A method and device for monitoring aging of a three-core cable based on dynamic dielectric loss

Abstract

The application discloses a kind of based on dynamic dielectric loss three-core cable aging monitoring method and device. Among them, method includes: real-time acquisition ground current and space voltage of two ends of three-core cable;Based on ground current and space voltage, the leakage current monitoring value of three-core cable is calculated;Based on leakage current monitoring value, the first phase angle between leakage current and intermediate phase voltage in three-core cable is determined;Based on the value and variation trend of first phase angle, the dielectric loss of three-core cable is calculated;According to dielectric loss, the aging degree of three-core cable is determined.

Description

Technical Field

[0001] This invention relates to the field of electrical measurement technology, and more specifically, to a method and apparatus for monitoring the aging of three-core cables based on dynamic dielectric loss. Background Technology

[0002] Distribution network cables are numerous and have complex topologies. Under long-term operating conditions, they are susceptible to damage from unexplained external forces, internal water ingress, and other defects, leading to severe aging and significantly threatening safe and stable operation. Therefore, monitoring the insulation condition of distribution network cables is essential, enabling early warning and effectively preventing short-circuit accidents.

[0003] Dielectric loss is a crucial indicator of insulation aging in power equipment. Dielectric loss detection and monitoring of cables can reflect their operational status and guide appropriate operation and maintenance measures. Currently, offline detection is the primary method in engineering projects, using ultra-low frequency dielectric loss detectors to obtain cable dielectric loss values ​​during power outages. However, this method is limited by power outages and cannot promptly detect potential problems and defects.

[0004] There are two main methods for online monitoring of dielectric loss in power equipment: ① Injecting a 0.01Hz low-frequency voltage signal at the high-voltage end and extracting the phase angle difference between the injected voltage signal and the current signal of the same frequency at the grounding point to obtain the dielectric loss; ② Collecting the grounding current, separating the leakage current, and then simultaneously collecting the voltage to calculate the phase difference between the two to obtain the dielectric loss value.

[0005] While existing online monitoring technologies for cable dielectric loss have been proposed, they are still some distance from practical engineering applications. For example, low-frequency signal injection technology at the high-voltage end requires modification of the cable head structure of the distribution cabinet, resulting in complex wiring. Moreover, if the low-frequency signal amplitude is large, it can easily generate harmonics that affect power quality; if the low-frequency signal amplitude is small, the leakage current at the corresponding frequency is very weak and difficult to extract, leading to excessive errors. Due to the complex composition of the grounding current in three-core cables, few related dielectric loss monitoring methods have been proposed to date. Recently, two methods have been proposed: "2024061700510330 An Online Monitoring Device and Method for Aging of Double-Ended Cables" and "2024104219948 A Calculation Method for Abnormal Aging Loss of Insulation Medium of Three-Core Cables Using the Double Current Transformer Method". Both methods use the main current monitoring as the phase reference and do not consider the influence of the power factor angle of the power distribution system. They also do not consider factors such as phase angle mismatch and three-phase uneven dynamic aging, resulting in inaccurate and unrepresentative dynamic dielectric loss monitoring results. The approximate estimation process adopted is complex and overly idealistic, and does not consider the dynamic changes of dielectric loss angle under real conditions. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and device for monitoring the aging of three-core cables based on dynamic dielectric loss.

[0007] According to one aspect of the present invention, a method for monitoring the aging of a three-core cable based on dynamic dielectric loss is provided, comprising:

[0008] Real-time acquisition of grounding current and space voltage at both ends of the three-core cable;

[0009] Calculate the leakage current monitoring value of the three-core cable based on the grounding current and the space voltage;

[0010] Based on the leakage current monitoring value, determine the first phase angle between the leakage current and the intermediate phase voltage of the three-core cable;

[0011] The dielectric loss of the three-core cable is calculated based on the value and trend of the first phase angle.

[0012] The degree of aging of a three-core cable is determined based on dielectric loss.

[0013] Optionally, the grounding current and space voltage at both ends of the three-core cable are collected, including:

[0014] Space voltage is acquired using a D-dot sensor installed on the middle phase of a three-core cable;

[0015] The grounding current is collected by current sensors installed at both ends of the three-core cable.

