Three-core cable aging monitoring method and device based on dynamic dielectric loss

Abstract

The invention discloses a three-core cable aging monitoring method and device based on dynamic dielectric loss. The method comprises the following steps: collecting grounding current and space voltage at two ends of a three-core cable in real time; calculating a leakage current monitoring value of the three-core cable based on the grounding current and the space voltage; determining 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; calculating the dielectric loss of the three-core cable based on the value and the change trend of the first phase angle; and determining the aging degree of the three-core cable according to the dielectric loss.

Description

Technical Field

[0001] The present invention relates to the field of electrical measurement technology, and more particularly to a three-core cable aging monitoring method and device based on dynamic dielectric loss. Background Art

[0002] Distribution networks are complex and complex, with numerous cables. Over time, they can be subject to damage from unexplained external forces, internal water ingress, and other defects, leading to severe aging and posing a significant threat to safe and stable operation. Insulation condition monitoring of distribution network cables is essential to provide early warning and effectively prevent short-circuit accidents.

[0003] Dielectric loss is a key parameter that indicates insulation aging in power equipment. Testing and monitoring cable dielectric loss can reflect the cable's operating status and guide the implementation of appropriate maintenance measures. Currently, offline testing is the primary method used in projects, using ultra-low-frequency dielectric loss detectors to obtain cable dielectric loss values ​​during power outages. However, this method is subject to power outages and cannot detect potential problems or defects in a timely manner.

[0004] There are two main methods for online monitoring of dielectric loss in power equipment. 1. Inject a 0.01Hz low-frequency voltage signal at the high-voltage end, and extract 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. Collect the grounding current, separate the leakage current, and then collect the voltage at the same time to calculate the phase difference between the two to obtain the dielectric loss value.

[0005] While existing online cable dielectric loss monitoring technologies have been proposed, they are still some distance from practical application. For example, low-frequency signal injection at the high-voltage end requires modifications to the cable head structure of the distribution cabinet, complicating wiring. Furthermore, 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 detect, resulting in large errors. Due to the complex ground current components of three-core cables, relatively few dielectric loss monitoring methods have been proposed. Recently, some people proposed "2024061700510330 A double-end cable aging online monitoring device and online monitoring method" and "A method for calculating the abnormal aging loss of the insulation medium of a three-core cable using a dual mutual inductor method 2024104219948". Both methods use main current monitoring as a phase reference, without considering the influence of the power factor angle of the distribution system; they do not consider factors such as phase angle mismatch and three-phase uneven dynamic aging, resulting in inaccurate and non-representative dynamic dielectric loss monitoring results; the approximate estimation process adopted is complex and too idealized, and does not consider the dynamic changes of the dielectric loss angle under real conditions. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a three-core cable aging monitoring method and device based on dynamic dielectric loss.

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

[0008] Real-time collection of ground 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 ground current and space voltage;

[0010] determining a first phase angle between the leakage current and the middle phase voltage of the three-core cable based on the leakage current monitoring value;

[0011] Based on the value and change trend of the first phase angle, calculate the dielectric loss of the three-core cable;

[0012] Determine the aging degree of three-core cables based on dielectric loss.

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

[0014] The space voltage is collected by a D-dot sensor installed on the middle phase of the three-core cable;

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

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

[0017] Perform FFT spectrum analysis on the ground 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, the second phase angle and the third phase angle between the ground current and the space voltage at both ends are calculated respectively;

[0019] A 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 of the leakage current monitoring value I cx ∠γ x The calculation expression is:

[0021] I cx ∠γ x =I g1 ∠θ1+I g2 ∠θ2

[0022] Where, I cx is the vector sum of the ground currents at both ends; Ig1 , I g2 are the amplitudes of the power frequency AC components at both ends of the three-core cable; θ1 and θ2 are the second phase angle and the third phase angle at both ends of the three-core cable; γ x is the first phase angle.

