Methods for detecting disturbance sources of partial voltage dips in incompletely observable power grids

Abstract

This method for detecting disturbance sources of localized voltage dips in incompletely observable power grids utilizes a synchronous phasor measurement unit (PMU) to measure positive-sequence, negative-sequence, and zero-sequence voltage and current phasors in real time and uploads the data to a wide-area real-time dynamic monitoring master station. The master station determines the dominant sequence component type causing the voltage dip. Then, based on the correlation of the largest dominant sequence current flowing into and out of the associated branches of the voltage alarm measurement point, a cascaded search is performed to identify the key branch causing the voltage dip, ultimately obtaining the original voltage or current measurement point within the monitoring range that caused the voltage dip alarm. This method can provide real-time knowledge of the disturbance nature of the voltage dip alarm and the location of the corresponding disturbance source. Based on whether the disturbance source is within the jurisdiction, it helps operators decide whether to take measures to eliminate the disturbance source, or to limit the impact of the disturbance source on the managed power grid.

Description

Technical Field

[0001] This invention belongs to the field of power grid fault diagnosis technology, and more specifically, relates to a method for detecting disturbance sources of local voltage dips in incompletely observable power grids. Background Technology

[0002] Due to the interconnectedness and layering of power grids, the actual scope of power grid dispatch and monitoring is usually not the entire power system. For example, national, regional, provincial, local, and enterprise power grids typically cannot obtain real-time power grid measurement information for areas outside their jurisdiction. Even for power grids within their jurisdiction, such as local and enterprise power grids, real-time measurement information for the large number of 0.4kV and 6kV lines and loads within their area is usually unavailable. In this situation, if a short circuit or other event occurs in a non-real-time monitored area, the resulting voltage disturbance will affect the voltage of equipment in the monitored area. However, the dispatching system in the monitored area currently lacks automated means to directly determine whether the voltage drop in the monitored power grid is caused by a fault in equipment at the upstream, same, or downstream voltage level. In other words, it is impossible to determine or locate the source of the disturbance in the monitored voltage drop.

[0003] Currently, the automatic identification of voltage dip disturbance sources relies on direct measurement of equipment experiencing grid disturbances or faults, such as short circuits, load initiation, and commutation failures, or analysis of alarm information and switch action information from relevant protection devices. However, when the faulty or disturbance source equipment is outside the monitoring range, the above information is unavailable. Therefore, existing technologies cannot achieve automatic detection of voltage dip disturbance sources and can only rely on experienced operators to make disturbance source judgments based on manually collected grid fault information after the fact. This delays fault handling time and causes the fault scope to expand. Therefore, it is necessary to study methods for detecting voltage dip disturbance sources when monitoring of faulty equipment is not possible. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for detecting disturbance sources of incompletely observable local voltage dips in power grids. This method utilizes a synchronous phasor measurement unit to measure positive-sequence, negative-sequence, and zero-sequence voltage and current phasors in real time and transmits the data to a wide-area real-time dynamic monitoring master station. The master station determines the type of dominant sequence component causing the voltage dip, and then, based on the correlation of the maximum dominant sequence component current flowing into and out of voltage nodes in the associated branches of the power grid voltage alarm measurement point, it cascades and searches to identify the key branches causing the voltage dip, ultimately obtaining the most original voltage or current measurement point within the monitoring range that caused the voltage dip alarm.

[0005] The present invention adopts the following technical solution.

[0006] The steps of the method for detecting disturbance sources of partial voltage dips in incompletely observable power grids are as follows:

[0007] Step 1: Using a synchronous phasor measurement unit (PMU), positive sequence, negative sequence, and zero sequence electrical quantity information are collected and continuously sent to the wide-area real-time dynamic monitoring master station at preset time intervals.

[0008] Step 2: Obtain the voltage drop alarm event that is the source of the disturbance to be detected;

[0009] Step 3: Determine the dominant sequence component type that caused the voltage drop alarm event, and conduct cascade detection of disturbance sources based on the positive sequence, negative sequence, and zero sequence current directions respectively;

[0010] Step 4: Output and save the disturbance source corresponding to the voltage drop alarm event.

[0011] Preferably, step 1 includes:

[0012] Step 1.1: Using a synchronous phasor measurement unit, the three-phase voltage fundamental phasors and three-phase current fundamental phasors of the monitored power grid are collected in real time at preset time intervals.

