Insulation fault positioning system and method for power distribution network

Abstract

The invention discloses an insulation fault positioning system and method for a power distribution network, and relates to the technical field of power distribution network insulation monitoring, and the method comprises the steps: injecting a first test signal into the power distribution network, and obtaining the intensity of the first test signal; detecting and extracting the intensity of a reflected signal caused by the signal; calculating a real-time state index H reflecting the impedance matching degree of the system according to the intensity of the two; judging that the system is currently in one of four state categories of stable matching, matching attenuation, critical matching and mismatching based on the numerical value of the H and the change trend of the H; dynamically adjusting the injection intensity of the second test signal according to the state category; and finally measuring the leakage current by using the second test signal and calculating an insulation resistance value.

Description

Technical Field

[0001] This invention relates to the field of insulation monitoring technology for power distribution networks, specifically an insulation fault location system and method for power distribution networks. Background Technology

[0002] In AC ungrounded (IT) or neutral-point-grounded (ITN) distribution networks, online insulation monitoring systems are crucial for ensuring power supply safety. Current mainstream monitoring technologies generally employ the "signal injection method," which involves injecting a low-frequency voltage signal of a specific frequency between the power grid and ground, and then calculating parameters such as the system's insulation resistance by detecting the resulting leakage current.

[0003] However, this method has an inherent technical contradiction: a direct conflict between the measurement accuracy requirements and the system's electromagnetic compatibility (EMC) requirements. On the one hand, in order to accurately detect weak leakage currents in complex noisy environments, especially when the insulation resistance is high, a signal of sufficient strength needs to be injected to ensure the measurement signal-to-noise ratio. On the other hand, an excessively strong injected signal can cause electromagnetic interference to sensitive loads in the power grid, affecting their normal operation, and may even excite the distributed parameter resonance of the system, bringing safety hazards.

[0004] To address this contradiction, existing technologies typically adopt static and conservative compromises. For example, based on the most stringent application scenario standards, the amplitude of the injected signal is fixed at a low, conservative level; another approach is to use a trial-and-error strategy, gradually increasing the signal from a very small value until a valid response is detected.

[0005] However, these methods are essentially open-loop control: the process of setting or adjusting the signal strength does not involve closed-loop optimization based on feedback regarding its impact on the real-time state of the power grid after injection. Therefore, the system cannot dynamically balance the objectives of "achieving optimal measurement sensitivity" and "ensuring minimal electromagnetic interference." When the power grid load changes dynamically, the fixed preset method may cause measurement lag or inaccuracy due to an excessively weak signal, while the simple incremental method may introduce unnecessary transient interference during the adjustment process.

[0006] In summary, how to achieve high-precision and rapid adaptive monitoring of insulation parameters without affecting the normal operation of the power grid remains a technical challenge to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide an insulation fault location system and method for power distribution networks to solve the problems raised in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] An insulation fault location method for power distribution networks includes the following steps:

[0010] S1. Inject a first test signal into the distribution network and obtain the strength parameters of the first test signal;

[0011] S2. Detect and acquire the reflected signal caused by the first test signal in the power distribution network, and extract the intensity parameter of the reflected signal;

[0012] S3. Based on the intensity of the first test signal and the intensity of the reflected signal, calculate the real-time status index reflecting the impedance matching degree of the system.

[0013] S4. Determine the current operating status category of the distribution network based on the value of the real-time status indicator;

[0014] S5. Based on the current operating state category, dynamically adjust and generate the injection intensity of the second test signal;

[0015] S6. Use the second test signal to perform measurements to obtain optimized distribution network insulation status information.

[0016] S1 further includes the following:

[0017] A first test signal with a preset frequency, waveform, and voltage amplitude is generated by a signal generator.

[0018] The first test signal is injected between the target phase line and the system ground of the distribution network via a signal coupler;

[0019] The voltage amplitude of the first test signal is used as the intensity parameter of the first test signal;

[0020] Wherein, the target phase line is the live conductor to be monitored in the distribution network, and the system ground serves as a common potential reference point for signal injection and measurement.

[0021] S2 further includes the following:

[0022] Using the signal coupler, the signal component reflected back to the injection point from the total signal at the injection point is separated;

[0023] The signal components are sequentially subjected to signal conditioning and analog-to-digital conversion to obtain a digitized reflected signal;

[0024] The root mean square (RMS) operation is performed on the digitized reflected signal, and the result is used as the intensity parameter of the reflected signal.

