Method for checking and treating three-phase imbalance of low-voltage transformer area

Abstract

The invention relates to the technical field of power system operation optimization, and discloses a low-voltage transformer area three-phase imbalance troubleshooting and treatment method, which comprises the steps of screening three-phase imbalance candidate transformer areas based on a voltage difference value, dividing time periods to judge a continuously unbalanced target transformer area, calculating a theoretical balance current value, and calculating the balance current value of the three-phase imbalance candidate transformer areas according to the theoretical balance current value. And formulating a load adjustment scheme with least changes through user current sorting and phase sequence matching, and finally controlling the three-phase current error within 10%. According to the method, the operation process is standardized, the treatment pertinence is high, and the problems of line loss increase, voltage quality reduction and the like caused by three-phase imbalance are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of operation and maintenance technology for low-voltage distribution areas in power systems, specifically to a method for investigating and managing three-phase imbalance. Background Technology

[0002] Three-phase imbalance is a common problem in low-voltage power distribution systems, especially in smaller distribution areas. Due to the randomness and diversity of user loads, as well as unreasonable initial phase allocation, uneven distribution of three-phase current is easily caused. Three-phase imbalance can lead to a series of adverse consequences: first, it increases line losses, resulting in wasted power resources; second, it causes excessive voltage deviation, affecting the quality of power supply for users; and third, it reduces the operating efficiency of transformers and other power equipment, shortening their service life.

[0003] Existing methods for managing three-phase imbalance largely rely on manual on-site inspections, which suffer from low inspection efficiency, poor targeting, and a lack of quantitative basis for management solutions. Some methods achieve dynamic adjustment by installing balancing devices, but these are costly and unsuitable for large-scale management of small transformer substations. Therefore, a standardized, easy-to-operate, and cost-controllable inspection and management method is needed to achieve accurate identification and efficient management of three-phase imbalance in low-voltage transformer substations.

[0004] CN110247408A discloses a demand response-based method for managing three-phase imbalance in distribution transformer areas, comprising the following steps: S1. Uncertainty PBDR modeling: Based on the relationship between user load changes and electricity price changes, and the uncertainty of demand response for different types of electricity prices, a PBDR model is established; S2. Establishing a three-phase imbalance optimization model for distribution transformer areas: Based on the expected three-phase electricity consumption, and with constraints including electricity price constraints, electricity user electricity consumption constraints, and electricity consumption satisfaction constraints, a three-phase imbalance optimization model for distribution transformer areas is established with the objective of minimizing the sum of squares of the differences between the daily expected three-phase electricity consumption and the average of the daily expected three-phase electricity consumption; S3. Solving the three-phase imbalance optimization model for distribution transformer areas using the clear equivalence method to obtain the phase-specific electricity prices and the expected three-phase electricity consumption; S4. Setting the three-phase electricity prices on a given day based on the solution results, thereby completing the three-phase imbalance management. However, the effectiveness of its investigation and management, the standardization of its operational procedures, and the targeted nature of its management need further improvement. Summary of the Invention

[0005] The purpose of this invention is to provide a method for investigating and treating three-phase imbalance in low-voltage distribution areas, which solves the problems of low investigation efficiency and insufficient targeted treatment in the existing technology, and realizes standardized investigation and precise treatment of three-phase imbalance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0007] A method for investigating and managing three-phase imbalance in low-voltage distribution areas, characterized by comprising the following steps:

[0008] Step 1: Acquire three-phase current signals through the data acquisition module, and store current data and user load information;

[0009] Step 2: Analyze the voltage difference in the target transformer area, verify the monitoring points, confirm the transformer area that needs to be addressed, and record the time period and phase of imbalance;

[0010] Step 3: Extract the current during the unbalanced period, calculate the average value, determine the theoretical target, and generate the optimal load adjustment scheme;

[0011] Step 4: Arrange and combine user currents, adjust phase sequence to ensure the error does not exceed 10%, and output the user list after phase separation.

[0012] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized in that the first step is used for distribution area screening. The specific method is as follows: collect all voltage data of this type of distribution area from the previous day. The voltage data is taken from the phase voltage at the low-voltage side outlet of the distribution area. The collection frequency is not less than once per hour to ensure complete data coverage. Screen the distribution areas where the voltage difference between any two phases (AB, AC, BC, BA, CA, CB) at the same time point exceeds the voltage difference threshold, mark them as distribution areas to be confirmed as unbalanced, and initially lock the range of distribution areas with abnormalities.

