A system and method for non-stop loop closing and reverse power supply with a 30-degree angle difference tie line

Abstract

The application discloses a system and method for loop closing and power supply reversal without power interruption of a 30-degree angle difference tie line, comprising a loop topology automatic generation module, an operation parameter automatic acquisition module, a loop closing current automatic calculation module, a loop protection setting value checking module and a loop closing setting value automatic generation module. The system is equipped to make the loop closing operation more intelligent, the loop closing current calculation more accurate and scientific, and the loop closing protection setting value setting more suitable for engineering application. The function cooperation and method application based on the system realize the loop closing of the 30-degree angle difference tie line without power interruption, effectively improve the power supply reliability of users, and reduce the on-site operation workload of operation and maintenance personnel. Since the scheme is put into operation in the early stage, more than 100 10kV lines and more than 500,000 users are avoided from power interruption, the users are not aware of the power interruption, the power interruption order pressure is effectively reduced, and the power supply service level is greatly improved.

Description

Technical Field

[0001] This invention relates to a system for uninterrupted power supply switching with a 30-degree angle difference tie line, and more particularly to a system and method for uninterrupted power supply switching with a 30-degree angle difference tie line. Background Technology

[0002] Currently, most three-winding transformers in step-down substations are Y / Y / Δ connected, while two-winding transformers are mostly Y / Δ connected. When both sides of different voltage levels are Y / Y connected, there is no phase difference. When both sides are Y / Δ connected, there is a 30-degree phase difference. During the transition from a high voltage level to a low voltage level, the phase difference between the two sides increases by 30 degrees each time the transformer with the Y / Δ connection is used. Therefore, when the number of Y / Δ transitions experienced by the power supplies on both sides of the 35kV, 10kV, and 6kV tie lines during the step-down process to the 220kV voltage level is inconsistent, a 30-degree phase difference will exist between the two sides.

[0003] Taking a 35kV tie line as an example (each voltage level in the example represents a transformer of the corresponding voltage level), the voltage step-down from 220kV to 35kV in the power system is divided into two methods: 220kV-110kV-35kV and 220kV-35kV. When power source 1 supplies power in the 220kV-110kV-35kV mode, no Y / Δ conversion is performed. When power source 2 supplies power in the 220kV-35kV mode, a Y / Δ conversion is performed once. At this time, there is a 30-degree phase angle difference between power source 1 and power source 2 on both sides of the tie line.

[0004] Taking a 10kV (6kV) tie line as an example (each voltage level in the example represents the transformer of the corresponding voltage level), the voltage step-down from 220kV to 10kV (6kV) in the power system is divided into four methods: 220kV-110kV-35kV-10kV (6kV), 220kV-110kV-10kV (6kV), 220kV-10kV (6kV), and 220kV-35kV-10kV (6kV). When power supply 1 is supplied in the following ways: 220kV-10kV (6kV), 220kV-110kV-10kV (6kV), and 220kV-110kV-35kV-10kV (6kV), it undergoes one Y / Δ conversion. When power supply 2 is supplied in the following way: 220kV-35kV-10kV (6kV), it undergoes two Y / Δ conversions. At this time, there is a 30-degree phase angle difference between power supply 1 and power supply 2 on both sides of the tie line.

[0005] If a power grid with a 30-degree angle difference is closed in a loop, the large circulating current caused by the voltage difference will result in significant voltage angle fluctuations, making it difficult to meet the grid stability requirements and equipment current carrying capacity requirements. Therefore, loop closing operations are generally prohibited. According to dispatching regulations, tie lines with a 30-degree angle difference are not allowed to be directly closed in a loop; a "break-then-close" power outage method (cold-switch loop closing) must be used for load transfer. This involves a short-term equipment shutdown, inevitably causing short-term power outages for users, compromising power supply reliability. To reduce the impact of power outages on users, power companies currently generally schedule mode adjustment work at night or in the early morning. This not only increases the workload for maintenance and repair personnel but also introduces more safety risks during nighttime operations. Furthermore, if critical equipment malfunctions during the cold-switch operation, such as a pole-mounted circuit breaker failing to close properly, it will prolong the power outage time for users, severely affecting power supply reliability and posing significant safety hazards.

