Optocoupler health state evaluation method based on switching time characteristic parameters

Abstract

The invention discloses an optocoupler health state evaluation method based on switching time characteristic parameters. The method comprises the following steps: pre-calibrating a mapping relation between the switching time characteristic parameters tr and CTR; when the optocoupler is in an on-line operation state, detecting and calculating to obtain an on-line real-time detection value of a switching time characteristic parameter tr of the optocoupler; calculating to obtain a CTR online real-time value corresponding to the optocoupler based on a mapping relation between a pre-calibrated switching time characteristic parameter tr and the CTR; based on the change condition of the CTR online real-time value corresponding to the optocoupler along with the online operation time of the optocoupler, the optocoupler health state evaluation is realized; according to the invention, the complex measurement process of directly measuring the CTR is avoided, and the interference on the original circuit in the measurement process is avoided; meanwhile, the method is carried out based on the performance degradation condition of the optocoupler in a real switch working mode, and the life evaluation model is established in an actual working environment, so that the health state of the optocoupler device under specific conditions can be reflected more accurately.

Description

Technical Field

[0001] The present invention belongs to the field of electronic component reliability testing, and specifically relates to an optocoupler health status assessment method based on switching time characteristic parameters, which is particularly suitable for use as a life assessment method for optocouplers in relay protection boards. Background Art

[0002] Relay protection boards are widely used in key scenarios such as high-voltage switchgear and substations, and typically integrate a large number of optocouplers. As core components in relay protection boards in power systems, optocouplers provide the electrical-optical-electrical isolation and transmission of switching signals (such as protection action signals, switch position, and power indication), ensuring safe isolation between high-voltage and low-voltage systems and precise signal transmission. Their reliability directly determines the reliability and safety of relay protection equipment. However, the long-term exposure of relay protection boards to harsh environments such as high temperatures and electromagnetic interference accelerates the aging of optocouplers.

[0003] CTR (current transfer ratio, i.e. output current I C With input current I F The current transfer ratio (CTR) is the core indicator of the optocoupler's health status. Therefore, existing optocoupler health assessments (which are also equivalent to life assessment methods) generally rely on CTR measurements. However, traditional testing technology for current transfer ratio (CTR) has significant limitations in the actual application of relay protection boards. The operation is complex: it is necessary to apply and detect the input side drive current under offline conditions. I F , and the output collector current needs to be measured I C A constant drive current must be applied continuously during the measurement, which generates additional temperature stress, causing device temperature rise offsets and affecting the accuracy of optocoupler health monitoring. Furthermore, optocouplers in relay protection boards often operate in a dynamic switching state, and CTR testing relies on static current loading, which cannot reflect the degradation mechanisms under real dynamic switching conditions. Therefore, current optocoupler life assessment models based on CTR often fail to accurately reflect the health of optocouplers under actual operating conditions (real dynamic switching).

[0004] The invention patent application with publication number CN116298848A (application number: CN202310196668.7) discloses a method, device, and medium for evaluating the expected lifespan of an optocoupler. This invention uses input current as a sensitive parameter indicating the health of the optocoupler and utilizes the Weibull distribution to derive an optocoupler lifetime model. However, this method requires offline measurement of the input current, which is complex to operate and still cannot accurately reflect the health status of the optocoupler in an actual working environment (real dynamic switching).

[0005] Chenhao Wu et al. published a paper titled "An Online Proactive CTR Monitoring Methodfor Optocoupler in Automotive Auxiliary Converter" ( IEEE Transactions on Instrumentation and Measurement , vol. 70, pp. 1-13, 2021) proposes an online optocoupler CTR test circuit that measures the CTR by measuring the voltage at key nodes. However, the CTR measurement accuracy of this method mainly depends on the voltage measurement accuracy and the accuracy of the two resistors. In practical applications, if the resistor value shifts due to aging or temperature changes, it will lead to CTR calculation errors.

[0006] To summarize, in the current existing technology, the offline measurement method used for measuring the CTR parameters of optocouplers requires interrupting the operation of the equipment and disassembling the optocoupler. During measurement, the input and output currents of the optocoupler must be monitored simultaneously, which increases the downtime and maintenance costs of the power system and cannot accurately reflect the dynamic characteristics of the device under actual working conditions. Online measurement usually requires introducing a current or voltage sampling circuit into the original circuit, which will interfere with the original circuit and change the signal transmission characteristics, resulting in limited measurement accuracy.

