Power station small current grounding line selection system

Abstract

The invention discloses a power station small current grounding line selection system, which relates to the technical field of power system protection, and comprises a data acquisition module for acquiring each phase current, each phase voltage and grounding resistance of a power system, and calculating the effective value of the phase current, the effective value of the phase voltage and the change rate of the grounding resistance; the collected and calculated data are transmitted to the fault detection module and the display module; the fault detection module receives the data, analyzes the state and judges the types of faults and grounding faults; after the line selection positioning module positions a fault point, the control protection module automatically takes protection measures and generates a system self-inspection report, and the module self-inspection report and related data are displayed. According to the method, the fault state is quickly calculated and analyzed by automatically acquiring the current of each phase, the voltage of each phase and the grounding resistance data, so that the response speed and accuracy are greatly improved, the type of the grounding fault can be accurately judged, the high precision of fault positioning is ensured, and real-time monitoring and automatic protection measure taking are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power system protection, in particular to a small current grounding line selection system for a power station. Background Art

[0002] In modern power systems, ground faults are a common and potentially harmful type of fault that can cause equipment damage, power outages, and even personal safety risks. This is especially true in low-current grounding systems, where traditional protection devices often struggle to effectively detect and locate faults due to the low fault current values. This poses a challenge to the safe operation of power systems. Low-current grounding systems are designed to reduce the impact of ground faults on power equipment by controlling the ground current and minimizing damage to equipment caused by ground faults. However, with the increase in power loads and the complexity of power systems, the rapid and accurate detection of ground faults and the location of fault points have become pressing issues for the power industry. Traditional ground fault detection methods rely primarily on regular manual inspections and simple monitoring equipment, with drawbacks such as slow response, low accuracy, and the inability to monitor in real time. Summary of the Invention

[0003] The purpose of the present invention is to provide a power station low-current grounding line selection system to solve the problems of the existing ground fault detection method mainly relying on regular manual inspections and simple monitoring equipment, which have slow response speed, low accuracy and inability to monitor in real time.

[0004] The present invention solves the above problems through the following technical solutions:

[0005] A power station low-current grounding line selection system includes a data acquisition module, a fault detection module, a line selection and positioning module, a control and protection module, and a display module, wherein:

[0006] The data acquisition module is used to obtain the phase current, phase voltage and ground resistance of the power system in real time, calculate the effective value of the phase current, the effective value of the phase voltage and the rate of change of the ground resistance, and transmit the collected and calculated data to the fault detection module and the display module;

[0007] a fault detection module, configured to receive data input by the data acquisition module, perform status analysis and make fault judgments, and determine the type of ground fault by calculating the imbalance of each phase current, the fault current amplitude, the phase angle of each phase current, the power factor of each phase, and the waveform characteristics of the ground fault current;

[0008] The line selection and positioning module is used to calculate the distance from the fault point to the monitoring point based on the judgment result of the fault detection module, and output the coordinate information of the fault point to the control and protection module;

[0009] The control and protection module is used to automatically take protective measures after receiving a ground fault signal, generate a system self-test report and send it to the display module for display. The automatically taken protective measures include quickly disconnecting the fault line, starting the backup system and switching to the redundant power supply. The system self-test report is used to evaluate the effectiveness of the ground protection system.

[0010] The present invention automatically obtains the data of each phase current, each phase voltage and ground resistance, quickly calculates and analyzes the fault status, greatly improving the response speed and accuracy. Through detailed status analysis, it can accurately determine the type of ground fault and quickly calculate the fault point location, ensuring high-precision fault location and realizing real-time monitoring. In addition, after receiving the fault signal, the control and protection module can quickly and automatically take protective measures.

[0011] Furthermore, the calculation formula of the effective value of the phase current is:

[0012]

[0013] Among them, I eff represents the effective value of the phase current, T represents the time of a complete cycle, i(t) represents the instantaneous current value at time t, and dt represents the integral sign.

[0014] Furthermore, the calculation formula of the effective value of the phase voltage is:

[0015]

[0016] Among them, V eff represents the effective value of the phase current, T represents the time of a complete cycle, v(t) represents the instantaneous voltage value at time t, and dt represents the differential with respect to the time variable t.

[0017] Furthermore, the calculation formula for the rate of change of the ground resistance is:

[0018]

[0019] Where, ΔR g Indicates the rate of change of ground resistance, R g (t1) represents the ground resistance value at time point t1, R g (t2) represents the ground resistance value at time point t2.

