Capacitive voltage transformer capacitance online monitoring method, device, equipment and storage medium

Abstract

The present invention discloses an online monitoring method, device, equipment and storage medium for the capacitance of a capacitor voltage transformer. An online monitoring method for the capacitance of a capacitor voltage transformer comprises: continuously obtaining the harmonic variation of each harmonic component of the end-screen grounding current of the capacitor voltage transformer; calculating the initial probability of m preset capacitance variations for each harmonic variation; and determining the actual variation of the capacitor voltage transformer at the corresponding moment based on the initial probability corresponding to each harmonic variation. By directly obtaining the end-screen grounding current of the online capacitor voltage transformer and calculating the actual variation of the capacitance of the capacitor voltage transformer based on the corresponding relationship between the end-screen node current and the capacitance of the capacitor voltage transformer, the capacitance can be monitored without affecting the operating state of the capacitor voltage transformer, without exiting the capacitor voltage transformer from the operating state.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitance change monitoring of capacitive voltage transformers, and in particular to a method, device, equipment and storage medium for online monitoring of capacitance of a capacitive voltage transformer. Background Art

[0002] Capacitor voltage transformer (CVT) is a power system device used to measure high voltage. It is widely used in high voltage measurement of power systems due to its small size, light weight, simple structure and low price.

[0003] The capacitive voltage transformer adopts the principle of capacitive voltage division, and its main components are voltage-dividing capacitor, compensating reactor, intermediate transformer and damping device. The voltage-dividing capacitor is composed of a high-voltage capacitor and a medium-voltage capacitor in series. Due to its working principle, the voltage-dividing capacitor will be subjected to high voltage for a long time. As the use time increases, the voltage-dividing capacitor is prone to insulation aging and capacitance reduction. In severe cases, the capacitor unit may even be broken down, which will affect the accuracy of the measurement value and the normal and stable operation of the power system. The existing method of monitoring the capacitance change of the capacitive voltage transformer requires the capacitive voltage transformer to be disconnected from work, causing the operation of some systems based on the capacitive voltage transformer to stop working.

[0004] However, the existing method of monitoring capacitive voltage transformers requires the capacitive voltage transformer to be disconnected from its working state, which will affect the normal operation of the system that relies on the capacitive voltage transformer, and requires a large amount of manpower and material resources during the measurement process. In addition, the measurement of the capacitive voltage transformer requires manual arrangement of the measurement timing, and the data has a certain lag, making it impossible to achieve timely judgment on the operating status of the capacitive voltage transformer. Summary of the invention

[0005] The present invention provides a method, device, equipment and storage medium for online monitoring of capacitance of a capacitor voltage transformer, so as to solve the problem that the capacitor voltage transformer needs to stop running during monitoring.

[0006] According to one aspect of the present invention, there is provided a method for online monitoring of capacitance of a capacitive voltage transformer, comprising:

[0007] Continuously obtain the harmonic variation of each harmonic component of the end screen grounding current of the capacitor voltage transformer;

[0008] Calculating the initial probability of m preset capacitance changes for each harmonic change;

[0009] The actual variation of the capacitive voltage transformer at the corresponding moment is determined based on the initial probability corresponding to each harmonic variation.

[0010] Optionally, the continuously acquiring each harmonic component of the end screen grounding current of the capacitor voltage transformer includes:

[0011] Continuously obtain the end screen grounding current of the capacitor voltage transformer;

[0012] Performing Fourier transformation on the end-screen grounding current to obtain harmonic components of the end-screen grounding current;

[0013] The harmonic variation of each harmonic component corresponding to each acquisition time is calculated based on each harmonic component.

[0014] Optionally, the calculating of the initial probabilities of m preset capacitance changes for each harmonic change includes:

[0015] The initial probabilities of the preset m capacitance changes are calculated for each of the harmonic changes based on a preset Gaussian distribution probability density function.

[0016] Optionally, before calculating the initial probability of the preset m capacitance changes for each harmonic change, the method further includes:

[0017] Divide the entire domain Θ of the capacitance value range of the capacitive voltage transformer into m intervals [a k ,b k ], each of the intervals is a capacitance change;

[0018] The space (-∞, μ-3σ) and (μ+3σ, +∞) are divided into an interval [a k ,b k ];

[0019] Wherein, μ is the harmonic variation, and σ is the standard deviation of Gaussian distribution.

[0020] Optionally, the Gaussian distribution probability density function is:

[0021]

[0022]

[0023] P n (X k ) is the initial probability corresponding to each capacitance change under each harmonic change; n is the nth harmonic component; X k is the kth capacitance change, X1∩X2...X k ...∩X m =θ,X k =[a k ,b k], k∈[0,m]; μ is the harmonic variation; σ is the standard deviation of Gaussian distribution.

