Ground fault protection system for low voltage it power supply systems

Abstract

The present application relates to the technical field of electrical safety monitoring, in particular to a leakage protection system for low-voltage IT power supply system. The leakage protection system comprises an impedance spectrum identification unit, which is used to construct an original spectrum data set; based on the original spectrum data set, the system calculates the complex impedance spectrum to ground; and based on the complex impedance spectrum to ground, the system decouples out the real insulation resistance and the system capacitance to ground by applying a parallel RC equivalent circuit model; a dynamic assessment unit, which is used to construct an insulation health index; the system calculates a structure change factor; a trend prediction unit, which is used to calculate an insulation aging rate based on a time series formed by historical real insulation resistance data; a comprehensive risk decision unit, which is used to calculate a comprehensive risk index; and in response to the insulation health index exceeding a preset final protection limit value, the system outputs a trip signal. The present application solves the false alarm problem caused by the traditional protection device being unable to distinguish between resistive and capacitive leakage current, and significantly improves the accuracy of protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical safety monitoring, in particular to a leakage protection system for low-voltage IT power supply system. BACKGROUND

[0002] With the increasing application of low-voltage IT power supply system in critical fields such as medical treatment, data center and precision manufacturing, the requirements for power supply continuity and safety are also increasing. In modern IT systems, the use of a large number of nonlinear loads and variable frequency devices, as well as the increasing complexity of system network topology, leads to a significant increase in the capacitive component of the system to ground, which poses a serious challenge to traditional insulation monitoring technology.

[0003] The conventional leakage protection device mainly monitors the instantaneous value of the total ground leakage current or insulation resistance and compares it with a fixed threshold to achieve protection. However, this traditional method has its inherent technical limitations. It cannot effectively distinguish between resistive leakage current caused by real insulation aging or damage and capacitive leakage current generated by system inherent cables, filters, etc. In systems with large capacitive components, capacitive leakage current may dominate, thus masking the real insulation state.

[0004] This confusion directly leads to two major problems: one is false alarm, that is, the system insulation state is good, but the large capacitive leakage current makes the total leakage current exceed the alarm threshold, causing unnecessary shutdown for maintenance and affecting the continuity of power supply; the other is missed alarm, that is, the insulation has begun to deteriorate slowly, but the resistive leakage current component has not caused significant changes in the total leakage current, so the system cannot discover the potential risk in time. In addition, the alarm mechanism relying on a single threshold is a post-response, lacking the ability to analyze and predict the insulation aging trend, and cannot realize predictive maintenance.

[0005] Therefore, how to accurately identify the real insulation resistance of the system, exclude the interference of the system ground capacitance, and conduct forward-looking comprehensive risk assessment combined with the aging trend to overcome the false and missed alarm problems of the traditional method has become a technical problem to be solved in the field. SUMMARY

[0006] To solve the above technical problems, the present application discloses a leakage protection system for low-voltage IT power supply system, in particular, the technical scheme of the present application is:

[0007] The leakage protection system for low-voltage IT power supply system comprises:

[0008] an impedance spectrum identification unit configured to inject a preset composite voltage signal and collect a total ground leakage current response to construct an original spectrum dataset, calculate a system ground complex impedance spectrum based on the original spectrum dataset, and decouple out a real insulation resistance and a system ground capacitance based on the system ground complex impedance spectrum and a parallel RC equivalent circuit model;

[0009] a dynamic evaluation unit configured to construct an insulation health index based on the real insulation resistance and a preset insulation resistance alarm limit value, and calculate a system structure change factor based on the system ground capacitance and a preset capacitance reference benchmark value;

[0010] a trend prediction unit configured to calculate an insulation aging rate based on a time series formed by historical real insulation resistance data;

[0011] a comprehensive risk decision unit configured to perform weighted fusion of the insulation health index, the system structure change factor, and the insulation aging rate to calculate a comprehensive risk index, perform graded early warning based on the comprehensive risk index, and output a trip signal in response to the insulation health index exceeding a preset final protection limit value.

