Online monitoring method for operating state of secondary current loop neutral line, and system

Abstract

The present invention relates to the technical field of secondary device monitoring. Disclosed are an online monitoring method for an operating state of a secondary current loop neutral line, and a system. The method comprises: by using a high-precision sensor for collection and a composite filtering algorithm for processing, obtaining a secondary current fundamental component of each neutral line of a transformer substation which is not influenced by harmonic waves and transient states, and uploading the secondary current fundamental component to a protection information master station; retrieving originally configured access protection information master station information to obtain three-phase secondary current loop information of each bay of the transformer substation, summarizing secondary current information of all monitoring ranges, and performing grouping and classification marking on said information by transformer substation, bay and winding; and using the collection information for operation analysis, automatically identifying and confirming an operating state of the line, and on the basis of the operating state, calculating the outlier deviation linearity and the continuous dynamic trend deviation degree of each winding of each bay. The present invention solves the problem that intermittent faults in secondary current loop neutral lines are concealed and are not easily found, realizes comprehensive monitoring for the whole system, and can quickly and accurately position a specific winding and issue an abnormal early warning.

Description

A method and system for online monitoring of the operating status of the neutral line of a secondary current loop Technical Field

[0001] The present invention relates to the technical field of online monitoring, and in particular to a method and system for online monitoring the operating status of a neutral line of a secondary current loop. Background Art

[0002] In power system plants and substations, secondary equipment monitors, controls, and protects the operating status of primary equipment. Secondary current, serving as an analog input for secondary equipment, is crucially important for its accuracy and reliability. The secondary current circuit involves current transformers, local control cabinets, outdoor cables, secondary equipment terminals, and data acquisition circuits. It features complex wiring, numerous links, and hidden defects. Current secondary equipment lacks logic for identifying neutral line breaks. When a ground fault occurs in the power system, the current transformer's excitation current increases and saturates due to a loose connection or a break in the secondary circuit neutral line, further causing the relay protection equipment to lose selectivity. This can lead to serious consequences, such as false tripping for out-of-zone faults or refusal to trip for in-zone faults. Therefore, it is necessary to monitor and identify neutral line breaks to uncover potential neutral line break hazards in the secondary current circuit in advance and ensure safe and stable power grid operation.

[0003] At present, there are certain research and applications on monitoring methods for virtual connection or disconnection of neutral line in current secondary circuit, which mainly include the following categories:

[0004] The first is the harmonic analysis method. When the neutral line of the current secondary circuit is broken, the harmonic components in the current circuit will change. By monitoring the characteristics of higher harmonics, it is possible to sensitively determine whether the neutral line is broken. Patents with application numbers 202211596095.9 and 202110361366.1 respectively disclose methods for making judgments by detecting the changing characteristics of the third harmonic current in the neutral line current and the three-phase secondary current of lines A, B, and C, and the proportion of the second harmonic component. However, when a large number of new energy sources are connected or a system failure occurs, the harmonic characteristics within the system will change, which can easily lead to misjudgment. In addition, the acquisition of higher harmonics of the current also has high requirements for sampling frequency and accuracy.

[0005] The second is the out-of-zone fault analysis method. When a grounding fault occurs in the power system, the waveform characteristics of the protection elements outside the fault range are analyzed after activation in the faulty power grid area to determine whether the neutral line of the current loop is broken. Patent application number 202111317427.0 discloses a method for comparing and analyzing the waveform characteristics of two sets of protections when a fault occurs outside the line protection zone to determine whether the neutral line is broken. This method has high judgment accuracy, but it has the limitation that it can only detect power system faults. It cannot provide early warning before the system fault, which may cause accidents to occur during out-of-zone faults or in-zone faults. The monitoring effect of neutral line breakage is limited.

[0006] The third is the signal injection method, which adds an external signal to the secondary current loop to determine whether the neutral line is broken. Patent application number 200710062678.2 discloses a current injection type neutral line break detection method, which injects a weak current signal into the running secondary current loop. By monitoring the injected signal, the neutral line break of the system can be effectively detected. It has the judgment accuracy and sensitivity, but there is a great interference to the operation of the relay protection device, which may cause the relay protection device to operate incorrectly, and there are safety hazards.

[0007] In summary, from a practical application perspective, the following issues need to be addressed to monitor the virtual connection or disconnection of the neutral line in the secondary current circuit:

[0008] (1) Real-time, sensitive, and accurate identification of a loose connection or disconnection in the neutral line of the current secondary circuit. When the system is operating normally, the current on the neutral line of the current circuit is very small compared to the three-phase load currents of A, B, and C. The sensitivity and accuracy of the identification of loose connection or disconnection is necessary and important.

