Overload long time delay protection characteristic self-setting method and intelligent controller of circuit breaker

Abstract

The application is suitable for the technical field of circuit breaker, and particularly relates to an overload long-delay protection characteristic self-setting method and a circuit breaker intelligent controller. The method comprises the following steps: obtaining an electric current equivalent value, a current thermal time constant, a current reference current and a current safety factor; calculating a current thermal capacity usage rate through a first-order thermal network; determining that a thermal state compensation condition is met, and performing thermal state compensation on the current thermal time constant and the current reference current according to the current thermal capacity usage rate; generating a current protection curve; correcting the compensated reference current and the current safety factor through cold state simulation verification to obtain a final reference current and a final safety factor; and correcting the compensated thermal time constant through thermal state simulation verification to obtain a final thermal time constant. The method can sense the actual thermal state of a protection object in the setting process, reduces the interference of residual states on the result, and improves the objectivity of performance evaluation of the protection device.

Description

Technical Field

[0001] This application belongs to the field of circuit breaker technology, and in particular relates to a self-tuning method for overload long-delay protection characteristics and a circuit breaker intelligent controller. Background Technology

[0002] When the operating current of equipment such as lines, motors, and transformers continuously exceeds the rated value, although they may not be damaged immediately in a short period of time, their conductors and insulation will age faster due to the continuous accumulation of heat effects, and in severe cases, may even cause faults or fires. Therefore, low-voltage power distribution and motor protection devices generally incorporate long-delay overload protection circuits. These circuits enable the protection devices to effectively cut off continuous overloads while ensuring normal equipment startup, preventing false cutoffs of short-term impact loads and transient fluctuations, based on the inverse time-delay law that the greater the overload, the shorter the operating time.

[0003] In existing technologies, the setting of circuit breaker protection characteristics typically relies on physical testing methods involving offline test benches or field injection of large currents. These methods require removing the circuit breaker from the primary circuit or connecting an external current generator after disconnecting the primary circuit. This is not only complex to operate, but also susceptible to residual effects from previous states under continuous setting or testing conditions. This leads to distorted evaluations of the protection device's performance and makes it difficult to accurately distinguish and reflect the true protection characteristics of the protected object in its initial and post-heating states, thus affecting the authenticity and accuracy of the self-setting results.

[0004] For circuit breakers that are already in operation and in a energized state, physical testing methods are almost impossible to implement on-site. Frequent power outages and disassemblies not only seriously affect the continuity of power supply, but also lack professional current injection equipment and a controlled testing environment on-site, making it difficult to carry out the setting process.

[0005] In summary, during the self-tuning process of protection devices, there are problems such as the difficulty in implementing physical testing methods on-site and the susceptibility of protection devices to residual effects from the previous state of the protected object, which can lead to distorted protection performance evaluation and thus affect the self-tuning results. Summary of the Invention

[0006] This application provides a self-tuning method for overload long-delay protection characteristics and a circuit breaker intelligent controller, which can solve the problems in related technologies where, during the self-tuning process of protection devices, the difficulty in implementing physical testing methods on-site and the susceptibility of protection devices to residual influences from the previous state of the protected object lead to distorted protection performance evaluation, thereby affecting the self-tuning results.

[0007] In a first aspect, embodiments of this application provide a self-tuning method for overload long-delay protection characteristics, including:

[0008] In response to the setting signal, the equivalent current value, the current thermal time constant, the current reference current, and the current safety factor are obtained; among them, the thermal time constant is used to control the rate of heat accumulation and heat dissipation.

[0009] The current heat capacity utilization rate is calculated using a first-order thermal network based on the current equivalent value, the current thermal time constant, and the current reference current.

[0010] Based on the current heat capacity utilization rate, it is determined that the thermal compensation condition is met, and based on the current heat capacity utilization rate, thermal compensation is performed on the current thermal time constant and the current reference current to obtain the compensated thermal time constant and the compensated reference current; wherein, the thermal compensation condition is that the current heat capacity utilization rate is greater than the cold threshold.

[0011] Based on the compensated thermal time constant, the compensated reference current, and the current safety factor, a current protection curve is generated; wherein, the current protection curve is an inverse time characteristic curve of current versus time.

[0012] Based on the current protection curve, the compensated reference current and the current safety factor are corrected through cold simulation verification to obtain the final reference current and the final safety factor.

[0013] Based on the final reference current, the compensated thermal time constant is corrected through thermal simulation to obtain the final thermal time constant.

[0014] The technical solutions described in this application embodiment have at least the following technical effects:

[0015] The overload long-delay protection characteristic self-tuning method provided in this application first obtains the equivalent current value, the current thermal time constant (used to control the rate of heat accumulation and heat dissipation), the current reference current, and the current safety factor by responding to the setting signal. Then, based on the equivalent current value, the current thermal time constant, and the current reference current, the current heat capacity utilization rate is calculated through a first-order thermal network. Next, based on the current heat capacity utilization rate, the thermal compensation condition (the current heat capacity utilization rate is greater than the cold threshold) is determined. Based on the current heat capacity utilization rate, thermal compensation is performed on the current thermal time constant and the current reference current to obtain the compensated thermal time constant and the compensated reference current. Then, based on the compensated thermal time constant, the compensated reference current, and the current safety factor, the current protection curve (the inverse time characteristic curve of current versus time) is generated. Based on the current protection curve, the compensated reference current and the current safety factor are corrected through cold-state simulation verification to obtain the final reference current and the final safety factor. Finally, based on the final reference current, the compensated thermal time constant is corrected through thermal simulation verification to obtain the final thermal time constant. This method enables the setting process to sense and quantify the real-time thermal state of the protected object, avoiding the direct introduction of heat accumulation generated during previous tests or operation into the current setting result. This effectively reduces the interference of residual state on the result, improving the accuracy and consistency of the setting result. By introducing thermal state modeling, compensation, and verification mechanisms, this method makes the setting process more repeatable and stable, and the results obtained under different test conditions are more comparable, thereby improving the objectivity of the performance evaluation of the protection device. By reducing the need for repeated setting, repeated testing, and multiple rounds of verification caused by result deviations, this method can significantly reduce setting time and testing costs, and improve engineering implementation efficiency. Both cold-state simulation verification and hot-state simulation verification of this method are simulation processes executed inside the processor of the circuit breaker intelligent controller. It does not require injecting any real physical current into the primary circuit or current sampling circuit, does not require waiting for the equipment to physically heat up and cool down, and does not require disconnecting the primary circuit or external test equipment. It can be completed online in milliseconds while the circuit breaker is energized.

[0016] Secondly, embodiments of this application provide a self-tuning device for overload long-delay protection characteristics, comprising:

[0017] The acquisition unit is used to acquire the equivalent current value, the current thermal time constant, the current reference current, and the current safety factor in response to the setting signal; wherein, the thermal time constant is used to control the rate of heat accumulation and heat dissipation;

[0018] The heat capacity utilization calculation unit is used to calculate the current heat capacity utilization rate through a first-order thermal network based on the current equivalent value, the current thermal time constant, and the current reference current.

[0019] The compensation unit is used to determine whether the thermal compensation condition is met based on the current heat capacity utilization rate, and to perform thermal compensation on the current thermal time constant and the current reference current based on the current heat capacity utilization rate to obtain the compensated thermal time constant and the compensated reference current; wherein, the thermal compensation condition is that the current heat capacity utilization rate is greater than the cold threshold.

[0020] The protection curve generation unit is used to generate a current protection curve based on the compensated thermal time constant, the compensated reference current, and the current safety factor; wherein, the current protection curve is an inverse time characteristic curve of current versus time.

[0021] The cold-state verification unit is used to correct the compensated reference current and the current safety factor based on the current protection curve through cold-state simulation verification, so as to obtain the final reference current and the final safety factor.

[0022] The thermal verification unit is used to correct the compensated thermal time constant based on the final reference current through thermal simulation verification to obtain the final thermal time constant.

[0023] Thirdly, embodiments of this application provide a circuit breaker intelligent controller, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described in any of the embodiments of the first aspect.