[0012] Preferably, the impedance spectrum identification unit calculates the system ground complex impedance spectrum by:

[0013] calculating the injected voltage and the total ground leakage current response at each frequency point in the original spectrum dataset to generate complex impedance values containing equivalent resistance and equivalent reactance, and form the system ground complex impedance spectrum based on the complex impedance values and a complex ohm law.

[0014] Preferably, the impedance spectrum identification unit decouples out the real insulation resistance and the system ground capacitance by:

[0015] determining the real insulation resistance and the system ground capacitance values by a numerical optimization algorithm to minimize the error sum of squares between a theoretical impedance calculated based on the values and the system ground complex impedance spectrum based on a least square optimization model.

[0016] Preferably, the dynamic evaluation unit calculates the insulation health index by dividing the preset insulation resistance alarm limit value by the real insulation resistance.

[0017] Preferably, the dynamic evaluation unit calculates the system structure change factor by calculating a difference between the system ground capacitance and the preset capacitance reference benchmark value, and dividing the difference by the capacitance reference benchmark value.

[0018] Preferably, the dynamic evaluation unit is further configured to:

[0019] In response to the system structure change factor continuously exceeding the preset capacitance fluctuation limit for a preset time length, it is prompted to update the capacitance reference reference value, and in response to a confirmation instruction, the new stable capacitance value is used to update the capacitance reference reference value.

[0020] Preferably, the trend prediction unit calculates the relative loss rate of insulation resistance per unit time by processing the real insulation resistance time series in the preset time window to obtain the insulation aging rate.

[0021] Preferably, the process of calculating the comprehensive risk index by the comprehensive risk decision unit comprises:

[0022] The insulation health index, the system structure change factor normalized by the preset capacitance fluctuation limit, and the insulation aging rate normalized by the preset aging rate threshold are multiplied by the corresponding preset weight coefficients and summed to obtain the comprehensive risk index.

[0023] Preferably, the process of executing graded early warning by the comprehensive risk decision unit comprises:

[0024] When the comprehensive risk index is lower than the first warning threshold, it is determined to be in a normal state;

[0025] When the comprehensive risk index reaches the first warning threshold but is lower than the second warning threshold, a level of attention prompt is triggered;

[0026] When the comprehensive risk index is not lower than the second warning threshold, a warning level alarm is triggered.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] 1、The present application effectively eliminates the capacitive leakage current interference generated by the system-to-ground capacitance by accurately decoupling the real insulation resistance, solves the false alarm problem caused by the traditional protection device due to the inability to distinguish between resistive and capacitive leakage current, and significantly improves the accuracy of protection.

[0029] 2、The present application quantifies the insulation aging rate based on historical data of real insulation resistance, realizes the forward-looking prediction of the deterioration trend of insulation performance, and changes the traditional passive response after failure into proactive early warning, providing a decision basis for predictive maintenance.

[0030] 3、The present application integrates information in three dimensions of real-time insulation state, system structure stability and future aging trend to form a comprehensive risk assessment index, overcoming the one-sidedness of relying on a single fixed threshold for judgment, making the risk assessment more comprehensive and stereoscopic, and the decision more reliable.

[0031] 4、The application establishes a control strategy combining hierarchical early warning and final tripping protection, which can trigger responses of different levels according to the severity of the risk, provides clear operation guidance for operation and maintenance personnel, ensures absolute safety in the event of extreme deterioration, and thus comprehensively improves the safety, continuity and operation and maintenance efficiency of the power supply system. BRIEF DESCRIPTION OF DRAWINGS

[0032] The application will be further explained in conjunction with the accompanying drawings and embodiments:

[0033] Figure 1 is a flow chart of the system of the application. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions and advantages of the application clearer and more apparent, the application will be further described in detail below in conjunction with specific embodiments.

