Substation lightning arrester bus voltage phase detection point selection method based on double probes

Abstract

The present application relates to power system equipment online monitoring technology, specifically relates to a substation lightning arrester bus voltage phase detection point selection method based on double probes, through the calculation of a simple model, the relationship expression of the voltage of a space three-phase live body and the ground electric field intensity component is derived, and the detection point selection method is obtained; three typical lightning arrester arrangements of an ultra-high voltage substation are modeled; the error between the phase of the z-axis component of the electric field intensity of the detection point and the phase of the bus voltage is obtained through simulation, and the positions of the double detection points of the lightning arrester under different operating conditions are determined; according to the measurement results of the double electric field probes, the phase sequence of the three-phase voltage is analyzed, and according to the comparison between the phase angle difference of the double detection points and 120°, the voltage correction phase angle δ is obtained, and the three-phase bus voltage phase is back calculated; according to the lightning arrester full current and the voltage phase angle, the resistive current is calculated. The method is suitable for quickly finding the measurement position with the minimum error in the substation with a complex working environment, and improves the measurement accuracy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of on-line monitoring of power system equipment, and particularly relates to a substation lightning arrester bus voltage phase detection point selection method based on double probes. BACKGROUND

[0002] The good operation state of the lightning arrester is crucial for the safe operation of the substation equipment, can effectively cut off the operating overvoltage and lightning overvoltage on the bus, and protects important power grid equipment such as transformers. The lightning arrester is generally connected to the high-voltage bus, and when the voltage on the bus is higher than a certain threshold, the resistance value of the nonlinear resistor in the lightning arrester will decrease, so that the charge on the bus flows into the ground through the lightning arrester, protecting the safe operation of the equipment.

[0003] The zinc oxide lightning arrester becomes an important equipment of the substation due to its good nonlinear characteristics, large current-carrying capacity, and ability to withstand high overvoltage. The main method to evaluate the operation state of the lightning arrester is to detect the leakage current below the lightning arrester, but ultimately to obtain the resistive current representing the aging state of the lightning arrester, the phase angle between the lightning arrester bus voltage and the leakage current needs to be known. Measuring the voltage phase angle with an electric field probe is a safe choice suitable for the field, but for the complex operation of the substation, considering the influence of the surrounding charged bodies such as the bus, the voltage transformer, and the grading ring, the influence of each charged body on the electric field of the detection point position, and the selection strategy of the detection point according to the different position environments all need to be studied, so that the electric field phase can be efficiently measured with the probe. SUMMARY

[0004] In view of the problems in the background art, the application provides a substation lightning arrester bus voltage phase detection point selection method based on double probes.

[0005] To solve the above technical problems, the application adopts the following technical scheme: the substation lightning arrester bus voltage phase detection point selection method based on double probes, a simple model of the z-axis component of the electric field and the conductor charge is established, the relationship expression between the voltage of the space three-phase charged body and the ground electric field intensity component is derived through the calculation of the simple model, and the method for selecting the detection point is obtained; three typical lightning arrester arrangement situations of the ultra-high voltage substation are modeled, including a single lightning arrester, a single lightning arrester with a bus, and double lightning arresters with a bus; the error between the z-axis component phase of the electric field intensity of the detection point and the bus voltage phase is obtained through simulation, and the positions of the double detection points of the lightning arrester under different operation conditions are determined; the three-phase voltage phase sequence is analyzed according to the measurement results of the double electric field probes, the voltage correction phase angle δ is obtained by comparing the phase angle difference of the double detection points with 120°, and the three-phase bus voltage phase is inversely deduced; the resistive current representing the aging state of the lightning arrester is obtained according to the total current of the lightning arrester and the voltage phase angle; including the following steps:

[0006] Step 1: Based on the model of three-phase parallel conductors and three-phase metal spheres, obtain the phase law of the electric field around the three-phase charged body, and find the detection position to measure the phase of the three-phase voltage; establish the relationship between the z-axis component of the electric field and the conductor charge, and use the potential coefficient of the simple model to analyze the relationship between the electric field components and the potential.

