Low-current line selection device with perfect resonance overvoltage tripping logic function

Abstract

The invention discloses a low-current line selection device with a function of perfecting resonance overvoltage tripping logic, and the device comprises a power module, a signal collection module, a data processing module, a logic judgment and line selection module, a communication module, a human-computer interaction interface, and an early warning and tripping processing module. The signal acquisition module comprises a zero-sequence voltage acquisition unit, a zero-sequence current acquisition unit and a phase voltage acquisition unit, a line selection algorithm is built in the data processing module and the logic judgment and line selection module, and a voltage amplitude detection algorithm and a frequency analysis algorithm are built in the early warning and tripping processing module and have a frequent instantaneous grounding fault line tripping processing function. High-sensitivity acquisition and effective identification of the resonance overvoltage can be realized by accessing a phase voltage signal of a power distribution network system, and the resonance overvoltage is eliminated through frequent instantaneous grounding fault line tripping protection action aiming at a fault line in which the resonance overvoltage is detected. And the probability of converting a frequent instantaneous grounding fault into a permanent grounding fault is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of single-phase grounding fault detection and processing in a distribution network, and in particular relates to a small current line selection device with a perfect resonant overvoltage tripping logic function. Background Art

[0002] Small current line selection devices have been widely used in power stations, substations, petrochemical industry, coal industry, metallurgical industry and other fields of the power system. These industries have high requirements for the reliability of the power system. Small current line selection devices can timely and accurately select faulty lines, and through accurate line selection, only the faulty lines are repaired, and other lines can still supply power normally, reducing the number and scope of power outages, and effectively ensuring the safe and stable operation of the power system.

[0003] At present, more and more substations are beginning to install small current line selection devices to improve the grounding line selection capability and power supply reliability of the power grid. For example, some regions have gradually promoted the transformation of small current line selection devices and achieved full coverage of grounding line selection devices in substations.

[0004] Most of the 10kV distribution networks in Shangqiu area adopt the ungrounded neutral point method, and the proportion of single-phase grounding faults is high, which is prone to system resonance. In order to accurately identify the fault line, measures such as installing a small current line selection device in the substation and installing intelligent switches and fault indicators on the distribution lines outside the station were taken. At the same time, in order to quickly isolate the fault line, the line selection device and the intelligent switch were put into the tripping function. The above measures effectively reduced the handling time of permanent single-phase grounding faults, but they could not effectively protect the system from resonant overvoltage caused by frequent instantaneous grounding faults. Instantaneous grounding faults are often accompanied by arcing and resonant overvoltages, which can reach 3 to 5 times the phase voltage in severe cases, which can easily cause voltage transformer saturation, lightning arrester failure, insulation breakdown, etc., causing the accident to expand, and the harm is far greater than the grounding fault itself. In order to solve the above problems, it is necessary to develop a small current line selection device with a perfect resonant overvoltage tripping logic function. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a small current line selection device with a complete resonant overvoltage tripping logic function. The device can realize high-sensitivity collection and effective identification of resonant overvoltage by accessing the phase voltage signal of the distribution network system, and eliminate the resonant overvoltage through the frequent instantaneous ground fault line tripping protection action for the fault line where the resonant overvoltage is detected, thereby reducing the probability of frequent instantaneous ground faults turning into permanent ground faults, further reducing the occurrence of power outages and safety accidents, thereby improving the working stability and reliability of the distribution network system.

[0006] The object of the present invention is achieved in this way: to provide a small current line selection device with a perfect resonant overvoltage tripping logic function, including a power supply module, a signal acquisition module, a data processing module, a logic judgment and line selection module, a communication module, a human-computer interaction interface and an early warning and tripping processing module, the signal acquisition module includes a zero-sequence voltage acquisition unit, a zero-sequence current acquisition unit and a phase voltage acquisition unit, the data processing module and the logic judgment and line selection module have built-in line selection algorithms, the early warning and tripping processing module has built-in voltage amplitude detection algorithms and frequency analysis algorithms and frequent instantaneous ground fault line tripping processing functions, the data processing module is based on the built-in line selection algorithm After completing the processing of the collected signals of the signal collection module, the signals are sent to the logic judgment and line selection module. The logic judgment and line selection module completes the line selection of the fault line according to the built-in line selection algorithm, and at the same time sends the processed related collected data of the fault line to the early warning and tripping processing module. The early warning and tripping processing module completes the resonant overvoltage identification of the fault line according to the built-in voltage amplitude detection algorithm and frequency analysis algorithm, and sends an alarm signal to the fault line with the identified resonant overvoltage. At the same time, according to the built-in frequent instantaneous grounding fault line tripping processing function, the frequent instantaneous grounding fault line tripping of the identified resonant overvoltage fault line is completed.