[0006] Existing technology, such as the method for automatic loop closing in a distribution network with a 30-degree phase difference disclosed in patent application publication number CN116316862A, includes constructing a typical distribution line with a 30-degree phase difference in the distribution network, obtaining real-time operating parameters of the typical distribution line; calculating the switch protection settings of the typical distribution line based on the real-time operating parameters; calculating the loop closing current based on the real-time operating parameters, constructing safe loop closing conditions, and executing the loop closing operation. This method can achieve automatic loop closing between distribution lines with a 30-degree phase difference in the distribution network, reducing the impact of power outages and power adjustments on users. Specifically, the appendices disclosed in this patent... Figure 1 and attached Figure 2 The common process is as follows: Calculate the protection settings for relevant main transformer protection, substation line protection, and line tie switch protection based on the operating parameters of the distribution network. All of the above are standard value settings and have no actual relation to the 30-degree angle difference loop closure. (The attached text is incomplete and cannot be translated accurately.) Figure 3 The patent specification calculates the current after loop closure based on real-time operating parameters, but in reality, it does not calculate the loop closure current; it simply uses 1.5 times the allowable line current as the protection setting value. Overall, the method disclosed in this patent is rather crude and has the following problems: 1. When the loop closure path is long and the loop closure current is small, the relevant loop closure protection will not be able to effectively and quickly disconnect the loop closure current. If the dispatcher does not manually disconnect the loop in time, problems such as overload and overheating of equipment within the loop may occur; 2. The method's loop disconnection protection setting value is too large, and in extreme cases, it may result in an unreasonable configuration of the protection level difference with the incoming line switch protection within the station.

[0007] Existing technology, such as the method and system for uninterrupted load adjustment of a 10kV line with a 30-degree angle difference, disclosed in application publication number CN115313368A, includes: S1, establishing a protection setting adjustment diagram based on the loop protection setting; S2, calculating the loop closing current value; S3, setting the protection setting of the de-loop switch lower than the loop closing current value; S4, setting the loop protection setting higher than the loop closing current value. This patent only considers the loop current caused by the voltage difference between the two sides of the closed loop line. In reality, the current flowing through the closed loop path during loop closing is not only due to the voltage difference but also affected by the power flow on both sides and the combined impedance on both sides of the loop. Furthermore, this patent fixes the angle difference between the two sides at 30 degrees during calculation, while the actual angle difference between the two sides of the closed loop line will vary with the load conditions. Therefore, the method mentioned in this patent does not fully conform to the actual situation. Additionally, the aforementioned patent does not consider the power flow redistribution that occurs during actual operation when the loop is closed, which may lead to a significant deviation between the closed loop current and the actual operating conditions.

[0008] Besides the inaccuracy in calculating the closed-loop current, the two existing technologies mentioned above also have significant shortcomings in terms of intelligence, such as automatic generation of closed-loop topology, automatic acquisition of operating parameters, automatic calculation of closed-loop current, verification of protection settings within the loop, and automatic generation of closed-loop settings. Summary of the Invention

[0009] To address the shortcomings of the aforementioned technologies, this invention provides a system and method for uninterrupted power supply and loop-connection switching with a 30-degree angle difference interconnection line.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is: a system for uninterrupted power-on loop switching with a 30-degree angle difference tie line, comprising:

[0011] Automatic loop topology generation module, automatic operating parameter acquisition module, automatic loop current calculation module, loop protection setting verification module, and automatic loop setting generation module;

[0012] The automatic loop topology generation module and the automatic operating parameter acquisition module work together to automatically generate the loop power grid topology and extract the operating parameters.

[0013] The automatic loop current calculation module is used to calculate the loop current.

[0014] The loop protection setting verification module is used to verify the protection settings by comparing them with the maximum load current and the protection limits of the loop within the statistical period.

[0015] The automatic loop closing setting generation module is used to generate loop closing protection settings.

[0016] Furthermore, it includes the following steps:

[0017] S1. The power grid dispatcher selects the loop-closing object, automatically generates the loop-closing path power grid topology through the system's loop topology automatic generation module, and extracts the loop-closing path operating parameters through the system's operating parameter automatic acquisition module.