[0007] Step 2: Based on the parameters of the surge arrester, busbar, and voltage transformer of the substation, build a model of the UHV substation. The phase deviation and amplitude of each flange in the surge arrester model are simulated and calculated using Simulink and considered in the finite element simulation. At the same time, the influence of the voltage transformer and equalizing ring on the phase is also considered.

[0008] Step 3: Determine the location of the dual detection points for the following surge arrester arrangements: single surge arrester without busbar, single surge arrester with busbar, and two surge arresters with busbar.

[0009] Step 4: Based on the location of the dual detection points obtained in Step 3, find a location with less interference on site for measurement. At the same time, take the voltage signal on the PT for comparison to determine the correctness of the model simulation results and the location selection. Use the phase difference of the waveforms of the dual detection points to obtain the phase sequence of the bus voltage. Consider the rule that the electric field component measured by the electric field probe below the B-phase arrester is 180° out of phase with the bus voltage, and that the phase of the interphase detection point is consistent with the phase direction of the measured bus voltage, compare it with 120° to obtain the correction angle.

[0010] Step 5: Based on the phase angle difference of the corrected current and voltage waveforms, the resistive current is measured.

[0011] In the above-mentioned method for selecting the bus voltage phase detection point of a substation surge arrester based on dual probes, the specific implementation of step 1 includes:

[0012] Using Gauss's law, we obtain the expression for the relationship between electric field and charge:

[0013]

[0014] Substitute the relationship between charge and potential:

[0015]

[0016] The electric field expression at a point in space when a three-phase voltage is applied to a three-phase conductor is obtained:

[0017]

[0018] From the above formula, we can obtain that when the detection point is selected below phase B, since r1 = r3, r1′ = r3′, cosθ1 = cosθ3, cosθ1′ = cosθ3′, then F1 = F3, and β 21 =β 23,β 11 =β 33 Combining the first and third terms of the above equation, the remaining expression for the B-phase potential leads to the conclusion that: when measuring the B-phase voltage below the B-phase arrester; when measuring the phase of the B-phase bus below the B-phase arrester, since the direction of the bus voltage is opposite to the z-component of the electric field strength, the electric field component measured by the probe differs from the bus voltage by 180°; when measuring the C-phase voltage between phases A and B, and when measuring the A-phase voltage between phases B and C, there are phase deviations.

[0019] In the above-mentioned method for selecting the phase detection point of the bus voltage of the substation surge arrester based on dual probes, the specific implementation of step 2 includes:

[0020] Step 2.1: Based on the distribution of surge arresters, voltage transformers, and busbars, build finite element models that conform to the actual size, including models of surge arresters with a single set of surge arresters without busbars, with a single set of surge arresters with busbars, and with two sets of surge arresters with busbars.

[0021] Step 2.2: Obtain the magnitude and phase angle of the voltage of each flange of the surge arrester through the simulation model of the RC network. Through calculation, apply the voltage excitation to each flange. At the same time, use electrostatic field simulation, select two times t=0 and t=0.005s for simulation, and obtain the phase information of the electric field at any point in space.

[0022] In the above-mentioned method for selecting the phase detection point of the bus voltage of the substation surge arrester based on dual probes, the specific implementation of step 3 includes:

[0023] Step 3.1: Based on the model built in Step 2.1, under the actual substation size model, when the phase error between the z-component waveform of the electric field intensity between phase A and phase B surge arresters and the phase error between the bus voltage of phase C surge arrester are less than 1°, the voltage of phase C surge arrester is measured between phase A and phase B surge arresters, and there is no ±180° phase difference; when the phase error between the z-component waveform of the electric field intensity between phase B and phase C surge arresters and the phase error between the bus voltage of phase A surge arrester are less than 1°, the voltage of phase A surge arrester is measured between phase B and phase C surge arresters, and there is no ±180° phase difference; the phase of the bus voltage of phase B surge arrester measured below phase B surge arrester needs to be shifted by 180°.

[0024] Step 3.2: From Step 3.1, we can conclude that: For a single surge arrester without a busbar, the two detection points are selected respectively between the A-phase and B-phase surge arresters, and below the B-phase surge arrester; For a single surge arrester with a busbar, the two detection points are selected respectively at the detection point corresponding to the busbar phase closest to the arrester, and below the B-phase surge arrester; For two surge arresters with a busbar, the two detection points are selected respectively below the B-phase surge arrester that is most closely affected by the A-phase and B-phase live parts, and at the detection point where the live part has the greatest impact on the detection position.