[0007] Preferably, the zero-sequence voltage acquisition unit includes a voltage transformer installed on the bus, the zero-sequence current acquisition unit includes a current transformer installed on the bus, and the phase voltage acquisition unit includes a voltage transformer installed on the three-phase line.

[0008] Further preferably, the performance selection requirements of the voltage transformer are high precision, wide bandwidth and good linearity, and the performance selection requirements of the data acquisition device of the signal acquisition module are high speed and multi-channel.

[0009] Preferably, the line selection algorithm includes a zero-sequence current method, a zero-sequence power direction method and a blind half-wave method.

[0010] Preferably, the voltage amplitude detection algorithm is specifically as follows: a warning threshold of the zero-sequence voltage amplitude is set, the algorithm compares the zero-sequence voltage amplitude collected in real time with the set warning threshold, and triggers the warning mechanism when the collected voltage amplitude exceeds the warning threshold.

[0011] Preferably, the frequency analysis algorithm is specifically as follows: using a fast Fourier transform spectrum analysis algorithm, first performing frequency analysis on the collected voltage signal through the fast Fourier transform spectrum analysis algorithm, converting the time domain voltage signal into a frequency domain signal, obtaining the frequency component of the voltage signal and its amplitude distribution, and then judging whether there is a signal component close to the inherent resonant frequency in the frequency domain analysis result according to the inherent resonant frequency range of the system, and when an obvious voltage signal component is detected with a large amplitude, it is judged that a resonant overvoltage has occurred.

[0012] Preferably, the frequent instantaneous ground fault line tripping processing function is specifically: when the resonant overvoltage is detected, the resonant overvoltage is eliminated through the frequent instantaneous ground fault line tripping action, thereby reducing the probability of frequent instantaneous ground faults turning into permanent ground faults.

[0013] Preferably, the alarm signal uses both local alarm and remote alarm.

[0014] Due to the adoption of the above technical scheme, the beneficial effects of the present invention are as follows: on the basis of the existing small current line selection device, the present invention realizes high-sensitivity collection and effective identification of resonant overvoltage by accessing the phase voltage signal of the distribution network system, and for the fault line where the resonant overvoltage is detected, the frequent instantaneous ground fault line tripping protection action is performed to eliminate the resonant overvoltage, reduce the probability of frequent instantaneous ground faults turning into permanent ground faults, further reduce the occurrence of power outages and safety accidents, thereby improving the working stability and reliability of the distribution network system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the device of the present invention. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0017] like Figure 1 As shown, the present invention provides a small current line selection device with a complete resonant overvoltage tripping logic function, including a power supply module, a signal acquisition module, a data processing module, a logic judgment and line selection module, a communication module, a human-computer interaction interface and an early warning and tripping processing module. When implemented specifically, the appearance structure of the small current grounding line selection device in the prior art can be used, and the above-mentioned modules can be stored therein or arranged on the surface of its shell.

[0018] The power module provides suitable working power for the entire line selection device.

[0019] The signal acquisition module includes a zero-sequence voltage acquisition unit, a zero-sequence current acquisition unit and a phase voltage acquisition unit. That is, on the basis of the existing zero-sequence voltage acquisition unit and the zero-sequence current acquisition unit, a new phase voltage acquisition unit is added to facilitate the subsequent high-sensitivity acquisition and effective identification of resonant overvoltage through phase voltage signals (comprehensively considering the bus and three-wire lines).

[0020] Specifically, the zero-sequence voltage acquisition unit includes a voltage transformer installed on the bus, the zero-sequence current acquisition unit includes a current transformer installed on the bus, and the phase voltage acquisition unit includes a voltage transformer installed on the three-phase line.

[0021] The performance requirements for voltage transformers are high precision, wide bandwidth and good linearity. Selecting voltage transformers with high precision and wide bandwidth can accurately measure system voltage. For example, a 10kV system can use electromagnetic or capacitive voltage transformers with an accuracy level of 0.2 or above. These voltage transformers have good linearity, and the collected signals can accurately reflect voltage changes within a wider voltage range.

[0022] For the signal acquisition module, a high-speed, multi-channel data acquisition device is required to adapt to the collection of three-phase voltage signals. At the same time, it has a higher sampling frequency. For example, the sampling frequency of a 50Hz distribution network system needs to reach above 1000Hz, which can more accurately capture the instantaneous changes in voltage, including fluctuations in voltage amplitude and frequency caused by possible resonant overvoltage.

[0023] The data processing module uses a high-performance microprocessor CPU or digital signal processor DSP, which can condition the collected voltage and current signals, including amplification, filtering, analog-to-digital conversion and other processing. It amplifies the weak collected signals to facilitate subsequent processing, removes high-frequency interference noise in the signals through filtering circuits, ensures that the collected signals can accurately reflect the actual operating status of the distribution system, and converts the analog signals into digital signals for subsequent processing through analog-to-digital conversion.