[0009] (2) Low current data acquisition requirements. When the system is operating normally, the neutral current of each interval is small, and data can be transmitted remotely while meeting the accuracy requirements. High-frequency sampling may increase the difficulty of data transmission and storage, and the installation difficulty of monitoring components after the functional requirements are increased.

[0010] (3) Avoid the impact of system harmonics and transient faults and improve anti-interference performance. When a large number of new energy sources are connected or a system fault occurs, the system will generate harmonic interference and transient components, which may cause significant interference in the judgment of false connections or disconnections, and may cause frequent false alarms in actual applications.

[0011] (4) Comprehensive monitoring and precise positioning. The grid has a large number of secondary current windings. When neutral line breaks occur in different windings, accurate and rapid identification and rectification of specific power stations, intervals, and winding breaks are crucial.

[0012] (5) Identification of the operating status of primary and secondary equipment. The current in the neutral line is closely related to the operating status of the equipment. If the disconnection is directly determined without considering the status of the primary and secondary equipment, a false connection or disconnection warning may be mistakenly issued.

[0013] When judging the unstable state of the secondary current circuit, the neutral line of the secondary current is not completely connected or broken. The secondary line connection may be in a disconnected and restored circulation state, and the time is uncertain. It may be in a normal state for a long time, making it difficult to judge.

[0014] Summary of the Invention

[0015] In view of the above existing problems, the present invention is proposed.

[0016] Therefore, the present invention provides an online monitoring method for the operating status of the neutral line of a secondary current loop, which can solve the problem in traditional technologies that the electric field strength of the measured object is weak and high-precision measurement is difficult.

[0017] To solve the above technical problems, the present invention provides the following technical solution: a method for online monitoring of the operating status of the neutral line of a secondary current loop, comprising:

[0018] Through high-precision sensor acquisition and composite filtering algorithm processing, the fundamental component of the secondary current of each neutral line in the substation, which is not affected by harmonics and transients, is obtained and sent to the protection information master station. The information of the original configuration access protection information master station is retrieved to obtain the three-phase secondary current circuit information of each interval of the substation, and all secondary current information in the monitoring range is summarized and grouped and classified by substation, interval, and winding. The collected information is used for calculation and analysis, first automatically identifying and confirming the operating status of the line, and then combining the operating status to calculate the outlier deviation linearity and continuous dynamic trend deviation of each winding in each interval.

[0019] As a preferred solution of the method for online monitoring of the operating status of the neutral line of a secondary current loop described in the present invention, wherein: the calling of the information of the original configuration access protection information master station includes obtaining the neutral line current information by installing an open-type high-precision micro current sensor on the neutral line of each winding secondary current. The accuracy of the neutral line current sampling data is milliampere level, and it is sent to the protection information master station after being processed by the information acquisition system; the information acquisition system refers to the hardware and software system installed at the plant station end, which is responsible for communicating with the accessed neutral line current online monitoring module and the integrated data module, and completing the collection, monitoring, data processing and remote transmission of relevant current information; the information acquisition system should include an acquisition unit responsible for collecting the neutral line current data of the secondary current loop of the terminal box, and transmitting The data transmission server, protocol converter, and wireless receiving convergence unit transmit the data sampled by the collection unit to the protection information master station through the production management area network, that is, using the enterprise's comprehensive business data network to interconnect with the relevant production management areas in other places and the partitions in each safety zone with a security level lower than that of the non-control area; the protection information master station refers to an information platform for the dispatching agency to carry out remote related business for the secondary equipment at the plant and station end, analyzes and processes the secondary current loop neutral line current data sent by the information collection system, determines whether the neutral line of the current loop has a virtual connection or a broken line, and issues abnormal alarm information; the information collection system filters the DC component and harmonic component in the secondary current loop through a composite filtering algorithm, and obtains the neutral line current fundamental component data for comprehensive analysis and calculation.

[0020] As a preferred solution of the method for online monitoring the operating status of the neutral line of a secondary current loop described in the present invention, wherein: the comprehensive analysis and calculation includes the following calculation formula, where I nc , I njis the real and imaginary parts of the fundamental current RMS converted to the complex plane, is the maximum current amplitude, ω is the AC current angular frequency, T is the AC current cycle, N is the number of sampling points in one cycle, i is the i-th sampling, I Ai is the i-th sampling value:

[0021] And calculate the effective amplitude of the fundamental wave of the neutral line current in each interval:

[0022] As a preferred solution of the method for online monitoring the operating status of the neutral line of a secondary current loop described in the present invention, the retrieval includes directly collecting and obtaining the A, B, and C three-phase current data of each interval relay protection device and fault filter device through the original configuration protection information substation in the station, transmitting it to the protection information master station, and uniformly collecting and processing it with the neutral line current data, and marking and confirming the corresponding interval of a certain substation as the first winding A, B, and C three-phase currents Ia1, Ib1, Ic1 and the neutral line current I 01 , the second winding A, B, C three-phase current Ia2, Ib2, Ic2 and the neutral line current I 02 Until the three-phase current Ia of winding A, B, and C i , Ib i 、Ic i and neutral current I 0i Within the global monitoring range, if the neutral line of any winding is loose or broken, the problem winding will be accurately located immediately after comprehensive analysis and calculation.

