Method and related device for detecting faults in a power system

Abstract

The present application provides a method and related equipment for detecting faults in a power system. The method includes: calculating the amplitude differences of positive-sequence current, negative-sequence current, zero-sequence current, and zero-sequence voltage of the three-phase nodes of a secondary device based on the instantaneous current values and instantaneous voltage values of the three-phase nodes of a primary device; determining whether a line-break fault occurs in the power system based on the amplitude differences of the positive-sequence current and the negative-sequence current; when it is impossible to determine the line-break fault through the amplitude differences of the positive-sequence current and the negative-sequence current, determining whether a line-break fault occurs in the power system according to the amplitude differences of the zero-sequence current and the zero-sequence voltage. The fault detection method integrating the primary and secondary devices in the present application can analyze whether a fault occurs in the power system more comprehensively and accurately.

Description

Technical Field

[0001] This application relates to the technical field of power systems, and in particular, to a method for detecting faults in a power system and related devices. Background Art

[0002] As an important part of the power system, the safe and reliable operation of the medium-voltage distribution network is of great significance to people's normal electricity use. In particular, if the single-phase open-circuit fault, which is the most common type of open-circuit fault, cannot be detected in time, overvoltage will be generated, rotating motors will be burned out, and even serious accidents such as forest fires and electric shock to humans and livestock will occur.

[0003] For open-circuit grounding faults, due to the large grounding resistance at the fault point and the weak fault current, there are already many related small-current grounding fault detection methods. However, the research on the detection of open-circuit non-grounding faults has not received much attention. Summary of the Invention

[0004] In view of this, the purpose of this application is to propose a method for detecting faults in a power system and related devices to solve or partially solve the above problems.

[0005] Based on the above purpose, this application provides a method for detecting faults in a power system, including:

[0006] Obtaining the instantaneous current values and instantaneous voltage values of the three-phase nodes of the primary equipment in the power system;

[0007] According to the instantaneous current values and the instantaneous voltage values, calculating the amplitude differences of the positive-sequence currents, negative-sequence currents, zero-sequence currents, and the amplitude difference of the zero-sequence voltage of the three-phase nodes of the secondary equipment;

[0008] Based on the amplitude differences of the positive-sequence currents and the amplitude differences of the negative-sequence currents, determining whether an open-circuit fault occurs in the power system;

[0009] In response to being unable to determine an open-circuit fault through the amplitude differences of the positive-sequence currents and the amplitude differences of the negative-sequence currents, determining whether an open-circuit fault occurs in the power system according to the amplitude differences of the zero-sequence currents and the amplitude difference of the zero-sequence voltage.

[0010] Optionally, the calculating the amplitude differences of the positive-sequence currents, negative-sequence currents, zero-sequence currents, and the amplitude difference of the zero-sequence voltage of the three-phase nodes according to the instantaneous current values and the instantaneous voltage values further includes:

[0011] According to the instantaneous current values and the instantaneous voltage values, calculating the amplitudes of the positive-sequence currents, negative-sequence currents, zero-sequence currents, and the amplitude of the zero-sequence voltage of the three-phase nodes;

[0012] Calculate the amplitude differences of the positive-sequence current, negative-sequence current, zero-sequence current, and zero-sequence voltage at intervals of one power frequency cycle based on the amplitudes of the positive-sequence current, negative-sequence current, zero-sequence current, and zero-sequence voltage.

[0013] Optionally, the determining whether a disconnection fault occurs in the power system based on the amplitude differences of the positive-sequence current and the negative-sequence current further includes:

[0014] Determine that a disconnection fault occurs in the power system in response to the amplitude difference of the positive-sequence current being less than zero, the amplitude difference of the negative-sequence current being greater than zero, and the sum of the amplitude differences of multiple positive-sequence currents being greater than or equal to a first threshold.

[0015] Optionally, the determining whether a disconnection fault occurs in the power system based on the amplitude differences of the zero-sequence current and the zero-sequence voltage further includes:

[0016] Determine that a disconnection fault occurs in the power system in response to the amplitude difference of the zero-sequence current being greater than zero, the amplitude difference of the zero-sequence voltage being greater than zero, and the amplitude difference of the zero-sequence voltage being greater than or equal to a second threshold.

[0017] Optionally, the determining whether a disconnection fault occurs in the power system further includes: in response to a disconnection fault occurring in the power system, determining the location where the disconnection fault occurs in the power system.

[0018] Optionally, the in response to a disconnection fault occurring in the power system, determining the location where the disconnection fault occurs in the power system further includes:

[0019] In response to a disconnection fault occurring in the power system, calculate the line voltage amplitude difference between any two of the three-phase nodes;

[0020] Determine the location where the disconnection fault occurs in the power system based on the line voltage amplitude difference.

[0021] Optionally, the determining the location where the disconnection fault occurs in the power system based on the line voltage amplitude difference further includes:

[0022] In response to the line voltage amplitude difference being less than or equal to a third threshold, determine that the location where the disconnection fault occurs in the power system is on the power supply side of the power system.

