Distribution transformer phase selection and closing method, system, computer equipment and storage medium

Abstract

The present invention provides a distribution transformer phase selection and closing method, system, computer equipment, and storage medium, which belongs to the field of transformer excitation inrush current suppression. The method includes obtaining three-phase voltage and current data before and after the circuit breaker trips of multiple distribution transformers; determining the first two phases to be closed and the last phase to be closed based on the three-phase voltage and current data; calculating the steady-state residual flux per unit value of the multiple distribution transformers by using the initial residual flux at the time of arc extinction based on the predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value; calculating the closing time of the first two phases to be closed based on the steady-state residual flux per unit value, determining the closing time of the last phase to be closed based on the correspondence between the last phase to be closed and the closing time; and performing a closing action by the circuit breaker based on the closing time of the first two phases to be closed and the closing time of the last phase to be closed to obtain the transformer closing result. The method can suppress the excitation inrush current of multiple distribution transformers and enhance the stability of power supply in the distribution network.

Description

Technical Field

[0001] The present invention belongs to the field of transformer excitation inrush current suppression, and in particular relates to a distribution transformer phase selection and closing method, system, computer equipment and storage medium. Background Art

[0002] As the core power equipment of the distribution network, distribution transformers are widely distributed, numerous, and have a large total capacity. They directly supply power to terminal loads. During the restoration of power after fault clearance, the magnetic flux cannot change suddenly due to the hysteresis effect and nonlinear saturation characteristics of the core. When a sudden voltage surge triggers a transient magnetic flux, the core saturates and generates an excitation inrush current with an amplitude of 6-8 times the rated current. The superposition of inrush currents from multiple transformers and load currents can cause the feeder current to seriously exceed the limit, triggering the malfunction of upstream protection devices and causing reclosing failures during transient faults. This poses a significant threat to power supply reliability and may lead to cascading economic losses and social impacts.

[0003] Phase-selective closing technology, with its flexible and controllable features, can rapidly suppress inrush currents for multiple transformers simultaneously. However, existing phase-selective closing technology is primarily applied to the main grid, focusing on suppressing the magnetizing inrush current of a single large transformer with a star-connected primary. However, distribution lines are populated with numerous distribution transformers with delta-connected primary lines, making this technology poorly suited for distribution network scenarios. Therefore, a phase-selective closing method for suppressing magnetizing inrush currents for multiple distribution transformers in a distribution network is urgently needed. Summary of the Invention

[0004] In order to solve the problem that the existing phase selection and closing technology focuses on suppressing the excitation inrush current of a single transformer and has poor applicability in distribution network scenarios, the present invention provides a distribution transformer phase selection and closing method, system, computer equipment and storage medium.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A distribution transformer phase selection closing method is applied to a distribution line equipped with multiple distribution transformers, and the distribution line uses phase-splitting switches. The method includes:

[0007] Obtain three-phase voltage and current data of multiple distribution transformers before and after circuit breaker tripping;

[0008] Based on the three-phase voltage and current data, determine the first two phases to be closed and the last phase to be closed for each distribution transformer. The first two phases to be closed are the two phases of the distribution transformer that have the same closing time and are earlier than the closing time of the third phase, and the arc extinction time is later than that of the third phase. The last phase to be closed is the third phase.

[0009] Based on a predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value, the steady-state residual flux per unit values ​​of the multiple distribution transformers are obtained by calculating the initial residual flux at the arc extinction moment of the multiple distribution transformers, wherein the initial residual flux at the arc extinction moment is determined by calculating the three-phase voltage and current data;

[0010] The closing time of the first two phases to be closed is calculated based on the per-unit values ​​of the steady-state residual flux of multiple distribution transformers, and the closing time of the last phase to be closed is determined based on a preset correspondence between the last phase to be closed and the closing time;

[0011] The circuit breaker is closed based on the closing time of the first two phases to be closed and the closing time of the last phase to be closed.

[0012] Optionally, the distribution transformer phase selection and closing method provided by the present invention further includes:

[0013] When the distribution transformer is in operation, open the circuit breaker and obtain the initial residual flux between the first two closed phases;

[0014] Based on multiple closing angles, the circuit breaker performs closing operation on the first two phases to be closed, and determines the steady-state residual magnetic flux corresponding to the first closing angle, wherein the first closing angle is the closing angle with the smallest excitation inrush current among the multiple closing angles;

[0015] A corresponding relationship between the initial residual flux per unit value and the steady-state residual flux per unit value is generated according to the initial residual flux and the steady-state residual flux.

[0016] Optionally, the three-phase voltage and current data before and after tripping include voltage and current data at the line voltage peak point and voltage and current data at the arc extinction moment. The distribution transformer phase selection and closing method provided by the present invention further includes:

[0017] The initial residual magnetic flux at the time of arc extinction is calculated based on the voltage and current data at the line voltage peak point and the arc extinction time;

[0018] Determine the per-unit value of the initial residual magnetic flux at the arc extinction moment according to the initial residual magnetic flux at the arc extinction moment;

[0019] The steady-state residual flux per unit value at the arc extinction moment is determined by the corresponding relationship between the initial residual flux per unit value and the steady-state residual flux per unit value.

[0020] Optionally, the distribution transformer phase selection and closing method provided by the present invention further includes:

[0021] Determine the circuit breaker disconnection point based on three-phase voltage and current data;

[0022] Determine the arc extinguishing sequence of the three phases according to the disconnection point of the circuit breaker;

[0023] The first two phases to be closed and the last phase to be closed are determined according to the arc extinction sequence of the three phases.

[0024] Optionally, the three-phase voltage and current data further include the positive zero-crossing point of the phase A voltage. The distribution transformer phase selection and closing method provided by the present invention further includes:

[0025] Determine the reference time point according to the positive zero crossing point of the phase A voltage;

[0026] calculating the closing phase angle of the first two phases to be closed based on the per-unit values ​​of the steady-state residual flux and the flux amplitude of the multiple distribution transformers, wherein the flux amplitude is determined based on the primary side voltage amplitude of the three-phase power supply connected to the multiple distribution transformers, the power frequency angular frequency, the number of primary side winding turns, and the number of distribution transformers;

[0027] The closing time of the first two phases is calculated according to the closing phase angle of the first two phases and the reference time point.

[0028] Optionally, the distribution transformer phase selection and closing method provided by the present invention further includes:

[0029] The steady-state residual flux per unit value of the distribution transformers is weightedly calculated according to the weight coefficients corresponding to each of the multiple distribution transformers. The closing phase angle of the first two phases to be closed is determined based on the weighted calculation results and the flux amplitude. The weight coefficient is positively correlated with the capacity of the distribution transformer.

[0030] Optionally, the correspondence between the unclosed phase and the closing time includes a preset correspondence between the three phases and the closing phase angle. The distribution transformer phase selection and closing method provided by the present invention further includes:

[0031] The closing phase angle of the unclosed phase is determined by the preset correspondence between the three phases and the closing phase angle;

[0032] The closing time of the last closed phase is calculated based on the closing phase angle of the last closed phase and the reference time point.