[0007] Therefore, the applicant hopes to seek technical solutions to solve the above technical problems. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a method for evaluating the health status of an optocoupler based on switching time characteristic parameters, which avoids the complex measurement process of directly measuring CTR and avoids interference with the original circuit during the measurement process; at the same time, the switching time characteristic parameters introduced by the present invention t r The acquisition characterization is based on the performance degradation conditions of the optocoupler in the real switching operating mode, and the life assessment model is established under the actual working environment, so it can more accurately reflect the health status of the optocoupler device under specific conditions.

[0009] The technical solution adopted in the present invention is as follows: A method for evaluating the health status of an optocoupler based on switching time characteristic parameters. The optocoupler is installed in a relay protection board. t r The optical coupler health status assessment is performed as an aging sensitive parameter of the optical coupler; wherein the optical coupler health status assessment method includes: Pre-calibrate switching time characteristic parameters t r The mapping relationship between and CTR; An edge detection module is installed in the relay protection board. When the optocoupler is in online operation, the switch time characteristic parameters of the optocoupler are detected and calculated. t r Online real-time detection value; based on pre-calibrated switching time characteristic parameters t r The mapping relationship between the optocoupler and CTR is used to calculate the online real-time CTR value corresponding to the optocoupler; The health status of the optocoupler is evaluated based on the change of the online real-time CTR value of the optocoupler as the optocoupler operates online. Among them, the switching time characteristic parameter t r Refers to the voltage difference between the output collector and the output emitter of the optocoupler during the conduction process. V CE The CTR refers to the collector current of the optocoupler at its output side. I C and its input side input current I F ratio.

[0010] Preferably, the switching time characteristic parameter t r Refers to the voltage difference V between the output collector and the output emitter of the optocoupler during the conduction process. CE The edge from 100-85%V CE Drop to 15-0%V CE time, more preferably from 95-90%V CE Drop to 10-5%V CE time.

[0011] Preferably, the calibration switching time characteristic parameter t r The mapping relationship with CTR includes the following operations: S11. Select the optocoupler as the calibration sample. When the optocoupler is offline, measure and record its switching time characteristic parameters in the initial healthy state. t r Initial value and CTR initial value; S12, applying temperature stress to the calibration sample at fixed time intervals according to the above step S11) The process described measures and records the switching time characteristic parameters at time t t r value and CTR value until the optocoupler fails, wherein the optocoupler failure means that the measured CTR value is lower than the set minimum CTR value; S13, the switching time characteristic parameters corresponding to each moment t measured in step S20 above t r The value and CTR value are normalized and converted into the switching time characteristic parameters relative to the above step S11. t r The formula for normalizing the initial value and the rate of change of the initial CTR value is as follows: ; ; Where ΔCTR(t) is the CTR change rate at time t, CTR(t) is the CTR value recorded at time t, and CTR(0) is the initial CTR value; Δ t r ( t ) is the time under a certain time t r rate of change, t r ( t ) is the characteristic parameter of the switching time recorded at the time t t r Value, t r (0) is the switching time characteristic parameter t r Initial value; S14, based on each ΔCTR(t) data and Δ t r ( t ) data, the CTR change rate and t r Establish a suitable mapping formula model between the change rates.

[0012] Preferably, in step S11, the switching time characteristic parameter t r The process of measuring and recording the initial value includes: During the conduction process of the optocoupler in its initial healthy state, measure and record the voltage difference between its output side collector and its output side emitter V CE Edge fall time; The measurement and recording process of the initial CTR value includes: providing an input current I to the input side of the optocoupler. F , measure the collector current on the output side of the optocoupler I C , according to the formula: CTR=( I C / I F )×100%, obtain the initial CTR value of the optocoupler and record it.

[0013] Preferably, in step S12, temperature stress is applied to the calibration sample by using a temperature box or self-heating method, wherein 70-90% of the maximum allowable operating temperature corresponding to the calibration sample is used as the temperature stress.

[0014] Preferably, in step S14, the mapping formula model adopts the following linear formula model: ;in, k is the correlation coefficient, ε is the compensation amount; According to the measured data, the least squares method is used to fit k and ε , cross-validation was used to ensure that the relative error of the fitted model was less than 5%, and the goodness of fit R 2 >0.9.