[0016] Optionally, based on the grounding current and space voltage, the leakage current monitoring value of the three-core cable is calculated, including:

[0017] Perform FFT spectrum analysis on the grounding current to extract the 50Hz power frequency AC component at both ends of the three-core cable;

[0018] Based on the power frequency AC component and the space voltage, calculate the second phase angle and the third phase angle between the grounding current at both ends and the space voltage, respectively.

[0019] The leakage current monitoring value is calculated based on the second phase angle, the third phase angle, and the power frequency AC component.

[0020] Optionally, the vector I of the leakage current monitoring value cx ∠γ x The calculation expression is:

[0021] I cx ∠γ x =I g1 ∠θ1+I g2 ∠θ2

[0022] In the formula, I cx I is the vector sum of the grounding currents at both ends;g1 I g2 θ1 and θ2 are the power frequency AC component amplitudes at both ends of the three-core cable, respectively; θ1 and θ2 are the second and third phase angles at both ends of the three-core cable, respectively; γ x This is the first phase angle.

[0023] Optionally, based on the value and trend of the first phase angle, the dynamic dielectric loss of the three-core cable is calculated, including:

[0024] Calculate the dynamic dielectric loss angle of the three-core cable based on the value and trend of the third phase angle;

[0025] Calculate the dynamic dielectric loss of a three-core cable based on the dynamic dielectric loss angle.

[0026] Optionally, based on the value and trend of the first phase angle, the dynamic dielectric loss of the three-core cable is calculated, including:

[0027] The fourth phase angle is determined based on the value of the first phase angle;

[0028] The dynamic dielectric loss angle is calculated based on the changing trend of the first phase angle and the fourth phase angle.

[0029] Optionally, the fourth phase angle is determined based on the value of the first phase angle, including:

[0030] If γ x If ∈(0,120°), then the fourth phase angle is the first phase angle γ. x ;

[0031] If γ x If ∈(0,-90°), then the fourth phase angle is γ. x +120°;

[0032] If γ x If ∈(150°, 240°), then the fourth phase angle is γ. x -120°.

[0033] Optionally, based on the changing trend of the first phase angle and the fourth phase angle, the dynamic dielectric loss angle is calculated, including:

[0034] If the value of the first phase angle continues to increase, then the dynamic dielectric loss angle Δδ c The fourth phase angle γ x1 -30°;

[0035] If the first phase angle reaches its minimum value and then begins to increase again, then the dynamic dielectric loss angle Δδ c For: △δ c =∠(I cx ∠γ x -I cmin1 ∠γ cmin1 +Icmax1 ∠γ cmax1 -30°, where I cmax1 ∠γ cmax1 I is the leakage current monitoring value corresponding to the first phase angle reaching its maximum. cmin1 ∠γ cmin1 I is the leakage current monitoring value corresponding to the minimum first phase angle. cx ∠γ x This is the current leakage current monitoring value.

[0036] Optionally, the dielectric loss tanδ c The expression is:

[0037]

[0038] In the formula, I0 and δ0 are the leakage current values ​​of the relatively mild aging and their corresponding dielectric loss angles; Δδ c For dynamic dielectric loss angle; I cx The sum of the vector currents at both ends of the grounding circuit is given by , and a and b are fitting parameters.

[0039] According to another aspect of the present invention, a three-core cable aging monitoring device based on dynamic dielectric loss is provided, comprising:

[0040] The acquisition module is used to collect the grounding current and space voltage at both ends of the three-core cable in real time.

[0041] The first calculation module is used to calculate the leakage current monitoring value of the three-core cable based on the grounding current and the space voltage.

[0042] The first determining module is used to determine the first phase angle between the leakage current and the intermediate phase voltage of the three-core cable based on the leakage current monitoring value;

[0043] The second calculation module is used to calculate the dielectric loss of the three-core cable based on the value and trend of the first phase angle.

[0044] The second determining module is used to determine the aging degree of the three-core cable based on the dielectric loss.

[0045] According to another aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing a computer program for performing the methods described in any of the above aspects of the present invention.

[0046] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the preceding aspects of the present invention.

[0047] Therefore, this invention provides a method for dynamic dielectric loss monitoring and calculation of three-core cables based on grounding current and spatial electric field. By monitoring the grounding current at both ends of the three-core cable in the distribution network and the spatial voltage of the intermediate phase at both ends, the change trend of the cable's dielectric loss angle is calculated, thereby obtaining the dynamic dielectric loss and characterizing the aging of the cable. This provides reliable technical support for the safe operation of power cables. Attached Figure Description

[0048] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0049] Figure 1 This is a flowchart illustrating an exemplary embodiment of the present invention for a method of monitoring the aging of a three-core cable based on dynamic dielectric loss.

