Transformer area low-voltage cause analysis method, device, equipment and medium

Abstract

The invention provides a transformer area low-voltage cause analysis method, device and equipment and a medium, and the method comprises the steps: collecting transformer area basic parameters and operation parameters; establishing a load flow calculation model containing the transformer area network topology; executing load flow calculation of the transformer area in the current state by using a conjugate gradient method to obtain voltage of each electrical endpoint of the transformer area, judging whether the voltage of each electrical endpoint is a low-voltage node or not, and calculating a low-voltage quantitative evaluation index of the low-voltage node of the transformer area in the current state; a traversal analysis method is adopted, factors closely related to low voltage are adjusted one by one, the transformer area low voltage indexes obtained when the factors are adjusted to corresponding standard required values are calculated, the difference values between the transformer area low voltage indexes and the low voltage quantitative evaluation indexes are calculated, and the factor with the minimum difference value is determined as the transformer area low voltage main cause. The problems that the power supply quality of a power distribution network is reduced and the service life of electric equipment is damaged due to the fact that low-voltage causes cannot be determined are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of safe power supply of distribution networks, and in particular to a method, device, equipment and medium for analyzing the causes of low voltage in a distribution network. Background Art

[0002] With the development of science and technology, people's living standards are constantly improving, and the number of various types of electrical equipment has increased significantly, which has directly caused the rapid growth of electricity load in various regions, exceeding the safe power supply capacity of the distribution network. The distribution network has shown more and more problems in the quality of power supply. As an important link directly facing users in the power system, the power supply quality of the distribution network directly affects the user's power experience and the normal operation of equipment. However, in the actual operation of the distribution network, low voltage problems often occur, resulting in a decline in the quality of the distribution network, which has many adverse effects on users and the power system. For the power system, low voltage will reduce the operating efficiency of the power grid, increase line losses, and may even cause power grid failures, affecting the safe and stable operation of the entire power system.

[0003] However, there are many causes of low voltage, and inaccurate understanding of these causes has greatly restricted the effectiveness and progress of low voltage management.

[0004] Therefore, it is urgent to propose a method for analyzing the causes of low voltage in the substation to solve the technical problem that the power supply quality of the distribution network is reduced due to the inability to clearly determine the causes of low voltage, which affects people's normal electricity use and damages the service life of electrical equipment. Summary of the invention

[0005] In order to overcome the problems existing in the related art, the present disclosure provides a method, device, equipment and medium for analyzing the causes of low voltage in a substation, so as to solve the technical problem in the related art that the power supply quality of the distribution network is reduced due to the inability to clearly determine the causes of low voltage, which affects people's normal electricity use and damages the service life of electrical equipment.

[0006] One or more embodiments of this specification provide a method for analyzing the causes of low voltage in a metro area, including the following steps:

[0007] Collect basic parameters and operation parameters of the substation area;

[0008] According to the basic parameters of the substation area and the operating parameters, a power flow calculation model including the substation area network topology is established;

[0009] Based on the power flow calculation model, the conjugate gradient method is used to perform power flow calculation of the substation in the current state, the voltage of each electrical terminal in the substation is obtained, whether the voltage of each electrical terminal is a low voltage node is determined, and the low voltage quantitative evaluation index of the low voltage node in the substation in the current state is calculated;

[0010] By adopting the ergodic analysis method, various factors closely related to low voltage are adjusted one by one until the voltage index returns to the standard requirement value. The low voltage index of the substation is calculated when each factor is adjusted to the corresponding standard requirement value. The difference between each substation low voltage index and the low voltage quantitative evaluation index is calculated, and the factor with the smallest difference among the differences is determined as the main cause of the low voltage in the substation.

[0011] Preferably, the various factors closely related to low voltage specifically include medium voltage line load rate, reactive power compensation, medium voltage line power supply range, ring network line connecting switch, three-phase voltage, distribution transformer capacity, substation power supply radius and load distribution.

[0012] Preferably, the method further comprises the following steps:

[0013] Make logical judgments and formulate treatment measures based on the main causes of low voltage in the substation area;

[0014] If the medium voltage line load rate is too high, new lines are used to split the load, reduce the line load rate, and reduce the line voltage drop;

[0015] If the reactive power demand is too large or the power factor is too low, a parallel reactive power compensation device is installed at the load position where the medium voltage line consumes more reactive power to achieve on-site reactive power compensation;

[0016] If the power supply range of medium voltage lines is relatively long, a medium voltage regulator or a controllable series compensation device is used to increase the voltage at the end of the line;

[0017] For the tie switch of the ring network line, if the tie switch is in the closed position, disconnect the tie switch;

[0018] For the three-phase voltage, analyze the three-phase load current and the regularity of the three-phase current changes over time. The three-phase load current should be adjusted by operation and maintenance means to achieve a balanced three-phase load current.

[0019] For the problem of heavy overload or failure of distribution transformer, new construction or replacement of larger distribution transformer is adopted;

[0020] If the power supply radius of the substation is too long, the new substation should be built in a "multi-point, small capacity" way to shorten the power supply radius;

[0021] For load distribution, if a single-phase line carries too much load, the single-phase line is changed to a three-phase four-wire power supply.

