An overload protection method and system for a smart meter

Abstract

The application discloses an overload protection method and system of a smart electric meter, and relates to the technical field of smart electric meter protection, which comprises the following steps: obtaining historical power consumption statistical data, determining an adaptive preset current threshold; real-time sampling of voltage signals and current signals on the load side, corresponding calculation of multi-dimensional discrimination parameters, and discrimination to generate a protection sensitivity correction coefficient; according to the comparison relationship among the multi-dimensional discrimination parameters, the adaptive preset current threshold and the rated maximum current, determining the current protection state level; according to the protection state level, the multi-dimensional discrimination parameters and the protection sensitivity correction coefficient, performing adaptive multi-dimensional protection discrimination corresponding to the protection state level, and performing a tripping protection action corresponding to the discrimination result; after the tripping protection action is performed, a tentative closing recovery is performed at a current limiting value lower than the rated maximum current. The application solves the technical problems of poor adaptability, delayed response, lack of trend prediction and heat sensing capability of the existing smart electric meter overload protection.

Description

Technical Field

[0001] This invention relates to the field of smart meter protection technology, specifically to an overload protection method and system for smart meters. Background Technology

[0002] As a core device for collecting user electricity consumption information and controlling load, the overload protection function of smart meters directly affects power supply safety and user experience. Currently widely used overload protection schemes mainly determine whether to execute protection actions based on the magnitude of the current, and then use certain delay strategies to trip or restore power supply.

[0003] However, these solutions still have shortcomings in actual operation. The judgment criteria during the protection activation phase are singular, making it difficult to adapt to the different electricity consumption habits of various users, and lacking the ability to predict load change trends, resulting in a delayed response time. During sustained overload, it cannot effectively distinguish between short-term fluctuations and continuous overloads, making it difficult to accurately reflect the thermal stress state of conductors, and also lacking proactive assessment of the load's own operational health. In the recovery phase after tripping, direct reclosing may lead to repeated tripping, lacking a reasonable recovery rhythm and termination conditions. These factors combined make it difficult for existing solutions to meet the increasingly refined electricity management needs in terms of protection accuracy, load adaptability, and power supply continuity. Summary of the Invention

[0004] This invention provides an overload protection method and system for smart meters. This invention solves the technical problems of poor adaptability, delayed response, and lack of trend prediction and thermal sensing capabilities in existing smart meter overload protection systems.

[0005] In view of the above problems, the present invention provides an overload protection method for smart meters, the method comprising: S1: Obtain historical electricity consumption statistics from smart meters and determine adaptive preset current thresholds; S2: Through the smart meter, the voltage and current signals on the load side are sampled in real time, multi-dimensional discrimination parameters are calculated accordingly, and protection sensitivity correction coefficients are generated based on the multi-dimensional discrimination parameters. S3: Determine the current protection status level based on the comparison relationship between the multidimensional discrimination parameters, the adaptive preset current threshold and the rated maximum current, wherein the protection status level includes normal status, early warning status, alarm status and trip status. S4: Based on the protection status level, the multidimensional discrimination parameters, and the protection sensitivity correction coefficient, perform adaptive multidimensional protection discrimination corresponding to the protection status level, and perform trip protection action according to the discrimination result; S5: After the trip protection action is performed, a trial closing recovery is performed with a current limit value lower than the rated maximum current.

[0006] The present invention also provides an overload protection system for a smart meter, comprising: The adaptive threshold setting module is used to obtain historical electricity consumption statistics of the smart meter and determine the adaptive preset current threshold. The multi-dimensional parameter acquisition and calculation module is used to sample the voltage and current signals on the load side in real time through the smart meter, calculate the corresponding multi-dimensional discrimination parameters, and generate the protection sensitivity correction coefficient based on the multi-dimensional discrimination parameters. The protection status identification module is used to determine the current protection status level based on the comparison relationship between the multidimensional discrimination parameters, the adaptive preset current threshold and the rated maximum current. The protection status level includes normal status, early warning status, alarm status and trip status. The graded protection execution module is used to perform adaptive multidimensional protection discrimination corresponding to the protection status level according to the protection status level, the multidimensional discrimination parameters and the protection sensitivity correction coefficient, and to perform trip protection actions according to the discrimination results. The current-limiting reclosing recovery module is used to perform a trial reclosing recovery at a current-limiting value lower than the rated maximum current after the trip protection action is performed.

[0007] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention achieves this by dynamically determining an adaptive preset current threshold, enabling the protection threshold to align with the differentiated electricity usage characteristics of various users; by finely classifying four protection status levels, it allows protection actions to perform differentiated responses based on the severity of overload; by introducing feedforward monitoring of the current change rate and a feedforward correction coefficient, it can identify rapid upward trends and trigger warnings even before the current reaches the alarm threshold; and by dynamically multiplying the basic tolerance duration, protection sensitivity correction coefficient, and feedforward correction coefficient in the warning state, it allows the warning escalation speed to be adaptively adjusted. By recursively calculating the accumulation of heat during the heating phase and the attenuation during the heat dissipation phase under alarm conditions, dynamic assessment of overload thermal stress is achieved, and tripping is escalated when the accumulated heat reaches the thermal tolerance threshold. The tripping delay is calculated using an inverse time-limit relationship under tripping conditions, and the larger value is taken as the final delay, ensuring precise matching between tripping timing and overload severity. A three-stage process—cooling and waiting after tripping, current-limiting trial reconnection, and recovery monitoring—along with exponentially increasing cooling time in case of consecutive failures and permanent tripping after reaching the maximum number of retries, achieves safe and gradual power restoration and protection termination. All steps are implemented based on the meter's existing data acquisition and processing hardware, requiring no additional hardware costs.

[0008] In summary, this invention solves the technical problems of poor overload protection adaptability, slow response, and lack of trend prediction and thermal sensing capabilities in existing smart meters. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0010] Figure 1 This is a flowchart illustrating an overload protection method for a smart meter provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the multi-level protection state division in an overload protection method for a smart meter provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the overload protection system for a smart meter provided in an embodiment of the present invention; The components represented by each number in the attached diagram are explained below: Adaptive threshold setting module 11, multi-dimensional parameter acquisition and calculation module 12, protection status identification module 13, graded protection execution module 14, and current limiting reclosing recovery module 15. Detailed Implementation

[0011] This invention provides an overload protection method and system for smart meters, which specifically solves the technical problems of poor adaptability, slow response, and lack of trend prediction and thermal sensing capabilities in existing smart meter overload protection systems.

[0012] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0013] Example 1, as Figure 1 As shown, the present invention provides an overload protection method for a smart meter, the method comprising: S1: Obtain historical electricity consumption statistics from smart meters and determine adaptive preset current thresholds.

[0014] Current smart meter overload protection technologies generally employ fixed threshold settings, directly using the meter's rated maximum current or a constant percentage as the overload criterion. This approach faces several challenges in practical applications. Different users exhibit vastly different electricity consumption behaviors, and fixed thresholds cannot simultaneously meet the protection sensitivity requirements of low-load users and the false alarm avoidance needs of high-load users, resulting in inconsistent protection effectiveness. Using historical maximum values ​​as the setting basis can lead to unreasonably high thresholds due to occasional peak currents, permanently weakening the protection response capability. Furthermore, relying solely on historical behavior to determine the threshold also presents safety risks. When users habitually consume electricity at near-rated high loads, the protection threshold may be set at the safety margin, leaving the meter lacking necessary safety margins in the long term. Therefore, how to make the overload protection threshold adaptively match the differentiated electricity consumption behaviors of different users, ensure continuous operation within the meter's safe capacity range, and effectively eliminate interference from occasional extreme values ​​has become a pressing technical problem to be solved.

[0015] Step S1 in the method provided in this embodiment of the invention includes: S1.1: Collect the historical electricity consumption statistics of the smart meter, wherein the historical electricity consumption statistics include the effective current value records for each time period within a preset statistical time window; S1.2: Load preset parameters, wherein the preset parameters include a preset quantile ratio and a rated capacity ratio coefficient; S1.3: Based on the historical electricity consumption statistics, the preset quantile current value is calculated in combination with the preset quantile ratio; S1.4: Calculate the product of the rated maximum current of the smart meter and the rated capacity proportional coefficient to obtain the rated capacity limit value; S1.5: Select the smaller of the preset quantile current value and the rated capacity limit value as the adaptive preset current threshold.

[0016] In this embodiment of the invention, the smart meter continuously samples the current signal on the load side through its built-in metering chip, with a sampling frequency of no less than 128 points per cycle, calculating the effective current value every second. The meter's microcontroller unit (MCU) writes the effective current value per minute into the EEPROM non-volatile memory, forming a minute-by-minute record of the effective current value. The meter maintains a preset statistical time sliding window data queue, for example, with a length of 30 days, meaning that the EEPROM always stores the effective current value record for each minute within the past 30 days, with a total data volume of approximately 30 × 24 × 60 = 43,200 data points. At the end of each natural day, the meter's MCU reads the above historical electricity consumption statistics from the EEPROM for subsequent adaptive threshold update calculations.

[0017] Furthermore, before the threshold calculation is initiated, the MCU first loads two sets of preset parameters pre-stored in the meter parameter area. The first set is a preset quantile ratio, which determines which quantile to extract from historical electricity consumption statistics to characterize the user's typical electricity consumption limit. In this embodiment, this ratio is set to 95%. The second set is a rated capacity ratio coefficient, which is used to apply a safety discount factor to the meter's rated maximum current, reserving sufficient operational safety margin for the meter. In this embodiment, this coefficient is set to 0.85.