[0050] Figure 2 This is a schematic diagram of a method for monitoring the grounding current at both ends and the intermediate phase space voltage at both ends of a three-core cable in a distribution network, provided by an exemplary embodiment of the present invention.

[0051] Figure 3 This is a schematic diagram of the equivalent circuit and integration circuit of a D-dot sensor provided in an exemplary embodiment of the present invention;

[0052] Figure 4 This is a schematic diagram illustrating the relationship between the space voltage signal and the phase voltage provided in an exemplary embodiment of the present invention;

[0053] Figure 5 This is a schematic diagram of the leakage current and phase voltage phase angle when the cable aging degree is sorted as edge phase l > middle phase m ≥ edge phase n, according to an exemplary embodiment of the present invention.

[0054] Figure 6 An angle γ is provided in an exemplary embodiment of the present invention. c -30°, △δ cl-n Relationship diagram;

[0055] Figure 7 This is an experimental principle diagram and physical wiring diagram provided by an exemplary embodiment of the present invention;

[0056] Figure 8 This is a schematic diagram of the structure of a three-core cable aging monitoring device based on dynamic dielectric loss provided in an exemplary embodiment of the present invention;

[0057] Figure 9 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. Detailed Implementation

[0058] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0059] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0060] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0061] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0062] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0063] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0064] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0065] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0066] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0067] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0068] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0069] The embodiments of this invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate together with a wide range of other general-purpose or special-purpose computing system environments or configurations. Well-known examples of terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, and servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems, etc.

[0070] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in distributed cloud computing environments, where tasks are executed by remote processing devices linked through communication networks. In distributed cloud computing environments, program modules can reside on local or remote computing system storage media, including storage devices.

[0071] Exemplary methods

[0072] Figure 1 This is a schematic flowchart of an exemplary embodiment of the present invention for a three-core cable aging monitoring method based on dynamic dielectric loss. This embodiment can be applied to electronic devices, such as… Figure 1 As shown, the three-core cable aging monitoring method 100 based on dynamic dielectric loss includes the following steps:

[0073] Step 101: Real-time acquisition of grounding current and space voltage at both ends of the three-core cable;

[0074] Step 102: Calculate the leakage current monitoring value of the three-core cable based on the grounding current and the space voltage;

[0075] Step 103: Based on the leakage current monitoring value, determine the first phase angle between the leakage current and the intermediate phase voltage of the three-core cable;

[0076] Step 104: Calculate the dielectric loss of the three-core cable based on the value and trend of the first phase angle;

[0077] Step 105: Determine the aging degree of the three-core cable based on the dielectric loss.

[0078] Specifically, the technical problem to be solved by the present invention is to overcome the gaps in the prior art and provide a method for dynamic dielectric loss monitoring and calculation of three-core cables based on grounding current and spatial electric field. By monitoring the grounding current at both ends of the three-core cable of the distribution network and the spatial voltage of the intermediate phase at both ends, the change trend of the dielectric loss angle of the cable is calculated, thereby obtaining the dynamic dielectric loss and characterizing the aging of the cable.

[0079] The schematic diagram of the monitoring method is shown below. Figure 2 As shown. The main monitoring locations include the grounding current and space voltage at both ends of the cable. Both parameters are collected simultaneously by a synchronous acquisition device, ensuring that the acquisition time of the two parameters is consistent and that the phase difference can be effectively calculated.

[0080] The space voltage monitoring unit is installed close to the middle phase of the three-phase cable head. The sensor uses electromagnetic induction, employing a D-dot probe and integration reconstruction method to detect the space electric field waveform. (Reference) Figure 3 As shown, the D-dot sensor is a differential capacitive voltage divider. It indirectly measures voltage by measuring the differential components of the spatial electric field E or the electric displacement vector D. Generally, connecting an integrating circuit after the output voltage signal of the D-dot sensor yields a voltage signal linearly proportional to the conductor voltage. The potential of the measured conductor is equivalent to V. i voltage source, C m C is the mutual capacitance between the sensor and the high-voltage conductor. s R is the stray capacitance to ground of the sensor. m For the ground load resistance, the sensor is equivalent to a load resistance of C. m C s and R m This forms the simplest first-order RC circuit. The sensor's output signal V1(t) is input into a passive integrator circuit composed of R1 and C1. The integrator circuit outputs a signal V... o (t) represents the obtained measurement signal, which is a power frequency alternating signal, such as... Figure 4 As shown, since the sensor is located on both sides of the side phases, the space voltage vector U induced on the sensor by the middle phase and the side phases is symmetrical. sv The direction is consistent with the intermediate phase voltage.