[0024] Optionally, determining the actual change of the capacitive voltage transformer at a corresponding moment based on the initial probability corresponding to each harmonic change includes:

[0025] Using the evidence theory fusion algorithm to fuse the initial probabilities corresponding to the harmonic changes, to obtain the fusion probabilities of the preset m capacitance changes;

[0026] The capacitance change corresponding to the maximum fusion probability is obtained as the actual change of the capacitive voltage transformer.

[0027] Optionally, the evidence theory fusion algorithm is as follows:

[0028]

[0029]

[0030] Among them, F(X k ) is the fusion probability corresponding to the kth capacitance change; P n (X k ) is the initial probability corresponding to each of the capacitance changes under each of the harmonic changes; m is the interval range corresponding to the mth capacitance change.

[0031] According to another aspect of the present invention, there is provided a device for online monitoring the capacitance of a capacitive voltage transformer, comprising:

[0032] An acquisition module, used for continuously acquiring harmonic variation of each harmonic component of the end-screen grounding current of the capacitor voltage transformer;

[0033] A first calculation module, used for calculating the initial probability of m preset capacitance changes for each harmonic change;

[0034] The second calculation module is used to determine the actual change of the capacitive voltage transformer at a corresponding moment based on the initial probability corresponding to each harmonic change.

[0035] According to another aspect of the present invention, there is provided a device for online monitoring the capacitance of a capacitive voltage transformer, the device comprising:

[0036] at least one processor; and

[0037] a memory communicatively connected to the at least one processor; wherein,

[0038] The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the online monitoring method for the capacitance of a capacitive voltage transformer described in any embodiment of the present invention.

[0039] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the online monitoring method for the capacitance of a capacitive voltage transformer described in any embodiment of the present invention when executed.

[0040] The technical solution of the embodiment of the present invention continuously obtains the end-screen grounding current of the capacitive voltage transformer, then obtains the change of each harmonic component based on the end-screen grounding current, and then calculates the initial probability of each harmonic change corresponding to the preset m capacitance changes, and finally determines the actual change of the capacitance of the capacitive voltage transformer based on the initial probability. In this process, the end-screen grounding current of the online capacitive voltage transformer is directly obtained, and the actual change of the capacitance of the capacitive voltage transformer is calculated based on the corresponding relationship between the end-screen node current and the capacitance of the capacitive voltage transformer. The capacitance can be monitored without affecting the operating state of the capacitive voltage transformer, and the capacitive voltage transformer does not need to be withdrawn from the operating state. Compared with the existing power outage test, the online monitoring is richer in data, which can not only discover hidden dangers in time, but also the massive data can support the realization of digital power grid and intelligent operation and maintenance.

[0041] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1a This is a flow chart of a method for online monitoring of capacitance of a capacitive voltage transformer provided according to Embodiment 1 of the present invention;

[0044] Figure 1b is an equivalent circuit diagram of a capacitive voltage transformer provided by an embodiment of the present invention;

[0045] Figure 2aThis is a flow chart of a method for online monitoring of capacitance of a capacitive voltage transformer provided according to a second embodiment of the present invention;

[0046] Figure 2b is a schematic diagram of an algorithm provided in Embodiment 2 of the present invention;

[0047] Figure 2c This is a harmonic voltage fluctuation diagram of a certain line measured according to the second embodiment of the present invention;

[0048] Figure 2d is a simulation result diagram provided by the second embodiment of the present invention;

[0049] Figure 2e is another simulation result diagram provided by the second embodiment of the present invention;

[0050] Figure 2f is a harmonic variation data diagram provided by the second embodiment of the present invention;

[0051] Figure 2g is another simulation result diagram provided by the second embodiment of the present invention;

[0052] Figure 2h is an output result data graph provided by the second embodiment of the present invention;

[0053] Figure 2i is another simulation result diagram provided by the second embodiment of the present invention;

[0054] Figure 2j This is a diagram of measured data of the secondary side voltage of a certain substation bus provided by the second embodiment of the present invention;

[0055] Figure 2k is another simulation result diagram provided by the second embodiment of the present invention;

[0056] Figure 3 2 is a schematic structural diagram of an online monitoring device for capacitance of a capacitive voltage transformer provided according to a third embodiment of the present invention;

[0057] Figure 4 It is a structural schematic diagram of an electronic device for implementing the online monitoring method of the capacitance of a capacitive voltage transformer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0059] It should be noted that the terms "initial", "actual", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0060] Embodiment 1

[0061] Figure 1a A flowchart of a method for online monitoring of capacitance of a capacitive voltage transformer provided in Embodiment 1 of the present invention, Figure 1b The equivalent circuit diagram of the capacitive voltage transformer provided in the embodiment of the present invention is applicable to the situation of realizing online monitoring of the capacitance of the voltage-dividing capacitor of the capacitive voltage transformer, avoiding the need to disassemble and assemble the capacitive voltage transformer during the capacitance detection process of the capacitive voltage transformer. The method can be performed by an online monitoring device for the capacitance of the capacitive voltage transformer, and the online monitoring device for the capacitance of the capacitive voltage transformer can be implemented in the form of hardware and / or software. The online monitoring device for the capacitance of the capacitive voltage transformer can be configured in a computer device, which can be a mobile terminal such as a mobile phone, a tablet computer, a wearable device (such as a smart watch, smart glasses, etc.), or the computer device can be a non-mobile terminal such as a personal PC or a smart TV.

