Online monitoring method for insulation state of cable for transformer substation

An online monitoring method for insulation status of substation utility cables, comprising:

• selecting a to-be-monitored cable;
• connecting one end of the to-be-monitored cable to a primary monitoring device through a first coupler and connecting the other end of the to-be-monitored cable to a secondary monitoring device through a second coupler, wherein one end of the to-be-monitored cable is connected to the primary monitoring device through the first coupler and the other end of the to-be-monitored cable is connected to the secondary monitoring device through the second coupler;
• sending, by the primary monitoring device, a first high-frequency test signal and injecting the first high-frequency test signal into the to-be-monitored cable through the first coupler;
• collecting, by the primary monitoring device, a first high-frequency reflected signal in the to-be-monitored cable through the first coupler, performing signal processing on the first high-frequency reflected signal by using a frequency-domain peak iterative search algorithm, and extracting first reflection point parameter information which is configured to characterize position and energy of a reflection point in the to-be-monitored cable corresponding to the first high-frequency reflected signal;
• sending, by the secondary monitoring device, a second high-frequency test signal and injecting the second high-frequency test signal into the to-be-monitored cable through the second coupler;
• collecting, by the secondary monitoring device, a second high-frequency reflected signal in the to-be-monitored cable by using through the second coupler, performing signal processing on the second high-frequency reflected signal by using the frequency-domain peak iterative search algorithm, and extracting second reflection point parameter information which is configured to characterize position and energy of a reflection point in the to-be-monitored cable corresponding to the second high-frequency reflected signal;
• performing, by the primary monitoring device and the secondary monitoring device, information interaction, and after the second reflection point parameter information is acquired, determining insulation aging status of the to-be-monitored cable;
• and
• ending detection;
• wherein the frequency-domain peak iterative search algorithm comprises:
• inputting the first high-frequency reflected signal or the second high-frequency reflected signal into a divider to perform the signal processing;
• outputting a result of the signal processing and transferring the result to a Fast Fourier Transform (FFT) module;
• calculating a frequency-domain signal amplitude through an amplitude calculation module, a maximum amplitude search module, a maximum amplitude number storage module, and a maximum amplitude zeroing module in sequence;
• and performing two iterative searches and calculating, by a reflection information calculation module, the first reflection point parameter information or the second reflection point parameter information.