[0024] It is understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating a self-tuning method for overload long-delay protection characteristics provided in an embodiment of this application;

[0027] Figure 2 This is a schematic diagram illustrating the implementation process of generating the current protection curve in the self-tuning method for overload long-delay protection characteristics provided in this application embodiment;

[0028] Figure 3 This is a schematic diagram of the structure of the overload long delay protection characteristic self-tuning device provided in the embodiments of this application;

[0029] Figure 4 This is a schematic diagram of a circuit breaker intelligent controller provided in an embodiment of this application;

[0030] Figure 5 This is another structural schematic diagram of the intelligent circuit breaker controller provided in the embodiments of this application. Detailed Implementation

[0031] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0032] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0033] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0034] In related technologies, protection devices typically require multiple adjustments, continuous tests, and repeated verifications to obtain protection parameters that match the protected object. These tests and verifications largely rely on physical experimental methods, namely, injecting a specific current into the primary circuit or current sampling circuit of the circuit breaker through an external current source and waiting for the equipment to actually heat up until tripping occurs. However, under continuous adjustment or continuous testing conditions, the state influence of the previous test process on the protected object often cannot be eliminated in time. This residual state continues to be carried over into subsequent tests, causing the results to no longer simply reflect the protection performance that the protection device should provide for the protected object under the current adjustment conditions. Instead, it incorporates the influence of factors left over from previous tests, resulting in biased test results, distorted protection performance assessments, and an inaccurate reflection of the protection device's true protection capability for the protected object under current conditions.

[0035] Furthermore, the actual capacity and corresponding protection requirements of the protected object vary under different conditions, and the protection effect of the protection device also differs when facing the protected object in different conditions. Existing self-tuning technology lacks a clear and effective ability to distinguish these differences, making it difficult to accurately determine the protection performance of the protected object in its initial state and its protection performance after continuous operation and temperature rise accumulation. Because test results from different states are easily intersected and mixed, the final tuning conclusion often fails to objectively reflect the actual protection capability of the protection device for the protected object under different states, and it is also difficult to accurately evaluate whether the protection parameters truly meet the usage requirements of the protected object.

[0036] The aforementioned physical energization testing method is almost impractical in a live-line operating environment. On the one hand, disconnecting the primary circuit for testing would affect the continuity of power supply, which is generally not permitted in industrial sites; on the other hand, the lack of standardized current injection equipment and controlled environment in the field makes it difficult to guarantee test accuracy and repeatability.

[0037] To address the aforementioned issues, this application provides a self-tuning method for overload long-delay protection characteristics and a circuit breaker intelligent controller. In this method, firstly, in response to a setting signal, the equivalent current value, the current thermal time constant (used to control the rate of heat accumulation and dissipation), the current reference current, and the current safety factor are obtained. Then, based on the equivalent current value, the current thermal time constant, and the current reference current, the current thermal capacity utilization rate is calculated using a first-order thermal network. Next, based on the current thermal capacity utilization rate, the condition for satisfying thermal compensation (the current thermal capacity utilization rate is greater than the cold-state threshold) is determined. Then, based on the current thermal capacity utilization rate, thermal compensation is performed on the current thermal time constant and the current reference current to obtain the compensated thermal time constant and the compensated reference current. Next, based on the compensated thermal time constant, the compensated reference current, and the current safety factor, a current protection curve (an inverse time characteristic curve of current versus time) is generated. Then, based on the current protection curve, the compensated reference current and the current safety factor are corrected through cold-state simulation verification to obtain the final reference current and the final safety factor. Finally, based on the final reference current, the compensated thermal time constant is corrected through thermal simulation verification to obtain the final thermal time constant. This method enables the setting process to sense and quantify the real-time thermal state of the protected object, avoiding the direct introduction of heat accumulation generated during previous tests or operation into the current setting result. This effectively reduces the interference of residual state on the result, improving the accuracy and consistency of the setting result. By introducing thermal state modeling, compensation, and verification mechanisms, this method makes the setting process more repeatable and stable, and the results obtained under different test conditions are more comparable, thereby improving the objectivity of the performance evaluation of the protection device. By reducing the need for repeated setting, repeated testing, and multiple rounds of verification caused by result deviations, this method can significantly reduce setting time and testing costs, and improve engineering implementation efficiency. Both cold-state simulation verification and hot-state simulation verification of this method are simulation processes executed inside the processor of the circuit breaker intelligent controller. It does not require injecting any real physical current into the primary circuit or current sampling circuit, does not require waiting for the equipment to physically heat up and cool down, and does not require disconnecting the primary circuit or external test equipment. It can be completed online in milliseconds while the circuit breaker is energized.

[0038] The overload long-delay protection characteristic self-tuning method provided in this application embodiment can be applied to the circuit breaker intelligent controller. In this case, the circuit breaker intelligent controller is the execution subject of the overload long-delay protection characteristic self-tuning method provided in this application embodiment. This application embodiment does not impose any restrictions on the specific type of circuit breaker intelligent controller.

[0039] A circuit breaker intelligent controller may include a current acquisition device, an ambient temperature acquisition device, a protection actuator, and a control device that communicates with the current acquisition device, ambient temperature acquisition device, and protection actuator. The current acquisition device is capable of acquiring the current value of the circuit containing the protected object; it can be a current transformer (CT), a Hall current sensor, a Rogowski coil, etc. The ambient temperature acquisition device is capable of acquiring the ambient temperature surrounding the protected object; it can be a digital temperature sensor, a thermistor sensor (such as an NTC thermistor, a PTC thermistor), a resistance temperature detector (RTD) sensor (such as a PT100, PT1000), etc. The protection actuator is capable of performing protection actions when the protected object is overloaded; it may include a trip unit, a relay, a circuit breaker drive module, etc. The control device is capable of data processing and controlling the current acquisition device, ambient temperature acquisition device, and protection actuator; it can be a microcontroller (MCU), a digital signal processor (DSP), an ARM processor / embedded processor, an FPGA or CPLD, a PLC control unit, a SoC control platform, etc.

[0040] To better understand the self-tuning method for overload long-delay protection characteristics provided in the embodiments of this application, the specific implementation process of the self-tuning method for overload long-delay protection characteristics provided in the embodiments of this application will be described by way of example below.

[0041] Figure 1 This illustration shows a schematic flowchart of the self-tuning method for overload long-delay protection characteristics provided in an embodiment of this application. The self-tuning method for overload long-delay protection characteristics includes:

[0042] S100, in response to the setting signal, acquires the equivalent current value, the current thermal time constant, the current reference current, and the current safety factor. The thermal time constant is used to control the rate of heat accumulation and dissipation.

[0043] It is understandable that the setting signal is used to trigger the protection device (such as the circuit breaker intelligent controller) to start the self-setting process.

[0044] The thermal time constant indicates the rate of heat accumulation and dissipation of the protected object (such as a motor or cable). The larger the value, the slower the change in heat accumulation and dissipation; the smaller the value, the faster the change in thermal state. The thermal time constant does not only represent the inherent physical thermal constant of the protected object, but also includes equivalent dynamic parameters used to describe the protection response characteristics under thermal conditions.

[0045] The reference current is the maximum current value that the protected object (such as a motor, cable, etc.) can operate continuously for a long time without triggering overload protection.

[0046] The safety factor reflects the safety margin of the protected object against short-term overload. It is mainly determined by the type of equipment, thermal tolerance, and design protection principles, and is a relatively stable a priori parameter.

[0047] For example, the setting signal may include a manual trigger signal and an event trigger signal. A manual trigger signal may be a setting start command issued by maintenance personnel to the protection device via a human-machine interface, a background monitoring system, or a communication interface when the equipment is first put into operation, after maintenance or replacement, after parameters are restored to factory settings, or when protection parameters need to be reassessed. Upon receiving the command, the protection device automatically executes the subsequent setting process.

[0048] Event trigger signals can be signals that allow the protection device to autonomously initiate a self-tuning process when preset trigger conditions are met, based on monitoring of its operating status. Preset trigger conditions may include: first power-on operation or detection of new equipment connection; detection of a significant change in load type; detection of a long-term steady-state temperature rise deviating from the historical baseline; detection of parameter reset or hardware replacement after maintenance.

[0049] By using the two triggering methods mentioned above, the protection device can start the self-tuning process under clear boundaries and well-defined triggering conditions, thus avoiding parameter drift and mixed results caused by unconditional continuous tuning.

[0050] After receiving the setting signal, the protection device can collect the current signals of phases A, B, and C respectively through a current acquisition device (such as a current transformer), and obtain the discrete sampling sequence of the currents of phases A, B, and C within the current calculation cycle through analog-to-digital conversion. , , ,in, N is the number of sampling points in the current calculation period.

