Capacitor bank circuit breaker contact degradation monitoring method and system

Abstract

The invention discloses a method for monitoring degradation of a capacitor bank circuit breaker contact. The method comprises the following steps: acquiring a fracture voltage signal and a closing current signal; analyzing and processing the fracture voltage signal, and extracting pre-breakdown time; counting a current peak value of the current signal, constructing a pre-breakdown current sequence, and determining a degradation index; determining a current discrete sequence according to the closing current signal, constructing a current time sequence function, and determining an average offset degree; and comparing the pre-breakdown time, the degradation index and the average deviation degree with corresponding preset threshold ranges, and when any two items do not accord with each other, determining that the contact of the circuit breaker is degraded. The invention also discloses a monitoring system for the degradation of the capacitor bank circuit breaker contact. The method has the beneficial effects that the operation is convenient, the principle is intuitive and easy to understand, the potential contact degradation problem can be quickly identified and pre-warned, the contact degradation condition of the circuit breaker is monitored on line, the risk of failure of the circuit breaker caused by contact degradation is reduced, and the overall operation stability and safety of a power grid are improved.

Description

Technical Field

[0001] This invention relates to the field of online testing technology for electrical equipment in power systems, and more specifically, to a method and system for monitoring the deterioration of contacts in capacitor bank circuit breakers. Background Technology

[0002] Due to the intermittent and fluctuating nature of renewable energy generation, capacitor bank reactive power compensation devices are widely used to regulate reactive power, thereby improving the stability and capacity of the power grid. However, capacitor bank circuit breakers, due to frequent switching and the impact of high-frequency, high-amplitude inrush currents on closing capacitive loads, experience contact erosion and deterioration, leading to a decrease in circuit breaker breaking capacity and increasing the safety risks of system operation. Currently, research on monitoring contact deterioration lacks dedicated online monitoring technology, and a practical assessment scheme for field deployment has not yet been developed. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a method and system for monitoring the deterioration of capacitor bank circuit breaker contacts.

[0004] This invention provides a method for monitoring the deterioration of contacts in a capacitor bank circuit breaker, the method comprising:

[0005] Collect the break voltage signal and closing current signal generated when the circuit breaker is closed;

[0006] The break voltage signal is analyzed and processed to extract the pre-breakdown time;

[0007] The peak current of the closing current signal during the pre-breakdown stage in multiple closing operations is statistically analyzed, and a pre-breakdown current sequence is constructed. The degradation index of the pre-breakdown current sequence is determined based on the pre-breakdown current sequence.

[0008] The current discrete sequence of the steady-state arcing stage is determined based on the closing current signal, and a current time series function is constructed. The average deviation of the current change rate is determined by analyzing and processing the current time series function.

[0009] The pre-breakdown time, the degradation index, and the average offset are compared with the corresponding preset threshold ranges. If any two of them do not meet the corresponding preset threshold ranges, the contacts of the circuit breaker are determined to be degraded and an early warning is triggered.

[0010] As a further improvement of the present invention, a set of voltage sensors and a set of current sensors are respectively installed on both sides of the circuit breaker's break point, and the break point voltage and the closing current are collected through the voltage sensors and the current sensors.

[0011] As a further improvement of the present invention, the sampling frequency for obtaining the closing current is greater than or equal to 100kHz.

[0012] As a further improvement of the present invention, the analysis and processing of the break voltage and the extraction of the pre-breakdown time include:

[0013] Wavelet transform is used to extract transient features from the break voltage signal during the pre-breakdown stage;

[0014] The voltage drop moment of the voltage signal at the break point is detected and located as the breakdown start moment, and the waveform step rise moment is the termination moment when the contacts are fully in contact.

[0015] The pre-breakdown time is obtained based on the breakdown start time and the termination time of complete contact of the contacts.

[0016] As a further improvement of the present invention, comparing the pre-breakdown time with the corresponding preset threshold range includes:

[0017] The mean value μ of the pre-breakdown time is determined based on the pre-breakdown time. T and standard deviation σ T ;

[0018] In μ T ≥1.5μ0 or σ T When ≥5σ0, the pre-breakdown time is not within the preset threshold range, and it is determined that the warning level has been reached;

[0019] Where μ0 and σ0 are the mean μ0 and standard deviation σ0 of the standard pre-breakdown time of the circuit breaker.