[0062] Capacitor Voltage Transformers (CVT) are voltage transformers that are divided by series capacitors and then reduced and isolated by electromagnetic transformers. They are used as meters, relay protection, etc. Capacitor voltage transformers can also couple carrier frequencies to transmission lines for long-distance communications, remote measurements, selective line high-frequency protection, remote control, teletypewriting, etc. Therefore, compared with conventional electromagnetic voltage transformers, capacitor voltage transformers can prevent ferromagnetic resonance caused by voltage transformer core saturation, and have many advantages in terms of economy and safety.

[0063] The voltage divider capacitor is composed of a high-voltage capacitor and a medium-voltage capacitor connected in series. Due to its working principle, the voltage divider capacitor will be subjected to high voltage for a long time. As the use time increases, the voltage divider capacitor is prone to insulation aging and capacitance reduction, and in severe cases, the capacitor unit may even be broken down. Therefore, it is necessary to regularly monitor the capacitance of the capacitive voltage transformer to ensure the working reliability of the capacitive voltage transformer and the normal and stable operation of the power system.

[0064] As shown in FIG1 , the online monitoring method for capacitance of a capacitive voltage transformer provided in an embodiment of the present invention includes:

[0065] S110, continuously obtaining harmonic changes of each harmonic component of the end-screen grounding current of the capacitor voltage transformer.

[0066] In the embodiment of the present invention, continuous acquisition mainly refers to collecting the end screen grounding current of the capacitive voltage transformer according to a preset time interval. The preset time interval can be set based on actual needs, and the specific time interval duration is not mandatory here.

[0067] In order to make the radial and axial field strengths of the capacitive voltage transformer uniform, its insulation structure generally adopts a capacitive type. The insulation of this type of capacitive insulation equipment is made of layers of insulating paper, that is, many insulating layers are wrapped on the conductive rod, and many aluminum foils are sandwiched in between according to the field strength distribution characteristics to form a string of concentric cylindrical capacitors. The outermost aluminum foil (i.e., the end screen) is led out through a small bushing to measure the dielectric loss and capacitance of the bushing, and the end screen needs to be grounded during the operation of the capacitive voltage transformer. The end screen grounding current obtained in the embodiment of the present invention refers to the current flowing through the wire when the end screen is grounded.

[0068] In an embodiment of the present invention, the harmonic components of the end-screen grounding current mainly refer to the sinusoidal components whose frequencies are integer multiples of the original periodic current frequency obtained by expanding the end-screen grounding current in Fourier series. The harmonic current whose frequency is equal to k times the original periodic current frequency is called kth harmonic current.

[0069] The harmonic variation of each harmonic component can be obtained by calculating the difference between the kth harmonic current at the moment t currently obtained and the kth harmonic current at the moment t-1 previously obtained as the harmonic variation of the kth harmonic current. In addition, the harmonic variation can also be the difference between the kth harmonic current at the moment t currently obtained and the kth harmonic current at the moment t-2 obtained twice previously, or the difference between two harmonic components separated by more time intervals.

[0070] S120 , calculating the initial probabilities of the preset m capacitance changes for each harmonic change.

[0071] Among them, there are m capacitance changes preset, m>0. In the embodiment of the present invention, the preset m capacitance changes are the capacitance change values ​​of the assumed capacitive voltage transformer, and the value range is between negative infinity and positive infinity. Secondly, it can be expressed by a specific capacitance value, or expressed in the form of a percentage, and the percentage is used as an example for explanation in the embodiment of the present invention.

[0072] In the embodiment of the present invention, since the m capacitance changes are the capacitance change values ​​of the assumed capacitive voltage transformer, the range covered by the m capacitance changes when set should be relatively complete, and as many capacitance changes as possible should be set if computing power permits.

[0073] In an optional embodiment, the values ​​of the m capacitance changes can also be limited in the form of intervals, that is, one capacitance change is an interval. By dividing the entire domain into m intervals (capacitance changes), subsequent initial probability calculations are performed to ensure that the final calculation results fully cover the capacitance change range of the capacitive voltage transformer, thereby ensuring the reliability of data calculation.

[0074] like Figure 1b As shown in the circuit equivalent diagram of the capacitive voltage transformer provided in the embodiment of the present invention, in the figure, U1 is the primary side voltage of the capacitive voltage transformer; C1 and C2 constitute a voltage dividing capacitor; L is a compensating reactor; T is an intermediate transformer; L d is the load; I1 is the end screen grounding current of the capacitive voltage transformer (N-terminal current); I2 is the primary winding grounding current of the intermediate transformer of the capacitive voltage transformer (X-terminal current).

