Method, device and equipment for identifying low-frequency oscillation risk of electromagnetic voltage transformer

Abstract

The application discloses a kind of electromagnetic voltage transformer low-frequency oscillation risk identification method, device and equipment.The method comprises: obtaining the topological structure and electric power parameter of power system, according to the topological structure and electric power parameter of the power system, constructs electromagnetic voltage transformer low-frequency oscillation equivalent physical model;Based on the electromagnetic voltage transformer low-frequency oscillation equivalent physical model, low-frequency oscillation simulation is carried out to electromagnetic voltage transformer, and the primary current waveform signal of the electromagnetic voltage transformer is obtained;According to the maximum current of the primary current waveform signal and the frequency corresponding to the maximum current, it is judged whether the electromagnetic voltage transformer exists low-frequency oscillation risk, and the low-frequency oscillation risk identification result is obtained.The application can monitor the occurrence risk of electromagnetic voltage transformer low-frequency oscillation in real time accurately, effectively avoid electromagnetic voltage transformer ontology and fuse fault.

Description

Technical Field

[0001] This invention relates to the field of voltage transformer technology, and in particular to a method, apparatus and equipment for identifying low-frequency oscillation risks in electromagnetic voltage transformers. Background Technology

[0002] In medium-voltage distribution networks, due to the nonlinear characteristics of electromagnetic voltage transformers (PTs), external disturbances easily induce ferroresonance. As the scale of cable systems increases, the system's capacitance to ground increases significantly, making it difficult to achieve resonance with the system inductance, which is dominated by the PT. When a single-phase ground fault is cleared, the discharge of accumulated charge in the healthy phase's line capacitance creates nonlinear low-frequency oscillations, leading to frequent PT fuse blowouts and burnouts, significantly impacting the reliability of medium-voltage distribution network power supply.

[0003] The low-frequency oscillation of the PT is caused by a single-phase ground fault. When a single-phase ground fault occurs, a capacitive current flows through the fault point, and the voltage of the ungrounded phase rises to the line voltage. Its capacitance to ground is charged with a charge corresponding to the line voltage. Once the single-phase ground fault disappears, the current path is cut off, and the voltage of the ungrounded phase must instantly recover from the line voltage to the normal phase voltage level. However, at this time, the single-phase ground fault has been disconnected. The charge that the ungrounded phase has been charged to the line voltage during the grounding period can only enter the ground through the PT high-voltage winding and the originally grounded neutral point. During this transient process, a low-frequency saturation current with a high amplitude will flow through the PT high-voltage winding, which is the low-frequency oscillation.

[0004] Because single-phase grounding faults occur and dissipate frequently in medium-voltage distribution networks, PT (potential transformer) and fuse failures occur frequently. These failures are caused by improper coordination of system parameters; even replacing the PT and fuse cannot fundamentally eliminate the fault conditions, making it difficult to effectively prevent recurrence. Furthermore, actual grid operation shows that PT and fuse failures often occur repeatedly at the same location, significantly impacting the reliability of the distribution network. Currently, research on low-frequency oscillations in medium-voltage PTs is limited, and there is a lack of relevant methods and systems for identifying low-frequency oscillation risks, making it impossible to monitor the risk of low-frequency oscillations in real time and take timely preventative measures. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method, device and equipment for identifying the risk of low-frequency oscillation in electromagnetic voltage transformers, which can monitor the risk of low-frequency oscillation in electromagnetic voltage transformers in real time and effectively avoid failure of the electromagnetic voltage transformer body and fuse.

[0006] To address the aforementioned technical problems, in a first aspect, an embodiment of the present invention provides a method for identifying low-frequency oscillation risks in an electromagnetic voltage transformer, comprising:

[0007] Obtain the topology and power parameters of the power system, and construct an equivalent physical model of low-frequency oscillation of the electromagnetic voltage transformer based on the topology and power parameters of the power system.

[0008] Based on the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer, the electromagnetic voltage transformer is simulated for low-frequency oscillation to obtain the primary current waveform signal of the electromagnetic voltage transformer.

[0009] Based on the maximum current of the primary current waveform signal and the frequency corresponding to the maximum current, it is determined whether the electromagnetic voltage transformer has a risk of low-frequency oscillation, and the low-frequency oscillation risk identification result is obtained.

[0010] Furthermore, the method for identifying the low-frequency oscillation risk of the electromagnetic voltage transformer also includes:

[0011] When the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk, the low-frequency oscillation risk level of the electromagnetic voltage transformer is evaluated based on the maximum current and the frequency corresponding to the maximum current, and the low-frequency oscillation risk level evaluation result is obtained.

[0012] Furthermore, the method for identifying the low-frequency oscillation risk of the electromagnetic voltage transformer also includes:

[0013] When the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk, an alarm signal is sent.

[0014] Furthermore, the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer includes an equivalent source submodule, an excitation submodule, a capacitor submodule, an electromagnetic voltage transformer submodule, and a load submodule connected in sequence.

[0015] Furthermore, based on the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer, the low-frequency oscillation simulation of the electromagnetic voltage transformer is performed to obtain the primary current waveform signal of the electromagnetic voltage transformer, specifically as follows:

[0016] The operating parameters of the electromagnetic voltage transformer are input into the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer, so that the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer can simulate the low-frequency oscillation of the electromagnetic voltage transformer to obtain the primary current waveform signal.