[0015] Preferably, the edge detection module includes a voltage signal conditioning circuit, a multi-channel ADC sampling chip, an MCU and an isolated power supply module for power supply; wherein the voltage difference of the optocoupler is converted to V CE The signal is adjusted to the rated input range of the multi-channel ADC sampling chip, and the voltage difference of the optocoupler is collected by the ADC sampling chip. V CE The signal waveform is then calculated by the MCU to obtain the switching time characteristic parameters of the optocoupler t r Online real-time detection value.

[0016] Preferably, the edge detection module is installed separately or integrated in the relay protection board; the edge detection module also includes a human-computer interaction module connected to the MCU for communication, and the switching time characteristic parameters are transmitted to the MCU through the human-computer interaction module. t r The online real-time detection value is displayed.

[0017] Preferably, the process of implementing the health status assessment of the optocoupler based on the change of the online real-time CTR value corresponding to the optocoupler with the online operation time of the optocoupler includes: At fixed time intervals, the edge detection module collects and calculates the switching time characteristic parameters corresponding to the optocoupler t r Online real-time detection value and record, based on pre-calibrated switching time characteristic parameters t r The mapping relationship between the optocoupler and CTR is used to calculate the online real-time CTR value corresponding to the optocoupler; The number of failed optocouplers corresponding to each acquisition moment is counted to generate a statistical table of the number of failed optocouplers at each acquisition moment. The failed optocoupler refers to an optocoupler whose calculated online real-time CTR value is lower than its set minimum CTR value.

[0018] Preferably, the process of implementing the health status assessment of the optocoupler based on the change of the online real-time CTR value corresponding to the optocoupler with the online operation time of the optocoupler further includes: fitting a two-parameter Weibull distribution model of the optocoupler life according to the following formula: ; ; ; Where F(t) is the cumulative failure percentage of the optocoupler at the acquisition time t, R(t) is the optocoupler reliability function corresponding to the acquisition time t; β is the shape parameter that determines the shape characteristics of the distribution; η is the scale parameter that represents the characteristic life corresponding to the specific working conditions; The F(t) is obtained using the median rank method , where i is the number of newly failed optocouplers corresponding to the cumulative failure time, and n is the total number of test optocoupler samples; the shape parameter is obtained by linear fitting the two-parameter Weibull distribution model curve β , scale parameters η And the optocoupler reliability function R ( t ); The life of the optocoupler under different online operation times is evaluated based on the corresponding CTR online real-time value of the optocoupler and its corresponding optocoupler reliability function R(t).

[0019] The present invention creatively introduces the switching time characteristic parameter t r (When the optocoupler is on, the voltage difference between its output collector and its output emitter is V CE The edge fall time of the optocoupler is used as the aging sensitive parameter of the optocoupler to evaluate the health status of the optocoupler, and it is proposed to install an edge detection module in the relay protection board to collect the switching time characteristic parameters of the optocoupler. t r Online real-time detection value, based on pre-calibrated switching time characteristic parameters t r The mapping relationship between the CTR and the optocoupler is used to calculate the online real-time CTR value corresponding to the optocoupler, thereby realizing the evaluation of the life (health status) of the optocoupler, avoiding the complex measurement process of directly measuring the CTR and avoiding interference with the original circuit during the measurement process; at the same time, the switching time characteristic parameter introduced by the present invention t rThe acquisition characterization is based on the performance degradation conditions of the optocoupler in the real switching operating mode, and the life assessment model is established in the actual working environment, so it can more accurately reflect the health status of the optocoupler device under specific conditions; In addition, the present invention only needs to calibrate the switching time characteristic parameters once t r The mapping relationship with CTR can realize the online real-time CTR value and life model establishment corresponding to the optocoupler under various working conditions, avoiding the subsequent complicated shutdown and disassembly measurement work. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the switching time characteristic parameter of the optocoupler in the specific embodiment of this application t r Schematic diagram of; Figure 2 This is a schematic diagram of the structure of the edge detection module in the specific implementation method of this application; Figure 3 It is a structural diagram of the experimental platform under the specific implementation method of this application; Figure 4 The initial voltage difference measured by the experimental platform under the specific implementation method of this application is V CE Time domain waveform; DETAILED DESCRIPTION