[0025] In the above method for selecting the phase detection point of the bus voltage of the substation surge arrester based on dual probes, the specific implementation of step 4 includes:

[0026] First, the phase of the probe measurement result and the voltage signal acquired on the PT are compared. If the error is less than 1°, the dual probe points are arranged according to the position obtained in step 3. By acquiring the dual probe simulated voltage waveform for 1 second, the time difference Δt between the two waveforms is obtained. Then, based on the relationship between time and phase angle, the phase angle difference Δφ is obtained.

[0027]

[0028] If the probe is used to measure the voltage of phase B, the phase needs to be shifted by 180°.

[0029] Calculate the correction angle δ based on the phase angle difference Δφ of the dual electric field probe waveforms:

[0030]

[0031] If Δφ>120°, then the waveform with the leading phase will lag by δ, and the waveform with the lagging phase will lead by δ. Similarly, if Δφ<120°, then the waveform with the leading phase will lead by δ again, and the waveform with the lagging phase will lag by δ.

[0032] 6. The method for selecting the bus voltage phase detection point of a substation surge arrester based on dual probes according to claim 5, characterized in that: the specific implementation of step 5 includes:

[0033] Step 5.1: Based on the conclusions obtained in Step 3.2, find the detection point with the least interference;

[0034] Step 5.2: Compare the measured z-component phase of the electric field intensity with the waveform acquired by the PT to obtain the error;

[0035] Step 5.3: If the error is greater than 1°, return to step 5.1; if the error is less than 1°, proceed to step 5.4.

[0036] Step 5.4: Determine the probe placement location, and use the time difference to deduce the phase angle difference Δφ to determine the phase sequence;

[0037] Step 5.5: Obtain the correction angle δ using the phase angle difference formula, and modify the voltage waveform accordingly;

[0038] Step 5.6: Input the voltage waveform and the current waveform collected by the surge arrester into the equipment, analyze the phase angle difference between the voltage and current, and obtain the resistive current value.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] (1) The present invention proposes a method of electric field measurement using dual electric field probes, which can not only obtain the phase sequence of three-phase voltage, but also balance measurement errors and avoid measurement randomness.

[0041] (2) This invention, through simulation and analysis of three typical surge arrester spatial arrangement methods, can find the optimal placement location for the electric field probe in complex substation environments. By calculating the phase angle difference between the output waveforms of the two probes using the measurement results of the dual probes, the probe output waveform is corrected, providing a more reliable representation of the bus voltage phase. The dual electric field probe placement method proposed in this invention provides a site selection strategy for probe placement, quickly finding the location with the smallest error, and has significant reference value for practical operation.

[0042] (3) The present invention can obtain reliable bus voltage phase information without direct contact with the live equipment in the substation, making it suitable for actual substation measurement. Attached Figure Description

[0043] Figure 1 This is a model diagram of a single-group three-phase surge arrester according to an embodiment of the present invention;

[0044] Figure 2 This is a phase angle deviation curve diagram at different positions according to an embodiment of the present invention;

[0045] Figure 3 This is a model diagram of a single three-phase surge arrester with busbar according to an embodiment of the present invention;

[0046] Figure 4 This is a model diagram of a dual-group three-phase surge arrester with busbar according to an embodiment of the present invention;

[0047] Figure 5 This is a flowchart of the actual on-site operation of an embodiment of the present invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0049] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0050] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0051] Deploying dual-field probes in UHV substations can effectively reduce the randomness and errors of single-probe measurements, obtaining a surge arrester bus phase that meets practical requirements. Simultaneously, dual-field probes can be used to determine the phase sequence of three-phase voltages. When spatially deploying dual-field probes, different detection points must be determined based on different bus locations and the spatial distribution of surge arresters to minimize errors and meet practical application requirements.