[0023] As a preferred embodiment of the method for online monitoring of the operating status of the neutral line of a secondary current circuit of the present invention, wherein: the operation and analysis using the collected information includes analyzing and calculating the current information after the protection information master station marks, and calculating the average value of the effective value of the fundamental component of the three-phase current within T1=1 minute. I a有 (t) is the effective value of the phase A current of the relevant protection device collected by the main station at time t, N1 is the number of sampling points for the telemetry information collected by the main station during this period, I b and I c The calculation method is the same as I a , and then use the following formula to determine the operating status of the line and the main transformer primary equipment, where In is the rated current of the secondary current of the interval:

[0024] When the line is not in operation or no-load state, the zero drift sampling requirement of the relay protection device and the fault recording device is not greater than 0.01In. At this time, no judgment is made on whether the neutral line of the current secondary circuit is loosely connected or broken. It is assumed that there is no abnormality in the neutral line at this time. When the line is in load operation state, the neutral line break judgment logic is entered.

[0025] As a preferred embodiment of the method for online monitoring of the operating status of the neutral line of a secondary current loop according to the present invention, wherein: the operation and analysis using the collected information also includes: using the neutral line current data of different windings at the same interval, based on the neutral line current sampling data I 01 , I 02 ...I 0n In order to improve the differentiation of broken windings, the composite outlier value of each winding is set to I lq :

[0026] Calculate the standard deviation σ of the neutral current of each winding:

[0027] According to the maximum outlier deviation, the correction coefficient ε is calculated:

[0028] The final protection information master station calculates the current outlier deviation linearity β of each winding neutral line when the branch neutral line is broken. i :

[0029] Among them, I 0i is the effective value of the fundamental component of the neutral current sampling of the i-th secondary winding, n is the number of neutral currents connected to the protection information master station in this interval, β i is the outlier deviation linearity of the neutral current of the i-th secondary winding.

[0030] Through statistical analysis and calculation, the non-broken phase β i The values ​​are all less than 0.9, the broken phases are all greater than 0.9 with a certain margin, and the reliability coefficient Krel is equal to 1.1, then the critical value K of the outlier linearity is set to 1; when the outlier linearity β i When β<1, the protection information master station initially determines that the neutral line of the winding is operating normally; when β i When ≥1, the protection information master station preliminarily determines that the neutral line of the winding is loosely connected or broken, and continues to perform logical judgment.

[0031] As a preferred solution of the online monitoring method for the operating status of the neutral line of a secondary current loop described in the present invention, wherein: the outlier deviation linearity and the continuous dynamic trend deviation include, by real-time collection of the neutral line milliampere current data on the same winding, based on the neutral line current sampling data I at different times 01, I 02 ...I 0n , perform the following operations:

[0032] By accurately monitoring the mA-level current of the neutral line of the secondary AC circuit in real time, collecting and recording data, and taking 200 milliseconds and 1 minute as the acquisition period, the average value of the neutral line current sampling I within the current 200 milliseconds and 1 minute is calculated and recorded respectively. mn and I dn 、Previous statistical period I mn1 and I dn1 、The first two statistical cycles I mn2 and I dn2 , ..., the first 10 statistical periods I mn10 and I dn10 , forming a historical database. When the neutral line current is greater than 2 times the minimum precision current, the average current value of each statistical period in the database is used for comparison to obtain the instantaneous dynamic trend deviation and the continuous dynamic trend deviation. Since this criterion responds suddenly when the line is broken, it will no longer respond after the neutral line is broken for more than the statistical period. Therefore, the protection information master station does not use this criterion alone to determine whether the neutral line is disconnected or broken. It is used as an auxiliary criterion for logical judgment. The formula is as follows:

[0033] Where, ρ mni and ρ dni They are the instantaneous dynamic trend deviation and continuous dynamic trend deviation of the neutral line current of the nth winding compared with the previous i statistical cycles, and the requirement is I mni or I dni Greater than twice the minimum precision current. Exit calculation when all comparison cycles are not satisfied.

[0034] Another object of the present invention is to provide an online monitoring system for the operating status of a secondary current loop neutral line, which can solve problems that cannot be solved in the prior art by implementing an online monitoring method for the operating status of a secondary current loop neutral line.