[0033] The present invention also provides a distribution transformer phase selection and closing system, which is applied to a distribution line equipped with multiple distribution transformers and using phase-splitting switches. The system includes:

[0034] The voltage and current acquisition module is used to obtain the three-phase voltage and current data of multiple distribution transformers before and after the circuit breakers trip;

[0035] A three-phase closing sequence determination module is used to determine the first two phases to be closed and the last phase to be closed of each distribution transformer based on the three-phase voltage and current data. The first two phases to be closed are the two phases of the distribution transformer whose closing time is the same and earlier than the closing time of the third phase, and whose arc extinction time is later than that of the third phase. The last phase to be closed is the third phase;

[0036] a steady-state residual flux calculation module, configured to calculate the steady-state residual flux per unit values ​​of the plurality of distribution transformers by calculating the initial residual flux at the time of arc extinction of the plurality of distribution transformers based on a predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value, wherein the initial residual flux at the time of arc extinction is determined by calculating the three-phase voltage and current data;

[0037] A closing time calculation module is used to calculate the closing time of the first two phases to be closed based on the per-unit values ​​of the steady-state residual flux of multiple distribution transformers, and to determine the closing time of the last phase to be closed based on a preset correspondence between the last phase to be closed and the closing time;

[0038] The closing action execution module is used to execute the closing operation on the circuit breaker based on the closing time of the first two phases to be closed and the closing time of the last phase to be closed.

[0039] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement any step of the distribution transformer phase selection and closing method.

[0040] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is loaded by a processor, it can execute any step of the distribution transformer phase selection and closing method.

[0041] The distribution transformer phase selection and closing method provided by the present invention has the following beneficial effects:

[0042] Since the distribution transformer phase selection and closing method provided by the present invention is based on the correspondence between the predetermined initial residual flux per unit value and the steady-state residual flux per unit value, multiple distribution transformers quickly determine the steady-state residual flux of their respective first closed two phases, and determine the closing time of the first closed two phases by means of average calculation. The residual magnetism is considered from an overall perspective, thereby suppressing the excitation inrush current and executing the closing action. This method can adapt to a large number of distribution network scenarios of distribution transformers, expand the application scope of the distribution transformer phase selection and closing, and ensure that the distribution network can smoothly resume power supply after the fault is cleared, thereby enhancing the stability and reliability of the distribution network power supply and avoiding major economic losses and social impacts caused by power outages.

[0043] Moreover, the three-phase voltage and current data obtained by the distribution transformer phase selection and closing method adopted in the present invention simultaneously include the voltage and current data before and after the circuit breaker tripping, thereby determining the first two phases closed and the last phase closed in the distribution transformer, thereby executing the action of closing two phases and then closing one phase. This strategy of closing two phases first and then closing one phase leaves room for coordination with the current distribution network phase reclosing fault identification technology, improves the intelligence level and accuracy of distribution network fault handling, and reduces misjudgment and malfunction. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] To more clearly illustrate the embodiments of the present invention and its design, the following briefly introduces the drawings required for this embodiment. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0045] Figure 1 This is a schematic diagram of a phase selection and closing method for a distribution transformer provided by an embodiment of the present invention;

[0046] Figure 2 A second schematic diagram of the phase selection and closing method for a distribution transformer provided in an embodiment of the present invention;

[0047] Figure 3 Schematic diagram of the third method for phase selection and closing of a distribution transformer provided by an embodiment of the present invention;

[0048] Figure 4 Schematic diagram of the fourth method for phase selection and closing of a distribution transformer provided by an embodiment of the present invention;

[0049] Figure 5 Schematic diagram of the fifth method for phase selection and closing of a distribution transformer provided by an embodiment of the present invention;

[0050] Figure 6 Schematic diagram six of the phase selection and closing method for a distribution transformer provided by an embodiment of the present invention;

[0051] Figure 7 Schematic diagram seven of the phase selection and closing method for a distribution transformer provided in an embodiment of the present invention;

[0052] Figure 8 An example of the control logic of the phase selection and closing technology provided in an embodiment of the present invention;

[0053] Figure 9 An example of the process flow for suppressing the excitation inrush current provided by an embodiment of the present invention;

[0054] Figure 10 An example of a simulation model provided for an embodiment of the present invention;

[0055] Figure 11 Example of excitation current waveform for stable transformer operation and opening of circuit breaker;

[0056] Figure 12 An example of a magnetic flux waveform diagram for a transformer to stabilize operation and open a circuit breaker;

[0057] Figure 13 An example of a voltage waveform for a transformer to stabilize operation and open a circuit breaker;

[0058] Figure 14 This is an example of the excitation current waveform when the three phases of the circuit breaker are closed simultaneously;

[0059] Figure 15 This is an example of the magnetic flux waveform when the three phases of the circuit breaker are closed simultaneously;

[0060] Figure 16 This is an example of the voltage waveform when the three phases of the circuit breaker are closed simultaneously;

[0061] Figure 17 This is an example of the excitation current waveform when the circuit breaker is closed based on the distribution transformer phase selection closing method;

[0062] Figure 18 This is an example of a magnetic flux waveform when the circuit breaker is closed based on the distribution transformer phase selection closing method;

[0063] Figure 19 This is an example of a voltage waveform when the circuit breaker is closed based on the distribution transformer phase selection closing method;

[0064] Figure 20 Schematic diagram of the distribution transformer phase selection and closing system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0065] In order to enable those skilled in the art to better understand the technical solution of the present invention and to be able to implement it, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention.

[0066] Existing methods for suppressing magnetizing inrush current include reconfiguring the primary and secondary winding distribution to increase the equivalent transient inductance, thereby achieving structural optimization, or adding external components such as series resistors, voltage-side capacitors, or specialized suppressors for compensation. However, in distribution network scenarios, structural modification methods involve large-scale equipment upgrades, which are uneconomical and complex to maintain. While additional devices can achieve local suppression, the overall effect is limited. Pre-magnetization methods, which require specialized equipment and are time-consuming, are more suitable for single large transformers and are difficult to meet the needs of multiple transformers. The phase-selective closing method, on the other hand, precisely controls the closing phase of the circuit breaker so that the pre-induced magnetic flux generated by the system voltage and the residual magnetic flux of the iron core cancel each other out, thereby suppressing transient magnetic flux saturation and theoretically completely eliminating magnetizing inrush current. However, research on phase-selective closing to suppress magnetizing inrush current has focused on the main grid, which does not match the actual situation of the distribution network: the connection groups of transformers in the main grid are usually YNy0 or YNd11, while the distribution network is dominated by Dyn11 transformers, resulting in significant differences in the subjects. In addition, research and practice in the main grid often focus on suppressing the magnetizing inrush current of a single transformer, while there are a large number of distribution transformers distributed along the distribution network, and their capacities are not completely consistent. When the feeder circuit breaker performs the power restoration operation, the residual magnetization state of each transformer is different, making the research on phase-selective closing to suppress magnetizing inrush current not applicable.

[0067] The distribution transformer phase selection and closing method provided in this application fully considers the actual situation of the distribution network, including key factors such as the structural characteristics of the transformer core and the connection method of the windings. Taking into account the electromagnetic coupling between the phases of the three-phase transformer, the closing sequence and phase selection will directly affect the suppression effect. It provides a closing strategy for suppressing the excitation inrush current of multiple distribution transformers while taking into account the three-phase coupling characteristics to meet the unique needs of the distribution network. It can significantly reduce the amplitude of the excitation inrush current, effectively improve the stability and reliability of the distribution network during the power restoration process, and provide a strong guarantee for the efficient and safe operation of the distribution network.