[0020] Furthermore, the calculation formula of the imbalance degree of each phase current is:

[0021]

[0022] Among them, I a ,I b ,I cIndicates the current value of each phase, BP indicates the imbalance of the current of each phase, I avg Indicates the average value of each phase current.

[0023] Furthermore, the calculation formula of the fault current amplitude is:

[0024]

[0025] Among them, I f Indicates the fault current amplitude, I a ,I b ,I c Indicates the current value of each phase.

[0026] Furthermore, the calculation formula of the phase angle of each phase current is:

[0027]

[0028] in, Indicates the phase angle of each phase current, arctan represents the inverse function, I q Represents the imaginary current of each phase, I d represents the real part of each current.

[0029] Furthermore, the calculation formula of the phase angle of each phase power factor is:

[0030]

[0031] Wherein, PF represents the power factor of each phase, and cos represents the cosine function.

[0032] Furthermore, the calculation formula of the waveform characteristic of the ground fault current is:

[0033]

[0034] Where F(x) represents the signal in the frequency domain, f(t) represents the fault current waveform in the time domain, which is a digital signal obtained by analog-to-digital conversion of the waveform signal collected by the current sensor in real time, j represents the imaginary unit, w represents the frequency of f(t), and e -jwt represents the complex exponential function, and dt represents the differential with respect to the time variable t.

[0035] Furthermore, the calculation formula for the distance from the fault point to the monitoring point is:

[0036] Ds=vc*t f

[0037] Where Ds represents the distance from the fault point to the monitoring point, vc represents the signal propagation speed, which can be obtained from the electromagnetic parameter table of the cable provided by the manufacturer, and t fIndicates the time required from the occurrence of a fault to the detection point, acquired through a high-speed sampler.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] The present invention automatically obtains the data of each phase current, each phase voltage and grounding resistance, quickly calculates and analyzes the fault status, and greatly improves the response speed and accuracy. The fault detection module can accurately determine the type of grounding fault through detailed status analysis, and combine with the digital signal processing algorithm to quickly calculate the fault point location to ensure high-precision fault location. In addition, after receiving the fault signal, the control and protection module can quickly and automatically take protective measures, such as cutting off the fault line and switching to the redundant power supply, thereby effectively reducing the safety hazards and economic losses caused by the grounding fault. At the same time, the generation of the system self-test report and the real-time monitoring interface of the display module further enhance the user's control over the power system status. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a system block diagram of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0042] Example:

[0043] Combined with attachment Figure 1 As shown, a power station low-current grounding line selection system includes a data acquisition module, a fault detection module, a line selection and positioning module, a control and protection module, and a display module, wherein:

[0044] The data acquisition module is used to obtain the phase current, phase voltage and ground resistance of the power system in real time, calculate the effective value of the phase current, the effective value of the phase voltage and the rate of change of the ground resistance, and transmit the collected and calculated data to the fault detection module and the display module;

[0045] a fault detection module, configured to receive data input by the data acquisition module, perform status analysis and make fault judgments, and determine the type of ground fault by calculating the imbalance of each phase current, the fault current amplitude, the phase angle of each phase current, the power factor of each phase, and the waveform characteristics of the ground fault current;

[0046] The line selection and positioning module is used to calculate the distance from the fault point to the monitoring point based on the judgment result of the fault detection module, and output the coordinate information of the fault point to the control and protection module;

[0047] The control and protection module is used to automatically take protective measures after receiving a ground fault signal, generate a system self-test report and send it to the display module for display. The automatically taken protective measures include quickly disconnecting the fault line, starting the backup system and switching to the redundant power supply. The system self-test report is used to evaluate the effectiveness of the ground protection system.

[0048] The present invention automatically obtains the data of each phase current, each phase voltage and ground resistance, quickly calculates and analyzes the fault status, greatly improving the response speed and accuracy. Through detailed status analysis, it can accurately determine the type of ground fault and quickly calculate the fault point location, ensuring high-precision fault location and realizing real-time monitoring. In addition, after receiving the fault signal, the control and protection module can quickly and automatically take protective measures.

[0049] The data acquisition module plays a key real-time monitoring role in the power system. Its main purpose is to obtain the parameters of each phase current, each phase voltage, and ground resistance. These data are collected in real time through high-precision sensors and acquisition circuits, and digitized through analog-to-digital converters (ADCs) to ensure data accuracy and timeliness.

