A single-phase grounding fault location device for a low-current grounding system according to claim 1, characterized in that: In the data acquisition module, both A / D converters are model AD7606, and the FPGA chip is model EP4CE10F17C8N.

6. A single-phase grounding fault location device for a low-current grounding system according to claim 1, characterized in that: The display module adopts Kunlun Tongtai TPC7022EX touch screen. The display module receives control signals from the data processing and control module and displays the three-phase voltage and zero-sequence voltage values ​​at the bus, the status of each feeder, and the time of occurrence and end of the fault in real time. When the display module receives fault information, it displays the faulty line number, and the indicator light for the corresponding faulty line on the display page turns red.

7. A single-phase grounding fault location device for a low-current grounding system according to claim 1, characterized in that: The alarm module uses a SIM900A GSM module. When a single-phase ground fault occurs, the data processing and control module sends the fault information to the alarm module. The alarm module receives the alarm signal from the data processing and control module and sends the fault information to the staff via SMS through the communication module.

8. A single-phase grounding fault location device for a low-current grounding system according to claim 1, characterized in that: The power module has an input voltage of 24V and output voltages of 15V, 5V, and 3.3V.

Images