[0035] Embodiment 1:

[0036] Please refer to Figure 1 , a leakage protection system for a low-voltage IT power supply system, comprising:

[0037] An impedance spectrum identification unit is configured to inject a preset composite voltage signal and collect a total-to-ground leakage current response to construct an original spectrum data set; based on the original spectrum data set, calculate a system-to-ground complex impedance spectrum; and based on the system-to-ground complex impedance spectrum, decouple out a real insulation resistance and a system-to-ground capacitance by applying a parallel RC equivalent circuit model;

[0038] A dynamic assessment unit is configured to construct an insulation health index based on the real insulation resistance and a preset insulation resistance alarm limit value; and calculate a system structure change factor based on the system-to-ground capacitance and a preset capacitance reference benchmark value;

[0039] A trend prediction unit is configured to calculate an insulation aging rate based on a time series formed by historical real insulation resistance data;

[0040] A comprehensive risk decision unit is configured to perform weighted fusion of the insulation health index, the system structure change factor and the insulation aging rate to calculate a comprehensive risk index; perform hierarchical early warning based on the comprehensive risk index; and output a tripping signal in response to the insulation health index exceeding a preset final protection limit value;

[0041] The embodiment discloses a leakage protection system for a low-voltage IT power supply system; the system aims to overcome the false alarm and missed alarm problems caused by the traditional leakage protection device relying on a single leakage current threshold, and realizes accurate and forward-looking management of insulation risks through multi-dimensional dynamic assessment and trend prediction;

[0042] The system comprises an impedance spectrum identification unit, a dynamic evaluation unit, a trend prediction unit and a comprehensive risk decision unit; the four units work cooperatively to form a complete technical closed loop from data collection, state identification, risk evaluation to decision control;

[0043] The impedance spectrum identification unit aims to accurately obtain two core parameters representing the physical state of the system: the real insulation resistance and the system-to-ground capacitance , to provide a high-quality data basis for subsequent evaluation and prediction;

[0044] In the embodiment, the unit performs wideband excitation signal injection and response collection; specifically, a preset composite voltage signal containing multiple discrete frequency points, for example, 20 characteristic frequency points selected from the range of 50 Hz to 5000 Hz, is actively injected between the three-phase conductors of the system and the protective ground; the amplitude of the signal is controlled within a safe range to avoid interference with the normal operation of the system; at the same time, a high-precision synchronous acquisition module captures the injected excitation voltage phasor at each discrete frequency point and the total ground leakage current response phasor generated by the system in real time and synchronously; these collected data collectively constitute the original spectrum data set;

[0045] Based on the above data set, the unit calculates the system-to-ground complex impedance spectrum, which aims to convert the original voltage and current data into impedance information that can better reveal the inherent physical characteristics of the system;

[0046] Finally, the unit applies a parallel RC equivalent circuit model to decouple the real insulation resistance and the system-to-ground capacitance from the frequency-dependent complex impedance spectrum; the ground characteristics of the IT power supply system can be accurately equivalent to a model of a real insulation resistance and a system-to-ground capacitance in parallel; wherein, the resistance value does not change with frequency and represents the real insulation level; while the capacitive reactance is inversely proportional to the frequency and becomes the main path of leakage current at high frequencies; the purpose of this step is to separate representing the real insulation level from the total leakage current to exclude the capacitive leakage current interference caused by ;

[0047] The dynamic evaluation unit aims to evaluate the current health status of the system from two dimensions of real-time insulation state and system structure stability in a standardized and multi-angle manner.

[0048] The unit is based on the real insulation resistance decoupled by the impedance spectrum recognition unit With a preset insulation resistance alarm limit , to build an insulation health index ; wherein, the insulation resistance alarm limit Is the legal safety threshold set according to the industry safety standard, which is the authoritative benchmark for judging whether the insulation is failed;

[0049] And, based on the system to ground capacitance With a preset capacitance reference value , the system structure change factor ; wherein, the capacitance reference value Is the statistical average value obtained by multiple measurements When the system is in the initial debugging or in the confirmed stable running state, which represents the topology of the system health; The calculation of the system structure change factor

[0050] Trend prediction unit, its technical purpose is to realize the change from post-alarm to pre-warning, by analyzing historical data to quantify the degradation trend of insulation performance;

[0051] The unit will periodically store the real insulation resistance Calculated by the impedance spectrum recognition unit, and arrange in chronological order to form a time series data set; based on this historical data sequence, the unit will calculate the insulation aging rate ; this Value does not reflect the instantaneous change of , but through the analysis of the data in a time window, it quantifies the relative downward trend of the insulation resistance persistence, so as to predict the future insulation state;

