A detuning device and method for suppressing ferromagnetic resonance in power system

Abstract

The present invention provides a detuning device and method for suppressing ferromagnetic resonance in an electric power system, and relates to the technical field of safety prevention and control of electric power systems. The detuning device for suppressing ferromagnetic resonance in an electric power system comprises: a detuning module for consuming the energy generated by ferromagnetic resonance; a collection module; a detection module for real-time detection of the excitation surge current between the neutral point of the voltage transformer and the high-voltage damping resistor; a calculation module for calculating the rising edge slope of the excitation surge current and calculating the offset voltage of the neutral point to the ground; a judgment module for the judgment module to continue to judge the relationship between the numerical values ​​of the rising edge slope of the excitation surge current and the offset voltage of the neutral point to the ground detected in real time and each threshold value, and judge whether a single-phase grounding fault occurs in the system; and a control module for controlling the input of the detuning module. The detuning device can accurately and quickly eliminate ferromagnetic resonance, and effectively improve the detuning efficiency of ferromagnetic resonance.

Description

Technical Field

[0001] The present invention relates to the technical field of power system safety prevention and control, and in particular to a detuning device and method for suppressing ferromagnetic resonance in a power system. Background Art

[0002] In the medium-voltage distribution network system of 10kV to 35kV, the neutral point is usually ungrounded, and the voltage transformer (PT) used for bus monitoring is an iron core inductor. When the bus switch is closed asynchronously, a single-phase grounding fault disappears in the line, or the load fluctuates violently, the nonlinear excitation impedance of the PT and the ground capacitance of the system form a ferromagnetic resonance circuit, causing system resonant overvoltage and PT overcurrent, resulting in discharge breakdown of weak insulation equipment in the power grid and melting of the PT high-voltage fuse, and even burning of the body. Therefore, a detuning device for suppressing ferromagnetic resonance in the power system is used to prevent harm to the system operation and the personal safety of operators when the system fails. The existing detuning method will not only prolong the detuning time and increase the detuning cost, but also greatly affect the detuning efficiency, causing frequent damage to the equipment, and posing a serious threat to the safe and stable operation of the power grid and equipment. Summary of the invention

[0003] Technical issues solved:

[0004] In view of the deficiencies in the prior art, the present invention provides a detuning device and method for suppressing ferromagnetic resonance in an electric power system, which solves the problem that the existing detuning method not only prolongs the detuning time and increases the detuning cost, but also greatly affects the detuning efficiency, causing frequent damage to equipment, and posing a serious threat to the safe and stable operation of the power grid and equipment.

[0005] Technical solution: To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0006] In a first aspect, a detuning device for suppressing ferromagnetic resonance in an electric power system is provided, the device comprising:

[0007] Detuning module, used to consume the energy generated by ferromagnetic resonance;

[0008] The acquisition module is used to collect the PT triangle opening voltage, the switch status signal neutral point displacement voltage, the resistance branch current and the zero sequence current;

[0009] A detection module is used to detect the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor in real time. When the detection module detects the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor, the detection result is fed back to the calculation module;

[0010] A calculation module, used to calculate the rising edge slope of the excitation inrush current, and also used to calculate the neutral point to ground offset voltage according to the PT triangle opening voltage, the switch state signal neutral point displacement voltage, the resistance branch current and the zero sequence current;

[0011] A judgment module, used for the judgment module to continue to judge the relationship between the rising edge slope of the excitation inrush current and the numerical value of the offset voltage of the neutral point to the ground detected in real time and each threshold value; the judgment module includes a first judgment module and a second judgment module, the first judgment module is used to judge whether the rising edge slope of the excitation inrush current exceeds a preset dynamic trigger threshold, the second judgment module is used to judge whether the offset voltage of the neutral point to the ground exceeds a preset voltage threshold, and the first judgment module and the second judgment module are used to judge whether a single-phase grounding fault occurs in the system;

[0012] The control module is used to control the input of the harmonic elimination module when it is determined that a single-phase grounding fault occurs in the system.

[0013] Preferably, the detuning module includes an impedance R connected at both ends of the PT open delta winding. Z , the impedance R Z A topological structure including an inductor L0 and a resistor R0 connected in parallel.