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

[0027] determining a fourth phase angle according to 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, determining the fourth phase angle according to the value of the first phase angle includes:

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

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

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

[0033] Optionally, calculating the dynamic dielectric loss angle based on the change trend of the first phase angle and the fourth phase angle includes:

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

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

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

[0037]

[0038] Where I0 and δ0 are the leakage current values ​​of the lightly aged parameters and their corresponding dielectric loss angles; Δδ c is the dynamic dielectric loss angle; I cx is the vector sum of the ground currents at both ends, 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] Acquisition module, used to collect the ground current and space voltage at both ends of the three-core cable in real time;

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

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

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

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

[0045] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and the computer program is used to execute the method according to any one of the above aspects of the present invention.

[0046] According to another aspect of the present invention, an electronic device is provided, comprising: a processor; a memory for storing instructions executable by the processor; and the processor for reading the executable instructions from the memory and executing the instructions to implement the method described in any one of the above aspects of the present invention.

[0047] The present invention provides a dynamic dielectric loss monitoring and calculation method for three-core cables based on ground current and spatial electric field. By monitoring the ground current at both ends of a three-core distribution network cable and the mid-phase spatial voltage at both ends, the method calculates the cable's dielectric loss angle variation trend, thereby obtaining dynamic dielectric loss and characterizing cable aging. This provides reliable technical support for the safe operation of power cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0049] Figure 1 1 is a flow chart of a three-core cable aging monitoring method based on dynamic dielectric loss provided by an exemplary embodiment of the present invention;

[0050] Figure 2 Schematic diagram of a method for monitoring the ground current at both ends and the mid-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 Schematic diagram of a D-dot sensor equivalent circuit and an integration circuit provided by an exemplary embodiment of the present invention;

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

[0053] Figure 5 1 is a schematic diagram of the phase angle of leakage current and phase voltage when the cable aging degree is ranked as side phase l> middle phase m≥ side phase n, provided by an exemplary embodiment of the present invention;

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

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

[0056] Figure 8 1 is a schematic structural diagram of a three-core cable aging monitoring device based on dynamic dielectric loss provided by an exemplary embodiment of the present invention; Figure 9 This is a structure of an electronic device provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0057] Below, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0058] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0059] Those skilled in the art will understand that the terms "first" and "second" in the embodiments of the present invention are only used to distinguish different steps, devices or modules, and neither represent any specific technical meaning nor indicate the necessary logical order between them.

[0060] It should also be understood that, in the embodiments of the present invention, “a plurality of” may refer to two or more than two, and “at least one” may refer to one, two or more than two.

[0061] 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 limited or otherwise indicated in the context.

[0062] In addition, the term "and / or" in this invention merely describes an association relationship between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the character " / " in this invention generally indicates that the related objects are in an "or" relationship.

[0063] It should also be understood that the description of the various embodiments of the present invention focuses on the differences between the various embodiments, and the same or similar aspects thereof can be referenced with each other. For the sake of brevity, they will not be described one by one.

[0064] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0065] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0066] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0067] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0068] Embodiments of the present invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate in conjunction with numerous other general-purpose or specialized computing system environments or configurations. Examples of well-known terminal devices, computing systems, environments, and / or configurations suitable for use with terminal devices, computer systems, servers, and other electronic devices 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 personal computers, minicomputer systems, mainframe computer systems, and distributed cloud computing technology environments including any of the above.

[0069] 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. Generally, 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 a distributed cloud computing environment, where tasks are performed by remote processing devices linked via a communication network. In a distributed cloud computing environment, program modules can be located on local or remote computing system storage media, including storage devices.

[0070] Exemplary Methods

[0071] Figure 1 This is a flow chart of a three-core cable aging monitoring method based on dynamic dielectric loss provided by an exemplary embodiment of the present invention. 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:

[0072] Step 101: collecting the ground current and space voltage at both ends of the three-core cable in real time;

[0073] Step 102: Calculate the leakage current monitoring value of the three-core cable based on the ground current and the space voltage;

[0074] Step 103: determining a first phase angle between the leakage current and the middle phase voltage of the three-core cable based on the leakage current monitoring value;

[0075] Step 104, calculating the dielectric loss of the three-core cable based on the value and change trend of the first phase angle;

[0076] Step 105: Determine the aging degree of the three-core cable according to the dielectric loss.