[0025] S3 further includes the following:

[0026] Calculate the ratio k of the reflected signal strength Ar to the first test signal strength parameter Ai according to the first test signal strength parameter Ai and the reflected signal strength Ar. The formula is as follows:

[0027] k = Ar / Ai;

[0028] When the ratio k is greater than 1, correct the value of k to 1;

[0029] Input the ratio k into a preset conversion function F(k). The conversion function F(k) is configured to perform a non - linear transformation on the input value. The formula is as follows:

[0030] F(k)=1 - k 2 ;

[0031] Map the output value of the conversion function F(k) to a preset continuous numerical interval. The upper and lower limit values of this interval correspond to the theoretical best state and the theoretical worst state of the system impedance matching degree respectively;

[0032] Determine the obtained continuous numerical value after completing the mapping as the real - time state index H reflecting the system impedance matching degree.

[0033] The S4 further includes the following content:

[0034] Calculate the difference ΔH between the current value H(t) of the real - time state index H and the historical value H(t - 1) of the real - time state index H in the previous calculation cycle;

[0035] Classify the current operating state of the distribution network into one of four discrete state categories based on the threshold interval where the current value H(t) is located and the sign of the difference ΔH.

[0036] The classifying the current operating state of the distribution network into one of four discrete state categories based on the threshold interval where the current value H(t) is located and the sign of the difference ΔH includes:

[0037] When H(t)≥Hhigh and ΔH≥0, it is determined as the first state category, and the first state category represents that the system impedance matching is in a stable matching state;

[0038] When H(t)≥Hhigh and ΔH < 0, it is determined as the second state category, and the second state category represents that the system impedance matching is in a matching attenuation state;

[0039] When Hmid≤H(t)<Hhigh, it is determined as the third state category, and the third state category represents that the system impedance matching is in a critical matching state;

[0040] When H(t) < Hmid, it is determined as the fourth state category, and the fourth state category characterizes that the system impedance matching is in a mismatched state;

[0041] Where, Hhigh and Hmid are preset thresholds, and Hhigh > Hmid.

[0042] The S5 further includes the following:

[0043] According to the determined operation state category, generate an instruction to control the voltage amplitude U2 of the second test signal output by the signal generator according to a preset intensity adjustment rule;

[0044] Where, the intensity adjustment rule is configured as follows:

[0045] For the first state category, generate an instruction to increase the voltage amplitude U2 of the second test signal according to a preset value;

[0046] For the second state category, generate an instruction to keep the voltage amplitude U2 of the second test signal;

[0047] For the third state category, generate an instruction to decrease the voltage amplitude U2 of the second test signal according to a preset value;

[0048] For the fourth state category, generate an instruction to set the voltage amplitude U2 of the second test signal to zero.

[0049] The S6 further includes the following:

[0050] Measure the leakage current flowing through the connecting wire between the signal coupler and the system ground under the action of the second test signal to obtain a leakage current signal;

[0051] Obtain a reference signal generated by the signal generator and synchronized with the voltage of the second test signal;

[0052] Multiply the leakage current signal by the reference signal, and perform filtering on the multiplication result to extract the component in the leakage current signal that is in the same phase as the voltage of the second test signal as the resistive current component I;

[0053] According to the voltage amplitude U2 of the second test signal and the resistive current component I, calculate the current insulation resistance value R of the distribution network, and the formula is as follows:

[0054] R = U2 / I;

[0055] Take the insulation resistance value R, the real-time state index H and the determined current operation state category together as the optimized insulation state information of the distribution network.

[0056] An insulation fault location system for a power distribution network includes a signal generation and injection module, a first signal strength acquisition module, a reflected signal detection and extraction module, a status index calculation module, an operating status determination module, a signal strength dynamic adjustment module, an insulation parameter measurement module, and a signal processing and output module.

[0057] The signal generation and injection module is used to generate a test signal with preset characteristics and inject the test signal between the target phase line and the system ground of the distribution network.

[0058] The first intensity acquisition module is used to acquire the intensity parameters of the first test signal;

[0059] The reflected signal detection and extraction module is used to detect and separate the signal components reflected back to the injection point from the distribution network, and extract the intensity parameters of the reflected signal.

[0060] The state index calculation module is used to calculate a real-time state index H that reflects the impedance matching degree of the system based on the intensity parameters of the first test signal and the intensity parameters of the reflected signal.

[0061] The operation status determination module is used to determine the current operation status category of the distribution network based on the value and changing trend of the real-time status indicator H.