[0021] This embodiment provides a method for evaluating the health status of an optocoupler based on switching time characteristic parameters. The optocoupler is installed in a relay protection board, and the switching time characteristic parameters of the optocoupler are t r As the aging sensitive parameter of the optocoupler, the optocoupler health status evaluation method includes: pre-calibrating the switching time characteristic parameter t r The mapping relationship between the optocoupler and CTR; an edge detection module is installed in the relay protection board. When the optocoupler is in online operation, the switch time characteristic parameters of the optocoupler are detected and calculated. t r Online real-time detection value; based on pre-calibrated switching time characteristic parameters t r The mapping relationship between the switching time characteristic parameter and the CTR is used to calculate the online real-time CTR value corresponding to the optocoupler; the health status of the optocoupler is evaluated based on the change of the online real-time CTR value corresponding to the optocoupler as the online operation time of the optocoupler changes; t r Refers to the voltage difference between the output collector and the output emitter of the optocoupler during the conduction process. V CEEdge fall time; CTR refers to the collector current of the optocoupler on its output side I C and its input side input current I F ratio.

[0022] Preferably, in this embodiment, the switching time characteristic parameter t r Refers to the voltage difference V between the output collector and the output emitter of the optocoupler during the conduction process. CE The edge from 100-85%V CE Drop to 15-0%V CE time, more preferably from 95-90%V CE Drop to 10-5%V CE For details, see Figure 1 As shown, the switching time characteristic parameters t r Refers to the voltage difference V between the output collector and the output emitter of the optocoupler during the conduction process. CE The edge from 90%V CE Drop to 10%V CE time; Preferably, in this embodiment, the switching time characteristic parameter is calibrated t r The mapping relationship with CTR includes the following operations: S11. Select the optocoupler as the calibration sample. When the optocoupler is offline, measure and record its switching time characteristic parameters in the initial healthy state. t r Initial value and CTR initial value; preferably, in this step S11, the switching time characteristic parameter t r The process of measuring and recording the initial value includes: During the conduction process of the optocoupler in its initial healthy state, measure and record the voltage difference between its output side collector and its output side emitter V CE Edge fall time; The measurement and recording process of the initial CTR value includes: providing an input current I to the input side of the optocoupler F , measure the collector current on the output side of the optocoupler I C , according to the formula: CTR=( I C / I F )×100%, obtain the initial CTR value of the optocoupler and record it; S12, apply temperature stress to the calibration sample, and measure and record the switching time characteristic parameters at time t according to the process described in step S11) at fixed time intervals. t r value and CTR value until the optocoupler fails, where optocoupler failure means that the measured CTR value is lower than the set minimum CTR value; preferably, in this step S12, a temperature stress is applied to the calibration sample by using a temperature box or self-heating method, wherein preferably, 70-90% of the maximum allowable operating temperature corresponding to the calibration sample is used as the temperature stress; S13, the switching time characteristic parameters corresponding to each moment t measured in step S20 above t r The value and CTR value are normalized and converted into the switching time characteristic parameters relative to the above step S11. t r The formula for normalizing the initial value and the rate of change of the initial CTR value is as follows: ; ; Where ΔCTR(t) is the CTR change rate at time t, CTR(t) is the CTR value recorded at time t, and CTR(0) is the initial CTR value; Δ t r ( t ) is the time under a certain time t r rate of change, t r ( t ) is the characteristic parameter of the switching time recorded at the time t t r Value, t r (0) is the switching time characteristic parameter t r Initial value; S14, based on each ΔCTR(t) data and Δ t r ( t ) data, the CTR change rate and t r Establish a suitable mapping formula model between the change rates.

[0023] Preferably, in step S14, the mapping formula model adopts the following linear formula model: ;in, k is the correlation coefficient, ε is the compensation amount; According to the measured data, the least squares method is used to fit k and ε , cross-validation was used to ensure that the relative error of the fitted model was less than 5%, and the goodness of fit R 2 >0.9.

[0024] Preferably, see Figure 2 As shown, in this embodiment, the edge detection module includes a voltage signal conditioning circuit ( Figure 2 Marked as "voltage conditioning circuit", which can simultaneously input switching signals of multiple sets of input optocouplers), multi-channel ADC sampling chip ( Figure 2 Marked as "ADC sampling chip"), MCU and isolated power supply module for power supply ( Figure 2 Marked as "power module"); wherein, the voltage difference of the optocoupler is converted to V CE The signal is adjusted to the rated input range of the multi-channel ADC sampling chip, and the voltage difference of the optocoupler is collected by the ADC sampling chip. V CE The signal waveform is then calculated by the MCU to obtain the switching time characteristic parameters of the optocoupler t r Online real-time detection value; further preferably, in this embodiment, the edge detection module is installed separately or integrated in the relay protection board; the edge detection module also includes a human-computer interaction module connected to the MCU, and the switching time characteristic parameters are transmitted through the human-computer interaction module t r The online real-time detection value is displayed.