[0081] The grounding current and space voltage signals at both ends of the cable under test were obtained by monitoring using the above method, and are denoted as follows: in These are the grounding current and space voltage at one end of the cable under test, respectively. This refers to the grounding current and space voltage at the other end of the cable under test. It is important to note that during actual operation, the orientation of the current sensor must be carefully considered; the grounding current at both ends should be considered positive when it flows from the cable into the ground.

[0082] The synchronous acquisition device performs further FFT spectrum analysis on the above signals, extracts the 50Hz power frequency AC component, and calculates the phase difference angle between the grounding current and space voltage signals at each end, denoted as θ1 and θ2, to obtain two leakage current monitoring value vectors: I g1 ∠θ1、I g2 ∠θ2, because the spatial voltage signal vector direction at both ends of the cable is consistent with the intermediate phase voltage, and the intermediate phase voltages at both ends of the cable are the same, I g1 ∠θ1、I g2 Although ∠θ2 was not monitored at the same time and place, it is comparable in amplitude and phase.

[0083] The grounding current of a power cable consists of two components: induced current and grounding current. The component used to calculate dielectric loss is the leakage current, which includes resistive and capacitive currents. Dielectric loss can be calculated by determining the angle between the leakage current and the phase voltage. The induced current can be canceled out by connecting a current transformer (CT) at both ends to measure the grounding current. Since both ends flow into the ground in a positive reference direction, the induced current can be directly separated using vector addition to obtain the leakage current vector.

[0084] I cx ∠γ x =I g1 ∠θ1+I g2 ∠θ2

[0085] In the formula γ x The leading intermediate phase voltage is taken as positive.

[0086] A three-core cable contains three sub-cables, which will generate three leakage currents, corresponding to three dielectric loss angles, each representing the insulation condition of the main insulation of the cable. Therefore, I cx ∠γ x It is actually the vector sum of three leakage currents, denoted as I. cm ∠δ cm I cn ∠δ cn I cl ∠δ cl Under normal circumstances, due to star-shaped symmetry, I cx ∠γ x Numerically, it should be close to 0. However, in reality, with increased operating time and the occurrence of aging phenomena, the leakage current and dielectric loss angle of the three sub-cables will vary. Inevitably, one cable will be severely aged, and the other will be the least aged. The more severe the aging, the lower the insulation resistance, the higher the dielectric loss, and the larger the equivalent capacitance, resulting in an increase in both leakage current and dielectric loss angle. Assuming the aging degree of the three cables is ranked as follows: edge phase l > middle phase m ≥ edge phase n, the leakage current and phase voltage phase angles might be as follows: Figure 5As shown.

[0087] In the figure This represents the leakage current vector when the aging degree of phase l is consistent with that of phase n. For example... Figure 5 As shown, assuming that edge phase l begins to age first, while edge phase n and middle phase m have not yet begun to age, then γ x The value increases as the aging degree of the edge phase l increases, and satisfies:

[0088]

[0089] Therefore, angle γ can be considered as x -30° characterizes the increase in dielectric loss angle between the severely aged phase and the unaged / lightly aged phases. For △δ cl-n If so Figure 6 As shown:

[0090] Depend on Figure 6 It can be known that △δ cl-n For acute angles less than 90°, then: 0° ≤ γ x <120°.

[0091] Similarly, based on Figure 5 It is not difficult to deduce from the vector diagram that when the middle phase m begins to age and gradually reaches the same aging degree as the edge phase l, γ x It will gradually decrease, and can decrease to a minimum of:

[0092]

[0093] Therefore, since it is impossible to measure the ground current of each phase of a three-core cable in practice, only the sum of the grounding currents can be measured, from which the sum of the leakage currents can be calculated. The leakage current γ... x The trend of change can be used to characterize the increase in dielectric loss angle of the phase with more severe aging, which is called dynamic dielectric loss. Therefore, through the above derivation, the aging state of the cable can be reflected by the dynamic dielectric loss.

