Development and Application of Pole-Mounted Fully Insulated and Visualized Low-Voltage Load Transfer Device in Distribution Network

In distribution network, safe, reliable and fast operation of low-voltage load transfer device plays a vital role in power supply reliability. In this paper, a new 0. 4kV pole-mounted fully insulated and visualized load transfer device (PFIVLTD) is developed, which solves the problems of conventional jumper wire device(JWD), such as high current of single-phase operation, high resistance augmentation rate at contact points, susceptibility to aging of the insulation, clamps liable to break by an external force, and high risk and inefficient operation, and it has the advantages of full insulation and visualization, safety and convenience, economy and reliability. PFIVLTD realizes the intrinsic insulation through a fully insulated and fully enclosed design and ensures the remote visualization of the state of switch through a transparent viewable window at the bottom. Three-phase linkage switch, compact spring operating mechanism, and operating handle design changed the load-transfer-way from single-phase-sequential-operate for thrice direct contact to three-phase-operate for once indirect contact, it also reduced the load transfer operation time of the overhead line from 20 minutes to 3 minutes, and improved the safety and efficiency of 0. 4kV uninterrupted operation. PFIVLTD has been applied in many places in Shanghai City, China since 2022. Engineering practice demonstrated that the new PFIVLTD effectively reduced the tripping rate of overhead line, shortened the user outage time, and enhanced the safety of load transfer operation in contrast with conventional JWD, which provides strong support for maintaining Average Service Availability Index (ASAI) of power supply reliability above 99.999% in Shanghai urban area in 2022.