[0014] Preferably, the impedance R Z It also includes a resistor R1 connected in series with the resistor R0 and a resistor R2 connected in series with the inductor L0, a switch K2 is connected in parallel at both ends of the resistor R1, and a switch K3 is connected in parallel at both ends of the resistor R2. The input end of the parallel circuit of the inductor L0 and the resistor R0 is provided with a switch K1, wherein in normal operation, the switch K1 is opened, and the switches K2 and K3 are closed.

[0015] Preferably, it also includes a primary detuning module connected in series with the neutral point of the PT, the primary detuning module is composed of a current-sensitive detuning device and a built-in CT, the detection module is also used to collect the operating status of the primary detuning module, and detect the current value flowing through the primary detuning module and record the waveform to determine whether the primary detuning module is in a normal state; when the current flowing through the current-sensitive detuning device increases, the resistance value of the resistor in the current-sensitive detuning device increases rapidly, completing the primary detuning action.

[0016] Preferably, the calculation formula for the rising edge slope of the excitation inrush current is:

[0017] ,

[0018] in, is the current change between two adjacent sampling points, is the time interval between two adjacent sampling points.

[0019] Preferably, the dynamic trigger threshold is used to determine whether to trigger the detuning action, and the calculation formula of the dynamic trigger threshold is:

[0020] ,

[0021] in, is the dynamic trigger threshold, For the queue Slope data, is the corresponding weight coefficient, is the length of the slope data queue, is a constant less than 1.

[0022] Preferably, the control module controls the input of the detuning module according to the judgment result of the judgment module, and the specific process is as follows:

[0023] If the first judgment module determines that the rising edge slope of the excitation inrush current is greater than or equal to the preset dynamic trigger threshold or the second judgment module determines that the offset voltage of the neutral point to the ground is greater than or equal to the preset voltage threshold, the judgment result is sent to the control module, the control module controls the input of the detuning module, and the judgment module continues to judge the magnitude relationship between the magnitude of the real-time detected excitation inrush current and the offset voltage of the neutral point to the ground and each threshold;

[0024] If the first judgment module determines that the rising edge slope of the excitation surge current is less than the preset dynamic trigger threshold and the second judgment module determines that the offset voltage of the neutral point to the ground is less than the preset voltage threshold, the judgment module continues to determine the relationship between the numerical values ​​of the excitation surge current and the offset voltage of the neutral point to the ground detected in real time and the magnitude of each threshold.

[0025] Preferably, the detection module is also used to detect the duration of a single-phase grounding fault in the system, and the judgment module also includes a third judgment module, and the third judgment module is used to judge whether the duration of the single-phase grounding fault in the system exceeds a preset time threshold. When the duration of the single-phase grounding fault is greater than or equal to the preset time threshold, the third judgment module sends the detection result to the control module, and the control module controls the disconnection of switch K2 and switch K3, and puts resistors R1 and R2 into operation.

[0026] In a second aspect, a detuning method of a detuning device for suppressing ferromagnetic resonance in an electric power system is provided, the method comprising:

[0027] Collect PT triangle opening voltage, switch status signal neutral point displacement voltage, resistance branch current and zero sequence current;

[0028] Calculate the offset voltage of the neutral point to ground;

[0029] Real-time detection of the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor;

[0030] When the detection module detects the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor, the rising edge slope of the excitation inrush current is calculated;

[0031] Determine whether the rising edge slope of the excitation inrush current exceeds a preset dynamic trigger threshold, and determine whether the offset voltage of the neutral point to the ground exceeds a preset voltage threshold;

[0032] The input of the detuning module is controlled according to the judgment result.

[0033] Furthermore, controlling the input of the harmonic elimination module according to the judgment result specifically includes:

[0034] If it is determined that the rising edge slope of the excitation inrush current is greater than or equal to the preset dynamic trigger threshold or the second judgment module determines that the offset voltage of the neutral point to the ground is greater than or equal to the preset voltage threshold, the judgment result is sent to the control module, the control module controls the input of the detuning module, and the judgment module continues to judge the magnitude relationship between the magnitude of the real-time detected excitation inrush current and the offset voltage of the neutral point to the ground and each threshold;

[0035] If it is determined that the rising edge slope of the excitation surge current is less than the preset dynamic trigger threshold and the second judgment module determines that the offset voltage of the neutral point to the ground is less than the preset voltage threshold, the judgment module continues to judge the relationship between the numerical values ​​of the excitation surge current and the offset voltage of the neutral point to the ground detected in real time and the magnitude of each threshold.