[0020] As a further improvement of the present invention, comparing the degradation index with the corresponding preset threshold range includes:

[0021] At 0.8≤DSI-I d When the value is less than 1, the degradation index is not within the preset threshold range, and the warning level is determined to be reached.

[0022] Among them, DSI-I d The degradation index is mentioned above.

[0023] As a further improvement of the present invention, comparing the average offset with the corresponding preset threshold range includes:

[0024] When 0.06 ≤ v ≤ 0.08, the average offset is not within the preset threshold range, and the warning level is determined to be reached;

[0025] Where v is the average offset.

[0026] The present invention also provides a monitoring system for the deterioration of contacts in a capacitor bank circuit breaker, the monitoring system comprising:

[0027] An integrated sensing module, including a voltage sensor and a current sensor, is used to acquire the break voltage signal and closing current signal generated when the circuit breaker is closed.

[0028] The host computer is communicatively connected to the integrated sensing module.

[0029] Receive the disconnection voltage signal and the closing current signal;

[0030] The break voltage signal is analyzed and processed to extract the pre-breakdown time;

[0031] The peak current of the closing current signal during the pre-breakdown stage in multiple closing operations is statistically analyzed, and a pre-breakdown current sequence is constructed. The degradation index of the pre-breakdown current sequence is determined based on the pre-breakdown current sequence.

[0032] The current discrete sequence of the steady-state arcing stage is determined based on the closing current signal, and a current time series function is constructed. The average deviation of the current change rate is determined by analyzing and processing the current time series function.

[0033] The pre-breakdown time, the degradation index, and the average offset are compared with the corresponding preset threshold ranges. If any two of them do not meet the corresponding preset threshold ranges, the contacts of the circuit breaker are determined to be degraded and an early warning is triggered.

[0034] As a further improvement of the present invention, the monitoring system also includes a GPS synchronization and time synchronization module to correct and synchronize the time of the entire monitoring system in real time.

[0035] As a further improvement of the present invention, the integrated sensing module further includes a wireless communication unit, which is communicatively connected to the host computer.

[0036] The beneficial effects of this invention are as follows: by collecting the break voltage signal and closing current signal generated when the circuit breaker is closed, and using the dynamic change pattern of these two signals as the basis for judgment, it is not only convenient to operate and intuitive to understand, but also can quickly identify and warn of potential contact deterioration problems, realize online monitoring of the contact deterioration of the circuit breaker, reduce the risk of circuit breaker failure due to contact deterioration, and improve the overall operational stability and safety of the power grid. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1A schematic diagram showing the changes in the erosion morphology of circuit breaker contacts;

[0039] Figure 2 To improve the three-segment arc resistance model;

[0040] Figure 3 This is a measured current signal collected during a capacitor bank circuit breaker closing operation.

[0041] Figure 4 This is a summary flowchart of a method for monitoring the deterioration of contacts in a capacitor bank circuit breaker according to an exemplary embodiment of the present invention.

[0042] Figure 5 This is a waveform diagram showing the 1-6 layer wavelet function decomposition results of the contact deterioration monitoring method for capacitor bank circuit breakers according to an exemplary embodiment of the present invention.

[0043] Figure 6 This is a diagram illustrating the dynamic variation characteristics of arc breakdown current in a method for monitoring contact deterioration of a capacitor bank circuit breaker according to an exemplary embodiment of the present invention.

[0044] Figure 7 This is a diagram showing the trend of closing current changes under different contact erosion states in a monitoring method for contact deterioration of a capacitor bank circuit breaker according to an exemplary embodiment of the present invention.

[0045] Figure 8 This is a diagram showing the pre-breakdown time distribution characteristics of different contact deterioration states in a monitoring method for contact deterioration of a capacitor bank circuit breaker according to an exemplary embodiment of the present invention.

[0046] Figure 9 This is a detailed flowchart of a method for monitoring the deterioration of contacts in a capacitor bank circuit breaker according to an exemplary embodiment of the present invention.