[0068] Example 1

[0069] The present application provides a method for phase selection and closing of distribution transformers, which is applied to a distribution line equipped with multiple distribution transformers, and the distribution line adopts a phase-splitting switch, specifically Figure 1 As shown, the method includes the following steps:

[0070] Step 11: Acquire three-phase voltage and current data of multiple distribution transformers before and after circuit breakers trip.

[0071] Step 12: Determine the first two phases to be closed and the last phase to be closed of each distribution transformer based on the three-phase voltage and current data, where the first two phases to be closed are the two phases of the three phases of the distribution transformer whose closing time is the same and earlier than the closing time of the third phase, and whose arc extinction time is later than that of the third phase, and the last phase to be closed is the third phase.

[0072] Step 13: Based on the predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value, the steady-state residual flux per unit values ​​of the multiple distribution transformers are obtained by calculating the initial residual flux at the arc extinction moment of the multiple distribution transformers, wherein the initial residual flux at the arc extinction moment is determined by calculating the three-phase voltage and current data.

[0073] Step 14: Calculate the closing time of the first two phases to be closed based on the per-unit values ​​of the steady-state residual flux of the multiple distribution transformers, and determine the closing time of the last phase to be closed based on a preset correspondence between the last phase to be closed and the closing time.

[0074] Step 15: Based on the closing time of the first two phases to be closed and the closing time of the last phase to be closed, perform a closing operation on the circuit breaker.

[0075] Specifically, in the distribution transformer phase selection and closing method provided in the present application, when multiple transformers are operating in the distribution network, the three-phase voltage and current data such as the three-phase voltage and current waveforms before and after the primary side circuit breaker of the distribution transformer trips are first collected in real time through a data acquisition device.

[0076] Secondly, based on the three-phase voltage and current data collected in real time, determine which phase of the three phases extinguishes the arc first, thereby determining the arc extinction order of the three phases. In the distribution transformer phase selection and closing method provided in this application, the circuit breaker extinguishes the arc in the following manner: one phase current extinguishes the arc first, and the other two phases are equal and reverse. After a period of time, such as several cycles, the other two phases extinguish the arc. After determining the arc extinction order, the two phases that extinguish the arc later are used as the first two phases to be closed, and the phase that extinguishes the arc first is used as the last phase to be closed, thereby determining the closing phase order. Among them, when there are multiple distribution transformers, the first two phases to be closed and the last phase to be closed are unified.

[0077] Since opening and closing a circuit breaker are opposite processes, the opening process directly affects the transformer's per-unit value. Ideally, the residual magnetism (RPM) should not change at the moment the circuit breaker opens, and the residual magnetism at the moment of opening is the steady-state RPM. However, in practice, after the circuit breaker opens, the core magnetic flux begins at a certain point on the steady-state hysteresis loop, undergoes the opening transient, and ultimately drops to a point corresponding to zero current. After a short period of time, the magnetic domains adjust to a new equilibrium state, forming a steady-state RPM. Therefore, there will be some variation between the initial RPM at the moment the circuit breaker opens and the final steady-state RPM. Therefore, the corresponding relationship between the initial RPM and the steady-state RPM is necessary to determine the actual stable RPM of the distribution transformer and then determine the closing parameters for the first two phases to be closed.

[0078] Specifically, for multiple distribution transformers, the initial residual flux at the time of arc extinction is calculated based on the three-phase voltage and current data. Multiple steady-state residual fluxes corresponding to each initial residual flux are then determined based on the predetermined correspondence between the per-unit values ​​of the initial residual flux and the per-unit values ​​of the steady-state residual flux. The steady-state residual fluxes of the multiple distribution transformers are averaged, and the closing phase angle and closing time of the first two phases to be closed are determined based on the average calculation result. The closing phase angle and closing time of the last phase to be closed are then determined based on the phase to which the last phase to be closed specifically corresponds among the three phases.

[0079] After the closing phase sequence is determined and the closing time of the first two phases and the closing time of the last phase are calculated, a closing command is sent to the circuit breaker through the control terminal to complete the closing action.

[0080] It should be emphasized that, considering that distribution transformers currently commonly use Dyn11 three-phase transformers, whose primary neutral point is not grounded, and for three-phase transformers with ungrounded neutral points, when only one phase of the three-phase circuit breaker is closed, the power supply and the transformer windings cannot form a current path. Therefore, for transformers with ungrounded neutral points, at least two phases must be closed simultaneously when the transformer is first closed. In addition, when there are multiple distribution transformers, in order to facilitate unified control, the first two phases closed and the last phase closed can be unified for multiple distribution transformers. For example, multiple distribution transformers can use phases B and C as the first two phases closed and phase A as the last phase closed.

[0081] Since the distribution transformer phase selection and closing method provided by the present invention is based on the correspondence between the predetermined initial residual flux per unit value and the steady-state residual flux per unit value, multiple distribution transformers quickly determine the steady-state residual flux of the first two phases closed, and determine the closing time of the first two phases closed by means of average calculation, considering the residual magnetism from an overall perspective, thereby suppressing the excitation inrush current and executing the closing action, it can adapt to the distribution network scenario with a large number of distribution transformers, expand the application scope of the distribution transformer phase selection and closing, and improve the power supply reliability of the distribution network. It effectively solves the problem that the line cannot be normally powered after maintenance due to the large number of transformers in the distribution network and the excitation inrush current, reduces the misoperation of the upstream line protection of the feeder and the reclosing failure caused by the excitation inrush current, ensures that the distribution network can smoothly resume power supply after the fault is removed, enhances the stability and reliability of the distribution network power supply, and avoids the significant economic losses and social impacts caused by power outages.

[0082] In addition, the three-phase voltage and current data obtained by the distribution transformer phase selection and closing method adopted in the present invention also include the voltage and current data before and after the circuit breaker tripping, thereby determining the first two phases closed and the last phase closed in the distribution transformer, thereby executing the action of closing two phases and then closing one phase. This strategy of closing two phases first and then closing one phase leaves room for coordination with the current distribution network phase reclosing fault identification technology, and can timely cut off the fault when a permanent fault occurs; when a transient fault occurs, this strategy is used to suppress the excitation inrush current, realizing the coordinated work of fault identification and excitation inrush current suppression, improving the intelligence level and accuracy of distribution network fault processing, and reducing misjudgment and malfunction.

[0083] In addition, the distribution transformer phase selection and closing method adopted in the present invention effectively avoids closing overvoltage, reduces the risk of equipment damage and power outages caused by overvoltage, extends the service life of equipment such as transformers, reduces the maintenance cost and power outage losses of the power grid, and improves the overall operating efficiency and power supply quality of the distribution network, which is of great practical significance for ensuring the safe and stable operation of the distribution network.

[0084] On the basis of the above implementation mode, Figure 2 As shown, in the distribution transformer phase selection and closing method provided by the present application, before step 13, the following steps are further included:

[0085] Step 16: When the distribution transformer is in operation, open the circuit breaker and obtain the initial residual flux between the first two closed phases.