[0023] Based on the above object, the present application further provides a device for detecting faults in a power system, including:

[0024] An acquisition module configured to acquire the instantaneous current values and instantaneous voltage values of three-phase nodes in the power system;

[0025] A calculation module, configured to calculate the amplitude difference of positive-sequence current, the amplitude difference of negative-sequence current, the amplitude difference of zero-sequence current, and the amplitude difference of zero-sequence voltage of the three-phase node according to the instantaneous current value and the instantaneous voltage value;

[0026] A first detection module, configured to determine whether a line break fault occurs in the power system based on the amplitude difference of positive-sequence current and the amplitude difference of negative-sequence current;

[0027] A second detection module, configured to, in response to being unable to determine a line break fault through the amplitude difference of positive-sequence current and the amplitude difference of negative-sequence current, determine whether a line break fault occurs in the power system according to the amplitude difference of zero-sequence current and the amplitude difference of zero-sequence voltage.

[0028] Optionally, the calculation module is further configured to:

[0029] Calculate the amplitude of positive-sequence current, the amplitude of negative-sequence current, the amplitude of zero-sequence current, and the amplitude of zero-sequence voltage of the three-phase node according to the instantaneous current value and the instantaneous voltage value;

[0030] Calculate the amplitude difference of positive-sequence current, the amplitude difference of negative-sequence current, the amplitude difference of zero-sequence current, and the amplitude difference of zero-sequence voltage separated by one power frequency cycle according to the amplitude of positive-sequence current, the amplitude of negative-sequence current, the amplitude of zero-sequence current, and the amplitude of zero-sequence voltage.

[0031] Optionally, the first detection module is further configured to:

[0032] In response to the amplitude difference of positive-sequence current being less than zero, the amplitude difference of negative-sequence current being greater than zero, and the sum of multiple amplitude differences of positive-sequence current being greater than or equal to a first threshold, determine that a line break fault occurs in the power system.

[0033] Optionally, the second detection module is further configured to:

[0034] In response to the amplitude difference of zero-sequence current being greater than zero, the amplitude difference of zero-sequence voltage being greater than zero, and the amplitude difference of zero-sequence voltage being greater than or equal to a second threshold, determine that a line break fault occurs in the power system.

[0035] Optionally, the second detection module is further configured to:

[0036] In response to a line break fault occurring in the power system, determine the location where the line break fault occurs in the power system.

[0037] Optionally, the second detection module is further configured to:

[0038] In response to a disconnection fault occurring in the power system, calculate the line voltage amplitude difference between any two of the three-phase nodes;

[0039] Determine the location of the disconnection fault in the power system according to the line voltage amplitude difference.

[0040] Optionally, the second detection module is further configured to:

[0041] In response to the line voltage amplitude difference being less than or equal to a third threshold, determine that the location of the disconnection fault in the power system is on the power supply side of the power system.

[0042] Based on the above object, the present application further provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the method described in any of the above embodiments is implemented.

[0043] Based on the above object, the present application further provides a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium stores computer instructions for causing a computer to execute the method described in any of the above embodiments.

[0044] As can be seen from the above, the present application provides a method and related device for detecting faults in a power system. The method includes: calculating the amplitude differences of positive-sequence current, negative-sequence current, zero-sequence current, and zero-sequence voltage of the three-phase nodes of a secondary device according to the instantaneous current values and instantaneous voltage values of the three-phase nodes of a primary device; determining whether a disconnection fault occurs in the power system based on the amplitude differences of the positive-sequence current and the negative-sequence current; when it is impossible to determine the disconnection fault through the amplitude differences of the positive-sequence current and the negative-sequence current, determining whether a disconnection fault occurs in the power system according to the amplitude differences of the zero-sequence current and the zero-sequence voltage. The fault detection method of the integration of the primary and secondary devices in the present application can analyze whether a fault occurs in the power system more comprehensively and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the present application or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1 Shows the equivalent circuit of a single-phase disconnection fault in a non-effectively grounded neutral system.

[0047] Figure 2The flowchart of an exemplary method for detecting faults in a power system according to an embodiment of the present application is shown.

[0048] Figure 3 The schematic diagram of an exemplary device for detecting faults in a power system according to an embodiment of the present application is shown.

[0049] Figure 4 The schematic diagram of an exemplary electronic device according to an embodiment of the present application is shown. Detailed implementation manners

[0050] To make the objectives, technical solutions, and advantages of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0051] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should have the ordinary meanings understood by those of ordinary skill in the art to which the present application belongs. The "first", "second" and similar terms used in the embodiments of the present application do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0052] As an important part of the power system, the safe and reliable operation of the medium-voltage distribution network is of great significance to people's normal power consumption life. With the continuous expansion of the current scale of the medium-voltage distribution network, the operating environment is becoming more and more complex. The continuous improvement of the circuit insulation rate leads to low line heat dissipation efficiency, and the line is prone to melting due to high temperature. In addition, affected by extreme weather such as lightning strikes, disconnection faults occur frequently. Especially, if the most common single-phase disconnection fault in the disconnection faults cannot be detected in time, overvoltage will be generated, rotating motors will be burned out, and even serious accidents such as forest fires and human and livestock electric shocks will occur. For disconnection grounding faults, due to the large grounding resistance at the fault point and the weak fault current, there are many related small current grounding fault detection methods, and the research attention on the detection of disconnection non-grounding faults is not high enough. Therefore, a method and related equipment for detecting faults in a power system provided by the present application are of great significance for ensuring the safety of the power system.

