CN-122017681-A - Automatic detection method for online fault judgment of marine cable

CN122017681ACN 122017681 ACN122017681 ACN 122017681ACN-122017681-A

Abstract

The invention relates to the technical field of electric fault detection, in particular to an automatic detection method for online fault judgment of a marine cable, which is characterized in that the online early warning of insulation degradation is realized by collecting earth leakage current and load current in operation, extracting active components of the leakage current and analyzing nonlinear correlation between the active components and the load current; the method comprises the steps of positioning a fault branch based on the normalization result of the capacitance change to the ground before and after the power failure of each branch and the cable length when a ship is in a short-time power failure working condition of a part of a non-critical loop, judging the fault type by combining the fundamental wave and the phase voltage phase difference of leakage current and the harmonic distortion rate after power restoration, injecting a high-frequency carrier wave when power failure maintenance is performed, determining the position of a fault point according to the current attenuation abnormality, and correcting by combining the temperature and the vibration factor, thereby improving the detection accuracy and the positioning accuracy.

Inventors

CHEN GUANYU
ZENG GUANGBIN
XUE XIUJUAN
CHEN HUI
ZENG XIUJUAN
WU LIANJUN
WU LIANFEI

Assignees

扬州市红旗电缆制造有限公司

Dates

Publication Date: 20260512
Application Date: 20260324

Claims (7)

1. The automatic detection method for online fault judgment of the marine cable is characterized by comprising the steps of collecting earth leakage current and load current in operation, extracting active components of the leakage current, analyzing the correlation between the active components and the load current, and judging that an insulation degradation fault exists when the active components are in nonlinear positive correlation with the load current; When the ship is in a working condition that short-time power failure of a part of non-critical circuits is allowed, acquiring capacitance values to ground before and after each power-failure distribution branch is disconnected in sequence, calculating capacitance variation to ground of each branch, carrying out normalization processing on the capacitance variation and the cable length of the corresponding branch, and judging the branch as a fault branch according to the branch positioning of which the normalization value exceeds a normal range; After the power supply of each branch is restored, collecting earth leakage current and phase voltage aiming at a positioned fault branch, extracting the phase difference and harmonic distortion rate of the fundamental wave component and the voltage of the leakage current, and judging the fault type as insulation degradation, insulation breakdown and/or intermittent fault according to the combination characteristics of the phase difference and the harmonic distortion rate; When the fault branch circuit is powered off and overhauled, a high-frequency carrier signal is injected into the cable, high-frequency current amplitudes of a plurality of accessible positions along the cable are measured, and a fault point is determined according to a position section with abnormally increased high-frequency current attenuation rate between adjacent measuring points.
2. The automatic detection method for online fault judgment of marine cable according to claim 1, wherein the method comprises the following steps: the method comprises the steps of carrying out frequency spectrum decomposition on the collected leakage current to obtain a fundamental component, extracting a component of which the fundamental component is in phase with the phase voltage as an active component, and extracting a component of which the fundamental component is orthogonal with the phase voltage as a reactive component; The analysis of the correlation of the active component and the load current includes synchronously recording time series data of the active component and the load current within a continuous time window, calculating a rate of change of the active component to the load current, and determining a nonlinear positive correlation when the rate of change is greater than a first preset threshold and a monotonically increasing trend is maintained within a plurality of continuous time windows.
3. The automatic detection method for online fault judgment of marine cable according to claim 1, wherein the method comprises the following steps: The ship is in the working condition of allowing part of the non-critical loop to be powered off in a short time is judged by acquiring the rotating speed of a ship host, the rotating speed of a propeller, the load rate of a generator and the position information of the ship, and judging that the ship is in a port leaning working condition when the rotating speed of the host is lower than the set proportion of the rated rotating speed, the rotating speed of the propeller is zero and the position of the ship is in the port coordinate range; The normal range is determined by extracting the ratio of the capacitance to ground variable quantity and the length of the cables with the same model and the same specification, removing outliers with the mean value exceeding a set multiple, calculating the mean value and standard deviation of the residual ratio, and taking the interval of adding and subtracting 3 times of the standard deviation of the mean value as the normal range.
4. The automatic detection method for online fault judgment of marine cable according to claim 1, wherein the method comprises the following steps: Judging the fault type according to the combined characteristics of the phase difference and the harmonic distortion rate, wherein when the phase difference is between 90 degrees of capacitive advance and a set first angle of capacitive advance and the harmonic distortion rate is lower than a set first threshold value, the fault type is judged to be slightly insulating degradation; when the phase difference is between the first angle of the capacitive advanced setting and the second angle of the capacitive advanced setting and the harmonic distortion rate is lower than a second threshold value, judging that the insulation is moderately deteriorated; when the phase difference is between the capacitive advanced setting second angle and the in-phase and the harmonic distortion rate is higher than a set second threshold value, judging that the phase difference is insulation breakdown; And when the leakage current has intermittent pulse mutation and the mutation frequency exceeds a set frequency threshold value, judging that the leakage current is intermittent.
5. The automatic detection method for online fault judgment of marine cable according to claim 1, wherein the method comprises the following steps: The frequency of the high-frequency carrier signal is determined according to the length of the cable and the expected positioning precision, the total length of the cable of the fault branch is obtained, the minimum frequency required by calculation is calculated according to the propagation speed of the high-frequency signal in the cable and the required positioning precision, and the frequency avoiding the power interference frequency band of the ship is selected as the carrier frequency on the basis of the minimum frequency; The selection of the multiple accessible positions along the cable includes setting measurement positions at the head end of the cable, the positions of the branch junction boxes, the cabin penetrating sealing positions, the fixing points of the cable support and the tail end of the cable, and determining the intervals between the measurement positions according to the required positioning precision.
6. The automatic detection method for judging online faults of marine cables according to claim 1, further comprising the steps of continuously monitoring the amplitude change trend of the neutral point to ground voltage after judging that the insulation degradation faults exist, carrying out time sequence correlation analysis on the neutral point to ground voltage change trend and the leakage current active component change trend, and taking the neutral point to ground voltage change trend and the leakage current active component change trend as auxiliary confirmation basis of the insulation degradation faults when the neutral point to ground voltage monotonically increases and the leakage current active component shows synchronous increase trend.
7. The automatic detection method for judging online faults of a marine cable according to claim 1, further comprising the steps of collecting environmental temperature data at a plurality of positions along the cable, establishing a statistical relation model of active components of leakage current and environmental temperature, calculating an expected leakage current value based on temperature influence according to the current environmental temperature, comparing the actually measured active components of the leakage current with the expected value, and judging that the excess is abnormal leakage caused by insulation degradation when the actual value exceeds a set multiple of the expected value; Collecting vibration acceleration signals of a ship host, extracting main frequency and amplitude of vibration, carrying out frequency domain correlation analysis on time domain fluctuation of leakage current and/or capacitance to ground and the vibration signals, and judging that the vibration-induced intermittent fault is caused when the fluctuation frequency of the leakage current and/or the capacitance to ground is detected to be consistent with the main frequency of vibration and the correlation coefficient exceeds a set threshold value.