[0022] Preferably, the calculation of the low voltage quantitative evaluation index of the low voltage node in the substation under the current state specifically includes the following steps:

[0023] The low voltage quantitative evaluation index is a comprehensive index of the number of low voltage users and the low voltage jump lower limit of low voltage users, which is the cumulative sum of the low voltage jump lower limit of all low voltage users. It can be specifically expressed as:

[0024]

[0025] Among them, m is the number of low voltage nodes in the area, ΔU n is the low voltage jump lower limit of the nth low voltage node in the substation, n∈[1,m], n y is the number of users connected to the nth low-voltage node.

[0026] Preferably, the step of establishing a power flow calculation model including the substation network topology specifically includes the following steps:

[0027] Establish line models of three-phase four-wire and single-phase two-wire, single-phase and two-phase load types and three-phase load types of star and triangle connection, transformer model, voltage regulator model and load model, wherein the transformer and voltage regulator models include two П-type equivalent circuits of single-phase double winding and three-phase double winding;

[0028] The load model is converted into different types of endpoint injection currents, and the load access points and line branch nodes are combined to abstract the electrical endpoints;

[0029] A substation network topology with the transformer as the root node is formed according to the connection relationship and order between the electrical endpoints.

[0030] One or more embodiments of this specification provide a device for analyzing the causes of low voltage in a substation, including a parameter acquisition module, a model building module, an index calculation module, and a cause analysis module;

[0031] The parameter acquisition module is used to collect basic parameters and operating parameters of the substation area;

[0032] The model building module is used to establish a power flow calculation model including a substation network topology according to the substation basic parameters and the operating parameters;

[0033] The index calculation module is used to perform the power flow calculation of the substation in the current state by using the conjugate gradient method based on the power flow calculation model, obtain the voltage of each electrical terminal of the substation, determine whether the voltage of each electrical terminal is a low voltage node, and calculate the low voltage quantitative evaluation index of the low voltage node of the substation in the current state;

[0034] The cause analysis module is used to adopt the ergodic analysis method to adjust each factor closely related to low voltage one by one until the voltage index is restored to the standard requirement value, calculate the low voltage index of the substation when each factor is adjusted to the corresponding standard requirement value, calculate the difference between each substation low voltage index and the low voltage quantitative evaluation index, and determine the factor with the smallest difference as the main cause of the low voltage in the substation.

[0035] Preferably, the various factors closely related to low voltage specifically include medium voltage line load rate, reactive power compensation, medium voltage line power supply range, ring network line connecting switch, three-phase voltage, distribution transformer capacity, substation power supply radius and load distribution.

[0036] Preferably, it also includes a governance measure formulation module, which is used to make logical judgments and formulate governance measures based on the main causes of low voltage in the substation area;

[0037] If the medium voltage line load rate is too high, new lines are used to split the load, reduce the line load rate, and reduce the line voltage drop;

[0038] If the reactive power demand is too large or the power factor is too low, a parallel reactive power compensation device is installed at the load position where the medium voltage line consumes more reactive power to achieve on-site reactive power compensation;

[0039] If the power supply range of medium voltage lines is relatively long, a medium voltage regulator or a controllable series compensation device is used to increase the voltage at the end of the line;

[0040] For the tie switch of the ring network line, if the tie switch is in the closed position, disconnect the tie switch;

[0041] For the three-phase voltage, analyze the three-phase load current and the regularity of the three-phase current changes over time. The three-phase load current should be adjusted by operation and maintenance means to achieve a balanced three-phase load current.

[0042] For the problem of heavy overload or failure of distribution transformer, new construction or replacement of larger distribution transformer is adopted;

[0043] If the power supply radius of the substation is too long, the new substation should be built in a "multi-point, small capacity" way to shorten the power supply radius;

[0044] For load distribution, if a single-phase line carries too much load, the single-phase line is changed to a three-phase four-wire power supply.

[0045] One or more embodiments of the present specification provide a computer device, further comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned method for analyzing the causes of low voltage in a substation when executing the computer program.

[0046] One or more embodiments of the present specification provide a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the above-mentioned method for analyzing the causes of low voltage in a substation are implemented.