[0053] A method for detecting faults in a power system provided by this application can be applied to fault detection in a power system. This method combines the monitoring information of primary equipment and secondary equipment to judge and detect faults. Primary equipment refers to equipment directly involved in power transmission and distribution, such as transmission lines, transformers, busbars, etc.; secondary equipment refers to equipment used to monitor and control primary equipment, such as relay protection devices, measuring instruments, etc.; the integration of primary and secondary equipment combines the real-time operation data of primary equipment with the protection and measurement information of secondary equipment to achieve more comprehensive and accurate fault analysis and judgment. A method for detecting faults in a power system provided by this application is an algorithm implemented on a feeder terminal unit (FTU).

[0054] In related technologies, methods for identifying and locating single-phase open-circuit faults in medium-voltage distribution networks include line selection methods based on negative-sequence current characteristics and phase current characteristics. However, these methods mainly rely on current-related characteristics, so they lack sensitivity or even fail when the power grid is lightly loaded or unloaded, and there are large errors in the measurement of negative-sequence components. In addition, they are also easily affected by power grid imbalance and lateral faults. Methods in related technologies also include line selection methods based on the amplitude difference of zero-sequence voltages. However, this method relies on communication and data synchronization between FTUs at different locations, usually requires more detection equipment and complex communication systems, bringing certain technical and economic challenges. In addition, related technologies also have problems such as relying on communication and data synchronization between FTUs at different locations, usually requiring more detection equipment and complex communication systems, high costs, complex implementation principles, and methods relying on current-related characteristics lacking sensitivity or even failing when the power grid is lightly loaded or unloaded, and there are large errors in the measurement of negative-sequence components, and low identification accuracy.

[0055] For the open-circuit protection strategy of the feeder terminal unit (FTU) in the in-situ feeder automation system, it is not only necessary to achieve accurate and rapid open-circuit fault detection, but also to determine whether the open-circuit fault point is upstream (power supply side) or downstream (load side) of the FTU. Therefore, the method provided by this application comprehensively analyzes the characteristics of voltage, current, and sequence components of typical open-circuit forms in the medium-voltage distribution network, aiming to propose a fault detection algorithm that combines zero-sequence components, phase current phase, and line voltage amplitude changes. By comprehensively comparing the changes in the zero-sequence voltage amplitude, phase current phase, and line voltage amplitude at the fault point, the FTU can accurately determine the occurrence and location of single-phase ungrounded open-circuit faults, thus filling the deficiencies of existing fault detection algorithms.

[0056] Aiming at the problem of lack of effective detection and protection algorithms for accurate identification and determination of single-phase disconnection faults, the method provided in this application studies the change characteristics of the phase differences of three-phase currents, zero-sequence voltage components, and line voltage amplitude signals in the circuit when a single-phase disconnection fault occurs based on the composite sequence network. It indexes the fault type according to the easy observability of the jump of the zero-sequence voltage and current amplitudes of the fault phase, identifies whether a disconnection fault occurs according to whether the phase current zero-crossing phase changes suddenly, and finally determines the fault location according to the different characteristics of the line voltage amplitude at different positions on the fault line. Through simulation and bench tests, the test results show that the fault detection algorithm integrating the changes of zero-sequence current and voltage, phase current, and line voltage amplitude can successfully achieve fault location, laying a foundation for the design of subsequent disconnection fault detection schemes with better performance.

[0057] Figure 1 The equivalent circuit of a single-phase disconnection fault in an uneffectively grounded neutral system is shown.

[0058] Assume that a single-phase disconnection fault occurs in phase in the line. In the figure, , , are the three-phase (phase A, phase B, and phase C) power supplies of the system respectively; N is the neutral point on the power supply side of the disconnection position; M is the neutral point on the load side of the disconnection position; is the total equivalent shunt capacitance to ground of all non-faulty lines; is the shunt capacitance to ground of the fault line; γ represents a coefficient with a range of 0 - 1; , , are the three-phase voltages of the medium-voltage lines on the power supply side of the disconnection position; , , are the three-phase voltages on the load side of the disconnection position; , are the disconnection grounding transition resistances on both sides of the disconnection point respectively, and , have the same value, both being . By setting different combinations of , , various forms such as disconnection without grounding, disconnection with load-side grounding, disconnection with power supply-side grounding, and disconnection with both sides grounded can be covered. When , tend to positive infinity, it represents that the corresponding side has a disconnection without grounding fault; is the load equivalent impedance of the normal line; Z is the load equivalent impedance downstream of the disconnection point of the fault line. The line impedance is much smaller than the line shunt capacitive reactance and the load impedance and can be ignored.