[0024] The data processing module and the logic judgment and line selection module all have built-in line selection algorithms. The built-in line selection algorithm of the data processing module is used to perform corresponding data processing on the collected signals according to the line selection algorithm, so as to facilitate the subsequent line selection work. The built-in line selection algorithm of the logic judgment and line selection module is used to perform logical judgment on the processed collected signals according to the line selection algorithm, so as to facilitate the subsequent line selection of the faulty line according to the logical judgment result. Then, without power outage, it is only necessary to inspect and repair the selected faulty line manually or through the automatic tripping function equipped by the line selection device, thereby reducing the number and scope of power outages.

[0025] The line selection algorithm can adopt the zero-sequence current method, zero-sequence power direction method or blind half-wave method of the existing technology. The zero-sequence current method is that when a single-phase grounding fault occurs in a small current grounding system, a zero-sequence current will be generated. At this time, the zero-sequence current of the fault line is greater than the capacitive current of the non-fault line; in the zero-sequence power direction method, the zero-sequence power direction of the fault line is from the line to the bus, while the zero-sequence power direction of the non-fault line is from the bus to the line, so the fault line is selected by judging the direction of the zero-sequence power; in the blind half-wave method, the blind half-wave current of the fault line is opposite to the blind half-wave current of the non-fault line in polarity, so the fault line is selected based on this characteristic.

[0026] The early warning and tripping processing module has built-in voltage amplitude detection algorithm and frequency analysis algorithm as well as frequent instantaneous ground fault line tripping processing function.

[0027] The voltage amplitude detection algorithm is to set the warning threshold of the zero-sequence voltage amplitude in the software of the line selection device. The algorithm compares the collected zero-sequence voltage amplitude with the set warning threshold in real time. When the collected voltage amplitude exceeds the warning threshold, the warning mechanism is triggered. An alarm signal is sent through the warning mechanism to remind the staff to handle it or the system to handle it automatically according to the preset procedure.

[0028] Specifically, the warning threshold needs to be determined based on the normal operating voltage range of the system and historical data. For example, for a 10kV system, the zero-sequence voltage is generally within tens of volts during normal operation. Then it can be set so that when the zero-sequence voltage amplitude exceeds 100 volts, a resonant voltage occurs in the fault line. The resonant voltage needs to be processed immediately to eliminate it. Otherwise, it will likely cause a permanent fault over time.

[0029] Among them, the alarm signal can be used as local alarm and remote alarm at the same time. Among them, the local alarm can be realized through the sound and light alarm device installed in the local substation. When the resonance overvoltage is detected, the alarm light of the sound and light alarm device starts to flash, and the buzzer sounds an alarm to remind the staff in the substation to pay attention to the abnormal situation of the system and deal with it in time to ensure the normal operation of the substation. Among them, the remote alarm is to send the alarm signal to the remote monitoring center through the communication module. After the monitoring system of the monitoring center receives the alarm signal, it can display the specific alarm signal content on the monitoring interface, such as which substation, which bus or which line may have a resonance overvoltage situation, and timely track the subsequent processing to ensure the normal operation of the entire distribution network system.

[0030] The frequency analysis algorithm uses spectrum analysis algorithms such as fast Fourier transform (FFT). First, the collected voltage signal is frequency analyzed through the FFT algorithm, and the time domain voltage signal is converted into a frequency domain signal to obtain the frequency component of the voltage signal and its amplitude distribution. Then, according to the system's inherent resonant frequency range, it is determined in the frequency domain analysis results whether there is a signal component close to the inherent resonant frequency. When an obvious voltage signal component is detected with a large amplitude, it is determined that a resonant overvoltage has occurred.

[0031] Specifically, the natural resonant frequency range of the system can be determined through theoretical calculation and field testing. For example, if the natural resonant frequency of the system is between 300 and 500 Hz, then when a significant voltage signal component with a large amplitude is detected within this frequency range, it indicates that a resonant overvoltage has occurred.

[0032] The resonant overvoltage protection action logic of the frequent instantaneous ground fault line tripping processing function is: when the resonant overvoltage is detected, the frequent instantaneous ground fault line tripping action is used to eliminate the resonant overvoltage and reduce the probability of frequent instantaneous ground faults turning into permanent ground faults.

[0033] The communication module is used to upload the information on the line selection device to the remote monitoring center and also receive remote control instructions. Its communication method can be Ethernet, high-speed serial port communication (such as RS485 interface, SPI interface, 2C interface) and internal bus (such as CAN bus) of existing technology.