[0047] The present disclosure provides a method, device, equipment and medium for analyzing the causes of low voltage in a substation, which has the advantages that by collecting basic parameters and operating parameters of the substation, parameters affecting the causes of low voltage in the substation are collected as objects of cause analysis, and accurate data can be provided for cause analysis; a power flow calculation model including the substation network topology is established based on the basic parameters and operating parameters of the substation, and a power flow calculation model for calculating the steady-state operation state of the power system under given operating conditions is constructed through the collected parameters; based on the power flow calculation model, the conjugate gradient method is used to perform power flow calculation of the substation in the current state, the voltage of each electrical terminal of the substation is obtained, and it is judged whether the voltage of each electrical terminal is low Voltage node, calculate the low voltage quantitative evaluation index of the substation low voltage node in the current state, and judge whether each electrical endpoint is a low voltage node through calculation; adopt the ergodic analysis method to adjust each factor closely related to low voltage one by one until the voltage index is restored to the standard requirement value, and calculate the substation low voltage index when each factor is adjusted to the corresponding standard requirement value, calculate the difference between each substation low voltage index and the low voltage quantitative evaluation index, and obtain the factor with the smallest difference. The factor with the smallest difference in each difference is determined as the main cause of the low voltage in the substation, which can effectively analyze the specific problems of medium voltage line factors, distribution transformer factors, and internal factors of the substation, and obtain the precise cause of the low voltage problem in the substation. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0049] Figure 1 A schematic flow chart of a method for analyzing the causes of low voltage in a metro area provided in one or more embodiments of this specification;

[0050] Figure 2 A structural diagram of a device for analyzing the causes of low voltage in a metro area provided in one or more embodiments of this specification;

[0051] Figure 3 A schematic diagram of the structure of a computer device provided for one or more embodiments of this specification. DETAILED DESCRIPTION

[0052] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below in conjunction with the drawings in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the protection scope of the present invention.

[0053] The present invention is described in detail below in conjunction with specific implementation methods and the accompanying drawings.

[0054] Method Embodiment

[0055] According to an embodiment of the present invention, a method for analyzing the causes of low voltage in a transformer area is provided. Figure 1 As shown, it is a schematic diagram of the process flow of the method for analyzing the causes of low voltage in the metro area provided in this embodiment. The method for analyzing the causes of low voltage in the metro area according to the embodiment of the present invention comprises the following steps:

[0056] S1. Collect basic parameters and operating parameters of the substation from the power grid enterprise's energy management system, distribution automation system, metering automation, marketing system, distribution network planning system and other systems, including transformer and voltage regulator model, connection group, capacity and transformer gear number, line installation method (including overhead power lines and cable lines), model, length, number of phases, phase-to-phase distance and distance to the ground, capacitor compensation capacity, capacitor location and capacitor type, load quantity, load access point location and load type (single-phase, three-phase), etc.; transformer high-voltage side voltage, transformer and voltage regulator operating gear, grounding resistance value of each grounding point, capacitor switching status, load during typical peak load period (active, reactive), etc.

[0057] S2. According to the basic parameters of the substation and the operating parameters, a power flow calculation model including the substation network topology is established, wherein a three-phase four-wire and single-phase two-wire line model is established (the line model takes into account the influence of line mutual inductance and grounding resistance), single-phase and two-phase load types and three-phase load types of star and triangle connection, transformer and voltage regulator model, and load model. The transformer and voltage regulator model includes two types: single-phase double winding and three-phase double winding, which are П-type equivalent circuits, and non-standard transformation ratios are considered (the transformation ratio setting when the transformer tap voltage is adjusted is different from the standard rated voltage transformation ratio). The load model is ultimately reflected in different types of terminal injection currents; combined with the load access point and the line branch node, the electrical endpoint is abstracted, each electrical endpoint includes a, b, c, n three-phase nodes and a neutral node n, indicating the geographical location corresponding to the four electrical nodes, and the electrical endpoint does not consider the user's low-voltage household line; and according to the connection relationship and order between the electrical endpoints, the substation network topology with the transformer as the root node is formed (the network topology is actually a list of various models with the transformer as the root node).

[0058] S3. Based on the power flow calculation model, the conjugate gradient method is used to perform power flow calculation in the substation under the current state, and the voltage, current and power of each electrical terminal in the substation are obtained. It is determined whether the voltage of each electrical terminal is a low-voltage node. For a certain electrical terminal, if one or more of its three-phase voltages (Uan, Ubn or Ucn) is less than the allowable voltage lower limit, then the electrical terminal is a low-voltage node. The low-voltage quantitative evaluation index of the low-voltage node in the substation under the current state is calculated.

[0059] S4. Use the traversal analysis method to adjust each factor closely related to low voltage one by one until the voltage index returns to the standard requirement value (i.e. within the standard range of 235.4V to 198V), and calculate the low voltage index of the substation when each factor is adjusted to the corresponding standard requirement value. Calculate the difference between the low voltage index of each substation and the low voltage quantitative evaluation index, and obtain the factor with the smallest difference. This means that the more obvious the improvement in "low voltage" management is after adjusting the factor, the stronger the correlation between the factor and the low voltage in the substation. The factor with the smallest difference among the differences is determined as the main cause of the low voltage in the substation.