[0018] The two sets of preset parameters are written into the non-volatile memory of the meter's parameter area when the meter leaves the factory. During meter operation, the microcontroller unit directly reads these two sets of parameters from the parameter area to participate in calculations. Simultaneously, these two sets of preset parameters support remote configuration and adjustment via a remote communication protocol. Power supply departments or maintenance personnel can send parameter modification commands to the meter through the master station system. After receiving and verifying the command, the meter writes the updated parameters into the parameter area to overwrite the original values, thus adapting to the differentiated needs of different application scenarios or users.

[0019] Furthermore, based on the collected minute-by-minute current RMS data dataset from the past 30 days, and combined with a preset quantile ratio of 95%, the MCU calculates the preset quantile current value I. 95% The specific calculation uses a quantile interpolation algorithm. First, all 43,200 effective current values ​​in the dataset are sorted in ascending order to obtain an ordered sequence X1≤X2≤...≤X N Where N is the total number of samples. Then, the target quantile position pos is calculated as 0.95 × (N + 1). If pos is exactly an integer, then I... 95% The data value corresponding to the specified position is directly retrieved; if pos is not an integer, the final 95th percentile current value is calculated through linear interpolation. This quantile interpolation algorithm has extremely low computational complexity, can be easily completed on the meter's MCU, and is only executed once at the end of each day, thus having no negative impact on the meter's normal metering and protection functions.

[0020] Furthermore, the MCU reads the rated maximum current I from the parameters on the smart meter's nameplate. max This parameter represents the upper limit of the safe continuous current-carrying capacity determined during the meter's design. For example, common rated maximum current values ​​for single-phase meters are 60A, 80A, and 100A. The rated maximum current I... max Multiplying this by the proportionality factor of 0.85 for the rated capacity, the rated capacity limit value I is calculated. max×0.85. The physical meaning of this limit value is that even in extreme cases where the user's electricity consumption habits are extremely aggressive and their historical percentile current value is close to or even exceeds the meter's rated capacity, the protection threshold must never exceed 85% of the meter's rated capacity. This provides a 15% safety buffer zone for the meter near its rated operating conditions, avoiding the risk of heat accumulation caused by the meter operating at the edge of its rated capacity for a long time.

[0021] Finally, the MCU will calculate the preset quantile current value I. 95% Compared with the rated capacity limit value I max The values ​​of ×0.85 are compared, and the smaller of the two is selected as the final adaptive preset current threshold I. th , that is I th =min(I 95% I max ×0.85). This adaptive preset current threshold is then stored in the MCU's random access memory (RAM) for use in subsequent comparison and discrimination of protection status levels and status classification processes.

[0022] This invention compares the preset quantile current value calculated based on historical electricity consumption statistics and a preset quantile ratio with the rated capacity limit value calculated based on the rated maximum current and rated capacity ratio coefficient, and takes the smaller value as the final threshold. This allows the adaptive preset current threshold to closely match the actual electricity consumption characteristics of different users, achieving personalized and precise protection with one threshold per household. It effectively overcomes the contradiction between fixed threshold schemes' insufficient protection for low-load users and frequent false alarms for high-load users. Simultaneously, the statistical strategy of using a preset quantile ratio instead of the maximum value effectively eliminates the interference of occasional peak currents on the threshold setting, while the rated capacity limit value physically ensures that the adaptive preset current threshold will not exceed the meter's safe operating range. All calculations are based on the meter's existing data acquisition and storage resources, performing a lightweight interpolation operation only once at the end of the preset statistical time window, achieving dynamic updates of the adaptive preset current threshold without any additional hardware costs.

[0023] S2: The voltage and current signals on the load side are sampled in real time through the smart meter, multi-dimensional discrimination parameters are calculated accordingly, and protection sensitivity correction coefficients are generated based on the multi-dimensional discrimination parameters.

[0024] Existing smart meter overload protection technology relies entirely on a single criterion: current amplitude. Protection is only triggered when the current exceeds a preset threshold, lacking proactive sensing capabilities regarding the load's operating status. This single-criterion approach suffers from severe blind spots. When faults such as motor stall, capacitor failure, or winding insulation degradation occur, the load's power factor often drops significantly before the current rises substantially. However, existing protection schemes fail to utilize the meter's existing voltage sampling data to identify these precursory faults, resulting in a lack of awareness before the fault fully develops, thus missing a valuable window for early warning and proactive intervention.

[0025] On the other hand, the background power factor levels of different loads vary greatly. Factories with concentrated inductive loads typically have low power factors, while office equipment with predominantly capacitive loads typically has high power factors. Simply using the absolute value of the power factor as the basis for anomaly detection will inevitably lead to frequent false alarms for users with low power factors, rendering the early warning mechanism unreliable. Therefore, how to effectively identify precursors to load power factor anomalies and adapt to the differences in background power factor among different load types, without increasing hardware costs, has become an urgent technical problem to be solved.

[0026] Step S2 in the method provided in this embodiment of the invention includes: S2.1: The voltage and current signals on the load side are sampled in real time through the analog-to-digital converter built into the smart meter; S2.2: Calculate the effective value of the current based on the sampled value of the current signal, and calculate the rate of change of the current based on the ratio of the difference between the effective values ​​of the current in adjacent sampling periods to the sampling period interval; S2.3: Calculate the power factor based on the sampled values ​​of the voltage signal and the current signal; S2.4: Compare the current power factor with the recent moving average of the power factor to obtain the power factor offset; S2.5: When the power factor offset is greater than the preset power factor offset threshold and the current power factor is less than the preset absolute lower limit of the power factor, it is determined that there is an abnormal precursor, and the protection sensitivity correction coefficient is set to a preset correction value less than 1; otherwise, the protection sensitivity correction coefficient is set to 1.

[0027] In this embodiment of the invention, the analog-to-digital converter (ADC) built into the smart meter samples the voltage and current signals on the load side in real time at a sampling rate of 256 points per cycle. The voltage signal is connected to the voltage sampling channel of the ADC via a resistor divider network, and the current signal is connected to the current sampling channel of the ADC via a current transformer. The sampled instantaneous voltage and current values ​​are stored in the random access memory of the microcontroller unit in digital form as the basis for subsequent RMS and power factor calculations.

[0028] Furthermore, the microcontroller unit reads all instantaneous current samples within one power frequency cycle, squares each sample, sums them, averages them, and finally takes the square root to obtain the effective current value I for that cycle. r At the end of each sampling period, the microcontroller unit calculates the effective current value I for the current period. r (n) and the effective current value I calculated in the previous sampling period r (n-1) Subtract the two values, calculate the difference, and then divide by the sampling period interval ΔTs to obtain the current change rate. In this embodiment of the invention, the sampling period interval ΔTs is 1 second, that is, the effective current value is calculated and the current change rate is updated once every 1 second.

[0029] Furthermore, the microcontroller unit synchronously calculates the power factor using all instantaneous voltage and current samples within one power frequency cycle. Specifically, it multiplies the instantaneous voltage and current values ​​at each sampling moment, sums them, and then averages the results to obtain the active power P; the effective voltage value U... r With the effective value of current I r Multiplying these two values ​​yields the apparent power S. Dividing the active power by the apparent power gives the power factor pf = P / S. When the apparent power S is zero or close to zero, the power factor calculation has no physical meaning; therefore, this power factor calculation is skipped, and the protection sensitivity correction factor β is applied. pf Keep it at 1.

[0030] Furthermore, the microcontroller unit maintains a sliding window with a length of 1800 sampling periods in random access memory. Since the sampling period interval is 1 second, this window covers the power factor historical data for the most recent 30 minutes. After each sampling period, the microcontroller unit pushes the latest calculated power factor value into the sliding window and removes the oldest power factor value from the window. Then, it calculates the arithmetic mean of all 1800 power factor values ​​in the window to obtain the moving average power factor pf. a Compare the current power factor pf(n) with the moving average power factor pf a Subtracting them, we get the power factor offset Δpf = pf a -pf(n).

[0031] Finally, the microcontroller unit loads a preset power factor offset threshold and a preset absolute lower limit of the power factor. In this embodiment, the power factor offset threshold is set to 0.15, and the absolute lower limit of the power factor is set to 0.50. When both the power factor offset Δpf is greater than 0.15 and the current power factor pf(n) is less than 0.50, the microcontroller unit determines that there is an abnormal precursor on the load side and adjusts the protection sensitivity correction coefficient β. pf Set it to 0.5; otherwise, adjust the protection sensitivity correction factor β. pf Set to 1. This protection sensitivity correction coefficient is temporarily stored in random access memory for later use in correcting the warning state tolerance duration and heat tolerance threshold.

[0032] The power factor offset threshold and the absolute lower limit of the power factor are written into the non-volatile memory of the meter's parameter area at the factory. During meter operation, the microcontroller unit directly reads these two sets of parameters from the parameter area to participate in the determination of power factor anomalies. Simultaneously, these two sets of power factor threshold parameters support remote configuration and adjustment via a remote communication protocol. Power supply departments or maintenance personnel can send parameter modification commands to the meter through the master station system to adjust the sensitivity of the determination, based on different application scenarios or differences in the load characteristics of different users. After receiving and verifying the command, the meter writes the updated parameters into the parameter area to overwrite the original values.