[0013] The above-described method for investigating and addressing three-phase imbalance in low-voltage distribution areas is characterized by the following step: Step 2 is used to confirm the unbalanced distribution area. The specific method is as follows: The voltage monitoring period of the candidate distribution area is divided into three typical periods: low period, flat period, and peak period. The voltage data of each typical period is analyzed. If there are at least 4 monitoring points in any period, and the interval between adjacent monitoring points does not exceed 2 hours, and there is a voltage difference threshold or higher between the same two phases in the same group of 4 monitoring points, it indicates that the imbalance in the distribution area is not an instantaneous phenomenon, but a continuous problem. It is determined to be a three-phase unbalanced distribution area that needs to be addressed. The corresponding unbalanced period and the specific unbalanced phase are recorded simultaneously to provide accurate basis for subsequent treatment.

[0014] The duration doesn't matter, as long as it's detected.

[0015] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized in that step 3 is used for load adjustment scheme formulation, specifically divided into: step 3.1 for theoretical target current calculation, step 3.2 for user current sequencing, step 3.3 for phase sequence confirmation, and step 3.4 for phase adjustment with minimal load changes.

[0016] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized in that step 3.1 involves extracting real-time current data for phases A, B, and C of the confirmed unbalanced distribution area during the unbalanced period. The average current value for each phase is calculated using the formula: "Average current value for each phase = Sum of all real-time currents during the unbalanced period for that phase / Number of data acquisitions." This average value reflects the reasonable current distribution benchmark for the distribution area under the current load level and serves as the theoretical target current value for three-phase balance. The calculation formula is:

[0017] ;

[0018] in, These are the average currents of phases A, B, and C during the unbalanced period, respectively.

[0019] The above-described method for investigating and managing three-phase imbalance in a low-voltage distribution area is characterized in that step 3.2 is as follows: during the imbalance period, real-time current data of all low-voltage users in the distribution area are obtained through a power acquisition system, and users corresponding to A, B, and C are sorted in descending or ascending order according to current magnitude to clarify the distribution of high-load and low-load users on each phase.

[0020] The method for investigating and managing three-phase imbalance in low-voltage distribution areas described above is characterized in that the specific method of step 3.3 is as follows: by using the "one distribution area, one index" module of the data acquisition system, the target distribution area is selected in the value assignment management function interface. Through the correlation between the daily theoretical line loss rate and the phase of the user access, the current phase sequence of each user is accurately confirmed, providing basic data for the phase adjustment of the user.

[0021] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized by the following specific method in step 3.4: Based on the core principle of "minimizing the use of user load," and ensuring that the sum of the total current of switched users does not exceed 5% of the total load of the distribution area, the current data of users with different phase sequences are arranged and combined to adjust some low-current users in high-load phases to low-load phases, so that the currents of phases A, B, and C after adjustment are close to the theoretical target currents, and the error between the three-phase currents does not exceed 10%. Finally, a detailed user phase adjustment list is output, clearly specifying the names of users requiring phase sequence switching, the original phase sequence, the target phase sequence, and the switching time window. The following optimization algorithm is used when generating the optimal load adjustment list:

[0022] Step 3.4.1: Initialization: Set the optimization objective to Minimize(N), where N is the number of users whose phases need to be adjusted. Set the constraint condition as: the adjusted three-phase current satisfy:

[0023] ;

[0024] Step 3.4.2: Sorting and candidate set construction: Sort the users on the unbalanced phase in descending order of current value to construct a candidate set of users to be adjusted;

[0025] Step 3.4.3: Iterative Search:

[0026] a. Let N=1, try to adjust the user with the largest current in the candidate set of phase A to the phase with the smallest current, calculate the three-phase current after adjustment, and determine whether the constraint conditions are met. If they are met, record the scheme.

[0027] b. If not satisfied, try combinations of N=2, and perform combination calculations and judgments;

[0028] c. Continue in this manner, gradually increasing N until a solution that satisfies the constraints is found.

[0029] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized in that step 4 is used for output and interaction. Specifically, the method is as follows: the solution with the smallest N value among all solutions that meet the conditions is output as the optimal solution. If there are multiple solutions with the same N value, the solution with the smallest total load adjustment is selected.

[0030] The present invention has the following main beneficial technical effects:

[0031] 1. Accurate and efficient investigation: Through the dual judgment mechanism of "voltage difference screening + time period verification", the system avoids misjudgment of instantaneous imbalance, accurately locates the transformer area with continuous three-phase imbalance, and improves the investigation efficiency.

