A method for on-line monitoring of medium voltage cable insulation based on shock impedance spectroscopy
A technology of impact impedance and cable insulation, applied in the direction of measuring resistance/reactance/impedance, measuring electricity, measuring devices, etc., can solve the problems of inability to obtain cable change laws, power grid safety hazards, weak measurement signals, etc., and achieve the frequency component of the impact signal. Rich, not easy to noise interference, high detection sensitivity effect
Active Publication Date: 2021-10-26
SICHUAN UNIV
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Problems solved by technology
[0006] In the prior art, the first two online monitoring methods of cable insulation belong to the online monitoring method of power cable insulation status under non-impulse voltage, and there are problems such as weak measurement signal, difficult signal acquisition, and difficult operation.
The last online monitoring method of cable insulation requires additional switching of high-voltage capacitors, which may cause harm to the safety of the power grid, and the minimum value of the impact impedance can only be used to obtain the insulation status of the cable in isolation, which cannot reflect the aging degree of the cable, let alone the different aging degrees of the cable. law of change
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[0041] Such as figure 1 As shown, the on-line monitoring method for medium-voltage cable insulation based on shock impedance spectroscopy provided by this embodiment includes the following steps:
[0042] S1 respectively collects the busbar voltage on the cable to be tested and the leakage current of the cable grounding wire in real time, records and extracts the busbar voltage V of a fixed time length during the impact transient process when lightning shock or operation shock occurs m (n) and cable ground wire leakage current data I m (n).
[0043] In the present embodiment, the busbar voltage on the cable 1 to be tested and the cable ground wire current pass through such as figure 2 The shown two-stage RC-based overvoltage on-line monitoring device specifically includes a capacitive voltage divider 2 composed of two capacitors connected in series, a hollow Rogowski coil 3 and an industrial computer 4 . The industrial computer 4 is provided with a data acquisition card 401...
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The invention discloses an on-line monitoring method for medium-voltage cable insulation based on shock impedance spectroscopy. The lightning shock and operation shock signals that are ubiquitous in the power system are used as excitations to monitor the current response on the cable grounding line and utilize the monitored lightning shock , Operate the shock signal and current signal to obtain the cable insulation impedance spectrum in the frequency domain, and further based on the amplitude change of the cable shock impedance spectrum and the shift of the resonant frequency point, the aging state of the cable insulation is judged, and then the online monitoring of the cable insulation is realized. The present invention uses the impulse voltage generated by lightning impulse and operation impulse to monitor the cable insulation state, which will generate a transient response with a strong amplitude on the cable grounding line, and the voltage and current signals are easy to be captured by the monitoring equipment, and the detection accuracy is high; and It is not susceptible to noise interference and can ensure the effectiveness of monitoring the cable insulation state.
Description
technical field [0001] The invention belongs to the technical field of electric power engineering, and relates to an on-line monitoring technology for the insulation state of electric cables, in particular to an on-line monitoring method for medium-voltage cable insulation based on shock impedance spectroscopy. Background technique [0002] The proportion of cable lines in the urban power supply lines of most cities has exceeded 50%. The insulating material is the weakest link of the cable body. Most cable faults are caused by the aging insulation breakdown of equipment. Once the cable breaks down, Long-term power-off maintenance must be carried out, which will bring great hidden dangers to the safe operation of cables, and then affect the reliability of power supply of the power grid, endangering the safety of the power grid and equipment. [0003] The patent application document with the application number CN201010513523.8 discloses a method and device for on-line monitori...
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IPC IPC(8): G01R27/02G01R31/12
CPCG01R27/02G01R31/1272
Inventor 周凯龚薇奚航黄永禄孟鹏飞
Owner SICHUAN UNIV