[0017] Furthermore, the step of determining whether the electromagnetic voltage transformer has a low-frequency oscillation risk based on the maximum current of the primary current waveform signal and the frequency corresponding to the maximum current, and obtaining the low-frequency oscillation risk identification result, specifically involves:

[0018] Extract the maximum current and the frequency corresponding to the maximum current from the primary current waveform signal, and compare the maximum current with a preset current threshold and compare the frequency corresponding to the maximum current with a preset frequency threshold.

[0019] If the maximum current is greater than the preset current threshold and the frequency corresponding to the maximum current is less than the preset frequency threshold, then the electromagnetic voltage transformer is determined to have a risk of low-frequency oscillation; otherwise, the electromagnetic voltage transformer is determined not to have a risk of low-frequency oscillation.

[0020] Furthermore, the step of assessing the low-frequency oscillation risk level of the electromagnetic voltage transformer based on the maximum current and the frequency corresponding to the maximum current, and obtaining the low-frequency oscillation risk level assessment result, specifically involves:

[0021] Based on the first risk coefficient assessment model, the first risk coefficient of the electromagnetic voltage transformer is obtained according to the maximum current and the preset current threshold.

[0022] Based on the second risk coefficient assessment model, the second risk coefficient of the electromagnetic voltage transformer is obtained according to the frequency corresponding to the maximum current and the preset frequency threshold.

[0023] The first risk coefficient and the second risk coefficient are weighted and summed to obtain the comprehensive risk coefficient of the electromagnetic voltage transformer;

[0024] Based on a predefined risk coefficient range-risk level mapping relationship, the risk level corresponding to the risk coefficient range in which the comprehensive risk coefficient is located is taken as the low-frequency oscillation risk level of the electromagnetic voltage transformer.

[0025] Furthermore, the first risk coefficient assessment model is as follows:

[0026]

[0027] Among them, K I Let I be the first risk coefficient. max I0 is the maximum current, and I0 is the preset current threshold.

[0028] The second risk coefficient assessment model is as follows:

[0029]

[0030] Among them, K f f is the second risk coefficient, f is the frequency corresponding to the maximum current, and f0 is the preset frequency threshold.

[0031] The comprehensive risk coefficient is:

[0032] K = a × K I +b×K f ;

[0033] Wherein, K is the comprehensive risk coefficient, a is the weight of the first risk coefficient, b is the weight of the second risk coefficient, and a+b=1.

[0034] Secondly, an embodiment of the present invention provides a low-frequency oscillation risk identification device for an electromagnetic voltage transformer, comprising:

[0035] The equivalent physical model construction module is used to obtain the topology and power parameters of the power system, and construct an equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer based on the topology and power parameters of the power system.

[0036] The low-frequency oscillation simulation module is used to simulate the low-frequency oscillation of the electromagnetic voltage transformer based on the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer, and to obtain the primary current waveform signal of the electromagnetic voltage transformer.

[0037] The low-frequency oscillation risk identification module is used to determine whether the electromagnetic voltage transformer has a low-frequency oscillation risk based on the maximum current of the primary current waveform signal and the frequency corresponding to the maximum current, and to obtain the low-frequency oscillation risk identification result.

[0038] Thirdly, one embodiment of the present invention provides a low-frequency oscillation risk identification device for an electromagnetic voltage transformer, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. The memory is coupled to the processor, and when the processor executes the computer program, it implements the low-frequency oscillation risk identification method for an electromagnetic voltage transformer as described above.

[0039] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0040] By acquiring the topology and power parameters of the power system, an equivalent physical model of low-frequency oscillation of the electromagnetic voltage transformer is constructed. Based on this model, low-frequency oscillation simulation is performed on the electromagnetic voltage transformer to obtain its primary current waveform signal. The presence of low-frequency oscillation risk in the electromagnetic voltage transformer is determined based on the maximum current and its corresponding frequency, resulting in a low-frequency oscillation risk identification result. This allows for real-time and accurate monitoring of the risk of low-frequency oscillation in the electromagnetic voltage transformer, effectively preventing faults in the transformer itself and its fuses. Attached Figure Description

[0041] Figure 1This is a flowchart illustrating a method for identifying low-frequency oscillation risks in an electromagnetic voltage transformer according to the first embodiment of the present invention.

[0042] Figure 2 This is a schematic diagram of the equivalent physical model of the low-frequency oscillation of an electromagnetic voltage transformer as exemplified in the first embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the structure of the electromagnetic voltage transformer submodule exemplified in the first embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the saturation curve of an electromagnetic voltage transformer exemplified in the first embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of the saturation characteristic curve of an electromagnetic voltage transformer exemplified in the first embodiment of the present invention;

[0046] Figure 6 This is a schematic diagram illustrating the method of measuring capacitance using an external PT at the neutral point of a capacitor, as exemplified in the first embodiment of the present invention.

[0047] Figure 7 This is a schematic diagram of the primary current waveform signal of an electromagnetic voltage transformer exemplified in the first embodiment of the present invention;

[0048] Figure 8 This is a schematic diagram of the structure of a low-frequency oscillation risk identification device for an electromagnetic voltage transformer according to the second embodiment of the present invention. Detailed Implementation

[0049] The technical solutions of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0050] It should be noted that the step numbers in this document are only for the convenience of explaining the specific embodiments and are not intended to limit the order in which the steps are executed. The method provided in this embodiment can be executed by relevant terminal devices, and the following description uses a processor as the execution subject.