[0032] 2. Targeted governance: Identify the unbalanced periods and phases, and combine user current sequencing and phase sequence confirmation to formulate adjustment plans with "minimum load changes" to reduce operating costs and impact on user electricity consumption.

[0033] 3. Stable balancing effect: Based on the theoretical target current, it ensures that the error of the three-phase current after adjustment is small, effectively reducing line loss, improving voltage quality, and improving the operating efficiency of the transformer area.

[0034] This invention features standardized operating procedures and targeted solutions, effectively reducing problems such as increased line losses and decreased voltage quality caused by three-phase imbalance. This invention can automatically and accurately investigate and resolve three-phase imbalance problems in distribution transformer areas. Attached Figure Description

[0035] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0037] refer to Figure 1 A method for investigating and managing three-phase imbalance in low-voltage distribution areas, characterized by comprising the following steps:

[0038] Step 1: Acquire three-phase current signals through the data acquisition module, and store current data and user load information;

[0039] Step 2: Analyze the voltage difference in the target transformer area, verify the monitoring points, confirm the transformer area that needs to be addressed, and record the time period and phase of imbalance;

[0040] Step 3: Extract the current during the unbalanced period, calculate the average value, determine the theoretical target, and generate the optimal load adjustment scheme;

[0041] Step 4: Arrange and combine user currents, adjust phase sequence to ensure the error does not exceed 10%, and output the user list after phase separation.

[0042] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized in that the first step is used for distribution area screening, and the specific method is as follows:

[0043] Collect all voltage data of this type of transformer substation from the previous day. The voltage data is taken from the phase voltage at the low-voltage side outlet of the substation, and the collection frequency is no less than once per hour to ensure complete data coverage. Select substations where the voltage difference between any two phases (AB, AC, BC, BA, CA, CB) exceeds 12V at the same time point and mark them as unbalanced substations to be confirmed, thus initially identifying the range of substations with abnormalities.

[0044] The preset voltage difference is called the voltage difference threshold, which can be dynamically configured and optimized. The pre-screening conditions (capacity 200kVA, average household capacity <1kVA) are designed to focus on residential areas and other transformer substations where imbalance problems are frequent, thereby improving the efficiency of investigation.

[0045] Average household capacity <1kVA ​​means that the average distribution transformer capacity allocated to each user is less than 1 kVA. A value that is too low indicates insufficient load capacity, which leads to low voltage.

[0046] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized in that step 2 is used to confirm the imbalanced distribution area, and the specific method is as follows:

[0047] To avoid misjudging transient imbalances, the voltage monitoring period for candidate transformer substations was divided into three typical periods: 0-8 AM (off-peak hours), 8-4 PM (normal hours), and 4 PM-12 AM (peak hours). Voltage data for each period was analyzed. If at least four monitoring points (with adjacent monitoring points no more than two hours apart) exist within any given period, and a voltage difference of 12V or higher is consistently observed between the same two phases at these four monitoring points, it indicates that the imbalance in the substation is not transient but a persistent problem. This substation is then identified as a three-phase imbalance substation requiring remediation. The corresponding imbalance period (e.g., imbalance during peak hours) and the specific imbalanced phase (e.g., excessive AC phase voltage difference) are recorded simultaneously to provide accurate data for subsequent remediation.

[0048] The requirement of "at least four time points" is to ensure the continuity of the imbalance problem and avoid false alarms caused by the instantaneous start-up and shutdown of large-capacity equipment. The time period division can be adjusted according to local load characteristics, such as dividing it into multiple time periods for analysis, including peak, flat, and valley periods.

[0049] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized in that step 3 is used for load adjustment scheme formulation, specifically divided into: step 3.1 for theoretical target current calculation, step 3.2 for user current sequencing, step 3.3 for phase sequence confirmation, and step 3.4 for phase adjustment with minimal load changes.

[0050] The method for investigating and managing three-phase imbalance in low-voltage distribution areas, as described above, is characterized in that step 3.1 involves extracting real-time current data for phases A, B, and C of the confirmed unbalanced distribution area during the unbalanced period. The average current value for each phase is calculated using the formula: "Average current value of each phase = Sum of all real-time currents during the unbalanced period of that phase / Number of data acquisitions." This average value reflects the reasonable current distribution benchmark for the distribution area under the current load level and serves as the theoretical target current value for three-phase balance. The calculation formula is:

[0051] ;

[0052] in, These are the average currents of phases A, B, and C during the unbalanced period, respectively.