[0086] Step 17: Based on the multiple closing angles, perform a closing action on the first two phases to be closed by the circuit breaker to determine the steady-state residual magnetic flux corresponding to the first closing angle, wherein the first closing angle is the closing angle with the smallest excitation inrush current among the multiple closing angles.

[0087] Step 18: Generate a corresponding relationship between the initial residual flux per unit value and the steady-state residual flux per unit value according to the initial residual flux and the steady-state residual flux.

[0088] After a circuit breaker is opened, the residual magnetism changes due to complex transient processes and then stabilizes. The magnetic flux at the moment of opening is called the initial residual flux, and the magnetic flux after stabilization is called the steady-state residual flux. The distribution transformer phase selection and closing method provided in this application also predetermines the phase and amplitude relationship between the initial residual flux per unit value and the steady-state residual flux per unit value before executing the closing operation.

[0089] Specifically, when the transformer is operating normally and stably, the circuit breaker is disconnected. After the circuit breaker is disconnected, the current first extinguishes one phase, such as phase A, and the currents of phases B and C are in opposite phases. The arc is extinguished after 90°. The residual magnetic flux between phases B and C at the time of arc extinguishing is recorded as the initial residual magnetic flux. .

[0090] When the circuit breaker is completely disconnected, the closing action is performed again. At this time, phases B and C are used as the first two phases to be closed, and the first closing angle is recorded. Since phase A is the last closing phase, the closing angle of the last closing phase is not affected by the residual magnetic flux and is fixed to a specific value, such as 90° or 270°, to avoid the influence of the changing closing angle of the last closing phase on the closing transient current. Based on the current closing parameters, the magnetizing inrush current is recorded while closing the circuit breaker, and the first closing angle is continuously adjusted until the magnetizing inrush current is minimized. As the steady-state first closing angle and determine the corresponding steady-state residual flux by formula (1) :

[0091] (1)

[0092] in, is the steady-state residual flux, is the steady-state first closing angle.

[0093] Then, phase B and phase C are respectively used as the unclosed phases, and the corresponding relationship between the initial residual flux per unit value and the steady-state residual flux per unit value corresponding to the two first closing phases is constructed. For example, for the first closing phases A and B, and Corresponding relationship, for the first closing phase is phase B and phase C and Corresponding relationship, for the first closing phase is C, A phase and Correspondence.

[0094] Since the distribution transformer phase selection and closing method provided in this application is based on residual magnetism design, when the residual magnetism is accurately given, the excitation inrush current can be suppressed to a minimum. Determining the correspondence between the initial residual magnetism and the steady-state residual magnetism through experiments in advance not only reduces the difficulty of data calculation during the closing process, but also maximizes the excitation inrush current suppression effect, further ensuring the stability of the distribution network operation.

[0095] On the basis of the above embodiment, the three-phase voltage and current data before and after the tripping include the voltage and current data at the line voltage peak point and the voltage and current data at the arc extinction moment, such as Figure 3 As shown, the distribution transformer phase selection and closing method provided by this application, step 13 includes:

[0096] Step 131 : Calculate the initial residual magnetic flux at the arc extinction moment based on the line voltage peak point and the voltage and current data at the arc extinction moment.

[0097] Step 132: Determine the per-unit value of the initial residual magnetic flux at the arc extinction moment according to the initial residual magnetic flux at the arc extinction moment.

[0098] Step 133: Determine the steady-state residual flux per unit value at the arc extinction moment through the correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value.

[0099] Specifically, the distribution transformer phase selection and closing method provided in the present application determines the steady-state residual magnetic flux in the following manner, thereby determining the closing phase angle and closing time of the first two phases to be closed, and executing the closing action of the first two phases to be closed:

[0100] Considering that the distribution transformers in the distribution network are basically Dyn11 type transformers, the magnetic flux is mainly affected by the line voltage. Therefore, the initial magnetic flux can be obtained by the line voltage integration method. Based on the real-time collected three-phase voltage and current data, the line voltage is integrated from the positive zero crossing point for half a power frequency cycle to obtain the equivalent rated magnetic flux. And integrate from the line voltage peak point to the arc extinction moment to obtain the initial residual flux at the arc extinction moment Among them, the magnetic field needs to pass through the zero point during integration to ensure that the lower limit of the integral is 0. Then, according to the initial residual magnetic flux at the time of arc extinction, Determine the corresponding initial flux per unit value , and based on the predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value, that is, - The corresponding relationship between the steady-state residual magnetic flux and the arc extinction moment is determined, and the steady-state residual magnetic flux is obtained. , for subsequent calculation of the closing phase angle of the two closing phases.

[0101] Since the distribution transformer phase selection and closing method provided in this application accurately calculates the steady-state residual magnetic flux based on real-time voltage data, the distribution transformer phase selection and closing control accuracy is improved, the excitation inrush current is accurately suppressed, and the stability of the power supply is further improved.

[0102] On the basis of the above implementation mode, Figure 4 As shown, the distribution transformer phase selection and closing method provided by this application, step 12 includes:

[0103] Step 121: Determine the circuit breaker disconnection point according to the three-phase voltage and current data.

[0104] Step 122: Determine the arc extinguishing sequence of the three phases according to the circuit breaker disconnection point.

[0105] Step 123: Determine the first two phases to be closed and the last phase to be closed according to the arc extinction sequence of the three phases.

[0106] Specifically, in the distribution transformer phase selection and closing method provided in the present application, the circuit breaker disconnection point is determined based on real-time three-phase voltage and current data, and the arc extinguishing order is determined in combination with which phase extinguishes the arc first and which two phases extinguish the arc later at the circuit breaker disconnection point. The two phases that extinguish the arc later are used as the first two phases to be closed, and the phase that extinguishes the arc first is used as the last phase to be closed, thereby determining the closing order of the three phases.

[0107] Since this application closes the last arc-extinguished phase first, it ensures that the first two phases to be closed are in a stable state, avoids excessive current shock, and thus avoids the generation of huge excitation inrush current, further improving the power supply reliability of the distribution network.

[0108] On the basis of the above implementation, the three-phase voltage and current data also includes the positive zero crossing point of the phase A voltage, such as Figure 5 As shown, the distribution transformer phase selection and closing method provided by this application, step 14 includes:

[0109] Step 141: Determine a reference time point according to the positive zero crossing point of the phase A voltage.

[0110] Step 142: Calculate the closing phase angle of the first two phases to be closed based on the steady-state residual flux per unit value and flux amplitude of the multiple distribution transformers, wherein the flux amplitude is determined based on the primary side voltage amplitude, the power frequency angular frequency, the number of primary side winding turns of the three-phase power supply connected to the multiple distribution transformers, and the number of distribution transformers.

[0111] Step 143: Calculate the closing time of the first two phases according to the closing phase angle of the first two phases and the reference time point.

[0112] Specifically, after the arc extinguishing sequence is determined, the first two phases to be closed and the last phase to be closed are determined, the positive zero crossing point of the phase voltage of phase A is determined based on the real-time three-phase voltage and current data. For example, the time point 2 to 3 cycles before the time when the circuit breaker trips is determined as the reference time point. It should be emphasized that, regardless of whether it is the first closing phase or the last closing phase, the phase reference starting point of all closing phases is the zero crossing point of phase A, and the reference time is the moment corresponding to the positive zero crossing point of phase A voltage.