[0035] As a preferred solution of the non-contact micro-intelligent sensing optimization system for the secondary DC circuit potential described in the present invention, the system includes: a high-precision micro-current sensor for collecting current data of the neutral line of the current circuit; an information acquisition system for transmitting the neutral line current data to the protection information master station; the protection information master station for processing the data in the instructions or system programs; a comprehensive analysis module for analyzing and judging the disconnection situation and issuing an early warning; and an early warning module for issuing an early warning for the judged abnormal situation.

[0036] A computer device includes a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, it implements the steps of an online monitoring method for the operating status of a neutral line of a secondary current loop.

[0037] A computer-readable storage medium stores a computer program thereon, wherein when the computer program is executed by a processor, the computer program implements the steps of a method for online monitoring the operating status of a neutral line of a secondary current loop.

[0038] Beneficial effects of the present invention: The method of the present invention is based on the acquisition of neutral current data, and adopts high-precision micro-current sensors to non-contactly access the neutral lines of each compartment terminal box on the substation side. Under the premise of ensuring accuracy, it avoids the invasion of additional signals into the protection secondary current circuit, greatly improving the safety of the secondary equipment in operation. The present invention first calls the original three-phase current data of each compartment A, B, and C of the protection information master station, judges the operating interval of the interval, avoids the misjudgment of the secondary current circuit of the maintenance line or the no-load line being disconnected, and then further analyzes and judges the loaded operating line. The neutral current information collected by the homologous high-precision sensor is used to perform a high-sensitivity outlier deviation linearity algorithm to horizontally compare the deviations of each winding, calculate and screen out the windings with larger outlier deviation linearity, and then compare the winding continuous dynamic trend deviation algorithm vertically. Under the premise of ensuring sufficient sensitivity, double confirmation is performed, and at the same time, the accuracy of the neutral line virtual connection or disconnection judgment is guaranteed. Simultaneously, by applying the sensitive characteristics of the instantaneous dynamic trend deviation, the unstable state of the neutral line connection is perceived and judged, solving the problem that the neutral line of the secondary current circuit is intermittent and hidden and difficult to find. The present invention collects neutral current data and performs sampling processing through a comprehensive filtering algorithm. It only needs to apply the fundamental component of the current for analysis and calculation, thus realizing the low-current data collection and processing requirements of the monitoring module and the data processing module of the information acquisition system. And the use of the steady-state fundamental component for analysis avoids the harmonic interference generated by the large-scale access of new energy sources in the system or during transient faults, further ensuring the accuracy of the neutral line virtual connection or disconnection judgment. The present invention transmits the information to the protection information main station through the plant-side information substation, and performs comprehensive processing and analysis at the protection information main station, coordinates and dispatches, and centrally monitors all secondary current neutral lines within the entire dispatch range. By grouping and classifying each winding, it realizes comprehensive monitoring of the entire system, and can also quickly and accurately locate and issue abnormal warnings for a specific winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0040] FIG1 is a flow chart of a method for online monitoring of the operating status of a neutral line of a secondary current loop provided by an embodiment of the present invention.

[0041] FIG2 is a flow chart of an online monitoring system for the operating status of a neutral line of a secondary current loop provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0042] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0043] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0044] Example 1

[0045] 1 , which is a first embodiment of the present invention, provides an online monitoring method for the operating status of a neutral line of a secondary current loop, including:

[0046] S1: The fundamental component of the secondary current of each neutral line of the substation that is not affected by harmonics and transients is obtained through high-precision sensor collection and composite filtering algorithm processing, and is sent to the protection information master station.

[0047] The retrieving of the original configuration access protection information master station information includes obtaining neutral line current information by installing an open-type high-precision micro current sensor on the neutral line of each winding secondary current. The neutral line current sampling data has an accuracy of milliampere level and is sent to the protection information master station after processing by the information acquisition system.

[0048] The information collection system refers to the hardware and software system installed at the plant station end, which is responsible for communicating with the connected neutral current online monitoring module and integrated data module, and completing the collection, monitoring, data processing, and remote transmission of relevant current information; the information collection system should include a collection unit responsible for collecting the neutral current data of the secondary current circuit of the terminal box, a server for transmitting data, a protocol converter, and a wireless receiving and aggregation unit. The data sampled by the collection unit shall be sent to the protection information master station through the production management area network, that is, using the enterprise's integrated business data network to interconnect with the relevant production management areas in other places and the partitions in each safety zone with a security level lower than that of the non-control area.

[0049] The protection information master station refers to an information platform used by the dispatching agency to carry out remote related business for the secondary equipment at the plant end. It analyzes and processes the neutral line current data of the secondary current loop sent by the information acquisition system, determines whether there is a loose connection or a broken line in the neutral line of the current loop, and issues abnormal alarm information.

[0050] The information acquisition system filters the DC component and harmonic components in the secondary current loop through a composite filtering algorithm to obtain the fundamental component data of the neutral line current for comprehensive analysis and calculation.