[0033] For example, the power factor of a user load remains stable at around 0.92 for a long period of time, and its moving average value is pf a The current power factor is approximately 0.92. If, at a certain moment, the current power factor suddenly drops to 0.43, then Δpf is 0.49, which is greater than 0.15. Furthermore, the current power factor of 0.43 is less than 0.50. Since both conditions are met simultaneously, the protection sensitivity correction coefficient is set to 0.5. For example, in a factory that uses a large number of inductive loads, the power factor fluctuates around 0.53 for a long time. Although the current power factor may occasionally drop below 0.50, its moving average is still around 0.53. The power factor deviation is much less than 0.15, which will not trigger an anomaly detection, effectively avoiding false alarms.

[0034] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0035] This invention achieves multiple technical benefits by calculating the power factor in real time and comparing it with the recent moving average, using a dual criterion of relative offset combined with an absolute lower limit to determine anomaly precursors. It can keenly capture load anomalies characterized by a sudden drop in power factor. Precursor faults such as a sharp drop in power factor during motor stall and a sudden change in reactive power during capacitor failure can be identified before current overload occurs, expanding the protection system's sensing dimension from a single current amplitude to load health status assessment. The dual criterion strategy combining relative offset and absolute lower limit effectively distinguishes between anomalies caused by a sudden drop in power factor and the inherent low power factor characteristics of the load itself, preventing false alarms for users operating under low power factor conditions for extended periods, thus improving the accuracy and practicality of anomaly detection. Once an anomaly precursor is determined, the protection sensitivity correction coefficient is set to 0.5. This correction coefficient further participates in the subsequent correction of the warning state tolerance time and thermal tolerance threshold, enabling the entire protection system to automatically increase sensitivity when detecting load anomalies, achieving a leap from passively waiting for overload to actively detecting anomalies and raising the warning level in advance. All power factor calculations are based on the existing voltage and current sampling data of the smart meter. Only software algorithms are added within the microcontroller unit, without the need to add voltage transformers, temperature sensors or any other hardware, thus achieving a zero-incremental improvement in load health perception capabilities.

[0036] S3: Determine the current protection status level based on the comparison relationship between the multidimensional discrimination parameters, the adaptive preset current threshold, and the rated maximum current. The protection status level includes normal status, early warning status, alarm status, and trip status.

[0037] Existing smart meter overload protection technologies typically employ a binary logic based on a single current threshold. This means that tripping occurs when the current exceeds a preset threshold, and normal power supply is restored when the current falls below the threshold, resulting in only two states: over-limit and not over-limit. This binary approach fails to distinguish between the different severity levels of minor and severe overloads. Tripping is triggered as soon as the current slightly exceeds the rated value, leading to over-processing of many non-urgent overload situations and causing unnecessary power outages. Furthermore, the lack of a transitional state between normal and tripping prevents users from receiving early warnings for minor overloads and fails to provide a state basis for subsequent refined protection based on thermal accumulation. On the other hand, the lack of hierarchical state classification prevents the configuration of differentiated monitoring strategies and protection parameters based on different states, resulting in a lack of targeted protection actions. Therefore, establishing a multi-level protection state classification system that reflects the differences in overload severity, providing a state basis for subsequent differentiated protection strategies, has become a pressing technical problem that needs to be solved.

[0038] Step S3 in the method provided in the embodiments of the present invention, such as Figure 2 As shown, it includes: S3.1: If the effective value of the current is less than or equal to the adaptive preset current threshold, the current protection status level is determined to be normal. S3.2: If the effective value of the current is greater than the adaptive preset current threshold and less than or equal to the rated maximum current, the current protection status level is determined to be a warning status. S3.3: If the effective value of the current is greater than the rated maximum current and less than or equal to the trip trigger threshold, the current protection status level is determined to be an alarm status, wherein the trip trigger threshold is the product of the rated maximum current and the preset trip trigger multiplier. S3.4: If the effective value of the current is greater than the trip trigger threshold, the current protection status level is determined to be a trip state.

[0039] In this embodiment of the invention, a state latching mechanism is provided to ensure the stability of the alarm state. Latching means that once the protection state level is determined to be a specific state, that state remains locked until a specific exit condition is met, and the state determination in subsequent cycles cannot arbitrarily overwrite the locked state.

[0040] Specifically, when an alarm state is triggered, the microcontroller unit sets an alarm state latch flag in the random access memory. A valid value indicates that the current state is in an alarm state lockout; an invalid value indicates that the current state is not in an alarm state lockout. Before the state determination begins in each sampling cycle, the microcontroller unit first checks the alarm state latch flag: if the alarm state latch flag is valid, the current alarm state is maintained, skipping the current range determination in step S3; if the alarm state latch flag is invalid, the current range determination in step S3 is executed. The alarm state latch flag is cleared to an invalid state by the microcontroller unit only when the overload heat accumulation Q decays to zero and the effective current value falls back to less than or equal to the rated maximum current.

[0041] In this embodiment of the invention, the effective value of the current I is completed in each sampling period. r After calculation, the microcontroller unit reads the adaptive preset current threshold I from the random access memory. th And read the rated maximum current I from the parameter area. max and the preset trip trigger ratio k t In this embodiment, k t Taking 1.2, the microcontroller unit first calculates the trip trigger threshold, i.e., I. max With k t The product of.

[0042] Furthermore, the microcontroller unit will use the current RMS value I of the current in the current sampling period. r With adaptive preset current threshold I thCompare. If I r Less than or equal to I th If the current protection status is normal, then the protection status level is determined to be normal. Normal status indicates that the power consumption is within the user's normal operating range and the line is in a safe operating zone. In this state, no protection timing or thermal accumulation calculations are initiated; only routine current monitoring is maintained.

[0043] Furthermore, if the effective value of the current I r Greater than the adaptive preset current threshold I th And less than or equal to the rated maximum current I max If the current consumption exceeds the user's usual electricity consumption pattern but has not yet exceeded the meter's rated capacity, the microcontroller unit determines the current protection status level as a warning state. A warning state indicates that the electricity consumption has exceeded the user's usual consumption pattern but has not yet exceeded the meter's rated capacity. In this state, a continuous warning timer is initiated, and the current change rate is monitored to determine if the load is in a rapid increase phase.

[0044] Furthermore, if the effective value of the current I r Greater than the rated maximum current I max And less than or equal to the trip trigger threshold I max ×k t If this condition is met, the microcontroller unit determines the current protection status level as an alarm state. The trip trigger threshold is determined by the rated maximum current and the preset trip trigger ratio k. t Multiplying, we get k in this embodiment of the invention. t The value is 1.2, meaning the trip trigger threshold is 1.2 times the rated maximum current. An alarm status indicates that the current has exceeded the meter's design rated operating conditions, posing a risk of overheating to the conductors and terminals.

[0045] Among them, the preset trip trigger ratio k t In this embodiment of the invention, k is written as a default parameter into the non-volatile memory of the meter's parameter area when the meter leaves the factory. t The value is set to 1.2, meaning the trip trigger threshold is 1.2 times the rated maximum current. During meter operation, the microcontroller unit directly reads this value from the parameter area to participate in the calculation of the trip trigger threshold. Simultaneously, this parameter supports remote configuration adjustment via a remote communication protocol. Power supply departments or maintenance personnel can issue parameter modification commands to the meter through the master station system according to the actual application scenario. After receiving and verifying the command, the meter writes the updated parameter to the parameter area to overwrite the original value.

[0046] Furthermore, if the effective value of the current I r Greater than the trip trigger threshold I max ×k t If the current exceeds the meter's rated capacity, the microcontroller unit determines the current protection status to be tripped. A tripped status indicates that the current has significantly exceeded the meter's rated capacity, requiring immediate or rapid disconnection of the load.

[0047] For example, suppose a user's adaptive preset current threshold is 32 amps, the rated maximum current is 60 amps, the trip trigger ratio is 1.2, and the trip trigger threshold is 72 amps. When the measured current is 28 amps, it is in a normal state because 28 ≤ 32 amps; when the measured current is 45 amps, it is in a warning state because 45 > 32 amps and ≤ 60 amps; when the measured current is 65 amps, it is in an alarm state because 65 > 60 amps and ≤ 72 amps; and when the measured current is 78 amps, it is in a trip state because 78 > 72 amps. Through the above four-level state division, differentiated protection strategies can be executed according to the severity of the overload.

[0048] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0049] This invention, through comparing the effective current value sequentially with an adaptive preset current threshold, the rated maximum current, and the trip trigger threshold, finely divides the protection status into four levels: normal, warning, alarm, and trip, achieving multiple technical benefits. This four-level status system accurately reflects the differences in overload severity: normal state corresponds to the normal power consumption range; warning state exceeds the normal range but does not exceed the rated current; alarm state exceeds the rated current but has not yet reached the trip threshold; and trip state indicates severe overload. This allows for differentiated protection strategies to be implemented for different levels. The warning state setting introduces a buffer zone into the system, issuing a warning without tripping when the current just exceeds the user's normal power consumption pattern, avoiding the overreaction of tripping at the slight overload in traditional solutions.

[0050] Meanwhile, the distinction between warning and alarm states provides clear state triggering conditions for subsequent current change rate feedforward monitoring and thermal accumulation calculation. This enables feedforward monitoring to accelerate in the warning state and thermal accumulation to start calculation in the alarm state, achieving orderly coordination of different protection mechanisms. The entire four-level state determination only requires three comparison operations, with extremely low computational overhead and no increase in hardware cost.