[0052] This embodiment derives the relationship between the voltage of a three-phase charged body in space and the components of the ground electric field intensity through calculations on a simple model, thus obtaining the basic rules for selecting detection points. It models three typical surge arrester arrangements in UHV substations: single-group surge arresters, single-group surge arresters with a busbar, and double-group surge arresters with a busbar. Simulations are used to obtain the error between the z-axis phase of the electric field intensity at the detection point and the phase of the busbar voltage, determining the optimal location of the dual detection points for the surge arresters under different operating conditions. The three-phase voltage phase sequence is analyzed based on the measurement results from the dual electric field probes. Simultaneously, the voltage correction phase angle δ is obtained by comparing the phase angle difference between the dual detection points with 120°, and the three-phase busbar voltage phase is deduced. Based on the total current of the surge arrester and the voltage phase angle, the resistive current characterizing the aging state of the surge arrester is calculated. This method uses dual detection points to obtain the busbar voltage phase, enabling the selection of different detection points according to different surge arrester arrangements. It is suitable for quickly finding the location with the minimum error in substations with complex operating environments, improving measurement accuracy.

[0053] To achieve optimal dual-probe positioning, this embodiment adopts the following technical solution:

[0054] S1. Based on the model of three-phase parallel busbars, the phase law of the surrounding electric field is derived, and the method for measuring the phase of the three-phase busbar voltage is analyzed. First, the expression for the z-axis component of the electric field intensity and the busbar charge is established. At the same time, by calculating the potential coefficient of the busbar, the magnitude relationship and influencing factors of the busbar electrostatic induction coefficient are obtained, and finally the relationship between the electric field components and the potential is analyzed.

[0055] Theoretical analysis shows that, in a three-phase parallel busbar model, the phase of phase B busbar can be measured below it. However, since the direction of the busbar voltage is opposite to the z-component of the electric field intensity, the phase of the electric field component waveform measured by the probe needs to be ±180° to obtain the phase of the phase B busbar voltage. Furthermore, placing an electric field probe between phase A and phase B conductors cannot completely measure the phase of phase C voltage; the specific error depends on the conductor size and the location of the detection point. Similarly, measuring the phase of phase A voltage between phase B and phase C surge arresters also presents errors, which are related to the conductor size and the location of the detection point. The specific steps are as follows:

[0056] The relationship between the z-component of the electric field intensity and the bus potential is derived, and the measurement law of the detection points around the three-phase bus is analyzed.

[0057] First, using Gauss's law, we obtain the expression for the relationship between the electric field and the charge.

[0058]

[0059] Substituting the relationship between charge and potential:

[0060]

[0061] Finally, we obtain the electric field expression for a point in space when three-phase voltages are applied to three-phase parallel buses, where F n This represents the position function of the busbar n relative to the detection point.

[0062] but

[0063] From the above formula, we can obtain that when the detection point is selected below phase B, since r1 = r3, r1′ = r3′, cosθ1 = cosθ3, cosθ1′ = cosθ3′, then F1 = F3, and β 21 =β 23 ,β 11 =β 33 The first and third terms of the above equation can be completely combined, and the final electric field strength z-component is an expression for the potential of phase B. Therefore, the phase B voltage can be measured below the phase B arrester. When the detection point is placed between phase A and phase B, due to the different electrostatic induction coefficients, the first and second terms of the above equation cannot be completely combined. Therefore, theoretically, the phase of the phase C voltage cannot be accurately obtained between the phase A arrester and the phase B arrester. Similarly, there is a theoretical deviation in measuring the phase of the phase A voltage between phase B and phase C, but the deviation is related to the size of the conductor and its spatial position.

[0064] S2. Based on parameters such as surge arresters, busbars, and voltage transformers in the substation, a UHV substation model conforming to actual dimensions was constructed. The phase deviation and amplitude of each flange section in the surge arrester model were simulated and calculated using Simulink, and considered in the finite element simulation. The influence of other charged components such as voltage transformers and grading rings on the phase was also fully considered. The magnitude and phase angle of the voltage at each flange section of the surge arrester were obtained through a simulation model of an RC network, and the voltage excitation was applied to each flange through calculation. Electrostatic field simulation was also employed; by simulating the time points t=0 and t=0.005s, the phase information of the electric field at any point in space could be obtained.