[0113] When the steady-state residual flux corresponding to the distribution transformer After the determination, the closing phase angle of the first two phases is determined, as shown in formula (2):

[0114] (2)

[0115] in, The closing phase angle of the first two phases to be closed, is the steady-state residual flux.

[0116] Afterwards, the closing time of the first two phases is determined based on the closing phase angle of the first two phases and the reference time point, as shown in formula (3):

[0117] (3)

[0118] in, The closing phase angle of the first two phases to be closed, is the reference time point, is the angular frequency of the three-phase power supply.

[0119] When there are multiple distribution transformers, the steady-state residual flux corresponding to each of the multiple distribution transformers is averaged to obtain the steady-state residual flux mean value, and the closing phase angle and closing time of the first two phases of the multiple distribution transformers are determined based on the calculation result of the steady-state residual flux mean value.

[0120] For a three-phase power supply, as shown in formula (4):

[0121] (4)

[0122] in, is the primary side voltage amplitude, is the power frequency angular frequency, This is the initial phase of the system power supply.

[0123] Taking the first closing of phases B and C as an example, the reference time point is the zero crossing point of phase A voltage with a positive slope. , the inherent closing time of the circuit breaker is .

[0124] The circuit voltage equation when closing phases B and C is shown in formula (5):

[0125] (5)

[0126] in, 、 、 is the magnetic flux corresponding to the primary side (delta side) of the transformer, is the primary side resistance, is the number of turns of the primary winding.

[0127] When the primary side resistance is ignored, formula (4) and formula (5) are combined and simplified using the sum-difference-product formula to obtain formula (6):

[0128] (6)

[0129] Integrating both ends of formula (6) yields formula (7):

[0130] (7)

[0131] The calculation of magnetic flux amplitude is shown in formula (8):

[0132] (8)

[0133] in, is the magnetic flux amplitude, is the primary side voltage amplitude, is the power frequency angular frequency, is the number of turns of the primary winding.

[0134] Then the steady-state flux expression after phases B and C are closed is shown in formula (9):

[0135] (9)

[0136] The steady-state flux expression after phases A and B are closed is shown in formula (10):

[0137] (10)

[0138] The steady-state flux expression after phases A and C are closed is shown in formula (11):

[0139] (11)

[0140] When closing phases B and C, in order to make the magnetic flux enter the steady state directly after closing, the closing moment needs to satisfy formula (12):

[0141] (12)

[0142] When closing phases A and B, in order to make the magnetic flux enter the steady state directly after closing, the closing moment needs to satisfy formula (13):

[0143] (13)

[0144] When closing phases A and C, in order to make the magnetic flux enter the steady state directly after closing, the closing moment needs to satisfy formula (14):

[0145] (14)

[0146] in, 、 、 They are the residual magnetic flux of the primary winding before closing.

[0147] When all three phases are switched on, the circuit voltage equation is as shown in formula (15):

[0148] (15)

[0149] Combining formula (6) with formula (15) and performing sum and difference conversion, we get formula (16):

[0150] (16)

[0151] Ignoring the internal resistance of the primary side and integrating across both ends, the flux expression is as shown in formula (17):

[0152] (17)

[0153] Combined with formula (8), the steady-state magnetic flux between the three phases is expressed as shown in formula (18):

[0154] (18)

[0155] When phase A is the last phase to be closed and phases B and C are the first phases to be closed, the steady-state flux is expressed as shown in formula (19):

[0156] (19)

[0157] When there are n distribution transformers, the steady-state flux when phases B and C are the first two phases to be closed is expressed as shown in formula (20):

[0158] (20)

[0159] By summing formula (20), we get formula (21):

[0160] (twenty one)

[0161] The closing phase angle of the first two phases of each distribution transformer is obtained by calculating the mean value of the steady-state residual flux, as shown in formula (22):

[0162] (twenty two)

[0163] in, is the number of distribution transformers, is the magnetic flux amplitude, is the mean value of the steady-state residual flux, is the closing phase angle of the first two phases of each distribution transformer. Once the closing phase angle of the first two phases of each distribution transformer is determined, the closing time of the first two phases is also determined by formula (3).

[0164] Since the distribution transformer phase selection and closing method provided in this application calculates the average value of the steady-state residual flux not only includes the steady-state residual flux of all distribution transformers, but also combines the primary side voltage amplitude, power frequency angular frequency, primary side winding turns and other data of the three-phase power supply, the residual magnetism is considered from the perspective of the distribution network as a whole to achieve excitation inrush current suppression, thereby further improving the reliability of the distribution network power supply.

[0165] On the basis of the above implementation mode, Figure 6 As shown, in the distribution transformer phase selection and closing method provided by this application, step 142 includes:

[0166] Step 1421: Perform weighted calculation on the per-unit values ​​of the steady-state residual flux of the distribution transformers according to the weight coefficients corresponding to each of the multiple distribution transformers, and determine the closing phase angle of the first two phases to be closed based on the weighted calculation result and the flux amplitude, wherein the weight coefficient is positively correlated with the capacity of the distribution transformer.

[0167] Specifically, the rated currents of multiple distribution transformers with different capacities are shown in formula (23):

[0168] (twenty three)

[0169] in, is the rated capacity, is the rated current, is the rated voltage.

[0170] The magnetizing inrush current is usually 6-8 times the rated current, as shown in formula (24):

[0171] (twenty four)

[0172] in, is the magnetizing inrush current, is the rated current, that is, in the distribution line scenario, such as the 10kV feeder scenario, the peak value of the excitation inrush current is positively correlated with the transformer capacity.

[0173] When the capacity of the distribution transformer is different, the magnetic flux amplitude will also change. Based on formula (8), the first two phases to be closed satisfy formula (25):

[0174] (25)

[0175] Rewriting formula (25) yields formula (26):

[0176] (26)

[0177] Among them, there are n distribution transformers. 、 and is the residual magnetic flux of the primary winding of the first distribution transformer, is the magnetic flux amplitude of each of the n distribution transformers, It is the closing phase angle of the first two phases closed on each distribution transformer.

[0178] In summary, the closing phase angle of the first two phases is related to the ratio of the residual flux to the flux amplitude. Considering the power supply network line, for example, in a 10 kV line, the peak value of the excitation inrush current is positively correlated with the transformer capacity. The excitation inrush current of a large-capacity transformer is larger and needs more attention. In order to describe the problem at the same scale, the distribution transformer phase selection closing method provided in this application also introduces a linear weight coefficient to participate in the weighted calculation, as shown in formula (27):

[0179] (27)

[0180] in, is the weight coefficient corresponding to the i-th distribution transformer, is the capacity of the i-th distribution transformer, and formula (28) is obtained by weighting formula (26):

[0181] (28)

[0182] Adding formula (28) yields formula (29):

[0183] (29)

[0184] in, is the weight coefficient corresponding to the i-th distribution transformer, 、 and is the residual magnetic flux of the primary winding of the first distribution transformer, is the magnetic flux amplitude of each of the n distribution transformers, It is the closing phase angle of the first two phases closed on each distribution transformer.