[0094] In practice, the magnitude of the dynamic dielectric loss angle can be determined based on its changing trend, as follows:

[0095] (1) Monitor γ according to the above steps x Numerical magnitude: If γ x If ∈(30,120°), then edge phase l ages first; if γ x If ∈(0,-90°), then the middle phase m ages first, γ x Add 120° to the original value; if γ x If ∈(150°,240°), then edge phase n ages first, γ x Reduce the original angle by 120°;

[0096] at this time:

[0097] (1-2) If γ x The continuous increase indicates that the aging of the phase that ages first is accelerating, and the dynamic dielectric loss angle Δδ is calculated. c =γ x -30° characterizes the increase in the cable dielectric loss angle, and tanΔδ is calculated. c Dynamic dielectric loss is obtained;

[0098] (1-3) When Δδ c Reaching a certain peak value Δδ max1 When the current begins to decrease, it indicates that the other two phases are also beginning to age. At this time, the dynamic dielectric loss of the cable is still denoted as tanΔδ. max1 And record the leakage current monitoring value at this time as I. cmax1 ∠γ cmax1 ;

[0099] (1-4) If γ x Reaching a certain minimum value I cmin1 ∠γ cmin1 Then it started to increase again, indicating that the initial aging phase had begun to age again. At this time, an incremental superposition was carried out on the basis of the original maximum dynamic dielectric loss angle, that is:

[0100] △δ c =∠(I cx ∠γ x -I cmin1 ∠γ cmin1 +I cmax1 ∠γ cmax1 -30°

[0101] I cx ∠γ x This is the leakage current monitoring value.

[0102] And so on.

[0103] According to the vector Figure 6 It is not difficult to derive the dielectric loss tanδ after aging. x The mathematical relationship between the dielectric loss angle and leakage current before aging:

[0104]

[0105] Equations I0 and δ0 represent the leakage current values ​​and corresponding dielectric loss angles for lightly aged conditions, equivalent to... Figure 6 In In general, tanδ0 is much less than 1, so the above equation can be simplified to:

[0106]

[0107] Therefore, from the above equation, the tangent of the dielectric loss angle after aging can be obtained through I. cx ∠△δ cx I0∠δ0 is calculated. However, for a three-core cable, I0∠δ0 of a certain phase during actual operation cannot be directly monitored or calculated, and its quantitative relationship with the dynamic change of dielectric loss angle is unknown.

[0108] Therefore, if the monitored cable dielectric loss tanδ x If the trend changes abruptly with the increase in the number of years of operation, the problem can be investigated on-site and guidance provided for operation and maintenance.

[0109] This study employed artificial simulation experiments to obtain a quantitative correlation between the dynamic changes in leakage current and dielectric loss angle during cable aging. A 4-meter-long YJV-8.7 / 15kV cable, identical to those used in actual operation, was selected as the sample. To accelerate aging, the experimental cable was subjected to five times its rated voltage. Each half-hour period of pressure application was recorded as one aging cycle, and ten cycles constituted one round of aging. The leakage current, capacitance, and dielectric loss parameters of the cable were recorded for each round. The experimental schematic and physical wiring diagram are shown below. Figure 7 As shown:

[0110] A single-ended grounding method was used, and the leakage current of the cable was measured using a current transformer. The changes in leakage current were observed using an oscilloscope, and the leakage current data was recorded every fifteen minutes. After one round of aging, the changes in the cable's capacitance and dielectric loss were measured using a digital high-voltage dielectric loss tester.

[0111] This experiment involved 8 aging cycles. To ensure the accuracy of the measurement data, after each aging cycle, a grounding rod was used to discharge the cable and surrounding conductors to prevent residual charge from affecting the experimental results. Then, a digital high-voltage dielectric loss tester was used to measure the dielectric loss, leakage current, and other parameters of the cable under the rated operating voltage, thereby obtaining the quantitative relationship between the dielectric loss and the dynamic changes of leakage current during long-term operation of the cable under rated voltage.

[0112] This experiment involved nine rounds of pressurized aging, and the data records are shown in Table 1.