[0052] Comprehensive risk decision unit, its technical purpose is to make final summary analysis on all the evaluation and prediction results, and output clear and classified control instructions accordingly;

[0053] The unit will weight and integrate the insulation health index , representing the immediate risk, the system structure change factor , representing the structure stability, and the insulation aging rate , representing the future risk, to calculate the comprehensive risk index ; such integration calculation aims to avoid the limitations of any single index, and provides a comprehensive and three-dimensional evaluation of the system health status;

[0054] The unit is based on the comprehensive risk index Perform hierarchical early warning; Different early warning thresholds are set in the unit, and different levels of response are triggered according to The interval, so as to provide clear operation guidance for the operation and maintenance personnel in accordance with the current risk level;

[0055] In addition, the system has a set of highest priority safety protection logic; the unit independently monitors the insulation health index , and in response to the insulation health index exceeding a preset final protection limit , directly outputting a trip signal; wherein the final protection limit is a critical risk coefficient set based on engineering practice, and its value range is usually 1.5 to 2.0; this design ensures that in the critical moment when the system insulation deteriorates extremely and is about to break down, it can bypass the comprehensive evaluation to forcibly cut off the power supply at the fastest speed, and ensure the safety of personnel and equipment;

[0056] The leakage protection system of the embodiment realizes deep recognition and forward-looking management of the insulation state of the low-voltage IT system through the cooperative work of the above four units; the system recognizes the core physical parameters and , and comprehensively evaluates and predicts from three dimensions of instantaneous state, structural stability and aging trend, which has the beneficial effect of improving the accuracy of leakage protection and effectively avoiding false alarms caused by capacitive leakage current; at the same time, through trend prediction, it realizes predictive maintenance, changes passive response to active management, and improves the safety, continuity and operation and maintenance efficiency of the power supply system.

[0057] Embodiment 2:

[0058] The process of calculating the system-to-ground complex impedance spectrum by the impedance spectrum recognition unit includes:

[0059] The complex ohm law is used to calculate the injected voltage and total ground leakage current response at each frequency point in the original spectrum data set to generate complex impedance values containing equivalent resistance and equivalent reactance, forming the system-to-ground complex impedance spectrum;

[0060] This embodiment is based on embodiment 1 and illustrates the process of calculating the system-to-ground complex impedance spectrum by the impedance spectrum recognition unit;

[0061] In this process, the impedance spectrum recognition unit uses the complex ohm law; for each discrete frequency point in the original spectrum data set, the unit divides the injected voltage phasor of the point by the measured total ground leakage current response phasor ; the calculation relationship is:

[0062] ;

[0063] In this relationship, is the frequency; and are the original inputs of the model, that is, the collected voltage and current phasors; the output of the calculation is a complex number, the real part represents the equivalent resistance of the system at the frequency, and the imaginary part represents the equivalent reactance of the system at the frequency; wherein, is the imaginary unit; by performing this calculation on all collected frequency points one by one, a series of complex impedance values are finally generated, which together constitute the system ground complex impedance spectrum depicting the change of the system impedance with frequency.

[0064] Embodiment 3:

[0065] The process of decoupling the real insulation resistance and the system ground capacitance by the impedance spectrum identification unit includes:

[0066] A least square optimization model is used to determine the real insulation resistance and the system ground capacitance value through a numerical optimization algorithm, so that the sum of squares of errors between the theoretical impedance calculated based on the value and the system ground complex impedance spectrum reaches the minimum;

[0067] This embodiment further limits the specific technical means of decoupling the real insulation resistance and the system ground capacitance by the impedance spectrum identification unit in Embodiment 1;

[0068] In this embodiment, the decoupling process uses a least square optimization model; the goal of this model is to find a set of optimal and values, so that the error between the theoretical impedance calculated based on this set of values and the parallel RC equivalent circuit model and the system ground complex impedance spectrum actually measured in the last step is minimized; the optimization objective function is:

[0069] ;