[0185] The closing phase angle of the first two phases is shown in formula (30), which is related to the per-unit residual flux value of each distribution transformer:

[0186] (30)

[0187] The equivalent steady-state residual flux is defined as shown in formula (31):

[0188] (31)

[0189] At this time, the closing phase angle of the first two phases is shown in formula (32):

[0190] (32)

[0191] After the closing phase angle of the first two phases is calculated based on the linear weight coefficient, the closing time of the first two phases is determined based on the closing phase angle of the first two phases, thereby executing the closing action of the first two phases.

[0192] Since the distribution transformer phase selection and closing method provided in this application comprehensively considers the impact of the capacity differences between different distribution transformers in the distribution network on the excitation inrush current, and emphasizes large-capacity distribution transformers through weighted coefficients, the final determined closing time can better meet the use scenarios of the distribution network, extend the service life of equipment such as transformers, and improve the overall operating efficiency and power supply quality of the distribution network.

[0193] On the basis of the above implementation, the correspondence between the unclosed phase and the closing time includes the preset correspondence between the three phases and the closing phase angle, such as Figure 7 As shown, in the distribution transformer phase selection and closing method provided by the present application, step 14 also includes:

[0194] Step 144: Determine the closing phase angle of the unclosed phase based on the preset correspondence between the three phases and the closing phase angle.

[0195] Step 145 : Calculate the closing time of the unclosed phase based on the closing phase angle of the unclosed phase and the reference time point.

[0196] Specifically, in the distribution transformer phase selection and closing method provided in the present application, the closing phase angle of the first two phases closed needs to be obtained through the steady-state residual magnetic flux, and the closing phase angle of the last phase closed is a fixed value and is independent of the residual magnetic flux.

[0197] For a distribution transformer, based on the difference in the last closed phase, the corresponding closing phase angle is shown in formula (33):

[0198] (33)

[0199] Among them, P is the last closed phase, P=A means the last closed phase is phase A, is the closing phase angle of the last closed phase.

[0200] Afterwards, the closing time of the last closed phase is determined based on the closing phase angle of the last closed phase and the reference time point, as shown in formula (34):

[0201] (34)

[0202] in, is the closing phase angle of the last closed phase, is the reference time point, is the angular frequency of the three-phase power supply.

[0203] When there are multiple distribution transformers, taking phase A as the last closed phase, in order to make the magnetic flux enter the steady state directly after closing, the last closed phase needs to satisfy formula (35) at the same time:

[0204] (35)

[0205] in, is the closing phase angle of the last closed phase, is the residual magnetic flux of the primary winding between phase A and phase B, is the residual magnetic flux of the primary winding group between phase A and phase C, is the magnetic flux amplitude.

[0206] Subtracting formula (35), the difference in residual magnetic flux of the primary winding group is as shown in formula (36):

[0207] (36)

[0208] When there are multiple distribution transformers, the difference in residual magnetic flux of the primary winding groups of multiple distribution transformers is shown in formula (37):

[0209] (37)

[0210] Among them, there are n distribution transformers. and is the residual magnetic flux of the primary winding of the first distribution transformer, and is the residual magnetic flux of the primary winding group of the nth distribution transformer.

[0211] The residual flux difference of the primary winding groups of all distribution transformers is obtained by summing the equations in formula (37), as shown in formula (38):

[0212] (38)

[0213] Based on formula (38), the closing phase of the last closing phase is determined as shown in formula (39):

[0214] (39)

[0215] Considering the actual situation of the distribution network, the residual magnetism of multiple transformers cannot be known, but after a period of delay, the residual magnetism of the remaining two windings tends to be stable, as shown in formula (40):

[0216] (40)

[0217] At this time, the closing phase of the unclosed phase is shown in formula (41):

[0218] (41)

[0219] Therefore, when the last closed phase is phase A, the closing phase angle of the last closed phase is 90°, that is, When the last closed phase is phase B or phase C, the closing phase angle of the last closed phase can also be calculated separately to obtain the closing phase angle of the last closed phase shown in formula (33). The specific calculation method will not be repeated here.

[0220] In addition, considering the different capacities of distribution transformers, the larger the capacity of the distribution transformer, the greater the magnetizing inrush current, which requires more attention. A linear weight coefficient is introduced to calculate the phase and closing phase angle of the closing of the last closing phase. The linear weight coefficient is introduced into formula (39), as shown in formula (42):

[0221] (42)

[0222] Among them, there are n distribution transformers. and is the residual magnetic flux of the primary winding of the first distribution transformer, and is the residual magnetic flux of the primary winding of the nth distribution transformer, are the linear weight coefficients of n distribution transformers respectively, is the magnetic flux amplitude of each of the n distribution transformers.

[0223] The closing phase of the last closing phase is shown in formula (43):

[0224] (43)

[0225] When the two phases are closed and in steady state, , , The closing phase of the last closing phase is shown in formula (41), and the closing phase angles of the three phases corresponding to the last closing phase are shown in formula (33).

[0226] Since the closing phase angle of the last closed phase is not affected by residual magnetism, the distribution transformer phase selection and closing method provided in the present application is targeted at the last closed phase, and the closing phase angles of the three phases corresponding to the last closed phase are predetermined. When executing the closing action, the closing phase angle and closing time of the last closed phase can be quickly determined according to the closing sequence. The relevant parameters are simple and convenient to obtain and easy to put into use, thereby improving the simplicity and practicality of the distribution transformer phase selection and closing.

[0227] Example 2

[0228] This application also provides a distribution transformer phase selection closing method, specifically as follows Figure 8 As shown:

[0229] Among them, 110kV / 10k is the voltage level of the main transformer, corresponding to the main transformer, 10kV / 0.4kV is the voltage level of the distribution transformer, corresponding to the 10kV / 0.4kV distribution transformer targeted by the embodiment of the present application, and the distribution transformer phase selection closing method provided in the embodiment of the present application is used to suppress the excitation inrush current generated by the distribution transformer. First, the three-phase voltage and current waveforms before and after the tripping of the primary-side circuit breaker of the distribution transformer of the distribution network are collected, and then the residual magnetism is calculated. Based on the per-unit value of the steady-state residual magnetic flux, the closing time of the first two phases to be closed and the closing time of the last phase to be closed are determined to determine the closing strategy. Subsequently, the closing strategy is sent to the control terminal, and the control terminal sends an instruction to the circuit breaker (QF) to execute the closing action.

[0230] The distribution transformer phase selection and closing action process is as follows Figure 9 As shown:

[0231] After predetermining the correspondence between the initial magnetic flux and the steady-state magnetic flux, basic data such as the three-phase voltage and current waveforms are collected, and the first phase to extinguish the arc and the last two phases to extinguish the arc are determined based on the circuit breaker disconnection point, thereby determining the arc extinction order, and also determining the reference time point based on the circuit breaker disconnection point.

[0232] Next, the initial magnetic flux is calculated based on basic data such as the three-phase voltage and current waveforms. The per-unit steady-state residual magnetic flux value is determined based on the corresponding relationship between the initial magnetic flux and the steady-state magnetic flux. The closing sequence of the first two phases to be closed and the last phase to be closed is determined based on the arc extinction sequence. The closing time is calculated based on the per-unit steady-state residual magnetic flux value and a reference time point. Finally, the circuit breaker is controlled to close to complete the closing operation.