[0036] Furthermore, the method further comprises:

[0037] Detect the duration of a single-phase ground fault in the system;

[0038] It is determined whether the duration of the single-phase grounding fault in the system exceeds the preset time threshold. When the duration of the single-phase grounding fault is greater than or equal to the preset time threshold, the third judgment module sends the detection result to the control module, and the control module controls the disconnection of switch K2 and switch K3, and puts resistors R1 and R2 into operation.

[0039] Beneficial effects: (1) The present invention provides a detuning device and method for suppressing ferromagnetic resonance in an electric power system. When the system is operating normally, the switch K1 is in an off state, ensuring that the normal measurement signal of the voltage transformer is not affected. When the system resonates, the values ​​of the resistor R1 and the inductor L0 in the detuning module are very small, and the two ends of the PT open delta winding are equivalent to short-circuiting, which can play a good detuning role.

[0040] (2) The present invention provides a detuning device and method for suppressing ferromagnetic resonance in an electric power system. When the system is operating normally, switches K2 and K3 are closed. When a permanent single-phase grounding fault occurs in the line, switches K2 and K3 are disconnected, and two large resistors (resistors R1 and R2) are switched on. The open delta winding is turned on through the inductor L0 in series with the resistor R2 and the parallel high resistor (the resistor R0 and the resistor R1 are connected in series). The neutral point is converted to ground through the inductor L0 in series with the resistor R2 and the parallel high resistor. The damping rate of the system is reduced, which can ensure that the neutral point displacement voltage will not be too high, thereby protecting the system.

[0041] (3) The present invention provides a detuning device and method for suppressing ferromagnetic resonance in an electric power system. The detuning device and method can detect and calculate the excitation surge current between the neutral point of the voltage transformer and the high-voltage damping resistor and the offset voltage between the neutral point and the ground, respectively, to determine whether the system is resonant and control the rapid activation of the detuning module, thereby accurately and quickly eliminating ferromagnetic resonance and effectively improving the detuning efficiency of ferromagnetic resonance. The existing detuning method not only prolongs the detuning time and increases the detuning cost, but also greatly affects the detuning efficiency, causing frequent damage to the equipment and posing a serious threat to the safe and stable operation of the power grid and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a module diagram of a detuning device for suppressing ferromagnetic resonance in a power system according to the present invention;

[0043] Figure 2 This is a schematic diagram of the structure of the harmonic elimination module connected to both ends of the PT open delta winding of the present invention;

[0044] Figure 3 The ferromagnetic resonance circuit diagram of the voltage transformer with Y0 connection of the present invention;

[0045] Figure 4 The ferromagnetic resonance equivalent circuit diagram of the voltage transformer with Y0 connection of the present invention;

[0046] Figure 5 This is a connection circuit diagram of the primary harmonic elimination module of the present invention;

[0047] Figure 6 This is a flow chart of the harmonic elimination method of the present invention;

[0048] Figure 7 This is the control principle diagram of the harmonic elimination device of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the accompanying drawings of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] See also Figure 3-Figure 4 , the ferromagnetic resonance generation principle studied in this application is as follows:

[0051] In the distribution network system with ungrounded neutral point, the substation bus is connected with an electromagnetic voltage transformer for monitoring the three-phase voltage, and the three windings are connected in a Y0 / Y0 / Δ connection. The system ground parameters include the line-to-ground capacitance C0 and the excitation inductance L of the voltage transformer. The equivalent circuit is as follows: Figure 3 As shown. C0 and L are connected in parallel, each forming an independent oscillation circuit. During normal operation, the three phases are basically balanced, and the offset voltage of the neutral point to the ground is very small. When the system is disturbed and the neutral point of the power grid has a higher offset voltage, a large saturation current will flow through the PT high-voltage winding, causing the excitation impedance to drop sharply. When it matches the line parameters, ferromagnetic resonance will be excited. Ferromagnetic resonance overvoltage is caused by the zero-sequence voltage caused by the different saturation levels of the three phases of the voltage transformer, and is only related to the zero-sequence circuit parameters. Therefore, the capacitor bank connected between phases to improve the power factor, the load transformer, and the active and reactive loads have no effect on the ferromagnetic resonance overvoltage. These parameters are Figure 3 Not included in.