[0051] like Figure 1 As shown, the first embodiment provides a method for identifying low-frequency oscillation risks in electromagnetic voltage transformers, including steps S1 to S3:

[0052] S1. Obtain the topology and power parameters of the power system, and construct an equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer based on the topology and power parameters of the power system.

[0053] S2. Based on the equivalent physical model of low-frequency oscillation of electromagnetic voltage transformer, the low-frequency oscillation of electromagnetic voltage transformer is simulated to obtain the primary current waveform signal of electromagnetic voltage transformer.

[0054] S3. Based on the maximum current and the frequency corresponding to the maximum current of the primary current waveform signal, determine whether the electromagnetic voltage transformer has a risk of low-frequency oscillation and obtain the low-frequency oscillation risk identification result.

[0055] As an example, in step S1, the topology and power parameters of the power system are obtained according to the substation wiring diagram and power system parameters, and an equivalent physical model of low-frequency oscillation of the electromagnetic voltage transformer is constructed based on the topology and power parameters of the power system.

[0056] Among them, power parameters include the parameters of various components in the power system, such as the rated voltage of the voltage source and the resistance value of the resistor.

[0057] In step S2, when the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer is obtained, the electromagnetic voltage transformer is simulated for low-frequency oscillation based on the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer to obtain the primary current waveform signal of the electromagnetic voltage transformer.

[0058] In step S3, the maximum current and the frequency corresponding to the maximum current are extracted from the primary current waveform signal. Based on the maximum current and the frequency corresponding to the maximum current, it is determined whether the electromagnetic voltage transformer has a risk of low-frequency oscillation, and the low-frequency oscillation risk identification result is obtained.

[0059] This embodiment can monitor the risk of low-frequency oscillation in electromagnetic voltage transformers in real time and accurately, effectively avoiding failures in the electromagnetic voltage transformer body and fuses.

[0060] In a preferred embodiment, the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer includes an equivalent source submodule, an excitation submodule, a capacitor submodule, an electromagnetic voltage transformer submodule, and a load submodule connected in sequence.

[0061] As an example, the constructed equivalent physical model of low-frequency oscillation of an electromagnetic voltage transformer is as follows: Figure 2 As shown, the equivalent physical model of low-frequency oscillation of an electromagnetic voltage transformer includes an equivalent source submodule, an excitation submodule, a capacitor submodule, an electromagnetic voltage transformer submodule, and a load submodule connected in sequence.

[0062] For the electromagnetic voltage transformer submodule, its equivalent physical model is established based on the physical properties of the electromagnetic voltage transformer. The electromagnetic voltage transformer submodule is as follows: Figure 3As shown, electromagnetic voltage transformers that generate low-frequency oscillations are usually three-phase star-connected (YY connection), with their primary side connected to the three-phase busbar and their secondary side connected in an open delta configuration.

[0063] The electromagnetic voltage transformer submodule considers the saturation effect of the electromagnetic voltage transformer. This is simulated by inputting characteristic points of the saturation curve into the submodule; that is, the voltage and current data at different characteristic points are sufficient. The saturation curve of the electromagnetic voltage transformer is shown below. Figure 4 As shown, the voltage and current at point k are U and U, respectively. k and I k .

[0064] The characteristic points of the saturation curve are obtained through experiments on an electromagnetic voltage transformer. The experimental method is as follows: the end terminal of the primary winding of the electromagnetic voltage transformer is grounded, and all other windings are open-circuited. A voltage U is applied to the secondary winding, with a voltage waveform of an actual sine wave, and the corresponding excitation current I is measured. Measurement points must include voltage values ​​at at least 20%, 50%, 80%, 100%, and 120% of the rated voltage. By measuring multiple sets of points, the relationship curve between U and I is plotted, which is the saturation curve of the electromagnetic voltage transformer.

[0065] To ensure the correctness and validity of the feature points of the input saturation curve, an algorithm based on differentiated slope verification is proposed. This algorithm verifies each feature point according to the slope characteristics of different curve segments. If a point with an incorrect slope is found, it is automatically ignored. For example, based on... Figure 5 The saturation characteristic curve of the electromagnetic voltage transformer shown should show a gradually decreasing slope in segment 0a, i.e., K1 > K2. If the system detects K1 < K2, it will automatically ignore the point with a slope of K2.

[0066] For the capacitor submodule, the system-to-ground capacitance is measured using the external PT method at the capacitor neutral point. The capacitance measured by the capacitor current tester is converted into the actual system-to-ground capacitance. Then, based on the relationship model between phase-to-phase capacitance and phase-to-ground capacitance, the phase-to-phase capacitance is calculated, thereby obtaining the required parameters such as the phase-to-ground capacitance and phase-to-ground capacitance for the capacitor submodule.

[0067] like Figure 6 As shown, the capacitor neutral point external PT method involves connecting the neutral point of the capacitor (which can be supplemented by a reactive power compensation capacitor) to the primary side of a PT, and connecting the secondary side of the PT to a capacitance current meter. By injecting a signal from the secondary side of the PT into the capacitance current meter, the displayed value C of the capacitance current meter can be measured. x This value is the capacitor C. a C b C c The series capacitance with the total capacitance C of the line to ground. Figure 6In this diagram, PT is an external single-phase electromagnetic voltage transformer; X is a withstand voltage cable; DL is a circuit breaker; DS is a disconnecting switch; ES is a grounding switch; L is a current-limiting reactor; C a C b C c The capacitance of a capacitor bank forming a star connection; C 11 C 22 C 33 This refers to the three-phase ground capacitance of the line.