[0060] The method provided in this embodiment collects the basic parameters and operating parameters of the substation, collects the parameters that affect the cause of low voltage in the substation, and uses them as the object of cause analysis, so as to provide accurate data for cause analysis; according to the basic parameters and operating parameters of the substation, a power flow calculation model including the substation network topology is established, and a power flow calculation model for calculating the steady-state operation state of the power system under given operating conditions is constructed through the collected parameters; based on the power flow calculation model, the conjugate gradient method is used to perform power flow calculation of the substation in the current state, and the voltage, current and power of each electrical terminal of the substation are obtained, and it is judged whether the voltage of each electrical terminal is a low voltage node, and the current is calculated. The low voltage quantitative evaluation index of the low voltage node in the substation under the state is used to determine whether each electrical endpoint is a low voltage node through calculation; the ergodic analysis method is used to adjust each factor closely related to the low voltage one by one until the voltage index is restored to the standard requirement value, and the low voltage index of the substation when each factor is adjusted to the corresponding standard requirement value is calculated respectively, and the difference between each substation low voltage index and the low voltage quantitative evaluation index is calculated to obtain the factor with the smallest difference, and the factor with the smallest difference in each of the differences is determined as the main cause of the low voltage in the substation. The specific problems of medium voltage line factors, distribution transformer factors, and internal factors of the substation can be effectively analyzed, and the precise cause of the low voltage problem in the substation is obtained.

[0061] In one embodiment, the various factors closely related to low voltage specifically include medium voltage line load rate, reactive power compensation, medium voltage line power supply range, ring network line connecting switch, three-phase voltage, distribution transformer capacity, substation power supply radius and load distribution.

[0062] The method provided in this embodiment lists various factors closely related to low voltage to facilitate cause analysis and formulation of control measures.

[0063] In one embodiment, the following steps are also included:

[0064] According to the main causes of low voltage in the substation, logical judgment is made to formulate governance measures. Among them, if the load rate of medium-voltage lines is too high, new lines are used to split the load, reduce the line load rate, and reduce the line voltage drop.

[0065] If the reactive power demand is too large or the power factor is too low, a parallel reactive compensation device is installed at the load position where the medium-voltage line consumes more reactive power to realize on-site reactive power compensation; if the power supply range of the medium-voltage line is too long, a medium-voltage voltage regulator or a controllable series compensation device is used to increase the voltage at the end of the line; for the interconnecting switch of the ring network line, if the interconnecting switch is in the closed position, the interconnecting switch is disconnected; for the three-phase voltage, the three-phase load current is analyzed, and if the three-phase current changes regularly over time, the three-phase load current should be adjusted by operation and maintenance means to achieve a balanced effect; for the capacity overload or failure problem of the distribution transformer, a new distribution transformer is built or replaced with a larger one; for the long power supply radius of the substation, the new substation is built in accordance with the "multi-point, small capacity" method to shorten the power supply radius; for load distribution, if the single-phase line carries too much load, the single-phase line is changed to a three-phase four-wire for power supply.

[0066] The method provided in this embodiment can formulate effective solutions by accurately identifying the causes of the "low voltage" problem in the distribution area, so as to deeply solve the low voltage problem existing in the distribution network.

[0067] After the "low voltage" cause analysis and measures formulation system is put into operation, the "low voltage" problem area analysis results of each relevant unit are counted in the form of a list. Taking the #1 public transformer in a certain area as an example, the specific representations of the medium-voltage line factors, distribution transformer factors, and internal factors of the area can be derived. Based on the representation content, the system gives the cause analysis of the problem and formulates corresponding measures to guide the staff to solve it.

[0068] Table 1: Operation analysis results of the public transformer system in area #1 in a certain region

[0069]

[0070]

[0071] After systematic analysis, it was found that the "low voltage" problem in a certain substation was caused by the excessive reactive power transmission of the medium-voltage line of the #1 public transformer in the substation. It is recommended to install parallel capacitors at appropriate locations on the line for reactive power compensation to reduce the line voltage drop problem caused by the large amount of reactive power transmission.

[0072] In one embodiment, the calculation of the low voltage quantitative evaluation index of the low voltage node in the station area in the current state specifically includes the following steps:

[0073] The low voltage quantitative evaluation index is a comprehensive index of the number of low voltage users and the low voltage jump lower limit of low voltage users, which is the cumulative sum of the low voltage jump lower limit of all low voltage users. It can be specifically expressed as:

[0074]

[0075] Where m is the number of low voltage nodes in the substation area, which is determined according to the power flow calculation results; ΔU n is the low voltage jump lower limit of the nth low voltage node in the substation, n∈[1,m]; n y The number of users connected to the nth low-voltage node is determined according to the user access location and phase sequence relationship in the substation area; the low voltage jump lower limit refers to the difference between the actual voltage of the low-voltage node and the allowable voltage lower limit (according to the provisions of GB / T12325 "Power Quality Supply Voltage Deviation", the 220V single-phase power supply voltage deviation is 7% and -10% of the nominal voltage, that is, the allowable voltage lower limit is 220-220*10%=198V.

[0076] The method provided in this embodiment calculates the low voltage quantitative evaluation index according to the number of low voltage users and the low voltage jump lower limit of the low voltage users.