[0051] The comprehensive analysis and calculation includes the following calculation formula: nc , I nj is the real and imaginary parts of the fundamental current RMS converted to the complex plane, is the maximum current amplitude, ω is the AC current angular frequency, T is the AC current cycle, N is the number of sampling points in one cycle, i is the i-th sampling, I Ai is the i-th sampling value:

[0052] And calculate the effective amplitude of the fundamental wave of the neutral line current in each interval:

[0053] S2: Retrieve the original configuration access protection information master station information to obtain the three-phase secondary current loop information of each bay of the substation, summarize all the secondary current information in the monitoring range, and group and classify it by substation, bay, and winding.

[0054] The retrieval includes directly collecting and acquiring the A, B, and C three-phase current data of each bay relay protection device and fault filter device through the original configuration protection information substation in the station, transmitting it to the protection information master station, and uniformly collecting and processing it with the neutral line current data. The corresponding bay of a substation is marked and confirmed as the first winding A, B, and C three-phase current Ia1, Ib1, Ic1 and the neutral line current I 01 , the second winding A, B, C three-phase current Ia2, Ib2, Ic2 and the neutral line current I 02 Until the three-phase current Ia of winding A, B, and Ci , Ib i 、Ic i and neutral current I 0i Within the global monitoring range, if the neutral line of any winding is loose or broken, the problem winding will be accurately located immediately after comprehensive analysis and calculation.

[0055] S3: Utilize the collected information for computational analysis, first automatically identify and confirm the operating status of the line, and then calculate the outlier deviation linearity and continuous dynamic trend deviation of each winding in each interval based on the operating status.

[0056] The calculation and analysis using the collected information includes analyzing and calculating the current information after the protection information master station marks, and calculating the average value of the three-phase current fundamental component effective value T1=1 minute. I a有 (t) is the effective value of the phase A current of the relevant protection device collected by the main station at time t, N1 is the number of sampling points for the telemetry information collected by the main station during this period, I b and I c The calculation method is the same as I a , and then use the following formula to determine the operating status of the line and the main transformer primary equipment, where In is the rated current of the secondary current of the interval:

[0057] When the line is not in operation or no-load state, the zero drift sampling requirement of the relay protection device and the fault recording device is not greater than 0.01In. At this time, no judgment is made on whether the neutral line of the current secondary circuit is loosely connected or broken. It is assumed that there is no abnormality in the neutral line at this time. When the line is in load operation state, the neutral line break judgment logic is entered.

[0058] The method of performing calculation and analysis using the collected information also includes: using the neutral line current data of different windings at the same interval, based on the neutral line current sampling data I 01 , I 02 ...I 0n In order to improve the differentiation of broken windings, the composite outlier value of each winding is set to I lq :

[0059] Calculate the standard deviation σ of the neutral current of each winding:

[0060] Under rated current conditions, the current amplitude error of the protection winding of the current transformer is no more than 3%, and the phase error is no more than 1°. The composite error of the open-type high-precision micro current sensor installed on the neutral line is no more than 5%. According to the various voltage levels of the grounding protection configured in the network, the number of protection windings used on site is in the range of 3-6. Considering that the effective sampling of the protection is no less than twice the minimum precision current, that is, greater than 2mA, the correction coefficient ε is calculated according to the maximum outlier deviation:

[0061] The final protection information master station calculates the current outlier deviation linearity β of each winding neutral line when the branch neutral line is broken. i :

[0062] Among them, I 0i is the effective value of the fundamental component of the neutral current sampling of the i-th secondary winding, n is the number of neutral currents connected to the protection information master station in this interval, β i is the outlier deviation linearity of the neutral current of the i-th secondary winding.

[0063] Through statistical analysis and calculation, the non-broken phase β i The values ​​are all less than 0.9, the broken phases are all greater than 0.9 with a certain margin, and the reliability coefficient Krel is equal to 1.1, then the critical value K of the outlier linearity is set to 1; when the outlier linearity β i When β<1, the protection information master station initially determines that the neutral line of the winding is operating normally; when β i When ≥1, the protection information master station preliminarily determines that the neutral line of the winding is loosely connected or broken, and continues to perform logical judgment.