[0070] wherein, is the complex impedance value in the actually measured system ground complex impedance spectrum, and is the theoretical complex impedance calculated based on the parallel RC equivalent circuit model; the goal of this function is to find a set of optimal real insulation resistance and system ground capacitance , so that at all measurement frequency points ​The sum of squares of the errors between the theoretical impedance and the actual measured impedance is minimized;

[0071] in, The theoretical complex impedance of the parallel RC equivalent circuit model is expressed as:

[0072] ;

[0073] The input to this function is the series of complex impedance values ​​calculated in the previous step. The system uses numerical optimization algorithms, such as the Levenberg-Marquardt algorithm, to iteratively solve for the function that minimizes the sum of squared errors. and To improve solution accuracy, higher weights can be assigned to errors in low-frequency data points during numerical implementation. The technical reason for this is... The contribution is more significant in the low-frequency region; although for systems with extremely complex structures, their ground characteristics may contain higher-order impedance components, the parallel RC model has been proven to capture the core parameters most critical to insulation risk assessment with sufficient accuracy, achieving a good balance between universality and accuracy in engineering applications.

[0074] Example 4:

[0075] The dynamic evaluation unit calculates the insulation health index by dividing the preset insulation resistance alarm limit by the actual insulation resistance.

[0076] This embodiment illustrates how the dynamic evaluation unit in Embodiment 1 calculates the insulation health index. Specific methods;

[0077] The dynamic evaluation unit uses preset insulation resistance alarm limits. Divide by the actual insulation resistance obtained from real-time decoupling. The insulation health index was calculated. The calculation formula is as follows:

[0078] ;

[0079] In this formula, the input is the result calculated from the previous steps. , As a preset constant reference; output It is a dimensionless relative risk index; when the system insulation is good, Much larger ,at this time Much less than 1; when the system insulation deteriorates, The value decreased and approached hour, The value approaches 1; once Below the legal limit , Will be greater than 1, clearly indicate that the system into the risk state.

[0080] Embodiment 5:

[0081] The dynamic evaluation unit calculates the difference between the system-to-ground capacitance and the preset capacitance reference value, and divides the difference by the capacitance reference value to obtain a system structure change factor;

[0082] The dynamic evaluation unit is also used to:

[0083] In response to the system structure change factor continuously exceeding the preset capacitance fluctuation limit for a preset length of time, prompting to update the capacitance reference value, and in response to a confirmation instruction, updating the capacitance reference value with a new stable capacitance value;

[0084] This embodiment describes the evaluation mechanism of the dynamic evaluation unit for system structure changes, which not only can detect changes, but also has self-adaptive updating capability;

[0085] According to the limitation of embodiment 5, the dynamic evaluation unit calculates the difference between the current system-to-ground capacitance And the preset capacitance reference value , and divides the difference by the capacitance reference value To obtain a system structure change factor ; Its calculation formula is:

[0086] ;

[0087] Before calculation, the system will check whether the capacitance reference value Is a non-zero valid value, so as to avoid calculation error; A valid Is the premise of system structure change evaluation;

[0088] The input of this formula is the current measured And the reference value ; When the absolute value of Exceeds the preset system capacitance fluctuation limit , for example , representing a 20% fluctuation, the system considers that a structural change may have occurred;

[0089] In order to further adapt to the normal topology change of the system and avoid long-term false positives, according to the limitation of embodiment 5, the dynamic evaluation unit also has the self-adaptive updating function of the reference value; Its internal logic is: in response to the system structure change factor Continuously exceeding the preset capacitance fluctuation limit For a preset length of time For example, every 3 hours, the system will prompt the maintenance personnel to update the capacitor reference value. If the maintenance personnel confirm that this change is a legitimate and permanent system change and issue a confirmation command, the system will respond to the command and adopt the new, stabilized capacitor value as the new reference value. .

[0090] Example 6:

[0091] The trend prediction unit processes the real insulation resistance time series within a preset time window and calculates the relative loss rate of insulation resistance per unit time to obtain the insulation aging rate.

[0092] This embodiment illustrates how the trend prediction unit in Embodiment 1 calculates the insulation aging rate. This method aims to quantify the trend of insulation performance degradation.