[0059] When a single-phase line break fault occurs, the values of the sequence currents before and after the break will change, and this change can be used as a starting criterion for judging whether a line break fault has occurred. If is the instantaneous value of the phase A current before the fault, (where i is p, n, 0 respectively) represent the positive (p), negative (n), and zero (0) sequence impedances of the fault point, , , are the instantaneous values of the positive sequence current, negative sequence current, and zero sequence current respectively. After a single-phase line break fault occurs, since the low-voltage side of the main transformer in the distribution network and the high-voltage side of the load transformer both adopt delta connection, the impedance in the zero sequence network can be approximated as infinity. Therefore, the simplified expression formulas for the positive, negative, and zero sequence currents generated by this fault are as follows:

[0060]

[0061] After a line break fault occurs, the directions of the positive and negative sequence currents are opposite to those of the normal currents, and their post-fault change characteristics are relatively significant, making it easy to distinguish from the healthy phase circuit. By specifically analyzing the changes in the positive and negative sequence currents before and after the fault, it can be seen that the change values of the positive and negative sequence currents of the line after the fault are consistent, while the directions of the corresponding phase B and phase C currents are opposite to those of the pre-fault phase currents, and the values are 3 / 2 of the latter. Therefore, when judging a single-phase line break fault, it can be based on the change amplitudes of the positive and negative sequence currents.

[0062] Based on Figure 1 shown equivalent circuit diagram, the simulation of the algorithm can be carried out. The program is developed based on embedded software and runs on the FTU algorithm board. When the algorithm board is powered on and starts up, the line break protection algorithm starts to run. Through the hardware circuit, the instantaneous values of the currents and voltages of A, B, and C (for example, the three-phase nodes) in the monitored line are sampled and extracted. The instantaneous values of the currents can include the three-phase currents , and the instantaneous values of the voltages can include the three-phase voltages . After filtering the sampled original waveforms, the amplitude differences of the positive sequence current, negative sequence current, zero sequence current, and zero sequence voltage are calculated.

[0063] Since when the line is in no-load or light-load state, the current is small, and the starting criterion may not be met when a line break fault occurs at this time, an additional criterion can be added to use the change amount of the zero sequence voltage for auxiliary judgment:

[0064]

[0065] Among them, represents the amplitude of the zero sequence current, represents the amplitude difference of the zero sequence current, represents the amplitude of the zero sequence voltage, represents the amplitude difference of zero-sequence voltage, represents a variable, represents the number of sampling points of the waveform in one period, 、 and represents a fixed-value constant, which can take 0.01.

[0066] After the starting criterion is determined, since the occurrence of a small-current grounding fault will also cause a sudden change in the zero-sequence voltage, the phase of the phase current passing through zero needs to be used as a criterion to further determine the cause of the fault. In some embodiments, when a single-phase disconnection fault occurs in phase A, the amplitude of the phase-A current drops to 0, the amplitudes of the phase-B and phase-C currents remain unchanged, but the phases are opposite. Accordingly, it can be determined whether the disconnection occurs and in which phase the disconnection occurs by whether the phases of the phase-B and phase-C currents are reversed.

[0067]

[0068] Among them, represents the instantaneous value of the line voltage between phases A and B, represents the instantaneous value of the line voltage between phases B and C, represents the instantaneous value of the line voltage between phases C and A, represents the instantaneous value of the neutral-point voltage, represents C / C2, C = C1 + C2, is the formula after Fourier transform, C represents the total capacitance of the circuit, represents the phase-A power supply, represents the phase-B power supply, represents the phase-C power supply, represents the equivalent impedance of the faulty line, represents resistance 、 the value of.

[0069] It can be known that the line voltages on the load side of the disconnection are all 、 、 and other functions. The voltages of each phase of the line upstream (power supply side) of the disconnection position with respect to the neutral point N and the line voltage remain unchanged before and after the disconnection; among the voltages of each phase of the medium-voltage line downstream (load side) of the disconnection position with respect to the neutral point M and the three line voltages, at least one amplitude is lower than 0.8Uset (the third threshold). Therefore, the change amount of the line voltage amplitude (for example, the line voltage amplitude difference) before and after the disconnection can be used to judge the disconnection position.

[0070] In the case of a broken wire fault, in some embodiments, the fault area can be determined based on the change in the effective value of the line voltage. If the broken wire fault point is downstream of the FTU monitoring point, the three-phase voltages at the monitoring point still exist, and only the current in the faulty phase becomes 0. Therefore, the line voltage is the same as that before the fault. If the fault point is upstream of the FTU monitoring point, the phase voltage and phase current of the faulty phase both become 0. Therefore, the line voltage will drop below 0.8 times the normal value.

[0071] Specifically, in some embodiments, the effective value of the line voltage can be obtained, and the line voltage amplitude can be calculated through the effective value of the line voltage:

[0072]

[0073] where represents the line voltage amplitude, represents the effective value of the line voltage.

[0074] As an alternative embodiment, an oscilloscope or other measuring device can also be used to directly measure the amplitude of the line voltage .

[0075] By calculating the line voltage amplitude during a power system fault and the line voltage amplitude before the fault, the line voltage amplitude difference can be calculated. In some embodiments, if the line voltage amplitude difference is less than the third threshold, it is determined that the location of the broken wire fault in the power system is on the power supply side of the power system.

