High-precision online monitoring system for leakage current of zinc oxide arrester

Abstract

The utility model discloses a high-precision online monitoring system for leakage current of a zinc oxide arrester, which relates to the field of online monitoring of power equipment and comprises a signal acquisition module, an A / D analog-to-digital conversion module, a communication module, an upper computer central processing unit and a display module. The signal acquisition module is used for acquiring voltage and current signals, and the voltage and current signals are converted into digital sampling data signals through the A / D analog-to-digital conversion module; the communication module is used for transmitting the original voltage and current digital sampling data signal to the upper computer central processing unit; and the upper computer central processing unit is used for processing the signal harmonic wave of the current, displaying the result on the display module and giving out the aging degree of the lightning arrester. According to the utility model, the actual operation state of the zinc oxide lightning arrester of the transformer substation can be monitored in real time, and a user can obtain the state data of the lightning arrester by outputting the man-machine interaction interface, thereby further removing faults and improving the operation safety and efficiency of a power grid.

Description

Technical Field

[0001] The utility model relates to the technical field of online monitoring of electric power equipment, in particular to a high-precision online monitoring system for leakage current of zinc oxide lightning arresters. Background Art

[0002] Aging will cause the nonlinear characteristics of zinc oxide valve plates to deteriorate, resulting in a significant increase in the high-order harmonic components of the resistive current. The high-order harmonic components of the MOA resistive leakage current are the basis for judging the aging status of metal oxide valve plates. Operation and maintenance personnel need to get close to the line under test and use the secondary side voltage method. At the test site, a large number of test lines are prone to accidental dragging, and there is a short circuit hazard on the secondary side. In addition, temporary detection wiring has poor contact and long-distance wireless signal instability, which reduces the efficiency of equipment detection. Therefore, it is necessary to propose an online detection method and system for lightning arresters to accurately judge the insulation status of lightning arresters and improve the efficiency and safety of power equipment inspections.

[0003] Metal oxide arresters are widely used in transmission and distribution networks. Affected by harsh environments such as high temperature and high humidity and the years of operation, arresters have prominent problems such as moisture and aging. At present, most domestic and foreign projects use the traditional method of regular preventive testing to conduct safety assessments on the health of metal oxide arresters. The aging of metal oxide valve plates will cause their nonlinear characteristics to deteriorate, resulting in a significant increase in the high-order harmonic components of the resistive current. The high-order harmonic components of the MOA resistive leakage current are the basis for judging the aging of metal oxide valve plates. Operation and maintenance personnel need to use the secondary side voltage method close to the line under test. At the test site, more test lines are very likely to cause accidental dragging, and there are short-circuit risks on the secondary side. In addition, temporary detection wiring has poor contact and unstable long-distance wireless signals, which reduces the efficiency of equipment detection. Therefore, it is necessary to propose an online detection method and system for arresters to accurately judge the insulation state of arresters and improve the efficiency and safety of power equipment inspections. Utility Model Content

[0004] The utility model aims to provide a high-precision zinc oxide arrester leakage current online monitoring system to solve the problems raised in the above-mentioned background technology.

[0005] In order to solve the above technical problems, the utility model provides the following technical solutions: a high-precision zinc oxide arrester leakage current online monitoring system, including a signal acquisition module, an A / D analog-to-digital conversion module, a communication module, a host computer central processing unit and a display module;

[0006] The signal acquisition module is used to collect voltage and current signals, and the voltage and current signals are converted into digital sampling data signals through the A / D analog-to-digital conversion module;

[0007] The communication module is used to transmit the original voltage and current digital sampling data signal to the host computer central processor; the host computer central processor is used to process the signal harmonics of the current, display the results on the display module, and give the aging degree of the lightning arrester.

[0008] Preferably, the signal acquisition module includes voltage and current signal acquisition devices, the voltage signal acquisition device adopts a voltage transformer; the current signal acquisition device adopts a zinc oxide valve plate current transformer; the total leakage current is detected by the zinc oxide valve plate current transformer, which is used to measure the ground capacitance current of the total leakage current of the lightning arrester.