[0075] Then, the primary voltage of the capacitor voltage transformer can be expressed as:

[0076]

[0077] Where j is the imaginary unit and ω is the phase angle.

[0078] In actual implementation, since I1>>I2, formula (1) can be changed to:

[0079]

[0080] From the above formula (2), it can be seen that the changes in the main capacitance parameters C1 and C2 of the capacitive voltage transformer can be reflected by the changes in the magnitude of the end-screen grounding current I1. There are two factors that affect the end-screen grounding current I1 (jω), namely the primary side voltage U1 (jω) and the main capacitance parameters C1, C2. Therefore, if it can be ruled out that the change in the harmonic current I1 (jω) is caused by the influence of the primary side voltage U1 (jω), then it can be considered that it is caused by the change in the main capacitance parameters C1, C2. Therefore, in the embodiment of the present invention, the collection conditions for the end-screen grounding current should also be added with the limitation of the primary side voltage to ensure that the primary side voltage is the same during each collection.

[0081] Based on formula (2), in the embodiment of the present invention, the corresponding relationship between the harmonic change of the end screen grounding current and the actual change of the capacitance is set to satisfy the Gaussian distribution, that is, it is assumed that there is a probability corresponding relationship between the measured value and the actual capacitance. Thus, the initial probability of m capacitance changes corresponding to the harmonic change can be calculated, that is, the possibility of calculating each capacitance change as a real change.

[0082] S130. Determine the actual change of the capacitive voltage transformer at the corresponding moment based on the initial probability corresponding to each harmonic change.

[0083] In the above steps, the initial probability of m capacitance changes under the harmonic changes corresponding to the harmonic components of the end-screen grounding current is calculated. In this step, it is necessary to judge the capacitance change closest to the actual change from the calculation results as the actual change in the embodiment of the present invention. The closest capacitance change can be judged and obtained in a variety of ways, such as the simplest way of directly taking the capacitance change corresponding to the extreme value of the initial probability value as the actual change, or fusing the calculated initial probability through the evidence theory fusion algorithm, and finally judging the capacitance change closest to the actual value as the actual change.

[0084] In an embodiment of the present invention, the end-screen grounding current of the capacitor voltage transformer is continuously obtained, and then the change of each harmonic component thereof is obtained based on the end-screen grounding current, and then the initial probability of each harmonic change corresponding to the preset m capacitance changes is calculated, and finally the actual change of the capacitance of the capacitor voltage transformer is determined based on the initial probability. In this process, the end-screen grounding current of the online capacitor voltage transformer is directly obtained, and the actual change of the capacitance of the capacitor voltage transformer is calculated based on the corresponding relationship between the end-screen node current and the capacitance of the capacitor voltage transformer. The capacitance can be monitored without affecting the operating state of the capacitor voltage transformer, and the capacitor voltage transformer does not need to be withdrawn from the operating state. In addition, compared with the existing power outage test, online monitoring is richer in data, because online monitoring can obtain CVT operating information in real time and continuously, which can not only discover hidden dangers in time, but also support the realization of digital power grid and intelligent operation and maintenance with massive data.

[0085] Embodiment 2

[0086] Figure 2a This is a flowchart of a method for online monitoring the capacitance of a capacitive voltage transformer provided in the second embodiment of the present invention. This embodiment further refines the entire monitoring method based on the above embodiment. As shown in Figure 2, the method includes:

[0087] S201. Continuously obtain the end-screen grounding current of the capacitive voltage transformer.

[0088] In a specific implementation, a current collection device is provided between the end screen of the capacitive voltage transformer and the ground to continuously collect the end screen grounding current, and then the collected data is stored and uploaded for processing. For the collection requirements of the end screen grounding current, reference can be made to the corresponding part in step S110 of the first embodiment, and no further elaboration is given here.

[0089] S202, performing Fourier transform on the end-screen grounding current to obtain harmonic components of the end-screen grounding current.

[0090] In a specific implementation, the collected end-screen grounding current of the capacitive voltage transformer is subjected to Fourier transformation to decompose the end-screen grounding current into multiple harmonic components.

[0091] S203: Calculate the harmonic variation of each harmonic component corresponding to each acquisition time based on each harmonic component.

[0092] In a specific implementation, the harmonic change amount can be the calculated difference between the harmonic component at the current moment t and the previous moment t-1, or the difference between the value of the harmonic component at the current moment t and a plurality of moments ago. In the following embodiments, if not mentioned, the default refers to the difference between the current moment t and the previous moment t-1.

[0093] S204 , calculating the initial probabilities of the preset m capacitance changes for each harmonic change based on a preset Gaussian distribution probability density function.

[0094] Exemplarily, the preset m capacitance changes can be obtained by dividing the entire capacitance value range of the capacitive voltage transformer into m intervals [a k ,b k ], each interval is regarded as a capacitance change.