[0051] The effective values ​​of the discrete sampling sequences of the currents in each phase can be calculated to obtain the effective values ​​of the currents in phases A, B, and C. , , ,in, , , These represent the effective current values ​​of phases A, B, and C within the current calculation period k, respectively.

[0052] The equivalent current value can be the maximum value among the effective values ​​of the three-phase current, i.e. This method is suitable for scenarios where overheating of any phase, such as three-phase cables, motor windings, or busbars, could lead to failure. The equivalent current value can be the average of the effective values ​​of the three-phase currents, i.e. This method is suitable when the focus of protection is on the overall load level. The equivalent current value can be expressed as the root mean square equivalent of the three-phase current RMS value, i.e. This method can more accurately characterize the combined heating effect of three phases. In practical applications, a correspondence between the object type and the current equivalent value calculation method can be established in advance. For example, the maximum value method can be used for cable protection; the average value method or the root mean square method can be used for general three-phase balanced loads. The protection device can also allow users to select the corresponding calculation method through parameter configuration.

[0053] The thermal time constant saved after the last setting can be retrieved from the control device's storage unit as the current thermal time constant, reflecting the thermal dynamic characteristics of the protected object after the previous correction. Initial thermal time constant. It can be calibrated experimentally or preset according to the type of protected object. For example, a common electric motor. power distribution cables Variable frequency drive power supply motor ,transformer The protection device allows users to manually input the initial thermal time constant and provides a recommended input range as a guide, such as 100s~1200s.

[0054] The rated current of the protected object can be used as the initial value of the current reference current, which is beneficial for subsequent correction of the reference current based on cold simulation verification. This ensures that the final setting result is based on the rated parameters of the equipment and can be optimized in combination with the actual protection characteristics.

[0055] The current safety factor can be obtained by looking up a table based on the type of protected object. For example, the safety factor K=1.15 for a motor, K=1.10 for a distribution cable, and K=1.20 for a transformer. The current safety factor is obtained by resetting it using a table lookup method and does not inherit the previous setting value. If the historically corrected safety factor is used directly, it may lead to the accumulation of errors in multiple rounds of setting. For example, if the safety factor is corrected from 1.15 to 1.12 in the first setting after cold simulation verification, and the second setting continues to use 1.12 as the starting value, this offset may continue to amplify in subsequent settings, eventually causing the protection curve to gradually deviate from the original safety margin setting of the protected object. Therefore, each time self-tuning is started, the initial safety factor is re-obtained according to the type of protected object. This helps to suppress the drift caused by the setting history and allows the protection parameters to return to the safety boundary based on the inherent capacity of the protected object.

[0056] The protection device can cache the equivalent current value, the current thermal time constant, the current reference current, and the current safety factor as input parameters for the current setting cycle in the running register or storage unit for subsequent steps to call.

[0057] S200 calculates the current heat capacity utilization rate through a first-order thermal network based on the current equivalent value, the current thermal time constant, and the current reference current.

[0058] Exemplarily, when the protected object is operating under overload, the temperature rise process has the characteristics of thermal inertia and can be approximately described by a first-order thermal network. The first-order thermal network can be equivalently regarded as a thermal dynamic system composed of thermal resistance and heat capacity. The heat capacity represents the heat storage capacity, the thermal resistance represents the heat dissipation capacity, and the thermal time constant represents the comprehensive dynamic speed of heat accumulation and heat dissipation.

[0059] The heat generation of a conductor or winding is proportional to the square of the current. The square of the ratio of the current equivalent value to the current reference current can be used as the unitized heat input quantity, that is , where represents the heat generation intensity in the current calculation period k, represents the current reference current.

[0060] It can be understood that the heat capacity utilization rate H can be introduced as a thermal state variable to describe the thermal state of the protected object. The heat capacity utilization rate is a dimensionless quantity, representing the proportion of the current heat accumulation to the allowable heat capacity. H = 0 indicates a cold state or a state with basically no heat accumulation; 0 < H < 1 indicates that there is a certain amount of heat accumulation but the thermal limit has not been reached; H = 1 indicates that the heat capacity upper limit has been reached. The heat capacity utilization rate H is a normalized expression of the temperature rise state of the protected object, which can avoid the measurement difficulties and object differences caused by directly using absolute temperature and is more suitable for real-time iterative calculations in protection devices.

[0061] Exemplarily, the thermal dynamic process of the protected object can be expressed as a continuous-time first-order differential equation (i.e., the first-order thermal network): , where represents the heat capacity utilization rate at time t, represents the current thermal time constant.

[0062] Since the protection device samples and operates according to a fixed calculation period, the above differential equation can be discretized. It can be assumed that the current setting operation period is , and the Euler discretization method is used to calculate the current heat capacity utilization rate, that is , where represents the current heat capacity utilization rate, represents the heat capacity utilization rate in the previous calculation period.

[0063] The exponential discretization method can also be used to improve the calculation accuracy, that is . Select the Euler discretization method or the exponential discretization method according to the processor resources and accuracy requirements. If the requirement for operation complexity is low, the Euler discretization method can be used; if the requirement for thermal state tracking accuracy is high, the exponential discretization method can be used.

[0064] When the protection device is first started for setting, historical thermal states are not available, or the protected object has been sufficiently cooled, the initial thermal capacity utilization rate can be set to zero, i.e., H=0. When the setting process is continuous, and the protected object has not been completely cooled after the previous round of setting or testing, the thermal capacity utilization rate saved at the end of the previous round of setting can be read as the current initial value for calculation to retain thermal history information.

[0065] This step enables continuous tracking and quantitative expression of the thermal state of the protected object. Compared with methods based solely on instantaneous current or simple time accumulation, this step can simultaneously reflect the combined impact of historical heat accumulation and current load changes on temperature rise, making the obtained heat capacity utilization rate both physically consistent and possessing good dynamic response characteristics. This provides an accurate and stable basis for subsequent thermal compensation judgment and protection parameter correction.

[0066] In one possible implementation, please refer to Figure 2 S200, based on the equivalent current value, the current thermal time constant, and the current reference current, calculates the current heat capacity utilization rate through a first-order thermal network, including:

[0067] S210, calculate the per-unit value of the current based on the equivalent current value and the current reference current.

[0068] For example, the protection device can calculate the per-unit value of the current based on the current equivalent value and the current reference current, i.e. ,in, This indicates the per-unit value of the current.

[0069] S220 constructs a continuous thermal equilibrium model based on the per-unit current value, the current thermal time constant, and the first-order thermal network.

[0070] For example, the expression for a first-order heat network is: ,in, The term "thermal state" can refer to either temperature rise or thermal state quantity. For heat input, is the thermal time constant.

[0071] The protected object can be represented as a first-order thermal network composed of thermal resistance and heat capacity. Heat capacity characterizes the protected object's ability to store heat, thermal resistance characterizes its ability to dissipate heat to the environment, and the current thermal time constant characterizes the dynamic process of heat accumulation and dissipation. Using the current heat capacity utilization rate as the thermal state variable, the continuous thermal balance model can be expressed as: In this context, the Joule heating power of the protected object is approximately proportional to the square of the current, and the square of the per-unit value of the current can be used as the heat input.

[0072] S230 performs differential discretization on the continuous thermal balance model to obtain the current heat capacity utilization rate.

[0073] For example, the Euler discretization method can be used to differentially discretize the continuous thermal equilibrium model to adapt to the implementation mode of digital protection devices operating according to a fixed calculation cycle, i.e. After sorting, we can obtain ,in, Indicates the calculation period.

[0074] An exponential discrete form based on the analytical solution of a first-order thermal network can be adopted, i.e. Boundary constraints can be applied to the current heat capacity utilization rate to avoid non-physical values ​​caused by sampling disturbances or calculation errors. ,in, This represents the upper limit of heat capacity utilization. It can be set to 1, or a value greater than 1 if it is necessary to retain the ability to characterize overheating.

[0075] These steps not only avoid the problem of accurately characterizing thermal effects based solely on instantaneous current or simple time accumulation, but also simultaneously reflect the comprehensive impact of current load level, historical heat accumulation, and heat dissipation recovery process on the thermal state. This provides a basis with physical consistency, dynamic continuity, and engineering feasibility for subsequent thermal compensation judgment, protection curve generation, and protection parameter correction, helping to improve the accuracy, stability, and adaptability of protection setting results to actual operating conditions.