[0077] The following is a further explanation with a specific example:

[0078] A certain area is a Class B power supply zone. According to the relevant guidelines for the power system, the voltage drop of a 10 kV line should not exceed 5% (i.e., the difference between the first section voltage and the terminal voltage should not exceed 500V). At the same time, the power supply radius of a 0.4 kV line in a Class B power supply zone should not exceed 250m. A specific low voltage cause analysis and control measures system for the substation area includes the following steps:

[0079] Step 1: Collect the basic parameters and operating parameters of the typical "low voltage" area A in the power supply area from the power grid enterprise's energy management system, distribution automation system, metering automation, marketing system, distribution network planning system and other systems. And calculate the area low voltage index A0 without governance measures, that is,

[0080] The analysis system detects the "low voltage" substation that needs to be treated through the metering automation monitoring system. The judgment is based on the monitoring that there are 4 or more users in the substation with a voltage lower than 198V, and the cumulative duration exceeds 10 hours. At this time, it is automatically confirmed that the substation needs to carry out "low voltage" treatment.

[0081] Step 2: Construct the network topology of electrical components in area A and perform power flow calculation. Retrieve the lines to which area A belongs and determine whether there are other "low voltage" areas in the line that need to be managed. If so, it is because the line access area has a large load, resulting in "low voltage" in typical area A. Remove other "low voltage" areas and recalculate the low voltage index A1 of typical area A, that is, If not, the low voltage in the substation is caused by other problems. Proceed to the next step.

[0082] Step 3: According to the occurrence time of the "low voltage" problem area in the enterprise energy management system, investigate the load current of the line to which the area belongs during the time period, and combine the line current limit value data in the distribution network planning system to determine whether the line is heavily overloaded. If a heavy overload occurs, the line load rate is controlled within the standard range according to the line wiring method (the load rate of the single-tie / ring network line is controlled at 50%, and the load rate of the double-tie / double-ring network line is controlled at 75%), and then calculate the low voltage index A2 of area A under the standard line load rate, that is, If no severe overload occurs, the low voltage in the substation is caused by other problems. Proceed to the next step.

[0083] Step 4: The analysis system calls the active power and reactive power of the line where the "low voltage" problem area is located in the enterprise energy management system, and calculates according to the power factor formula to determine whether the line has excessive reactive power. If the calculated power factor is less than 0.92, it is considered that the cause of the "low voltage" problem is insufficient reactive power compensation. The line reactive power is compensated to 0.92, and then the low voltage index A3 of area A in this case is calculated, that is, If the power factor is greater than or equal to 0.92, the low voltage in the substation is caused by other problems, so proceed to the next step.

[0084] Step 5: The analysis system calls the enterprise energy management system to check whether the voltage drop of the line where the "low voltage" problem area is located exceeds 500V on that day. If it exceeds 500V, the power supply range of the line is too large. Correspondingly, the power supply range of the line is shortened to control the voltage drop within 500V. At the same time, the low voltage index A4 of area A in this case is calculated, that is, If it does not exceed 500V, it is low voltage in the substation caused by other problems. Proceed to the next step.

[0085] Step 6: The analysis system calls the current ring network line interconnection switch status of the line where the "low voltage" problem area is located in the distribution automation system. If the interconnection switch is in the closed position (the switch current is not 0), the low voltage is caused by the power supply transfer. The interconnection switch is disconnected and the low voltage index A5 of area A is recalculated, that is, Otherwise, the low voltage in the substation is caused by other problems. Please proceed to the next step.

[0086] Step 7: The analysis system calls the three-phase voltage at the head end of the "low voltage" problem area in the metering automation system; determines the voltage difference of the three-phase voltage at each moment. If the voltage difference of 20 or more consecutive measuring points exceeds 5V, it is caused by unbalanced three-phase voltage. Adjust the three-phase voltage of the area to balance and recalculate the low voltage index A6 of area A, that is, Otherwise, the low voltage in the substation is caused by other problems. Please proceed to the next step.

[0087] Step 8: The analysis system calls the load rate of the distribution transformer in the "low voltage" problem area and the voltage at the head end of the area in the metering automation system; determines whether the load rate exceeds 80%. If it exceeds, it is caused by the high load rate. Increase the capacity of the distribution transformer, control the load rate within 80%, and recalculate the low voltage index A7 of area A, that is, Otherwise, the low voltage in the substation is caused by other problems. Please proceed to the next step.

[0088] Step 9: The analysis system calls the power supply radius of the "low voltage" area in the low voltage area of ​​the distribution network planning system and makes a judgment. If it exceeds 250m, it is caused by the long power supply radius. Correspondingly, the power supply radius of the area is controlled within 250m, and the low voltage index A8 of area A is recalculated, that is, Otherwise, the low voltage in the substation is caused by other problems. Please proceed to the next step.

[0089] Step 10: The analysis system calls the phase sequence of "low voltage" users in the metering automation system and performs statistical analysis to calculate the number of A-phase, B-phase, and C-phase users in the "low voltage" users. If a phase accounts for more than 50%, it is considered that the low voltage is caused by excessive load on the single-phase line. The load is redistributed to the substation to ensure that the load of each phase does not exceed 50%, and the low voltage index A9 of substation A is recalculated, that is, Otherwise, the low voltage in the substation is caused by other problems. Please proceed to the next step.