[0051] S4: Based on the protection status level, the multidimensional discrimination parameters, and the protection sensitivity correction coefficient, perform adaptive multidimensional protection discrimination corresponding to the protection status level, and perform trip protection action according to the discrimination result.

[0052] Existing smart meter overload protection schemes typically employ a single binary current threshold logic, tripping the circuit breaker as soon as the current exceeds the threshold, lacking differentiated response strategies throughout the protection process. This type of scheme has several shortcomings. Regarding early warning capabilities, traditional schemes rely entirely on the current amplitude reaching the threshold before initiating protection, lacking the ability to predict rapidly rising load changes and failing to identify risks before the current reaches a dangerous level, resulting in delayed protection response. In terms of thermal state sensing, existing schemes do not differentiate between continuous and intermittent overloads, failing to reflect the true thermal stress accumulation in conductors and terminals. While intermittent overloads may occur repeatedly, each instance is short in duration, allowing sufficient heat dissipation time for the conductor, and the actual thermal risk is not high. However, traditional schemes still treat them as continuous overloads, leading to unnecessary tripping. Conversely, minor but continuous overloads, even with currents only slightly exceeding the rated value, can still damage the insulation layer due to long-term heat accumulation, which traditional schemes may ignore because the tripping threshold has not been reached.

[0053] Meanwhile, regarding the rationality of tripping delays, existing solutions typically employ fixed delays or simple inverse-proportional delays, failing to accurately match tripping timing based on overload severity. Using the same delay logic for severe and minor overloads results in either insufficient tripping speed during severe overloads or premature tripping during minor overloads, causing unnecessary power outages. Therefore, constructing a complete protection chain—from predicting current change trends to assessing thermal stress accumulation and then to adaptive tripping based on overload severity—enabling the protection system to adopt differentiated monitoring and response strategies at different stages, has become a pressing technical problem that needs to be solved.

[0054] Step S4 in the method provided in this embodiment of the invention includes: S4a1: Calculate the difference between the rated maximum current and the adaptive preset current threshold, and divide it by the preset expected early warning time to determine the current change rate feedforward threshold. S4a2: Compare the current change rate with the current change rate feedforward threshold. When the current change rate is greater than the current change rate feedforward threshold, adjust the feedforward correction coefficient to a preset value less than 1; otherwise, adjust the feedforward correction coefficient to 1. S4a3: If the current protection status level is normal and the current change rate is greater than the current change rate feedforward threshold, the smart meter records the trend warning event and reports it. S4a4: If the current protection status level is a warning status, the corrected warning tolerance duration is determined based on the product of the basic warning tolerance duration, the protection sensitivity correction coefficient, and the feedforward correction coefficient. S4a5: Record the duration of the warning state. When the duration reaches the corrected warning tolerance duration, upgrade the current protection state level to an alarm state. Otherwise, return to step S2 to perform cyclic sampling.

[0055] In this embodiment of the invention, the current change rate feedforward threshold is first determined. Specifically, the rated maximum current I is... max Subtract adaptive preset current threshold I th Then divide the difference by the preset expected advance warning time T. an In this embodiment of the invention, the expected advance warning time T is... an Set the time to 60 seconds. The physical meaning of this threshold is that if the rate of change of current exceeds this threshold, the current is expected to rise from the adaptive preset current threshold to the rated maximum current after 60 seconds.

[0056] Among them, the preset expected advance warning time T an The default parameters are written into the non-volatile memory of the meter's parameter area when the meter leaves the factory. In this embodiment of the invention, T an Take 60 seconds. The physical meaning of this parameter is that if the rate of change of current exceeds the feedforward threshold calculated from this parameter, then it is expected that in T... an After a few seconds, the current will rise from the adaptive preset current threshold to the rated maximum current. During meter operation, the microcontroller unit directly reads this value from the parameter area to participate in the calculation of the current change rate feedforward threshold. Simultaneously, this parameter supports remote configuration adjustment via a remote communication protocol. Power supply departments or maintenance personnel can issue parameter modification commands to the meter through the master station system according to the actual application scenario. After receiving and verifying the command, the meter writes the updated parameter to the parameter area to overwrite the original value.

[0057] For example, if the rated maximum current is 60 amps and the adaptive preset current threshold is 32 amps, the difference between the two is 28 amps. Dividing this by 60 seconds gives a feedforward threshold of approximately 0.467 amps / second.

[0058] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0059] Furthermore, the current change rate calculated in the current sampling period is compared with the feedforward threshold. When the current change rate is greater than the feedforward threshold, the microcontroller unit determines that the load is in a rapid rise channel and sets the feedforward correction coefficient γ to 0.5; otherwise, the feedforward correction coefficient γ is set to 1. This correction coefficient is temporarily stored in random access memory for subsequent calculation of the warning tolerance duration.

[0060] Furthermore, when the protection status is normal and the current change rate is greater than the feedforward threshold, although the current has not yet exceeded the adaptive preset current threshold, the abnormally high current change rate indicates that a high-power load is being applied or a fault is developing. The microcontroller unit records a trend warning event, including the current timestamp, the current change rate value, and the current effective current value. Simultaneously, a slow-flashing local LED indicator alerts the user, and a warning notification is sent to the main station via the communication module.

[0061] For example, suppose the user's current measured current is 28 amps, the adaptive preset current threshold is 32 amps, the current is in a normal state, but the current change rate reaches 0.6 amps / second, which exceeds the feedforward threshold of 0.467 amps / second. At this time, the trend warning event is recorded and reported to the main station.

[0062] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0063] Furthermore, when the protection status level is in the warning state, the microcontroller unit calculates the corrected warning tolerance duration. Specifically, the basic warning tolerance duration T is... wb × Protection sensitivity correction factor β pf ×Feedforward correction coefficient γ. The basic early warning tolerance duration T in this embodiment of the invention. wb Take 600 seconds. Therefore, when the power factor is normal and there is no feedforward warning, T w =600×1×1=600 seconds; when the power factor is abnormal but there is no feedforward warning, T w =600×0.5×1=300 seconds; When the power factor is normal but there is a feedforward warning, T w =600×1×0.5=300 seconds; When the power factor is abnormal and there is a feedforward warning, T w =600 × 0.5 × 0.5 = 150 seconds. The shorter the revised warning tolerance period, the more dangerous the assessment of the current load status, and the faster the escalation to alarm status is required.

[0064] Finally, the microcontroller unit starts a timer when the state enters the warning state to record the duration of the warning state. After each sampling cycle, the current duration is compared with the corrected warning tolerance duration. When the duration reaches or exceeds the corrected warning tolerance duration, it indicates that the warning state duration has reached the allowable upper limit, and the microcontroller unit upgrades the protection status level to the alarm state. When the duration has not yet reached the tolerance duration, the warning state is maintained and the process returns to step S2 to perform the next cycle of sampling and calculation.

[0065] When the microcontroller unit upgrades the protection status level from warning state to alarm state via S4a5, the microcontroller unit immediately sets the alarm state latch flag to active in the random access memory, locking the alarm state. Until this latch flag is cleared, even if the effective current value falls back to the current range corresponding to the warning or normal state in subsequent sampling cycles, the status level remains alarm state.

[0066] It should be noted that when the alarm state is triggered from the warning state via the time escalation method of S4a5, the effective value of the current may not yet exceed the rated maximum current, and the conductor has not generated excessive Joule heat. Therefore, the initial value of the overload heat accumulation is set to zero. In each sampling cycle after entering the alarm state, heating accumulation or heat dissipation attenuation is carried out according to the rules of S4b1 and S4b2.

[0067] Step S4 in the method provided in this embodiment of the invention further includes: S4b1: In alarm state, when the effective value of the current is greater than the rated maximum current, the overload heat accumulation is accumulated by multiplying the difference between the square of the effective value of the current and the square of the rated maximum current by the sampling period interval. S4b2: In alarm state, when the effective value of the current drops to less than or equal to the rated maximum current, the overload heat accumulation is attenuated according to a preset heat dissipation attenuation rate, and the minimum value of the overload heat accumulation is zero. S4b3: Compare the overload heat accumulation with the heat tolerance threshold, wherein the heat tolerance threshold is the product of the square of the rated maximum current, the rated overload heat tolerance time, and the protection sensitivity correction coefficient; S4b4: When the accumulated overload heat is greater than or equal to the heat tolerance threshold, the current protection status level is upgraded to trip status; S4b5: When the overload heat accumulation is greater than or equal to the preset alarm ratio of the heat tolerance threshold, but less than the heat tolerance threshold, the smart meter records the heat accumulation alarm event and continues to perform monitoring in the alarm state.

[0068] In this embodiment of the invention, under alarm conditions, the microcontroller unit checks the current effective value I in each sampling cycle. r With the rated maximum current I max The size relationship. When I r >I max When the conductor is in the overload heating stage, the accumulated overload heat Q(n) is updated as follows: the square of the current effective value I is increased. r 2 Subtract the square of the rated maximum current I max 2Multiply this by the sampling period interval ΔTs to obtain the heat accumulation increment for the current sampling period. Add this increment to the heat accumulation Q(n-1) of the previous sampling period to obtain the updated heat accumulation Q(n).