[0233] The corresponding relationship between the initial magnetic flux and the steady-state magnetic flux can be determined as follows:

[0234] The voltage and current data before and after the circuit breaker is disconnected are collected, and the line voltage data is integrated to obtain the initial residual flux. The final closing angle is controlled to remain unchanged and the closing angles of the first two closing phases are continuously adjusted. The optimal first closing phase angle is determined according to the angle with the minimum excitation inrush current. The steady-state residual flux is calculated based on the first closing phase angle, and a mapping relationship between the initial residual flux and the steady-state residual flux is established, that is, the corresponding relationship between the initial flux and the steady-state flux.

[0235] Example 3

[0236] This application also provides an example of a simulation model in a 10kV distribution network:

[0237] In the electromagnetic transient simulation software PSCAD, the following Figure 10 The simulation model shown in the figure is mainly studied on four three-phase double-winding Dyn11 distribution transformers with a rated voltage of 10kV / 0.4kV and rated capacities of 5MVA, 2MVA, 1MVA, and 0.63MVA, respectively. The active load of each phase is approximately no-load to ensure the normal operation of the model. For example, the load is set to 0.002MW, the system frequency is 50Hz, and the main transformer is 110kV / 10kV.

[0238] First, the transformer enters the stable operation stage, then the circuit breaker is opened, the arc extinction sequence after opening is determined, and the initial residual flux is determined by integration. Then, the steady-state residual flux is determined by the relationship between the initial residual flux and the steady-state residual flux, thereby determining the closing phase angle. Finally, the circuit breaker is closed according to the closing phase angle to suppress the corresponding excitation inrush current. The excitation current, flux, and voltage waveforms when the transformer is operating stably and the circuit breaker is disconnected, the circuit breakers are closed at the same time, and the circuit breaker is closed using this strategy are shown in the figure below. Figure 11-19 As shown. Among them, Figure 11 、 Figure 12 and Figure 13 They are respectively the excitation current waveform of the transformer when it is running stably and the circuit breaker is disconnected, the magnetic flux waveform of the transformer when it is running stably and the circuit breaker is disconnected, and the voltage waveform of the transformer when it is running stably and the circuit breaker is disconnected; Figure 14 、 Figure 15 、 Figure 16 They are respectively the excitation current waveform when the three phases of the circuit breaker are closed simultaneously, the magnetic flux waveform or flux linkage waveform when the three phases of the circuit breaker are closed simultaneously, and the voltage waveform when the three phases of the circuit breaker are closed simultaneously; Figure 17 、 Figure 18 and Figure 19 They are respectively an excitation current waveform diagram when the circuit breaker is closed after the distribution transformer phase selection closing method provided by this embodiment is adopted, a magnetic flux waveform diagram when the circuit breaker is closed, and a voltage waveform diagram when the circuit breaker is closed.

[0239] Specifically, the arc extinguishing order of the distribution transformer phase selection closing method provided in this embodiment is that phase A extinguishes the arc first, followed by phases B and C. Therefore, the closing order is to close phases B and C first, followed by phase A. The initial residual flux is then determined through integration, and the steady-state residual flux is determined based on the relationship between the initial residual flux and the steady-state residual flux. This determines the closing phase angle of phase A to be 270°, while the closing phase angles of phases B and C are 113°. Finally, the circuit breaker is controlled to close.

[0240] Depend on Figure 11 and Figure 14 It can be seen from the two excitation current waveforms that when the three phases of the circuit breaker are closed at the same time, a huge excitation inrush current is generated. Figure 15 The corresponding magnetic flux waveform shows that the magnetic flux has not entered a steady state. Figure 16 The corresponding voltage waveform shows that closing the circuit breaker will also cause closing overvoltage. That is, the method of closing the three phases of the circuit breaker at the same time will cause huge excitation inrush current, which will seriously load the distribution network and affect its stable operation.

[0241] Then, the phase selection closing method of the distribution transformer provided in this embodiment is compared with the method of closing the three phases of the circuit breaker simultaneously. Figure 17 The excitation current waveform can be seen from the figure, compared with Figure 14 The excitation current waveform is shown in Figure 2. After closing, the current quickly enters the steady state, accompanied by only a slight closing transient current, and the excitation inrush current is very small; Figure 18 It can be seen from the magnetic flux waveform that compared with Figure 15 The magnetic flux waveform shows that the magnetic flux has entered a steady state. Figure 19 As can be seen from the voltage waveform, compared with Figure 16 The voltage waveform shows that there is no closing overvoltage.

[0242] In summary, the distribution transformer phase selection closing method provided in this embodiment is used for closing. After closing, the current formed by the superposition of multiple transformers is close to the no-load current, and almost completely enters the steady state. The closing strategy has a significant suppression effect and avoids the generation of closing overvoltage.

[0243] Example 4

[0244] The present application also provides a distribution transformer phase selection and closing system, which is applied to a distribution line equipped with multiple distribution transformers, and the distribution line adopts a phase-splitting switch, such as Figure 20 As shown, the system includes:

[0245] The voltage and current acquisition module 201 is used to obtain three-phase voltage and current data of multiple distribution transformers before and after the circuit breakers are tripped through the phase switches;

[0246] A three-phase closing sequence determination module 202 is configured to determine the first two phases to be closed and the last phase to be closed of each distribution transformer based on the three-phase voltage and current data, wherein the first two phases to be closed are the two phases of the three phases of the distribution transformer that have the same closing time and are earlier than the closing time of the third phase, and have an arc extinction time later than that of the third phase, and the last phase to be closed is the third phase;

[0247] a steady-state residual flux calculation module 203 for calculating the steady-state residual flux per unit values ​​of the plurality of distribution transformers by calculating the initial residual flux at the time of arc extinction of the plurality of distribution transformers based on a predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value, wherein the initial residual flux at the time of arc extinction is determined by calculating the three-phase voltage and current data;

[0248] A closing time calculation module 204 is configured to calculate the closing time of the first two phases to be closed based on the per-unit values ​​of the steady-state residual flux of the plurality of distribution transformers, and determine the closing time of the last phase to be closed based on a preset correspondence between the last phase to be closed and the closing time;

[0249] The closing action execution module 205 is configured to execute a closing operation on the circuit breaker based on the closing time of the first two phases to be closed and the closing time of the last phase to be closed.

[0250] The present invention also provides a computer device comprising a memory, a processor, and a computer program stored in the memory. The processor executes the computer program to implement the steps of the embodiment of the distribution transformer phase selection and closing method. The specific implementation method can be found in the method embodiment and will not be repeated here.

[0251] Furthermore, the present invention provides a non-transitory computer-readable storage medium containing instructions, wherein the storage medium stores a computer program. For example, the storage medium may be a memory containing instructions, wherein the instructions are executable by a processor of a computer device to perform the above-described method. For example, the non-transitory computer-readable storage medium may be a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, or optical data storage device. When executed by the processor, the computer program can implement the steps of the embodiments of the distribution transformer phase selection and closing method. The specific implementation method can be found in the method embodiments and will not be further described here.