[0064] The outlier linearity and continuous dynamic trend deviation include real-time acquisition of the neutral line milliampere current data on the same winding, and the neutral line current sampling data I at different times. 01 , I 02 ...I 0n , perform the following operations:

[0065] By accurately monitoring the mA-level current of the neutral line of the secondary AC circuit in real time, collecting and recording data, and taking 200 milliseconds and 1 minute as the acquisition period, the average value of the neutral line current sampling I within the current 200 milliseconds and 1 minute is calculated and recorded respectively. mn and I dn 、Previous statistical period I mn1 and I dn1 、The first two statistical cycles I mn2 and I dn2 , ..., the first 10 statistical periods I mn10 and I dn10, forming a historical database. When the neutral line current is greater than 2 times the minimum precision current, the average current value of each statistical period in the database is used for comparison to obtain the instantaneous dynamic trend deviation and the continuous dynamic trend deviation. Since this criterion responds suddenly when the line is broken, it will no longer respond after the neutral line is broken for more than the statistical period. Therefore, the protection information master station does not use this criterion alone to determine whether the neutral line is disconnected or broken. It is used as an auxiliary criterion for logical judgment. The formula is as follows:

[0066] Where, ρ mni and ρ dni They are the instantaneous dynamic trend deviation and continuous dynamic trend deviation of the neutral line current of the nth winding compared with the previous i statistical cycles, and the requirement is I mni or I dni Greater than twice the minimum precision current. Calculations are terminated when all comparison periods fail to meet the requirement. Based on current grid operation, without special operating conditions, the daily minimum load factor is approximately between 0.6 and 0.8. Power load changes are minimal within 10 minutes. When the neutral line breaks, the neutral current instantly drops to the zero-drift sampling value. The reliability coefficient, Krel', is assumed to be greater than 1.2, and the critical value for the dynamic trend deviation is 40%.

[0067] Compare the neutral point current data of a certain winding in the first ten cycles to obtain the continuous dynamic trend deviation data set ρ dn1 , ρ dn2 …、ρ dn10 , the dynamic trend deviation of the neutral current of any winding satisfies ρ dni When the value is less than 40%, the auxiliary judgment is that the neutral line of the winding is operating normally; when any one of the data groups ρ dni When ≥40%, it is auxiliary judged that the neutral line of the winding is loosely connected or broken.

[0068] When it is preliminarily determined that the neutral line of the winding is loosely connected or broken, the winding meets the continuous dynamic trend deviation criterion and an early warning of loose connection or broken neutral line of the secondary current circuit is immediately issued.

[0069] Compare the neutral point current data of a certain winding in the first ten cycles to obtain the instantaneous dynamic trend deviation data set ρ mn1 , ρ mn2 …、ρ mn10 , when the interval winding ρ mni ≥40% is judged as a transient abnormality of the neutral line. When the winding has three or more transient abnormal actions and restorations within one day, it is judged that the winding is in an unstable neutral line state, and an abnormal warning of the neutral line in the secondary current circuit is immediately issued.

[0070] Example 2

[0071] Referring to Figure 2, which is the second embodiment of the present invention, a non-contact micro-intelligent sensing optimization system for secondary DC circuit potential is provided, which includes a high-precision micro-current sensor for collecting current data of the neutral line of the current circuit; an information acquisition system for transmitting the neutral line current data to the protection information master station; the protection information master station for processing the data in the instructions or system programs; a comprehensive analysis module for analyzing and determining the disconnection situation and issuing an early warning; and an early warning module for issuing an early warning for the determined abnormal situation.

[0072] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0073] Example 3

[0074] The third embodiment of the present invention is different from the first two embodiments in that:

[0075] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0077] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiment of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal translation scripting language JavaScript, etc.

[0078] The present application is described with reference to the flow chart and / or block diagram of the method, device (system), and computer program product according to the embodiment of the present application. It should be understood that each flow process and / or box in the flow chart and / or block diagram and the combination of the flow process and / or box in the flow chart and / or block diagram can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processing machine or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one flow chart flow or multiple flows and / or one box or multiple boxes of the block diagram.

[0079] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0080] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0081] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0082] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

[0083] Example 4

[0084] The test steps are as follows:

[0085] Five data points were randomly selected within 10 minutes after the neutral line of a winding of a 220kV operating line in a substation was broken. All the current values ​​of the neutral line windings in this interval were sampled and the measured values ​​were recorded to form Data Table 1.

[0086] Table 1 Neutral point current data of each winding when the neutral point is broken

[0087] (1) Calculate the outlier linear deviation β of each winding at each moment i , and obtain the outlier linear deviation data table 2.

[0088] Table 2 Outlier linearity deviation data of each winding when the neutral point is broken

[0089] (2) Select the data collected 10 minutes before and after the neutral line of a substation's operating line is disconnected and the three-phase current and neutral line current of the no-load line are disconnected, and record the measured values ​​to form Data Table 3.

[0090] Table 3 Winding current test data 10 minutes before and after neutral line disconnection

[0091] Calculate the line operating status based on the three-phase currents A, B, and C. If In = 1A, then: I a >0.01In|I b >0.01In|I c >0.01In;

[0092] When the line is in operation, the continuous dynamic trend deviation of the winding at each moment is calculated to obtain the continuous dynamic trend deviation data table 4.