[0062] The signal strength dynamic adjustment module is used to dynamically adjust and generate the injection strength command of the next test signal according to the determined operating state category and preset rules.

[0063] The insulation parameter measurement module is used to measure leakage current, extract resistive current components, and calculate the insulation resistance value of the distribution network based on the adjusted second test signal.

[0064] The signal processing and output module is used to condition, convert analog to digital, and perform calculations on the measurement signal, and output the optimized distribution network insulation status information.

[0065] Compared with the prior art, the beneficial effects of the present invention are:

[0066] 1. This invention calculates the system impedance matching index H by detecting the reflected signal and dynamically adjusts the injected signal strength accordingly, constructing a closed-loop feedback system. This enables the monitoring device to perceive the impact of its own injection behavior on the system state in real time and automatically find the current optimal balance between "ensuring the measurement signal-to-noise ratio" and "minimizing electromagnetic interference," fundamentally solving the static contradiction of traditional open-loop injection methods;

[0067] 2. The system health index H created by this invention is itself a valuable diagnostic parameter. The H value and its changing trend ΔH can intuitively reflect the overall uniformity and stability of the distribution network's ground parameters. Before the insulation resistance drops significantly, it can provide early warning of system structural changes, potential resonance risks, or local insulation degradation trends, thus achieving an upgrade from "fault alarm" to "condition warning". Attached Figure Description

[0068] Figure 1 This is a flowchart of an insulation fault location method for a power distribution network according to the present invention.

[0069] Figure 2 This is a flowchart illustrating the state determination and dynamic adjustment decision-making process of an insulation fault location method for power distribution networks according to the present invention. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] Example: Figures 1-2 As shown, the present invention provides a technical solution.

[0072] An insulation fault location method for power distribution networks, such as Figure 1 As shown, it includes the following steps:

[0073] S1. Inject a first test signal into the distribution network and obtain the strength parameters of the first test signal;

[0074] S2. Detect and acquire the reflected signal caused by the first test signal in the power distribution network, and extract the intensity parameter of the reflected signal;

[0075] S3. Based on the intensity of the first test signal and the intensity of the reflected signal, calculate the real-time status index reflecting the impedance matching degree of the system.

[0076] S4. Determine the current operating status category of the distribution network based on the value of the real-time status indicator;

[0077] S5. Based on the current operating state category, dynamically adjust and generate the injection intensity of the second test signal;

[0078] S6. Use the second test signal to perform measurement to obtain optimized distribution network insulation status information; the direct purpose of the optimized distribution network insulation status information is to provide the most suitable insulation resistance value R under the current system conditions for judging the insulation status;

[0079] All the logic design and real-time adjustments in the entire adaptive closed-loop process are aimed at enabling the system to automatically find a test condition that achieves the best balance between ensuring that the measured signal strength is sufficient to overcome noise and avoiding interference from injected signals to the power distribution system.

[0080] S6 is the final measurement performed under these optimized conditions, and the insulation resistance value R calculated from it is the ultimate criterion that this method aims to provide.

[0081] Meanwhile, the real-time status indicator H and operating status category output are used to verify under what system matching background and what safety strategy the insulation resistance value R was obtained, thus proving that the data is the most suitable measurement result after systematic optimization, rather than an ordinary reading obtained under fixed or blind conditions.

[0082] S1 further includes the following:

[0083] A first test signal with a preset frequency, waveform, and voltage amplitude is generated by a signal generator.

[0084] The first test signal is injected between the target phase line and the system ground of the distribution network via a signal coupler;

[0085] The voltage amplitude of the first test signal is used as the intensity parameter of the first test signal;

[0086] Wherein, the target phase line is the live conductor to be monitored in the distribution network, and the system ground serves as a common potential reference point for signal injection and measurement.

[0087] S2 further includes the following:

[0088] Using the signal coupler, the signal component reflected back to the injection point from the total signal at the injection point is separated;

[0089] The signal components are sequentially subjected to signal conditioning and analog-to-digital conversion to obtain a digitized reflected signal;

[0090] The root mean square (RMS) operation is performed on the digitized reflected signal, and the result is used as the intensity parameter of the reflected signal.

[0091] The signal coupler is a device with directional coupling function; it can couple the signal generated by the generator to the power grid in the forward direction, and at the same time separate the signal reflected back from the power grid from the reverse coupling port, thereby realizing the separation and measurement of the incident signal and the reflected signal.