[0077] Specifically, the technical problem to be solved by the present invention is to overcome the gaps in the existing technology and provide a dynamic dielectric loss monitoring and calculation method for 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 intermediate phase spatial voltage at both ends, the dielectric loss angle change trend of the cable is calculated, thereby obtaining the dynamic dielectric loss and characterizing the aging of the cable.

[0078] The monitoring method schematic diagram is as follows Figure 2 The main monitoring locations include the ground current and space voltage at both ends of the cable. These two parameters are collected simultaneously by a synchronous acquisition device, ensuring that the two parameters are collected at the same time and that the phase difference can be effectively calculated.

[0079] The installation position of the space voltage monitoring is close to the middle phase of the three-phase cable head. The sensor uses the electromagnetic induction principle to detect the space electric field waveform through the D-dot probe and the integral reduction method. Figure 3 As shown in the figure, the D-dot sensor is a differential capacitive voltage divider that measures the voltage indirectly by measuring the differential of the spatial electric field E or the electric displacement vector D. Generally, an integration circuit is connected to the output voltage signal of the D-dot sensor to obtain a voltage signal that is linearly proportional to the conductor voltage. The potential of the conductor being measured is equivalent to V i The voltage source, C m is the mutual capacitance between the sensor and the high voltage conductor, C s is the stray capacitance of the sensor to ground, R m is the grounded load resistance, and the sensor is equivalent to C m 、C s and R m The output signal V1(t) of the sensor is input into the passive integration circuit composed of R1 and C1, and the integration circuit outputs the signal V o (t) is the measured signal obtained, which is an alternating power frequency signal, such as Figure 4 As shown, since the side phases on both sides of the sensor are symmetrical, the spatial voltage vector U induced by the middle phase and side phase on the sensor is sv The direction is consistent with the middle phase voltage.

[0080] The ground current and space voltage signals at both ends of the cable under test are monitored by the above method and are recorded as in are the ground current and space voltage at one end of the cable to be tested, = is the ground current and space voltage at the other end of the cable under test. It is important to note that in actual operation, the direction of the current sensor must be paid attention to. The positive direction of the ground current at both ends is when it flows from the cable to the ground.

[0081] The synchronous acquisition device performs further FFT spectrum analysis on the above signal, extracts the 50Hz power frequency AC component, and calculates the phase difference angle between the ground current and space voltage signals at each end, recorded as θ1 and θ2, to obtain two leakage current monitoring value vectors: I g1 ∠θ1、I g2 ∠θ2, since the direction of the space voltage signal vector at both ends of the installed cable is consistent with the intermediate phase voltage, and the intermediate phase voltage at both ends of the cable is the same, I g1 ∠θ1、I g2 Although ∠θ2 is not monitored at the same time and place, it is comparable in amplitude and phase.

[0082] The grounding current of a power cable consists of two components: the induced current and the grounding current. The dielectric loss is calculated using the leakage current component, which includes both resistive and capacitive currents. The dielectric loss can be calculated by calculating the angle between the leakage current component and the phase voltage. Measuring the grounding current using a dual-terminal CT can cancel out the induced current. Since both ends flow into the positive reference direction of the earth, the induced current can be directly separated using vector addition to obtain the leakage current vector:

[0083] I cx ∠γ x =I g1 ∠θ1+I g2 ∠θ2

[0084] Where γ x The leading intermediate phase voltage is positive.

[0085] There are three sub-cables in a three-core cable, which will generate three leakage currents, corresponding to three dielectric loss angles, which respectively characterize the insulation condition of the main insulation of each cable. 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 the star symmetry, I cx ∠γ x The value should be close to 0, but in reality, as the operating time increases and aging occurs, the leakage current and dielectric loss angle of the three sub-cables will vary. There will inevitably be a situation where one cable is severely aged and another is the least aged. The more severe the aging, the lower the insulation resistance, the higher the dielectric loss, and the higher the equivalent capacitance, causing the leakage current and dielectric loss angle to increase. Assuming that the aging degree of the three cables is ranked as side phase l> middle phase m≥ side phase n, the phase angle of the leakage current and phase voltage may be as follows: Figure 5shown.