[0013] Step 1.2: Calculate the positive-sequence, negative-sequence, and zero-sequence components of voltage and current;

[0014] Step 1.3: The time-stamped voltage and current sequence component phasors are continuously transmitted to the wide-area real-time dynamic monitoring master station at preset time intervals.

[0015] The voltage sequence component phasor includes: the zero-sequence voltage phasor of the bus, the negative-sequence voltage phasor of the bus, and the positive-sequence voltage phasor of the bus;

[0016] The current sequence component phasors include: the zero-sequence current phasor of the branch, the negative-sequence current phasor of the branch, the positive-sequence current phasor of the branch, the zero-sequence current phasor of the device, the negative-sequence current phasor of the device, and the positive-sequence current phasor of the device.

[0017] Preferably, in step 2, while acquiring the voltage drop alarm event signal of the disturbance source to be detected, the number of the event-related bus should also be acquired.

[0018] Preferably, in step 3, determining the dominant sequence component type that caused the voltage dip alarm event refers to determining the fault type and the sequence component type that best reflects the fault type based on the relationship between the sequence voltage phasor of the bus associated with the voltage dip alarm event and the fault voltage threshold value. Specifically, this includes:

[0019] (1) If the zero-sequence voltage of the event-related bus is greater than the threshold value of the fault voltage sequence component, it is judged as an asymmetrical ground fault, with the zero-sequence as the dominant sequence component.

[0020] (2) If the negative sequence voltage of the event-related bus is greater than the threshold value of the fault voltage sequence component, it is judged as a phase-to-phase ungrounded short-circuit fault, with the negative sequence as the dominant sequence component.

[0021] (3) If neither of the above two criteria is met, it is judged as a symmetrical grounding fault, with the positive sequence as the dominant sequence component.

[0022] In step 3, when an asymmetrical ground fault occurs, i.e., when zero-sequence current is the dominant sequence component, cascade detection of disturbance sources is carried out based on the direction of zero-sequence current. Specifically, the wide-area real-time dynamic monitoring master station performs layer-by-layer cascade detection on the branches connected to the event-related bus based on the correlation between the maximum zero-sequence current flowing into and out of the event-related bus, determining the disturbance sources within the master station's monitoring range that cause the asymmetrical ground fault. These sources specifically include:

[0023] Step 3.1.1: Set the level number i of the cascade detection, and define the level number i of the bus that has the voltage drop alarm event as 0, which represents the initial level;

[0024] Step 3.1.2, collect data from bus A. i All connected branches flow to bus A i The zero-sequence current determines the direction of flow to bus A. i The branch with the largest zero-sequence current, b i ;

[0025] Step 3.1.3, determine the relationship with branch b. i The other busbar A connected i+1 If the fault is within the main station's monitoring range, proceed to step 3.1.4; otherwise, determine that the disturbance source of the asymmetrical ground fault is in branch b. i The direction of the external network side or the non-monitored power grid side, and the search for the source of disturbance ends;

[0026] Step 3.1.4, collect data from bus A. i+1 All connected branches flow to bus A i+1 If there is no zero-sequence current except for branch b i External flow to bus A i+1 The zero-sequence current determines that the disturbance source of the asymmetrical ground fault is in branch b. i Above; if branch b exists i External flow to bus A i+1 The zero-sequence current is selected, and the branch with the largest zero-sequence current is chosen as b. i+1 If so, set i = i + 1 and return to step 3.1.3.

[0027] In step 3, when a phase-to-phase ungrounded short-circuit fault occurs, the cascade detection of disturbance sources is carried out based on the direction of the negative sequence current, with the negative sequence current as the dominant sequence component. Specifically, the wide-area real-time dynamic monitoring master station performs layer-by-layer cascade detection on the branches connected to the event-related bus based on the correlation between the maximum negative sequence current flowing into and out of the event-related bus, determining the disturbance sources within the master station's monitoring range that caused the phase-to-phase ungrounded short-circuit fault. These sources specifically include:

[0028] Step 3.2.1: Set the level number i of the cascade search, and define the level number i of the bus where the voltage drop alarm event occurs as 0, indicating the initial level;

[0029] Step 3.2.2, collect data from bus A. i All connected branches flow to bus A i The negative sequence current determines the direction of flow to bus A. i The branch with the largest negative sequence current, b i ;