[0018] S2. The system uses the automatic loop current calculation module to calculate the loop current according to the power flow calculation method of the dual-end power supply network based on the loop path parameters and its operating parameters.

[0019] S3. Generate unloop protection settings.

[0020] Furthermore, in S1, the power grid dispatcher enters the expected loop-closing switch information, the first loop-breaking switch information, and the second loop-breaking switch information in the system loop-closing operation interface. The second loop-breaking switch information is optional. The expected loop-closing switch information, the first loop-breaking switch information, and the second loop-breaking switch information each include the substation name and the dual number of the line switch.

[0021] Furthermore, it is expected that after the information of the loop-closing switch, the first loop-breaking switch, and the second loop-breaking switch is entered, the system will trace back the loop-closing topology from the loop-closing switch node based on the principle of gradually increasing the voltage level, using external full power grid topology model data.

[0022] Furthermore, the principle of gradually increasing voltage levels includes:

[0023] A1. Traverse upwards from the nodes of the entered loop switch to the station bus (direction 1) and the line (direction 2) respectively;

[0024] A2. When tracing back to the busbar equipment

[0025] like,

[0026] When the voltage level on other sides of the transformer connected to the busbar is higher than the busbar voltage level, the closed-loop path continues upstream through the main transformer.

[0027] like,

[0028] When the voltage level on other sides of the transformer connected to the busbar is lower than the voltage level of the busbar, the loop path continues to trace upstream along the busbar outgoing line interval.

[0029] A3. When tracing back to the busbar equipment

[0030] When it is determined that the path is to trace back along the bus and there are multiple outgoing line bays on the bus, the tracing shall be carried out according to each line bay. The tracing shall continue only when the switch and disconnector at the tracing point are in the closed position. When the switch or disconnector at the opposite end is in the open position, the path is not a closed loop path and the direction shall be terminated.

[0031] A4. When continuing to trace upstream through the main transformer according to the loop closing path in A2.

[0032] like,

[0033] If the other direction does not lead back to the main transformer, then the tracing should continue from the highest voltage level side of the main transformer.

[0034] like,

[0035] If the other direction simultaneously traces back to the main transformer, then the closed-loop path power grid topology is formed;

[0036] A5. When direction 1 and direction 2 trace back to the same busbar device, a closed-loop path network topology is formed.

[0037] Furthermore, the extraction of loop-closing path operating parameters in S1 involves extracting operating data parameters related to loop closure from the real-time operating data of the entire power grid, including:

[0038] Impedance of the main transformer and transmission lines;

[0039] In actual power flow operation, the voltage amplitude, current amplitude, active power value, and reactive power value of each node;

[0040] Each protection setting within the loop is reset to its initial value;

[0041] Historical load current time-sharing data for each main transformer and line.

[0042] Furthermore, in S2, when the distribution network closes at a 30-degree angle difference, the power redistribution of the two-terminal power supply networks with unequal voltage magnitudes and different phases can be considered as follows:

[0043] That is, Formula 1;

[0044] because but

[0045] Formula 1 rewritten as That is, Formula 2;

[0046] That is, Formula 3;

[0047] In the formula, Z represents the difference in voltage across the two ends. 12 Z 23 Z 34 Both are impedances; U N S a S2 and S3 are both power.

[0048] Furthermore, in a two-terminal power supply network with unequal voltages at both ends, the power flowing through each end is the superposition of two power components; the system performs per-unit value conversion on the extracted data information, and calculates the power flow and current value of each node when the loop is closed according to Formula 3.

[0049] Furthermore, the result of the loop closing current calculated in S2 is transmitted to the loop closing setting automatic generation module through the system, and the loop breaking protection setting generation coefficient is selected;

[0050] Loop-closing protection setting = Loop-closing current / Loop-closing protection setting generation coefficient.