[0095] Due to the characteristics of Gaussian distribution, P(μ-3σ≤x≤μ+3σ)>99.7%, that is, the probability density integral of the capacitance value outside 3σ accounts for less than 0.3% of the total integral. Therefore, the space (-∞,μ-3σ) and (μ+3σ,+∞) are divided into an interval [a k ,b k ] to effectively reduce the amount of capacitance change, reduce the amount of calculation, and reduce the requirements for computing power.

[0096] Among them, μ is the harmonic variation and σ is the standard deviation of Gaussian distribution.

[0097] In the embodiment of the present invention, the Gaussian distribution probability density function is set as:

[0098]

[0099]

[0100] P n (X k ) is the initial probability corresponding to each capacitance change under each harmonic change; n is the nth harmonic component; X k is the kth capacitance change, X1∩X2...X k ...∩X m =θ,X k =[a k ,b k ], k∈[0,m]; μ is the harmonic variation; σ is the standard deviation of Gaussian distribution.

[0101] S205 , using the evidence theory fusion algorithm to fuse the initial probabilities corresponding to the harmonic changes, to obtain the fusion probabilities of the preset m capacitance changes.

[0102] Among them, the evidence theory fusion algorithm (DS evidence theory data fusion algorithm) is a probabilistic reasoning theory that can fuse multiple independent variables. DS evidence theory contains the following elements.

[0103] 1) Hypothesis space Θ, which represents the set of all possible hypotheses.

[0104] 2) Basic Probability Assignment (BPA), which represents the basic probability process of each evidence (sub-learner) for each element in the hypothesis space Θ.

[0105] 3) Basic probability distribution function (mass function), the function used in the BPA process. Assume that the probability distribution function M is: 2 Θ →[0,1], then And ∑M(A)=1,A∈Θ, where Represents the empty set.

[0106] for Assume that there are n mass functions M1,M2...M on the space Θ n The synthesis rule is shown in formula (3).

[0107]

[0108] In the formula, K is called the normalization factor, and its calculation method is shown in formula (4).

[0109]

[0110] Where A1, A2...An are the probability densities of M1, M2,...Mn for event A, and o represents the empty set.

[0111] In the embodiment of the present invention, the evidence theory fusion algorithm is modified as follows:

[0112]

[0113]

[0114] Among them, F(X k ) is the fusion probability corresponding to the kth capacitance change; P n (X k ) is the initial probability corresponding to each capacitance change under each harmonic change; m is the interval range corresponding to the mth capacitance change.

[0115] S206. Obtain the capacitance change corresponding to the maximum fusion probability as the actual change of the capacitive voltage transformer.

[0116] In the above steps, the probability of whether each capacitance change belongs to a capacitive voltage transformer is calculated accordingly, and a corresponding fusion probability value is obtained respectively, which represents the probability of whether the corresponding capacitance change is the capacitance change of the capacitive voltage transformer. Therefore, in this step, the capacitance change corresponding to the maximum fusion probability is taken as the actual change of the capacitive voltage transformer.

[0117] Optionally, in the embodiment of the present invention, an evidence credibility factor G may be introduced to measure the credibility of the result.

[0118]

[0119] Among them, X k ∈Θ.

[0120] When multiple pieces of evidence point to greater divergence, G is smaller, and when the evidence points to higher consistency, G is larger. Introducing the credibility factor is beneficial to reducing the amount of calculation in the algorithm implementation and the credibility of the evaluation results.

[0121] Furthermore, when G is greater than 95%, according to X k In the interval, the capacitance changes by X k When G is less than 10%, it is judged as interference.

[0122] Optionally, when G∈[10%, 95%], it means that the calculation result at this moment can neither be regarded as interference nor as a change in capacitance, and thus the calculation result at the next moment is introduced as an additional criterion.

[0123] Specifically, refer to Figure 2b The algorithm diagram provided in , when the calculated G is between 10% and 95%, the end-screen grounding current at the current moment is replaced by the end-screen grounding current at the next moment (t+1), and then substituted into S203 for recalculation, if G still falls between 10% and 95%, the end-screen grounding current at the next moment (t+2) is continued to replace the end-screen grounding current at the current moment (t) for recalculation until G is outside 10% to 95%.

[0124] Simulation verification:

[0125] 1. Anti-interference performance verification 1

[0126] like Figure 2c This is the measured harmonic voltage fluctuation diagram of a certain line, such as Figure 2c As shown, 15 continuous sampling moments are provided within 45 seconds, and the measured indicators include fundamental voltage, third harmonic voltage, fifth harmonic voltage, and seventh harmonic voltage.

[0127] Assuming that the main capacitance of the capacitor voltage transformer remains unchanged during this time period, the percentage of harmonic change flowing through the main capacitance should remain the same. Taking the change value as the harmonic change in the embodiment of the present invention as input, the capacitor voltage transformer capacitance online monitoring method provided in the embodiment of the present invention is used for simulation, and the obtained results are as follows: Figure 2d shown.

[0128] like Figure 2dFrom the simulation results in , we can see that the credibility factor G at 15 moments is less than 10%, indicating that the evidence is not sufficiently pointed and is judged to be harmonic interference.