[0092] S3 further includes the following:

[0093] Based on the first test signal strength parameter Ai and the reflected signal strength Ar, the ratio k of the reflected signal strength Ar to the first test signal strength parameter Ai is calculated using the following formula:

[0094] k = Ar / Ai;

[0095] When the ratio k is greater than 1, the value of k is corrected to 1;

[0096] The ratio k is input to a preset transformation function F(k), which is configured to perform a nonlinear transformation on the input value, as shown in the following formula:

[0097] F(k) = 1 - k 2 ;

[0098] The output value of the conversion function F(k) is mapped to a preset continuous numerical range, the upper limit and the lower limit of which correspond to the theoretical best state and the theoretical worst state of the system impedance matching degree, respectively.

[0099] The continuous values ​​obtained after the mapping are completed are determined as the real-time status index H that reflects the impedance matching degree of the system.

[0100] When reflection increases, i.e., when k increases, k 2 This will amplify its negative impact, making the state indicator H more sensitive to system mismatch, i.e., interference risk.

[0101] S4 further includes the following:

[0102] like Figure 2 As shown, based on the current value H(t) of the real-time status index H and the historical value H(t-1) of the real-time status index H in the previous calculation period, the difference ΔH between the current value H(t) and H(t-1) is calculated.

[0103] The system operates in a fixed cycle T, meaning that every T time interval, it restarts the complete adaptive monitoring process from step S1; H(t-1) refers to the H value calculated in the previous cycle T.

[0104] Based on the threshold interval in which the current value H(t) is located and the positive or negative of the difference ΔH, the current operating state of the distribution network is classified into one of four discrete state categories.

[0105] The classification of the current operating state of the distribution network into one of four discrete state categories based on the threshold interval in which the current value H(t) is located and the positive or negative of the difference ΔH includes:

[0106] When H(t) ≥ Hhigh and ΔH ≥ 0, it is determined as the first state category, and the first state category represents that the system impedance matching is in a stable matching state;

[0107] When H(t) ≥ Hhigh and ΔH < 0, it is determined as the second state category, and the second state category represents that the system impedance matching is in a matching attenuation state;

[0108] When Hmid ≤ H(t) < Hhigh, it is determined as the third state category, and the third state category represents that the system impedance matching is in a critical matching state;

[0109] When H(t) < Hmid, it is determined as the fourth state category, and the fourth state category represents that the system impedance matching is in a mismatched state;

[0110] By comparing the current value H(t) of the real-time state index H with the preset threshold, the absolute level of the impedance matching of the system at the current moment is objectively judged; at the same time, by calculating the difference ΔH between H(t) and the historical value H(t - 1) of the previous cycle, the instantaneous change direction and trend of the system matching degree are captured;

[0111] Combining and judging the information in these two dimensions can achieve refined and forward-looking classification of the system operating state: when H(t) ≥ Hhigh and ΔH ≥ 0, it indicates that the system is not only well-matched currently but also in a stable state, so it is classified as stable matching;

[0112] When H(t) ≥ Hhigh but ΔH < 0, it indicates that although the current matching degree is good, its internal state is deteriorating and there are potential risks, so it is classified as matching attenuation to issue an early warning;

[0113] When Hmid ≤ H(t) < Hhigh, regardless of the trend, its current matching degree is no longer sufficient to be considered safe, and the system has entered a critical matching state that requires active intervention;

[0114] When H(t) < Hmid, it indicates that the system is in a mismatched dangerous state of serious mismatch;

[0115] This classification logic enables the determination of system status to no longer rely on a single, static insulation resistance threshold, but to achieve in-depth perception and graded early warning of the electrical environment safety status of the power distribution system through two dimensions: dynamic coupling matching degree level and its changing trend.

[0116] Hhigh and Hmid are preset thresholds, with Hhigh > Hmid. In practical applications, users can fine-tune these two thresholds through a centralized display terminal according to the sensitivity and safety requirements of the specific power distribution network.

[0117] S5 further includes the following:

[0118] Based on the determined operating state category, and in accordance with the preset intensity adjustment rules, an instruction is generated to control the signal generator to output the voltage amplitude U2 of the second test signal;

[0119] The intensity adjustment rules are configured as follows:

[0120] For the first state category, an instruction is generated to increase the voltage amplitude U2 of the second test signal by a preset value;

[0121] For the second state category, generate instructions to maintain the voltage amplitude U2 of the second test signal;

[0122] For the third state category, an instruction is generated to reduce the voltage amplitude U2 of the second test signal by a preset value;

[0123] For the fourth state category, an instruction is generated to set the voltage amplitude U2 of the second test signal to zero;

[0124] The preset value can be a fixed percentage of the current voltage amplitude or a fixed voltage step value. Preferably, the adjustment range can be set differently according to different state categories.