[0050] Furthermore, the calculation formula of the effective value of the phase current is:

[0051]

[0052] Among them, I eff represents the effective value of the phase current, T represents the duration of a complete cycle, i(t) represents the instantaneous current value at time t, and dt represents the integral sign. Calculating the effective value of current provides the DC equivalent of continuously changing current, enabling engineers to understand the actual operating state of the current and avoid misjudgments caused by current fluctuations. Long-term monitoring of the effective value not only ensures proper equipment operation but also helps identify potential overloads and system failures.

[0053] Furthermore, the calculation formula of the effective value of the phase voltage is:

[0054]

[0055] Among them, V eff represents the effective value of the phase current, T represents the duration of a complete cycle, v(t) represents the instantaneous voltage value at time t, and dt represents the differential with respect to the time variable t. By calculating the effective value of the phase voltage, the system can monitor voltage stability and promptly detect voltage fluctuations or imbalances, which is crucial for maintaining power equipment and ensuring the quality of power supply to users. Stable monitoring of effective voltage helps improve power grid security and prevent equipment damage or power outages caused by voltage anomalies.

[0056] Furthermore, the calculation formula for the rate of change of the ground resistance is:

[0057]

[0058] Where, ΔR g Indicates the rate of change of ground resistance, R g (t1) represents the ground resistance value at time point t1, R g (t2) represents the ground resistance value at time t2. Monitoring the rate of change of ground resistance is crucial for assessing the reliability of the grounding system. Stable ground resistance effectively prevents leakage and short circuits, thereby ensuring the safety of equipment and personnel. By tracking changes in ground resistance in real time, engineers can promptly adjust the grounding system to prevent potential safety hazards to the power system caused by ground faults.

[0059] All of the above data will be transmitted to the fault detection module after real-time processing by the data acquisition module, providing a reliable data basis for subsequent fault diagnosis and processing. This precise data acquisition and processing method effectively improves the monitoring capability, stability and safety of the power system, thereby ensuring the efficient operation of the power system and reducing the failure rate.

[0060] The fault detection module is responsible for receiving the phase current, phase voltage and ground resistance data from the data acquisition module in the monitoring of the power system. This module uses advanced signal processing algorithms and fault diagnosis logic to conduct in-depth status analysis to achieve fault judgment.

[0061] Furthermore, the calculation formula of the imbalance degree of each phase current is:

[0062]

[0063] Among them, I a ,I b ,I c Indicates the current value of each phase, BP indicates the imbalance of the current of each phase, I avg The benefit of calculating imbalance is that it can effectively identify uneven current fluctuations, which can indicate possible equipment failure or load mismatch. If the imbalance exceeds the normal range, the system can immediately issue an alarm, allowing engineers to take preventative measures to avoid equipment damage or long-term operational failures caused by the imbalance.

[0064] Furthermore, the calculation formula of the fault current amplitude is:

[0065]

[0066] Among them, I f Indicates the fault current amplitude, I a,I b ,I c Indicates the current value of each phase.

[0067] The above formula integrates the square values of the currents in each phase to provide the effective magnitude of the fault current. This data is crucial for determining the safety status of the system. It enables operators to promptly identify current changes after an accident and take appropriate protective measures.

[0068] Furthermore, the calculation formula of the phase angle of each phase current is:

[0069]

[0070] in, Indicates the phase angle of each phase current, arctan represents the inverse function, I q Represents the imaginary current of each phase, I d The real part of each current is represented by the phase angle. By analyzing the phase angle, engineers can identify phase differences between phases, which is crucial for determining whether a ground fault exists. Phase angle fluctuations may indicate a potential ground fault or short circuit event. Therefore, timely phase angle monitoring can effectively improve system safety and response speed.

[0071] Furthermore, the calculation formula of the phase angle of each phase power factor is:

[0072]

[0073] Here, PF represents the power factor of each phase, and cos represents the cosine function. Calculating the power factor helps assess the energy efficiency of power systems. A low power factor not only means higher energy loss but may also indicate grounding problems. Therefore, real-time monitoring of the power factor provides important energy management information for equipment operation.