[0068] The actual capacitance to ground of the system is calculated as follows:

[0069] According to the displayed value C of the capacitance current tester x Capacitor bank capacitance C a C b C c To calculate the total capacitance C to ground and the capacitance current, the conversion formula is:

[0070]

[0071]

[0072] In equation (2), Uφ is the system phase voltage and ω is the angular frequency.

[0073] Assume the three-phase-to-ground capacitance C of the line 11 C 22 C 33 If they are all the same, then

[0074]

[0075] Interphase capacitance calculation:

[0076] Based on operational experience, the interphase capacitance is typically one-third of the capacitance to ground; therefore, the interphase capacitance C... 12 C 23 C 31 The solution can be obtained using the following formula:

[0077]

[0078] For the excitation submodule, the low-frequency oscillation of the electromagnetic voltage transformer is triggered by a single-phase ground fault. When a single-phase ground fault occurs, the voltage of the ungrounded phase rises to the line voltage. Once the single-phase ground fault disappears, the ungrounded phase must instantly return from the line voltage to the normal phase voltage level. This can only be achieved by discharging the charge through the PT high-voltage winding. To simulate this process, an excitation submodule is constructed to simulate a single-phase ground fault by using a switch. The occurrence and disappearance times of the single-phase ground fault are set to simulate the fault process.

[0079] Considering that different phase angles during a single-phase ground fault may lead to different current amplitudes and operating frequencies of low-frequency oscillation waveform signals, a closing angle traversal algorithm is proposed. When a single-phase ground fault occurs, the closing angle is traversed from 0° to 360° with an interval of 2°. Finally, the primary current amplitude of the electromagnetic voltage transformer with the highest current amplitude and its corresponding operating frequency are saved.

[0080] To reduce system workload and memory pressure, after the system completes two calculations, the amplitude I of the primary current of the electromagnetic voltage transformer obtained from the two calculations is... k The calculations are compared, and the results with higher current amplitudes are saved. This process is repeated until the system finally exhibits the most demanding operating conditions, yielding the maximum current I. max ,Right now:

[0081]

[0082] In equation (5), k = 1, 2, ..., 181.

[0083] For the equivalent source submodule, the equivalent source submodule is represented by an AC voltage source with system impedance, which is solved based on the short-circuit current.

[0084] For the load submodule, the load submodule is represented by input active power P and reactive power Q, i.e., P+jQ form.

[0085] This embodiment constructs an equivalent physical model of low-frequency oscillation in an electromagnetic voltage transformer, enabling subsequent direct simulation of low-frequency oscillations in the electromagnetic voltage transformer using this model. This allows for real-time and accurate monitoring of the risk of low-frequency oscillations in the electromagnetic voltage transformer, effectively preventing failures in the transformer body and fuses.

[0086] In a preferred embodiment, the step of simulating low-frequency oscillations of an electromagnetic voltage transformer based on a low-frequency oscillation equivalent physical model to obtain the primary current waveform signal of the electromagnetic voltage transformer specifically involves: inputting the operating parameters of the electromagnetic voltage transformer into the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer, so that the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer can simulate low-frequency oscillations of the electromagnetic voltage transformer to obtain the primary current waveform signal.

[0087] As an example, the operating parameters of the electromagnetic voltage transformer, such as saturation parameters, three-phase-to-ground capacitance parameters, phase-to-phase capacitance parameters, equivalent source parameters, and load parameters, are input into the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer. The saturation parameters, three-phase-to-ground capacitance parameters, and phase-to-phase capacitance parameters are obtained through the aforementioned experiments. The equivalent source parameters (including voltage value and equivalent impedance) and load parameters (including active power and reactive power) are obtained in real time by querying power system operating data. This allows the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer to simulate low-frequency oscillations, obtaining the primary current waveform signal of the electromagnetic voltage transformer. The primary current waveform signal of the electromagnetic voltage transformer is shown below. Figure 7 As shown.

[0088] This embodiment inputs the operating parameters of the electromagnetic voltage transformer into the equivalent physical model of the electromagnetic voltage transformer's low-frequency oscillation, so that the equivalent physical model of the electromagnetic voltage transformer can simulate the low-frequency oscillation of the electromagnetic voltage transformer. This enables real-time and accurate monitoring of the risk of low-frequency oscillation of the electromagnetic voltage transformer, effectively avoiding failures of the electromagnetic voltage transformer body and fuses.

[0089] In a preferred embodiment, the step of determining whether the electromagnetic voltage transformer has a low-frequency oscillation risk based on the maximum current and the frequency corresponding to the maximum current in the primary current waveform signal, and obtaining the low-frequency oscillation risk identification result, specifically involves: extracting the maximum current and the frequency corresponding to the maximum current from the primary current waveform signal, comparing the maximum current with a preset current threshold, and comparing the frequency corresponding to the maximum current with a preset frequency threshold; if the maximum current is greater than the preset current threshold and the frequency corresponding to the maximum current is less than the preset frequency threshold, then the electromagnetic voltage transformer is determined to have a low-frequency oscillation risk; otherwise, the electromagnetic voltage transformer is determined not to have a low-frequency oscillation risk.