[0076] In one possible implementation, the self-tuning method for overload long-delay protection characteristics also includes:

[0077] S201, based on the reference current correction factor, correct the current reference current to obtain the first reference current.

[0078] For example, when the protection device is equipped with an ambient temperature acquisition device, the ambient temperature factor can be incorporated into the reference current correction coefficient to reflect the impact of decreased heat dissipation capacity or increased equivalent heat load under high-temperature environments. The current reference current can be corrected based on the temperature correction coefficient. ,in, Indicates the first reference current. This represents the temperature correction factor. Indicates the rated current of the protected object. The value can be determined through table lookup, piecewise function method, or empirical fitting formula method. For example, a correspondence table between ambient temperature and temperature correction coefficient can be established in advance, and the protection device can look up the corresponding value based on the current ambient temperature collected by the ambient temperature acquisition device. .

[0079] S202 calculates the current heat capacity utilization rate through a first-order thermal network based on the current equivalent value, the current thermal time constant, and the first reference current.

[0080] For example, this step is implemented in the same way as steps S210, S220, and S230, simply by replacing the current reference current with the first reference current.

[0081] By introducing a reference current correction factor to correct the current reference current, the current parameter used as the reference for the thermal model is no longer limited to the rated or initial setting value, but can be adaptively adjusted in combination with the current operating condition of the protected object, object differences or external influencing factors, thereby improving the accuracy of the reference current in representing the actual thermal load capacity.

[0082] S300 determines whether the thermal compensation condition is met based on the current heat capacity utilization rate, and performs thermal compensation on the current thermal time constant and the current reference current based on the current heat capacity utilization rate, obtaining the compensated thermal time constant and the compensated reference current. The thermal compensation condition is that the current heat capacity utilization rate is greater than the cold threshold.

[0083] For example, a cold threshold can be preset. (e.g., 20%), used to characterize the boundary point where the protected object transitions from a cold state to a hot state compensation range. When the current heat capacity utilization rate... If the protected object is still in a cold or near-cold state, the heat accumulation formed by the previous test or operation has little impact on the current setting result. At this time, the thermal compensation condition is not met, and the protection device keeps the current thermal time constant and the current reference current unchanged.

[0084] When the current heat capacity utilization rate When this occurs, it indicates that significant heat accumulation has occurred in the protected object, and the previous operating state has affected the current protection capability. At this point, the thermal compensation condition is met, and the protection device initiates the thermal compensation process. To ensure that the compensation amount changes continuously with the thermal state, rather than simply using a fixed correction value, a thermal compensation factor can be constructed based on the current heat capacity utilization rate. ,in, .

[0085] Since the subsequent heat accumulation and dissipation processes of the protected object have changed compared to the cold state when it is in a hot state, in order to make the thermal model more closely reflect the current thermal inertia characteristics, the current thermal time constant is compensated as follows: ,in, This represents the compensated thermal time constant. This represents the thermal time constant compensation coefficient (e.g., 0.05~0.30). This compensation method makes an equivalent correction to the thermal time constant so that the dynamic response of the first-order thermal network under the current thermal state is closer to the actual thermal behavior of the protected object.

[0086] Because the protected object's ability to withstand sustained overload in a hot state is lower than in a cold state, to avoid the protection becoming too slack due to using the cold-state reference, the current reference current compensation method is as follows: ,in, This represents the compensated reference current. This indicates the reference current compensation coefficient (e.g., 0.05~0.25). This compensation method causes the reference current to be adjusted downwards accordingly when the heat capacity utilization rate increases, so as to reflect the decrease in the actual withstand capacity of the protected object under the existing temperature rise conditions.

[0087] This step enables adaptive compensation of the thermal time constant and reference current as the thermal state changes continuously, based on the current thermal capacity utilization rate, providing a parameter basis that is more consistent with the current thermal state for the subsequent generation of protection curves.

[0088] In one possible implementation, please refer to Figure 2 In step S300, based on the current heat capacity utilization rate, thermal compensation is performed on the current thermal time constant and the current reference current to obtain the compensated thermal time constant and the compensated reference current, including:

[0089] S310, based on the current heat capacity utilization rate, performs thermal compensation on the current thermal time constant to obtain the compensated thermal time constant.

[0090] For example, similarly, a thermal compensation factor can be used to thermally compensate (i.e., equivalently correct) the current thermal time constant to obtain the compensated thermal time constant, i.e. Boundary constraints can be set on the compensated thermal time constant to prevent over-compensation. ,in, , These are the lower and upper limits of the allowable range for the thermal time constant, respectively. It can take the value 0.5. ~0.8 , It can take the value 1.2. ~1.5 ,in, The initial thermal time constant can be obtained through experimental calibration (details to follow) or by looking up a table based on the object being protected.

[0091] S320 performs thermal compensation on the first reference current based on the current heat capacity utilization rate to obtain the compensated reference current.

[0092] For example, similarly, a thermal compensation factor can be used to thermally compensate the first reference current to obtain the compensated reference current, i.e. Boundary constraints can be set on the compensated reference current to prevent over-compensation of the thermal time constant, i.e. ,in, , These are the lower and upper limits of the allowable range of the reference current, respectively. It can take the value 0.80. ~0.95 , It can take the value 1.00. ~1.10 .

[0093] By performing thermal compensation on the reference current, the actual load-bearing capacity of the protected object under existing temperature rise conditions can be reflected, thereby making the subsequent protection action threshold closer to the real working conditions. At the same time, by performing equivalent compensation on the thermal time constant, the dynamic response of the thermal model under thermal conditions can be made more consistent with the actual thermal process.

[0094] S400 generates the current protection curve based on the compensated thermal time constant, the compensated reference current, and the current safety factor. The current protection curve is an inverse time characteristic curve of current versus time.

[0095] For example, the current protection curve represents the allowable operating time relationship of the protected object under different overload multiples. The thermal trip initiation current can be calculated based on the compensated reference current and the current safety factor. ,Right now Where K represents the current safety factor, This indicates the starting current threshold calculated from the thermal overload protection curve, when the actual current... When the protected object is within the allowable load range, the protection device does not activate the inverse time delay timing; when the actual current... When the protected object enters the overload range, the protection device calculates the corresponding allowable operating time based on the degree of overload. The ratio of the actual current to the thermal trip initiation current can be calculated, i.e. .

[0096] The time required for the heat capacity utilization rate to evolve from the current state to the operating boundary is related to the thermal time constant and the overload heating intensity. Since the heating intensity is approximately proportional to the square of the current, the current protection curve can be expressed as follows: ,in, This is the allowable operating time corresponding to the actual current I.

[0097] For ease of engineering application and parameter tuning, the current protection curve can also be constructed using a standardized inverse time-limit expression: .

[0098] The corresponding action time can be calculated for multiple discrete current points within a preset current range, and the calculated action time and corresponding current can be stored in a storage unit in the form of a lookup table, a set of function parameters, or a sequence of curve coordinate points. For example, to Select several discrete current points within the interval, and calculate the action time point by point. This allows for the formation of a complete current protection curve. During subsequent operation, the protection device can obtain the allowable operating time based on the real-time detected current through table lookup, interpolation, or direct function calculation, and perform overload protection judgment accordingly.

[0099] The current protection curve can not only reflect the change law of the action time of the protected object under different overload conditions, but also connect with the thermal compensation results, so that the subsequent cold simulation verification and hot simulation verification are based on protection parameters that are more in line with the actual state of the protected object.

[0100] For example, both cold-state and hot-state simulation verifications are numerical simulation verifications executed within the processor of the circuit breaker intelligent controller. During this verification process, the test currents required for verification (such as simulated cold-state test current, simulated preheating current, and simulated hot-state test current) are not physical currents injected into the primary circuit or current sampling circuit through external devices, but rather virtual current calculation values ​​generated internally by the controller, serving as input parameters for the first-order thermal network model. Simultaneously, the action time obtained from the verification is the simulation time length obtained through iterative simulation calculations based on the first-order thermal network model, rather than the actual measured time waiting for the physical tripping mechanism to operate. Through this verification method, the entire self-tuning process can be completed within milliseconds while the circuit breaker is energized, without disconnecting the primary circuit and without affecting the continuity of power supply.

[0101] S500, based on the current protection curve, corrects the compensated reference current and the current safety factor through cold simulation verification to obtain the final reference current and the final safety factor.