[0074] Furthermore, the fault detection module also analyzes the waveform characteristics of the ground fault current. Through spectrum analysis and time domain analysis, the ground fault type can be identified in a timely manner. The waveform characteristics are monitored through technical means such as Fourier transform. The calculation formula of the waveform characteristics of the ground fault current is:

[0075]

[0076] Where F(x) represents the signal in the frequency domain, f(t) represents the fault current waveform in the time domain, which is a digital signal obtained by analog-to-digital conversion of the waveform signal collected by the current sensor in real time, j represents the imaginary unit, w represents the frequency of f(t), and e -jwtdenotes a complex exponential function, and dt denotes the differential with respect to the time variable t. This method effectively converts time-domain signals into frequency-domain signals, enabling accurate identification and classification of ground fault waveforms while examining the signal's frequency components. This allows the system to quickly locate the source of the fault and provide real-time feedback, ensuring that appropriate protective measures can be taken promptly in the event of a power system fault.

[0077] The method for determining the type of ground fault based on the above calculated values is as follows:

[0078] During normal operation, the three-phase currents are basically balanced, and the imbalance is low (generally within 5%). If the imbalance increases significantly (exceeds the threshold, such as above 10%), it indicates that a ground fault or short circuit may occur in one phase. Therefore, when the imbalance is extremely high (>30%), it indicates an obvious single-phase ground fault or short circuit fault. Low imbalance (<10%) indicates normal or minor faults, which will not affect the judgment for the time being.

[0079] A large fault current amplitude (close to the system rated current or overload value) indicates a severe ground fault (such as a severe single-phase ground fault or a multi-phase fault), while a small amplitude (much lower than the system rated current) may indicate a slight ground fault or a partial ground leakage. (In electrical engineering, "slight ground fault" or "partial ground leakage" usually refers to an incomplete electrical connection between some part of the electrical system and the ground.)

[0080] In a single-phase grounding fault, the current phase angle of the faulted phase deviates slightly from that of the normal phase, while the phase angle of the ungrounded phase does not change much. The zero-sequence current phase is the same as or close to that of the grounded phase. Therefore, the phase angle shift is significant (for example, exceeding 30 degrees), indicating that the faulty phase is the grounding point. If the other phases are normal, such as the phases are consistent or the deviation is small, it may be a multi-phase grounding.

[0081] Since a ground fault causes changes in current phase and voltage, it will affect the power factor. Therefore, when the power factor drops significantly (becomes negative or close to zero), it indicates that the system is grounded or short-circuited, which may be single-phase grounding or multi-phase grounding.

[0082] The waveform characteristics of the ground fault current include frequency components and harmonic changes. Single-phase grounding usually produces a significant increase in the zero-sequence component and specific harmonic characteristics in the waveform. Therefore, the zero-sequence component in the waveform is significantly enhanced, and harmonic analysis shows that the zero-sequence harmonic component is significant, indicating a single-phase grounding. Enhanced high-order harmonics or specific frequency components in the waveform may indicate multi-phase grounding or a complex fault.

[0083] The above calculation and analysis methods not only improve the accuracy and response speed of fault detection, but also help maintenance personnel better understand and deal with potential risks, thereby significantly improving the safety and reliability of the power system.

[0084] The line selection and location module plays a crucial role in the power system. It uses digital signal processing (DSP) algorithms to locate the fault point based on the judgment results of the fault detection module. Specifically, this module uses time domain reflectometry or waveform feature-based algorithms to calculate the distance between the fault point and the monitoring point by measuring the propagation time of the fault signal. The distance calculation formula is:

[0085] Ds=vc*t f

[0086] Where Ds represents the distance from the fault point to the monitoring point, vc represents the propagation speed of the electrical signal in the conductor (usually an approximation of the speed of light in the cable), which is obtained from the electromagnetic parameter table of the cable provided by the manufacturer, and t f This calculation method has significant advantages: it can not only quickly and accurately determine the location of the fault point, but also provide real-time feedback to the system control module, reducing fault processing time and improving system response speed and operating efficiency. f It can be acquired through a high-speed sampler.

[0087] Next, when the control and protection module receives a ground fault signal, it automatically initiates a series of protective measures, including rapidly disconnecting the faulty line, activating the backup system, and switching to the redundant power source. The decision to quickly disconnect the faulty line is based on real-time current and voltage data. The calculation of the fault current amplitude provides a safety basis for decision-making and can promptly identify overload or short circuit conditions. By quickly disconnecting the faulty line, the system can effectively prevent further damage to equipment or impact on power services in neighboring areas. Activating the backup system and switching to the redundant power source ensures the continuity of power supply, greatly improving the stability of the power system.

[0088] In addition, the control and protection module generates a system self-test report, providing further reliability analysis by evaluating the effectiveness of the ground protection system. This report integrates data from adjacent monitoring systems and interprets it using advanced data analysis methods (such as regression analysis and statistical models). This process can identify potential system failure risks and provide recommendations to optimize and improve equipment maintenance strategies. The information in the report provides valuable decision support for subsequent maintenance work.