[0125] S6 further includes the following:

[0126] The leakage current flowing through the connecting wire between the signal coupler and the system ground is measured under the action of the second test signal to obtain the leakage current signal; the leakage current is measured by a precision current sampling resistor or current transformer connected in series in the grounding loop of the signal coupler.

[0127] Obtain a reference signal generated by the signal generator that is synchronized with the voltage of the second test signal;

[0128] The leakage current signal is multiplied by the reference signal, and the multiplication result is filtered to extract the component in the leakage current signal that is in phase with the voltage of the second test signal, which is taken as the resistive current component I.

[0129] The filtering process is a low-pass filter, the purpose of which is to filter out the high-frequency components generated after the multiplication operation and retain the DC signal that is proportional to the resistive current component.

[0130] Based on the voltage amplitude U2 of the second test signal and the resistive current component I, the current insulation resistance value R of the distribution network is calculated using the following formula:

[0131] R = U² / I;

[0132] The insulation resistance value R, the real-time status index H, and the determined current operating status category are used together as the optimized distribution network insulation status information.

[0133] An insulation fault location system for a power distribution network includes a signal generation and injection module, a first signal strength acquisition module, a reflected signal detection and extraction module, a status index calculation module, an operating status determination module, a signal strength dynamic adjustment module, an insulation parameter measurement module, and a signal processing and output module.

[0134] The signal generation and injection module is used to generate a test signal with preset characteristics and inject the test signal between the target phase line and the system ground of the distribution network.

[0135] The first intensity acquisition module is used to acquire the intensity parameters of the first test signal;

[0136] The reflected signal detection and extraction module is used to detect and separate the signal components reflected back to the injection point from the distribution network, and extract the intensity parameters of the reflected signal.

[0137] The state index calculation module is used to calculate a real-time state index H that reflects the impedance matching degree of the system based on the intensity parameters of the first test signal and the intensity parameters of the reflected signal.

[0138] The operation status determination module is used to determine the current operation status category of the distribution network based on the value and changing trend of the real-time status indicator H.

[0139] The signal strength dynamic adjustment module is used to dynamically adjust and generate the injection strength command of the next test signal according to the determined operating state category and preset rules.

[0140] The insulation parameter measurement module is used to measure leakage current, extract resistive current components, and calculate the insulation resistance value of the distribution network based on the adjusted second test signal.

[0141] The signal processing and output module is used to condition, convert analog to digital, and perform calculations on the measurement signal, and output the optimized distribution network insulation status information.

[0142] An insulation fault location method for power distribution networks is proposed. Its core lies in constructing a closed-loop adaptive system to resolve the inherent contradiction between measurement accuracy and electromagnetic compatibility in traditional insulation monitoring. This method senses the impact of injected signals on the power distribution system in real time and dynamically adjusts the measurement strategy to ultimately obtain the most suitable insulation resistance measurement value under the current system conditions. The complete implementation process of this method will be described in detail below.

[0143] First, a first test signal with a preset frequency, waveform, and voltage amplitude is generated by a signal generator; for example, the signal can be set to a frequency of 1.25Hz, a sine wave, and a voltage amplitude of 5V. This first test signal is injected into the distribution network between the target phase line to be monitored and the system ground via a signal coupler with directional coupling function.

[0144] In this system, the target phase line is a energized conductor in the distribution network, while the system ground is the common potential reference point for the entire monitoring system. The signal coupler plays a crucial role; it couples the signal generated by the generator forward to the power grid while simultaneously separating the signal reflected back from the grid from the reverse coupling port, thus achieving separate measurement of the incident and reflected signals. The voltage amplitude of the first test signal, for example, 5V, is directly used as its intensity parameter Ai, providing a basis for subsequent calculations.

[0145] Subsequently, using the same signal coupler, the signal component reflected back to the injection point from the total signal at the injection point is separated. This reflected signal component is then subjected to signal conditioning processes such as amplification and filtering, followed by analog-to-digital conversion to obtain a digitized reflected signal.

[0146] By performing a root mean square (RMS) operation on the digitized reflected signal, its intensity parameter Ar can be extracted. For example, if the measured RMS value of the reflected signal is 0.5V, then Ar = 0.5V. This step achieves direct quantification of the system's reflection behavior.