[0102] It is understandable that cold-state simulation verification refers to verifying the initial action boundary and inverse time-limit action characteristics of the current protection curve under cold or near-cold conditions, in order to eliminate the interference of residual heat on parameter identification and ensure that the obtained parameters can objectively reflect the protection capability and protection requirements of the protected object under the initial thermal state.

[0103] For example, the current protection curve can be used as a candidate curve, and the current protection curve can be checked at at least one simulated cold test current point. The simulated cold test current point can be set as one or more of the low-multiple overload point, medium-multiple overload point and high-multiple overload point close to the start of thermal action. For example, 1.05 to 1.20 times the thermal action start current (i.e., simulated cold test current) can be selected to check the start action boundary, or several discrete current points can be selected to check the shape of the entire inverse time curve.

[0104] During cold-state simulation verification, a verification environment can be built at the software level, without relying on external current injection or driving physical actuators. This involves calling the discrete iterative formula of the first-order thermal network model, taking the simulated cold-state test current value as input, and executing a step-by-step thermal accumulation simulation calculation starting from the current thermal state (e.g., cold state H=0). When the calculated simulated thermal capacity utilization rate reaches or exceeds a preset tripping threshold (e.g., H=1), the simulation stops, and the product of the number of iterations and the calculation cycle is determined as the cold-state calculation action time. .

[0105] The protection device inputs a simulated cold-state test current into the current protection curve and calculates the theoretical operating time corresponding to that simulated cold-state test current. It can calculate the cold-state calculation action time. Compared with theoretical motion time The deviation between them, i.e. .

[0106] Compensated reference current The current level positioning affects the protection curve, and the current safety factor K affects the start-up boundary and safety margin of the action. The protection device can jointly correct these two factors. That is, it can use a multi-current-point calculation method to comprehensively optimize the compensated reference current and the current safety factor. For example, in multiple simulated cold-state test currents... The theoretical motion time is calculated separately below. Cold-state calculation of action time And construct the comprehensive error function: Where m is the number of simulated cold-state test currents. For the first The weighting coefficients of each simulated cold-state test current are determined. By minimizing the comprehensive error function, the weighting coefficients are... The parameters K are iteratively adjusted until the overall error is less than a preset threshold, or the number of iterations reaches a preset upper limit. The parameters obtained after iteration are the final reference current and the final safety factor. Constraint ranges can be set for the corrected reference current and safety factor to avoid parameter oscillations or deviations from the equipment safety boundary caused by the correction process.

[0107] This step effectively eliminates cold-state deviations that may be introduced during the hot-state compensation process, ensuring that the final reference current and safety factor retain the parameter basis after hot-state compensation while accurately reflecting the protection requirements of the protected object under the initial hot state. At the same time, since the verification process does not rely on external physical testing equipment or long-term physical heating waiting, cold-state simulation verification can be performed online while the circuit breaker is energized, significantly reducing the threshold and cost of engineering implementation, and thus providing a stable and reliable parameter basis for subsequent hot-state simulation verification and correction of the thermal time constant.

[0108] In one possible implementation, S500, based on the current protection curve, corrects the compensated reference current and the current safety factor through cold-state simulation verification to obtain the final reference current and the final safety factor, including:

[0109] S510, Cold-state verification step: Based on the compensated reference current and the compensated thermal time constant, perform cold-state simulation verification to obtain the cold-state calculation action time. Specifically, the cold-state simulation verification involves calling a first-order thermal network, using the simulated cold-state test current as input, and performing iterative calculations of thermal accumulation simulation until the simulated heat capacity utilization rate reaches the tripping threshold. The simulated cold-state test current is N times the compensated reference current, and the cold-state calculation action time is the simulation time length from the start of the simulation to reaching the tripping threshold.

[0110] For example, the simulated cold-state test current can be N times the compensated reference current, where N>1. It can be preset to a value between 1.1 and 2.0 based on the verification accuracy requirements and the type of protected object. , This represents the simulated cold-state test current.

[0111] The discretized first-order thermal network can be invoked, starting with the initial value of heat capacity utilization (e.g., H=0 in the cold state), and using the simulated cold-state test current as a constant input, according to the calculation cycle. Perform iterative calculations of thermal accumulation simulation step by step: The simulation terminates when the calculated heat capacity utilization rate H reaches or exceeds the preset tripping threshold (e.g., H≥1) for the first time. The simulation time from the start of the simulation to reaching the tripping threshold can be taken as the cold-state calculation action time. .

[0112] S520, Cold-state theoretical operating time determination steps: Based on the current protection curve and simulated cold-state test current, determine the cold-state theoretical operating time.

[0113] For example, the cold test current can be used. Substituting the values ​​into the calculation formula for the current protection curve, the cold-state theoretical action time is calculated, i.e. ,in, ,or .

[0114] S530, Cold Error Calculation Steps: Calculate the cold error based on the cold calculated action time and the cold theoretical action time.

[0115] For example, cold-state error can be expressed in the form of absolute error, relative error, or percentage error. Here, the relative error form is used, that is... ,in, This indicates the cold-state error.

[0116] S540, Cold State Judgment Steps: If the cold state error is less than or equal to the error threshold, the compensated reference current is determined as the final reference current, and the current safety factor is determined as the final safety factor.

[0117] For example, cold-state error With error threshold In comparison, if This indicates that the protection curve under the current parameter conditions can well reflect the actual protection characteristics under cold conditions. Therefore, the compensated reference current can be determined as the final reference current. The current safety factor is determined as the final safety factor, that is... .

[0118] For protection systems with high precision requirements, the error threshold It can be set to 1%~3%, which helps the protection device accurately reflect the load-bearing capacity of the equipment under cold conditions; for general applications, the error threshold... It can be set to 3%~5%, providing higher fault tolerance while ensuring protection performance.

[0119] In subsequent iterations, the cold-state error of each iteration will be... With error threshold In comparison, if The reference current and safety factor of this iteration (i.e., the reference current and safety factor corrected in the previous iteration) can be determined as the final reference current and final safety factor.

[0120] S550, Cold-state correction steps: If the cold-state error is greater than the error threshold, the compensated reference current is corrected according to the cold-state error to obtain the corrected reference current, and the current safety factor is corrected according to the cold-state error to obtain the corrected safety factor.

[0121] For example, if This indicates that the current protection curve still has a significant deviation under cold-state conditions. The cold-state error can be used as a basis for further analysis. The reference current is corrected (the first correction uses the compensated reference current). Subsequent corrections will use the corrected reference current from the previous iteration, i.e. ,in, Indicates the first The reference current after the next iteration correction. Show the first The reference current after the next iteration correction. Indicates the first Cold state error of the next iteration.

[0122] Based on cold state error The safety factor is adjusted (the first adjustment uses the current safety factor K, and subsequent adjustments use the safety factor adjusted in the previous iteration), that is... ,in, Indicates the first The safety factor after the next iteration. Show the first The safety factor after the next iteration.

[0123] S560 involves iterative cold-state verification, cold-state theoretical action time determination, cold-state error calculation, cold-state judgment, and cold-state correction steps until the cold-state convergence condition is met. The cold-state convergence condition is that the cold-state error is less than or equal to the error threshold, and the number of iterations is less than or equal to the maximum number of iterations.

[0124] For example, after the above corrections are completed, the protection device can generate a new current protection curve based on the corrected reference current and the corrected safety factor, and then re-execute the cold-state verification step, the cold-state theoretical operating time determination step, the cold-state error calculation step, the cold-state judgment step, and the cold-state correction step, forming an iterative verification process until the cold-state convergence condition is met. The cold-state convergence condition is... and ,in, Indicates the maximum number of iterations (e.g., 3 times).

[0125] The above iterative optimization process can effectively eliminate the impact of residual heat or initial setting deviation, which is beneficial to the accuracy and reliability of protection parameters in the cold state, improves the adaptability of protection devices to different operating conditions, thereby optimizing the protection performance of the equipment and reducing the risk of malfunction.

[0126] S600, based on the final reference current, corrects the compensated thermal time constant through thermal simulation verification to obtain the final thermal time constant.

[0127] It is understandable that thermal simulation verification is used to check the consistency between the actual thermal response process and the theoretical thermal response process of the protected object as it continues to develop from the current thermal state to the protection action boundary under existing thermal accumulation conditions, thereby correcting the thermal time constant to a parameter that is more in line with the characteristics of thermal operation.