[0113] Table 1

[0114]

[0115] Since the dielectric loss tangent of cable insulation material is dimensionless and independent of cable size, but depends on the material itself and its aging defects, tanδ0 in equation (2) can be taken as 0.001. However, the basic value of I0 is different under different cable operating conditions, so Δδ is fitted based on test data. cx with I cxThe relationship between / I0 can be obtained as follows:

[0116]

[0117] According to the experimental results, a = 0.0553 and b = 2.935.

[0118] Based on the above method, a one-year monitoring and verification was carried out in the actual field, and the data calculation results are shown in Table 2 below:

[0119] Table 2

[0120]

[0121] The results showed that as the service life of the Zhicheng 1#133 line increased, the dielectric loss tangent value increased significantly, and a phase with a more severe aging condition inside the three-core cable showed signs of accelerated aging, which is consistent with the actual situation. The dielectric loss calculation method for three-core cables proposed in this invention can reflect the aging condition of the cable during operation, and the numerical range of the calculation results is reasonable.

[0122] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0123] Therefore, the aging monitoring method for three-core cables based on dynamic dielectric loss proposed in this invention has the following advantages:

[0124] (1) Improve monitoring accuracy and real-time performance:

[0125] This invention enables real-time monitoring during cable operation, avoiding the limitations of power outage detection and improving the real-time performance and accuracy of monitoring.

[0126] (2) Simplify monitoring devices and operating procedures:

[0127] Using a non-contact method to detect the intermediate phase voltage waveform as a reference phase eliminates the complex steps of taking power from the secondary cabinet to measure the waveform and synchronizing the voltage and current signals with GPS, which are required in traditional methods. This simplifies the structure of the monitoring device and the dielectric loss calculation process, and reduces the difficulty of operation.

[0128] (3) Eliminate the influence of the power factor angle of the power system:

[0129] Using space voltage as the reference phase, compared with using main current as the reference phase, eliminates the influence of the power factor angle of the power system and improves the accuracy of dielectric loss monitoring.

[0130] (4) Adaptable to complex aging conditions of three-core cables:

[0131] This invention takes into account the more complex and general dynamic evolution of uneven aging of three-core cables, and can more accurately reflect the actual aging state of the cable. It is suitable for dynamic assessment of dielectric loss changes in in-service cables.

[0132] (5) Provide dynamic dielectric loss monitoring results:

[0133] By monitoring the dynamic dielectric loss angle, the aging trend of cables can be reflected, helping maintenance personnel to detect aging problems in a timely manner, provide early warnings, prevent short circuit accidents, and improve the safety and stability of the power grid.

[0134] Through the above innovations, monitoring accuracy is improved, operation procedures are simplified, system errors are eliminated, complex aging conditions are adapted, and effective dynamic monitoring results are provided, thus providing reliable technical support for the safe operation of power cables.

[0135] Exemplary device

[0136] Figure 8 This is a schematic diagram of the structure of a three-core cable aging monitoring device based on dynamic dielectric loss provided in an exemplary embodiment of the present invention. Figure 8 As shown, the device 800 includes:

[0137] The acquisition module 810 is used to acquire the grounding current and space voltage at both ends of the three-core cable in real time.

[0138] The first calculation module 820 is used to calculate the leakage current monitoring value of the three-core cable based on the grounding current and the space voltage.

[0139] The first determining module 830 is used to determine the first phase angle between the leakage current and the intermediate phase voltage of the three-core cable based on the leakage current monitoring value;

[0140] The second calculation module 840 is used to calculate the dielectric loss of the three-core cable based on the value and trend of the first phase angle.

[0141] The second determining module 850 is used to determine the aging degree of the three-core cable based on the dielectric loss.

[0142] Optionally, the acquisition module 810 includes:

[0143] The first acquisition submodule is used to acquire space voltage through a D-dot sensor installed on the middle phase of a three-core cable;

[0144] The second acquisition submodule is used to acquire the grounding current through current sensors installed at both ends of the three-core cable.

[0145] Optionally, the first computing module includes:

[0146] The extraction submodule is used to perform FFT spectrum analysis on the grounding current and extract the 50Hz power frequency AC component at both ends of the three-core cable.

[0147] The first calculation submodule is used to calculate the second phase angle and the third phase angle between the grounding current at both ends and the space voltage based on the power frequency AC component and the space voltage, respectively.

[0148] The second calculation submodule is used to calculate the leakage current monitoring value based on the second phase angle, the third phase angle, and the power frequency AC component.