[0009] Preferably, the current transformer is connected to the A / D analog-to-digital conversion module via a filtering circuit, and the voltage transformer is connected to the A / D analog-to-digital conversion module via a filtering circuit. The A / D analog-to-digital conversion module uses a high-precision ADS8556 chip and is connected to the communication module using a parallel interface transmission mode.

[0010] Preferably, the communication module is a ZigBee communication module, the main control chip is connected to the ZigBee module via the MCU serial port, and the signal communication module transmits the sensor voltage and current signals to the signal processing module.

[0011] Preferably, the host computer central processor includes a signal processing module, and the communication module transmits the sensor voltage and current signals to the signal processing module. The signal processing module uses a 150MHz frequency, 256KB flash memory, 32-bit TMS320F2812 DSP main control chip to process the voltage and current sampling signals. The signal processing module also includes a power supply circuit, a clock circuit with internal oscillation of a quartz crystal, an RC reset circuit, and a JTAG interface circuit to burn and simulate the internal flash of the DSP.

[0012] Preferably, the host computer central processor MCU adopts the TMS320F2812 DSP main control chip. The harmonic analysis of the current signal can adopt the very mature DSP microprocessor technology to perform Fourier transform harmonic analysis, introduce the third harmonic of the bus voltage and the amplitude of the fundamental component for comparison, analysis and processing, and avoid the interference of the harmonic component in the working voltage on the extraction of resistive leakage current. The intelligent diagnosis system can reduce the number of power outage tests, ensure the safe production of the power transmission and distribution system and the personal safety of operation and maintenance personnel. The host computer output module of the host computer central processor counts, analyzes, and calculates, intuitively understands the changing trend of data within a certain period of time, displays the leakage current calculation results and gives the aging degree of the lightning arrester.

[0013] Compared with the prior art, the beneficial effects of the utility model are:

[0014] The utility model can monitor the actual operating status of the zinc oxide lightning arrester in the substation in real time. The user can obtain the lightning arrester status data by outputting the human-computer interaction interface, further troubleshooting, and improving the safety and efficiency of power grid operation. No external power supply is required, and real-time online passive wireless monitoring and on-site display functions of the lightning arrester operating status are provided. The host adopts a low-power embedded DSP chip designed with standard industrial specifications to ensure that the system is stable and reliable. Real-time monitoring of lightning arrester leakage current data, unified management of on-site equipment, eliminating the tedious work of staff to patrol the site, and staff can grasp the aging information of zinc oxide lightning arresters in the monitoring room. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the monitoring system of the utility model;

[0016] Figure 2 This is a visualized block diagram of the ADS8556 chip of the utility model;

[0017] Figure 3 This is the connection diagram of ADS8556 and TMS320F2812 DSP of the utility model. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0019] like Figure 1-3 As shown in , this embodiment provides a high-precision zinc oxide arrester leakage current online monitoring system, including a terminal measurement system and a host computer system; wherein the terminal measurement system includes a signal acquisition module and a communication module, and the communication module is a ZigBee communication module.

[0020] The host computer central processing unit includes a microprocessor signal processing module and a host computer output module.