[0047] Figure 10 This is a schematic diagram of the structure of a monitoring system for the deterioration of contacts of a capacitor bank circuit breaker according to an exemplary embodiment of the present invention;

[0048] Figure 11 This is a diagram of the host computer user interface in a monitoring system for contact deterioration of a capacitor bank circuit breaker, as described in an exemplary embodiment of the present invention. Detailed Implementation

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

[0050] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0051] Furthermore, the terminology used in the description of this invention is for illustrative purposes only and is not intended to limit the scope of the invention. The terms "comprising" and / or "including" are used to specify the presence of said elements, steps, operations, and / or components, but do not exclude the presence or addition of one or more other elements, steps, operations, and / or components. The terms "first," "second," etc., may be used to describe various elements, do not represent an order, and do not limit these elements. Moreover, in the description of this invention, unless otherwise stated, "a plurality of" means two or more. These terms are used only to distinguish one element from another. These and / or other aspects become apparent in conjunction with the following drawings, and those skilled in the art will more readily understand the description of the embodiments of the invention. The drawings are used for illustrative purposes only to depict the embodiments of the invention. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods shown in the invention can be employed without departing from the principles of the invention.

[0052] like Figure 1 As shown, after ablation, the contacts exhibit two main geometrical changes: First, the tip of the stationary contact gradually sharpens due to continuous material loss, significantly shortening its effective contact stroke during engagement and disengagement. Second, a distinct irregular uneven structure forms on the contact surface, affecting the stability of the electric field distribution and arc conduction path between the contacts. These morphological changes lead to a longer pre-breakdown time, making the changes in the rise edge of the pre-breakdown current and the evolution of the steady-state arcing process key characteristics reflecting the degree of contact degradation.

[0053] like Figure 2 and Figure 3 As shown, an improved three-segment arc resistance model is used to describe the entire process of pre-breakdown arcing during circuit breaker closing. The process of the arc current rising from its initial value to its peak value is defined as the pre-breakdown stage, the process of the current decreasing from its peak value to its first zero crossing is defined as the unstable breakdown stage, and the moment when the current first crosses zero is considered the starting point of the steady-state arcing stage. Taking the measured current signal collected during a capacitor bank branch closing operation as an example, the division of each stage is illustrated. In the figure, t0, t1, and t2 are the breakdown start time (arc initiation time), the end time of the pre-breakdown stage, and the start time of the steady-state arcing stage, respectively, while t3 to t4 represent the arc entering the extinction stage.

[0054] like Figure 4 As shown in the embodiment of the present invention, a method for monitoring the deterioration of capacitor bank circuit breaker contacts includes:

[0055] Collect the break voltage signal u(t) and closing current signal i(t) generated when the circuit breaker is closed;

[0056] A voltage sensor and a current sensor are respectively installed on both sides of the circuit breaker's break point. The voltage sensor and the current sensor collect the break point voltage ΔU and the closing current I. L .

[0057] The current information on both sides of the circuit breaker's break point belongs to the same branch, so one side of the current line can be selected for calculation. The break point voltage ΔU is calculated by subtracting the voltage measurements on both sides.

[0058] Furthermore, the sampling frequency of the closing current is greater than or equal to 100kHz. This ensures accurate capture of transient current changes at the millisecond or even microsecond level during critical periods such as the pre-breakdown stage and steady-state arcing stage during the closing process, avoiding the loss of feature information, guaranteeing calculation accuracy, and providing crucial support for the reliability and sensitivity of the entire monitoring method.

[0059] The voltage signal at the break point is analyzed and processed to extract the pre-breakdown time.

[0060] When pre-breakdown occurs, the voltage across the circuit breaker contacts is measured by voltage sensors placed on both sides of the circuit breaker contact, and the difference is calculated to obtain the break-point voltage ΔU. The break-point voltage ΔU drops sharply from the system voltage level to the arc sustaining voltage range of 100V-500V. After the moving and stationary contacts complete physical contact, the break-point voltage ΔU experiences a slight step increase, then decays and stabilizes at a near-zero low level (<50V). Based on these voltage response characteristics, the breakdown initiation time and the termination time of complete contact can be determined by identifying two key abrupt changes in the break-point voltage waveform, thus enabling the estimation of pre-breakdown time.