[0086] In the figure Represents the leakage current vector when the aging degree of side phase l is consistent with that of side phase n. Figure 5 As shown in the figure, assuming that the edge phase l starts to age first, and the edge phase n and the middle phase m have not yet started to age, at this time, γ x The value will increase with the deepening of edge phase l aging, and meet the following conditions:

[0087]

[0088] Therefore, the angle γ can be considered x -30° represents the dielectric loss angle increment of the severely aged phase relative to the unaged / lightly aged phase. is △δ cl-n , then Figure 6 As shown:

[0089] Depend on Figure 6 It can be seen that △δ cl-n For an acute angle less than 90°, then: 0°≤γ x <120°.

[0090] Analogy Figure 5 It is not difficult to deduce from the vector diagram that when the middle phase m begins to age and gradually becomes consistent with the aging degree of the side phase l, γ x It will gradually decrease, and the minimum can be reduced to:

[0091]

[0092] Therefore, in actual situations, it is impossible to measure the ground current of each phase of the three-core cable, so we can only measure the sum of the ground currents, and thus obtain the sum of the leakage currents. x The changing trend can be used to characterize the dielectric loss angle increment of the phase with more serious aging, which is called dynamic dielectric loss. Therefore, through the above derivation, the dynamic dielectric loss can be used to reflect the aging status of the cable.

[0093] In actual implementation, the size of the dynamic dielectric loss angle can be determined based on its changing trend as follows:

[0094] (1) Monitor γ according to the above steps x Value size: If γ x ∈(30,120°), then the edge phase l ages first; if γ x ∈(0,-90°), the middle phase m ages first, γ x Add 120° to the original basis; if γ x ∈(150°,240°), then the edge phase n ages first, γ x Subtract 120° from the original basis;

[0095] at this time:

[0096] (1-2) If γ x Continuous increase indicates that the aging of the first phase is intensifying, and the dynamic dielectric loss angle △δ is calculated. c =γ x -30°, characterizes the increase in the cable dielectric loss angle and calculates tan△δ c Get dynamic dielectric loss;

[0097] (1-3) When △δ c Reach a certain peak △δ max1 It starts to decrease when the other two phases also begin to age. At this time, the dynamic dielectric loss of the cable is still recorded as tan△δ max1 , and record the leakage current monitoring value at this time as I cmax1 ∠γ cmax1 ;

[0098] (1-4) If γ x Reach a minimum value I cmin1 ∠γ cmin1 Then it starts to increase again, indicating that the initial aging phase begins to age again. At this time, the incremental superposition is performed on the basis of the original maximum dynamic dielectric loss angle, that is:

[0099] △δ c =∠(I cx ∠γ x -I cmin1 ∠γ cmin1 +I cmax1 ∠γ cmax1 )-30°

[0100] I cx ∠γ x is the leakage current monitoring value.

[0101] And so on.

[0102] According to the vector Figure 6 It is not difficult to deduce the dielectric loss tanδ after aging x Mathematical relationship between dielectric loss angle and leakage current before aging:

[0103]

[0104] Formula I0 and δ0 are the leakage current values ​​of the lighter aged parameters and their corresponding dielectric loss angle, which are equivalent to Figure 6 in In general, tanδ0 is much smaller than 1, so the above formula can be simplified to:

[0105]

[0106] Therefore, it can be obtained from the above formula that the dielectric loss tangent value after aging can be obtained by I cx ∠△δ cx , I0∠δ0 can be calculated. However, for three-core cables, the I0∠δ0 of a phase during actual operation cannot be directly monitored or calculated, and its quantitative relationship with the dynamic change of the dielectric loss angle is unknown.

[0107] Therefore, if the monitored cable dielectric loss tanδ x If there is a sudden change in the trend as the operating years increase, we can go to the site to investigate the problem and provide guidance on operation and maintenance.