[0069] The sampling period interval ΔTs is determined by the metering sampling period of the smart meter, that is, the time interval between the completion of one full sampling and the calculation of the effective value by the analog-to-digital converter inside the meter. In this embodiment of the invention, the sampling period interval ΔTs is 1 second, a value determined based on the conventional design of the smart meter. It should be noted that this sampling period interval is determined by the underlying firmware and timer interrupt period of the meter, and remains constant during the operation of the meter, without changing with the configuration of external parameters. Different models or designs of smart meters can select different sampling period intervals according to their hardware capabilities and sampling strategies. For example, some meters may use 0.5 seconds or 2 seconds, which are all conventional choices for those skilled in the art.

[0070] For example, let I max The current is 60 amperes, the heat accumulation in the previous cycle Q(n-1) was 200 ampere-seconds, and the current I... r If the current power is 65 amperes, then the increment for this period = (65 amperes) 2 -60 2 )×1=625 ampere-square seconds, after updating Q(n)=200+625=825 ampere-square seconds.

[0071] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0072] Furthermore, in the alarm state, when the effective value of the current I... r Falling back to less than or equal to the rated maximum current I max At this point, the conductor no longer generates excess Joule heat, and the existing heat accumulation begins to dissipate to the environment. At this time, the microcontroller unit reduces the overload heat accumulation Q according to a preset heat dissipation decay rate λ, i.e., Q(n) = Q(n-1) - λ × ΔTs. The heat dissipation decay rate λ is calculated from the square of the rated maximum current I... max 2 Determined by dividing by the conductor's heat dissipation time constant τ, i.e., λ = I max 2 / τ. At the same time, the microcontroller unit ensures that the minimum heat accumulation is zero, and if the result of a certain decay calculation is less than zero, it directly sets Q(n) = 0.

[0073] The conductor heat dissipation time constant τ is determined through type testing. Specifically, during the type test, the rated maximum current I is applied to the smart meter. maxThe current is continuously supplied until the temperature of the internal conductor of the meter reaches a thermally stable state, after which the current is cut off. A temperature sensor continuously records the temperature drop curve of the conductor over time. The temperature drop curve is fitted and calculated, and the time required for the conductor temperature to drop from the steady-state temperature rise value to 36.8% of that steady-state temperature rise value (i.e., a drop of 63.2%) is taken as the conductor heat dissipation time constant τ. In this embodiment of the invention, the typical range of τ obtained through the above type test calibration is 300 seconds to 600 seconds. This τ value, after being calibrated before the meter leaves the factory, is written as a fixed parameter into the non-volatile memory of the meter's parameter area for subsequent calculation of the heat dissipation attenuation rate λ.

[0074] For example, let I max For 60 amperes, I max 2 If the time is 3600 seconds and τ is 400 seconds, then λ = 3600 / 400 = 9 amperes squared per second. If the heat accumulation Q(n-1) in the previous cycle is 825 amperes squared per second, then after the update in this cycle, Q(n) = 825 - 9 × 1 = 816 amperes squared per second.

[0075] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0076] Furthermore, in each sampling cycle, the microcontroller unit compares the current accumulated overload heat Q(n) with the heat tolerance threshold Q. th A comparison was made. The heat tolerance threshold Q th The calculation method is as follows: I = (squared) the rated maximum current. max 2 Multiply by the rated overload heat withstand time T th Then multiply by the protection sensitivity correction factor β pf Q th =I max 2 ×T th ×β pf .

[0077] Among them, the rated overload heat withstand time T th The T value in this embodiment of the invention is predetermined by the manufacturer based on product design standards and conductor thermal safety requirements before the meter leaves the factory. th Take 300 seconds. The physical meaning of this parameter is: the conductor operates at its rated maximum current I. maxThe thermal withstand time scale is determined based on the thermal aging characteristics of the insulation layer of the internal conductors of the meter, the maximum allowable operating temperature of the terminals, and the thermal withstand requirements specified in relevant national standards. For conventional smart meters, the typical range of this parameter is 180 to 600 seconds. This parameter is written as a default parameter into the non-volatile memory of the meter's parameter area when the meter leaves the factory. During meter operation, the microcontroller unit directly reads this value from the parameter area to participate in the thermal withstand threshold Q. th The calculation is performed. Simultaneously, this parameter supports remote configuration adjustment via a remote communication protocol. Maintenance personnel can send parameter modification commands to the meter through the main station system based on the differences in thermal characteristics of different meter specifications or the protection requirements of special application scenarios. After receiving and verifying the command, the meter writes the updated parameters into the parameter area to overwrite the original values.

[0078] For example, let I max For 60 amperes, I max 2 For 3600, T th For 300 seconds, β pf =1, then Q th =3600×300×1=1,080,000 amperes squared seconds; if β pf =0.5, then Q th Reduced to 540,000 ampere-square seconds.

[0079] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0080] Furthermore, when Q(n) ≥ Q th When this occurs, it indicates that the accumulated thermal stress in the conductor has reached the safety tolerance limit, and the microcontroller unit upgrades the protection status from alarm to trip. Simultaneously, it raises the thermal tolerance threshold Q... th Multiplying by a preset alarm ratio of 80% yields an early alarm trigger value, when Q th ×80%≤Q(n) th At that time, the microcontroller unit records the thermal accumulation alarm event, including the current timestamp, Q(n) value, and I. r Information such as values ​​is reported to the main station via the communication module, and monitoring continues in the alarm state until Q(n) reaches Q. th Triggering a trip or current drop causes Q(n) to decay below the alarm trigger value.

[0081] For example, let Q th ​The threshold is 1,080,000 ampere-seconds, and the 80% threshold is 864,000 ampere-seconds. When Q(n) reaches 864,000 ampere-seconds or more but has not yet reached 1,080,000 ampere-seconds, a heat accumulation alarm event is sent to the master station to notify the master station that a trip is about to be triggered.

[0082] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0083] When both conditions are met—that the effective current value falls back to less than or equal to the rated maximum current and the overload heat accumulation decays to zero—the microcontroller unit clears the alarm state latch flag to an invalid state, releasing the alarm state from lock. Subsequently, the microcontroller unit re-executes the current range determination in step S3 based on the current effective current value, transitioning to the corresponding normal or warning state.

[0084] Step S4 in the method provided in this embodiment of the invention further includes: S4c1: In the tripping state, the overload multiple is determined based on the ratio of the effective value of the current to the rated maximum current, and the tripping delay is calculated according to the inverse time characteristic relationship, wherein the larger the overload multiple, the shorter the tripping delay; S4c2: Compare and select the larger of the trip delay and the preset minimum trip delay as the final trip delay; S4c3: If the duration of the tripping state reaches the final tripping delay, execute the tripping protection action.

[0085] In this embodiment of the invention, under tripped conditions, the overload factor is first calculated, i.e., the current effective value I. r With the rated maximum current I max The ratio I r / I max The larger this ratio, the more severe the overload. Subsequently, the tripping delay t is calculated according to the inverse time-delay characteristic relationship. t The calculation rule is that the larger the overload multiple, the shorter the tripping delay; the closer the overload multiple is to 1, the longer the tripping delay. The inverse time calculation formula used in this embodiment is t. t =K / [(I r / I max ) α -1], where K is the inverse time constant and α is the inverse time characteristic index. In this embodiment of the invention, K is 5.0 and α is 2.0.

[0086] The values ​​of the inverse-time constant K and the inverse-time characteristic index α were determined through a combination of simulation verification and type testing. First, theoretical calculations were performed based on the recommended curves for inverse-time overcurrent protection characteristics in relevant standards to initially determine the range of values ​​for K and α. Then, actual measurements were conducted at different overload multiples to ensure that the trip delay met the protection coordination requirement of approximately 11 seconds based on the theoretically calculated delay at 1.2 times the rated current, and that the theoretically calculated delay at 1.5 times the rated current did not exceed the preset minimum trip delay. This ensured that overloads of 1.5 times and above could trigger the minimum trip delay constraint, ultimately determining the aforementioned values. These parameters are written into the meter's non-volatile memory before the meter leaves the factory and are considered low-level protection setting parameters. Remote configuration modification is not allowed during normal meter operation to ensure the stability and consistency of the protection characteristics.

[0087] For example, let I max For 60 amperes, currently I r The current is 72 amps, and the overload factor is 72 / 60 = 1.2. The calculated value is t. t =5.0 / (1.2 2 -1) = 5.0 / 0.44 ≈ 11.36 seconds; when I r At 78 amps, the overload factor is 78 / 60 = 1.3, t t =5.0 / (1.3 2 -1) = 5.0 / 0.69 ≈ 7.25 seconds; when I r At 90 amps, the overload factor is 90 / 60 = 1.5, t t =5.0 / (1.5 2 -1) = 5.0 / 1.25 = 4 seconds. Therefore, the more severe the overload, the shorter the tripping delay.

[0088] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0089] Furthermore, the microcontroller unit calculates the trip delay t obtained through inverse time-delay calculation. t With the preset minimum trip delay t t，min The two values ​​are compared, and the larger one is selected as the final tripping delay. In this embodiment of the invention, t t，min Taking 5 seconds is intended to prevent extreme overload conditions. t If the calculated value is too small, it will cause malfunctions, thus providing immunity for normal transient processes such as motor startup.