[0061] Furthermore, the analysis and processing of the break voltage to extract the pre-breakdown time includes:

[0062] Wavelet transform is used to extract transient features from the break voltage signal during the pre-breakdown stage;

[0063] Wavelet transform has excellent time-frequency localization capabilities, and is especially suitable for processing non-stationary and abrupt signals. It can be used to identify transient fluctuations at breakdown points and contact points.

[0064] The voltage drop moment of the voltage signal at the break point is detected and located as the breakdown start moment, and the waveform step rise moment is the termination moment when the contacts are fully in contact.

[0065] The pre-breakdown time is obtained based on the breakdown start time and the termination time of complete contact of the contacts.

[0066] The break voltage signal is u(t), and its continuous wavelet transform (CWT) is defined as:

[0067]

[0068] Where W(a,b) are the transform coefficients under scaling factor a and shift factor b, and ψ(t) is the mother wavelet function. It indicates its complex conjugate form.

[0069] In practical engineering, Discrete Wavelet Transform (DWT) is more commonly used for digital signal processing, where the j-th level detail coefficients d j (k) can be expressed as:

[0070]

[0071] Where u(n) is the value of the original signal at the nth position, g(n) is the high-pass filter coefficient corresponding to the mother wavelet function, j represents the wavelet transform level, k represents the nth data point in that level, and d j (k) reflects the high-frequency or abrupt changes in the signal.

[0072] like Figure 5 As shown, discrete wavelet decomposition was performed on the voltage signal at the break point collected in a certain pre-breakdown test to obtain decomposition results of 1 to 6 levels. The results show that the detail coefficients of the 4th to 6th levels are more obvious in identifying the peak characteristics of the arc breakdown point and the contact point of the contact. In engineering applications, the approximate time period of arc activity can be initially determined based on the sudden change range of the break voltage, and then the break voltage signal within the range of the time period can be processed by wavelet decomposition of 4 to 6 levels. Subsequently, the first difference of the detail coefficients is calculated by Equation (3) to identify the local extreme points with significant upward or downward trends, thereby realizing the location of the arc start and end time, and calculating the pre-breakdown time Δd accordingly. j [k].

[0073] Δd j [k]=d j [k+1]-d j [k] (3)

[0074] Comparing the pre-breakdown time with the corresponding preset threshold range includes:

[0075] The mean value μ of the pre-breakdown time is determined based on the pre-breakdown time. T and standard deviation σ T ;

[0076] In μ T≥1.5μ0 or σ T When ≥5σ0, the pre-breakdown time is not within the preset threshold range, and it is determined that the warning level has been reached;

[0077] Where μ0 and σ0 are the mean μ0 and standard deviation σ0 of the standard pre-breakdown time of the circuit breaker.

[0078] like Figure 8 As shown, the probability density distribution of pre-breakdown time T in 40 closing pre-breakdown tests of the same circuit breaker under ideal and degraded conditions is illustrated. The results show that in the initial operating stage of the circuit breaker, the distribution of pre-breakdown time T is relatively concentrated, exhibiting small dispersion and a stable normal distribution. However, after contact erosion and deterioration, the mean of pre-breakdown time T increases significantly, and the distribution tends to be right-skewed, exhibiting a long-tailed distribution characteristic. To assess the health status of the circuit breaker contacts, the mean μ of pre-breakdown time T is... T and standard deviation σ T As a characteristic quantity for condition monitoring.

[0079]

[0080] Where n is the number of samples in the statistics, and T (i) Let μ be the pre-breakdown time corresponding to the i-th closing operation. T Let σ be the mean of the pre-breakdown times after n closing cycles, representing the central tendency of the pre-breakdown time distribution. T Let be the standard deviation of the pre-breakdown time after n closing cycles, representing the degree of fluctuation in the pre-breakdown time distribution.

