CN-122017459-A - Insulation fault positioning system and method for power distribution network

CN122017459ACN 122017459 ACN122017459 ACN 122017459ACN-122017459-A

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, wherein the method comprises the steps of injecting a first test signal into the power distribution network and obtaining the strength 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 reflected signal and the intensity of the reflected signal, judging that the system is in one of four state categories of stable matching, matching attenuation, critical matching and mismatch at present based on the numerical value of the H and the variation trend of the numerical value, dynamically adjusting the injection intensity of a second test signal according to the state categories, and finally measuring leakage current and calculating an insulation resistance value by using the second test signal.

Inventors

ZHU XIANG
CAO QICHAO
LV ZHONGHUA
YANG YI
SHENG YUE

Assignees

江苏卓特电气科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260225

Claims (9)

1. The insulation fault positioning method for the power distribution network is characterized by comprising the following steps of: s1, injecting a first test signal into a power distribution network, and acquiring an intensity parameter of the first test signal; S2, detecting and acquiring a reflected signal caused by the first test signal in the power distribution network, and extracting an intensity parameter of the reflected signal; S3, calculating to obtain a real-time state index reflecting the impedance matching degree of the system according to the intensity of the first test signal and the intensity of the reflected signal; s4, judging the current running state type of the power distribution network according to the numerical value of the real-time state index; s5, dynamically adjusting and generating injection intensity of a second test signal according to the current running state type; and S6, measuring by using the second test signal to obtain optimized insulation state information of the power distribution network.
2. The method for locating an insulation fault of a power distribution network according to claim 1, wherein S1 further comprises the following steps: generating a first test signal with preset frequency, waveform and voltage amplitude by a signal generator; Injecting the first test signal between a target phase line and a system ground of the power distribution network through a signal coupler; Taking the voltage amplitude of the first test signal as a strength parameter of the first test signal; The target phase line is a live conductor to be monitored in the power distribution network, and the system ground is used as a common potential reference point for signal injection and measurement.
3. The method for locating an insulation fault of a power distribution network according to claim 1, wherein S2 further comprises the following steps: separating a signal component reflected by the distribution network back to the injection point from the total signal at the injection point by using the signal coupler; Sequentially carrying out signal conditioning and analog-to-digital conversion on the signal components to obtain a digitized reflected signal; and carrying out root mean square operation on the digitized reflected signals, and taking an operation result as an intensity parameter of the reflected signals.
4. The method for locating an insulation fault of a power distribution network according to claim 1, wherein S3 further comprises the following steps: Calculating the ratio k of the reflected signal intensity Ar to the first test signal intensity parameter Ai according to the first test signal intensity parameter Ai and the reflected signal intensity Ar, wherein the formula is as follows: k=Ar/Ai; When the ratio k is greater than 1, correcting the value of k to be 1; the ratio k is input to a preset conversion function F (k) configured to perform nonlinear transformation on the input value, and the formula is as follows: F(k)=1-k 2 ; mapping the output value of the conversion function F (k) to a preset continuous numerical value interval, wherein the upper limit value and the lower limit value of the interval respectively correspond to a theoretical optimal state and a theoretical worst state of the impedance matching degree of the system; and determining the continuous numerical value obtained after the mapping is completed as the real-time state index H reflecting the impedance matching degree of the system.
5. The method for locating an insulation fault of a power distribution network according to claim 1, wherein S4 further comprises the following steps: calculating a difference delta H between a current value H (t) and a current value H (t-1) of the real-time state index H according to the current value H (t) of the real-time state index H and a historical value H (t-1) of the real-time state index H in a previous calculation period; and classifying the current running state of the power 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 and negative of the difference value delta H.
6. An insulation fault locating method for a power distribution network according to claim 5, wherein: The classifying the current operation state of the power distribution network into one of four discrete state categories based on the threshold interval where the current value H (t) is located and the positive and negative of the difference value Δh includes: when H (t) is not less than Hhigh and delta H is not less than 0, judging a first state type, wherein the first state type represents that the impedance matching of the system is in a stable matching state; when H (t) is not less than Hhigh and delta H is less than 0, judging a second state type, wherein the second state type represents that the impedance matching of the system is in a matching attenuation state; When Hmid is less than or equal to H (t) < Hhigh, determining a third state class, wherein the third state class represents that the impedance matching of the system is in a critical matching state; When H (t) < Hmid, determining a fourth state class, the fourth state class characterizing that the system impedance match is in a mismatched state; wherein Hhigh and Hmid are preset thresholds and Hhigh > Hmid.
7. The method for locating an insulation fault in a power distribution network according to claim 6, wherein S5 further comprises the following steps: generating an instruction for controlling the signal generator to output the voltage amplitude U2 of the second test signal according to the determined running state type and a preset intensity adjustment rule; Wherein the intensity adjustment rule is configured as follows: Generating an instruction for increasing the voltage amplitude U2 of the second test signal according to a preset value for the first state class; generating instructions for maintaining the second test signal voltage magnitude U2 for the second state class; generating an instruction for reducing the voltage amplitude U2 of the second test signal according to a preset value for the third state class; For the fourth state class, instructions are generated for setting the second test signal voltage amplitude U2 to zero.
8. The method for locating an insulation fault in a power distribution network according to claim 7, wherein S6 further comprises the following steps: measuring leakage current flowing through a connecting wire between the signal coupler and system ground under the action of the second test signal to obtain a leakage current signal; Acquiring a reference signal generated by the signal generator in synchronization with the second test signal voltage; multiplying the leakage current signal with the reference signal, and filtering the multiplication result to extract a component which represents the leakage current signal and is in phase with the voltage of the second test signal, and the component is used as a resistive current component I; according to the voltage amplitude U2 of the second test signal and the resistive current component I, the current insulation resistance value R of the power distribution network is calculated according to the following formula: R=U2/I; and taking the insulation resistance value R, the real-time state index H and the determined current running state type as the optimized insulation state information of the power distribution network.
9. An insulation fault locating system for a power distribution network, applied to the insulation fault locating method for the power distribution network according to any one of claims 1-8, characterized in that: The system comprises 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 operation state judgment 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 for generating a test signal with preset characteristics and injecting the test signal between a target phase line and a system ground of the power distribution network; The first intensity acquisition module is used for acquiring intensity parameters of the first test signal; The reflected signal detection and extraction module is used for detecting and separating out a signal component reflected back to the injection point from the injection point and extracting the intensity parameter of the reflected signal; The state index calculation module is used for calculating a real-time state index H reflecting the impedance matching degree of the system according to the intensity parameter of the first test signal and the intensity parameter of the reflected signal; The running state judging module is used for judging the current running state type of the power distribution network according to the numerical value of the real-time state index H and the change trend of the numerical value; The signal intensity dynamic adjustment module is used for dynamically adjusting and generating an injection intensity instruction of a next test signal according to the determined running state category and a preset rule; The insulation parameter measurement module is used for measuring leakage current, extracting resistive current components and calculating insulation resistance values of the power distribution network based on the adjusted second test signal; the signal processing and outputting module is used for conditioning, analog-to-digital converting and operating the measuring signal and outputting the optimized insulation state information of the power distribution network.