[0093] Table 4 Deviation of winding continuous dynamic trend when neutral line is broken

[0094] (4) Select the data collected 2 seconds before and after the neutral line of a substation's operating line is broken and the three-phase current and neutral line current of the no-load line are broken, and record the measured values ​​to form Data Table 5.

[0095] Table 5 Winding current test data 2s before and after neutral line disconnection

[0096] Calculate the dynamic trend deviation of the winding at each moment and obtain the dynamic trend deviation data table 6.

[0097] Table 6 Winding dynamic trend deviation when neutral line is broken

[0098] According to the experimental data and calculation results, it can be known that the line is first judged whether it is in operation. According to the experimental results, the line is operating normally and the protection master station system continues to judge the neutral point secondary current circuit.

[0099] When a protective neutral line of a 220kV line in a substation is broken, the deviation degree β4 of the interval winding outlier line is ≥ 1, and that of other windings is less than 1, which preliminarily determines that the neutral line of the secondary current of the winding is broken.

[0100] After the neutral line breaks, a sustained trend deviation analysis is performed. The calculated current average for this statistical cycle is 1.7 mA. Compared to the previous 10 cycles, the sustained trend deviation is greater than 40%, confirming a neutral line break in the secondary circuit and prompting the protection information master station to issue an early warning. Furthermore, the break determination criteria are met for the next 10 cycles. After 10 cycles, the current is less than twice the minimum precision current, and the determination logic is no longer entered.

[0101] If the protection neutral line is in an unstable state, the average current calculated in the cycle is 1.4mA, and the dynamic trend deviation compared with the previous 10 cycles is greater than 40%. If the same winding has three or more satisfied and unsatisfied judgment conversions within one day, the protection information master station will judge that the neutral line of the secondary circuit is in an unstable state, and the protection information master station will issue an early warning.

Claims

1. A method for online monitoring of the operating status of a neutral line of a secondary current loop, characterized in that: include, Through high-precision sensor acquisition and composite filtering algorithm processing, the fundamental component of the secondary current of each neutral line of the substation that is not affected by harmonics and transients is obtained and sent to the protection information master station; Retrieve the original configuration access protection information master station information to obtain the three-phase secondary current loop information of each bay of the substation, summarize all the secondary current information in the monitoring range, and group and classify it by substation, bay, and winding; The collected information is used for computational analysis to automatically identify and confirm the operating status of the line, and then the outlier deviation linearity and continuous dynamic trend deviation of each winding in each interval are calculated based on the operating status.

2. The method for online monitoring of the operating status of the neutral line of a secondary current loop according to claim 1, characterized in that: The retrieving the information of the protection information master station of the original configuration access includes obtaining the neutral line current information by installing an open-type high-precision micro current sensor on the neutral line of each winding secondary current, and the neutral line current sampling data accuracy is milliampere level, and is sent to the protection information master station after being processed by the information acquisition system; The information collection system refers to the hardware and software system installed at the plant station end, which is responsible for communicating with the connected neutral current online monitoring module and integrated data module, and completing the collection, monitoring, data processing and remote transmission of relevant current information; the information collection system should include a collection unit responsible for collecting the neutral current data of the secondary current loop of the terminal box, a server for transmitting data, a protocol converter, and a wireless receiving and convergence unit, and the data sampled by the collection unit is sent to the protection information master station through the production management area network, that is, using the enterprise comprehensive business data network to interconnect with the relevant production management areas in other places and the partitions in each safety area with a safety level lower than the non-control area; The protection information master station refers to an information platform for the dispatching organization to carry out remote related business for the secondary equipment at the plant and station end, which analyzes and processes the current data of the neutral line of the secondary current loop sent by the information collection system, determines whether there is a virtual connection or a disconnection in the neutral line of the current loop, and issues abnormal alarm information; The information acquisition system filters the DC component and harmonic component in the secondary current loop through a composite filtering algorithm to obtain the fundamental component data of the neutral line current for comprehensive analysis and calculation.

3. The method for online monitoring of the operating status of the neutral line of a secondary current loop according to claim 2, characterized in that: The comprehensive analysis and calculation includes the following calculation formula: nc ,I nj is the real and imaginary parts of the fundamental current effective value converted to the complex plane, is the maximum current amplitude, ω is the AC current angular frequency, T is the AC current cycle, N is the number of sampling points in one cycle, i is the i-th sampling, I Ai is the i-th sampling value: And calculate the effective amplitude of the fundamental wave of the neutral line current in each interval:

4. The method for online monitoring of the operating status of the neutral line of a secondary current loop according to claim 3, characterized in that: The retrieval includes directly collecting and acquiring the A, B, and C three-phase current data of each interval relay protection device and fault filter device through the original configuration protection information substation in the station, transmitting it to the protection information master station, and uniformly collecting and processing it with the neutral line current data, and marking and confirming the corresponding interval of a certain substation as the first winding A, B, C three-phase current Ia1, Ib1, Ic1 and the neutral line current I 01 , the second winding A, B, C three-phase current Ia2, Ib2, Ic2 and the neutral line current I 02 Until the three-phase current Ia of the i-th winding A, B, C i , Ib i 、Ic i and the neutral current I 0i Within the global monitoring range, if the neutral line of any winding is loosely connected or broken, the problematic winding will be accurately located immediately after comprehensive analysis and calculation.