[0053] The above-described method for investigating and managing three-phase imbalance in a low-voltage distribution area is characterized in that step 3.2 is as follows: during the imbalance period, real-time current data of all low-voltage users in the distribution area are obtained through a power acquisition system, and users corresponding to A, B, and C are sorted in descending or ascending order according to current magnitude to clarify the distribution of high-load and low-load users on each phase.

[0054] The above-described method for investigating and managing three-phase imbalance in low-voltage distribution areas is characterized in that step 3.3 is as follows: using the "one distribution area, one index" module of the data acquisition system, the target distribution area is selected in the value assignment management function interface. Through the correlation between the daily theoretical line loss rate and the phase of the user access, the current phase sequence (phase A, phase B, or phase C) of each user is accurately confirmed, providing basic data for the user's phase adjustment.

[0055] The method for investigating and managing three-phase imbalance in low-voltage distribution areas, as described above, is characterized by the following specific method in step 3.4: Adhering to the core principle of "minimizing user load mobilization," users with lower current values ​​are prioritized for phase sequence switching (to avoid increased operational complexity due to large-scale adjustments to high-load users), and ensuring that the total current of the switched users does not exceed 5% of the total load of the distribution area. By arranging and combining the current data of users with different phase sequences, some low-current users in high-load phases are adjusted to low-load phases, so that the currents of phases A, B, and C after adjustment are close to the theoretical target currents, and the error between the three-phase currents does not exceed 10%. Finally, a detailed user phase adjustment list is output, clearly specifying the names of users requiring phase sequence switching, the original phase sequence, the target phase sequence, and the switching time window. The following optimization algorithm can be used to generate the optimal load adjustment list:

[0056] Step 3.4.1: Initialization: Set the optimization objective to Minimize(N), where N is the number of users whose phases need to be adjusted. Set the constraint condition as: the adjusted three-phase current satisfy:

[0057] ;

[0058] Step 3.4.2: Sorting and candidate set construction: Sort the users on the unbalanced phase (such as phase A with the largest current) in descending order of current value to construct a candidate set of users to be adjusted; the method for determining other phases is the same.

[0059] Step 3.4.3: Iterative Search:

[0060] a. Let N=1, and try to adjust the user with the largest current in the candidate pool of phase A to the phase with the smallest current (such as phase C). Calculate the three-phase current after adjustment and determine whether the constraint conditions are met. If they are met, record the scheme; the method for determining other phases is the same.

[0061] b. If not satisfied, try combinations of N=2 (such as adjusting the largest and second largest users in phase A, or adjusting them to phases B and C respectively), and perform combination calculations and judgments; the method for determining other phases is the same;

[0062] c. Continue in this manner, gradually increasing N until a solution that satisfies the constraints is found.

[0063] The above-described method for troubleshooting and managing three-phase imbalance in low-voltage distribution areas is characterized in that step 4 is used for output and interaction. Specifically, the method is as follows: the solution with the smallest N value among all solutions that meet the conditions is output as the optimal solution. If there are multiple solutions with the same N value, the solution with the smallest total load adjustment can be selected. The generated adjustment list is output in the form of a visual report for operation and maintenance personnel to execute.

[0064] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for investigating and managing three-phase imbalance in low-voltage distribution areas, characterized in that, It includes the following steps: Step 1: Acquire three-phase current signals through the data acquisition module, and store current data and user load information; Step 2: Analyze the voltage difference in the target transformer area, verify the monitoring points, confirm the transformer area that needs to be addressed, and record the time period and phase of imbalance; Step 3: Extract the current during the unbalanced period, calculate the average value, determine the theoretical target, and generate the optimal load adjustment scheme; Step 4: Arrange and combine user currents, adjust phase sequence to ensure the error does not exceed 10%, and output the user list after phase separation.

2. The method for investigating and managing three-phase imbalance in a low-voltage distribution area according to claim 1, characterized in that, Step 1 is used for transformer area screening. The specific method is as follows: collect the full voltage data of this type of transformer area on the previous day. The voltage data is taken from the phase voltage at the low-voltage side outlet of the transformer area. The collection frequency is not less than once per hour to ensure complete data coverage. Screen the transformer areas where the voltage difference between any two phases at the same time point exceeds the voltage difference threshold and mark them as unbalanced transformer areas to be confirmed. This will initially lock down the range of transformer areas with abnormalities.

