Research And Design Of Partial Discharge Detect System In High-voltage Cable Accessories Based On UHF

Power cable has been widely applied in the power system, and the cable accessories (including intermediate connector and terminal head) is a vital part of the power cable. Cable accessories are the weakest link and run the most typical failure site due to their comlex internal structure. Partial Discharge (PD) is the main reason of cable accessories’early insulation failure. Therefore, cable accessories partial discharege detection has a far-reaching theoretical significance and practical value to protect the safe operation of the cable.This paper integrates antenna theory and electrical measurement technology to research the partial discharge detection of cross-linked polyethylene (XLPE)cable accessories based on Ultra High Frequency(UHF)technology. The main contents are as follows:The existence of multi-layer composite interface in the complex inner structure of cable accessories increases the difficulties of signal detection methods. According to the propagation characteristics of UHF electromagnetic wave generated by partial discharge, the design requirements of UHF sensor used in partial discharge detection is researched, and an internally-installed flat gap antenna with simple structure is designed.The butterfly antenna is simulated through Ansoft HFSS software, the antenna’s structural size parameters and material properties are optimized. The butterfly antenna’s frequency band is widened by slot processing and so on, thus improving the antena’s performance. A butterfly antena sensor with the efficient bandwidth of365MHZ to577MHZ is finally developed. In order to recieve the electromagnetic wave generated by partial discharge, the Archimedes spiral antenna’a properties are calculated through theoretical analysis, the Archimedes spiral antenna is designed through Ansoft HFSS software. The antenna’s gain and direction property are improved by adding reflector cavity, thereby enhancing the sensitivity of PD detection. Meanwhile, the impedance matching is realized by applying an exponential gradient mcirostrip balun’s feed. An Archimedean spriral antenna sensor with bandwidth of0.7GHZ to3GHZ is finally developed, the butterfly antenna is measured by vector network analyzer.The high frequency processing software of Advanced Design System is applied, the appropriate circuit elements and corresponding circuit model are selected to design a preamplifier with operating frequency band of400MHz to800MHz and band-pass filter. In order to decrease the frequency of partial discharge signal, a detector based on high-frequency detector diode HSMS-2825is produced. The frequency of UHF signal collected by the sensor is reduce within2MHz to20MHz, thus substantially reducing the acquisition rate and data amount of data acquisition system. A two path high speed data acquisition system based on AD9481is designed, the acquisition speed is250Msps.Research shows that, the design of the UHF sensor (butterfly antenna and the Archimedes spiral antenna) can be used as a partial discharge detection sensor cable accessories, ultra high frequency detection circuit design can be used for partial discharge in high voltage cable testing system.