[0065] In a real substation dimensional model, the phase error between the z-component waveform of the electric field intensity between phase A and phase B surge arresters and the phase error between the phase C surge arrester bus voltage and phase C surge arrester bus voltage is less than 1°. This allows for the measurement of phase C voltage without requiring ±180°. Similarly, the phase of phase A surge arrester bus voltage can be measured between phase B and phase C surge arresters, with an error also less than 1° and without requiring ±180°, meeting the requirements for on-site measurement. The phase of phase B surge arrester bus voltage can be measured below phase B surge arrester, but a 180° phase shift is required.

[0066] Step 3: Based on the model established in S2, this embodiment determines the locations of the dual detection points according to three typical surge arrester layout environments (single surge arrester without busbar, single surge arrester with busbar, and two surge arresters with busbar). Specifically, it selects two locations with the smallest errors from three positions: the middle between phase A and phase B, below phase B, and the middle between phase B and phase C, and obtains their errors. Based on the analysis and simulation results, the selection criteria for the dual detection points are summarized as follows: In the case of a single surge arrester without busbar, the dual detection points are selected between the phase A and phase B surge arresters, and below the phase B surge arrester. When a single set of surge arresters is connected to a busbar, the dual detection points are selected at the detection point corresponding to the busbar phase closest to the surge arrester and below the B-phase surge arrester. That is, if the A-phase busbar is closest to the surge arrester, the dual detection points are located between the B-phase and C-phase surge arresters, and below the B-phase surge arrester, respectively. Similarly, if the C-phase busbar is closest to the surge arrester, the dual detection points are selected between the A-phase and B-phase surge arresters, and below the B-phase surge arrester. When two sets of surge arresters are connected to a busbar, the dual detection points are selected below the B-phase surge arrester that is most closely affected by the A-phase and C-phase live conductors, and at the detection point where the live conductor has the greatest influence on the detection position. In other words, assuming that phase A busbar is closest to both sets of surge arresters, and that both sets of surge arresters are installed in the same phase sequence, for one set of surge arresters, if phase C surge arresters of the other set are closest to this set, then the dual detection points are selected respectively below phase B surge arresters of this set, and between phase B and phase C surge arresters of the other set. If phase A surge arresters of the other set are closest to this set, then the dual detection points are selected respectively below phase B surge arresters of the other set, and between phase B and phase C surge arresters of this set. Similarly, assuming phase C busbar is closest, for one set of surge arresters, if phase A surge arresters of the other set are closest to this set, then the dual detection points are selected respectively below phase B surge arresters of this set, and between phase A and phase B surge arresters of the other set. If phase C surge arresters of the other set are closest to this set, then the dual detection points are selected respectively below phase B surge arresters of the other set, and between phase A and phase B surge arresters of this set. In summary, the detection point below the B-phase surge arrester should be located where the influence of the live conductors of phases A and C is as consistent as possible. The other interphase detection point (used to measure the voltage phase of phase A or C) should be selected at the detection point location corresponding to the phase of the live conductor that has the greatest influence on the detection point. The optimal dual detection point can be determined on-site by judging the phase sequence distribution of the busbar and adjacent surge arresters.

[0067] Based on the simulation results, the selected probe locations are as follows:

[0068] In a single-group surge arrester model without a busbar, such as Figure 1As shown, the detection points are mainly selected at Point A (between phase A and phase B surge arresters) and Point B (below phase B surge arrester). This is primarily because the phase of each flange section of the surge arrester gradually lags from top to bottom. Furthermore, under positive phase sequence, since the middle phase B lags behind phase A and leads phase C, the phase lag angle of the phase of the phase A flange increases from top to bottom under the influence of the phase B voltage. With a phase spacing of 22.5m, the phase of the fourth flange section of phase A lags behind the bus voltage by 1.28°. Conversely, the phase lag angle of phase C decreases, and it even leads, leading the bus voltage phase by 0.31° with a phase spacing of 22.5m. Since the phase measurement at the inter-phase detection points inherently has a certain lead error, placing the detection points between phase A and phase B surge arresters minimizes this error. The longitudinal position, based on simulation results, is as follows: Figure 2 As shown, the point can be selected between the surge arrester and the current transformer, at a distance of 1.3m to 2m from the surge arrester.

