Construction of Novel Online Partial Discharge Monitoring System in Model Power Apparatus Using Power Line Communication

Abstract

In recent years, partial discharge (PD) measurement attracts attention as insulation diagnosis of power equipment. A lower-cost and higher sensitive detection method is required, but it has not been established yet. In this research, an attempt is made to apply a ferrite core (FC), usually used for suppression of high frequency noise in electric circuit, and power line communication (PLC), known as a data communication on AC power transmission. By combining those tools, we aim to develop the low cost and high sensitive continuous monitoring technique. In the previous paper, the frequency characteristic of impedance of FC was clarified and PD measurement using FC was performed. This paper presents a novel concept of PD detection by PLC and FC, constructed test circuit and experimental verification. In general, PLC is used for information communication by superimposing the data on distribution systems with commercial frequency. Principle of the novel PD measurement using PLC is as follows: PD measurements are made by injecting PD signal generated in an artificial defect model into the constructed test circuit consisting of PLC and FC. The inductance component of FC causes dominant frequency band that PD signal originally possesses to shift to the frequency band allowable to transmit in PLC between 2 MHz and 28 MHz. In addition, the impedance of the FC amplifies the signal intensity detected from a test lead connected to the two terminals in the ground line. In principle, PD detection can be realized by identifying the PD signal as a noise signal in the communication frequency region of PLC. Note that PD signal causes a communication error resulting in an abnormal state in PLC. The novel PD detection method extracts PD signal as a disturbance from the communication signal. An attempt is also made to measure PD using the constructed monitoring system so as to verify the PD detection principle.