[0093] The trend prediction unit predicts the actual insulation resistance within a preset time window. The time series data is processed to calculate the relative loss rate of insulation resistance per unit time, thereby obtaining the insulation aging rate. The calculation formula is as follows:

[0094] ;

[0095] The formula input is a segment of length... History Data sequence, { },in Represents the first in the time series The actual insulation resistance value of each sampling point For example, if the data point is taken from the past 24 hours, then... ,and The time interval between two measurements is, for example, 1 hour; the formula calculates the time within the time window. Within each time interval Inside The relative rate of decrease, and their arithmetic mean; output Its physical dimension is the reciprocal of time. A consistently positive The value indicates that the system insulation is continuously degrading;

[0096] To ensure robustness of computation, in actual calculations, it is necessary to... The value is preprocessed; if a certain value is detected... If a value approaches zero due to a serious fault or sensor malfunction, the system should skip the calculation or mark it as abnormal and directly trigger a high-level alarm to prevent calculation errors involving division by zero.

[0097] Example 7:

[0098] The process by which the comprehensive risk decision-making unit calculates the comprehensive risk index includes:

[0099] The insulation health index, the system structure change factor normalized by the preset capacitance fluctuation limit, and the insulation aging rate normalized by the preset aging rate threshold are multiplied by their respective preset weight coefficients and then summed to obtain the comprehensive risk index.

[0100] This embodiment specifically defines the calculation of the comprehensive risk index by the comprehensive risk decision-making unit in Embodiment 1. Fusion algorithm;

[0101] This calculation process aims to integrate risk information from multiple dimensions into a single indicator; specifically, this unit will incorporate the insulation health index. After the preset capacitance fluctuation limit Normalized system structure change factor and the preset aging rate threshold. Normalized insulation aging rate Each factor is multiplied by its corresponding preset weighting coefficient and then summed to obtain the comprehensive risk index. The calculation formula is as follows:

[0102] ;

[0103] In this formula, all inputs are dynamic values ​​calculated in previous steps; to ensure dimensional consistency, The absolute value is determined by its alarm threshold. Normalization By its alarm threshold Normalization ensures that all terms involved in the weighted calculation are dimensionless. To ensure the validity of the calculation, a preset capacitance fluctuation limit is used. With aging rate threshold All should be set to non-zero positive numbers; among them, It is an unacceptable aging rate threshold set based on the characteristics of equipment materials or long-term operation and maintenance experience data. For example, based on the life curve of the insulation material of a specific cable, the threshold is set when the average relative loss rate of insulation resistance per unit time exceeds 5%. They are dimensionless weighting coefficients that satisfy... Its value can be adjusted according to the operation and maintenance strategy; for example, if the focus is on real-time security, it can be set to... If the predictive maintenance is focused on, the weight of the of the risk index can be increased.

[0104] Embodiment 8:

[0105] The process of the hierarchical early warning performed by the comprehensive risk decision unit includes:

[0106] When the comprehensive risk index is lower than the first early warning threshold, it is determined as a normal state.

[0107] When the comprehensive risk index reaches the first early warning threshold but is lower than the second early warning threshold, a concern level prompt is triggered.

[0108] When the comprehensive risk index is not lower than the second early warning threshold, a warning level alarm is triggered.

[0109] This embodiment is based on the embodiment 1, and the specific logic of the hierarchical early warning performed by the comprehensive risk decision unit is clarified.

[0110] The unit compares the comprehensive risk index calculated in the last step with two preset early warning thresholds , i.e. the first early warning threshold, and , i.e. the second early warning threshold, and satisfies These thresholds are set based on statistical analysis of historical failure data and the operation and maintenance response capability corresponding to different risk levels, and the following hierarchical logic is executed:

[0111] Normal state: when the comprehensive risk index is lower than the first early warning threshold , the system determines that it is in a normal operation state, and no alarm or prompt is generated.

[0112] First-level early warning (concern level): when the comprehensive risk index reaches the first early warning threshold but is lower than the second early warning threshold , the system triggers a concern level prompt; this state usually indicates that an abnormality occurs in a non-core indicator of the system, but the immediate insulation index is still within a safe range, aiming to remind the operation and maintenance personnel to pay attention.