[0069] In the case of a single surge arrester connected to a busbar, the detection point corresponding to the nearest busbar voltage phase is generally selected as the main detection point. The other detection point is still selected below the B-phase surge arrester. These two detection points have the smallest error. Figure 3 Point B (below the surge arrester of phase B) and Point C (between phase B and phase C) are shown. The main reason is that the closer to the phase A busbar, the smaller the error at Point C for measuring the phase voltage of phase A. In summary, the greater the influence of the busbar on the detection point, the smaller the error. Another point with relatively small error is below phase B.

[0070] In the case of double-set surge arresters with a busbar, the phase voltage detection point for phase B should be selected at a location where the influence of the live conductors in phases A and C is as equal as possible. This minimizes the phase measurement error of phase B. Similarly, the phase-to-phase detection point should be selected at the location corresponding to the phase of the live conductor that has the greatest influence on the detection point, to also minimize error. For example... Figure 4 As shown, the phase errors of the A-phase voltage measured at Point A (between the B-phase and C-phase surge arresters in the first group) and Point C (between the B-phase and C-phase surge arresters in the second group) are relatively small. However, for Point C, the closest conductor to the second group of surge arresters is the A-phase of the first group, and the nearest busbar is also the A-phase. Therefore, the electric field influence of the A-phase conductor is the greatest, and since it is closest, the error is relatively smaller than that of Point A. Regarding the position for measuring the busbar phase of the B-phase surge arrester, the influence of the A-phase and C-phase charged bodies on Point B (below the first group of surge arresters) is relatively even, while Point D (below the B-phase surge arresters in the second group) is excessively affected by the A-phase charged bodies. Therefore, Point B is more ideal than Point D. Ultimately, the dual detection points are selected at Point C and Point B.

[0071] S4. Based on the pattern obtained in S3, a relatively ideal location conforming to the pattern is found on-site for measurement. Simultaneously, the voltage on the PT is compared to confirm the accuracy of the model simulation results and the correctness of the location. The phase sequence of the bus voltage can be obtained using the phase difference of the waveforms at the dual detection points, but the pattern that the electric field component measured by the electric field probe below the B-phase arrester is 180° out of phase with the bus voltage, and that the phase direction of the phase at the phase-to-phase detection point is consistent with the phase direction of the bus voltage to be measured, must be considered. Finally, a correction angle is obtained by comparing with 120°.

[0072] In actual operation, the measurement results of the probe are first compared with the voltage signal acquired on the PT to determine the phase. If the error is less than 1°, it conforms to the analysis results of this invention. Then, the optimal positions of the dual probes are arranged according to the theoretical analysis. By acquiring a 1-second simulated voltage waveform of the dual probes, the time difference Δt between the two waveforms is obtained. Then, based on the relationship between time and phase angle, the phase angle difference Δφ is obtained.

[0073]

[0074] Based on the preceding analysis, the phase of the B-phase voltage measured by the electric field probe is opposite to the electric field waveform, with a phase difference of 180°, while the direction of the electric field components measured by the other two probes is consistent with the bus voltage. Therefore, if a probe is used to measure the B-phase voltage, a 180° phase shift is required.

[0075] Theoretically, a dual-field probe can obtain the phase angle difference between two-phase voltages, but as analyzed above, the phase angle difference deviates from 120°. Therefore, based on the phase angle difference Δφ of the dual-field probe waveform, the correction angle δ is calculated:

[0076]

[0077] If Δφ > 120°, then the waveform with the leading phase is delayed by δ, and the waveform with the lagging phase is advanced by δ. Similarly, if Δφ < 120°, then the waveform with the leading phase is advanced by δ again, and the waveform with the lagging phase is delayed by δ. This method can balance the phase angles of the two waveforms, avoid excessive single-value errors, and ensure that at least one value is close to the true value.

[0078] S5 corrects the voltage phase using the correction angle calculated by S4, and sends the corrected voltage signal and total current signal to the surge arrester testing equipment to obtain resistive current and evaluate the aging status of the surge arrester.