[0090] Among them, the preset minimum tripping delay t t，min Before the electricity meter leaves the factory, the manufacturer pre-determines the protection setting parameters according to national standards and typical load characteristics, and writes them into the non-volatile memory of the meter's parameter area. In this embodiment of the invention, t t，minSet to 5 seconds. This parameter is set based on the minimum operating time requirement for inverse-time overcurrent protection of terminal power distribution protection devices in relevant national standards, as well as the duration of a typical motor starting process. The full-voltage starting time of small and medium-sized asynchronous motors is usually 2 to 8 seconds. A minimum trip delay of 5 seconds is sufficient to cover most normal starting processes, avoiding false tripping caused by motor starting current surges, while also preventing excessive delay in protection action. This achieves a reasonable balance between transient surges and actual overloads.

[0091] For example, when I r When the current is 90 amperes, the inverse time-limited calculated value t t =4 seconds, t t，min =5 seconds, and the final tripping delay is the larger of the two, which is 5 seconds; when I r When the current is 78 amperes, t t =7.25 seconds, t t，min =5 seconds, and the final trip delay is the larger of the two, which is 7.25 seconds; when I r When the current is 72 amperes, t t =11.36 seconds, and the final trip delay is the larger of the two, which is 11.36 seconds.

[0092] It should be noted that the above values ​​are for illustrative purposes only and do not constitute a limitation on the present invention.

[0093] Finally, a timer is started when the trip state is entered to record the duration of the trip state. When the trip state duration reaches the final trip delay, the microcontroller unit outputs a control signal to drive the relay to disconnect the circuit, execute the trip protection action, and cut off the load power supply. After the trip protection action is executed, the microcontroller unit clears the alarm state latch flag, the overload thermal accumulation, and the trip state duration timer. These clearing operations provide the initial state for the next restart of the overload protection process.

[0094] This invention achieves early prediction of overload trends through feedforward monitoring of current change rate. It accurately distinguishes between the different thermal effects of continuous and intermittent overloads using a recursive calculation method that accumulates during the heating phase and decays during the heat dissipation phase. During intermittent overloads, the accumulated heat decreases during the heat dissipation phase, preventing easy tripping. In contrast, continuous overloads accumulate until a tripping threshold is reached. The inverse-time tripping characteristic achieves precise matching between tripping timing and overload severity; the larger the overload multiple, the faster the tripping, and vice versa. These three elements work synergistically to enable the protection system to provide early warning during the current rise phase, accurately assess overload heat accumulation during the overload phase, and reasonably delay the final tripping phase. This achieves full-process hierarchical protection from warning to tripping, and all algorithms are implemented based on existing meter hardware resources without adding any sensors or hardware costs.

[0095] S5: After the trip protection action is performed, a trial closing recovery is performed with a current limit value lower than the rated maximum current.

[0096] Existing smart meters typically employ two recovery strategies after overload tripping: direct full reconnection to restore power, or manual reconnection by the user. Both methods have significant technical drawbacks. With direct full reconnection, if the overload fault on the load side has not yet been resolved, the current will rapidly exceed the threshold again after reconnection, causing frequent reconnection and tripping of the meter. This repeated impact not only causes severe wear on the meter's relay contacts and shortens equipment lifespan but also causes cumulative electrical shocks to the load-side equipment and lines, while also causing repeated power interruptions for users, severely impacting their electricity experience. If manual reconnection is used, it relies entirely on human intervention, making automatic recovery impossible and reducing power continuity. Furthermore, existing solutions lack an effective termination mechanism after multiple failed recovery attempts, potentially leading to an endless series of reconnection and tripping attempts until equipment damage occurs. Therefore, how to achieve safe automatic power restoration without removing the faulty load, effectively avoid damage to equipment and lines from reverse reconnection shocks, and reasonably terminate the automatic recovery process after multiple failed attempts has become a pressing technical problem to be solved.

[0097] Step S5 in the method provided in this embodiment of the invention includes: S5.1: After executing the trip protection action, enter the preset cooling waiting stage; S5.2: After the cooling waiting phase ends, the current limiting value is obtained by multiplying the preset current limiting ratio by the rated maximum current, and based on the current limiting value, the smart meter is limited to perform a trial closing. S5.3: During the preset recovery monitoring period, monitor whether the effective value of the current is continuously lower than the current limit value. If so, it is determined that the power supply recovery conditions are met, the current limit is canceled, and normal power supply is restored.

[0098] In this embodiment of the invention, after the microcontroller unit performs the trip protection action, the relay disconnects, and the power supply to the load side is cut off. At this time, a preset cooling waiting phase begins, allowing the load-side equipment and lines to cool down sufficiently. In this embodiment of the invention, the cooling waiting phase lasts for 60 seconds.

[0099] The cooling waiting period is predetermined by the manufacturer before the meter leaves the factory, based on the heat capacity and heat dissipation characteristics of the internal conductors. This value is written into the non-volatile memory of the meter's parameter area as a system default parameter; in this embodiment, it is set to 60 seconds. This parameter is set based on the fact that after a trip, the load side is de-energized, the conductor no longer generates new Joule heat, and existing heat begins to dissipate naturally to the environment. According to the basic principles of heat conduction, the conductor temperature drops fastest within the first 60 seconds after the power outage, and most of the releaseable heat is dissipated during this phase. A 60-second cooling time is sufficient to reduce the conductor temperature from the overload temperature at the time of the trip to below a safe level, while also considering the need for timely power restoration. This parameter is written into the parameter area at the factory. During meter operation, the microcontroller unit directly reads this value from the parameter area and executes the cooling timer after each trip.

[0100] Furthermore, after the cooling waiting phase, the microcontroller unit calculates the current limiting value, which is the preset current limiting ratio of 50% multiplied by the rated maximum current I. max The current limiting value I is obtained. limit =50%×I max Subsequently, the microcontroller unit outputs a closing control signal to drive the relay to close, using the current limit value as the maximum allowable current after closing for a trial closing. After closing, the microcontroller unit monitors the effective current value once per second. Once it detects that the effective current value exceeds the current limit value, it immediately trips the circuit again. Because the current limit value is far below the normal overload trip threshold, even if there is a fault on the load side, it will not cause substantial thermal damage to the line.

[0101] The preset current limiting ratio is written as a default parameter in the parameter area when the meter leaves the factory; in this embodiment, it is set to 50%. This value strikes a balance between safety and the feasibility of power restoration. 50% of the rated maximum current is far below the tripping trigger threshold, so even if there is a fault on the load side, it will not cause thermal damage. At the same time, this current limiting value is sufficient to drive the light-load operation of most normal loads, avoiding false judgments of restoration failure due to an excessively low current limiting value. This parameter can be remotely configured and adjusted via a remote communication protocol to adapt to the differentiated needs of different application scenarios.

[0102] Furthermore, after a successful trial closing, the microcontroller unit enters a preset recovery monitoring period, which is 300 seconds in this embodiment. During this period, the microcontroller unit continuously monitors whether the effective current value remains below the current limit. If the effective current value remains below the current limit for 300 seconds, the power supply recovery condition is met, the current limit is lifted, and normal power supply capacity is restored. If the effective current value exceeds the current limit during the recovery monitoring period, the monitoring is deemed a failure, and the trip protection action is executed again.

[0103] Step S5 in the method provided in this embodiment of the invention further includes: S5.4: If the effective value of the current does not remain lower than the current limit value during the recovery monitoring period, it is determined that the power supply recovery conditions are not met, and the trip protection action is executed again. S5.5: Each time the trip protection action is executed again, the duration of the cooling waiting phase is increased exponentially using the backoff method; S5.6: Record the cumulative number of times the trip protection action is executed again, and compare it with the preset maximum number of retry attempts; S5.7: When the cumulative number of attempts reaches the maximum number of retries, a permanent trip is executed, and the permanent trip is restricted to be canceled only through manual operation and remote command.

[0104] In this embodiment of the invention, if the effective value of the current rises above the current limit value during the recovery monitoring period, the microcontroller unit determines that the power supply recovery conditions are not met, immediately outputs a trip control signal, and performs the trip protection action again.

[0105] Furthermore, each time the trip protection action is executed again, the microcontroller unit increments the cooling-off period using an exponential backoff method, with the recursive formula being T1. （k） =T1×2 k-1 Where k represents the number of consecutive failures. In this embodiment of the invention, the basic cooling time T1 is 60 seconds, that is, the cooling time after the first trip is 60 seconds, the cooling time after the second trip is 120 seconds, and the cooling time after the third trip is 240 seconds. The core idea of ​​exponential backoff is that the more consecutive failures there are, the more stubborn the fault on the load side is, and the longer the cooling time is given, so as to avoid repeated impacts on the line and equipment caused by frequent reconnection.

[0106] The basic cooling time T1 is set based on the following principle: after a trip, the load side loses power, and the conductor no longer generates new Joule heat. Existing heat begins to dissipate naturally to the environment. According to the basic principle of heat conduction, the conductor temperature drops most rapidly within the first 60 seconds after the power outage, during which most of the releaseable heat is dissipated. A basic cooling time of 60 seconds is sufficient to reduce the conductor temperature from the overload temperature at the time of the trip to below a safe level, while also taking into account the need for timely power restoration. This parameter is written into the parameter area when the meter leaves the factory and supports remote configuration adjustment via a remote communication protocol. Maintenance personnel can adjust the basic cooling time according to the differences in thermal characteristics of different meter specifications to adapt to the differentiated needs of different application scenarios.