[0081] Specifically, in practical engineering applications, after each new pre-breakdown time is measured, its statistical characteristics can be dynamically calculated using a sliding window method, combining the data from the most recent closing tests: the mean μ0 and standard deviation σ0 of the standard pre-breakdown time of the circuit breaker are obtained based on the pre-breakdown test conducted at the circuit breaker's factory. When the μ0 calculated within the sliding window... T Exceeding 1.5 times the standard pre-breakdown time mean μ0 and / or σ T When the standard deviation of the pre-breakdown time exceeds 5 times (i.e., μ) T ≥1.5μ0 or σ T If the value is ≥5σ0, then it is considered to have reached the warning level.

[0082] The peak current of the closing current signal during the pre-breakdown stage in multiple closing operations is statistically analyzed, and a pre-breakdown current sequence is constructed. The degradation index of the pre-breakdown current sequence is determined based on the pre-breakdown current sequence.

[0083] When the circuit breaker is in the pre-breakdown stage, the instantaneous input power of the arc exceeds its dissipation power, and the arc current rises rapidly to its peak value. The spatial collisional ionization coefficient α characterizes the average number of electrons generated during this process when an electron travels a unit distance from the cathode to the anode in the electric field direction and undergoes collisional ionization. Therefore, the expression for the arc breakdown current I is derived:

[0084]

[0085] Where λ is the mean free path length of the electron, approximately 10. -5 cm represents the average distance an electron travels between two collisions; E is the instantaneous breakdown field strength; U i I is the ionization potential of the gas, with a value of 15. I0 is the ionization saturation current, approximately 10. -21 kA; d is the contact spacing between the fracture surfaces during breakdown.

[0086] like Figure 6 As shown, the arc breakdown current I varies with the instantaneous breakdown field strength E and the contact distance d in three dimensions. The results show that the arc breakdown current increases exponentially with the increase of the instantaneous breakdown field strength and the contact distance.

[0087] Let I1, I n Representing the peak closing breakdown current under the conditions of contact deterioration to the warning state and ideal state without ablation, respectively, substituting equation (4) into equation (3), taking the logarithmic transformation, and then subtracting, we get:

[0088]

[0089] Where Δd is the change in the breakdown spacing of the contact ablation fracture surface, d1, d n These represent the closing breakdown distances when the contacts deteriorate to the warning state and when they are in the ideal state without ablation, respectively.

[0090] The degradation sensitivity index (DSI) of the pre-breakdown current sequence is:

[0091]

[0092] Where n is the total number of closing operations, I t Let l be the peak current corresponding to the t-th closing pre-breakdown. Δd The threshold for reducing the closing contact distance, l Δd The standard for its value can be determined based on the research results on the degradation characteristics of circuit breaker contact stroke in relevant literature.

[0093] Comparing the degradation index with the corresponding preset threshold range includes:

[0094] At 0.8≤DSI-Id When the value is less than 1, the degradation index is not within the preset threshold range, and the warning level is determined to be reached.

[0095] Among them, DSI-I d The degradation index is mentioned above.

[0096] Introducing the maximum degradation index MaxDSI-I d Identifying sudden, abrupt behavioral changes improves the stability and sensitivity of monitoring models. Based on the numerical characteristics of the indicators, when 0.8 ≤ DSI-I... d When the value is less than 1, the breakdown structure is close to instability and reaches the warning level, so planned maintenance should be arranged.

[0097] The current discrete sequence of the steady-state arcing stage is determined based on the closing current signal, and a current time series function is constructed. The average offset of the current change rate is determined by analyzing and processing the current time series function.

[0098] The erosion of circuit breaker contacts will significantly affect the dynamic characteristics of arc behavior during the closing process, mainly manifested as increased current fluctuations and a slower attenuation trend.

[0099] Write the branch voltage equations for the capacitor bank circuit breaker based on Kirchhoff's laws:

[0100]

[0101] Where R, L, and C are the equivalent resistance, inductance, and capacitance of the circuit, respectively; R arc This represents the nonlinear resistance of the circuit breaker during arcing. ω is the voltage frequency. U is the line phase angle when the circuit is closed. e This is the power supply voltage.