[0051] A system and method for uninterrupted loop-closing power supply with a 30-degree angle difference tie line is presented. By incorporating modules for automatic loop topology generation, automatic operating parameter acquisition, automatic loop current calculation, loop protection setting verification, and automatic loop setting generation, the system achieves more intelligent loop-closing operations and more accurate and scientific loop current calculations, fully conforming to actual power grid operation conditions. The loop-breaking protection setting is also more suitable for engineering applications. The system's functional coordination and methodological application enable uninterrupted loop-closing of the 30-degree angle difference tie line, effectively improving power supply reliability for users and reducing the workload of maintenance personnel on-site. Since its initial implementation and operation, this solution has prevented power outages for over 100 10kV lines and over 500,000 users, achieving seamless user experience, effectively reducing power outage work order voltage, and significantly improving power supply service levels. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the process of the present invention.

[0053] Figure 2 This is the equivalent circuit diagram of a simple two-terminal ring network.

[0054] Figure 3 This is a diagram of the 35kV Dongkou South power supply method.

[0055] Figure 4 This is the equivalent circuit for the power supply network at both ends of the 35kV Dongkou South Station.

[0056] Figure 5 Waveforms were recorded for the 364-loop connection process of the Qipan Station Qinan Line 220kV.

[0057] Figure 6 This is an example diagram of Example 4. Detailed Implementation

[0058] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0059] Example 1

[0060] This embodiment relates to a system with a 30-degree angle difference tie line that allows for uninterrupted power supply in a closed loop, including: a loop topology automatic generation module, an operating parameter automatic acquisition module, a closed loop current automatic calculation module, an in-loop protection setting verification module, and a closed loop setting automatic generation module.

[0061] The automatic loop topology generation module and the automatic operating parameter acquisition module work together to automatically generate the loop power grid topology and extract operating parameters; the automatic loop current calculation module is used to calculate the loop current; the loop protection setting verification module is used to verify the loop protection setting by comparing it with the maximum load current and the protection limit of each loop within the statistical period; and the automatic loop setting generation module is used to generate the loop disconnection protection setting.

[0062] Example 2

[0063] Based on Example 1, this example discloses a method for a system with a 30-degree angle difference tie line that allows for uninterrupted power supply and loop reversal, including the following steps:

[0064] S1. The power grid dispatcher selects the loop-closing object, automatically generates the loop-closing path power grid topology through the system's loop topology automatic generation module, and extracts the loop-closing path operating parameters through the system's operating parameter automatic acquisition module.

[0065] S2. The system uses the automatic loop current calculation module to calculate the loop current according to the power flow calculation method of the dual-end power supply network based on the loop path parameters and its operating parameters.

[0066] S3. Generate unloop protection settings.

[0067] In S1 of this embodiment, the power grid dispatcher enters the expected loop closing switch information, the first loop breaking switch information, and the second loop breaking switch information in the system loop closing operation interface. The second loop breaking switch information is optional. The expected loop closing switch information, the first loop breaking switch information, and the second loop breaking switch information each include the substation name and the line switch dual number. It should be noted that the system loop closing operation interface is existing technology.

[0068] Furthermore, it is expected that after the information of the loop-closing switch, the first loop-breaking switch, and the second loop-breaking switch is entered, the system will trace back the loop-closing topology from the loop-closing switch node based on the principle of gradually increasing the voltage level, using external full power grid topology model data.

[0069] The principle of gradually increasing voltage levels includes:

[0070] A1. Traverse upwards from the nodes of the entered loop switch to the station bus (direction 1) and the line (direction 2) respectively;

[0071] A2. When tracing back to the busbar equipment

[0072] If the voltage level on other sides of the transformer connected to the busbar is higher than the busbar voltage level, the loop path continues upstream through the main transformer.

[0073] If the voltage level on other sides of the transformer connected to the bus is lower than the voltage level of the bus, the loop path continues to trace upstream along the bus outgoing line interval.

[0074] A3. When tracing back to the busbar equipment

[0075] When it is determined that the path is to trace back along the bus and there are multiple outgoing line bays on the bus, the tracing shall be carried out according to each line bay. The tracing shall continue when the switch and disconnector at the tracing point are in the closed position. When the switch or disconnector at the opposite end is in the open position, the path is not a closed loop path and the direction shall be terminated. It should be noted that when the bus tie switch is in the closed position, the two bus sections are regarded as the same bus.