[0107] Furthermore, the microcontroller unit maintains a trip counter to record the cumulative number of times the trip protection action is executed consecutively after the same overload event occurs. Each time the trip protection action is executed again, the microcontroller unit increments the cumulative count by 1 and compares it with the preset maximum number of retries. In this embodiment of the invention, the preset maximum number of retries is 3.

[0108] Furthermore, when the cumulative number of retries reaches the preset maximum, the microcontroller unit performs a permanent trip, the relay remains open, and it no longer automatically attempts to close the circuit to restore power. After a permanent trip, the permanent trip can only be lifted manually, such as by pressing a physical button on the meter or resetting the switch, or remotely via a command from the master station through the communication module. The purpose of this constraint mechanism is to prevent endless automatic closing and tripping when a serious fault on the load side has not been resolved, thus avoiding cumulative damage to equipment and lines, while also ensuring the personal safety of maintenance personnel.

[0109] This invention achieves safe and automatic recovery after a trip through a progressive recovery process consisting of three stages: cooling and waiting, current-limiting trial closing, and recovery monitoring. The cooling and waiting stage allows sufficient time for the load-side equipment and lines to cool down. The current-limiting trial closing uses a current limit far below the rated maximum current, ensuring no substantial thermal damage to the lines even if the load-side fault is not resolved. The recovery monitoring stage continuously monitors whether the current is stable below the current limit to confirm that the load has returned to normal. Only after successful monitoring is the current limit lifted and full-capacity power supply restored, avoiding the secondary tripping oscillations that may occur with direct full-capacity closing in traditional solutions.

[0110] Building upon this, an exponential backoff method is used to progressively extend the cooling time. The more consecutive failures, the longer the cooling time. This allows the faulty equipment more time to dissipate heat and avoids repeated impacts on relay contacts and circuits caused by frequent circuit breaker closing within a short period. By setting a maximum number of retries and performing a permanent trip after reaching the limit, the potential for endless automatic closing and tripping leading to equipment damage is avoided. After a permanent trip, only manual operation or remote command is allowed to reset the circuit, ensuring that power will not be automatically restored if a serious fault remains, thus protecting equipment and personnel safety. These two methods work together to maximize power supply continuity while ensuring safety, and all logic is implemented in software within the existing microcontroller unit of the meter, without adding any hardware costs.

[0111] In summary, the embodiments of the present invention have at least the following technical effects: This invention achieves this by dynamically determining an adaptive preset current threshold, enabling the protection threshold to align with the differentiated electricity usage characteristics of various users; by finely classifying four protection status levels, it allows protection actions to perform differentiated responses based on the severity of overload; by introducing feedforward monitoring of the current change rate and a feedforward correction coefficient, it can identify rapid upward trends and trigger warnings even before the current reaches the alarm threshold; and by dynamically multiplying the basic tolerance duration, protection sensitivity correction coefficient, and feedforward correction coefficient in the warning state, it allows the warning escalation speed to be adaptively adjusted. By recursively calculating the accumulation of heat during the heating phase and the attenuation during the heat dissipation phase under alarm conditions, dynamic assessment of overload thermal stress is achieved, and tripping is escalated when the accumulated heat reaches the thermal tolerance threshold. The tripping delay is calculated using an inverse time-limit relationship under tripping conditions, and the larger value is taken as the final delay, ensuring precise matching between tripping timing and overload severity. A three-stage process—cooling and waiting after tripping, current-limiting trial reconnection, and recovery monitoring—along with exponentially increasing cooling time in case of consecutive failures and permanent tripping after reaching the maximum number of retries, achieves safe and gradual power restoration and protection termination. All steps are implemented based on the meter's existing data acquisition and processing hardware, requiring no additional hardware costs.

[0112] In summary, this invention solves the technical problems of poor overload protection adaptability, slow response, and lack of trend prediction and thermal sensing capabilities in existing smart meters.

[0113] Example 2, as Figure 3 As shown, based on the same inventive concept as the overload protection method for a smart meter provided in Embodiment 1, this embodiment of the invention also provides an overload protection system for a smart meter, comprising: The adaptive threshold setting module 11 is used to obtain historical electricity consumption statistics of the smart meter and determine the adaptive preset current threshold. The multi-dimensional parameter acquisition and calculation module 12 is used to sample the voltage and current signals on the load side in real time through the smart meter, calculate the corresponding multi-dimensional discrimination parameters, and generate the protection sensitivity correction coefficient based on the multi-dimensional discrimination parameters. The protection status identification module 13 is used to determine the current protection status level based on the comparison relationship between the multidimensional discrimination parameters, the adaptive preset current threshold and the rated maximum current, wherein the protection status level includes normal status, early warning status, alarm status and trip status. The graded protection execution module 14 is used to perform adaptive multidimensional protection discrimination corresponding to the protection status level according to the protection status level, the multidimensional discrimination parameters and the protection sensitivity correction coefficient, and to perform trip protection action according to the discrimination result. The current-limiting reclosing recovery module 15 is used to perform a trial reclosing recovery with a current-limiting value lower than the rated maximum current after the trip protection action is performed.

[0114] In one embodiment, the adaptive threshold setting module 11 is specifically used for: Collect the historical electricity consumption statistics of smart meters, wherein the historical electricity consumption statistics include the effective current value records for each time period within a preset statistical time window; Load preset parameters, wherein the preset parameters include a preset percentile ratio and a rated capacity ratio coefficient; Based on the historical electricity consumption statistics, the preset quantile current value is calculated in conjunction with the preset quantile ratio. The rated capacity limit value is obtained by multiplying the rated maximum current of the smart meter by the rated capacity proportional coefficient. The smaller of the preset quantile current value and the rated capacity limit value is selected as the adaptive preset current threshold.

[0115] In one embodiment, the multidimensional parameter acquisition and calculation module 12 is specifically used for: The smart meter uses a built-in analog-to-digital converter to sample the voltage and current signals on the load side in real time. The effective value of the current is calculated based on the sampled value of the current signal, and the rate of change of the current is calculated based on the ratio of the difference between the effective values ​​of the current in adjacent sampling periods to the sampling period interval. The power factor is calculated based on the sampled values ​​of the voltage and current signals. The current power factor is compared with the recent moving average of the power factor to obtain the power factor offset; When the power factor offset is greater than the preset power factor offset threshold and the current power factor is less than the preset absolute lower limit of the power factor, it is determined that there is an abnormal precursor, and the protection sensitivity correction coefficient is set to a preset correction value less than 1; otherwise, the protection sensitivity correction coefficient is set to 1.

[0116] In one embodiment, the protection status identification module 13 is specifically used for: If the effective value of the current is less than or equal to the adaptive preset current threshold, the current protection status level is determined to be normal. If the effective value of the current is greater than the adaptive preset current threshold and less than or equal to the rated maximum current, the current protection status level is determined to be a warning status. If the effective value of the current is greater than the rated maximum current and less than or equal to the trip trigger threshold, the current protection status level is determined to be an alarm status, wherein the trip trigger threshold is the product of the rated maximum current and the preset trip trigger multiplier. If the effective value of the current is greater than the trip trigger threshold, the current protection status level is determined to be a trip state.

[0117] In one embodiment, the hierarchical protection execution module 14 is specifically used for: Calculate the difference between the rated maximum current and the adaptive preset current threshold, and divide it by the preset expected early warning time to determine the current change rate feedforward threshold. The current change rate is compared with the current change rate feedforward threshold. When the current change rate is greater than the current change rate feedforward threshold, the feedforward correction coefficient is adjusted to a preset value less than 1; otherwise, the feedforward correction coefficient is adjusted to 1. If the current protection status level is normal, and the current change rate is greater than the current change rate feedforward threshold, the smart meter records the trend warning event and reports it. If the current protection status level is a warning status, the corrected warning tolerance duration is determined based on the product of the basic warning tolerance duration, the protection sensitivity correction coefficient, and the feedforward correction coefficient. Record the duration of the warning state. When the duration reaches the corrected warning tolerance duration, upgrade the current protection state level to an alarm state. Otherwise, return to step S2 to perform cyclic sampling.

[0118] In one embodiment, the hierarchical protection execution module 14 is further specifically used for: In alarm mode, when the effective value of the current is greater than the rated maximum current, the overload heat accumulation is accumulated by multiplying the difference between the square of the effective value of the current and the square of the rated maximum current by the sampling period interval. In alarm mode, when the effective value of the current drops to less than or equal to the rated maximum current, the overload heat accumulation is attenuated according to a preset heat dissipation attenuation rate, and the minimum value of the overload heat accumulation is zero. Compare the accumulated overload heat with the heat tolerance threshold, wherein the heat tolerance threshold is the product of the square of the rated maximum current, the rated overload heat tolerance time, and the protection sensitivity correction coefficient. When the accumulated overload heat is greater than or equal to the heat tolerance threshold, the current protection status level will be upgraded to trip status. When the overload heat accumulation is greater than or equal to the preset alarm ratio of the heat tolerance threshold, but less than the heat tolerance threshold, the smart meter records the heat accumulation alarm event and continues to perform monitoring in the alarm state.

[0119] In one embodiment, the hierarchical protection execution module 14 is further specifically used for: In the tripped state, the overload factor is determined based on the ratio of the effective current value to the rated maximum current, and the tripping delay is calculated according to the inverse time characteristic relationship. The larger the overload factor, the shorter the tripping delay. The larger of the trip delay and the preset minimum trip delay is selected as the final trip delay; If the duration of the tripping state reaches the final tripping delay, the tripping protection action is executed.