[0030] Step 3.2.3, determine the relationship with branch b. i The other busbar A connected i+1 If the fault is within the main station's monitoring range, proceed to step 3.2.4; otherwise, determine that the disturbance source of the phase-to-phase ungrounded short-circuit fault is in branch b. i The direction of the external network side or the non-monitored power grid side, and the search for the source of disturbance ends;

[0031] Step 3.2.4, collect data from bus A. i+1 All connected branches flow to bus A i+1 Negative sequence current, if there is no branch b i External flow to bus A i+1 The negative sequence current indicates that the disturbance source of the phase-to-phase ungrounded short-circuit fault is in branch b. i Above; if branch b exists i External flow to bus A i+1 Given the negative sequence current, select branch b with the largest negative sequence current. i+1 If so, set i = i + 1 and return to step 3.2.3.

[0032] In step 3, when a symmetrical grounding fault occurs, i.e., when the positive sequence is the dominant sequence component, cascade detection of disturbance sources is carried out based on the positive sequence current direction. That is, the wide-area real-time dynamic monitoring master station performs layer-by-layer cascade detection on the branches connected to the event-related bus based on the correlation of the maximum positive sequence current flowing into and out of the event-related bus, to determine the disturbance sources causing the symmetrical grounding fault within the monitoring range of the master station, specifically including:

[0033] Step 3.3.1: Set the level number i of the cascade search, and define the level number i of the bus where the voltage drop alarm event occurs as 0, indicating the initial level;

[0034] Step 3.3.2, collect data from bus A. i If there is a positive sequence current flowing out of the busbar among all the connected branches, then select the branch with the largest positive sequence current as b. i Proceed to step 3.3.3; otherwise, proceed to bus A. i The grounding point, i.e., the disturbance source, is at bus A. i ;

[0035] Step 3.3.3, determine the relationship with branch b. i The other busbar A connected i+1 Is it within the monitoring range of the main station? If it is within the monitoring range, set i = i + 1 and return to step 3.3.2; if it is not within the monitoring range, determine that the disturbance source of the symmetrical grounding short circuit fault is on bus A. i branch road b i The direction is either the external network side or the non-monitored power grid side, and the search for the source of disturbance ends.

[0036] Preferably, the preset time interval is 10ms or 20ms.

[0037] Preferably, step 4 further includes outputting and saving the grid voltage drop alarm event signal, the number of the event-associated bus, and the number of the disturbance source branch.

[0038] The beneficial effects of this invention are compared with those of the prior art:

[0039] 1. Real-time awareness of the nature of the voltage drop alarm disturbance and the specific device where the corresponding disturbance source is located; when the actual disturbance source is on the external power grid or on an unmonitored power grid, the detected "specific device where the disturbance source is located" refers to the device among the monitored devices that is closest to the actual disturbance source in electrical distance.

[0040] 2. Based on whether the disturbance source is within the jurisdiction, help operators decide whether to take measures to eliminate the disturbance source or to limit the impact of the disturbance source on the power grid under their jurisdiction; when the disturbance source is within the power grid's jurisdiction, help operators decide what measures to take to eliminate the disturbance source. Attached Figure Description

[0041] Figure 1 This is a flowchart of the method for detecting disturbance sources of partial voltage drops in an incompletely observable power grid according to the present invention.

[0042] Figure 2This invention relates to a method for detecting disturbance sources of partial voltage dips in a non-observable power grid. It is applied to voltage dip alarm events caused by phase-to-phase short circuits in the external power grid, and is a schematic diagram showing the direction and magnitude of the negative sequence current in each branch. Detailed Implementation

[0043] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be construed as limiting the scope of protection of the present application.

[0044] like Figure 1 The steps of the method for detecting disturbance sources of partial voltage drops in incompletely observable power grids are as follows:

[0045] Step 1: Using a synchronous phasor measurement unit (PMU), positive-sequence, negative-sequence, and zero-sequence electrical quantity information is collected and continuously sent to the wide-area real-time dynamic monitoring master station at preset time intervals.

[0046] Step 1 includes:

[0047] Step 1.1: Using a synchronous phasor measurement unit, the three-phase voltage fundamental phasors and three-phase current fundamental phasors of the monitored power grid are collected in real time at preset time intervals.