[0108] Through artificial simulation experiments, we can obtain the quantitative correlation between the dynamic changes of leakage current and dielectric loss angle during cable aging. The cable sample is the same as the one used in actual operation. The model is YJV-8.7 / 15kV and its length is 4 meters. In order to accelerate aging, 5 times the rated voltage is applied to the experimental cable. Half an hour of pressure is recorded as one aging cycle. Ten aging cycles are recorded as one aging cycle. The leakage current, capacitance, and dielectric loss parameters of the cable are recorded once in each aging cycle. The experimental principle diagram and the actual wiring diagram are as follows. Figure 7 As shown:

[0109] Single-ended grounding was used, and the cable leakage current was measured using a current transformer. The changes in leakage current were observed using an oscilloscope, with data recorded every fifteen minutes. After each aging cycle, a digital high-voltage dielectric loss meter was used to measure the cable's capacitance and dielectric loss.

[0110] This experiment involves eight rounds of aging. To ensure the accuracy of the measurement data, a ground rod is used to discharge the cable and surrounding conductors after each aging round to prevent residual charge from affecting the experimental results. A digital high-voltage dielectric loss tester is then used to measure the cable's dielectric loss, leakage current and other parameters at the rated operating voltage of the cable. This provides a quantitative relationship between the dynamic changes in the dielectric loss and leakage current of the cable during long-term operation at the rated voltage.

[0111] This experiment was conducted for 9 rounds of pressurized aging, and the data records are shown in Table 1:

[0112] Table 1

[0113]

[0114] Since the dielectric loss tangent of the cable insulation material has no dimension and is independent of the cable size, but is related to the material itself and its aging defects, tanδ0 in formula (2) can be taken as 0.001. However, the basic value of I0 is different under different cable operating conditions, so △δ is fitted based on the test data. cx with I cxThe relationship between / I0 can be obtained:

[0115]

[0116] According to the test results, a=0.0553 and b=2.935.

[0117] Based on the above method, a one-year monitoring verification was carried out on site, and the data calculation results are shown in Table 2 below:

[0118] Table 2

[0119]

[0120] The results show that the dielectric loss tangent of Zhicheng 1#133 line increases significantly with the increase in service life. A phase with a more severe degree of aging within the three-core cable shows signs of accelerated aging, which is consistent with the actual situation. The three-core cable dielectric loss calculation method proposed in this invention can reflect the aging of the cable in operation, and the numerical range of the calculation results is reasonable.

[0121] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0122] Therefore, the present invention proposes a three-core cable aging monitoring method based on dynamic dielectric loss, which has the following advantages:

[0123] (1) Improve monitoring accuracy and real-time performance:

[0124] The present invention can monitor the operation of the cable in real time, avoids the limitation of power failure detection, and improves the real-time performance and accuracy of monitoring.

[0125] (2) Simplify monitoring equipment and operating procedures:

[0126] The non-contact detection of the intermediate phase voltage waveform is used as the reference phase, eliminating the complex steps of measuring the waveform and GPS timing of the voltage and current signals in the secondary cabinet in the traditional method, simplifying the structure of the monitoring device and the dielectric loss calculation process, and reducing the difficulty of operation.

[0127] (3) Eliminate the influence of power factor angle of power system:

[0128] Compared with the method of using the main current as the reference phase, the method of using the space voltage as the reference phase eliminates the influence of the power factor angle of the power system and improves the accuracy of dielectric loss monitoring.

[0129] (4) Adapt to complex three-core cable aging conditions:

[0130] The present invention takes into account the more complex and common dynamic evolution of uneven aging of three-core cables, can more accurately reflect the actual aging state of the cables, and is suitable for the dynamic evaluation of dielectric loss changes of in-service cables.

[0131] (5) Provide dynamic dielectric loss monitoring results:

[0132] By monitoring the dynamic dielectric loss angle, the aging trend of the cable can be reflected, helping operation and maintenance personnel to promptly detect cable aging problems, provide early warnings, prevent short-circuit accidents, and improve the safety and stability of the power grid.