[0052] See also Figure 3 , e A , e B and e C is the winding potential of the power transformer, is the three-phase positive sequence voltage, and always remains constant. i A , i B and i C is the three-phase output current of the power transformer, i 1. i 2 and i 3 is the three-phase current of the primary side of the voltage transformer, i 0 is the zero-sequence current on the secondary side of the voltage transformer, E 0 is the offset voltage of the neutral point O to the ground. Figure 3 The circuit can get the three-phase output current of the power transformer:

[0053] (1) ,

[0054] For the power transformer, there are Combined with equation (1), we can get the relationship between the offset voltage and the three-phase current on the primary side of the voltage transformer (2).

[0055] (2) ,

[0056] The magnetic potential balance of the voltage transformer,

[0057] (3) ,

[0058] In formula (3), i L1 , i L2 and i L3 is the excitation current of the voltage transformer, L 1. L 2 and L 3 is the excitation inductance of the voltage transformer, so:

[0059] (4) ,

[0060] Combining equations (2) and (3), we get the current equation of the resonant circuit:

[0061] (5) ,

[0062] Zero-sequence current on the secondary side of voltage transformer i 0 offset voltage from neutral point E 0 The relationship is:

[0063] (6) ,

[0064] Combining equations (5) and (6), we can further obtain the current equation of the resonant circuit:

[0065] (7) ,

[0066] Combining equations (4) and (7), we can further obtain the neutral point offset voltage of the resonant circuit:

[0067] (8) ,

[0068] Correspondingly, the equivalent circuit of PT ferromagnetic resonance is as follows: Figure 4 shown.

[0069] From formula (8), we can see that when the system operates normally, the excitation impedance of the PT is large and the three-phase parameters are symmetrical, that is, L 1=L 2= L 3. At this time, the displacement voltage E 0 is zero, and no overvoltage will occur. However, when certain disturbances occur in the system (such as asynchronous closing of the bus switch, single-phase grounding fault in the line, or severe load fluctuations), the three-phase load to ground may become unbalanced, thereby generating a zero-sequence voltage, making the instantaneous voltage on the high-voltage side of the voltage transformer no longer symmetrical, the zero-sequence current continues to increase, the voltage transformer core has different degrees of magnetic saturation, the excitation impedance decreases, and when the parameters of the capacitor and inductor match, ferromagnetic resonance is excited, causing overvoltage. The resistor R connected at both ends of the PT open delta winding Z It has the function of damping and suppressing resonance.

[0070] See also Figure 4 It can be seen that the resistance R Z is the equivalent resistance of the neutral point of the power grid to the ground. Z When it is zero, it is equivalent to the neutral point of the power grid being directly grounded, and the high-voltage side of the PT always maintains a constant three-phase positive sequence voltage of the power transformer. The PT cannot be saturated and will not excite ferromagnetic resonance. At this time, the PT open delta winding is short-circuited.

[0071] According to the mechanism of ferromagnetic resonance studied above, the resistor R connected at both ends of the PT open triangle winding Z It has the function of damping and suppressing resonance. Figure 1 As shown, one embodiment of the present invention provides a detuning device for suppressing ferromagnetic resonance in an electric power system, the device comprising:

[0072] Detuning module, used to consume the energy generated by ferromagnetic resonance;

[0073] The acquisition module is used to collect the PT triangle opening voltage, the switch status signal neutral point displacement voltage, the resistance branch current and the zero sequence current;

[0074] A detection module is used to detect the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor in real time. When the detection module detects the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor, the detection result is fed back to the calculation module;

[0075] Calculation module, used to calculate the rising slope of the excitation inrush current It is also used to calculate the neutral point to ground offset voltage based on the PT triangle opening voltage, the switch status signal neutral point displacement voltage, the resistance branch current and the zero sequence current. E 0 ;

[0076] A judgment module, used for the judgment module to continue to judge the relationship between the rising edge slope of the excitation inrush current and the numerical value of the offset voltage of the neutral point to the ground detected in real time and each threshold value; the judgment module includes a first judgment module and a second judgment module, the first judgment module is used to judge whether the rising edge slope of the excitation inrush current exceeds the preset dynamic trigger threshold The second judgment module is used to judge whether the offset voltage of the neutral point to the ground exceeds a preset voltage threshold. , judging whether a single-phase grounding fault occurs in the system through the first judging module and the second judging module;

[0077] The control module is used to control the input of the harmonic elimination module when it is determined that a single-phase grounding fault occurs in the system.