[0090] The A1~A9 obtained by the above calculation are respectively calculated with A0 to obtain A 1～0 ~A 9～0 , and then take the absolute value for difference comparison. The larger the difference, the more it means that the low voltage in the substation is mainly caused by the corresponding indicator, and the corresponding improvement indicator is.

[0091] Based on the logical judgment and analysis of the cause of the "low voltage" problem, the system can ultimately determine the cause of the problem and formulate measures.

[0092] In terms of medium-voltage line problems, if the load rate of the medium-voltage line is too high, new lines should be used to split the load, reduce the line load rate, and reduce the line voltage drop; if the reactive power demand is too large or the power factor is too low, it is recommended to install parallel reactive compensation devices at the load positions where the medium-voltage line consumes more reactive power, so as to achieve on-site reactive power compensation and avoid reactive power flowing over long distances in the line; if the power supply radius of the medium-voltage line is too long, it is recommended to use a medium-voltage voltage regulator or a controllable series compensation device to increase the voltage at the end of the line; for the "low voltage" problem caused by the power transfer operation mode, the line operation mode should be reasonably optimized to avoid long-term power transfer operation. For lines with other problems, it is necessary to combine the annual planning work to plan distribution network improvement projects to improve the effective power transfer capacity of the line.

[0093] Regarding the internal problems of the low-voltage substation, if the power supply radius of the substation is too long, the "multi-point, small capacity" approach should be followed to shorten the power supply radius; in the case of excessive load on a single-phase line, the single-phase line should be changed to a three-phase four-wire line for power supply; the three-phase imbalance problem in the substation requires analysis of the three-phase load current. If the three-phase current changes regularly over time, the three-phase load current should be adjusted using operation and maintenance methods to achieve a balanced three-phase load current.

[0094] For distribution transformer problems, if the distribution transformer is overloaded or faulty, new construction or replacement of a larger distribution transformer should be adopted; if the gear is too low, power outage should be used to adjust the transformer gear. Other problems require on-site verification by relevant personnel.

[0095] At the same time, with the implementation of the national new energy strategy of "carbon neutrality and carbon peak", county-wide photovoltaic pilot projects are continuously being implemented in rural areas. Power supply units must guide the deployment of rooftop photovoltaic power generation facilities and the installation of distributed energy storage devices in combination with the "low voltage" and heavy overload problems in low-voltage areas to comprehensively improve the voltage quality of rural distribution networks.

[0096] Device Embodiment

[0097] According to an embodiment of the present invention, a device for analyzing the causes of low voltage in a substation is provided. Figure 2 As shown, it is a structural diagram of the low voltage cause analysis of the substation provided in this embodiment. The low voltage cause analysis device of the substation according to the embodiment of the present invention includes a parameter acquisition module 21, a model construction module 22, an indicator calculation module 23 and a cause analysis module 24.

[0098] The parameter acquisition module 21 is used to collect the basic parameters and operation parameters of the substation.

[0099] The model building module 22 is used to establish a power flow calculation model including the substation network topology according to the substation basic parameters and the operating parameters, wherein a three-phase four-wire and single-phase two-wire line model is established (the line model takes into account the influence of line mutual inductance and grounding resistance), single-phase and two-phase load types and three-phase load types of star and triangle connection, transformer and voltage regulator model, and load model. The transformer and voltage regulator model includes two types: single-phase double winding and three-phase double winding, which are П-type equivalent circuits, and non-standard transformation ratios are considered (the transformation ratio setting when the transformer tap voltage is adjusted is different from the standard rated voltage transformation ratio). The load model is ultimately reflected in different types of endpoint injection currents; combining the load access points and line branch nodes, electrical endpoints are abstracted, each electrical endpoint includes three-phase nodes a, b, c, n and a neutral node n, representing the geographical locations corresponding to the four electrical nodes, and the electrical endpoints do not consider the user's low-voltage household lines; and based on the connection relationship and order between the electrical endpoints, a substation network topology with the transformer as the root node is formed (the network topology is actually a list of various models with the transformer as the root node).

[0100] The index calculation module 23 is used to perform the current flow calculation of the substation in the current state based on the current flow calculation model and the conjugate gradient method to obtain the voltage, current and power of each electrical terminal in the substation, determine whether the voltage of each electrical terminal is a low voltage node, and calculate the low voltage quantitative evaluation index of the low voltage node in the substation in the current state.

[0101] The cause analysis module 24 is used to use the traversal analysis method to adjust each factor closely related to low voltage one by one until the voltage index is restored to the standard requirement value, calculate the low voltage index of the substation when each factor is adjusted to the corresponding standard requirement value, calculate the difference between each substation low voltage index and the low voltage quantitative evaluation index, obtain the factor with the smallest difference, and determine the factor with the smallest difference as the main cause of the low voltage in the substation.