[0089] Finally, the display module displays system self-test reports and related data on the monitoring interface, including real-time current, voltage, and ground resistance values. Through this visualization tool, operators can intuitively monitor the current status of the system and obtain key information in real time. This intuitive information display not only improves operator work efficiency but also ensures timely response, further enhancing system security.

[0090] Through the above series of technical means and calculation methods, the fault location and processing capabilities of the power system have been significantly improved, and the automation and efficiency of fault response have been achieved, thereby effectively maintaining the stability and safety of the power system.

[0091] Although the present invention is described herein with reference to illustrative embodiments of the present invention, the above embodiments are merely preferred embodiments of the present invention, and the embodiments of the present invention are not limited to the above embodiments. It should be understood that those skilled in the art can design many other modifications and implementations, which will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A power station low current grounding line selection system, characterized in that: It includes data acquisition module, fault detection module, line selection and positioning module, control and protection module and display module, among which: The data acquisition module is used to obtain the phase current, phase voltage and ground resistance of the power system in real time, calculate the effective value of the phase current, the effective value of the phase voltage and the rate of change of the ground resistance, and transmit the collected and calculated data to the fault detection module and the display module; a fault detection module, configured to receive data input by the data acquisition module, perform status analysis and make fault judgments, and determine the type of ground fault by calculating the imbalance of each phase current, the fault current amplitude, the phase angle of each phase current, the power factor of each phase, and the waveform characteristics of the ground fault current; The line selection and positioning module is used to calculate the distance from the fault point to the monitoring point based on the judgment result of the fault detection module, and output the coordinate information of the fault point to the control and protection module; The control and protection module is used to automatically take protection measures after receiving the ground fault signal, generate a system self-test report and send it to the display module for display.

2. A power station low current grounding line selection system according to claim 1, characterized in that: The calculation formula of the effective value of the phase current is: Among them, I eff represents the effective value of the phase current, T represents the time of a complete cycle, i(t) represents the instantaneous current value at time t, and dt represents the integral sign.

3. A power station low current grounding line selection system according to claim 1, characterized in that: The calculation formula of the effective value of the phase voltage is: Among them, V eff represents the effective value of the phase current, T represents the time of a complete cycle, v(t) represents the instantaneous voltage value at time t, and dt represents the differential with respect to the time variable t.

4. A power station low current grounding line selection system according to claim 1, characterized in that: The calculation formula of the change rate of the ground resistance is: Where, ΔR g Indicates the rate of change of ground resistance, R g (t1) represents the ground resistance value at time point t1, R g (t2) represents the ground resistance value at time point t2.

5. A power station low current grounding line selection system according to claim 1, characterized in that: The calculation formula of the imbalance degree of each phase current is: Among them, I a ,I b ,I c Indicates the current value of each phase, BP indicates the imbalance of the current of each phase, I avg Indicates the average value of each phase current.

6. A power station low current grounding line selection system according to claim 1, characterized in that: The calculation formula of the fault current amplitude is: Among them, I f Indicates the fault current amplitude, I a ,I b ,I c Indicates the current value of each phase.

7. A power station low current grounding line selection system according to claim 1, characterized in that: The calculation formula of the phase angle of each phase current is: in, Indicates the phase angle of each phase current, arctan represents the inverse function, I q Represents the imaginary current of each phase, I d represents the real part of each current.

8. A power station low current grounding line selection system according to claim 7, characterized in that: The calculation formula of the phase angle of each phase power factor is: Wherein, PF represents the power factor of each phase, and cos represents the cosine function.

9. The power station low current grounding line selection system according to claim 1, characterized in that: The calculation formula of the waveform characteristic of the ground fault current is: Where F(x) represents the signal in the frequency domain, f(t) represents the fault current waveform in the time domain, which is a digital signal obtained by analog-to-digital conversion of the waveform signal collected by the current sensor in real time, j represents the imaginary unit, w represents the frequency of f(t), and e -jwt represents the complex exponential function, and dt represents the differential with respect to the time variable t.

10. A power station low current grounding line selection system according to claim 1, characterized in that: The calculation formula of the distance from the fault point to the monitoring point is: Ds=vc*t f Where Ds represents the distance from the fault point to the monitoring point, vc represents the signal propagation speed, and t f Indicates the time required from the occurrence of a fault to the detection point.

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