[0078] See also Figure 2 Furthermore, the detuning module includes an impedance R connected at both ends of the PT open delta winding. Z , the impedance R Z A topological structure including an inductor L0 and a resistor R0 connected in parallel.

[0079] Furthermore, the impedance R Z It also includes a resistor R1 connected in series with the resistor R0 and a resistor R2 connected in series with the inductor L0, a switch K2 is connected in parallel at both ends of the resistor R1, and a switch K3 is connected in parallel at both ends of the resistor R2. The input end of the parallel circuit of the inductor L0 and the resistor R0 is provided with a switch K1, wherein in normal operation, the switch K1 is opened, and the switches K2 and K3 are closed.

[0080] Furthermore, the calculation formula for the rising edge slope of the excitation inrush current is:

[0081] (9) ,

[0082] in, is the current change between two adjacent sampling points, is the time interval between two adjacent sampling points.

[0083] Furthermore, the dynamic trigger threshold is used to determine whether to trigger the detuning action, and the calculation formula of the dynamic trigger threshold is:

[0084] (10) ,

[0085] (11) ,

[0086] in, is the dynamic trigger threshold, For the queue Slope data, is the corresponding weight coefficient, is the length of the slope data queue, is a constant less than 1.

[0087] Furthermore, the control module controls the input of the detuning module according to the judgment result of the judgment module. The specific process is as follows:

[0088] If the first judgment module determines that the rising edge slope of the excitation inrush current is greater than or equal to the preset dynamic trigger threshold or the second judgment module determines that the offset voltage of the neutral point to the ground is greater than or equal to the preset voltage threshold, the judgment result is sent to the control module, the control module controls the input of the detuning module, and the judgment module continues to judge the magnitude relationship between the magnitude of the real-time detected excitation inrush current and the offset voltage of the neutral point to the ground and each threshold;

[0089] If the first judgment module determines that the rising edge slope of the excitation surge current is less than the preset dynamic trigger threshold and the second judgment module determines that the offset voltage of the neutral point to the ground is less than the preset voltage threshold, the judgment module continues to determine the relationship between the numerical values ​​of the excitation surge current and the offset voltage of the neutral point to the ground detected in real time and the magnitude of each threshold.

[0090] Furthermore, the detection module is also used to detect the duration of a single-phase grounding fault in the system. The judgment module also includes a third judgment module, which is used to judge whether the duration of a single-phase grounding fault in the system exceeds a preset time threshold. When the duration of the single-phase grounding fault is greater than or equal to the preset time threshold, the third judgment module sends the detection result to the control module, and the control module controls the disconnection of switch K2 and switch K3, and puts resistors R1 and R2 into operation.

[0091] See also Figure 5 The detuning device for suppressing ferromagnetic resonance in the power system also includes a primary detuning module connected in series to the neutral point of the PT, the primary detuning module is composed of a current-sensitive detuning device and a built-in CT, the detection module is also used to collect the operating status of the primary detuning module, and detect the current value flowing through the primary detuning module and record the waveform to determine whether the primary detuning module is in a normal state; when the current flowing through the current-sensitive detuning device increases, the resistance value in the current-sensitive detuning device increases rapidly to complete the primary detuning action; the primary detuning module is connected in series to the neutral point of the PT, The primary detuning module is composed of a flow-sensitive detuning device and a built-in CT. The detection module is also used to collect the operating status of the primary detuning module, detect the current value flowing through the primary detuning module and record the waveform. The primary detuning module is specifically a flow-sensitive detuning device. The flow-sensitive detuning device uses a flow-sensitive detuning resistor inside. The flow-sensitive detuning resistor contains zinc oxide material. When the current increases, the resistance of the flow-sensitive detuning resistor increases rapidly, thereby performing rapid detuning. When the current decreases, the resistance of the flow-sensitive detuning resistor also decreases, thereby avoiding affecting the operation of the system.