[0102] The device provided in this embodiment collects the basic parameters and operating parameters of the substation through the parameter acquisition module 21, collects the parameters that affect the cause of low voltage in the substation, and uses them as the object of cause analysis, so as to provide accurate data for cause analysis; the model construction module 22 establishes a power flow calculation model including the substation network topology according to the basic parameters and operating parameters of the substation, and constructs a power flow calculation model for calculating the steady-state operation state of the power system under given operating conditions through the collected parameters; the index calculation module 23 performs the power flow calculation of the substation in the current state by using the conjugate gradient method based on the power flow calculation model, obtains the voltage, current and power of each electrical terminal in the substation, and judges whether the voltage of each electrical terminal is low voltage. The low voltage node is calculated, and the low voltage quantitative evaluation index of the low voltage node in the substation under the current state is calculated, and it is determined by calculation whether each electrical endpoint is a low voltage node; the cause analysis module 24 adopts the traversal analysis method to adjust each factor closely related to the low voltage one by one until the voltage index is restored to the standard requirement value, and respectively calculates the low voltage index of the substation when each factor is adjusted to the corresponding standard requirement value, calculates the difference between each substation low voltage index and the low voltage quantitative evaluation index, and obtains the factor with the smallest difference. The factor with the smallest difference in each of the differences is determined as the main cause of the low voltage in the substation, which can effectively analyze the specific problems of medium voltage line factors, distribution transformer factors, and internal factors of the substation, and obtain the precise cause of the low voltage problem in the substation.

[0103] In one embodiment, the various factors closely related to low voltage specifically include medium voltage line load rate, reactive power compensation, medium voltage line power supply range, ring network line connecting switch, three-phase voltage, distribution transformer capacity, substation power supply radius and load distribution.

[0104] The device provided in this embodiment lists various factors closely related to low voltage to facilitate cause analysis and formulation of control measures.

[0105] In one embodiment, it also includes a governance measure formulation module, which is used to make logical judgments and formulate governance measures based on the main causes of low voltage in the substation area; if the load rate of the medium-voltage line is too high, a new line is used to split the load, reduce the line load rate, and reduce the line voltage drop; if the reactive power demand is too large or the power factor is too low, a parallel reactive power compensation device is installed at the load position where the medium-voltage line consumes more reactive power to achieve on-site reactive power compensation; if the power supply range of the medium-voltage line is too long, a medium-voltage regulator or a controllable series compensation device is used to increase the voltage at the end of the line; For the interconnecting switch of the ring network line, if the interconnecting switch is in the closed position, disconnect the interconnecting switch; for the three-phase voltage, analyze the three-phase load current. If the three-phase current changes regularly over time, the operation and maintenance means should be used to adjust the three-phase load current so that the three-phase load current reaches a balanced effect; for the capacity overload or failure problem of the distribution transformer, a new distribution transformer should be built or replaced with a larger one; for the long power supply radius of the substation, follow the "multi-point, small capacity" method of building a new substation to shorten the power supply radius; for load distribution, if the single-phase line carries too much load, the single-phase line should be changed to a three-phase four-wire for power supply.

[0106] The device provided in this embodiment and the control measures formulation module can formulate effective solutions by accurately identifying the causes of the "low voltage" problem in the substation, so as to deeply solve the low voltage problem in the distribution network.

[0107] The embodiment of the present invention is an apparatus embodiment corresponding to the above-mentioned method embodiment. The specific operations of the processing steps of each module can be understood by referring to the description of the method embodiment, which will not be repeated here.

[0108] like Figure 3 As shown, the present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the method for analyzing the cause of low voltage in the substation in the above embodiment is implemented, or when the computer program is executed by a processor, the method for analyzing the cause of low voltage in the substation in the above embodiment is implemented.

[0109] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing related hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0110] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and the contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for analyzing the causes of low voltage in a substation, characterized in that: The following steps are involved: Collect basic parameters and operation parameters of the substation area; According to the basic parameters of the substation area and the operating parameters, a power flow calculation model including the substation area network topology is established; Based on the power flow calculation model, the conjugate gradient method is used to perform power flow calculation of the substation in the current state, the voltage of each electrical terminal in the substation is obtained, whether the voltage of each electrical terminal is a low voltage node is determined, and the low voltage quantitative evaluation index of the low voltage node in the substation in the current state is calculated; By adopting the ergodic analysis method, various factors closely related to low voltage are adjusted one by one until the voltage index returns to the standard requirement value. The low voltage index of the substation is calculated when each factor is adjusted to the corresponding standard requirement value. The difference between each substation low voltage index and the low voltage quantitative evaluation index is calculated, and the factor with the smallest difference among the differences is determined as the main cause of the low voltage in the substation.

2. The method for analyzing the causes of low voltage in a substation according to claim 1, characterized in that: The factors closely related to low voltage specifically include medium voltage line load rate, reactive power compensation, medium voltage line power supply range, ring network line interconnection switch, three-phase voltage, distribution transformer capacity, substation power supply radius and load distribution.