[0147] After obtaining the first test signal strength parameter Ai and the reflected signal strength parameter Ar, the system impedance matching degree can be evaluated.

[0148] Calculate the ratio k of the reflected signal intensity Ar to the first test signal intensity parameter Ai, i.e., k = Ar / Ai. Taking the assumed data as an example, k = 0.5 / 5 = 0.1;

[0149] It should be noted that under extreme conditions (such as system resonance), Ar may be greater than Ai, resulting in k > 1. To ensure the stability of subsequent logic, when the calculated ratio k is greater than 1, its value is corrected to 1, i.e., k = 1.

[0150] Then, the ratio k is input into a preset transformation function F(k) for nonlinear transformation; this function is defined as F(k) = 1 - k². This design ensures that when reflection is enhanced (k increases), k² amplifies its negative impact, making the output more sensitive to system mismatch, reflecting the principle of safety first.

[0151] The output value of F(k) is mapped to a preset continuous numerical range, such as [0.2, 0.95], where 0.95 corresponds to the theoretical best-fit state and 0.2 corresponds to the theoretical worst-fit state. Through linear mapping, the output of F(k) is converted into an intuitive real-time state indicator H. For k=0.1, F(0.1)=1-0.01=0.99, and after mapping, we assume H=0.94.

[0152] The system runs the above process in a fixed cycle T (e.g., 30 seconds); in each cycle, the difference ΔH = H(t) - H(t-1) is calculated based on the current value H(t) of the real-time status index H and the historical value H(t-1) of the previous cycle. The difference ΔH reflects the instantaneous change trend of the system matching degree.

[0153] Based on the preset threshold range in which the current value H(t) is located and the sign of ΔH, the current operating state of the distribution network is classified into one of the four discrete state categories; the preset thresholds Hhigh and Hmid (e.g., Hhigh=0.85, Hmid=0.60) are the key to the judgment;

[0154] When H(t) ≥ 0.85 and ΔH ≥ 0, it is classified as the first state category, namely "stable matching state," indicating that the system is currently well-matched and in a stable state. When H(t) ≥ 0.85 but ΔH < 0, it is classified as the second state category, namely "match decay state," indicating that although the current matching degree is still good, it is deteriorating and an early warning needs to be issued. When 0.60 ≤ H(t) < 0.85, it is classified as the third state category, namely "critical matching state," indicating that the current matching degree is insufficient and the system has entered a range requiring active intervention. When H(t) < 0.60, it is classified as the fourth state category, namely "mismatch state," indicating that the system is in a dangerous state of severe mismatch.

[0155] This classification logic achieves in-depth perception and graded early warning of the system's security status by dynamically coupling the two dimensions of "matching degree level" and "its changing trend," thus getting rid of the dependence on a single static threshold.

[0156] Based on the determined operating state category, the system generates an instruction for the control signal generator to output the second test signal according to the preset intensity adjustment rules;

[0157] The rule is specifically configured to: for the first state category, generate an instruction to increase the voltage amplitude U2 of the second test signal by a preset value (such as increasing the current voltage amplitude by 20%);

[0158] For the second state category, generate instructions that keep U2 unchanged;

[0159] For the third state category, generate an instruction to reduce U2 by a preset value (such as reducing the current voltage amplitude by 30%);

[0160] For the fourth state category, generate an instruction to set U2 to zero (i.e., stop injection);

[0161] These differentiated instructions directly embody the closed-loop control concept based on state feedback, aiming to achieve the optimal trade-off between measurement accuracy and system safety under different risk levels.

[0162] Finally, under the second test signal condition obtained by the above-mentioned dynamic adjustment, the final insulation parameter measurement is performed;

[0163] The leakage current flowing through the connecting wire between the signal coupler and the system ground under the action of the second test signal is usually measured by a precision sampling resistor or current transformer connected in series in the circuit to obtain the leakage current signal.

[0164] Simultaneously, a reference signal generated by a signal generator and synchronized with the second test signal voltage is acquired. The leakage current signal is multiplied by this reference signal, and the multiplication result is low-pass filtered to remove high-frequency components, retaining the DC component that is in phase with the second test signal voltage. This DC component is proportional to the resistive current component I. Based on the voltage amplitude U2 of the second test signal and the resistive current component I, the current insulation resistance value R of the distribution network is calculated using the formula R = U2 / I.