[0092] When in use, the acquisition module collects the PT triangle opening voltage, the neutral point displacement voltage of the switch state signal, the resistance branch current and the zero-sequence current; the detection module detects the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor in real time, as well as the working current of the primary detuning module. Under normal circumstances, the primary detuning module and the secondary detuning element (detuning module) have no effect on the system. If PT ferromagnetic resonance occurs, the primary detuning module will play an immediate elimination role before the detuning module. The acquisition module detects that it is a ferromagnetic resonance of a certain frequency, starts the secondary detuning element (detuning module), issues an alarm, displays and automatically stores relevant data. At the same time, the detection module detects whether the current value flowing through the primary detuning module is within the normal range, determines whether the primary detuning module is in a normal state, detects the current value flowing through the primary detuning module and records the waveform.

[0093] The intelligent monitoring center is installed on a guide rail in the secondary room of the PT cabinet. It collects the three-phase voltage and open voltage on the secondary side of the PT in real time, as well as the working current of the current-sensitive harmonic eliminator. It monitors the operating status of the power grid and the current-sensitive harmonic eliminator in real time. It also has the functions of fault identification, fault alarm, and fault recording.

[0094] See also Figure 6 Another embodiment of the present invention provides a detuning method of a detuning device for suppressing ferromagnetic resonance in an electric power system, the method comprising:

[0095] Collect PT triangle opening voltage, switch status signal neutral point displacement voltage, resistance branch current and zero sequence current;

[0096] Calculate the offset voltage of the neutral point to ground;

[0097] Real-time detection of the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor;

[0098] When the detection module detects the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor, the rising edge slope of the excitation inrush current is calculated;

[0099] Determine whether the rising edge slope of the excitation inrush current exceeds a preset dynamic trigger threshold, and determine whether the offset voltage of the neutral point to the ground exceeds a preset voltage threshold;

[0100] The input of the detuning module is controlled according to the judgment result.

[0101] Furthermore, the input of the harmonic elimination module is controlled according to the judgment result, specifically including:

[0102] If it is determined that the rising edge slope of the excitation inrush current is greater than or equal to the preset dynamic trigger threshold or the second judgment module determines that the offset voltage of the neutral point to the ground is greater than or equal to the preset voltage threshold, the judgment result is sent to the control module, the control module controls the input of the detuning module, and the judgment module continues to judge the magnitude relationship between the magnitude of the real-time detected excitation inrush current and the offset voltage of the neutral point to the ground and each threshold;

[0103] If it is determined that the rising edge slope of the excitation surge current is less than the preset dynamic trigger threshold and the second judgment module determines that the offset voltage of the neutral point to the ground is less than the preset voltage threshold, the judgment module continues to judge the relationship between the numerical values ​​of the excitation surge current and the offset voltage of the neutral point to the ground detected in real time and the magnitude of each threshold.

[0104] Furthermore, the method also includes:

[0105] Detect the duration of a single-phase ground fault in the system;

[0106] It is determined whether the duration of the single-phase grounding fault in the system exceeds the preset time threshold. When the duration of the single-phase grounding fault is greater than or equal to the preset time threshold, the third judgment module sends the detection result to the control module, and the control module controls the disconnection of switch K2 and switch K3, and puts resistors R1 and R2 into operation.

[0107] See also Figure 7 , is a control principle diagram of the harmonic elimination device of the present invention. From this figure, it can be seen that the working process of the harmonic elimination device of the present invention in actual application is:

[0108] First, the detuning device of the present application is installed in the power system, and the detuning device is started. By collecting the PT triangle opening voltage, the neutral point displacement voltage of the switch state signal, the resistance branch current and the zero-sequence current, the offset voltage of the neutral point to the ground is calculated, and the excitation surge current between the neutral point of the voltage transformer and the high-voltage damping resistor is detected in real time. When the detection module detects the excitation surge current between the neutral point of the voltage transformer and the high-voltage damping resistor, the rising edge slope of the excitation surge current is calculated; it is judged that the rising edge slope of the excitation surge current is greater than or equal to the preset dynamic trigger threshold, and the offset voltage of the neutral point to the ground is greater than or equal to the preset voltage threshold. When one of the conditions is met, the switch K1 is closed and the detuning module is put into the power system; the rising edge slope of the excitation surge current is continued to be judged. Greater than or equal to the preset dynamic trigger threshold , the offset voltage of the neutral point to ground is greater than or equal to the preset voltage threshold , when one of the conditions is met and the duration t of the single-phase ground fault is greater than or equal to the preset time threshold , then disconnect switch K2 and switch K3, and put resistors R1 and R2 into operation; select the faulty line and cut it off; when the system returns to normal, disconnect switch K1, close switch K2 and switch K3, and the detuning device continues to monitor and protect the power system. Thus, ferromagnetic resonance can be eliminated accurately and quickly, and the detuning efficiency of ferromagnetic resonance can be effectively improved. It also solves the problem that the existing detuning method not only prolongs the detuning time and increases the detuning cost, but also greatly affects the detuning efficiency, causing frequent damage to the equipment, and posing a serious threat to the safe and stable operation of the power grid and equipment.

[0109] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. A detuning device for suppressing ferromagnetic resonance in an electric power system, characterized in that: include: Detuning module, used to consume the energy generated by ferromagnetic resonance; The acquisition module is used to collect the PT triangle opening voltage, the switch status signal neutral point displacement voltage, the resistance branch current and the zero sequence current; A detection module is used to detect the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor in real time. When the detection module detects the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor, the detection result is fed back to the calculation module; A calculation module, used to calculate the rising edge slope of the excitation inrush current, and also used to calculate the neutral point to ground offset voltage according to the PT triangle opening voltage, the switch state signal neutral point displacement voltage, the resistance branch current and the zero sequence current; A judgment module, used for the judgment module to continue to judge the relationship between the rising edge slope of the excitation inrush current and the numerical value of the offset voltage of the neutral point to the ground detected in real time and each threshold value; the judgment module includes a first judgment module and a second judgment module, the first judgment module is used to judge whether the rising edge slope of the excitation inrush current exceeds a preset dynamic trigger threshold, the second judgment module is used to judge whether the offset voltage of the neutral point to the ground exceeds a preset voltage threshold, and the first judgment module and the second judgment module are used to judge whether a single-phase grounding fault occurs in the system; A control module is used to control the input of the harmonic elimination module when it is determined that a single-phase grounding fault occurs in the system; The detuning module includes an impedance R connected at both ends of the PT open delta winding. Z , the impedance R Z A topological structure including an inductor L0 and a resistor R0 connected in parallel; The impedance R Z It also includes a resistor R1 connected in series with the resistor R0 and a resistor R2 connected in series with the inductor L0, a switch K2 is connected in parallel at both ends of the resistor R1, and a switch K3 is connected in parallel at both ends of the resistor R2, and the input end of the parallel circuit of the inductor L0 and the resistor R0 is provided with a switch K1, wherein when the system is operating normally, the switch K1 is opened, and the switches K2 and K3 are closed; The detection module is also used to detect the duration of a single-phase grounding fault in the system. The judgment module also includes a third judgment module. The third judgment module is used to judge whether the duration of a single-phase grounding fault in the system exceeds a preset time threshold. When the duration of the single-phase grounding fault is greater than or equal to the preset time threshold, the third judgment module sends the detection result to the control module. The control module controls the disconnection of switch K2 and switch K3 and puts resistors R1 and R2 into operation.

2. A detuning device for suppressing ferromagnetic resonance in a power system according to claim 1, characterized in that: The calculation formula of the rising edge slope of the excitation inrush current is: ， in, is the current change between two adjacent sampling points, is the time interval between two adjacent sampling points.

3. A detuning device for suppressing ferromagnetic resonance in a power system according to claim 2, characterized in that: The dynamic trigger threshold is used to determine whether to trigger the detuning action. The calculation formula of the dynamic trigger threshold is: ， in, is the dynamic trigger threshold, For the queue Slope data, is the corresponding weight coefficient, is the length of the slope data queue, is a constant less than 1.