[0128] For example, the initial value of the simulated heat capacity utilization rate can be set as the target heat capacity utilization rate (e.g., 0.7~0.9). The simulated hot-state test current is used as the input of the first-order thermal network. The heat accumulation simulation is iterated through the first-order thermal network until the simulated heat capacity utilization rate reaches the tripping threshold. The product of the number of iterations in the second stage of simulation and the calculation cycle is determined as the hot-state calculation action time. The simulated hot-state test current can be the current point corresponding to several overload multiples of the final reference current. ,in, To simulate the hot test current, To simulate the multiple of the hot-state test current, One or more of 1.1, 1.2, 1.5, and 2.0 can be selected to verify the thermal response characteristics under different thermal overload ranges.

[0129] The theoretical operating time can be calculated based on the target heat capacity utilization rate and the current protection curve. ,Right now The deviation between the theoretical action time and the thermally calculated action time is calculated. .

[0130] The thermal time constant determines the time scale of the inverse time-limit curve, and the compensated thermal time constant can be corrected based on the time deviation. ,in, This represents the thermal time constant after the first correction. This represents the step size coefficient for thermal time constant correction. Similarly, verification can be repeated under multiple hot-state test currents, and a comprehensive error function can be constructed to iteratively optimize the compensated thermal time constant. Boundary constraints can be applied to the corrected thermal time constant to prevent excessive deviation of the thermal time constant correction from the actual thermal inertia range of the protected object.

[0131] Repeat the above correction steps until the parameter changes in two adjacent iterations satisfy the following conditions: ,,in, The thermal time constant convergence threshold (e.g., 5~10) indicates that the thermal simulation verification correction is complete and the final thermal time constant is obtained.

[0132] By using the results of thermal simulation to correct the compensated thermal time constant, the final thermal time constant no longer depends solely on the initial set value or the simple compensation result, but can be determined by combining the simulation response characteristics of the protected object under thermal conditions. The final thermal time constant can more accurately characterize the thermal inertia law of the protected object under continuous operation, temperature rise accumulation and residual heat, thereby improving the authenticity, stability and adaptability of the protection curve generation and action criteria under thermal conditions.

[0133] In one possible implementation, S600, based on the final reference current, corrects the compensated thermal time constant through thermal simulation verification to obtain the final thermal time constant, including:

[0134] S610, Hot-state verification step: Based on the final reference current and the compensated thermal time constant, perform hot-state simulation verification to obtain the hot-state calculation action time. Specifically, the hot-state simulation verification involves calling the first-order thermal network, setting the initial value of the simulated heat capacity utilization rate as the target heat capacity utilization rate, and using the simulated hot-state test current as input to perform iterative calculations of heat accumulation simulation until the simulated heat capacity utilization rate reaches the tripping threshold. The simulated hot-state test current is N times the final reference current, and the hot-state calculation action time is the simulation time length from the start of the simulation to reaching the tripping threshold.

[0135] For example, the target heat capacity utilization rate can be set between 0.7 and 0.9, indicating that the protection device has withstood a sufficient heat load for a certain period of time, approaching but not exceeding its maximum heat capacity, to simulate the protection device being in a reasonable heat accumulation state. The simulated hot-state test current can be N times the final reference current, where N>1, and can be preset to a value between 1.1 and 2.0 according to the verification accuracy requirements and the type of protected object. , (This represents the simulated hot test current).

[0136] The initial value of the simulated heat capacity utilization rate can be set as the target heat capacity utilization rate (e.g., H=0.8) to simulate the thermal state of the protected object after a preheating process. The simulated hot-state test current is used as a constant input to the discretized first-order thermal network, and heat accumulation simulation iterative calculation is performed until the simulated heat capacity utilization rate reaches the tripping threshold (e.g., H≥1), at which point the simulation terminates. The simulation time from the start of the simulation to reaching the tripping threshold can be used as the hot-state calculation action time. .

[0137] S620, hot-state theoretical operating time determination steps: Calculate the hot-state theoretical operating time based on the final reference current, simulated hot-state test current, compensated thermal time constant, and current protection curve.

[0138] For example, the thermal theory action time This is the theoretical time required for the protection device to execute a protection action (i.e., when the heat capacity utilization rate reaches 1) after monitoring and reaching the target heat capacity utilization rate. The ideal thermal action time can be calculated based on the current protection curve. ,in, , Indicates the target heat capacity utilization rate, or .

[0139] S630, Hot-state error calculation steps: Calculate the hot-state error based on the hot-state calculated action time and the hot-state theoretical action time.

[0140] For example, thermal error can also be expressed in the form of relative error, i.e. ,in, This indicates thermal error.

[0141] S640, Hot state judgment step: If the hot state error is less than or equal to the error threshold, the compensated thermal time constant is determined as the final thermal time constant.

[0142] For example, thermal error can be... With error threshold In comparison, if This indicates that the current protection curve can well meet the requirements of hot-state protection, and the compensated thermal time constant is determined as the final thermal time constant, i.e. .

[0143] In subsequent iterations, the thermal error of each iteration will be... With error threshold In comparison, if The thermal time constant of this iteration (i.e., the thermal time constant corrected in the previous iteration) can be determined as the final thermal time constant.

[0144] S650, Hot-state correction step: If the hot-state error is greater than the error threshold, the compensated thermal time constant is corrected according to the hot-state error to obtain the corrected thermal time constant.

[0145] For example, if This indicates that the current protection curve deviates under hot conditions. The hot error can be used to determine this. The thermal time constant is corrected (the first correction uses the compensated thermal time constant). Subsequent corrections use the corrected thermal time constant from the previous iteration, i.e. ,in, Indicates the first The thermal time constant after the next iteration. Show the first The thermal time constant after the next iteration. Indicates the first The thermal error of the next iteration.

[0146] S660 involves iterative hot-state verification, hot-state theoretical action time determination, hot-state error calculation, hot-state judgment, and hot-state correction steps until the hot-state convergence condition is met. The hot-state convergence condition is that the hot-state error is less than or equal to the error threshold, and the number of iterations is less than or equal to the maximum number of iterations.

[0147] For example, after the thermal correction is completed, the thermal verification, thermal theoretical action time calculation, thermal error calculation, thermal judgment, and thermal correction steps are re-executed based on the corrected thermal time constant until the thermal convergence condition is met. The thermal convergence condition is... and .

[0148] The final reference current and the final thermal time constant can be updated into the thermal capacity utilization rate calculation formula. The protection device can calculate the thermal capacity utilization rate of the protected object in real time according to the updated thermal capacity utilization rate calculation formula. When the thermal capacity utilization rate reaches the thermal limit (H=1), the protection device will perform protection action.

[0149] By iteratively optimizing and correcting the thermal time constant, the thermal error is kept within a reasonable range, thereby improving the accuracy and reliability of the protection device under thermal conditions. It can adapt to actual thermal operating conditions, accurately adjust protection parameters, and ensure that the protection performance under different thermal conditions meets the safety requirements of the protected object, avoids false operation or failure to operate, and improves the protection reliability of the protected object.

[0150] In one possible implementation, the self-tuning method for overload long-delay protection characteristics also includes:

[0151] S10, if the current heat capacity utilization rate is less than or equal to the cold threshold, generate the first protection curve based on the current thermal time constant, the current reference current and the current safety factor.

[0152] For example, when the current heat capacity utilization rate At this time, without thermal compensation, the current thermal time constant, current reference current, and current safety factor can be directly used to generate the first protection curve, i.e. ,in, .

[0153] S20, based on the first protection curve, corrects the current reference current and the current safety factor through cold simulation verification to obtain the final reference current and the final safety factor.

[0154] For example, the implementation process of this step is the same as that of step S500, and will not be repeated here.

[0155] S30, based on the final reference current, corrects the current thermal time constant through thermal simulation verification to obtain the final thermal time constant.

[0156] For example, the implementation process of this step is the same as that of step S600, and will not be repeated here.

[0157] By determining the thermal state of the protection device based on whether the current heat capacity utilization rate is less than or equal to the cold-state threshold, the protection requirements of the protected object under different thermal states can be effectively distinguished. When the current heat capacity utilization rate is less than or equal to the cold-state threshold, the protection device can generate a first protection curve based on the current thermal time constant, the current reference current, and the current safety factor. This helps to make the protection characteristics more accurate under cold or near-cold conditions, avoiding overcompensation caused by heat accumulation. When the heat capacity utilization rate is greater than the cold-state threshold, the protection device further corrects the reference current and safety factor through cold-state simulation verification, enabling the protection device to accurately adapt to hot conditions and avoiding the overly conservative influence of excessively low reference current and safety factor. In this way, a smooth transition between cold and hot states can be achieved, thereby improving the adaptability and protection accuracy of the protection device under various operating states.