3. The method for investigating and managing three-phase imbalance in a low-voltage distribution area according to claim 1, characterized in that, Step 2 is used to confirm unbalanced transformer areas. The specific method is as follows: Divide the voltage monitoring period of the candidate transformer area into three typical periods: low period, flat period, and peak period. Analyze the voltage data of each typical period. If there are at least 4 monitoring points in any period, and the interval between adjacent monitoring points does not exceed 2 hours, and the same two phases in the same group of 4 monitoring points have a voltage difference threshold or above, it indicates that the imbalance of the transformer area is not an instantaneous phenomenon, but a continuous problem. It is determined to be a three-phase unbalanced transformer area that needs to be treated. At the same time, record the corresponding unbalanced period and the specific unbalanced phase to provide accurate basis for subsequent treatment.

4. The method for investigating and managing three-phase imbalance in a low-voltage distribution area according to claim 1, characterized in that, Step 3 is used for load adjustment scheme formulation, which is specifically divided into: Step 3.1 for theoretical target current calculation, Step 3.2 for user current sorting, Step 3.3 for phase sequence confirmation, and Step 3.4 for phase adjustment with minimal load changes.

5. The method for investigating and managing three-phase imbalance in a low-voltage distribution area according to claim 4, characterized in that, The specific method of step 3.1 is as follows: extract the real-time current data of the three phases A, B, and C of the unbalanced transformer area during the unbalanced period after confirmation, and calculate the average current of each phase according to the formula "average current of each phase = sum of all real-time currents during the unbalanced period of the phase / number of data acquisitions". This average value reflects the reasonable current distribution benchmark of the transformer area under the current load level and serves as the theoretical target current value for three-phase balance. Theoretical equilibrium target current value The calculation formula is: ； in, These are the average currents of phases A, B, and C during the unbalanced period, respectively.

6. The method for investigating and managing three-phase imbalance in a low-voltage distribution area according to claim 5, characterized in that, The specific method for step 3.2 is as follows: During the unbalanced period, real-time current data of all low-voltage users in the distribution area are obtained through the power acquisition system. Users corresponding to A, B, and C are sorted in descending or ascending order according to the current magnitude to clarify the distribution of high-load and low-load users on each phase.

7. The method for investigating and managing three-phase imbalance in a low-voltage distribution area according to claim 6, characterized in that, The specific method for step 3.3 is as follows: Using the "one station area, one index" module of the data acquisition system, enter the value assignment management function interface, select the target station area, and accurately confirm the current phase sequence of each user through the correlation between the daily theoretical line loss rate and the user access phase, so as to provide basic data for user phase adjustment.

8. The method for investigating and managing three-phase imbalance in a low-voltage distribution area according to claim 7, characterized in that, The specific method for step 3.4 is as follows: Adhering to the core principle of "minimizing user load usage," and ensuring that the total current of switched users does not exceed 5% of the total load of the distribution area, the current data of users with different phase sequences are arranged and combined to adjust some low-current users in high-load phases to low-load phases. This ensures that the currents of phases A, B, and C after adjustment are close to the theoretical target currents, and the error between the three-phase currents does not exceed 10%. Finally, a detailed user phase adjustment list is output, clearly specifying the names of users requiring phase sequence switching, the original phase sequence, the target phase sequence, and the switching time window. The following optimization algorithm is used to generate the optimal load adjustment list: Step 3.4.1: Initialization: Set the optimization objective to Minimize(N), where N is the number of users whose phases need to be adjusted. Set the constraint condition as: the adjusted three-phase current satisfy: ； Step 3.4.2: Sorting and candidate set construction: Sort the users on the unbalanced phase in descending order of current value to construct a candidate set of users to be adjusted; Step 3.4.3: Iterative Search: a. Let N=1, try to adjust the user with the largest current in the candidate set of phase A to the phase with the smallest current, calculate the three-phase current after adjustment, and determine whether the constraint conditions are met. If they are met, record the scheme. b. If not satisfied, try combinations of N=2, and perform combination calculations and judgments; c. Continue in this manner, gradually increasing N until a solution that satisfies the constraints is found.

9. A method for investigating and managing three-phase imbalance in a low-voltage distribution area according to claim 8, characterized in that, Step 4 is for output. The specific method is as follows: output the solution with the smallest N value among all the solutions that meet the conditions. If there are multiple solutions with the same N value, select the solution with the smallest total load adjustment.

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