[0102] During the steady-state arcing phase, branches R and R arc The values ​​are all relatively small, in [(R+R arc ) / 2L] 2 When <1 / LC, the system transitions to an underdamped state. The line current expression is obtained by performing a Laplace transform on equation (7):

[0103]

[0104] α=(R+R arc ) / 2L (9)

[0105] ω0={1 / (LC)-[(R+R arc ) / 2L] 2} 0.5 (10)

[0106] Among them, I mω0 represents the line current amplitude during the steady-state arcing phase; α is the attenuation coefficient, characterizing the signal attenuation rate; and ω0 is the oscillation frequency, determining the high-frequency oscillation characteristics.

[0107] As can be seen from equation (8), the steady-state arcing current of the circuit breaker consists of a power frequency component and an exponentially decaying high-frequency oscillation component. The power frequency component mainly depends on the fundamental parameters of the circuit; under the condition that R, L, and C are all fixed parameters, R... arc Changes in these parameters directly affect the attenuation characteristics and oscillation frequency of the high-frequency oscillation components.

[0108] like Figure 7 The figure shows the simulation calculation of the arc current response characteristics caused by the shortening of the contact stroke due to contact deterioration. The initial arc length is set to 30mm, and the changes in the contact state after contact structure deterioration are simulated by changing the moving and stationary contacts. As the effective contact distance decreases, R... arc The overall size decreases, which leads to an increase in the oscillation frequency f of the arc current and a decrease in the current decay amplitude Δi per cycle, resulting in stronger high-frequency continuous oscillation characteristics.

[0109] In time-domain feature analysis, the arc current time series function S(t) can be constructed, and the rate of change ΔS(t) between adjacent sampling points can be calculated to quantitatively characterize the fluctuation of the arc signal and realize the assessment of the contact deterioration state.

[0110]

[0111] Average offset v of the rate of change of current:

[0112]

[0113]

[0114] Where t2<t≤t4, t2 and t4 are the start time of the steady-state arcing stage and the end time of complete contact of the contacts, respectively, and R(t) is the ratio of the integral current in the two windows to the equivalent released charge; the absolute value of the derivative of this ratio represents the rate of change of the arc release ratio per unit time. This represents the average level of the fluctuation rate of the current integral ratio during this stage;

[0115] In practical measurements, based on the discrete sequence i(j) of the branch current obtained from the sampling frequency, the absolute value of the time derivative of the current integral ratio within the preceding and following time windows and the average level of the fluctuation rate of the current integral ratio can be calculated using a sliding time window. It is used to reflect the overall fluctuation level of arc stability during the arcing phase.

[0116] Comparing the average offset with the corresponding preset threshold range includes:

[0117] When 0.06 ≤ v ≤ 0.08, the average offset is not within the preset threshold range, and the warning level is determined to be reached;

[0118] Where v is the average offset.

[0119] When the observed v value during the arcing stage is in the range of 0.06≤v≤0.08, it indicates that the contact state of the contact has fluctuated significantly, indicating an instability risk, reaching the warning level, and routine maintenance is recommended.

[0120] like Figure 9 The diagram shows the circuit breaker contact degradation monitoring process. The monitoring system collects the contact voltage ΔU and closing current I in real time during the circuit breaker closing process. L When a sharp drop in the break voltage ΔU is detected, this moment t0 is determined as the breakdown initiation point, and sampling is performed backwards from this starting point until the termination moment t4, when the contacts are fully contacted, is identified. Based on the previous analysis, μ... T ≥1.5μ0 or σ T ≥5σ0、0.8≤DSI-I d <1 and 0.06≤v≤0.08 are used as condition monitoring indicators. When any two of the monitoring indicators meet the conditions, the circuit breaker contacts are determined to be in a severely degraded state, and a fault warning mechanism is triggered. This method comprehensively analyzes multiple dynamic characteristic parameters: pre-breakdown time T, and the degradation index DSI-I of the pre-breakdown current sequence. d By using the average deviation v of the current change rate, accurate identification and comprehensive monitoring of the deterioration state of circuit breaker contacts can be achieved.

[0121] Table 1 presents a comparison of different monitoring methods in identifying contact deterioration conditions.