[0252] Those skilled in the art will appreciate that embodiments of the present invention may provide methods, systems, or computer program products. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0253] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0254] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0255] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0256] It should be pointed out that the above specific implementation methods can enable those skilled in the art to understand the invention more comprehensively, but do not limit the invention in any way. Therefore, although this specification and examples have described the invention in detail, those skilled in the art should understand that the invention can still be modified or replaced by equivalents; and all technical solutions and improvements that do not deviate from the spirit and scope of the invention are included in the scope of protection of the patent for the invention. Any figure mark in the claims should not be regarded as limiting the claims involved. Any simple change or equivalent replacement of the technical solution that can be obviously obtained by any person familiar with the art within the technical scope disclosed in the present invention belongs to the scope of protection of the present invention.

Claims

1. A phase selection and closing method for a distribution transformer, characterized in that: The method is applied to a distribution line equipped with multiple distribution transformers, and the distribution line uses a phase-splitting switch, and the method includes: Obtain three-phase voltage and current data of multiple distribution transformers before and after circuit breaker tripping; Determine the first two phases to be closed and the last phase to be closed of each distribution transformer based on the three-phase voltage and current data, wherein the first two phases to be closed are two phases of the three phases of the distribution transformer that have the same closing time and are earlier than the closing time of the third phase, and whose arc extinction time is later than that of the third phase, and the last phase to be closed is the third phase; Based on a predetermined correspondence between an initial residual flux per unit value and a steady-state residual flux per unit value, the steady-state residual flux per unit values ​​of the plurality of distribution transformers are obtained by calculating the initial residual fluxes at the arc extinction moment of the plurality of distribution transformers, wherein the initial residual flux at the arc extinction moment is determined by calculating the three-phase voltage and current data; The closing time of the first two phases to be closed is calculated based on the per-unit values ​​of the steady-state residual magnetic fluxes of the plurality of distribution transformers, and the closing time of the last phase to be closed is determined based on a preset correspondence between the last phase to be closed and the closing time; A closing operation is performed on the circuit breaker based on the closing time of the first two phases to be closed and the closing time of the last phase to be closed.

2. The distribution transformer phase selection and closing method according to claim 1, characterized in that: Before obtaining the steady-state residual flux per unit values ​​of the plurality of distribution transformers by calculating the initial residual flux at the arc-extinguishing moment of the plurality of distribution transformers based on the predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value, the method further includes: When the distribution transformer is in operation, opening the circuit breaker and obtaining the initial residual magnetic flux between the first closed two phases; Based on a plurality of closing angles, performing a closing operation on the first two phases to be closed by the circuit breaker, and determining a steady-state residual magnetic flux corresponding to the first closing angle, wherein the first closing angle is a closing angle at which the magnetizing inrush current is minimum among the plurality of closing angles; A correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value is generated according to the initial residual flux and the steady-state residual flux.

3. The distribution transformer phase selection and closing method according to claim 1, characterized in that: The three-phase voltage and current data before and after the tripping include line voltage peak point voltage and current data and voltage and current data at the arc extinction moment. Based on the predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value, the steady-state residual flux per unit values ​​of the plurality of distribution transformers are obtained by calculating the initial residual flux at the arc extinction moment of the plurality of distribution transformers. The steady-state residual flux per unit values ​​include: Calculating the initial residual magnetic flux at the arc extinction moment based on the line voltage peak point and the voltage and current data at the arc extinction moment; Determining the initial residual flux per unit value at the arc extinction moment according to the initial residual flux at the arc extinction moment; The steady-state residual flux per unit value at the arc extinction moment is determined according to the corresponding relationship between the initial residual flux per unit value and the steady-state residual flux per unit value.

4. The distribution transformer phase selection and closing method according to claim 1, characterized in that: Determining the first two phases to be closed and the last phase to be closed according to the three-phase voltage and current data includes: determining a circuit breaker disconnection point according to the three-phase voltage and current data; Determining the arc extinguishing sequence of the three phases according to the disconnection point of the circuit breaker; The first two phases to be closed and the last phase to be closed are determined according to the arc extinction sequence of the three phases.

5. The distribution transformer phase selection and closing method according to claim 1, characterized in that: The three-phase voltage and current data also includes the positive zero-crossing point of the phase A voltage. The closing time of the first two phases to be closed is calculated based on the per-unit values ​​of the steady-state residual magnetic flux of the plurality of distribution transformers and includes: Determine a reference time point according to the positive zero crossing point of the phase A voltage; The closing phase angle of the first two phases to be closed is calculated based on the per-unit values ​​of the steady-state residual magnetic flux and the magnetic flux amplitude of the plurality of distribution transformers, wherein the magnetic flux amplitude is determined based on the primary side voltage amplitude, the power frequency angular frequency, the number of primary side winding turns of the three-phase power supply connected to the plurality of distribution transformers, and the number of the distribution transformers; The closing time of the first two phases is calculated according to the closing phase angle of the first two phases and the reference time point.

6. The distribution transformer phase selection and closing method according to claim 5, characterized in that: The closing phase angle of the first two phases to be closed is calculated based on the steady-state residual flux per unit value and flux amplitude of the plurality of distribution transformers, including: A weighted calculation is performed on the per-unit value of the steady-state residual flux of the distribution transformer according to the weight coefficient corresponding to each of the multiple distribution transformers, and the closing phase angle of the first two phases to be closed is determined based on the weighted calculation result and the flux amplitude, wherein the weight coefficient is positively correlated with the capacity of the distribution transformer.

7. The distribution transformer phase selection and closing method according to claim 5, characterized in that: The correspondence between the last closed phase and the closing time includes a preset correspondence between the three phases and the closing phase angle. Determining the closing time of the last closed phase based on the preset correspondence between the last closed phase and the closing time includes: Determining the closing phase angle of the unclosed phase based on the correspondence between the three phases and the closing phase angle; The closing time of the unclosed phase is calculated based on the closing phase angle of the unclosed phase and the reference time point.

8. The distribution transformer phase selection and closing system is characterized by: The system is applied to a distribution line equipped with multiple distribution transformers and using phase-splitting switches. The system includes: The voltage and current acquisition module is used to obtain the three-phase voltage and current data of multiple distribution transformers before and after the circuit breakers trip; a three-phase closing sequence determination module, configured to determine the first two phases to be closed and the last phase to be closed of each distribution transformer based on the three-phase voltage and current data, wherein the first two phases to be closed are two phases of the three phases of the distribution transformer whose closing times are the same and earlier than the closing time of the third phase, and whose arc extinction times are later than that of the third phase, and the last phase to be closed is the third phase; a steady-state residual flux calculation module, configured to obtain the steady-state residual flux per unit values ​​of the plurality of distribution transformers by calculating the initial residual flux at the arc extinction moment of the plurality of distribution transformers based on a predetermined correspondence between the initial residual flux per unit value and the steady-state residual flux per unit value, wherein the initial residual flux at the arc extinction moment is determined by calculating the three-phase voltage and current data; a closing time calculation module, configured to calculate the closing time of the first two phases to be closed based on the per-unit values ​​of the steady-state residual magnetic fluxes of the plurality of distribution transformers, and determine the closing time of the last phase to be closed based on a preset correspondence between the last phase to be closed and the closing time; The closing action execution module is used to perform a closing operation on the circuit breaker based on the closing time of the first two phases to be closed and the closing time of the last phase to be closed.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory, wherein: The processor executes the computer program to implement the steps of the distribution transformer phase selection and closing method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is loaded into a processor, it can execute the steps of the distribution transformer phase selection and closing method according to any one of claims 1 to 7.

Images