Description

Insulation fault positioning system and method for power distribution network Technical Field The invention relates to the technical field of insulation monitoring of power distribution networks, in particular to an insulation fault positioning system and method for a power distribution network. Background In an alternating current ungrounded (IT) or high-resistance grounded (ITN) power distribution network, an insulation on-line monitoring system is important for guaranteeing power supply safety. Currently, the mainstream monitoring technology generally adopts a signal injection method, namely, a low-frequency voltage signal with a specific frequency is injected between a power grid and the ground, and parameters such as insulation resistance of a system are calculated by detecting leakage current generated by the signal injection method. However, the method has an inherent technical contradiction that the measurement accuracy requirement and the electromagnetic compatibility (EMC) requirement of the system are directly conflicting, on one hand, in order to accurately detect weak leakage current in a complex noise environment, particularly when the insulation resistance is high, signals with enough strength are needed to be injected to ensure the measurement signal to noise ratio, on the other hand, the excessively strong injection signals can generate electromagnetic interference on sensitive loads in a power grid, so that the normal operation of the power grid is influenced, and even the resonance of distributed parameters of the system is possibly excited, so that potential safety hazards are brought. To address this conflict, the prior art generally employs a static, conservative compromise. For example, the amplitude of the injected signal is fixedly preset at a lower conservative level according to the most severe application scene standard, and another improvement idea is to use a heuristic strategy to gradually increase from the minimum signal until a valid response is detected. However, these methods are essentially open loop control, i.e. the process of setting or adjusting the signal strength, and do not perform closed loop optimization according to the feedback of the influence of the real-time state of the power grid after the injection. Thus, the system cannot dynamically trade off between the two goals of "achieving optimal measurement sensitivity" and "ensuring that electromagnetic interference is minimized". When the grid load changes dynamically, a fixed pre-try may lead to measurement delays or misalignments due to the signal being too weak, whereas a simple incremental rule may cause unnecessary transient disturbances in the adjustment process. In summary, how to realize high-precision and rapid self-adaptive monitoring of insulation parameters on the premise of not affecting normal operation of a power grid is still a technical problem to be solved in the field. Disclosure of Invention The invention aims to provide an insulation fault positioning system and method for a power distribution network, which are used for solving the problems in the prior art. In order to achieve the above purpose, the present invention provides the following technical solutions: an insulation fault locating method for a power distribution network, comprising the following steps: s1, injecting a first test signal into a power distribution network, and acquiring an intensity parameter of the first test signal; S2, detecting and acquiring a reflected signal caused by the first test signal in the power distribution network, and extracting an intensity parameter of the reflected signal; S3, calculating to obtain a real-time state index reflecting the impedance matching degree of the system according to the intensity of the first test signal and the intensity of the reflected signal; s4, judging the current running state type of the power distribution network according to the numerical value of the real-time state index; s5, dynamically adjusting and generating injection intensity of a second test signal according to the current running state type; and S6, measuring by using the second test signal to obtain optimized insulation state information of the power distribution network. The S1 further comprises the following contents: generating a first test signal with preset frequency, waveform and voltage amplitude by a signal generator; Injecting the first test signal between a target phase line and a system ground of the power distribution network through a signal coupler; Taking the voltage amplitude of the first test signal as a strength parameter of the first test signal; The target phase line is a live conductor to be monitored in the power distribution network, and the system ground is used as a common potential reference point for signal injection and measurement. The S2 further includes the following: separating a signal component reflected by the distribution network back to the injection point from the tot