[0113] Second-level early warning (warning level): when the comprehensive risk index is not lower than the second early warning threshold , the system triggers a warning level sound and light alarm; this state indicates that the comprehensive risk has reached a high level, and the operation and maintenance personnel need to intervene immediately for troubleshooting.

[0114] The above merely illustrates the preferred embodiments of the present application, and is not intended to limit the protection scope of the present application; any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0115] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A leakage protection system for low voltage IT power supply systems, characterized in that, The method comprises the following steps: An impedance spectrum identification unit is used to inject a preset composite voltage signal and collect a total ground leakage current response to construct an original spectrum data set; Based on the original spectrum data set, a system ground complex impedance spectrum is calculated; And a parallel RC equivalent circuit model is applied to decouple the real insulation resistance and the system ground capacitance based on the system ground complex impedance spectrum; A dynamic assessment unit is used to construct an insulation health index based on the real insulation resistance and a preset insulation resistance alarm limit value; And a system structure change factor is calculated based on the system ground capacitance and a preset capacitance reference benchmark value; A trend prediction unit is used to calculate an insulation aging rate based on a time series formed by historical real insulation resistance data; An integrated risk decision unit is used to perform weighted fusion of the insulation health index, the system structure change factor, and the insulation aging rate to calculate an integrated risk index; A hierarchical early warning is performed based on the integrated risk index; And a trip signal is output in response to the insulation health index exceeding a preset final protection limit value.

2. The ground fault protection system for low voltage IT power supply system as claimed in claim 1 wherein, The process of calculating the system ground complex impedance spectrum by the impedance spectrum identification unit comprises the following steps: The injected voltage and the total ground leakage current response at each frequency point in the original spectrum data set are calculated using the complex ohm law to generate complex impedance values containing equivalent resistance and equivalent reactance, thereby forming the system ground complex impedance spectrum.

3. The ground fault protection system for low voltage IT power supply system as claimed in claim 1 wherein, The process of decoupling the real insulation resistance and the system ground capacitance by the impedance spectrum identification unit comprises the following steps: A least squares optimization model is used to determine the real insulation resistance and the system ground capacitance value by a numerical optimization algorithm, so that the error sum of squares between the theoretical impedance calculated based on the value and the system ground complex impedance spectrum is minimized.

4. The ground fault protection system for low voltage IT power supply system of claim 1, wherein, The dynamic assessment unit calculates the insulation health index by dividing the preset insulation resistance alarm limit value by the real insulation resistance.

5. The ground fault protection system for low voltage IT power supply system as claimed in claim 1 wherein, The dynamic assessment unit calculates the system structure change factor by calculating the difference between the system ground capacitance and the preset capacitance reference benchmark value, and dividing the difference by the capacitance reference benchmark value.

6. The ground fault protection system for low voltage IT power supply systems of claim 5, wherein, The dynamic assessment unit is also used to: In response to the system structure change factor continuously exceeding the preset capacitance fluctuation limit value for a preset time length, prompting to update the capacitance reference benchmark value, and in response to a confirmation instruction, updating the capacitance reference benchmark value with a new stable capacitance value.

7. The ground fault protection system for low voltage IT power supply systems of claim 1, wherein, The trend prediction unit calculates the insulation aging rate by calculating the relative loss rate of the insulation resistance per unit time through processing of the real insulation resistance time series within a preset time window.

8. The ground fault protection system for low voltage IT power supply systems of claim 1, wherein, The process of calculating the integrated risk index by the integrated risk decision unit comprises the following steps: The insulation health index, the system structure change factor normalized by the preset capacitance fluctuation limit value, and the insulation aging rate normalized by the preset aging rate threshold value are multiplied by corresponding preset weight coefficients and then summed to obtain the integrated risk index.

9. The ground fault protection system for low voltage IT power supply system of claim 1, wherein, The process of performing hierarchical early warning by the integrated risk decision unit comprises the following steps: When the integrated risk index is below a first warning threshold, it is determined to be in a normal state; When the integrated risk index reaches the first warning threshold but is below a second warning threshold, a level of attention prompt is triggered; When the integrated risk index is not below the second warning threshold, a warning level alarm is triggered.

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