[0165] For example, if U2 is the optimized 6V and I is measured to be 0.002A, then R = 3000Ω. The calculated insulation resistance value R, the real-time status index H, and the determined current operating status category are combined as the optimized distribution network insulation status information output.

[0166] The ultimate goal of all the logic design and real-time adjustments in the entire adaptive closed-loop process is to enable the system to automatically find a test condition that achieves the best balance between "ensuring that the measured signal strength is sufficient to overcome noise" and "avoiding the injection signal from interfering with the power distribution system".

[0167] S6 is the final measurement performed under these optimized conditions, and the insulation resistance value R it calculates is the ultimate criterion that this method aims to provide. Meanwhile, the real-time status index H and operating status category output at the same time are used to verify under what system matching background and what safety strategy the insulation resistance value R was obtained, thereby proving to the user that the data is the most suitable measurement result after systematic optimization, rather than an ordinary reading obtained under fixed or blind conditions.

[0168] Corresponding to the above method, an insulation fault location system for a power distribution network includes a signal generation and injection module, a first signal strength acquisition module, a reflected signal detection and extraction module, a status index calculation module, an operating status determination module, a signal strength dynamic adjustment module, an insulation parameter measurement module, and a signal processing and output module.

[0169] These modules strictly correspond to the method steps in function and work together. The signal generation and injection module is responsible for generating and injecting the test signal; the first signal strength acquisition module acquires the strength of the injected signal; the reflected signal detection and extraction module separates and extracts the reflected signal strength; the status index calculation module calculates the real-time status index H based on the two intensities; the operating status determination module determines the status category based on H and its changing trend; the signal strength dynamic adjustment module generates adjustment instructions based on the category; the insulation parameter measurement module measures and calculates the insulation resistance R under the optimized signal; and the signal processing and output module is responsible for conditioning, converting, and calculating all signals and outputting the final insulation status information. Through the cooperation of hardware and software, this system fully realizes the aforementioned adaptive closed-loop monitoring logic.

[0170] In summary, by introducing a reflected signal detection and closed-loop adaptive adjustment mechanism, this invention not only solves the long-standing measurement interference problem, but also outputs the most reliable insulation resistance value after optimization and verification. At the same time, it provides additional dimension information reflecting the health of the system's electrical environment, achieving a significant advancement in insulation monitoring from static and open-loop to dynamic, closed-loop, and intelligent.

[0171] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for locating insulation faults in a power distribution network, characterized in that: Includes the following steps: S1. Inject a first test signal into the distribution network and obtain the strength parameters of the first test signal; S2. Detect and acquire the reflected signal caused by the first test signal in the power distribution network, and extract the intensity parameter of the reflected signal; S3. Based on the intensity of the first test signal and the intensity of the reflected signal, calculate the real-time status index reflecting the impedance matching degree of the system. S4. Determine the current operating status category of the distribution network based on the value of the real-time status indicator. S5. Based on the current operating state category, dynamically adjust and generate the injection intensity of the second test signal; S6. Use the second test signal to perform measurements to obtain optimized distribution network insulation status information.

2. The insulation fault location method for a power distribution network according to claim 1, characterized in that: S1 further includes the following: A first test signal with a preset frequency, waveform, and voltage amplitude is generated by a signal generator. The first test signal is injected between the target phase line and the system ground of the distribution network via a signal coupler; The voltage amplitude of the first test signal is used as the intensity parameter of the first test signal; Wherein, the target phase line is the live conductor to be monitored in the distribution network, and the system ground serves as a common potential reference point for signal injection and measurement.

3. The insulation fault location method for a power distribution network according to claim 1, characterized in that: S2 further includes the following: Using the signal coupler, the signal component reflected back to the injection point from the total signal at the injection point is separated; The signal components are sequentially subjected to signal conditioning and analog-to-digital conversion to obtain a digitized reflected signal; The root mean square (RMS) operation is performed on the digitized reflected signal, and the result is used as the intensity parameter of the reflected signal.

4. The insulation fault location method for a power distribution network according to claim 1, characterized in that: S3 further includes the following: Based on the first test signal strength parameter Ai and the reflected signal strength Ar, the ratio k of the reflected signal strength Ar to the first test signal strength parameter Ai is calculated using the following formula: k = Ar / Ai; When the ratio k is greater than 1, the value of k is corrected to 1; The ratio k is input to a preset transformation function F(k), which is configured to perform a nonlinear transformation on the input value, as shown in the following formula: F(k)=1-k 2 ; The output value of the conversion function F(k) is mapped to a preset continuous numerical range, the upper limit and the lower limit of which correspond to the theoretical best state and the theoretical worst state of the system impedance matching degree, respectively. The continuous values ​​obtained after the mapping are determined as the real-time status index H that reflects the impedance matching degree of the system.