[0048] Step 1.2: Calculate the positive-sequence, negative-sequence, and zero-sequence components of voltage and current;

[0049] Step 1.3: The time-stamped voltage and current sequence component phasors are continuously transmitted to the wide-area real-time dynamic monitoring master station at preset time intervals.

[0050] The voltage sequence component phasor includes: the zero-sequence voltage phasor of the bus, the negative-sequence voltage phasor of the bus, and the positive-sequence voltage phasor of the bus;

[0051] The current sequence component phasors include: the zero-sequence current phasor of the branch, the negative-sequence current phasor of the branch, the positive-sequence current phasor of the branch, the zero-sequence current phasor of the device, the negative-sequence current phasor of the device, and the positive-sequence current phasor of the device.

[0052] The preset time interval is 10ms or 20ms.

[0053] It is worth noting that those skilled in the art can arbitrarily choose the preset time interval. The preset time interval of 10ms or 20ms in this invention is only a preferred but non-limiting implementation. Those skilled in the art can choose a shorter or longer preset time interval. The preset time intervals within or outside these two, as well as other alternative preset time intervals, all fall within the scope of the inventive concept of this invention.

[0054] Step 2: Obtain the voltage drop alarm event that is the source of the disturbance to be detected.

[0055] In step 2, while acquiring the voltage drop alarm event signal of the disturbance source to be detected, it is also necessary to acquire the number of the bus associated with the event.

[0056] Step 3: Determine the dominant sequence component type that caused the voltage drop alarm event, and conduct cascade detection of disturbance sources based on the positive sequence, negative sequence, and zero sequence current directions respectively.

[0057] In step 3, determining the dominant sequence component type that caused the voltage dip alarm event refers to determining the fault type and the sequence component type that best reflects the fault type based on the relationship between the sequence voltage phasor of the bus associated with the voltage dip alarm event and the fault voltage threshold value. Specifically, this includes:

[0058] (1) If the zero-sequence voltage of the event-related bus is greater than the threshold value of the fault voltage sequence component, it is judged as an asymmetrical ground fault, with the zero-sequence as the dominant sequence component.

[0059] (2) If the negative sequence voltage of the event-related bus is greater than the threshold value of the fault voltage sequence component, it is judged as a phase-to-phase ungrounded short-circuit fault, with the negative sequence as the dominant sequence component.

[0060] (3) If neither of the above two criteria is met, it is judged as a symmetrical grounding fault, with the positive sequence as the dominant sequence component.

[0061] In step 3, when an asymmetrical ground fault occurs, i.e., when zero-sequence current is the dominant sequence component, cascade detection of disturbance sources is carried out based on the direction of zero-sequence current. Specifically, the wide-area real-time dynamic monitoring master station performs layer-by-layer cascade detection on the branches connected to the event-related bus based on the correlation between the maximum zero-sequence current flowing into and out of the event-related bus, determining the disturbance sources within the master station's monitoring range that cause the asymmetrical ground fault. These sources specifically include:

[0062] Step 3.1.1: Set the level number i of the cascade detection, and define the level number i of the bus that has the voltage drop alarm event as 0, which represents the initial level;

[0063] Step 3.1.2, collect data from bus A. i All connected branches flow to bus A i The zero-sequence current determines the direction of flow to bus A. i The branch with the largest zero-sequence current, b i ;

[0064] Step 3.1.3, determine the relationship with branch b. i The other busbar A connected i+1 If the fault is within the main station's monitoring range, proceed to step 3.1.4; otherwise, determine that the disturbance source of the asymmetrical ground fault is in branch b. i The direction of the external network side or the non-monitored power grid side, and the search for the source of disturbance ends;

[0065] Step 3.1.4, collect data from bus A. i+1 All connected branches flow to bus A i+1 If there is no zero-sequence current except for branch b i External flow to bus A i+1 The zero-sequence current determines that the disturbance source of the asymmetrical ground fault is in branch b. i Above; if branch b exists i External flow to bus A i+1 The zero-sequence current is selected, and the branch with the largest zero-sequence current is chosen as b. i+1 If so, set i = i + 1 and return to step 3.1.3.