[0076] Figure 2 FIG. shows a flowchart of an exemplary method for detecting faults in a power system according to an embodiment of the present application.

[0077] As Figure 2 shown, the program is based on embedded software development. The program runs in the FTU algorithm board. When the algorithm board is powered on and starts up, the broken wire protection algorithm starts to run. Through the hardware circuit, the instantaneous values of the three-phase currents at the A, B, and C three-phase nodes in the monitored line are sampled and extracted (for example, the instantaneous value of the A-phase current before the fault , the instantaneous value of the B-phase current before the fault , the instantaneous value of the C-phase current before the fault ), and the instantaneous values of the three-phase voltages (for example, the instantaneous value of the A-phase voltage before the fault , the instantaneous value of the B-phase voltage before the fault , the instantaneous value of the C-phase voltage before the fault ). After filtering the sampled original waveforms, the amplitude differences of the positive-sequence current, negative-sequence current, zero-sequence current, and zero-sequence voltage are calculated.

[0078] In some embodiments, according to the symmetrical component method, the amplitudes of the positive-sequence, negative-sequence, and zero-sequence currents of phase A can be calculated by the following formulas.

[0079]

[0080] Where, is the amplitude of the positive-sequence current, is the amplitude of the negative-sequence current, is the amplitude of the zero-sequence current, is the complex operator, = , represents the imaginary unit, is the instantaneous value of the current of phase A before the fault, is the instantaneous value of the current of phase B before the fault, is the instantaneous value of the current of phase C before the fault.

[0081] The amplitude of the zero-sequence voltage can be calculated by the following formula:

[0082]

[0083] Where, is the instantaneous value of the voltage of phase A before the fault, is the instantaneous value of the voltage of phase B before the fault, is the instantaneous value of the voltage of phase C before the fault, is the amplitude of the zero-sequence voltage.

[0084] According to the sampling frequency, the data of N sampling points are read for each power frequency cycle (periodic waveform). At this time, the amplitude differences of the positive-sequence current, negative-sequence current, zero-sequence current, and zero-sequence voltage can be expressed by the following formulas.

[0085]

[0086] Where, , are the amplitude differences of the positive-sequence current and negative-sequence current separated by one power frequency cycle, is the amplitude difference of the zero-sequence current separated by one power frequency cycle, is the amplitude difference of the zero-sequence voltage separated by one power frequency cycle, is the amplitude of the positive-sequence current, is the amplitude of the negative-sequence current, is the amplitude of the zero-sequence current, is the amplitude of the zero-sequence voltage.

[0087] Judge the amplitude differences of the positive-sequence current and negative-sequence current. is the sum of the amplitude differences of consecutive positive-sequence currents, To set the line Positive sequence current value , set to 0.5 . If it satisfies < 0, > 0, and 0.5 (for example, the first threshold), at this time, it is determined that a broken line fault has occurred in the power system. If the condition is not met, the amplitude difference of zero-sequence current and zero-sequence voltage is used to assist in judgment (judging the amplitude difference of zero-sequence current and zero-sequence voltage).

[0088]

[0089] When the amplitude difference of positive and negative sequence currents (i.e., the amplitude change) cannot determine whether a single-phase broken line fault occurs, the amplitude difference of zero-sequence current and the amplitude difference of zero-sequence voltage are used to assist in judgment. The fixed value constant is the zero-sequence overvoltage threshold value, and the fixed value can be taken with reference to the ordinary zero-sequence overvoltage protection. Compare the amplitude difference Δ of the zero-sequence voltage with the given value. When the amplitude difference Δ of the zero-sequence voltage is greater than or equal to the given value (the second threshold), it is considered that a broken line fault has occurred in the power system. If the amplitude difference Δ of the zero-sequence voltage is less than the given value, there is no broken line fault.

[0090]

[0091] After a broken line fault occurs in the power system, in some embodiments, the line voltage amplitude difference between any two of the three-phase nodes can be calculated, and based on the line voltage amplitude difference, the location of the broken line fault in the power system can be determined.

[0092] Calculate the zero-crossing phase of the three-phase current. Starting from the broken line moment, find the zero-crossing points of the three-phase current. Taking phase A as an example, when the following formula is satisfied, k is the required zero-crossing point. Find the zero-crossing points of phases B and C in the same way.

[0093]

[0094] Judge whether there are two-phase currents in antiphase, that is, whether the phase difference is . If there is a value of the change amount of two-phase currents near here, a deviation of 10° is set. If two-phase current in antiphase is detected, it is considered that a broken line fault has occurred, and calculate the line voltage amplitude difference between any two of the three-phase nodes (for example, ). If there is no two-phase current in antiphase, it is judged that there is no broken line fault.

[0095] Specifically, in some embodiments, the effective value of the line voltage can be obtained, and the line voltage amplitude can be calculated based on the effective value of the line voltage:

[0096]

[0097] Among them, represents the line voltage amplitude, represents the effective value of the line voltage.

[0098] As an alternative embodiment, an oscilloscope or other measuring device can also be used to directly measure the amplitude of the line voltage .