[0090] As an example, the maximum current and the frequency corresponding to the maximum current are extracted from the primary current waveform signal, and the maximum current is compared with a preset current threshold, and the frequency corresponding to the maximum current is compared with a preset frequency threshold.

[0091] When the maximum current is greater than a preset current threshold and the frequency corresponding to the maximum current is less than a preset frequency threshold, the electromagnetic voltage transformer is determined to have a risk of low-frequency oscillation; when the maximum current is not greater than a preset current threshold or the frequency corresponding to the maximum current is not less than a preset frequency threshold, the electromagnetic voltage transformer is determined not to have a risk of low-frequency oscillation.

[0092] In a preferred embodiment, the method for identifying the low-frequency oscillation risk of an electromagnetic voltage transformer further includes step S4:

[0093] S4. When the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk, the low-frequency oscillation risk level of the electromagnetic voltage transformer is evaluated based on the maximum current and the frequency corresponding to the maximum current, and the low-frequency oscillation risk level assessment result is obtained.

[0094] This embodiment assesses the low-frequency oscillation risk level of an electromagnetic voltage transformer based on the maximum current and the frequency corresponding to the maximum current when the transformer poses a low-frequency oscillation risk. This allows users to intuitively determine the impact of the electromagnetic voltage transformer on the reliability of medium-voltage power distribution networks based on the low-frequency oscillation risk level, and to take timely preventive measures to effectively avoid failures of the electromagnetic voltage transformer itself and its fuses.

[0095] In a preferred embodiment, the step of assessing the low-frequency oscillation risk level of the electromagnetic voltage transformer based on the maximum current and the frequency corresponding to the maximum current, and obtaining the low-frequency oscillation risk level assessment result, specifically involves: obtaining a first risk coefficient of the electromagnetic voltage transformer based on a first risk coefficient assessment model, according to the maximum current and a preset current threshold; obtaining a second risk coefficient of the electromagnetic voltage transformer based on a second risk coefficient assessment model, according to the frequency corresponding to the maximum current and a preset frequency threshold; weighted summing of the first and second risk coefficients to obtain a comprehensive risk coefficient of the electromagnetic voltage transformer; and, according to a predefined risk coefficient interval-risk level mapping relationship, using the risk level corresponding to the risk coefficient interval in which the comprehensive risk coefficient is located as the low-frequency oscillation risk level of the electromagnetic voltage transformer.

[0096] In a preferred embodiment, the first risk coefficient assessment model is:

[0097]

[0098] Among them, K I As the first risk factor, I max I is the maximum current, and I0 is the preset current threshold.

[0099] The second risk coefficient assessment model is:

[0100]

[0101] Among them, K f The second risk coefficient is f, where f is the frequency corresponding to the maximum current, and f0 is the preset frequency threshold; the comprehensive risk coefficient is:

[0102] K = a × K I +b×K f (8);

[0103] Where K is the comprehensive risk coefficient, a is the weight of the first risk coefficient, b is the weight of the second risk coefficient, and a+b=1.

[0104] As an example, under normal circumstances, the current flowing through an electromagnetic voltage transformer is approximately 1-5 mA at a frequency of 50 Hz. When the electromagnetic voltage transformer oscillates at a low frequency, the current increases and the frequency decreases.

[0105] Assume the preset current threshold I0 is 50mA; the preset frequency threshold f0 is 30Hz; the weight a of the first risk coefficient is 0.6, and the weight b of the second risk coefficient is 0.4.

[0106] Based on the first risk coefficient assessment model Based on the maximum current I max The first risk factor of the electromagnetic voltage transformer is obtained by using the preset current threshold I0.

[0107] Based on the second risk coefficient assessment model The second risk factor of the electromagnetic voltage transformer is obtained based on the frequency f corresponding to the maximum current and the preset frequency threshold f0.

[0108] For the first risk coefficient K I Second risk coefficient K f After weighted summation, the comprehensive risk coefficient K for the electromagnetic voltage transformer is obtained as K = 0.6 × K. I +0.4×K f .

[0109] Based on operational experience, I max ∈(50mA, 1000mA), then K I ∈(0,1); f∈(1Hz,30Hz), then K f ∈(0,1). According to K I and K f Given the range of K, we know that K∈(0,1).

[0110] Assume the predefined risk coefficient interval-risk level mapping relationship is {risk coefficient interval = (0, 0.4), risk level λ = low risk level}, {risk coefficient interval = [0.4, 0.8), risk level λ = medium risk level}, {risk coefficient interval = [0.8, 1], risk level λ = high risk level}.

[0111] Based on the predefined risk coefficient interval-risk level mapping relationship {risk coefficient interval = (0, 0.4), risk level λ = low risk level}, {risk coefficient interval = [0.4, 0.8), risk level λ = medium risk level}, and {risk coefficient interval = [0.8, 1], risk level λ = high risk level}, the risk level corresponding to the risk coefficient interval where the comprehensive risk coefficient K is located is taken as the low-frequency oscillation risk level of the electromagnetic voltage transformer, that is:

[0112] When the comprehensive risk coefficient K∈(0,0.4), the low-frequency oscillation risk level λ of the electromagnetic voltage transformer is determined to be low risk level.