[0158] In one possible implementation, the self-tuning method for overload long-delay protection characteristics also includes:

[0159] S2001, Obtain the current ambient temperature and calculate the current allowable temperature rise based on the current ambient temperature and the maximum allowable temperature. The maximum allowable temperature is the highest temperature the protected object is allowed to reach. S2002, Calculate the maximum allowable temperature rise based on the maximum allowable temperature and the reference ambient temperature. S2003, Calculate the reference current correction factor based on the current allowable temperature rise and the maximum allowable temperature rise.

[0160] For example, the current ambient temperature can be collected using an ambient temperature acquisition device. The maximum permissible temperature is the highest temperature that the protected object is allowed to reach. For instance, the maximum permissible temperature for Class B insulation windings of a motor is 130°C, and the maximum permissible temperature for Class F insulation of a motor is even higher; the maximum permissible temperature for XLPE insulation of a cable is 90°C.

[0161] The current allowable temperature rise can be calculated based on the current ambient temperature and the maximum allowable temperature. ,in, This indicates the current permissible temperature rise. Indicates the maximum permissible temperature. This indicates the current ambient temperature.

[0162] Heat capacity utilization rate H can be defined as ,in, This indicates the current actual temperature rise of the protected object. This indicates the current temperature of the protected object.

[0163] The reference ambient temperature can be set to 40°C. The maximum allowable temperature rise can be calculated based on the maximum allowable temperature and the reference ambient temperature. This indicates that the rated current is applied at the reference ambient temperature. At that time, the steady-state temperature rise of the protected object.

[0164] At steady-state thermal equilibrium, the heating power and The heat dissipation power is directly proportional to the temperature rise. Proportional, therefore in steady state we have ,but For any current I, then It can be Substitution In the middle, we get The purpose of the reference current correction factor is to correct the reference current so that when the current equals the corrected reference current, the protected object reaches its thermal limit H=1. This formula can be used to obtain the relationship between the reference current and the rated current, that is... Due to the reference current correction factor ,So .

[0165] The calculation formula for the above-mentioned reference current correction factor may result in a value greater than 1. That is, when operating at rated current under reference ambient temperature, the thermal limit will not be reached exactly, but rather a margin will be left: Therefore, a reference heat capacity utilization rate can be introduced. This makes the reference current correction factor .

[0166] The above steps take into account the impact of external ambient temperature changes on the thermal load of the protected object, which helps the protected object to operate reliably in various environments, avoids protection failure caused by overload or overheating, and thus improves the adaptability of the protection device and the safety of the protected object.

[0167] In one possible implementation, the self-tuning method for overload long-delay protection characteristics also includes:

[0168] S301, Obtain the experimental action time and current sequence; where the experimental action time is the time from the stabilization of the experimental test current to the execution of the protection action, and the experimental test current is N times the current reference current; S302, Based on the experimental action time, current sequence and first-order thermal network, solve the initial thermal time constant by the bisection method.

[0169] For example, the initial thermal time constant can be tested during the factory testing or offline testing phase of the circuit breaker intelligent controller. On an offline test bench, the circuit breaker intelligent controller is connected to a standard current source, and a current of 1.2 to 2.0 times the rated current can be selected. As an experimental test current, an experimental test current can be input to the protection device. Timing starts when the test current stabilizes and reaches the set value, and stops when the protection device performs a protection action (such as tripping). The actual action time is recorded. (Experimental action time) and current sequence The test can be repeated 2-3 times, and the median or average value can be taken to ensure data reliability.

[0170] The heat capacity utilization rate calculation formula after differential separation in step S230 can be used, i.e. If the experimental test current is constant, the analytical solution can be used to solve it directly. ,Right now ,in, , Indicates the experimental test current, reference current. It can be the rated current. Or the current after correction by the reference current correction factor It can be based on the actual action time and experimental test current ,calculate ,Right now .

[0171] If the experimental test current is not constant, the bisection method can be used to solve it: [The following is a possible interpretation:] ... Search scope (e.g., [50s, 1200s]); Can be taken Using the above discretization calculation formula For current sequences Integrate and calculate the simulated motion time. ;like Then the current Too small, can Equal to the current ;like Then the current Too large, can Equal to the current Iterate the above process until... ,in, This represents the convergence threshold (e.g., 1 second), and the final result is... The initial thermal time constant .

[0172] Different experimental test currents (e.g., 1.2 times) can be applied multiple times. and 1.5 times ), calculate the corresponding thermal time constants respectively, and take the median or weighted average as the final initial thermal time constant. To improve robustness.

[0173] The initial thermal time constant obtained from offline calibration can be written into the non-volatile memory (such as EEPROM or Flash) of the circuit breaker intelligent controller. During the field operation phase, in response to the setting signal, the controller reads the initial thermal time constant from the memory as the initial value of the current thermal time constant, which is then used in subsequent thermal capacity utilization calculations and self-tuning processes.

[0174] By limiting the calibration of the initial thermal time constant to the offline stage, the basic parameters can be accurately obtained by taking advantage of the convenient conditions of the test bench. On the other hand, the risk of power interruption and operational complexity caused by physical overload testing during on-site operation with power is avoided, which further improves the feasibility and convenience in practical engineering applications.

[0175] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0176] Corresponding to the overload long delay protection characteristic self-tuning method described in the above embodiments, this application also provides an overload long delay protection characteristic self-tuning device, the various units of which can implement the various steps of the overload long delay protection characteristic self-tuning method. Figure 3 The diagram shows a structural block diagram of the overload long delay protection characteristic self-tuning device provided in the embodiments of this application. For ease of explanation, only the parts related to the embodiments of this application are shown.

[0177] Reference Figure 3 The device includes:

[0178] The acquisition unit is used to acquire the equivalent current value, the current thermal time constant, the current reference current, and the current safety factor in response to the setting signal. The thermal time constant is used to control the rate of heat accumulation and dissipation.

[0179] The heat capacity utilization calculation unit is used to calculate the current heat capacity utilization rate through a first-order thermal network based on the current equivalent value, the current thermal time constant, and the current reference current.

[0180] The compensation unit is used to determine the conditions for thermal compensation based on the current heat capacity utilization rate, and to perform thermal compensation on the current thermal time constant and the current reference current based on the current heat capacity utilization rate, thereby obtaining the compensated thermal time constant and the compensated reference current. The thermal compensation condition is that the current heat capacity utilization rate is greater than the cold threshold.

[0181] The protection curve generation unit is used to generate the current protection curve based on the compensated thermal time constant, the compensated reference current, and the current safety factor. The current protection curve is an inverse time characteristic curve of current versus time.

[0182] The cold-state verification unit is used to correct the compensated reference current and the current safety factor based on the current protection curve through cold-state simulation verification, so as to obtain the final reference current and the final safety factor.

[0183] The thermal verification unit is used to correct the compensated thermal time constant based on the final reference current through thermal simulation verification, so as to obtain the final thermal time constant.

[0184] It should be noted that the information interaction and execution process between the above-mentioned units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, which will not be repeated here.

[0185] This application also provides an intelligent circuit breaker controller. Figure 4 and Figure 5 These are schematic diagrams illustrating two different structures of the intelligent circuit breaker controller provided in this application. The intelligent circuit breaker controller includes a current acquisition device, an ambient temperature acquisition device, a protection execution device, and a control device communicatively connected to the current acquisition device, the ambient temperature acquisition device, and the protection execution device. Figure 4 As shown, the control device 6 of the circuit breaker intelligent controller in this embodiment includes: at least one processor 60 ( Figure 4 Only one is shown in the image), at least one memory 61 ( Figure 4 (Only one is shown in the image) and a computer program 62 stored in the at least one memory 61 and executable on the at least one processor 60. When the processor 60 executes the computer program 62, it causes the circuit breaker intelligent controller to implement the steps in any of the above-described overload long-delay protection characteristic self-tuning method embodiments, or causes the circuit breaker intelligent controller to implement the functions of each unit in the above-described device embodiments.

[0186] For example, the computer program 62 may be divided into one or more modules / units, which are stored in the memory 61 and executed by the processor 60 to complete this application. The one or more modules / units may be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program 62 in the control device 6 of the circuit breaker intelligent controller.