[0076] A4. When continuing to trace upstream through the main transformer according to the loop closing path in A2.

[0077] If the other direction does not lead back to the main transformer, then the tracing should continue from the highest voltage level side of the main transformer.

[0078] If the other direction simultaneously traces back to the main transformer, a closed-loop power grid topology is formed;

[0079] A5. When direction 1 and direction 2 trace back to the same busbar device, a closed-loop path network topology is formed.

[0080] In this embodiment, the extraction of loop-closing path operating parameters in S1 involves extracting operating data parameters related to loop closure from the real-time operating data of the entire power grid, including:

[0081] Impedance of main transformers and lines; voltage amplitude, current amplitude, active power value, and reactive power value of each node in actual power flow; primary set value of each protection in the loop; time-sharing data of historical load current of each main transformer and line.

[0082] In S2 of this embodiment, when the distribution network closes at a 30-degree angle difference, the power redistribution of the two power supply networks with unequal voltage magnitudes and different phases can be considered as follows:

[0083] That is, Formula 1;

[0084] because but

[0085] Formula 1 rewritten as That is, Formula 2;

[0086] It should be noted that the power flowing through impedance Z12 can be solved from Equation 2, and then solved from Equation 3;

[0087] That is, Formula 3;

[0088] In the formula, Z represents the difference in voltage across the two ends. 12 Z 23 Z 34 Both are impedances; U NS a S2 and S3 are both power.

[0089] Based on the above formula, it can be seen that in a two-terminal power supply network with unequal voltages at both ends, the power flowing through each end can be considered as the superposition of two power components. The first component is the power when the voltages at both ends are equal, which depends on the power flow and impedance distribution of the two-terminal power supply network, i.e., the first part of Formula 3. This part of the power ultimately flows to the load side and does not circulate within the closed loop path; the change is the power transferred by the closed loop power flow. The second component depends on the difference in voltages at both ends. The power of the total impedance of the ring network is the second part of Formula 3, which will circulate within the closed loop path.

[0090] It should be noted that Z 12 Z 23 Z 34 The impedance parameters have been automatically obtained directly in step S1; including U N The data including S1, S2, and S3 are power grid operation data, which can be obtained in step S1 through real-time or cross-sectional historical data. The amplitude can be obtained from the power flow and voltage amplitude at each node.

[0091] Furthermore, The amplitude is obtained as follows:

[0092] The highest voltage level equipment in both directions 1 and 2 is used as the reference. When the equipment is the main transformer equipment, the high voltage side of the main transformer is used as the reference.

[0093] Then pass,

[0094] That is, Formula 4.

[0095] The voltage at each device node is iteratively calculated in both directions 1 and 2 until the loop-closing switch is reached, and then the phase difference of the loop-closing voltage is obtained.

[0096] Finally, the system automatically converts the extracted data into per-unit values ​​and calculates the power flow and current values ​​of each node when the loop is closed according to Formula 3.

[0097] Regarding S3, the closing current has already been calculated in S2. The set value range standard is: load current at the closing time < set value < closing current, i.e., overcurrent protection. The protection device does not operate under normal load current, and operates under closing current. The closing current calculated in S2 is transmitted to the closing setting automatic generation module through the system, and the loop-breaking protection setting generation coefficient is selected. Loop-breaking protection setting = closing current / loop-breaking protection setting generation coefficient.

[0098] It should be noted that, in order to ensure that the protection device does not operate under normal load current, the loop closing operation is usually selected during the off-peak load period at night. The selected loop closing time is when the load current is less than the loop closing current / the loop breaking protection setting generation coefficient / the load coefficient. After the loop breaking protection setting is generated, the loop breaking protection action time is selected. In actual operation, in order to avoid the switch not tripping and unable to break the loop due to reasons such as the trip output pressure plate not being engaged or the switch mechanism being jammed, a backup loop breaking protection setting and a backup loop breaking protection action time can also be set.

[0099] Example 3

[0100] Based on Example 2, this example provides case evidence to demonstrate the effectiveness of step S2 in Example 2.

[0101] Taking the 35kV Dongkou South substation as an example, the closed-loop power and current calculations are carried out. The 35kV Dongkou South power supply method is as follows: Figure 3 As shown.