[0025] Preferably, in this embodiment, the process of evaluating the health status of the optocoupler based on the change of the online real-time CTR value corresponding to the optocoupler as the online operation time of the optocoupler includes: At fixed time intervals, the edge detection module collects and calculates the switching time characteristic parameters corresponding to the optocoupler t r Online real-time detection value and record, based on pre-calibrated switching time characteristic parameters t r The mapping relationship between the optocoupler and CTR is used to calculate the online real-time CTR value corresponding to the optocoupler; The number of failed optocouplers corresponding to each collection time is counted, and a statistical table of the number of failed optocouplers at each collection time is generated. A failed optocoupler refers to an optocoupler whose calculated online real-time CTR value is lower than its set minimum CTR value.

[0026] The two-parameter Weibull distribution model of the photocoupler lifetime is fitted according to the following formula: ; ; ; Where F(t) is the cumulative failure percentage of the optocoupler at the acquisition time t, R(t) is the optocoupler reliability function corresponding to the acquisition time t; β is the shape parameter that determines the shape characteristics of the distribution; η is the scale parameter that represents the characteristic life corresponding to the specific working conditions; F(t) is obtained using the median rank method , where i is the number of newly failed optocouplers corresponding to the cumulative failure time, and n is the total number of test optocoupler samples; the shape parameter is obtained by linear fitting the two-parameter Weibull distribution model curve β , scale parameters η And the optocoupler reliability function R ( t ); The life of the optocoupler under different online operation times is evaluated based on the corresponding CTR online real-time value of the optocoupler and its corresponding optocoupler reliability function R(t).

[0027] In order to enable those skilled in the art to better understand the technical solutions of the present invention, based on the above implementation scheme, the following embodiments will be specifically proposed in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0028] See Figure 3 The experimental platform shown in the figure uses the ON Semiconductor MOC8050M optocoupler sample. The voltage edge detection device (also known as the "edge detection module") uses the AD7606 multi-channel ADC sampling chip, and the MCU uses the STM32 minimum system board. The relay protection board uses the RCS-941A. The environment for applying temperature stress to the calibration sample is provided by a constant temperature chamber. In pre-calibrated switching time characteristic parameters t r When the mapping relationship between the output collector and the output emitter is established, the voltage difference between the output collector and the output emitter is measured and recorded by an oscilloscope. V CE Edge fall time, complete the switching time characteristic parameters t r Measurement and recording of initial values; CTR initial values ​​are measured and recorded when the optocoupler is offline. Specifically, input current is provided to the input side of the optocoupler. I F , the corresponding input side voltage is V F , output side voltage difference VCE , measure the collector current on the output side of the optocoupler I C , according to the formula: CTR=( I C / I F )×100%, obtain the initial CTR value of the optocoupler and record it; At room temperature, a switching signal is applied to the optocoupler sample (i.e., the calibration sample of this embodiment) and the initial voltage difference is measured. V CE The time domain waveform is as follows Figure 4 As shown (each horizontal division (div) represents 0.5 milliseconds, that is, the time span of each grid on the horizontal axis is 0.5ms; each vertical division (div) represents 4 volts, that is, the amplitude span of each grid on the vertical axis is 4V), record the switching time characteristic parameters t r Initial value; at the same time, measure and record the initial CTR value offline; Then, the optocoupler sample was subjected to an accelerated aging test under temperature stress. The optocoupler sample was placed in a constant temperature box under 85°C temperature stress and continuously powered on. The measurement and recording were performed every 100 hours. V CE Waveform and record t r ( t ), then measure and record CTR(t) offline, until its CTR(t) is lower than the minimum CTR value specified in its specification (i.e., the “set minimum CTR value” described in the entire application), which means that the optocoupler has failed; t r ( t ) data and CTR(t) data are normalized according to the scheme described in the above embodiment, and finally Δ t r And the corresponding table of ΔCTR changes is shown in Table 1:

[0029] Fit a linear formula model using the least squares method: , get the parameters k =-0.402, ε= 0.015, that is, to determine the CTR change rate and t r The mapping formula model between the change rates is: .