[0099] By calculating the line voltage amplitude during a power system fault and the line voltage amplitude before the fault, the line voltage amplitude difference can be calculated.

[0100] Calculate the line voltage amplitude difference between any two-phase nodes. After the open-circuit protection is activated, determine whether an open-circuit fault has occurred and determine the location of the open-circuit fault. If the following formula is satisfied, it is determined that the location of the open-circuit fault in the power system is on the power supply side of the power system (open circuit on the power supply side). If not, it is determined that an open circuit has occurred on the load side.

[0101] There exists any one item (for example, the third threshold), among which, represents the rated voltage of the line.

[0102] Report the fault information, and the algorithm ends.

[0103] A method and related device for detecting faults in a power system provided by this application. The method includes: calculating the positive-sequence current amplitude difference, negative-sequence current amplitude difference, zero-sequence current amplitude difference, and zero-sequence voltage amplitude difference of the three-phase nodes of the secondary device based on the instantaneous current value and voltage instantaneous value of the three-phase nodes of the primary device; determining whether an open-circuit fault has occurred in the power system based on the positive-sequence current amplitude difference and the negative-sequence current amplitude difference; when the open-circuit fault cannot be determined by the positive-sequence current amplitude difference and the negative-sequence current amplitude difference, determining whether an open-circuit fault has occurred in the power system based on the zero-sequence current amplitude difference and the zero-sequence voltage amplitude difference. The fault detection method of the primary and secondary device integration in this application can analyze whether a fault has occurred in the power system more comprehensively and accurately.

[0104] It should be noted that the method of the embodiment of this application can be executed by a single device, such as a computer or a server, etc. The method of this embodiment can also be applied to a distributed scenario and completed by multiple devices cooperating with each other. In this case of a distributed scenario, one of the multiple devices can only execute one or more steps of the method of the embodiment of this application, and these multiple devices will interact with each other to complete the described method.

[0105] It should be noted that some embodiments of the present application have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the above embodiments and still achieve the desired results. Additionally, the processes depicted in the drawings do not necessarily require the particular order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0106] Based on the same inventive concept, corresponding to any of the above-described method embodiments, the present application also provides a device for detecting faults in a power system.

[0107] Referring to Figure 3 , the device for detecting faults in a power system includes:

[0108] An acquisition module 301, configured to acquire the instantaneous current values and instantaneous voltage values of the three-phase nodes of the primary equipment in the power system.

[0109] A calculation module 302, configured to calculate the amplitude differences of positive-sequence currents, negative-sequence currents, zero-sequence currents, and the amplitude difference of zero-sequence voltages of the three-phase nodes of the secondary equipment according to the instantaneous current values and the instantaneous voltage values.

[0110] The calculation module 302 is further configured to:

[0111] Calculate the amplitudes of positive-sequence currents, negative-sequence currents, zero-sequence currents, and the amplitude of zero-sequence voltages of the three-phase nodes according to the instantaneous current values and the instantaneous voltage values;

[0112] Calculate the amplitude differences of positive-sequence currents, negative-sequence currents, zero-sequence currents, and the amplitude difference of zero-sequence voltages separated by one power frequency cycle according to the amplitudes of positive-sequence currents, negative-sequence currents, zero-sequence currents, and the amplitude of zero-sequence voltages.

[0113] A first detection module 303, configured to determine whether a disconnection fault occurs in the power system based on the amplitude differences of positive-sequence currents and negative-sequence currents.

[0114] The first detection module 303 is further configured to:

[0115] In response to the amplitude difference of positive-sequence currents being less than zero, the amplitude difference of negative-sequence currents being greater than zero, and the sum of the amplitude differences of multiple positive-sequence currents being greater than or equal to a first threshold, determine that a disconnection fault occurs in the power system.

[0116] The second detection module 304 is configured to determine whether a line break fault occurs in the power system according to the amplitude difference of the zero-sequence current and the amplitude difference of the zero-sequence voltage in response to the inability to determine the line break fault through the amplitude difference of the positive-sequence current and the amplitude difference of the negative-sequence current.

[0117] The second detection module 304 is further configured to:

[0118] In response to the amplitude difference of the zero-sequence current being greater than zero, the amplitude difference of the zero-sequence voltage being greater than zero, and the amplitude difference of the zero-sequence voltage being greater than or equal to the second threshold, determine that a line break fault occurs in the power system.

[0119] The second detection module 304 is configured to:

[0120] In response to the occurrence of a line break fault in the power system, determine the location where the line break fault occurs in the power system.

[0121] The second detection module 304 is further configured to:

[0122] In response to the occurrence of a line break fault in the power system, calculate the line voltage amplitude difference between any two-phase nodes among the three-phase nodes;

[0123] According to the line voltage amplitude difference, determine the location where the line break fault occurs in the power system.

[0124] The second detection module 304 is further configured to:

[0125] In response to the line voltage amplitude difference being less than or equal to the third threshold, determine that the location where the line break fault occurs in the power system is on the power supply side of the power system.

[0126] For the convenience of description, when describing the above device, various modules are described separately according to their functions. Of course, when implementing the present application, the functions of each module can be implemented in the same or multiple software and / or hardware.