[0066] In step 3, when a phase-to-phase ungrounded short-circuit fault occurs, the cascade detection of disturbance sources is carried out based on the direction of the negative sequence current, with the negative sequence current as the dominant sequence component. Specifically, the wide-area real-time dynamic monitoring master station performs layer-by-layer cascade detection on the branches connected to the event-related bus based on the correlation between the maximum negative sequence current flowing into and out of the event-related bus, determining the disturbance sources within the master station's monitoring range that caused the phase-to-phase ungrounded short-circuit fault. These sources specifically include:

[0067] Step 3.2.1: Set the level number i of the cascade search, and define the level number i of the bus where the voltage drop alarm event occurs as 0, indicating the initial level;

[0068] Step 3.2.2, collect data from bus A. i All connected branches flow to bus A i The negative sequence current determines the direction of flow to bus A. i The branch with the largest negative sequence current, b i ;

[0069] Step 3.2.3, determine the relationship with branch b. i The other busbar A connected i+1 If the fault is within the main station's monitoring range, proceed to step 3.2.4; otherwise, determine that the disturbance source of the phase-to-phase ungrounded short-circuit fault is in branch b. i The direction of the external network side or the non-monitored power grid side, and the search for the source of disturbance ends;

[0070] Step 3.2.4, collect data from bus A. i+1 All connected branches flow to bus A i+1 Negative sequence current, if there is no branch b i External flow to bus A i+1 The negative sequence current indicates that the disturbance source of the phase-to-phase ungrounded short-circuit fault is in branch b. i Above; if branch b exists i External flow to bus Ai+1 Given the negative sequence current, select branch b with the largest negative sequence current. i+1 If so, set i = i + 1 and return to step 3.2.3.

[0071] In step 3, when a symmetrical grounding fault occurs, with the positive sequence as the dominant sequence component, cascade detection of disturbance sources is carried out based on the positive sequence current direction. Specifically, the wide-area real-time dynamic monitoring master station performs layer-by-layer cascade detection on the branches connected to the event-related bus based on the correlation between the maximum positive sequence current flowing into and out of the event-related bus, determining the disturbance sources causing the symmetrical grounding fault within the master station's monitoring range. These sources specifically include:

[0072] Step 3.3.1: Set the level number i of the cascade search, and define the level number i of the bus where the voltage drop alarm event occurs as 0, indicating the initial level;

[0073] Step 3.3.2, collect data from bus A. i If there is a positive sequence current flowing out of the busbar among all the connected branches, then select the branch with the largest positive sequence current as b. i Proceed to step 3.3.3; otherwise, proceed to bus A. i The grounding point, i.e., the disturbance source, is at bus A. i ;

[0074] Step 3.3.3, determine the relationship with branch b. i The other busbar A connected i+1 Is it within the monitoring range of the main station? If it is within the monitoring range, set i = i + 1 and return to step 3.3.2; if it is not within the monitoring range, determine that the disturbance source of the symmetrical grounding short circuit fault is on bus A. i branch road b i The direction of the external grid or the non-monitored power grid is then checked, and the search for the source of the disturbance is terminated.

[0075] Step 4: Output and save the disturbance source corresponding to the voltage drop alarm event.

[0076] Step 4 also includes outputting and saving the grid voltage drop alarm event signal, the number of the event-associated bus, and the number of the disturbance source branch.

[0077] Figure 2This invention presents a method for detecting disturbance sources of partial voltage dips in a partially observable power grid. It is applied to voltage dip alarm events caused by phase-to-phase short circuits in the external power grid. The diagram illustrates the direction and magnitude of negative sequence currents in each branch, where dashed arrows represent negative sequence currents. The thickness of the arrows indicates the magnitude of the negative sequence current, and the direction of the arrows indicates the direction of the negative sequence current. In a case where the dispatch center detected voltage dip alarm events on both the 110kV II bus and the 35kV IV bus, further voltage checks on these two bus sections revealed no significant zero-sequence voltage. However, the negative sequence voltages exceeded 5% of the rated voltage, i.e., exceeded the fault voltage sequence component threshold. Therefore, the disturbance source was detected by cascading the detection of the direction and magnitude of the negative sequence current.

[0078] from Figure 2 It can be seen that, starting from the 110kV II bus or the 35kV IV bus, the direction and magnitude of the negative sequence current in each branch can be used to deduce that the current in the 119 incoming branch of the Jiangting line is the current measurement point closest to the disturbance source within the monitoring range. Therefore, it is determined that the disturbance source is located in the external network connected to the Jiangting line and is a phase-to-phase short circuit.