[0129] 2. Anti-interference performance verification 2

[0130] Assume a situation where, due to harmonic interference, the incremental change characteristics of each component of the harmonic current at time n are just close to the trend caused by the change of the main capacitance. Therefore, the value of the credibility factor G calculated based on the online monitoring method for the capacitance of the capacitor voltage transformer provided in the embodiment of the present invention at time n should be between 10% and 95%.

[0131] At this point, the evidence is not enough to be considered that the main capacitor has changed, and it cannot be judged as caused by interference, and more evidence needs to be introduced. In this embodiment, the harmonic current at the n+1 moment is subtracted from the harmonic current at the n-1 moment, and this increment is re-adopted using the online monitoring method for the capacitance of the capacitive voltage transformer provided in the embodiment of the present invention for DS operation, and this result and the result at the n moment are once again applied to the DS algorithm. If the output result is still between 10% and 95%, the increments at the n+2 moment and the n-1 moment are continued to be introduced for calculation. If the output result is less than 10% or greater than 95%, the corresponding result is output. The increments of each component of the harmonic current at a certain moment (n moment) are selected as 0%, -2.8%, -0%, and 0%, respectively. According to the output result of the DS algorithm at the n moment, G is 48.2%, and the capacitance offset value is 0.6%. Continue to introduce the next moment criterion to continue to judge. Table 1 shows the increments of the harmonic current at different moments to the n moment.

[0132] Table 1

[0133] time n+1 n+2 n+3 Fundamental wave increment 0％ 0％ 0％ Third harmonic increment 0％ 1.4％ 0.1％ Fifth harmonic increment 0％ 0％ 0％ Seventh harmonic increment -2.9％ -0.2％ -0.2％

[0134] Figure 2e This is a simulation result based on the above data. It can be seen that the value of the credibility factor G does not reach 96.1% until time n+3. At this time, the corresponding capacitance offset value is 0.04%, which basically means that the main capacitance has not changed.

[0135] 3. Accuracy Verification 1

[0136] like Figure 2f Adjust the harmonic change data in simulation experiment 1, and adjust the increments at the fourth moment to 5.5%, 5.4%, 5%, and 5.2%, respectively, indicating that the capacitance of the main capacitor at the fourth moment has changed. Substituting the above data into the online monitoring method for capacitance of a capacitor voltage transformer provided in an embodiment of the present invention, the simulation results are as follows: Figure 2g shown.

[0137] According to the simulation results, the credibility factor at the fourth moment reached 98.74%, indicating that the evidence is very clear. The output of the DS algorithm at the fourth moment is as follows: Figure 2h As shown above. Figure 2h From the content, we can see that the bar graph represents the probability density of the DS algorithm output result, and the horizontal axis represents the capacitance offset value. The peak of the bar graph appears at 5.4%, indicating that after the algorithm's judgment, the most likely capacitance offset value is 5.4%, which is consistent with the preset input.

[0138] 4. Accuracy Verification 2

[0139] Based on simulation 3, let's assume another situation. Suppose that the main capacitor value increases by 1% at time n. However, due to the existence of harmonic interference in the power grid, the measured increment characteristics of each component of the harmonic current are not obvious. If the increments of each component of the harmonic current at time n are 1%, -1.8%, 1%, and 1%, respectively, the value of the credibility factor G in the DS algorithm result at time n is 48.6%. Therefore, it is also necessary to introduce the next moment criterion to continue the judgment. Table 2 shows the increments of each component of the harmonic current based on simulation 3, assuming that the main capacitor increases by 1%.

[0140] Table 2

[0141] time n+1 n+2 n+3 Fundamental wave increment 1％ 1％ 1％ Third harmonic increment 1％ 2.4％ 1.1％ Fifth harmonic increment 1％ 1％ 1％ Seventh harmonic increment -1.9％ 0.8％ 0.8％

[0142] like Figure 2i As shown in the simulation results, it can be seen from the results that the value of the credibility factor G does not reach 98.7% until the moment n+3, when the capacitance offset value is 0.9%. It should be noted that in order to reduce the amount of calculation, in the embodiment of the invention, the step size of the capacitance offset value is set to 0.3% during the design, that is, the maximum error of the algorithm is 0.3%. The smaller the step size is set, the smaller the error will be, but the amount of calculation will be greater.

[0143] 5. Comprehensive simulation

[0144] Select the measured data of the secondary side voltage of the CVT busbar of a substation as follows Figure 2j As shown. Before and after obtaining this data, the CVT power failure test results show that the CVT capacitance has not changed. This data is converted into capacitor harmonic current according to the formula and input into the algorithm set in this paper. The simulation results are as follows Figure 2k As shown. In the simulation results, except for the 35th and 40th moments, the credibility factor exceeded 95%, and the other moments failed to reach 95%, so it was judged that the capacitance was offset. The credibility factor exceeded 95% at the 35th and 40th moments, and the corresponding capacitance offset value was 0% at that moment. Therefore, in summary, the capacitance offset during this period was 0%, which is consistent with the actual situation.