3. The method for analyzing the causes of low voltage in a substation according to claim 2, characterized in that: The following steps are also included: Make logical judgments and formulate treatment measures based on the main causes of low voltage in the substation area; If the medium voltage line load rate is too high, new lines are used to split the load, reduce the line load rate, and reduce the line voltage drop; If the reactive power demand is too large or the power factor is too low, a parallel reactive power compensation device is installed at the load position where the medium voltage line consumes more reactive power to achieve on-site reactive power compensation; If the power supply range of medium voltage lines is relatively long, a medium voltage regulator or a controllable series compensation device is used to increase the voltage at the end of the line; For the tie switch of the ring network line, if the tie switch is in the closed position, disconnect the tie switch; For the three-phase voltage, analyze the three-phase load current and the regularity of the three-phase current changes over time. The three-phase load current should be adjusted by operation and maintenance means to achieve a balanced three-phase load current. For the problem of heavy overload or failure of distribution transformer, new construction or replacement of larger distribution transformer is adopted; If the power supply radius of the substation is too long, the new substation should be built in a "multi-point, small capacity" way to shorten the power supply radius; For load distribution, if a single-phase line carries too much load, the single-phase line is changed to a three-phase four-wire power supply.

4. The method for analyzing the causes of low voltage in a substation according to claim 1, characterized in that: The calculation of the low voltage quantitative evaluation index of the low voltage node in the substation under the current state specifically includes the following steps: The low voltage quantitative evaluation index is a comprehensive index of the number of low voltage users and the low voltage jump lower limit of low voltage users, which is the cumulative sum of the low voltage jump lower limit of all low voltage users. It can be specifically expressed as: Among them, m is the number of low voltage nodes in the area, ΔU n is the low voltage jump lower limit of the nth low voltage node in the substation, n∈[1,m], n y is the number of users connected to the nth low-voltage node.

5. The method for analyzing the causes of low voltage in a substation according to claim 1, characterized in that: The establishment of a power flow calculation model including the substation network topology specifically includes the following steps: Establish line models of three-phase four-wire and single-phase two-wire, single-phase and two-phase load types and three-phase load types of star and triangle connection, transformer model, voltage regulator model and load model, wherein the transformer and voltage regulator models include two П-type equivalent circuits of single-phase double winding and three-phase double winding; The load model is converted into different types of endpoint injection currents, and the load access points and line branch nodes are combined to abstract the electrical endpoints; A substation network topology with the transformer as the root node is formed according to the connection relationship and order between the electrical endpoints.

6. A device for analyzing the causes of low voltage in a substation, characterized in that: It includes parameter acquisition module, model building module, indicator calculation module and cause analysis module; The parameter acquisition module is used to collect basic parameters and operating parameters of the substation area; The model building module is used to establish a power flow calculation model including a substation network topology according to the substation basic parameters and the operating parameters; The index calculation module is used to perform the power flow calculation of the substation in the current state by using the conjugate gradient method based on the power flow calculation model, obtain the voltage of each electrical terminal of the substation, determine whether the voltage of each electrical terminal is a low voltage node, and calculate the low voltage quantitative evaluation index of the low voltage node of the substation in the current state; The cause analysis module is used to adopt the ergodic analysis method to adjust each factor closely related to low voltage one by one until the voltage index is restored to the standard requirement value, calculate the low voltage index of the substation when each factor is adjusted to the corresponding standard requirement value, calculate the difference between each substation low voltage index and the low voltage quantitative evaluation index, and determine the factor with the smallest difference as the main cause of the low voltage in the substation.

7. The device for analyzing the cause of low voltage in a substation according to claim 6, characterized in that: The factors closely related to low voltage specifically include medium voltage line load rate, reactive power compensation, medium voltage line power supply range, ring network line interconnection switch, three-phase voltage, distribution transformer capacity, substation power supply radius and load distribution.

8. The device for analyzing the cause of low voltage in a substation according to claim 7, characterized in that: It also includes a governance measure formulation module, which is used to make logical judgments and formulate governance measures based on the main causes of low voltage in the substation area; If the medium voltage line load rate is too high, new lines are used to split the load, reduce the line load rate, and reduce the line voltage drop; If the reactive power demand is too large or the power factor is too low, a parallel reactive power compensation device is installed at the load position where the medium voltage line consumes more reactive power to achieve on-site reactive power compensation; If the power supply range of medium voltage lines is relatively long, a medium voltage regulator or a controllable series compensation device is used to increase the voltage at the end of the line; For the tie switch of the ring network line, if the tie switch is in the closed position, disconnect the tie switch; For the three-phase voltage, analyze the three-phase load current and the regularity of the three-phase current changes over time. The three-phase load current should be adjusted by operation and maintenance means to achieve a balanced three-phase load current. For the problem of heavy overload or failure of distribution transformer, new construction or replacement of larger distribution transformer is adopted; If the power supply radius of the substation is too long, the new substation should be built in a "multi-point, small capacity" way to shorten the power supply radius; For load distribution, if a single-phase line carries too much load, the single-phase line is changed to a three-phase four-wire power supply.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method for analyzing the cause of low voltage in a substation as claimed in any one of claims 1 to 5 is implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for analyzing the causes of low voltage in a substation are implemented as claimed in any one of claims 1 to 5.

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