[0079] Finally, based on the phase angle difference of the corrected current and voltage waveforms, the resistive current is measured, and the complete on-site operation is real-time. Figure 5 As shown, the specific steps are as follows:

[0080] 1) Based on the simulation results, find the detection point with the least interference;

[0081] 2) Compare the measured phase of the z-component of the electric field intensity with the waveform acquired by the PT to obtain the error;

[0082] 3) If the error is greater than 1°, return to step 5.1; if the error is less than 1°, proceed to step 5.4.

[0083] 4) Determine the probe placement location, and use the time difference to deduce the phase angle difference Δφ to determine the phase sequence;

[0084] 5) Obtain the correction angle δ using the phase angle difference formula, and then modify the voltage waveform;

[0085] 6) Input the voltage waveform and the current waveform collected by the surge arrester into the equipment, analyze the phase angle difference between the voltage and current, and obtain the resistive current value.

[0086] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for selecting phase detection points for bus voltage of substation surge arresters based on dual probes, characterized in that: A simple model of the z-axis component of the electric field and the conductor charge is established. Through calculations on the simple model, the relationship between the voltage of a three-phase charged body in space and the components of the ground electric field intensity is derived, thus obtaining a method for selecting detection points. Three typical surge arrester arrangements in UHV substations are modeled, including single-group surge arresters, single-group surge arresters with busbars, and double-group surge arresters with busbars. Through simulation, the error between the phase of the z-axis component of the electric field intensity at the detection point and the phase of the busbar voltage is obtained, and the location of the dual detection points of the surge arrester under different operating conditions is determined. The phase sequence of the three-phase voltage is analyzed based on the measurement results of the dual electric field probes. Simultaneously, the phase angle difference between the two detection points is compared with 120° to obtain the voltage correction phase angle δ, from which the phase of the three-phase bus voltage is deduced. Based on the total current of the surge arrester and the voltage phase angle, the resistive current characterizing the aging state of the surge arrester is calculated. This includes the following steps: Step 1: Based on the model of three-phase parallel conductors and three-phase metal spheres, obtain the phase law of the electric field around the three-phase charged body, and find the detection position to measure the phase of the three-phase voltage; establish the relationship between the z-axis component of the electric field and the conductor charge, and use the potential coefficient of the simple model to analyze the relationship between the electric field components and the potential. Step 2: Based on the parameters of the surge arrester, busbar, and voltage transformer of the substation, build a model of the UHV substation. The phase deviation and amplitude of each flange in the surge arrester model are simulated and calculated using Simulink and considered in the finite element simulation. At the same time, the influence of the voltage transformer and equalizing ring on the phase is also considered. Step 3: Determine the location of the dual detection points for the following surge arrester arrangements: single surge arrester without busbar, single surge arrester with busbar, and two surge arresters with busbar. Step 4: Based on the location of the dual detection points obtained in Step 3, find a location with less interference on site for measurement. At the same time, take the voltage signal on the PT for comparison to determine the correctness of the model simulation results and the location selection. Use the phase difference of the waveforms of the dual detection points to obtain the phase sequence of the bus voltage. Consider the rule that the electric field component measured by the electric field probe below the B-phase arrester is 180° out of phase with the bus voltage, and that the phase of the interphase detection point is consistent with the phase direction of the measured bus voltage, compare it with 120° to obtain the correction angle. Step 5: Based on the phase angle difference of the corrected current and voltage waveforms, the resistive current is measured.

2. The method for selecting the phase detection point of the bus voltage of a substation surge arrester based on dual probes according to claim 1, characterized in that: The specific implementation of step 1 includes: Using Gauss's law, we obtain the expression for the relationship between electric field and charge: Substitute the relationship between charge and potential: The electric field expression at a point in space when a three-phase voltage is applied to a three-phase conductor is obtained: From the above formula, we can obtain that when the detection point is selected below phase B, since r1 = r3, r1′ = r3′, cosθ1 = cosθ3, cosθ1′ = cosθ3′, then F1 = F3, and β 21 =β 23 ,β 11 =β 33 Combining the first and third terms of the above equation, the remaining expression for the B-phase potential leads to the conclusion that: when measuring the B-phase voltage below the B-phase arrester; when measuring the phase of the B-phase bus below the B-phase arrester, since the direction of the bus voltage is opposite to the z-component of the electric field strength, the electric field component measured by the probe differs from the bus voltage by 180°; when measuring the C-phase voltage between phases A and B, and when measuring the A-phase voltage between phases B and C, there are phase deviations.