5. The method for online monitoring of the operating status of the neutral line of a secondary current loop according to claim 4, characterized in that: The use of collected information for calculation and analysis includes using the current information processed by the protection information master station to analyze and calculate, by calculating the effective value of the fundamental component of the three-phase current T1 = the average value within 1 minute I a有 (t) is the effective value of the phase A current of the relevant protection device collected by the main station at time t, N1 is the number of sampling points for collecting telemetry information during this period, I b and I c The calculation method is the same as I a , and then use the following formula to calculate and determine the operating status of the line and the main transformer primary equipment, where In is the rated current of the secondary current of the interval: When the line is not in operation or no-load state, the zero drift sampling requirement of the relay protection device and the fault recording device is not greater than 0.01In. At this time, no judgment is made on whether the neutral line of the current secondary circuit is loosely connected or broken. It is assumed that there is no abnormality in the neutral line at this time. When the line is in load operation, the neutral line break judgment logic is entered.

6. The method for online monitoring of the operating status of the neutral line of a secondary current loop according to claim 5, characterized in that: The use of the collected information for calculation and analysis also includes: using the neutral line current data of different windings at the same interval, based on the neutral line current sampling data I 01 ,I 02 ……I 0n , n is the number of windings collected in this interval. To improve the differentiation of broken windings, the composite outlier value I of each winding is set lq : Calculate the standard deviation σ of the neutral current of each winding: According to the maximum outlier deviation, the correction coefficient ε is calculated: The final protection information master station calculates the current outlier deviation linearity β of each winding neutral line when there is a branch neutral line break i : Among them, I 0i is the effective value of the fundamental component of the neutral current sampled by the i-th secondary winding, n is the number of neutral currents connected to the protection information master station in this interval, β i is the outlier deviation linearity of the neutral current of the ith secondary winding; Through statistical analysis and calculation, the non-broken phase β i The values ​​are all less than 0.9, the broken phases are all greater than 0.9 with a certain margin, and the reliability coefficient Krel is taken as 1.1, then the critical value K of the outlier linearity is set as 1; when the outlier linearity β i When β is less than 1, the protection information master station initially determines that the neutral line of the winding is operating normally; i When ≥1, the protection information master station initially determines that the neutral line of the winding is loosely connected or broken, and continues to perform logical judgment.

7. The method for online monitoring of the operating status of the neutral line of a secondary current loop according to claim 6, characterized in that: The outlier deviation linearity and continuous dynamic trend deviation include: collecting the neutral line milliampere current data on the same winding in real time, based on the neutral line current sampling data I at different times 01 ,I 02 ……I 0n , perform the following operations: By accurately monitoring the milliampere current of the neutral line of the secondary AC circuit in real time, collecting and recording data, 200 milliseconds and 1 minute are the acquisition cycles. The average value of the neutral line current sampling I within 200 milliseconds and 1 minute is calculated and recorded respectively. mn and I dn 、Previous statistical period I mn1 and I dn1 、The first two statistical cycles I mn2 and I dn2 , ..., the first 10 statistical cycles I mn10 and I dn10 , forming a historical database. When the neutral line current is greater than 2 times the minimum precision current, the average current value of each statistical period in the database is used for comparison to obtain the instantaneous dynamic trend deviation and the continuous dynamic trend deviation. Since the criterion responds suddenly when the line is broken, it will no longer respond after the neutral line is broken for more than the statistical period. Therefore, the protection information master station does not use this criterion alone to judge whether the neutral line is virtual or broken. As a logic judgment auxiliary criterion, the formula is as follows: In the formula, and are the instantaneous dynamic trend deviation and continuous dynamic trend deviation of the neutral line current of the nth winding compared with the previous i statistical cycles, and the requirement is I mni or I dni Greater than twice the minimum precision current, the calculation will be exited when all comparison cycles are not satisfied.

8. A system using the method for online monitoring of the operating status of the neutral line of a secondary current loop as claimed in any one of claims 1 to 7, characterized in that: The system comprises, High-precision micro current sensor, used to collect current data of the neutral line of the current loop; Information collection system, used to transmit neutral line current data to the protection information master station; Protect the information master station, which is used to process the data in the instructions or system programs; Comprehensive analysis module, used to analyze and determine disconnection situations and issue warnings; The early warning module issues early warning for abnormal situations.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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