5. The insulation fault location method for a power distribution network according to claim 1, characterized in that: S4 further includes the following: Based on the current value H(t) of the real-time status index H and the historical value H(t-1) of the real-time status index H in the previous calculation period, calculate the difference ΔH between the current value H(t) and H(t-1). Based on the threshold range in which the current value H(t) is located and the sign of the difference ΔH, the current operating state of the distribution network is classified into one of the four discrete state categories.

6. The insulation fault location method for a power distribution network according to claim 5, characterized in that: Based on the threshold interval in which the current value H(t) is located and the positive or negative of the difference ΔH, classify the current operating state of the distribution network into one of four discrete state categories, including: When H(t)≥Hhigh and ΔH≥0, it is determined as the first state category, and the first state category represents that the system impedance matching is in a stable matching state; When H(t)≥Hhigh and ΔH<0, it is determined as the second state category, and the second state category represents that the system impedance matching is in a matching attenuation state; When Hmid≤H(t)<Hhigh, it is determined as the third state category, and the third state category represents that the system impedance matching is in a critical matching state; When H(t)<Hmid, it is determined as the fourth state category, and the fourth state category represents that the system impedance matching is in a mismatched state; Where, Hhigh and Hmid are preset thresholds, and Hhigh>Hmid.

7. The insulation fault location method for a power distribution network according to claim 6, characterized in that: The S5 further includes the following content: According to the determined operating state category, generate an instruction to control the voltage amplitude U2 of the second test signal output by the signal generator according to a preset intensity adjustment rule; Where, the intensity adjustment rule is configured as follows: For the first state category, generate an instruction to increase the voltage amplitude U2 of the second test signal according to a preset value; [[ID=⑩]]For the second state category, generate an instruction to keep the voltage amplitude U2 of the second test signal; For the third state category, generate an instruction to decrease the voltage amplitude U2 of the second test signal according to a preset value; For the fourth state category, generate an instruction to set the voltage amplitude U2 of the second test signal to zero.

8. The insulation fault location method for a power distribution network according to claim 7, characterized in that: The S6 further includes the following content: Measure the leakage current flowing through the connecting wire between the signal coupler and the system ground under the action of the second test signal to obtain a leakage current signal; Obtain a reference signal generated by the signal generator and synchronized with the voltage of the second test signal; Multiply the leakage current signal by the reference signal, and perform filtering on the multiplication result to extract the component in the leakage current signal that is in the same phase as the voltage of the second test signal as the resistive current component I; According to the voltage amplitude U2 of the second test signal and the resistive current component I, calculate the current insulation resistance value R of the distribution network, and the formula is as follows: R = U2 / I; Take the insulation resistance value R, the real-time state index H and the determined current operating state category as the optimized insulation state information of the distribution network.

9. An insulation fault location system for a distribution network, applied to an insulation fault location method for a distribution network according to any one of claims 1-8, characterized in that: It includes a signal generation and injection module, a first signal intensity acquisition module, a reflected signal detection and extraction module, a state index calculation module, an operating state determination module, a signal intensity dynamic adjustment module, an insulation parameter measurement module, and a signal processing and output module; The signal generation and injection module is used to generate a test signal with preset characteristics and inject the test signal between the target phase line and the system ground of the distribution network. The first intensity acquisition module is used to acquire the intensity parameters of the first test signal; The reflected signal detection and extraction module is used to detect and separate the signal components reflected back to the injection point from the distribution network, and extract the intensity parameters of the reflected signal. The state index calculation module is used to calculate a real-time state index H that reflects the impedance matching degree of the system based on the intensity parameters of the first test signal and the intensity parameters of the reflected signal. The operation status determination module is used to determine the current operation status category of the distribution network based on the value and changing trend of the real-time status indicator H. The signal strength dynamic adjustment module is used to dynamically adjust and generate the injection strength command of the next test signal according to the determined operating state category and preset rules. The insulation parameter measurement module is used to measure leakage current, extract resistive current components, and calculate the insulation resistance value of the distribution network based on the adjusted second test signal. The signal processing and output module is used to condition, convert analog to digital, and perform calculations on the measurement signal, and output the optimized distribution network insulation status information.

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