[0127] The device in the above embodiment is used to implement the corresponding method for detecting faults in the power system in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiments, which will not be elaborated here.

[0128] Based on the same technical concept, corresponding to the method in any of the above embodiments, the present application further provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the method for detecting faults in the power system as described in any of the above embodiments.

[0129] Figure 4A schematic diagram of an exemplary electronic device according to an embodiment of the present application is shown. The device may include: a processor 1010, a memory 1020, an input / output interface 1030, a communication interface 1040, and a bus 1050. Among them, the processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040 are communicatively connected to each other inside the device through the bus 1050.

[0130] The processor 1010 may be implemented in the form of a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, etc., and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this specification.

[0131] The memory 1020 may be implemented in the form of a ROM (Read Only Memory), a RAM (Random Access Memory), a static storage device, a dynamic storage device, etc. The memory 1020 may store an operating system and other application programs. When implementing the technical solutions provided in the embodiments of this specification through software or firmware, the relevant program codes are stored in the memory 1020 and are called and executed by the processor 1010.

[0132] The input / output interface 1030 is used to connect to an input / output module to implement information input and output. The input / output module may be configured as a component in the device (not shown in the figure) or externally connected to the device to provide corresponding functions. Among them, the input device may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output device may include a display, a speaker, a vibrator, an indicator light, etc.

[0133] The communication interface 1040 is used to connect to a communication module (not shown in the figure) to implement communication interaction between this device and other devices. Among them, the communication module may implement communication in a wired manner (such as USB, network cable, etc.) or in a wireless manner (such as mobile network, WIFI, Bluetooth, etc.).

[0134] The bus 1050 includes a path for transmitting information between various components of the device (such as the processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040).

[0135] It should be noted that although the above device only shows the processor 1010, the memory 1020, the input / output interface 1030, the communication interface 1040, and the bus 1050, in the specific implementation process, the device may also include other components necessary for normal operation. In addition, those skilled in the art can understand that the above device may also only include the components necessary to implement the solution of the embodiments of this specification, and does not necessarily include all the components shown in the figure.

[0136] The electronic device in the above embodiment is used to implement the corresponding method for detecting faults in the power system in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiments, which will not be elaborated here.

[0137] Based on the same technical concept, corresponding to the method in any of the above embodiments, the present application also provides a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium stores computer instructions, and the computer instructions are used to cause the computer to execute the method for detecting faults in the power system as described in any of the foregoing embodiments.

[0138] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device.

[0139] The computer instructions stored in the storage medium of the above embodiment are used to cause the computer to execute the method for detecting faults in the power system as described in any of the foregoing embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be elaborated here.

[0140] Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is only exemplary, and is not intended to imply that the scope of the present application (including the claims) is limited to these examples; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the embodiments of the present application as described above, and they are not provided in detail for the sake of brevity.

[0141] In addition, for simplicity of explanation and discussion, and so as not to make the embodiments of the present application difficult to understand, well-known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the provided drawings. Further, the devices may be shown in block diagram form so as not to make the embodiments of the present application difficult to understand, and this also takes into account the fact that details of the implementation of these block diagram devices are highly dependent on the platform on which the embodiments of the present application are to be implemented (i.e., these details should be fully within the understanding of those skilled in the art). In cases where specific details (such as circuits) are set forth to describe exemplary embodiments of the present application, it will be apparent to those skilled in the art that the embodiments of the present application may be practiced without these specific details or with variations of these specific details. Accordingly, these descriptions should be regarded as illustrative rather than restrictive.

[0142] Although the present application has been described in connection with specific embodiments thereof, many alternatives, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description. For example, other memory architectures (such as dynamic RAM (DRAM)) may be used with the embodiments discussed.

[0143] Embodiments of the present application are intended to cover all such alternatives, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the embodiments of the present application shall be included within the protection scope of the present application.

Claims

1. A method for detecting a fault in an electric power system, comprising: Obtaining instantaneous current values ​​and instantaneous voltage values ​​of three-phase nodes of a primary device in the power system; Calculate the amplitude difference of the positive sequence current, the amplitude difference of the negative sequence current, the amplitude difference of the zero sequence current and the amplitude difference of the zero sequence voltage of the three-phase node of the secondary device according to the instantaneous value of the current and the instantaneous value of the voltage; Determining whether a line break fault occurs in the power system based on the amplitude difference of the positive sequence current and the amplitude difference of the negative sequence current; In response to the failure to determine a line break fault through the amplitude difference of the positive sequence current and the amplitude difference of the negative sequence current, determining whether a line break fault occurs in the power system according to the amplitude difference of the zero sequence current and the amplitude difference of the zero sequence voltage; The determining whether a line break fault occurs in the power system based on the amplitude difference of the positive sequence current and the amplitude difference of the negative sequence current further comprises: In response to the amplitude difference of the positive sequence current being less than zero, the amplitude difference of the negative sequence current being greater than zero, and the sum of the amplitude differences of a plurality of the positive sequence currents being greater than or equal to a first threshold, determining that a line disconnection fault occurs in the power system; Determining whether a line break fault occurs in the power system according to the amplitude difference of the zero-sequence current and the amplitude difference of the zero-sequence voltage further includes: In response to the amplitude difference of the zero-sequence current being greater than zero, the amplitude difference of the zero-sequence voltage being greater than zero, and the amplitude difference of the zero-sequence voltage being greater than or equal to a second threshold, it is determined that a line break fault occurs in the power system.