[0113] When the comprehensive risk coefficient K∈[0.4, 0.8), the low-frequency oscillation risk level λ of the electromagnetic voltage transformer is determined to be medium risk level;

[0114] When the comprehensive risk coefficient K∈[0.8,1], the low-frequency oscillation risk level λ of the electromagnetic voltage transformer is determined to be high risk level.

[0115] In a preferred embodiment, the method for identifying the low-frequency oscillation risk of an electromagnetic voltage transformer further includes step S5:

[0116] S5. When the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk, an alarm signal is sent.

[0117] As an example, when there is a risk of low-frequency oscillation in an electromagnetic voltage transformer, and the risk level λ of the low-frequency oscillation of the electromagnetic voltage transformer is assessed, based on the operability and processing time of different handling measures, an automatic alarm is issued and differentiated handling measures are proposed according to different low-frequency oscillation risk levels λ, providing feasible suggestions to avoid the occurrence of low-frequency oscillation.

[0118] For example, when the low-frequency oscillation risk level λ of the electromagnetic voltage transformer is determined to be low risk, the system will issue a real-time, automatic warning stating, "Under the current operating mode and system parameters, the electromagnetic voltage transformer has a low-frequency oscillation risk, and the risk level is low. It is recommended to take measures such as installing harmonic suppression devices and low-frequency oscillation suppression devices." When the low-frequency oscillation risk level λ of the electromagnetic voltage transformer is determined to be medium risk, the system will issue a real-time, automatic warning stating, "Under the current operating mode and system parameters, the electromagnetic voltage transformer has a low-frequency oscillation risk, and the risk level is medium risk. It is recommended to take temporary measures such as connecting a single-phase PT in series at the neutral point of the electromagnetic voltage transformer." When the low-frequency oscillation risk level λ of the electromagnetic voltage transformer is high, the system will issue a real-time, automatic warning stating that "under the current operating mode and system parameters, the electromagnetic voltage transformer has a low-frequency oscillation risk, with a risk level of high. It is recommended to take temporary measures such as changing the operating mode and reducing the system capacitance." When the low-frequency oscillation risk level λ of the electromagnetic voltage transformer is determined to be low, and the number of low-frequency oscillations that have occurred at this location is t > 1, the system will issue a real-time, automatic warning stating that "under the current operating mode and system parameters, the electromagnetic voltage transformer has a low-frequency oscillation risk, with a risk level of high. It is recommended to take temporary measures such as replacing it with a high-capacity fuse."

[0119] This embodiment sends an alarm signal when the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk. This enables users to take corresponding preventive measures in a timely manner in response to the alarm signal, effectively avoiding failures of the electromagnetic voltage transformer body and fuses.

[0120] The method for identifying low-frequency oscillation risks in electromagnetic voltage transformers provided in the first embodiment can not only automatically identify the risks of low-frequency oscillations in PTs, but also determine the risk level and automatically provide differentiated handling suggestions based on the risk level. This provides scientific reference and technical support for power grid operation and maintenance, and has the following advantages:

[0121] (1) Accuracy: The low-frequency oscillation risk identification method for electromagnetic voltage transformers provided in the first embodiment takes into account the saturation curve of electromagnetic voltage transformers, the randomness of closing angle, the difference of system-to-ground capacitance, etc., and proposes corresponding solutions, making the identification results more accurate and reliable.

[0122] (2) Real-time performance: The low-frequency oscillation risk identification method for electromagnetic voltage transformers provided in the first embodiment can simulate the changes in system operating parameters in real time and give the simulation results, which has strong timeliness.

[0123] (3) Safety: When applying the low-frequency oscillation risk identification method for electromagnetic voltage transformers provided in the first embodiment, there is no direct connection with the primary side of the main equipment of the power grid, which effectively avoids the impact of the method execution system on the operation of the power grid;

[0124] (4) Prevention in advance: The method for identifying the risk of low-frequency oscillation of electromagnetic voltage transformer provided in the first embodiment can determine the risk and risk level of low-frequency oscillation in advance, providing sufficient time for power grid operation and maintenance personnel to handle the situation, and achieving proactive prevention before the fault occurs.

[0125] Based on the same inventive concept as the first embodiment, the second embodiment provides as follows: Figure 8 The device for identifying low-frequency oscillation risks in an electromagnetic voltage transformer includes: an equivalent physical model construction module 21, used to acquire the topology and power parameters of a power system, and construct an equivalent physical model of low-frequency oscillation in the electromagnetic voltage transformer based on the topology and power parameters of the power system; a low-frequency oscillation simulation module 22, used to simulate low-frequency oscillations in the electromagnetic voltage transformer based on the equivalent physical model of low-frequency oscillations in the electromagnetic voltage transformer, and obtain the primary current waveform signal of the electromagnetic voltage transformer; and a low-frequency oscillation risk identification module 23, used to determine whether the electromagnetic voltage transformer has a low-frequency oscillation risk based on the maximum current and the frequency corresponding to the maximum current of the primary current waveform signal, and obtain the low-frequency oscillation risk identification result.

[0126] In a preferred embodiment, the electromagnetic voltage transformer low-frequency oscillation risk identification device further includes: a low-frequency oscillation risk level assessment module, used to assess the low-frequency oscillation risk level of the electromagnetic voltage transformer based on the maximum current and the frequency corresponding to the maximum current when the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk, and obtain the low-frequency oscillation risk level assessment result.