[0079] The beneficial effects of this invention are compared with those of the prior art:

[0080] 1. Real-time awareness of the nature of the voltage drop alarm disturbance and the specific device where the corresponding disturbance source is located; when the actual disturbance source is on the external power grid or on an unmonitored power grid, the detected "specific device where the disturbance source is located" refers to the device among the monitored devices that is closest to the actual disturbance source in electrical distance.

[0081] 2. Based on whether the disturbance source is within the jurisdiction, help operators decide whether to take measures to eliminate the disturbance source or to limit the impact of the disturbance source on the power grid under their jurisdiction; when the disturbance source is within the power grid's jurisdiction, help operators decide what measures to take to eliminate the disturbance source.

[0082] The applicant of this invention has provided a detailed description of the embodiments of the invention in conjunction with the accompanying drawings. However, those skilled in the art should understand that the above embodiments are merely preferred embodiments of the invention. The detailed description is only intended to help readers better understand the spirit of the invention and is not intended to limit the scope of protection of the invention. On the contrary, any improvements or modifications made based on the inventive spirit of the invention should fall within the scope of protection of the invention.

Claims

1. A method for detecting disturbance sources of partial voltage dips in an incompletely observable power grid, characterized in that, The steps of the detection method are as follows: Step 1: Using a synchronous phasor measurement unit (PMU), positive-sequence, negative-sequence, and zero-sequence electrical quantity information is collected and continuously sent to the wide-area real-time dynamic monitoring master station at preset time intervals; Step 2: Obtain the voltage drop alarm event that is the source of the disturbance to be detected; Step 3: Determine the dominant sequence component type causing the voltage drop alarm event. When an asymmetrical ground fault occurs, and zero sequence is the dominant sequence component, cascade detection of disturbance sources is carried out based on the direction of zero sequence current. The wide-area real-time dynamic monitoring master station performs cascade detection layer by layer on the branches connected to the event-related bus based on the correlation of the maximum zero sequence current flowing into and out of the event-related bus, to determine the disturbance source causing the asymmetrical ground fault within the monitoring range of the master station; including: Step 3.1.1, setting the cascade detection level number. Define the level number of the bus that triggers a voltage dip alarm event. A value of 0 indicates the initial level; Step 3.1.2, data acquisition and busbar... All branches connected to the busbar The zero-sequence current determines the direction of flow to the bus. The branch with the largest zero-sequence current Step 3.1.3, determine the branch. The other busbar connected If the fault is within the main station's monitoring range, proceed to step 3.1.4; otherwise, determine that the disturbance source of the asymmetrical ground fault is in the branch circuit. The direction of the external network side or the non-monitored power grid side is checked, and the search for the disturbance source ends; Step 3.1.4, collect data on the bus. All branches connected to the busbar The zero-sequence current, if it does not exist except in the branch External flow to bus The zero-sequence current determines the disturbance source of the asymmetrical ground fault in the branch. Up; if there are branches External flow to bus The zero-sequence current is selected from the branches with the largest zero-sequence current. Then set = +1 and return to step 3.1.3; When a phase-to-phase ungrounded short-circuit fault occurs, and the negative sequence is the dominant sequence component, cascade detection of disturbance sources is carried out based on the direction of the negative sequence current. The wide-area real-time dynamic monitoring master station performs layer-by-layer cascade detection on the branches connected to the event-related bus based on the correlation between the maximum negative sequence current flowing into and out of the event-related bus, to determine the disturbance source causing the phase-to-phase ungrounded short-circuit fault within the monitoring range of the master station; including: step 3.2.1, setting the hierarchical number of the cascade search. Define the level number of the bus that triggers a voltage dip alarm event. A value of 0 indicates the initial level; Step 3.2.2, data acquisition and busbar... All branches connected to the busbar The negative sequence current determines the direction of flow to the busbar. The branch with the largest negative sequence current Step 3.2.3, determine the branch. The other busbar connected If the fault is within the main station's monitoring range, proceed to step 3.2.4; otherwise, determine that the disturbance source of the phase-to-phase ungrounded short-circuit fault is in the branch circuit. The direction of the external network side or the non-monitored power grid side is checked, and the search for the disturbance source ends; Step 3.2.4, collect data on the bus. All branches connected to the busbar Negative sequence current, if there is no branch External flow to bus The negative sequence current indicates that the disturbance source of the phase-to-phase ungrounded short-circuit fault is in the branch. Up; if there are branches External flow to bus The negative sequence current is selected, and the branch with the largest negative sequence current is chosen as the negative sequence current. Then set = +1 and return to step 3.2.3; When a symmetrical grounding fault occurs, with the positive sequence as the dominant sequence component, cascade detection of disturbance sources is carried out based on the positive sequence current direction. The wide-area real-time dynamic monitoring master station performs layer-by-layer cascade detection on the branches connected to the event-related bus based on the correlation between the maximum positive sequence current flowing into and out of the event-related bus, to determine the disturbance source causing the symmetrical grounding fault within the monitoring range of the master station; including: step 3.3.1, setting the cascade search level number. Define the level number of the bus that triggers a voltage dip alarm event. A value of 0 indicates the initial level; Step 3.3.2, data acquisition and busbar... If a positive sequence current flows out of the busbar from all connected branches, select the branch with the largest positive sequence current as the busbar. Proceed to step 3.3.3; otherwise, the busbar... The grounding point, i.e., the source of disturbance, is on the busbar. Step 3.3.3, determine the branch. The other busbar connected Is it within the main station's monitoring range? If it is, then set... = +1, return to step 3.3.2; if it is not within the monitoring range, then determine that the disturbance source of the symmetrical grounding short circuit fault is on the busbar. branch road The direction of the external network side or the non-monitored power grid side, and the search for the source of disturbance ends; Step 4: Output and save the disturbance source corresponding to the voltage drop alarm event.