2. The method of claim 1, wherein: The step of calculating the amplitude difference of the positive sequence current, the amplitude difference of the negative sequence current, the amplitude difference of the zero sequence current and the amplitude difference of the zero sequence voltage of the three-phase node according to the instantaneous current value and the instantaneous voltage value further comprises: Calculating the amplitude of the positive-sequence current, the amplitude of the negative-sequence current, the amplitude of the zero-sequence current and the amplitude of the zero-sequence voltage of the three-phase node according to the instantaneous value of the current and the instantaneous value of the voltage; According to the amplitude of the positive-sequence current, the amplitude of the negative-sequence current, the amplitude of the zero-sequence current and the amplitude of the zero-sequence voltage, the amplitude difference of the positive-sequence current, the amplitude difference of the negative-sequence current, the amplitude difference of the zero-sequence current and the amplitude difference of the zero-sequence voltage at an interval of one power frequency cycle are calculated.

3. The method of claim 1, wherein: Determining whether a line disconnection fault occurs in the power system further comprises: In response to a line break fault occurring in the power system, a location where the line break fault occurs in the power system is determined.

4. The method of claim 3, wherein: In response to a line break fault occurring in the power system, determining a location where the line break fault occurs in the power system further comprises: In response to a line disconnection fault occurring in the power system, calculating a line voltage amplitude difference between any two phase nodes in the three-phase nodes; The location where the line disconnection fault occurs in the power system is determined according to the line voltage amplitude difference.

5. The method of claim 4, wherein: Determining the location where the power system has a line break fault according to the line voltage amplitude difference further comprises: In response to the line voltage amplitude difference being less than or equal to a third threshold, it is determined that a location where a line break fault occurs in the power system is on a power source side of the power system.

6. A device for detecting a fault in an electric power system, comprising: An acquisition module is configured to acquire instantaneous current values ​​and instantaneous voltage values ​​of three-phase nodes of a primary device in the power system; A calculation module is configured to calculate the amplitude difference of the positive sequence current, the amplitude difference of the negative sequence current, the amplitude difference of the zero sequence current and the amplitude difference of the zero sequence voltage of the three-phase node of the secondary device according to the instantaneous value of the current and the instantaneous value of the voltage; A first detection module is configured to determine whether a line break fault occurs in the power system based on the amplitude difference of the positive sequence current and the amplitude difference of the negative sequence current; a second detection module, configured to determine whether a line break fault occurs in the power system according to the amplitude difference of the zero-sequence current and the amplitude difference of the zero-sequence voltage in response to failure to determine a line break fault through the amplitude difference of the positive-sequence current and the amplitude difference of the negative-sequence current; The first detection module is further configured to: In response to the amplitude difference of the positive sequence current being less than zero, the amplitude difference of the negative sequence current being greater than zero, and the sum of the amplitude differences of a plurality of the positive sequence currents being greater than or equal to a first threshold, determining that a line disconnection fault occurs in the power system; The second detection module is further configured to: In response to the amplitude difference of the zero-sequence current being greater than zero, the amplitude difference of the zero-sequence voltage being greater than zero, and the amplitude difference of the zero-sequence voltage being greater than or equal to a second threshold, it is determined that a line break fault occurs in the power system.

7. The device according to claim 6, wherein: The computing module is further configured to: Calculating the amplitude of the positive-sequence current, the amplitude of the negative-sequence current, the amplitude of the zero-sequence current and the amplitude of the zero-sequence voltage of the three-phase node according to the instantaneous value of the current and the instantaneous value of the voltage; According to the amplitude of the positive-sequence current, the amplitude of the negative-sequence current, the amplitude of the zero-sequence current and the amplitude of the zero-sequence voltage, the amplitude difference of the positive-sequence current, the amplitude difference of the negative-sequence current, the amplitude difference of the zero-sequence current and the amplitude difference of the zero-sequence voltage at an interval of one power frequency cycle are calculated.

8. The device of claim 6, wherein: The second detection module is further configured to: In response to a line break fault occurring in the power system, a location where the line break fault occurs in the power system is determined.

9. The device of claim 8, wherein: The second detection module is further configured to: In response to a line disconnection fault occurring in the power system, calculating a line voltage amplitude difference between any two phase nodes in the three-phase nodes; The location where the line disconnection fault occurs in the power system is determined according to the line voltage amplitude difference.

10. The device of claim 9, wherein: The second detection module is further configured to: In response to the line voltage amplitude difference being less than or equal to a third threshold, it is determined that a location where a line break fault occurs in the power system is on a power source side of the power system.

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the method according to any one of claims 1 to 5 is implemented.

12. A non-transitory computer-readable storage medium storing computer instructions, wherein: The computer instructions are used to enable a computer to execute the method according to any one of claims 1 to 5.

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