[0133] Through the above innovations, the monitoring accuracy is improved, the operation process is simplified, the system error is eliminated, the system adapts to complex aging conditions and provides effective dynamic monitoring results, thus providing reliable technical support for the safe operation of power cables.

[0134] Exemplary devices

[0135] Figure 8 FIG is a schematic diagram of a three-core cable aging monitoring device based on dynamic dielectric loss according to an exemplary embodiment of the present invention. Figure 8 As shown, the apparatus 800 includes:

[0136] The acquisition module 810 is used to collect the ground current and space voltage at both ends of the three-core cable in real time;

[0137] A first calculation module 820 is configured to calculate a leakage current monitoring value of the three-core cable based on the ground current and the space voltage;

[0138] A first determining module 830 is configured to determine a first phase angle between the leakage current and the middle phase voltage of the three-core cable based on the leakage current monitoring value;

[0139] A second calculation module 840 is configured to calculate the dielectric loss of the three-core cable based on the value and change trend of the first phase angle;

[0140] The second determining module 850 is configured to determine the aging degree of the three-core cable according to the dielectric loss.

[0141] Optionally, the acquisition module 810 includes:

[0142] The first acquisition submodule is used to collect space voltage through a D-dot sensor installed on the middle phase of the three-core cable;

[0143] The second acquisition submodule is used to collect the ground current through current sensors installed at both ends of the three-core cable.

[0144] Optionally, the first computing module includes:

[0145] The extraction submodule is used to perform FFT spectrum analysis on the ground current and extract the 50Hz power frequency AC component at both ends of the three-core cable;

[0146] A first calculation submodule is used to calculate a second phase angle and a third phase angle between the ground current and the space voltage at both ends based on the power frequency AC component and the space voltage;

[0147] 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.

[0148] Optionally, the vector of the leakage current monitoring value I cx ∠γ x The calculation expression is:

[0149] I cx ∠γ x =I g1 ∠θ1+I g2 ∠θ2

[0150] Where, I cx is the vector sum of the ground currents at both ends; I g1 , I g2 are the amplitudes of the power frequency AC components at both ends of the three-core cable; θ1 and θ2 are the second phase angle and the third phase angle at both ends of the three-core cable; γ x is the first phase angle.

[0151] Optionally, the second calculation module 840 includes:

[0152] A third calculation submodule is used to calculate the dynamic dielectric loss angle of the three-core cable according to the value and change trend of the third phase angle;

[0153] The fourth calculation submodule is used to calculate the dynamic dielectric loss of the three-core cable according to the dynamic dielectric loss angle.

[0154] Optionally, the third computing submodule includes:

[0155] a determining unit, configured to determine a fourth phase angle according to a value of the first phase angle;

[0156] The calculation unit is used to calculate the dynamic dielectric loss angle based on the change trend of the first phase angle and the fourth phase angle.

[0157] Optionally, determining the fourth phase angle according to the value of the first phase angle includes:

[0158] If γ x ∈(0,120°), then the fourth phase angle is the first phase angle γ x ;

[0159] If γx ∈(0,-90°), then the fourth phase angle is γ x +120°;

[0160] If γ x ∈(150°,240°), then the fourth phase angle is γ x -120°.

[0161] Optionally, the computing unit includes:

[0162] If the value of the first phase angle continues to increase, the dynamic dielectric loss angle △δ c is the fourth phase angle γ x1 -30°;

[0163] If the first phase angle reaches the minimum value and then starts to increase, the dynamic dielectric loss angle △δ c =△δ c =∠(I cx ∠γ x -I cmin1 ∠γ cmin1 +I cmax1 ∠γ cmax1 )-30°, where I cmax1 ∠γ cmax1 is the leakage current monitoring value corresponding to the first phase angle reaching the maximum, I cmin1 ∠γ cmin1 is the leakage current monitoring value corresponding to the first phase angle reaching the minimum, I cx ∠γ x is the current leakage current monitoring value.