[0034] The human-machine interaction interface provides an interactive operation interface for the line selection device and the staff. The line selection device displays its working status to the staff through the human-machine interaction interface, and the staff checks and intervenes in the line selection device through the human-machine interaction interface.

[0035] During operation, the data processing module completes the processing of the collected signals of the signal acquisition module according to the built-in line selection algorithm and sends the processed signals to the logic judgment and line selection module. The logic judgment and line selection module completes the line selection of the fault line according to the built-in line selection algorithm and sends the processed collected data related to the fault line to the early warning and tripping processing module. The early warning and tripping processing module completes the identification of the resonant overvoltage of the fault line according to the built-in voltage amplitude detection algorithm and frequency analysis algorithm, sends an alarm signal to the fault line with the identified resonant overvoltage, and completes the tripping of the frequent instantaneous grounding fault line of the identified resonant overvoltage fault line according to the built-in frequent instantaneous grounding fault line tripping processing function.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific implementation modes of the present invention can still be modified or replaced by equivalents, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A low current line selection device with a perfect resonant overvoltage tripping logic function, comprising a power supply module, a signal acquisition module, a data processing module, a logic judgment and line selection module, a communication module and a human-computer interaction interface, characterized in that: It also includes an early warning and tripping processing module, the signal acquisition module includes a zero-sequence voltage acquisition unit, a zero-sequence current acquisition unit and a phase voltage acquisition unit, the data processing module and the logic judgment and line selection module have built-in line selection algorithms, the early warning and tripping processing module has built-in voltage amplitude detection algorithm and frequency analysis algorithm and frequent instantaneous ground fault line tripping processing function, the data processing module completes the collection signal processing of the signal acquisition module according to the built-in line selection algorithm and sends it to the logic judgment and line selection module, the logic judgment and line selection module completes the line selection of the fault line according to the built-in line selection algorithm, and sends the processed fault line related collection data to the early warning and tripping processing module, the early warning and tripping processing module completes the resonant overvoltage identification of the fault line according to the built-in voltage amplitude detection algorithm and frequency analysis algorithm, sends an alarm signal to the fault line with the identified resonant overvoltage, and completes the frequent instantaneous ground fault line tripping of the identified resonant overvoltage fault line according to the built-in frequent instantaneous ground fault line tripping processing function.

2. The low current line selection device with perfect resonant overvoltage tripping logic function according to claim 1 is characterized in that: The zero-sequence voltage acquisition unit includes a voltage transformer installed on the bus, the zero-sequence current acquisition unit includes a current transformer installed on the bus, and the phase voltage acquisition unit includes a voltage transformer installed on the three-phase line.

3. The low current line selection device with perfect resonant overvoltage tripping logic function according to claim 2 is characterized in that: The performance requirements of the voltage transformer are high precision, wide bandwidth and good linearity, and the performance requirements of the data acquisition device of the signal acquisition module are high speed, multi-channel and high sampling frequency.

4. The low current line selection device with perfect resonant overvoltage tripping logic function according to claim 1 is characterized in that: The line selection algorithm includes a zero-sequence current method, a zero-sequence power direction method and a blind half-wave method.

5. The low current line selection device with perfect resonant overvoltage tripping logic function according to claim 1 is characterized in that: The voltage amplitude detection algorithm is specifically as follows: a warning threshold of the zero-sequence voltage amplitude is set, the algorithm compares the zero-sequence voltage amplitude collected in real time with the set warning threshold, and triggers the warning mechanism when the collected voltage amplitude exceeds the warning threshold.

6. The low current line selection device with perfect resonant overvoltage tripping logic function according to claim 1 is characterized in that: The frequency analysis algorithm is specifically as follows: a fast Fourier transform spectrum analysis algorithm is used to first perform frequency analysis on the collected voltage signal through the fast Fourier transform spectrum analysis algorithm, and the voltage signal in the time domain is converted into a frequency domain signal to obtain the frequency component of the voltage signal and its amplitude distribution. Then, based on the inherent resonant frequency range of the system, it is determined in the frequency domain analysis results whether there is a signal component close to the inherent resonant frequency. When an obvious voltage signal component is detected with a large amplitude, it is determined that a resonant overvoltage has occurred.

7. The low current line selection device with perfect resonant overvoltage tripping logic function according to claim 1 is characterized in that: The frequent instantaneous ground fault line tripping processing function is specifically: when the resonance overvoltage is detected, the frequent instantaneous ground fault line tripping action is performed to eliminate the resonance overvoltage and reduce the probability of the frequent instantaneous ground fault turning into a permanent ground fault.

8. The low current line selection device with perfect resonant overvoltage tripping logic function according to claim 1 is characterized in that: The alarm signal uses both local alarm and remote alarm.

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