“10KV Changming Line #1 Ring Main Unit Distributed Low-frequency and Low-voltage Equipment’s 3^rd round of low-frequency action is correct, and the data uploading succeeds.” On February 14, State Grid Laiwu Power Supply Company’s smart grid dispatching and control system received the signal, marking State Grid’s first PDN distributed low-frequency and low-voltage equipment, participated in by Dongfang Electronics Corporation (DFE), has got through debugging and officially come into pilot running. 

Amid the backdrop that distributed PV has been massively put into running in recent years, 10KV power distribution lines frequently encountered inverse power transmission problem at noon time, so that load shedding amount in low-frequency and low-voltage load shedding scheme fails to meet system requirements. If smart low-frequency and low-voltage equipment that can discriminate power direction is installed at the transformer substation, it can rule out the likelihood of erroneous load shedding at the time of inverse supply, but it is unable to fundamentally raise load shedding amount.

Laiwu Power Supply Company, based on the principle “Realistic and Pragmatic, Addressing both Symptoms and Root Cause”, stressed precise load control and developed PDN distributed low-frequency and low-voltage equipment in conjunction with DFE. According to real conditions, it developed two modes of equipment and made use of optical cable or wireless 5G communication, living up to adaptation to local condition and quick rise of the third defense line’s load shedding level. Regarding the two modes, the first one is integration of low-frequency and low-voltage load shedding feature with ring main unit and pole-mounted distribution automation terminal. As a result, the upgrading and revamping is simple, and communication path keeps unchanged, which facilitates quick popularization and application; the second one is installation of separate distributed low-frequency and low-voltage equipment at ring main unit and pole-mounted switch, which facilitates  matchmaking with aviation connector, and the equipment is small-sized and reliable. Laiwu Power Supply Company has installed two modes of distributed low-frequency and low-voltage equipment at 10 KV Changming Line #1 ring main unit, 10 KV Xiangshan Line Xiyu Branch Line #5 ring main unit, and 10 KV Fangxing Line #12 pole-mounted section switch respectively. It adopted wired and 5G communication, and discriminated load for the people’s livelihood from the load for industry and commerce while preserving distributed PV output support. That helps ensure precise load shedding, tap load shedding potential to the maximum extent, realize all-around monitoring in the energy management system, and guarantee safety of the power grid’s third defense line.

With massive grid connection of distributed power supply, active power distribution network(PDN) brings about low-frequency and low-voltage load shedding measures’ approaching to lower safety limit. In view of this, DFE assisted Laiwu Company in making active explorations and embarking on Early and Pilot Implementation, in order to proactively shatter technical problem resulting from massive grid connection of distributed power supply. In the future, DFE will further contribute to development of new-type power system, keep expanding distributed low-frequency and low-voltage equipment application scenarios, quickly popularize use of the equipment in different scenarios (including important user line, hybrid line of various load natures, industrial user power distribution room connecting with distributed PV), and ensure safe and steady running of the power grid.