[0122] Table 1 Comparison of different contact deterioration monitoring methods

[0123]

[0124] As can be seen from the table, the monitoring method for capacitor bank circuit breaker contact degradation proposed in this application has significant advantages in terms of the number of sensors deployed, ease of installation, and complexity of monitoring algorithms. Compared with traditional monitoring methods that rely on multi-point deployment or complex wiring structures, the method used in this application can effectively reduce system hardware costs and construction difficulty.

[0125] Furthermore, the method used in this application mainly extracts typical transient features from voltage and current waveforms, eliminating the need for high-frequency signal demodulation or complex vibration modeling. This results in a more streamlined algorithm structure, lower computational resource consumption, and easier deployment on embedded platforms. Simultaneously, it enables state awareness without altering the original circuit breaker structure or affecting its normal operation, exhibiting good engineering compatibility and field adaptability. It is suitable for long-term, stable online monitoring and trend analysis of operating equipment, providing a practical technical route for state awareness and intelligent operation and maintenance of power equipment.

[0126] like Figure 10 As shown, the present invention also provides a monitoring system for the deterioration of contacts in a capacitor bank circuit breaker, the monitoring system comprising:

[0127] An integrated sensing module, including a voltage sensor and a current sensor, is used to acquire the break voltage signal and closing current signal generated when the circuit breaker is closed.

[0128] The host computer is communicatively connected to the integrated sensing module.

[0129] Receive the disconnection voltage signal and the closing current signal;

[0130] The break voltage signal is analyzed and processed to extract the pre-breakdown time;

[0131] The peak current of the closing current signal during the pre-breakdown stage in multiple closing operations is statistically analyzed, and a pre-breakdown current sequence is constructed. The degradation index of the pre-breakdown current sequence is determined based on the pre-breakdown current sequence.

[0132] The current discrete sequence of the steady-state arcing stage is determined based on the closing current signal, and a current time series function is constructed. The average deviation of the current change rate is determined by analyzing and processing the current time series function.

[0133] The pre-breakdown time, the degradation index, and the average offset are compared with the corresponding preset threshold ranges. If any two of them do not meet the corresponding preset threshold ranges, the contacts of the circuit breaker are determined to be degraded and an early warning is triggered.

[0134] The host computer can complete operations such as data communication initialization, data reading, and control command sending with the integrated sensing module by setting serial port parameters and function options. After each circuit breaker operation, the system can automatically process and archive the extracted key feature quantities, and construct trend curves of feature parameters evolving with the operating cycle based on the number of switching operations, providing continuous data support for monitoring the degree of circuit breaker deterioration and establishing its life prediction model.

[0135] Furthermore, the monitoring system also includes a GPS synchronization and timing module, which corrects and synchronizes the time of the entire monitoring system in real time, effectively ensuring the system's real-time response and data clock synchronization.

[0136] Preferably, the monitoring system also integrates data sampling and electrical feature extraction, which can centrally process the data uploaded by the integrated sensing module and run the status monitoring model, realizing online judgment and intelligent early warning of the deterioration trend of circuit breaker contacts, providing a data foundation and decision support for intelligent perception and proactive maintenance of circuit breaker contact deterioration.

[0137] Furthermore, the integrated sensing module also includes a wireless communication unit for communicating with the host computer. For example, it can establish a connection using Bluetooth, ZigBee, or Wi-Fi. Bluetooth offers convenient connectivity and is suitable for short-range, low-power applications with small data volumes; ZigBee provides flexible networking, enabling interconnection between multiple devices with low power consumption, and is commonly used in distributed monitoring systems; Wi-Fi offers relatively long transmission distances and high data transmission rates, facilitating remote monitoring and operation.

[0138] like Figure 11 The host computer user interface shown includes a serial port parameter setting area, a function option area, a plotting control area, a parameter analysis result display area, and a waveform display module. It enables real-time reception, analysis, and visualization of data from the integrated sensor module.

[0139] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0140] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention and form different embodiments.

[0141] Those skilled in the art will understand that although the invention has been described with reference to exemplary embodiments, various changes may be made and its elements may be substituted with equivalents without departing from the scope of the invention. Furthermore, many modifications may be made to adapt particular situations or materials to the teachings of the invention without departing from the essential scope of the invention.