[0149] Optionally, the vector I of the leakage current monitoring value cx ∠γ x The calculation expression is:

[0150] I cx ∠γ x =I g1 ∠θ1+I g2 ∠θ2

[0151] In the formula, I cx I is the vector sum of the grounding currents at both ends; g1 I g2 θ1 and θ2 are the power frequency AC component amplitudes at both ends of the three-core cable, respectively; θ1 and θ2 are the second and third phase angles at both ends of the three-core cable, respectively; γ x This is the first phase angle.

[0152] Optionally, the second computing module 840 includes:

[0153] The third calculation submodule is used to calculate the dynamic dielectric loss angle of the three-core cable based on the value and trend of the third phase angle.

[0154] The fourth calculation submodule is used to calculate the dynamic dielectric loss of the three-core cable based on the dynamic dielectric loss angle.

[0155] Optionally, the third computational submodule includes:

[0156] A determining unit is used to determine the fourth phase angle based on the value of the first phase angle;

[0157] The calculation unit is used to calculate the dynamic dielectric loss angle based on the changing trend of the first phase angle and the fourth phase angle.

[0158] Optionally, the fourth phase angle is determined based on the value of the first phase angle, including:

[0159] If γ x If ∈(0,120°), then the fourth phase angle is the first phase angle γ. x ;

[0160] If γx If ∈(0,-90°), then the fourth phase angle is γ. x +120°;

[0161] If γ x If ∈(150°, 240°), then the fourth phase angle is γ. x -120°.

[0162] Optionally, the computing unit includes:

[0163] If the value of the first phase angle continues to increase, then the dynamic dielectric loss angle Δδ c The fourth phase angle γ x1 -30°;

[0164] If the first phase angle reaches its minimum value and then begins to increase again, then the dynamic dielectric loss angle Δδ c For: △δ c =∠(I cx ∠γ x -I cmin1 ∠γ cmin1 +I cmax1 ∠γ cmax1 -30°, where I cmax1 ∠γ cmax1 I is the leakage current monitoring value corresponding to the first phase angle reaching its maximum. cmin1 ∠γ cmin1 I is the leakage current monitoring value corresponding to the minimum first phase angle. cx ∠γ x This is the current leakage current monitoring value.

[0165] Optionally, the dielectric loss tanδ c The expression is:

[0166]

[0167] In the formula, I0 and δ0 are the leakage current values ​​of the relatively mild aging and their corresponding dielectric loss angles; Δδ c For dynamic dielectric loss angle; I cx The sum of the vector currents at both ends of the grounding circuit is given by , and a and b are fitting parameters.

[0168] Exemplary electronic devices

[0169] Figure 9 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. For example... Figure 9 As shown, the electronic device 90 includes one or more processors 91 and memory 92.

[0170] The processor 91 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0171] The memory 92 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 91 may execute the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above, and / or other desired functions. In one example, the electronic device may also include an input device 93 and an output device 94, these components being interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0172] In addition, the input device 93 may also include, for example, a keyboard, a mouse, etc.

[0173] The output device 94 can output various information to the outside. The output device 94 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0174] Of course, for the sake of simplicity, Figure 9 Only some of the components of this electronic device relevant to the present invention are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0175] Exemplary computer program products and computer-readable storage media

[0176] In addition to the methods and apparatus described above, embodiments of the present invention may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps in the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0177] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of the present invention. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0178] Furthermore, embodiments of the present invention may also be computer-readable storage media storing computer program instructions thereon, which, when executed by a processor, cause the processor to perform the steps of the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0179] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof.

[0180] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0181] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0182] The block diagrams of devices, systems, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, systems, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0183] The methods and systems of the present invention may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of the present invention are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, the present invention may also be implemented as a program recorded on a recording medium, the program comprising machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers recording media storing programs for performing the methods according to the present invention.