[0187] The control device 6 of the circuit breaker intelligent controller can be a microcontroller (MCU), digital signal processor (DSP), ARM processor / embedded processor, FPGA or CPLD, PLC control unit, SoC control platform, etc. The circuit breaker intelligent controller may include, but is not limited to, a processor 60 and a memory 61. Those skilled in the art will understand that... Figure 4 This is merely an example of a circuit breaker intelligent controller and does not constitute a limitation on the circuit breaker intelligent controller. It may include more or fewer components than shown in the figure, or combine certain components, or different components, such as input / output devices, network access devices, buses, etc.

[0188] The processor 60 can be a Central Processing Unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0189] In some embodiments, the memory 61 may be an internal storage unit of the control device 6 of the circuit breaker intelligent controller, such as the hard disk or memory of the circuit breaker intelligent controller. In other embodiments, the memory 61 may be an external storage device of the circuit breaker intelligent controller, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the circuit breaker intelligent controller. Furthermore, the memory 61 may include both internal storage units and external storage devices of the circuit breaker intelligent controller. The memory 61 is used to store operating systems, applications, bootloaders, data, and other programs, such as the program code of computer programs. The memory 61 can also be used to temporarily store data that has been output or will be output.

[0190] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0191] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A self-tuning method for overload long-delay protection characteristics, characterized in that, include: In response to the setting signal, the equivalent current value, the current thermal time constant, the current reference current, and the current safety factor are obtained; among them, the thermal time constant is used to control the rate of heat accumulation and heat dissipation. The current heat capacity utilization rate is calculated using a first-order thermal network based on the current equivalent value, the current thermal time constant, and the current reference current. Based on the current heat capacity utilization rate, it is determined that the thermal compensation condition is met, and based on the current heat capacity utilization rate, thermal compensation is performed on the current thermal time constant and the current reference current to obtain the compensated thermal time constant and the compensated reference current; wherein, the thermal compensation condition is that the current heat capacity utilization rate is greater than the cold threshold. Based on the compensated thermal time constant, the compensated reference current, and the current safety factor, a current protection curve is generated; wherein, the current protection curve is an inverse time characteristic curve of current versus time. Based on the current protection curve, the compensated reference current and the current safety factor are corrected through cold simulation verification to obtain the final reference current and the final safety factor. Based on the final reference current, the compensated thermal time constant is corrected through thermal simulation to obtain the final thermal time constant. Based on the current protection curve, the compensated reference current and the current safety factor are corrected through cold-state simulation verification to obtain the final reference current and the final safety factor, including: Cold-state verification steps: Based on the compensated reference current and the compensated thermal time constant, perform cold-state simulation verification to obtain the cold-state calculation action time; wherein, the cold-state simulation verification involves calling the first-order thermal network, using the simulated cold-state test current as input, and performing thermal accumulation simulation iterative calculation until the simulated heat capacity utilization rate reaches the tripping threshold, the simulated cold-state test current is N times the compensated reference current, and the cold-state calculation action time is the simulation time length from the start of the simulation to reaching the tripping threshold; Cold-state theoretical operating time determination steps: Based on the current protection curve and the simulated cold-state test current, determine the cold-state theoretical operating time; Cold state error calculation steps: Calculate the cold state error based on the calculated cold state action time and the theoretical cold state action time; Cold state judgment step: If the cold state error is less than or equal to the error threshold, the compensated reference current is determined as the final reference current, and the current safety factor is determined as the final safety factor; Cold state correction step: If the cold state error is greater than the error threshold, the compensated reference current is corrected according to the cold state error to obtain the corrected reference current, and the current safety factor is corrected according to the cold state error to obtain the corrected safety factor; The process involves iterative cold-state verification, cold-state theoretical action time determination, cold-state error calculation, cold-state judgment, and cold-state correction steps until the cold-state convergence condition is met. The cold-state convergence condition is that the cold-state error is less than or equal to the error threshold, and the number of iterations is less than or equal to the maximum number of iterations.

2. The self-tuning method for overload long-delay protection characteristics as described in claim 1, characterized in that, The step of calculating the current heat capacity utilization rate through a first-order thermal network based on the current equivalent value, the current thermal time constant, and the current reference current includes: Calculate the per-unit value of the current based on the current equivalent value and the current reference current; Based on the per-unit current value, the current thermal time constant, and the first-order thermal network, a continuous thermal equilibrium model is constructed. Differential discretization is performed on the continuous thermal balance model to obtain the current heat capacity utilization rate.

3. The self-tuning method for overload long-delay protection characteristics as described in claim 1, characterized in that, The method further includes: The current reference current is corrected according to the reference current correction factor to obtain the first reference current; The current heat capacity utilization rate is calculated using a first-order thermal network based on the current equivalent value, the current thermal time constant, and the first reference current.

4. The self-tuning method for overload long-delay protection characteristics as described in claim 3, characterized in that, The step of performing thermal compensation on the current thermal time constant and the current reference current based on the current heat capacity utilization rate to obtain the compensated thermal time constant and the compensated reference current includes: Based on the current heat capacity utilization rate, thermal compensation is performed on the current thermal time constant to obtain the compensated thermal time constant; Based on the current heat capacity utilization rate, thermal compensation is performed on the first reference current to obtain the compensated reference current.

5. The self-tuning method for overload long-delay protection characteristics as described in claim 1, characterized in that, The process of correcting the compensated thermal time constant based on the final reference current through thermal simulation to obtain the final thermal time constant includes: Hot-state verification steps: Based on the final reference current and the compensated thermal time constant, perform hot-state simulation verification to obtain the hot-state calculation action time; wherein, the hot-state simulation verification involves calling the first-order thermal network, setting the initial value of the simulated heat capacity utilization rate as the target heat capacity utilization rate, and using the simulated hot-state test current as input to perform thermal accumulation simulation iterative calculation until the simulated heat capacity utilization rate reaches the tripping threshold, wherein the simulated hot-state test current is N times the final reference current, and the hot-state calculation action time is the simulation time length from the start of the simulation to reaching the tripping threshold; The steps for determining the theoretical operating time under hot conditions are as follows: Calculate the theoretical operating time under hot conditions based on the final reference current, the simulated hot-condition test current, the compensated thermal time constant, and the current protection curve. Hot-state error calculation steps: Calculate the hot-state error based on the calculated hot-state action time and the theoretical hot-state action time; Hot state determination step: If the hot state error is less than or equal to the error threshold, the compensated thermal time constant is determined as the final thermal time constant; Hot-state correction step: If the hot-state error is greater than the error threshold, the compensated thermal time constant is corrected according to the hot-state error to obtain the corrected thermal time constant; The process involves iterative hot-state verification, hot-state theoretical action time determination, hot-state error calculation, hot-state judgment, and hot-state correction steps until the hot-state convergence condition is met. The hot-state convergence condition is that the hot-state error is less than or equal to the error threshold, and the number of iterations is less than or equal to the maximum number of iterations.

6. The self-tuning method for overload long-delay protection characteristics as described in claim 1, characterized in that, The method further includes: If the current heat capacity utilization rate is less than or equal to the cold state threshold, a first protection curve is generated based on the current thermal time constant, the current reference current, and the current safety factor. Based on the first protection curve, the current reference current and the current safety factor are corrected through cold simulation verification to obtain the final reference current and the final safety factor; Based on the final reference current, the current thermal time constant is corrected through thermal simulation to obtain the final thermal time constant.

7. The self-tuning method for overload long-delay protection characteristics as described in claim 3, characterized in that, The method further includes: Obtain the current ambient temperature, and calculate the current allowable temperature rise based on the current ambient temperature and the maximum allowable temperature; wherein, the maximum allowable temperature is the highest temperature that the protected object is allowed to reach; Calculate the maximum allowable temperature rise based on the maximum allowable temperature and the reference ambient temperature; The reference current correction factor is calculated based on the current allowable temperature rise and the maximum allowable temperature rise.

8. The self-tuning method for overload long-delay protection characteristics as described in claim 1, characterized in that, The method further includes: Obtain the experimental action time and current sequence; wherein, the experimental action time is the time from the stabilization of the experimental test current to the execution of the protection action, and the experimental test current is N times the current reference current; Based on the experimental action time, the current sequence, and the first-order thermal network, the initial thermal time constant is solved using the bisection method.

9. A circuit breaker intelligent controller, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1 to 8.

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