[0030] Install the voltage edge detection device on the relay protection board, keep the equipment in normal working condition, and record the voltage difference every 50 hours. V CECorresponding switching time characteristic parameters t r Online real-time detection value, and according to the CTR change rate and t r The mapping formula model between the change rates counts the number of corresponding failed optocouplers at each acquisition time t, and generates a statistical table of the number of failed optocouplers at each acquisition time t. The total number of test optocoupler samples is 80, and the following Table 2 is obtained:

[0031] Using the median rank method, we get F ( t ), the shape parameter in the two-parameter Weibull distribution model is obtained by linear fitting the two-parameter Weibull distribution model curve of the photocoupler lifetime. β= 0.7108, scale parameter η= 6373.43, and the reliability function R(t) is obtained: ; The lifespan of the optocoupler at different online operating times is evaluated based on the online real-time CTR value corresponding to the optocoupler and its corresponding optocoupler reliability function R(t). The specific lifespan evaluation process example of this embodiment can be referred to as follows: The initial CTR value of an optocoupler is 150%, and the minimum CTR value specified in its manual (i.e., the "set minimum CTR value") is 100%. Then, when the edge detection module tests the switching time characteristic parameters of the optocoupler, t r It has a 15% change from its initial value, that is, Δ t r =15, then the mapping formula model shows that the CTR of the optocoupler has dropped by 6.015%, that is, the CTR of the optocoupler is about 141% at this time, so the optocoupler still has a relatively high CTR at this time, and its health status is relatively good; combined with the cumulative working time t of the optocoupler and its reliability function R(t), the current operating reliability of the optocoupler is further judged. For example, if the optocoupler has been working for 128 hours, then R(128)=0.94 can be obtained, which means that the reliability of the optocoupler is currently at a relatively high level and can continue to be put into use; and when the optocoupler R(t) is less than 0.9, it can be said that the reliability of the optocoupler is already low and the optocoupler can be replaced; in implementation, the threshold value of the specific reliability R(t) can be routinely adjusted in combination with the actual reliability requirements of the system. These are conventional technical choices that can be made by those skilled in the art based on the contents of this application and do not require any creative work.

[0032] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0033] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for evaluating the health status of an optocoupler based on switching time characteristic parameters, wherein the optocoupler is installed in a relay protection board, characterized in that: The switching time characteristic parameters of the optocoupler t r The optical coupler health status assessment is performed as an aging sensitive parameter of the optical coupler; wherein the optical coupler health status assessment method includes: Pre-calibrate switching time characteristic parameters t r The mapping relationship between and CTR; An edge detection module is installed in the relay protection board. When the optocoupler is in online operation, the switch time characteristic parameters of the optocoupler are detected and calculated. t r Online real-time detection value; based on pre-calibrated switching time characteristic parameters t r The mapping relationship between the optocoupler and CTR is used to calculate the online real-time CTR value corresponding to the optocoupler; The health status of the optocoupler is evaluated based on the change of the online real-time CTR value of the optocoupler as the optocoupler operates online. Among them, the switching time characteristic parameter t r Refers to the voltage difference between the output collector and the output emitter of the optocoupler during the conduction process. V CE The CTR refers to the collector current of the optocoupler at its output side. I C and its input side input current I F ratio.

2. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 1, characterized in that: The switching time characteristic parameters t r Refers to the voltage difference V between the output collector and the output emitter of the optocoupler during the conduction process. CE The edge from 100-85%V CE Drop to 15-0%V CE time, more preferably from 95-90%V CE Drop to 10-5%V CE time.

3. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 1, wherein: The calibration switching time characteristic parameters t r The mapping relationship with CTR includes the following operations: S11. Select the optocoupler as the calibration sample. When the optocoupler is offline, measure and record its switching time characteristic parameters in the initial healthy state. t r Initial value and CTR initial value; S12, applying temperature stress to the calibration sample at fixed time intervals according to the above step S11) The process described measures and records the switching time characteristic parameters at time t t r value and CTR value until the optocoupler fails, wherein the optocoupler failure means that the measured CTR value is lower than the set minimum CTR value; S13, the switching time characteristic parameters corresponding to each moment t measured in the above step S20 t r The value and CTR value are normalized and converted into the switching time characteristic parameters relative to the above step S11. t r The formula for normalizing the initial value and the rate of change of the initial CTR value is as follows: ； ； Where ΔCTR(t) is the CTR change rate at time t, CTR(t) is the CTR value recorded at time t, and CTR(0) is the initial CTR value; Δ t r ( t ) is the time under a certain time t r rate of change, t r ( t ) is the characteristic parameter of the switching time recorded at the time t t r Value, t r (0) is the switching time characteristic parameter t r Initial value; S14, based on each ΔCTR(t) data and Δ t r ( t ) data, the CTR change rate and t r Establish a suitable mapping formula model between the change rates.

4. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 3, wherein: In step S11, the switching time characteristic parameter t r The process of measuring and recording the initial value includes: During the conduction process of the optocoupler in its initial healthy state, measure and record the voltage difference between its output side collector and its output side emitter V CE Edge fall time; The process of measuring and recording the initial CTR value includes: providing an input current I to the input side of the optocoupler. F , measure the collector current on the output side of the optocoupler I C , according to the formula: CTR=( I C / I F )×100%, obtain the initial CTR value of the optocoupler and record it.

5. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 3, wherein: In the step S12, temperature stress is applied to the calibration sample by using a temperature box or self-heating, wherein 70-90% of the maximum allowable operating temperature corresponding to the calibration sample is used as the temperature stress.

6. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 3, characterized in that: In step S14, the mapping formula model adopts the following linear formula model: ;in, k is the correlation coefficient, ε is the compensation amount; According to the measured data, the least squares method is used to fit k and ε , cross-validation was used to ensure that the relative error of the fitted model was less than 5%, and the goodness of fit R 2 > 0.

9.

7. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 1, characterized in that: The edge detection module includes a voltage signal conditioning circuit, a multi-channel ADC sampling chip, an MCU and an isolated power supply module for power supply; wherein the voltage difference of the optocoupler is converted to V CE The signal is adjusted to the rated input range of the multi-channel ADC sampling chip, and the voltage difference of the optocoupler is collected by the ADC sampling chip. V CE The signal waveform is then calculated by the MCU to obtain the switching time characteristic parameters of the optocoupler t r Online real-time detection value.

8. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 7, characterized in that: The edge detection module is installed separately or integrated in the relay protection board; The edge detection module also includes a human-computer interaction module connected to the MCU, and the switching time characteristic parameters are transmitted through the human-computer interaction module. t r The online real-time detection value is displayed.

9. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 1, wherein: The process of implementing the health status assessment of the optocoupler based on the change of the online real-time CTR value corresponding to the optocoupler as the online operation time of the optocoupler includes: At fixed time intervals, the edge detection module collects and calculates the switching time characteristic parameters corresponding to the optocoupler t r Online real-time detection value and record, based on pre-calibrated switching time characteristic parameters t r The mapping relationship between the optocoupler and CTR is used to calculate the online real-time CTR value corresponding to the optocoupler; The number of failed optocouplers corresponding to each acquisition moment is counted to generate a statistical table of the number of failed optocouplers at each acquisition moment. The failed optocoupler refers to an optocoupler whose calculated online real-time CTR value is lower than its set minimum CTR value.

10. The method for evaluating the health status of an optocoupler based on switching time characteristic parameters according to claim 9, characterized in that: The process of evaluating the health status of the optocoupler based on the change of the online real-time CTR value corresponding to the optocoupler with the online operation time of the optocoupler further includes fitting a two-parameter Weibull distribution model of the optocoupler life according to the following formula: ； ； ； Where F(t) is the cumulative failure percentage of the optocoupler at the acquisition time t, R(t) is the optocoupler reliability function corresponding to the acquisition time t; β is the shape parameter that determines the shape characteristics of the distribution; η is the scale parameter that represents the characteristic life corresponding to the specific working conditions; The F(t) is obtained using the median rank method , where i is the number of newly failed optocouplers corresponding to the cumulative failure time, and n is the total number of test optocoupler samples; the shape parameter is obtained by linear fitting the two-parameter Weibull distribution model curve β , scale parameters η and optocoupler reliability function R ( t ); The life of the optocoupler under different online operation times is evaluated based on the corresponding CTR online real-time value of the optocoupler and its corresponding optocoupler reliability function R(t).

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