[0145] Embodiment 3

[0146] Figure 3 This is a schematic diagram of the structure of an online monitoring device for capacitance of a capacitive voltage transformer provided in the third embodiment of the present invention. Figure 3 As shown, the device includes an acquisition module 31, a first calculation module 32, and a second calculation module 33, wherein:

[0147] An acquisition module 31 is used to continuously acquire the harmonic variation of each harmonic component of the end-screen grounding current of the capacitor voltage transformer;

[0148] A first calculation module 32, configured to calculate the initial probability of m preset capacitance changes for each harmonic change;

[0149] The second calculation module 33 is used to determine the actual change amount of the capacitor voltage transformer at the corresponding moment based on the initial probability corresponding to each harmonic change amount.

[0150] Optionally, the acquisition module 31 includes:

[0151] An acquisition unit, used for continuously acquiring the end screen grounding current of the capacitor voltage transformer;

[0152] A transformation unit, used for performing Fourier transformation on the end-screen grounding current to obtain various harmonic components of the end-screen grounding current;

[0153] The change calculation unit is used to calculate the harmonic change amount of each harmonic component corresponding to each acquisition time based on each harmonic component.

[0154] Optionally, the first calculation module 32 includes:

[0155] The probability calculation unit is used to calculate the initial probability of the preset m capacitance changes for each harmonic change based on a preset Gaussian distribution probability density function.

[0156] Also includes:

[0157] The interval division unit is used to divide the entire domain Θ of the capacitance value range of the capacitive voltage transformer into m intervals [a k ,b k ], each interval is a capacitance change; the space (-∞,μ-3σ) and (μ+3σ,+∞) are divided into an interval [a k ,b k ];

[0158] Among them, μ is the harmonic variation and σ is the standard deviation of Gaussian distribution.

[0159] Among them, the Gaussian distribution probability density function is:

[0160]

[0161]

[0162] P n (X k ) is the initial probability corresponding to each capacitance change under each harmonic change; n is the nth harmonic component; X k is the kth capacitance change, X1∩X2...X k ...∩X m =θ,X k =[a k ,b k ], k∈[0,m]; μ is the harmonic variation; σ is the standard deviation of Gaussian distribution.

[0163] Optionally, the second calculation module 33 includes:

[0164] A fusion unit, used to fuse the initial probabilities corresponding to the harmonic changes using an evidence theory fusion algorithm to obtain fusion probabilities of the preset m capacitance changes;

[0165] The result acquisition unit is used to acquire the capacitance change corresponding to the maximum fusion probability as the actual change of the capacitive voltage transformer.

[0166] Among them, the evidence theory fusion algorithm is as follows:

[0167]

[0168]

[0169] Among them, F(X k ) is the fusion probability corresponding to the kth capacitance change; P n (X k ) is the initial probability corresponding to each capacitance change under each harmonic change; m is the interval range corresponding to the mth capacitance change.

[0170] The online monitoring device for capacitance of a capacitor voltage transformer provided in an embodiment of the present invention can execute the online monitoring method for capacitance of a capacitor voltage transformer provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0171] Embodiment 4

[0172] Figure 4A schematic diagram of the structure of an electronic device 10 that can be used to implement an embodiment of the present invention is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices (such as helmets, glasses, watches, etc.) and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or required herein.

[0173] like Figure 4 As shown, the electronic device 10 includes at least one processor 11, and a memory connected to the at least one processor 11, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., wherein the memory stores a computer program that can be executed by at least one processor, and the processor 11 can perform various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 12 or the computer program loaded from the storage unit 18 to the random access memory (RAM) 13. In the RAM 13, various programs and data required for the operation of the electronic device 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0174] A number of components in the electronic device 10 are connected to the I / O interface 15, including: an input unit 16, such as a keyboard, a mouse, etc.; an output unit 17, such as various types of displays, speakers, etc.; a storage unit 18, such as a disk, an optical disk, etc.; and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0175] The processor 11 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The processor 11 executes the various methods and processes described above, such as a method for online monitoring of capacitance of a capacitor voltage transformer.

[0176] In some embodiments, the online monitoring method for the capacitance of a capacitor voltage transformer may be implemented as a computer program, which is tangibly contained in a computer-readable storage medium, such as a storage unit 18. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 10 via the ROM 12 and / or the communication unit 19. When the computer program is loaded into the RAM 13 and executed by the processor 11, one or more steps of the online monitoring method for the capacitance of a capacitor voltage transformer described above may be performed. Alternatively, in other embodiments, the processor 11 may be configured to perform the online monitoring method for the capacitance of a capacitor voltage transformer by any other appropriate means (e.g., by means of firmware).