[0102] Before the loop closure, at the 35kV Dongkou South Substation, switch 311 on the Qinan Line was closed, and switch 312 on the Lingdong Line was open; at the 35kV Lingshan Substation, switch 322 was closed, and the 35kV Lingdong Line was charging and on standby. At the 220kV Qipan Substation, 110kV was operating in parallel, and 35kV was operating separately; switch 364 on the 35kV Qinan Line was connected to the 35kV Dongkou South Substation. At the 110kV Lingshan Substation, 110kV, 35kV, and 10kV were all operating in parallel; switch 345 on the Lingling Line was connected to the 35kV Lingshan Substation.

[0103] The 35kV Lingshan substation bus voltage does not undergo a 30-degree turn after passing through the transformers at Qipan and Lingshan substations, while the 35kV Dongkou South substation bus voltage undergoes a 30-degree turn after passing through the transformer at Qipan substation. The voltage phase angle difference between the two sides of the 312 switch on the Lingdong line at Dongkou South substation is approximately 30 degrees. Furthermore, on the same day, the 35kV Xiahe photovoltaic power station line was under maintenance, requiring the load of the 35kV Dongkou South substation to be transferred to the 35kV Lingshan side for power supply. The per-unit impedance values ​​of each line and main transformer within the loop are shown in Table 1.

[0104] 1 Z1: 35kV Qinan Line 1.4214+j3.2859 2 Z2: 35kV Lingdong Line 1.381+j2.5121 3 Z3: 35kV Lingling Line 0.3636+j0.4875 4 Z4: 110kV Lingshan Substation No. 1 Main Transformer High Voltage j2.5755 5 Z4: 110kV Lingshan Substation No. 1 Main Transformer in operation -j0.165 6 Z4: 110kV Lingshan Substation No. 2 Main Transformer High Voltage j2.2 7 Z4: 110kV Lingshan Substation No. 2 main transformer in operation -j0.146 8 Z5: 110kV Qiling II Line Pingyang Branch Line 0.1868+j0.5747 9 Z6: 220kV Qipan Station No. 2 main transformer in operation -j0.0606 10 Z6: 220kV Qipan Station No. 2 Main Transformer Low Voltage j0.5314

[0105] Table 1 shows the per-unit impedance values ​​of each line and main transformer within the loop.

[0106] Regarding the power transfer of the closed loop.

[0107] Organize the per-unit impedance values ​​of each line and main transformer within the closed loop path, and the power of each node at typical times, and plot as follows: Figure 4 The equivalent circuit of the two-terminal power supply network is shown.

[0108] Based on this, the relevant impedance values ​​and power of each node in the formula calculation are summarized as shown in Table 2, where the total impedance conjugate value is 3.3528-j8.44.

[0109]

[0110]

[0111] Table 2 shows the relevant parameters for power flow calculation of the power supply network at both ends of the 35kV Dongkou South Station.

[0112] The power transfer power flowing through the medium-voltage side impedance of Qipan Station is calculated using Formula 3 disclosed in Example 2 as 20.997 + j0.711; the load transfer from 35kV Lingshan Station to 35kV Dongkou South Station is -3.603 + j0.711; and the current converted to the 35kV voltage level is approximately 60.59A.

[0113] Regarding the closed-loop cycle power.

[0114] Because there is a 30-degree angle difference between the 35kV Lingshan Station and the 35kV Dongkou South Station, and the Dongkou South Station is ahead of the Lingshan Station; assuming that the voltage angle of Lingshan Station is 0, and ignoring the voltage drop from the 220kV Qipan Station to Lingshan Station and the Dongkou South Station, the per-unit value of the 35kV voltage south of the Dongkou Station is 1ej30, which is expressed as 0.866+j0.5 in complex form; the voltage difference between Lingshan Station and Dongkou South Station is 0.134-j0.5.

[0115] Based on this, using the impedance data shown in Table 2, the circulating power flowing from Lingshan Station to Dongkou South due to the voltage difference is calculated to be -56.614 + j6.613 using Formula 3 disclosed in Example 2. The current converted to the 35kV voltage level is approximately 877.59A.