3. The method for selecting the phase detection point of the bus voltage of a substation surge arrester based on dual probes according to claim 1, characterized in that: The specific implementation of step 2 includes: Step 2.1: Based on the distribution of surge arresters, voltage transformers, and busbars, build finite element models that conform to the actual size, including models of surge arresters with a single set of surge arresters without busbars, with a single set of surge arresters with busbars, and with two sets of surge arresters with busbars. Step 2.2: Obtain the magnitude and phase angle of the voltage of each flange of the surge arrester through the simulation model of the RC network. Through calculation, apply the voltage excitation to each flange. At the same time, use electrostatic field simulation, select two times t=0 and t=0.005s for simulation, and obtain the phase information of the electric field at any point in space.

4. The method for selecting the phase detection point of the bus voltage of a substation surge arrester based on dual probes according to claim 3, characterized in that: The specific implementation of step 3 includes: Step 3.1: Based on the model built in Step 2.1, under the actual substation size model, when the phase error between the z-component waveform of the electric field intensity between phase A and phase B surge arresters and the phase error between the bus voltage of phase C surge arrester are less than 1°, the voltage of phase C surge arrester is measured between phase A and phase B surge arresters, and there is no ±180° phase difference; when the phase error between the z-component waveform of the electric field intensity between phase B and phase C surge arresters and the phase error between the bus voltage of phase A surge arrester are less than 1°, the voltage of phase A surge arrester is measured between phase B and phase C surge arresters, and there is no ±180° phase difference; the phase of the bus voltage of phase B surge arrester measured below phase B surge arrester needs to be shifted by 180°. Step 3.2: From Step 3.1, we can conclude that: For a single surge arrester without a busbar, the two detection points are selected respectively between the A-phase and B-phase surge arresters, and below the B-phase surge arrester; For a single surge arrester with a busbar, the two detection points are selected respectively at the detection point corresponding to the busbar phase closest to the arrester, and below the B-phase surge arrester; For two surge arresters with a busbar, the two detection points are selected respectively below the B-phase surge arrester that is most closely affected by the A-phase and B-phase live parts, and at the detection point where the live part has the greatest impact on the detection position.

5. The method for selecting the phase detection point of the bus voltage of a substation surge arrester based on dual probes according to claim 4, characterized in that: The specific implementation of step 4 includes: First, the phase of the probe measurement result and the voltage signal acquired on the PT are compared. If the error is less than 1°, the dual probe points are arranged according to the position obtained in step 3. By acquiring the dual probe simulated voltage waveform for 1 second, the time difference Δt between the two waveforms is obtained. Then, based on the relationship between time and phase angle, the phase angle difference Δφ is obtained. If the probe is used to measure the voltage of phase B, the phase needs to be shifted by 180°. Calculate the correction angle δ based on the phase angle difference Δφ of the dual electric field probe waveforms: If Δφ>120°, then the waveform with the leading phase will lag by δ, and the waveform with the lagging phase will lead by δ. Similarly, if Δφ<120°, then the waveform with the leading phase will lead by δ again, and the waveform with the lagging phase will lag by δ.

6. The method for selecting the phase detection point of the bus voltage of a substation surge arrester based on dual probes according to claim 5, characterized in that: The specific implementation of step 5 includes: Step 5.1: Based on the conclusions obtained in Step 3.2, find the detection point with the least interference; Step 5.2: Compare the measured z-component phase of the electric field intensity with the waveform acquired by the PT to obtain the error; Step 5.3: If the error is greater than 1°, return to step 5.1; if the error is less than 1°, proceed to step 5.

4. Step 5.4: Determine the probe placement location, and use the time difference to deduce the phase angle difference Δφ to determine the phase sequence; Step 5.5: Obtain the correction angle δ using the phase angle difference formula, and modify the voltage waveform accordingly; Step 5.6: Input the voltage waveform and the current waveform collected by the surge arrester into the equipment, analyze the phase angle difference between the voltage and current, and obtain the resistive current value.

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