Description

Automatic detection method for online fault judgment of marine cable Technical Field The invention relates to the technical field of electric fault detection, in particular to an automatic detection method for online fault judgment of a marine cable. Background The marine power system is an isolated power grid, and an IT grounding mode is generally adopted for guaranteeing power supply continuity, namely, a neutral point is not grounded or high-resistance is grounded. The grounding mode is characterized in that the system is not tripped when the first insulation fault occurs, and can continue to operate, but if the second grounding fault occurs, the whole ship is possibly powered off, and the navigation safety is endangered. Therefore, the method has important significance in effective fault detection of the marine cable. The existing cable fault detection technology mainly comprises a time domain reflection method, a frequency domain reflection method, an insulation resistance measurement method, an on-line electrical parameter monitoring method and the like. However, the above-described techniques all have inherent drawbacks in marine scenarios. The power supply cables of the ship key systems such as steering engines, host control and navigation equipment do not allow power failure detection, so that the high-precision detection method requiring off-line operation cannot be applied. More importantly, when the first insulation fault occurs, the IT grounding system does not trip and the load still works normally, so that the electrical parameters such as current, voltage and the like do not generate abnormal characterization, and the on-line monitoring method based on the operation abnormality detection principle is completely disabled at the initial stage of the fault. Meanwhile, the marine cable is in an electrified running state from the installation date, and reliable health reference parameters cannot be established through power failure measurement, so that the existing fault judging method based on threshold comparison lacks effective comparison basis. Therefore, a detection method capable of realizing online automatic identification and accurate positioning of cable faults from normal operation signals under the conditions of no power failure and no abnormal representation of electrical parameters is needed. Therefore, an online fault judgment and automatic detection method for the marine cable is provided. Disclosure of Invention The invention aims to provide an on-line fault judging and automatic detecting method for a marine cable, which is used for realizing insulation degradation early warning by analyzing the correlation between an active component of leakage current and load current, positioning a fault branch based on capacitance change to ground under a specific working condition, and realizing fault type judgment and accurate positioning by combining phase difference, harmonic wave characteristics and high-frequency carrier attenuation. In order to achieve the above purpose, the present invention provides the following technical solutions: an automatic detection method for online fault judgment of a marine cable comprises the following steps: collecting earth leakage current and load current in operation, extracting active components of the leakage current, analyzing the correlation between the active components and the load current, and judging that insulation degradation faults exist when the active components are in nonlinear positive correlation with the load current; When the ship is in a working condition that short-time power failure of a part of non-critical circuits is allowed, acquiring capacitance values to ground before and after each power-failure distribution branch is disconnected in sequence, calculating capacitance variation to ground of each branch, carrying out normalization processing on the capacitance variation and the cable length of the corresponding branch, and judging the branch as a fault branch according to the branch positioning of which the normalization value exceeds a normal range; After the power supply of each branch is restored, collecting earth leakage current and phase voltage aiming at a positioned fault branch, extracting the phase difference and harmonic distortion rate of the fundamental wave component and the voltage of the leakage current, and judging the fault type as insulation degradation, insulation breakdown and/or intermittent fault according to the combination characteristics of the phase difference and the harmonic distortion rate; When the fault branch circuit is powered off and overhauled, a high-frequency carrier signal is injected into the cable, high-frequency current amplitudes of a plurality of accessible positions along the cable are measured, and a fault point is determined according to a position section with abnormally increased high-frequency current attenuation rate between adjacent measuring points. Preferably, extracting the