[0116] Regarding the total power and current of the closed loop.

[0117] The relevant data on closed-loop power transfer and cycle power are compiled and shown in Table 3 below:

[0118]

[0119] Table 3 shows the closed-loop power and current of switch 312 on the 35kV Southeast Lingdong Line.

[0120] The specific waveform recording of the 364-loop connection process of the 220kV Qipan Station Qinan Line is as follows: Figure 5 As shown, the power of the 364-phase interval changes from 1.101+j2.345 to 58.338+j3.201, and the loop current of phase A changes from 43.158A to 926.276A. This result is consistent with the calculated result.

[0121] Example 4

[0122] This embodiment further illustrates step S3 based on embodiment 2.

[0123] like Figure 6 As shown, a 35kV substation normally receives all its load from a 110kV substation via switches 361 and 312. Switches 361 and 312 are in the closed position. Now, it is necessary to connect the 35kV substation to a 220kV substation by closing the loop, which requires closing switch 311 and opening switch 312.

[0124] After the power grid dispatcher remotely closes switch 311, the loop-breaking process begins. If the loop-breaking current is calculated to be 800A in the second step, the loop-breaking protection setting generation coefficient for switch 312 is selected as 1.5, and the load factor is selected as 1.2. Then, the loop-breaking protection setting range is 800 / 1.5 / 1.2 = 444A < loop-breaking protection setting < 800 / 1.5 = 533A. To ensure the protection trips switch 312 sensitively, a low value is selected within the above range. Thus, the loop-breaking operation is performed when the load current is less than the low value / 1.2. The loop-breaking protection action time is selected as 0-0.1 seconds.

[0125] To prevent the 312 switch from failing to trip and thus unable to clear the loop due to reasons such as the trip output pressure plate not being engaged or the switch mechanism being jammed, the backup loop clearing protection setting value for the 361 switch (the same as that for the 312 switch) and the backup loop clearing protection action time are set, such as selecting 0.3 seconds to trip the 361 switch.

[0126] Through the above steps, the 35kV substation can be switched to a 220kV substation for power supply without interruption.

[0127] This application discloses a system and method for uninterrupted loop-connection and reverse power supply for tie lines with a 30-degree angle difference. By setting up modules for automatic loop topology generation, automatic operation parameter acquisition, automatic loop current calculation, loop protection setting verification, and automatic loop setting generation, the system makes loop-connection operation more intelligent, and loop current calculation more accurate and scientific, fully conforming to the actual operation of the power grid. The loop-breaking protection setting is more suitable for engineering applications. The functional coordination and methodological application based on the system enable uninterrupted loop-connection for tie lines with a 30-degree angle difference, effectively improving the reliability of power supply to users and reducing the workload of maintenance personnel on-site. Since its initial implementation and operation, this solution has prevented power outages for over 100 10kV lines and over 500,000 users, achieving seamless user experience, effectively reducing the voltage drop of power outage work orders, and greatly improving the level of power supply service.

[0128] The above embodiments are not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the technical solution of the present invention are also within the protection scope of the present invention.

Claims

1. A method for a system with a 30-degree angle difference tie line that allows for uninterrupted loop switching power supply, characterized in that, Includes the following steps: S1. The power grid dispatcher selects the loop-closing object, automatically generates the loop-closing path power grid topology through the system's loop topology automatic generation module, and extracts the loop-closing path operating parameters through the system's operating parameter automatic acquisition module. S2. The system uses the automatic loop current calculation module to calculate the loop current according to the power flow calculation method of the dual-end power supply network based on the loop path parameters and its operating parameters. S3. Generate unloop protection settings; In addition, the principle of gradually increasing the voltage level includes: A1. Traverse upwards from the nodes of the entered loop switch to the station bus (direction 1) and the line (direction 2) respectively; A2. When tracing back to the busbar equipment If the voltage level on other sides of the transformer connected to the busbar is higher than the voltage level of the busbar, the loop path continues to trace upstream through the main transformer. If the voltage level on other sides of the transformer connected to the bus is lower than the voltage level of the bus, the loop path continues to trace upstream along the bus outgoing line interval. A3. When it is determined that the path is to trace back along the bus and there are multiple outgoing line bays on the bus, the tracing shall be carried out according to each line bay. The tracing shall continue only when the switch and disconnector at the tracing point are in the closed position. When the switch or disconnector at the opposite end is in the open position, the path is not a closed loop path and the direction shall be terminated. A4. When continuing to trace upstream through the main transformer according to the loop closing path in A2. If the other direction does not reach the main transformer, the tracing should continue from the highest voltage level side of the main transformer. If the other direction simultaneously traces back to the main transformer, a closed-loop power grid topology is formed; A5. When direction 1 and direction 2 trace back to the same busbar device, a closed-loop path network topology is formed.