[0177] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0178] Computer programs for implementing the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the computer program is executed by the processor, the functions / operations specified in the flow chart and / or block diagram are implemented. The computer program may be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0179] In the context of the present invention, a computer-readable storage medium may be a tangible medium that may contain or store a computer program for use by or in combination with an instruction execution system, device or equipment. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or equipment, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0180] To provide interaction with a user, the systems and techniques described herein may be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and a pointing device (e.g., a mouse or trackball) through which the user can provide input to the electronic device. Other types of devices may also be used to provide interaction with the user; for example, the feedback provided to the user may be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form (including acoustic input, voice input, or tactile input).

[0181] The systems and techniques described herein may be implemented in a computing system that includes backend components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes frontend components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such backend components, middleware components, or frontend components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0182] A computing system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The client and server relationship is generated by computer programs running on the corresponding computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system to solve the defects of difficult management and weak business scalability in traditional physical hosts and VPS services.

[0183] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0184] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for online monitoring of capacitance of a capacitive voltage transformer, characterized in that: include: Continuously obtain the harmonic variation of each harmonic component of the end screen grounding current of the capacitor voltage transformer; Divide the entire domain Θ of the capacitance value range of the capacitive voltage transformer into m intervals [a k , b k ], each of the intervals is a capacitance change; The space (-∞, μ-3σ) and (μ+3σ, +∞) are divided into the interval [a k , b k ]; where μ is the harmonic variation and σ is the standard deviation of Gaussian distribution; Calculating the initial probability of m preset capacitance changes for each harmonic change based on a preset Gaussian distribution probability density function; Using the evidence theory fusion algorithm to fuse the initial probabilities corresponding to the harmonic changes, to obtain the fusion probabilities of the preset m capacitance changes; Acquire the capacitance change corresponding to the maximum fusion probability as the actual change of the capacitive voltage transformer; Wherein, the Gaussian distribution probability density function is: P n (X k ) is the initial probability corresponding to each capacitance change under each harmonic change; n is the nth harmonic component; X k is the kth capacitance change, X1∩X2…X k …∩X m =θ,X k =[a k , b k ], k∈[0, m]; μ is the harmonic variation; σ is the standard deviation of Gaussian distribution; The evidence theory fusion algorithm is as follows: Among them, F(X k ) is the fusion probability corresponding to the kth capacitance change; P n (X k ) is the initial probability corresponding to each of the capacitance changes under each of the harmonic changes; m is the interval range corresponding to the mth capacitance change.

2. The method for online monitoring of capacitance of a capacitive voltage transformer according to claim 1, characterized in that: The method of continuously acquiring the harmonic variation of each harmonic component of the end screen grounding current of the capacitor voltage transformer includes: Continuously obtaining the end-screen grounding current of the capacitive voltage transformer; Performing Fourier transformation on the end-screen grounding current to obtain harmonic components of the end-screen grounding current; The harmonic variation of each harmonic component corresponding to each acquisition time is calculated based on each harmonic component.

3. A device for online monitoring the capacitance of a capacitive voltage transformer, characterized in that: include: An acquisition module, used for continuously acquiring harmonic variation of each harmonic component of the end-screen grounding current of the capacitor voltage transformer; The first calculation module includes: an interval division unit and a probability calculation unit; The interval division unit is used to divide the entire domain Θ of the capacitance value range of the capacitive voltage transformer into m intervals [a k , b k ], each of the intervals is a capacitance change; the space (-∞, μ-3σ) and (μ+3σ, +∞) are respectively divided into an interval [a k , b k ]; where μ is the harmonic variation and σ is the standard deviation of Gaussian distribution; The probability calculation unit is used to calculate the initial probability of the preset m capacitance changes for each harmonic change based on a preset Gaussian distribution probability density function; The second computing module includes a fusion unit and a result acquisition unit; The fusion unit is used to fuse the initial probabilities corresponding to the harmonic changes using an evidence theory fusion algorithm to obtain fusion probabilities of the preset m capacitance changes; The result acquisition unit is used to acquire the capacitance change corresponding to the maximum fusion probability as the actual change of the capacitive voltage transformer; Wherein, the Gaussian distribution probability density function is: P n (X k ) is the initial probability corresponding to each capacitance change under each harmonic change; n is the nth harmonic component; X k is the kth capacitance change, X1∩X2…X k …∩X m =θ,X k =[a k , b k ], k∈[0, m]; μ is the harmonic variation; σ is the standard deviation of Gaussian distribution; The evidence theory fusion algorithm is as follows: Among them, F(X k ) is the fusion probability corresponding to the kth capacitance change; P n (X k ) is the initial probability corresponding to each of the capacitance changes under each of the harmonic changes; m is the interval range corresponding to the mth capacitance change.

4. A capacitive voltage transformer capacitance online monitoring device, characterized in that: The device comprises: at least one processor; and a memory communicatively connected to the at least one processor; wherein, The memory stores a computer program executed by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the online monitoring method for the capacitance of a capacitive voltage transformer according to any one of claims 1-2.

5. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the online monitoring method for the capacitance of a capacitive voltage transformer according to any one of claims 1-2 when executed.

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