[0021] The signal acquisition device includes a current signal acquisition and voltage zero-crossing detection module, using a current transformer and a voltage transformer. The current signal acquisition device is a zinc oxide valve plate current transformer. The full leakage current is detected by the zinc oxide valve plate current transformer, and is used to measure the capacitive current to ground of the full leakage current of the arrester. The current transformer is connected to the A / D analog-to-digital conversion module through a filter circuit, and the voltage transformer is connected to the A / D analog-to-digital conversion module through a filter circuit. The A / D analog-to-digital conversion module selects a high-precision ADS8556 chip, adopts a 16-bit parallel interface transmission mode, and is connected to the ZigBee module serial port through a 16-bit data bus. The analog-to-digital conversion module is configured to convert the collected analog sampling data signal into a digital sampling data signal. The external analog signal is converted into a digital signal that can be recognized by the data communication module MCU, such as Figure 2 As shown in Figure 1. The chip generates an internal clock, each conversion requires 18.5 clock cycles, and the conversion clock has a duty cycle of 50%. Figure 2 As shown, the system uses three ADCs in the chip to sample three-phase voltage, and another three ADCs to sample three-phase current. The three-phase voltage sampling and three-phase current sampling are analyzed and calculated by the digital signal processing circuit of the chip, and the three-phase arrester total leakage current effective value, the three-phase bus voltage effective value and the resistive leakage current fundamental component are output.

[0022] The ZigBee communication module includes a current transformer terminal node, a voltage transformer terminal node, a ZigBee router and a coordinator. ZigBee is a wireless connection with low power consumption. It can operate in the 2.4GHz frequency band, has a maximum transmission rate of 250kbit / s, and a transmission distance of up to 50 meters. The Zigbee networking and router based on the IPv6 communication protocol are responsible for connecting to the central network and relaying data; all Zigbee routers form a cellular mesh network, which is connected to the Zigbee aggregation node, which is set at the main service station to build a complete wireless network structure.

[0023] The microprocessor signal processing module includes a power supply circuit, a clock circuit with a quartz crystal internal oscillation, an RC reset circuit, and a JTAG interface circuit to burn and simulate the DSP internal flash. The host computer central processor uses a 150MHz frequency, 256KB flash memory, 32-bit MCU: TMS320F2812 DSP main control chip to process voltage and current sampling signals.

[0024] Using ZigBee transmission protocol, the main control chip is connected to the ZigBee module through the MCU serial port. The signal communication module transmits the sensor voltage and current signals to the signal processing module. The harmonic analysis of the current signal of the host computer central processor TMS320F2812 DSP main control chip can use the very mature DSP microprocessor technology to perform Fourier transform harmonic analysis, introduce the bus voltage third harmonic and fundamental component amplitude for comparison, analysis and processing, and avoid the harmonic component in the working voltage from interfering with the resistive leakage current extraction. This intelligent diagnostic system can reduce the number of power outage tests, ensure the safe production of the power transmission and distribution system and the personal safety of operation and maintenance personnel. The host computer output module, statistics, analysis, calculation, intuitive understanding of the data change trend over a period of time, display the leakage current calculation results and give the aging degree of the arrester.

[0025] The communication module transmits the original voltage and current digital signals to the microprocessor signal processing module. Figure 3 As shown, the 16-bit data line of ADS8556 is connected to the 16-bit data line of TMS320F2812 DSP to process the raw data. The data signal processor uses the MCUTMS320F2812 DSP main control chip with a frequency of 150MHz, 256KB flash memory, and 32 bits. The on-chip oscillator and watchdog timer module are enabled, and the low-power mode is adopted to save energy. A 32MHz external crystal oscillator is used, and the PLL phase-locked loop multiplication is used. The PLL control register value is set to 10, so the system clock is 160MHz. This is actually an overclocked state (the maximum operating frequency of 2812 is 150). The subsequent acquisition frequency is accurately set to ensure full-cycle sampling.

[0026] DSP performs Fourier transform to calculate the fundamental component of resistive leakage current and transmits the calculation result to the output module. The touch screen provides data display and user operation functions to output the aging status of the lightning arrester and perform corresponding operations. The microprocessor and output module are encapsulated in the online monitoring acquisition box.

[0027] In this embodiment, the signal acquisition uses the current signal of the current transformer on the same bus as the arrester as the reference phase signal for the arrester resistive current test, and the signal angle is rotated 90° clockwise to obtain the arrester operating voltage signal angle. Figure 1 From the equivalent circuit of the metal oxide arrester, we know that the MOA is composed of a nonlinear resistor R and a capacitor C in parallel, so the total leakage current is composed of:

[0028] i=i R +i C (1)

[0029] Where: i Ris the resistive current flowing through the nonlinear resistor when a voltage is applied across the MOA, i.e., the resistive leakage current. C is the capacitive leakage current and i is the total leakage current.