2. The method for a system with a 30-degree angle difference connecting line that allows for uninterrupted power supply and loop reversal, as described in claim 1, is characterized in that: In step S1, the power grid dispatcher enters the expected loop closing switch information, the first loop closing switch information, and the second loop closing switch information in the system loop closing operation interface. The second loop closing switch information is optional. The expected loop closing switch information, the first loop closing switch information, and the second loop closing switch information each include the substation name and the line switch dual number.

3. The method for a system with a 30-degree angle difference connecting line that allows for uninterrupted power supply and loop reversal, as described in claim 2, is characterized in that: After the expected loop-closing switch information, the first loop-breaking switch information, and the second loop-breaking switch information are entered, the system traces the loop-closing topology upwards from the loop-closing switch node using external full power grid topology model data, following the principle of gradually increasing the voltage level.

4. The method for a system with a 30-degree angle difference connecting line that allows for uninterrupted power supply and loop reversal, as described in claim 2, is characterized in that... The extraction of loop-closing path operating parameters in S1 involves extracting operating data parameters related to loop closure from the real-time operating data of the entire power grid, including: Impedance of the main transformer and transmission lines; In actual power flow operation, the voltage amplitude, current amplitude, active power value, and reactive power value of each node; Each protection setting within the loop is reset to its initial value; Historical load current time-sharing data for each main transformer and line.

5. The method for a system with a 30-degree angle difference connecting line that allows for uninterrupted power supply and loop reversal, as described in claim 1, is characterized in that... In S2, when the distribution network closes at a 30-degree angle difference, the power redistribution of the two-terminal power supply networks with unequal voltage magnitudes and different phases can be considered as follows: That is, Formula 1; because ,but Formula 1 rewritten as That is, Formula 2; That is, Formula 3; In the formula, This represents the difference in voltage across the two ends; , , All are impedances; , , , All are power.

6. The method for a system with a 30-degree angle difference connecting line that allows for uninterrupted power supply and loop reversal, as described in claim 5, is characterized in that... In a two-terminal power supply network with unequal voltages at both ends, the power flowing through each end is the superposition of two power components. The system converts the extracted data information into per-unit values ​​and calculates the power flow and current values ​​of each node when the loop is closed according to Formula 3.

7. The method for a system with a 30-degree angle difference connecting line that allows for uninterrupted power supply and loop reversal, as described in claim 6, is characterized in that: The result of the loop closing current calculated in S2 is transmitted to the loop closing setting automatic generation module through the system, and the loop opening protection setting generation coefficient is selected.

8. The method for a system with a 30-degree angle difference connecting line that allows for uninterrupted power supply and loop reversal, as described in claim 7, is characterized in that: The loop-breaking protection setting value = loop-closing current / loop-breaking protection setting value generation coefficient.

9. A system for uninterrupted power supply switching with a 30-degree angle difference connecting line as described in any one of claims 1-8, characterized in that, include: Automatic loop topology generation module, automatic operating parameter acquisition module, automatic loop current calculation module, loop protection setting verification module, and automatic loop setting generation module; The automatic loop topology generation module and the automatic operating parameter acquisition module work together to automatically generate the loop power grid topology and extract the operating parameters. The automatic loop current calculation module is used to calculate the loop current. The loop protection setting verification module is used to verify the protection settings by comparing them with the maximum load current and the protection limits of the loop within the statistical period. The automatic loop closing setting generation module is used to generate loop closing protection settings.

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