[0164] Optionally, dielectric loss tanδ c The expression is:

[0165]

[0166] Where I0 and δ0 are the leakage current values ​​of the lightly aged parameters and their corresponding dielectric loss angles; Δδ c is the dynamic dielectric loss angle; I cx is the vector sum of the ground currents at both ends, and a and b are fitting parameters.

[0167] Exemplary electronic devices

[0168] Figure 9 This is the structure of an electronic device provided by an exemplary embodiment of the present invention. Figure 9 As shown, the electronic device 90 includes one or more processors 91 and a memory 92 .

[0169] The processor 91 may be a central processing unit (CPU) or other forms of processing units having data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0170] 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, for example, include random access memory (RAM) and / or cache memory (cache), etc. The non-volatile memory may, for example, include read-only memory (ROM), a hard disk, a 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 further include: an input device 93 and an output device 94, which are interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0171] In addition, the input device 93 may also include, for example, a keyboard, a mouse, and the like.

[0172] The output device 94 can output various information to the outside. The output device 94 can include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto.

[0173] Of course, to simplify, Figure 9 Only some of the components related to the present invention in the electronic device are shown, and components such as a bus, an input / output interface, etc. are omitted. In addition, the electronic device may further include any other appropriate components according to specific application conditions.

[0174] Exemplary computer program products and computer-readable storage media

[0175] In addition to the above-mentioned methods and devices, an embodiment of the present invention may also be a computer program product, which includes computer program instructions, which, when executed by a processor, enable the processor to perform the steps of the method according to various embodiments of the present invention described in the above "Exemplary Method" section of this specification.

[0176] The computer program product may be written in any combination of one or more programming languages ​​to implement the operations of embodiments of the present invention, including object-oriented programming languages ​​such as Java, C++, and conventional procedural programming languages ​​such as C or similar programming languages. The program code may be executed entirely on the user's computing device, partially on the user's computing device, as a stand-alone 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.

[0177] In addition, an embodiment of the present invention may also be a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, enable the processor to execute the steps of the method according to various embodiments of the present invention described in the above "Exemplary Method" section of this specification.

[0178] The computer-readable storage medium can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium can, for example, include but is not limited to a system, system or device of electricity, magnetism, light, electromagnetic, infrared, or semiconductor, or any combination thereof. More specific examples (non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable 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 thereof.

[0179] The basic principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in the present invention are merely illustrative and non-limiting, and should not be construed as necessarily possessed by each embodiment of the present invention. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, and are not intended to be limiting. These details do not necessarily limit the present invention to being implemented using these specific details.

[0180] Each embodiment in this specification is described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. References to the same or similar parts between the various embodiments are sufficient. For system embodiments, since they largely correspond to method embodiments, their description is relatively simple. For relevant parts, references to the description of the method embodiments are sufficient.

[0181] The block diagrams of the devices, systems, equipment, and systems involved in the present 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 will be appreciated by those skilled in the art, these devices, systems, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "including," "comprising," "having," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0182] The method and system of the present invention may be implemented in many ways. For example, the method and system of the present invention may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above sequence of steps for the method is for illustration only, and the steps of the method of the present invention are not limited to the sequence specifically described above, unless otherwise specified. In addition, in some embodiments, the present invention may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method according to the present invention. Thus, the present invention also covers recording media that store programs for executing the method according to the present invention.

[0183] It should also be noted that, in the system, device and method of the present invention, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent schemes of the present invention. The above description of the disclosed aspects is provided to enable any technician in this field to make or use the present invention. Various modifications to these aspects will be very obvious to those skilled in the art, and the general principles defined here can be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the aspects shown here, but according to the widest scope consistent with the principles disclosed here and novel features.

[0184] The above description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example 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 three-core cable aging monitoring method based on dynamic dielectric loss, characterized in that: include: Real-time collection of ground current and space voltage at both ends of the three-core cable; Calculating a leakage current monitoring value of the three-core cable based on the ground current and the space voltage; Determining a first phase angle between the leakage current and the middle phase voltage of the three-core cable based on the leakage current monitoring value; Calculating the dielectric loss of the three-core cable based on the value and change trend of the first phase angle; The aging degree of the three-core cable is determined according to the dielectric loss.