[0030] As the MOA ages, its nonlinear characteristics deteriorate, which is mainly reflected in the increase of resistive current. At present, it is generally calculated using formula (2):

[0031] i R = k·u α (2)

[0032] Where: α and k are constants. α is the operating voltage of MOA.

[0033] The relationship between constants α and k and resistive current is: when the α value does not change, as the k value gradually increases, the MOA resistive current also tends to increase; when the k value does not change, as the α value decreases, the resistive current tends to increase. Therefore, the nonlinear coefficient α and k value can be used to judge the aging of MOA.

[0034] Capacitive current i of zinc oxide arrester C It is related to its own capacitance C. As the MOA ages, its own capacitance tends to increase. Therefore, this paper intends to use the MOA's own capacitance to reflect its aging. When a certain voltage is applied across the MOA, the capacitive component of the generated leakage current can be expressed by formula (3):

[0035]

[0036] The leakage current is expressed as

[0037]

[0038] According to the system bus voltage, the capacitive current of the arrester is calculated, and the resistive leakage current is the difference between the total current and the capacitive current. If it is damp or aged, the resistive current will increase and the loss will increase. According to the increase in resistive current, the aging degree of zinc oxide arrester can be determined.

[0039] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-precision zinc oxide arrester leakage current online monitoring system, characterized in that: It includes signal acquisition module, A / D analog-to-digital conversion module, communication module, host computer central processing unit and display module; The signal acquisition module is used to collect voltage and current signals, which are converted into digital sampling data signals by the A / D analog-to-digital conversion module; The communication module is used to transmit the original voltage and current digital sampling data signals to the host computer central processing unit; The host computer central processing unit is used to process the signal harmonics of the current, display the results on the display module, and give the aging degree of the lightning arrester.

2. A high-precision zinc oxide arrester leakage current online monitoring system according to claim 1, characterized in that: The signal acquisition module includes voltage and current signal acquisition devices, and the voltage signal acquisition device adopts a voltage transformer; The current signal acquisition device is a zinc oxide valve plate current transformer; The total leakage current is detected by a zinc oxide valve plate current transformer and is used to measure the capacitive current to ground of the total leakage current of the arrester.

3. A high-precision zinc oxide arrester leakage current online monitoring system according to claim 2, characterized in that: The current transformer is connected to the A / D analog-to-digital conversion module via a filter circuit, and the voltage transformer is connected to the A / D analog-to-digital conversion module via a filter circuit.

4. A high-precision zinc oxide arrester leakage current online monitoring system according to claim 1 or 2, characterized in that: The communication module is a ZigBee communication module.

5. A high-precision zinc oxide arrester leakage current online monitoring system according to claim 4, characterized in that: The host computer central processing unit includes a signal processing module, and the communication module transmits the sensor voltage and current signals to the signal processing module.

6. A high-precision zinc oxide arrester leakage current online monitoring system according to claim 5, characterized in that: The signal processing module uses a 150MHz frequency, 256KB flash memory, 32-bit TMS320F2812 DSP main control chip to process voltage and current sampling signals.

7. A high-precision zinc oxide arrester leakage current online monitoring system according to claim 6, characterized in that: The signal processing module also includes a power supply circuit, a clock circuit with internal quartz crystal oscillation, an RC reset circuit, and a JTAG interface circuit to perform programming and simulation testing on the internal flash of the DSP.

8. A high-precision zinc oxide arrester leakage current online monitoring system according to claim 1, characterized in that: The signal acquisition module uses the current signal of the current transformer on the same bus as the arrester as the reference phase signal during the resistive current test of the arrester.

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