[0127] In a preferred embodiment, the electromagnetic voltage transformer low-frequency oscillation risk identification device further includes: a low-frequency oscillation risk alarm module, used to send an alarm signal when the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk.

[0128] In a preferred embodiment, the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer includes an equivalent source submodule, an excitation submodule, a capacitor submodule, an electromagnetic voltage transformer submodule, and a load submodule connected in sequence.

[0129] In a preferred embodiment, the low-frequency oscillation simulation module 22 is specifically used to input the operating parameters of the electromagnetic voltage transformer into the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer, so that the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer performs low-frequency oscillation simulation on the electromagnetic voltage transformer to obtain a primary current waveform signal.

[0130] In a preferred embodiment, the low-frequency oscillation risk identification module 23 is specifically used to: extract the maximum current and the frequency corresponding to the maximum current from the primary current waveform signal, compare the maximum current with a preset current threshold, and compare the frequency corresponding to the maximum current with a preset frequency threshold; if the maximum current is greater than the preset current threshold and the frequency corresponding to the maximum current is less than the preset frequency threshold, then it is determined that the electromagnetic voltage transformer has a low-frequency oscillation risk; otherwise, it is determined that the electromagnetic voltage transformer does not have a low-frequency oscillation risk.

[0131] In a preferred embodiment, the low-frequency oscillation risk level assessment module is specifically used for: obtaining a first risk coefficient of the electromagnetic voltage transformer based on a first risk coefficient assessment model, according to the maximum current and a preset current threshold; obtaining a second risk coefficient of the electromagnetic voltage transformer based on a second risk coefficient assessment model, according to the frequency corresponding to the maximum current and a preset frequency threshold; weighted summing of the first and second risk coefficients to obtain a comprehensive risk coefficient of the electromagnetic voltage transformer; and, according to a predefined risk coefficient interval-risk level mapping relationship, using the risk level corresponding to the risk coefficient interval in which the comprehensive risk coefficient is located as the low-frequency oscillation risk level of the electromagnetic voltage transformer.

[0132] In a preferred embodiment, the first risk coefficient assessment model is:

[0133]

[0134] Among them, K I As the first risk factor, I max I is the maximum current, and I0 is the preset current threshold.

[0135] The second risk coefficient assessment model is:

[0136]

[0137] Among them, K f The second risk coefficient is f, where f is the frequency corresponding to the maximum current, and f0 is the preset frequency threshold.

[0138] The overall risk coefficient is:

[0139] K = a × K I +b×K f (11);

[0140] Where K is the comprehensive risk coefficient, a is the weight of the first risk coefficient, b is the weight of the second risk coefficient, and a+b=1.

[0141] Based on the same inventive concept as the first embodiment, the third embodiment provides a low-frequency oscillation risk identification device for electromagnetic voltage transformers, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. The memory is coupled to the processor, and when the processor executes the computer program, it implements the low-frequency oscillation risk identification method for electromagnetic voltage transformers as described in the first embodiment, and can achieve the same beneficial effects.

[0142] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0143] By acquiring the topology and power parameters of the power system, an equivalent physical model of low-frequency oscillation of the electromagnetic voltage transformer is constructed. Based on this model, low-frequency oscillation simulation is performed on the electromagnetic voltage transformer to obtain its primary current waveform signal. The presence of low-frequency oscillation risk in the electromagnetic voltage transformer is determined based on the maximum current and its corresponding frequency, resulting in a low-frequency oscillation risk identification result. This allows for real-time and accurate monitoring of the risk of low-frequency oscillation in the electromagnetic voltage transformer, effectively preventing faults in the transformer itself and its fuses.

[0144] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0145] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes described in the above embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

Claims

1. A method for identifying low-frequency oscillation risk in electromagnetic voltage transformers, characterized in that, include: Obtain the topology and power parameters of the power system, and construct an equivalent physical model of low-frequency oscillation of the electromagnetic voltage transformer based on the topology and power parameters of the power system. Based on the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer, the electromagnetic voltage transformer is simulated for low-frequency oscillation to obtain the primary current waveform signal of the electromagnetic voltage transformer. Based on the maximum current of the primary current waveform signal and the frequency corresponding to the maximum current, determine whether the electromagnetic voltage transformer has a risk of low-frequency oscillation, and obtain the low-frequency oscillation risk identification result. Specifically, determining whether the electromagnetic voltage transformer has a low-frequency oscillation risk based on the maximum current of the primary current waveform signal and the frequency corresponding to the maximum current, and obtaining the low-frequency oscillation risk identification result, involves the following steps: Extract the maximum current and the frequency corresponding to the maximum current from the primary current waveform signal, and compare the maximum current with a preset current threshold and compare the frequency corresponding to the maximum current with a preset frequency threshold. If the maximum current is greater than the preset current threshold and the frequency corresponding to the maximum current is less than the preset frequency threshold, then the electromagnetic voltage transformer is determined to have a risk of low-frequency oscillation; otherwise, the electromagnetic voltage transformer is determined not to have a risk of low-frequency oscillation. When the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk, the low-frequency oscillation risk level of the electromagnetic voltage transformer is evaluated based on the maximum current and the frequency corresponding to the maximum current, and the low-frequency oscillation risk level evaluation result is obtained. Specifically, the step of assessing the low-frequency oscillation risk level of the electromagnetic voltage transformer based on the maximum current and the frequency corresponding to the maximum current, and obtaining the low-frequency oscillation risk level assessment result, is as follows: Based on the first risk coefficient assessment model, the first risk coefficient of the electromagnetic voltage transformer is obtained according to the maximum current and the preset current threshold. Based on the second risk coefficient assessment model, the second risk coefficient of the electromagnetic voltage transformer is obtained according to the frequency corresponding to the maximum current and the preset frequency threshold. The first risk coefficient and the second risk coefficient are weighted and summed to obtain the comprehensive risk coefficient of the electromagnetic voltage transformer; Based on a predefined risk coefficient range-risk level mapping relationship, the risk level corresponding to the risk coefficient range in which the comprehensive risk coefficient is located is taken as the low-frequency oscillation risk level of the electromagnetic voltage transformer.