2. The method according to claim 1, characterized in that Collect the ground current and space voltage at both ends of the three-core cable, including: collecting the space voltage 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 Calculating a leakage current monitoring value of the three-core cable based on the ground current and the space voltage includes: Performing FFT spectrum analysis on the ground current to extract 50 Hz power frequency AC components at both ends of the three-core cable; Based on the power frequency AC component and the space voltage, respectively calculating a second phase angle and a third phase angle between the ground current at both ends and the space voltage; The leakage current monitoring value is calculated based on the second phase angle, the third phase angle, and the power frequency AC component.

4. The method according to claim 3, characterized in that 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 Where, I cx is the vector sum of the ground currents at both ends; I g1 , I g2 are the amplitudes of the power frequency AC components at both ends of the three-core cable; θ1 and θ2 are the second phase angle and the third phase angle at both ends of the three-core cable; γ x is the first phase angle.

5. The method according to claim 1, wherein Calculating the dynamic dielectric loss of the three-core cable based on the value and change trend of the first phase angle includes: Calculating the dynamic dielectric loss angle of the three-core cable according to the value and change trend of the first phase angle; The dynamic dielectric loss of the three-core cable is calculated according to the dynamic dielectric loss angle.

6. The method according to claim 5, characterized in that Calculating the dynamic dielectric loss angle of the three-core cable according to the value and change trend of the first phase angle includes: determining a fourth phase angle according to the value of the first phase angle; The dynamic dielectric loss angle is calculated based on the change trend of the first phase angle and the fourth phase angle.

7. The method according to claim 6, characterized in that Determining a fourth phase angle according to a value of the first phase angle includes: If γ x ∈(0,120°), then the fourth phase angle is the first phase angle γ x ; If γ x ∈(0,-90°), then the fourth phase angle is γ x +120°; If γ x ∈(150°,240°), then the fourth phase angle is γ x -120°.

8. The method according to claim 6, characterized in that Calculating the dynamic dielectric loss angle based on the changing trend of the first phase angle and the fourth phase angle includes: If the value of the first phase angle continues to increase, the dynamic dielectric loss angle Δδ c is the fourth phase angle γ x1 -30°; If the first phase angle reaches the minimum value and then starts to increase, the dynamic dielectric loss angle Δδ c =△δ c =∠(I cx ∠γ x -I cmin1 ∠γ cmin1 +I cmax1 ∠γ cmax1 )-30°, where I cmax1 ∠γ cmax1 is the leakage current monitoring value corresponding to the first phase angle reaching the maximum, I cmin1 ∠γ cmin1 is the leakage current monitoring value corresponding to the first phase angle reaching the minimum, I cx ∠γ x is the current leakage current monitoring value.

9. The method according to claim 5, characterized in that The dielectric loss tan δ c The expression is: Where I0 and δ0 are the leakage current values ​​of the lightly aged parameters and their corresponding dielectric loss angles; Δδ c is the dynamic dielectric loss angle; I cx is the vector sum of the ground currents at both ends, and a and b are fitting parameters.

10. A three-core cable aging monitoring device based on dynamic dielectric loss, characterized in that: include: Acquisition module, used to collect the ground current and space voltage at both ends of the three-core cable in real time; A first calculation module is used to calculate a leakage current monitoring value of the three-core cable based on the ground current and the space voltage; A first determining module is configured to determine a first phase angle between the leakage current and the middle phase voltage of the three-core cable based on the leakage current monitoring value; A second calculation module, configured to calculate the dielectric loss of the three-core cable based on the value and change trend of the first phase angle; The second determining module is configured to determine the aging degree of the three-core cable according to the dielectric loss.

11. A computer-readable storage medium, characterized in that The storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 9.

12. An electronic device, characterized in that: The electronic device comprises: processor; a memory for storing instructions executable by the processor; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any one of claims 1 to 9.

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