2. The method for detecting disturbance sources of incompletely observable local voltage dips in a power grid according to claim 1, characterized in that, Step 1 includes: Step 1.1: Using a synchronous phasor measurement unit, the three-phase voltage fundamental phasors and three-phase current fundamental phasors of the monitored power grid are collected in real time at preset time intervals. Step 1.2: Calculate the positive-sequence, negative-sequence, and zero-sequence components of voltage and current; Step 1.3: The time-stamped voltage and current sequence component phasors are continuously transmitted to the wide-area real-time dynamic monitoring master station at preset time intervals.

3. The method for detecting disturbance sources of incompletely observable local voltage dips in a power grid according to claim 2, characterized in that, The voltage sequence component phasor includes: the zero-sequence voltage phasor of the bus, the negative-sequence voltage phasor of the bus, and the positive-sequence voltage phasor of the bus; The current sequence component phasors include: the zero-sequence current phasor of the branch, the negative-sequence current phasor of the branch, the positive-sequence current phasor of the branch, the zero-sequence current phasor of the device, the negative-sequence current phasor of the device, and the positive-sequence current phasor of the device.

4. The method for detecting disturbance sources of incompletely observable local voltage dips in a power grid according to claim 1, characterized in that, In step 2, while acquiring the voltage drop alarm event signal of the disturbance source to be detected, it is also necessary to acquire the number of the bus associated with the event.

5. The method for detecting disturbance sources of incompletely observable local voltage dips in a power grid according to claim 4, characterized in that, In step 3, determining the dominant sequence component type that caused the voltage dip alarm event refers to determining the fault type and the sequence component type that best reflects the fault type based on the relationship between the sequence voltage phasor of the bus associated with the voltage dip alarm event and the fault voltage threshold value. Specifically, this includes: (1) If the zero-sequence voltage of the event-related bus is greater than the threshold value of the fault voltage sequence component, it is judged as an asymmetrical ground fault, and the zero-sequence is the dominant sequence component; (2) If the negative sequence voltage of the event-related bus is greater than the threshold value of the fault voltage sequence component, it is judged as a phase-to-phase ungrounded short-circuit fault, with the negative sequence as the dominant sequence component; (3) If neither of the above two criteria is met, it is judged as a symmetrical grounding fault, with the positive sequence as the dominant sequence component.

6. The method for detecting disturbance sources of incompletely observable local voltage dips in a power grid according to claim 1 or 2, characterized in that, The preset time interval is 10ms or 20ms.

7. The method for detecting disturbance sources of incompletely observable local voltage dips in a power grid according to claim 1, characterized in that, Step 4 also includes outputting and saving the grid voltage drop alarm event signal, the number of the event-associated bus, and the number of the disturbance source branch.

Images