2. The method for identifying low-frequency oscillation risks in electromagnetic voltage transformers as described in claim 1, characterized in that, Also includes: When the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk, an alarm signal is sent.

3. The method for identifying low-frequency oscillation risks in electromagnetic voltage transformers as described in claim 1, characterized in that, The equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer includes an equivalent source submodule, an excitation submodule, a capacitor submodule, an electromagnetic voltage transformer submodule, and a load submodule connected in sequence.

4. The method for identifying low-frequency oscillation risks in electromagnetic voltage transformers as described in claim 1, characterized in that, Based on the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer, a low-frequency oscillation simulation of the electromagnetic voltage transformer is performed to obtain the primary current waveform signal of the electromagnetic voltage transformer, specifically: The operating parameters of the electromagnetic voltage transformer are input into the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer, so that the low-frequency oscillation equivalent physical model of the electromagnetic voltage transformer can simulate the low-frequency oscillation of the electromagnetic voltage transformer to obtain the primary current waveform signal.

5. The method for identifying low-frequency oscillation risks in electromagnetic voltage transformers as described in claim 1, characterized in that, The first risk coefficient assessment model is: ； in, This is the first risk coefficient. The maximum current, The preset current threshold; The second risk coefficient assessment model is as follows: ； in, This is the second risk coefficient. The frequency corresponding to the maximum current. The preset frequency threshold; The comprehensive risk coefficient is: ； Wherein, K is the comprehensive risk coefficient, a is the weight of the first risk coefficient, b is the weight of the second risk coefficient, and a+b=1.

6. A low-frequency oscillation risk identification device for an electromagnetic voltage transformer, characterized in that, include: The equivalent physical model construction module is used to obtain the topology and power parameters of the power system, and construct an equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer based on the topology and power parameters of the power system. The low-frequency oscillation simulation module is used to simulate the low-frequency oscillation of the electromagnetic voltage transformer based on the equivalent physical model of the low-frequency oscillation of the electromagnetic voltage transformer, and to obtain the primary current waveform signal of the electromagnetic voltage transformer. The low-frequency oscillation risk identification module is used to determine whether the electromagnetic voltage transformer has a low-frequency oscillation risk based on the maximum current of the primary current waveform signal and the frequency corresponding to the maximum current, and to obtain the low-frequency oscillation risk identification result. Specifically, determining whether the electromagnetic voltage transformer has a low-frequency oscillation risk based on the maximum current of the primary current waveform signal and the frequency corresponding to the maximum current, and obtaining the low-frequency oscillation risk identification result, involves the following steps: Extract the maximum current and the frequency corresponding to the maximum current from the primary current waveform signal, and compare the maximum current with a preset current threshold and compare the frequency corresponding to the maximum current with a preset frequency threshold. If the maximum current is greater than the preset current threshold and the frequency corresponding to the maximum current is less than the preset frequency threshold, then the electromagnetic voltage transformer is determined to have a risk of low-frequency oscillation; otherwise, the electromagnetic voltage transformer is determined not to have a risk of low-frequency oscillation. When the low-frequency oscillation risk identification result indicates that the electromagnetic voltage transformer has a low-frequency oscillation risk, the low-frequency oscillation risk level of the electromagnetic voltage transformer is evaluated based on the maximum current and the frequency corresponding to the maximum current, and the low-frequency oscillation risk level evaluation result is obtained. Specifically, the step of assessing the low-frequency oscillation risk level of the electromagnetic voltage transformer based on the maximum current and the frequency corresponding to the maximum current, and obtaining the low-frequency oscillation risk level assessment result, is as follows: Based on the first risk coefficient assessment model, the first risk coefficient of the electromagnetic voltage transformer is obtained according to the maximum current and the preset current threshold. Based on the second risk coefficient assessment model, the second risk coefficient of the electromagnetic voltage transformer is obtained according to the frequency corresponding to the maximum current and the preset frequency threshold. The first risk coefficient and the second risk coefficient are weighted and summed to obtain the comprehensive risk coefficient of the electromagnetic voltage transformer; Based on a predefined risk coefficient range-risk level mapping relationship, the risk level corresponding to the risk coefficient range in which the comprehensive risk coefficient is located is taken as the low-frequency oscillation risk level of the electromagnetic voltage transformer.

7. A low-frequency oscillation risk identification device for electromagnetic voltage transformers, characterized in that, The method includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the memory being coupled to the processor, and the processor implementing the method for identifying low-frequency oscillation risks of electromagnetic voltage transformers as described in any one of claims 1 to 5 when executing the computer program.

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