[0184] It should also be noted that in the systems, apparatus, and methods of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered equivalents of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0185] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for monitoring the aging of three-core cables based on dynamic dielectric loss, characterized in that, include: Real-time acquisition of grounding current and space voltage at both ends of the three-core cable; Based on the grounding current and the space voltage, calculate the leakage current monitoring value of the three-core cable; Based on the leakage current monitoring value, a first phase angle between the leakage current and the intermediate phase voltage of the three-core cable is determined; Based on the value and trend of the first phase angle, the dielectric loss of the three-core cable is calculated; The degree of aging of the three-core cable is determined based on the dielectric loss, wherein, Based on the grounding current and the space voltage, the leakage current monitoring value of the three-core cable is calculated, including: Perform FFT spectrum analysis on the grounding current to extract the 50Hz power frequency AC component at both ends of the three-core cable; Based on the power frequency AC component and the space voltage, calculate the second phase angle and the third phase angle between the grounding current at both ends and the space voltage, respectively. The leakage current monitoring value is calculated based on the second phase angle, the third phase angle, and the power frequency AC component; The vector I of the leakage current monitoring value cx ∠γ x The calculation expression is: I cx ∠γ x = I g1 ∠θ1 + I g2 ∠θ2 In the formula, I cx I is the vector sum of the grounding currents at both ends. g1 I g2 θ1 and θ2 are the power frequency AC component amplitudes at both ends of the three-core cable, respectively; θ1 and θ2 are the second and third phase angles at both ends of the three-core cable, respectively; γ x This is the first phase angle.

2. The method according to claim 1, characterized in that, Collect the grounding current and space voltage at both ends of the three-core cable, including: The space voltage is acquired by a D-dot sensor installed on the middle phase of the three-core cable; The grounding current is collected by current sensors installed at both ends of the three-core cable.

3. The method according to claim 1, characterized in that, Based on the value and trend of the first phase angle, the dynamic dielectric loss of the three-core cable is calculated, including: The dynamic dielectric loss angle of the three-core cable is calculated based on the value and trend of the first phase angle. The dynamic dielectric loss of the three-core cable is calculated based on the dynamic dielectric loss angle.

4. The method according to claim 3, characterized in that, Based on the value and trend of the first phase angle, the dynamic dielectric loss angle of the three-core cable is calculated, including: The fourth phase angle is determined based on the value of the first phase angle; The dynamic dielectric loss angle is calculated based on the changing trend of the first phase angle and the fourth phase angle.

5. The method according to claim 4, characterized in that, Determining the fourth phase angle based on the value of the first phase angle includes: If γ x If ∈ (0, 120°), then the fourth phase angle is the first phase angle γ. x ; If γ x If ∈ (0, -90°), then the fourth phase angle is γ. x +120°; If γ x If ∈ (150°, 240°), then the fourth phase angle is γ. x -120°.

6. The method according to claim 4, characterized in that, Based on the changing trend of the first phase angle and the fourth phase angle, the dynamic dielectric loss angle is calculated, including: If the value of the first phase angle continues to increase, then the dynamic dielectric loss angle Δδ c The fourth phase angle γ x1 -30°; If the first phase angle reaches its minimum value and then begins to increase again, then the dynamic dielectric loss angle Δδ c For: △δ c = ∠(I cx ∠γ x -I cmin1 ∠γ cmin1 +I cmax1 ∠γ cmax1 -30°, where I cmax1 ∠γ cmax1 I is the leakage current monitoring value corresponding to the first phase angle reaching its maximum. cmin1 ∠γ cmin1 I is the leakage current monitoring value corresponding to the minimum first phase angle. cx ∠γ x This is the current leakage current monitoring value.

7. The method according to claim 3, characterized in that, The dielectric loss tan δ c The expression is: In the formula, I 0 and δ0 are the leakage current values ​​of the relatively lightly aged parameters and their corresponding dielectric loss angles. For dynamic dielectric loss angle; I cx The sum of the vector currents at both ends of the grounding circuit is given by , and a and b are fitting parameters.

8. A three-core cable aging monitoring device based on dynamic dielectric loss, used to implement the method described in any one of claims 1-7, characterized in that, include: The acquisition module is used to collect the grounding current and space voltage at both ends of the three-core cable in real time. The first calculation module is used to calculate the leakage current monitoring value of the three-core cable based on the grounding current and the space voltage. The first determining module is used to determine a first phase angle between the leakage current and the intermediate phase voltage of the three-core cable based on the leakage current monitoring value; The second calculation module is used to calculate the dielectric loss of the three-core cable based on the value and trend of the first phase angle. The second determining module is used to determine the degree of aging of the three-core cable based on the dielectric loss.

9. A computer-readable storage medium, characterized in that, The storage medium stores a computer program for performing the method described in any one of claims 1-7.

10. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method described in any one of claims 1-7.

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