4. A detuning device for suppressing ferromagnetic resonance in a power system according to claim 3, characterized in that: The control module controls the input of the detuning module according to the judgment result of the judgment module. The specific process is as follows: If the first judgment module determines that the rising edge slope of the excitation inrush current is greater than or equal to the preset dynamic trigger threshold or the second judgment module determines that the offset voltage of the neutral point to the ground is greater than or equal to the preset voltage threshold, the judgment result is sent to the control module, the control module controls the input of the detuning module, and the judgment module continues to judge the magnitude relationship between the magnitude of the real-time detected excitation inrush current and the offset voltage of the neutral point to the ground and each threshold; If the first judgment module determines that the rising edge slope of the excitation surge current is less than the preset dynamic trigger threshold and the second judgment module determines that the offset voltage of the neutral point to the ground is less than the preset voltage threshold, the judgment module continues to determine the relationship between the numerical values ​​of the excitation surge current and the offset voltage of the neutral point to the ground detected in real time and the magnitude of each threshold.

5. A detuning device for suppressing ferromagnetic resonance in a power system according to claim 1, characterized in that: It also includes a primary harmonic elimination module connected in series to the neutral point of the PT, the primary harmonic elimination module is composed of a current-sensitive harmonic elimination device and a built-in CT, the detection module is also used to collect the operating status of the primary harmonic elimination module, and detect the current value flowing through the primary harmonic elimination module and record the waveform to determine whether the primary harmonic elimination module is in a normal state; when the current flowing through the current-sensitive harmonic elimination device increases, the resistance value of the resistor in the current-sensitive harmonic elimination device increases rapidly, completing the primary harmonic elimination action.

6. A detuning method for suppressing ferromagnetic resonance in a power system based on a detuning device according to any one of claims 1 to 5, characterized in that: The method comprises: Collect PT triangle opening voltage, switch status signal neutral point displacement voltage, resistance branch current and zero sequence current; Calculate the offset voltage of the neutral point to ground; Real-time detection of the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor; When the detection module detects the excitation inrush current between the neutral point of the voltage transformer and the high-voltage damping resistor, the rising edge slope of the excitation inrush current is calculated; Determine whether the rising edge slope of the excitation inrush current exceeds a preset dynamic trigger threshold, and determine whether the offset voltage of the neutral point to the ground exceeds a preset voltage threshold; Control the input of the detuning module according to the judgment result; The detuning module includes an impedance R connected at both ends of the PT open delta winding. Z , the impedance R Z A topological structure including an inductor L0 and a resistor R0 connected in parallel; The impedance R Z It also includes a resistor R1 connected in series with the resistor R0 and a resistor R2 connected in series with the inductor L0, a switch K2 is connected in parallel at both ends of the resistor R1, and a switch K3 is connected in parallel at both ends of the resistor R2, and the input end of the parallel circuit of the inductor L0 and the resistor R0 is provided with a switch K1, wherein when the system is operating normally, the switch K1 is opened, and the switches K2 and K3 are closed; The method further comprises: Detect the duration of a single-phase ground fault in the system; It is determined whether the duration of the single-phase grounding fault in the system exceeds the preset time threshold. When the duration of the single-phase grounding fault is greater than or equal to the preset time threshold, the third judgment module sends the detection result to the control module, and the control module controls the disconnection of switch K2 and switch K3, and puts resistors R1 and R2 into operation.

7. The method for eliminating harmonics according to claim 6, characterized in that: The step of controlling the input of the harmonic elimination module according to the judgment result specifically includes: If it is determined that the rising edge slope of the excitation inrush current is greater than or equal to the preset dynamic trigger threshold or the second judgment module determines that the offset voltage of the neutral point to the ground is greater than or equal to the preset voltage threshold, the judgment result is sent to the control module, the control module controls the input of the detuning module, and the judgment module continues to judge the magnitude relationship between the magnitude of the real-time detected excitation inrush current and the offset voltage of the neutral point to the ground and each threshold; If it is determined that the rising edge slope of the excitation surge current is less than the preset dynamic trigger threshold and the second judgment module determines that the offset voltage of the neutral point to the ground is less than the preset voltage threshold, the judgment module continues to judge the relationship between the numerical values ​​of the excitation surge current and the offset voltage of the neutral point to the ground detected in real time and the magnitude of each threshold.

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