Claims

1. A method for monitoring the deterioration of contacts in a capacitor bank circuit breaker, characterized in that, include: Collect the break voltage signal and closing current signal generated when the circuit breaker is closed; The break voltage signal is analyzed and processed to extract the pre-breakdown time; The peak current of the closing current signal during the pre-breakdown stage in multiple closing operations is statistically analyzed, and a pre-breakdown current sequence is constructed. The degradation index of the pre-breakdown current sequence is determined based on the pre-breakdown current sequence. The current discrete sequence of the steady-state arcing stage is determined based on the closing current signal, and a current time series function is constructed. The average deviation of the current change rate is determined by analyzing and processing the current time series function. The pre-breakdown time, the degradation index, and the average offset are compared with the corresponding preset threshold ranges. If any two of them do not meet the corresponding preset threshold ranges, the contacts of the circuit breaker are determined to be degraded and an early warning is triggered.

2. The monitoring method as described in claim 1, characterized in that, A set of voltage sensors and a set of current sensors are respectively installed on both sides of the circuit breaker's break point to collect the break point voltage and the closing current.

3. The monitoring method as described in claim 2, characterized in that, The sampling frequency for obtaining the closing current is greater than or equal to 100kHz.

4. The monitoring method as described in claim 1, characterized in that, The analysis and processing of the break voltage, and the extraction of the pre-breakdown time, include: Wavelet transform is used to extract transient features from the break voltage signal during the pre-breakdown stage; The voltage drop moment of the voltage signal at the break point is detected and located as the breakdown start moment, and the waveform step rise moment is the termination moment when the contacts are fully in contact. The pre-breakdown time is obtained based on the breakdown start time and the termination time of complete contact of the contacts.

5. The monitoring method as described in claim 1, characterized in that, Comparing the pre-breakdown time with the corresponding preset threshold range includes: The mean value μ of the pre-breakdown time is determined based on the pre-breakdown time. T and standard deviation σ T ; In μ T ≥1.5μ0 or σ T When ≥5σ0, the pre-breakdown time is not within the preset threshold range, and it is determined that the warning level has been reached; Where μ0 and σ0 are the mean μ0 and standard deviation σ0 of the standard pre-breakdown time of the circuit breaker.

6. The monitoring method as described in claim 1, characterized in that, Comparing the degradation index with the corresponding preset threshold range includes: At 0.8≤DSI-I d When the value is less than 1, the degradation index is not within the preset threshold range, and the warning level is determined to be reached. Among them, DSI-I d The degradation index is mentioned above.

7. The monitoring method as described in claim 1, characterized in that, Comparing the average offset with the corresponding preset threshold range includes: When 0.06 ≤ v ≤ 0.08, the average offset is not within the preset threshold range, and the warning level is determined to be reached; Where v is the average offset.

8. A monitoring system utilizing the monitoring method for contact deterioration of a capacitor bank circuit breaker as described in any one of claims 1-7, characterized in that, The monitoring system includes: An integrated sensing module, including a voltage sensor and a current sensor, is used to acquire the break voltage signal and closing current signal generated when the circuit breaker is closed. The host computer is communicatively connected to the integrated sensing module. Receive the disconnection voltage signal and the closing current signal; The break voltage signal is analyzed and processed to extract the pre-breakdown time; The peak current of the closing current signal during the pre-breakdown stage in multiple closing operations is statistically analyzed, and a pre-breakdown current sequence is constructed. The degradation index of the pre-breakdown current sequence is determined based on the pre-breakdown current sequence. The current discrete sequence of the steady-state arcing stage is determined based on the closing current signal, and a current time series function is constructed. The average deviation of the current change rate is determined by analyzing and processing the current time series function. The pre-breakdown time, the degradation index, and the average offset are compared with the corresponding preset threshold ranges. If any two of them do not meet the corresponding preset threshold ranges, the contacts of the circuit breaker are determined to be degraded and an early warning is triggered.

9. The monitoring system as described in claim 8, characterized in that, The monitoring system also includes a GPS synchronization and time synchronization module, which corrects and synchronizes the time of the entire monitoring system in real time.

10. The monitoring system as described in claim 8, characterized in that, The integrated sensing module also includes a wireless communication unit, which is connected to the host computer for communication.

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