[0120] In one embodiment, the current-limiting reclosing recovery module 15 is specifically used for: After the trip protection action is executed, a preset cooling and waiting phase is entered; After the cooling waiting phase ends, the current limiting value is obtained by multiplying the preset current limiting ratio by the rated maximum current, and based on the current limiting value, the smart meter performs a trial closing operation with the current limited. During the preset recovery monitoring period, if the effective value of the monitored current is continuously lower than the current limit value, then it is determined that the power supply recovery conditions are met, the current limit is canceled, and normal power supply is restored.

[0121] In one embodiment, the current-limiting reclosing recovery module 15 is further configured to: If the effective value of the current does not remain below the current limit value during the recovery monitoring period, it is determined that the power supply recovery conditions are not met, and the trip protection action is executed again. Each time the trip protection action is executed again, the duration of the cooling waiting phase is increased exponentially using the backoff method. Record the cumulative number of times the trip protection action is executed again, and compare it with the preset maximum number of retries; When the cumulative number of attempts reaches the maximum number of retries, a permanent trip is executed, and the permanent trip is restricted to be canceled only through manual operation and remote command.

[0122] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, the above description focuses on specific embodiments of this specification. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0124] This specification and accompanying drawings are merely illustrative examples of the invention and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its scope. Therefore, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is intended to include these modifications and modifications.

Claims

1. An overload protection method for a smart meter, characterized in that, include: S1: Obtain historical electricity consumption statistics from smart meters and determine adaptive preset current thresholds; S2: Through the smart meter, the voltage and current signals on the load side are sampled in real time, multi-dimensional discrimination parameters are calculated accordingly, and protection sensitivity correction coefficients are generated based on the multi-dimensional discrimination parameters. S3: Determine the current protection status level based on the comparison relationship between the multidimensional discrimination parameters, the adaptive preset current threshold and the rated maximum current, wherein the protection status level includes normal status, early warning status, alarm status and trip status. S4: Based on the protection status level, the multidimensional discrimination parameters, and the protection sensitivity correction coefficient, perform adaptive multidimensional protection discrimination corresponding to the protection status level, and perform trip protection action according to the discrimination result; S5: After the trip protection action is performed, a trial closing recovery is performed with a current limit value lower than the rated maximum current.

2. The overload protection method for a smart meter as described in claim 1, characterized in that, Step S1 includes: S1.1: Collect the historical electricity consumption statistics of the smart meter, wherein the historical electricity consumption statistics include the effective current value records for each time period within a preset statistical time window; S1.2: Load preset parameters, wherein the preset parameters include a preset quantile ratio and a rated capacity ratio coefficient; S1.3: Based on the historical electricity consumption statistics, the preset quantile current value is calculated in combination with the preset quantile ratio; S1.4: Calculate the product of the rated maximum current of the smart meter and the rated capacity proportional coefficient to obtain the rated capacity limit value; S1.5: Select the smaller of the preset quantile current value and the rated capacity limit value as the adaptive preset current threshold.

3. The overload protection method for a smart meter as described in claim 1, characterized in that, Step S2 includes: S2.1: The voltage and current signals on the load side are sampled in real time through the analog-to-digital converter built into the smart meter; S2.2: Calculate the effective value of the current based on the sampled value of the current signal, and calculate the rate of change of the current based on the ratio of the difference between the effective values ​​of the current in adjacent sampling periods to the sampling period interval; S2.3: Calculate the power factor based on the sampled values ​​of the voltage signal and the current signal; S2.4: Compare the current power factor with the recent moving average of the power factor to obtain the power factor offset; S2.5 When the power factor offset is greater than the preset power factor offset threshold and the current power factor is less than the preset absolute lower limit of the power factor, it is determined that there is an abnormal precursor, and the protection sensitivity correction coefficient is set to a preset correction value less than 1; otherwise, the protection sensitivity correction coefficient is set to 1.

4. The overload protection method for a smart meter as described in claim 1, characterized in that, Step S3 includes: S3.1: If the effective value of the current is less than or equal to the adaptive preset current threshold, the current protection status level is determined to be normal. S3.2: If the effective value of the current is greater than the adaptive preset current threshold and less than or equal to the rated maximum current, the current protection status level is determined to be a warning status. S3.3: If the effective value of the current is greater than the rated maximum current and less than or equal to the trip trigger threshold, the current protection status level is determined to be an alarm status, wherein the trip trigger threshold is the product of the rated maximum current and the preset trip trigger multiplier. S3.4: If the effective value of the current is greater than the trip trigger threshold, the current protection status level is determined to be a trip state.

5. The overload protection method for a smart meter as described in claim 3, characterized in that, Step S4 includes: S4a1: Calculate the difference between the rated maximum current and the adaptive preset current threshold, and divide it by the preset expected early warning time to determine the current change rate feedforward threshold. S4a2: Compare the current change rate with the current change rate feedforward threshold. When the current change rate is greater than the current change rate feedforward threshold, adjust the feedforward correction coefficient to a preset value less than 1; otherwise, adjust the feedforward correction coefficient to 1. S4a3: If the current protection status level is normal and the current change rate is greater than the current change rate feedforward threshold, the smart meter records the trend warning event and reports it. S4a4: If the current protection status level is a warning status, the corrected warning tolerance duration is determined based on the product of the basic warning tolerance duration, the protection sensitivity correction coefficient, and the feedforward correction coefficient. S4a5: Record the duration of the warning state. When the duration reaches the corrected warning tolerance duration, upgrade the current protection state level to an alarm state. Otherwise, return to step S2 to perform cyclic sampling.

6. The overload protection method for a smart meter as described in claim 1, characterized in that, Step S4 includes: S4b1: In alarm state, when the effective value of the current is greater than the rated maximum current, the overload heat accumulation is accumulated by multiplying the difference between the square of the effective value of the current and the square of the rated maximum current by the sampling period interval. S4b2: In alarm state, when the effective value of the current drops to less than or equal to the rated maximum current, the overload heat accumulation is attenuated according to a preset heat dissipation attenuation rate, and the minimum value of the overload heat accumulation is zero. S4b3: Compare the overload heat accumulation with the heat tolerance threshold, wherein the heat tolerance threshold is the product of the square of the rated maximum current, the rated overload heat tolerance time, and the protection sensitivity correction coefficient; S4b4: When the accumulated overload heat is greater than or equal to the heat tolerance threshold, the current protection status level is upgraded to trip status; S4b5: When the overload heat accumulation is greater than or equal to the preset alarm ratio of the heat tolerance threshold, but less than the heat tolerance threshold, the smart meter records the heat accumulation alarm event and continues to perform monitoring in the alarm state.

7. The overload protection method for a smart meter as described in claim 1, characterized in that, Step S4 includes: S4c1: In the tripping state, the overload multiple is determined based on the ratio of the effective value of the current to the rated maximum current, and the tripping delay is calculated according to the inverse time characteristic relationship, wherein the larger the overload multiple, the shorter the tripping delay; S4c2: Compare and select the larger of the trip delay and the preset minimum trip delay as the final trip delay; S4c3: If the duration of the tripping state reaches the final tripping delay, execute the tripping protection action.

8. The overload protection method for a smart meter as described in claim 1, characterized in that, Step S5 includes: S5.1: After executing the trip protection action, enter the preset cooling waiting stage; S5.2: After the cooling waiting phase ends, the current limiting value is obtained by multiplying the preset current limiting ratio by the rated maximum current, and based on the current limiting value, the smart meter is limited to perform a trial closing. S5.3: During the preset recovery monitoring period, monitor whether the effective value of the current is continuously lower than the current limit value. If so, it is determined that the power supply recovery conditions are met, the current limit is canceled, and normal power supply is restored.

9. The overload protection method for a smart meter as described in claim 8, characterized in that, Step S5 also includes: S5.4: If the effective value of the current does not remain lower than the current limit value during the recovery monitoring period, it is determined that the power supply recovery conditions are not met, and the trip protection action is executed again. S5.5: Each time the trip protection action is executed again, the duration of the cooling waiting phase is increased exponentially using the backoff method; S5.6: Record the cumulative number of times the trip protection action is executed again, and compare it with the preset maximum number of retry attempts; S5.7: When the cumulative number of attempts reaches the maximum number of retries, a permanent trip is executed, and the permanent trip is restricted to be canceled only through manual operation and remote command.

10. An overload protection system for a smart meter, characterized in that, An overload protection method for performing any one of claims 1 to 9 of a smart meter includes: The adaptive threshold setting module is used to obtain historical electricity consumption statistics of the smart meter and determine the adaptive preset current threshold. The multi-dimensional parameter acquisition and calculation module is used to sample the voltage and current signals on the load side in real time through the smart meter, calculate the corresponding multi-dimensional discrimination parameters, and generate the protection sensitivity correction coefficient based on the multi-dimensional discrimination parameters. The protection status identification module is used to determine the current protection status level based on the comparison relationship between the multidimensional discrimination parameters, the adaptive preset current threshold and the rated maximum current. The protection status level includes normal status, early warning status, alarm status and trip status. The graded protection execution module is used to perform adaptive multidimensional protection discrimination corresponding to the protection status level according to the protection status level, the multidimensional discrimination parameters and the protection sensitivity correction coefficient, and to perform trip protection actions according to the discrimination results. The current-limiting reclosing recovery module is used to perform a trial reclosing recovery at a current-limiting value lower than the rated maximum current after the trip protection action is performed.

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