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It is generally acknowledged that high voltage direct current (HVDC) transmission line endures the drawback of large area, because of which the utilization of cable for space charge density monitoring system is of inconvenience. Compared with the traditional communication network, wireless sensor network (WSN) shows advantages in small volume, high flexibility and strong self-organization, thereby presenting great potential in solving the problem. Additionally, WSN is more suitable for the construction of distributed space charge density monitoring system as it has longer distance and higher mobility. A distributed wireless system is designed for collecting and monitoring the space charge density under HVDC transmission lines, which has been widely applied in both Chinese state grid HVDC test base and power transmission projects. Experimental results of the measuring system demonstrated its adaptability in the complex electromagnetic environment under the transmission lines and the ability in realizing accurate, flexible, and stable demands for the measurement of space charge density. [ABSTRACT FROM AUTHOR]

It is known that the high-voltage direct-current (HVdc) transmission projects are increasingly used in actual electrical power transmission and the ion-flow field at ground level has been systematically studied. However, few studies focused on the research of the consistency among ion-flow density measurement systems (IDMS). IDMS should keep good concordance to discover the distribution law of ion-flow density in HVdc research. This study proposes an improved gray relational analysis (IGRA) method for consistency test of IDMS by introducing an entropy weight method and interval estimation method. Using this method, the consistency among IDMS is analyzed. The calibration assessment experiment was conducted and the results can be used for calibration assessment. The fault diagnosis experiment with +120 kV was also performed and findings show that the IGRA method is effective in finding potential fault for IDMS compared to the GRA method. Overall, results demonstrate that the IGRA method presented in this paper is useful for discovering distribution law of ion-flow density in HVdc research. [ABSTRACT FROM AUTHOR]