It prevents misoperation and effectively protects personal and equipment safety. Taking the vacuum solid-insulated ring main unit (RMU) produced by DAYA Electric Group Co., Ltd. as an example, the vacuum load switch adopted in this product is a high-voltage switchgear with three positions: isolation, closing, and grounding. The isolating switch and earthing switch have visible breakpoints, and the load switch and isolating switch feature an automatic interlocking function. Specifically, when the vacuum load switch is opened, the isolating switch automatically opens to form a visible breakpoint; when the vacuum load switch is closed, the isolating switch automatically closes first. Additionally, the load switch and earthing switch are equipped with strict mechanical interlocks and electrical interlocks, structurally ensuring that misoperation between them is impossible. That is, when the load switch is in the closed position, the earthing switch cannot be closed, and vice versa. Once the front door of the solid-insulated RMU is opened, the load switch can no longer be closed, thereby effectively preventing misoperation.
It boasts high performance indicators. The vacuum and SF₆ load switches used in vacuum solid-insulated RMUs and SF₆ solid-insulated RMUs are designed for frequent operation. Their rated number of "closing-opening" cycles under active load can reach 100 times, more than 10 times that of general load switches such as gas-generating and pressure-gas load switches. They also possess excellent breaking capacity, with a short-time withstand current typically reaching 20 kA and a short-circuit closing current generally up to 50 kA.
It is convenient for maintenance. Solid-insulated RMUs in high and low-voltage complete sets of equipment are usually installed in power distribution rooms, avoiding risks such as vehicle collisions, man-made damage, and flooding that may affect ring network cable distribution boxes. Indoor operation and maintenance also minimize the impact of weather on operations. The clear panel design on the cabinet surface displays the wiring method in the form of a schematic diagram, making it easy to understand at a glance. Some manufacturers further mark operation guidelines and precautions on the cabinet surface, which reduces the possibility of misoperation by operators. Most products are equipped with a live display device that can monitor the live status of the main circuit. This device not only indicates the high-voltage live condition but also can cooperate with electromagnetic locks to achieve forced locking of the handle door, enhancing anti-misoperation performance. The transparent organic glass observation window installed on the front door allows direct viewing of the opening and closing status of the load switch.
It is flexible in use and easy to expand. With the accumulation of operational experience, expandable solid-insulated RMUs are gradually replacing the previous fully enclosed solid-insulated RMUs. Thanks to advancements in compact design and modular splicing, current configurations can flexibly meet the requirements of various design schemes and realize arbitrary combinations according to customers' actual needs. The connection method of cable trays is also more flexible; even when the ground is not flat enough, soft connection can be achieved without partial discharge. It is equipped with an automation interface, laying the foundation for the construction of distribution automation.
There is a wealth of knowledge about cable distribution boxes. It is hoped that users will thoroughly understand the characteristics of the installation environment of cable distribution boxes to lay a solid foundation for safe and effective use in the later stage. Meanwhile, the editor from DAYA will continue to introduce more knowledge about cable distribution boxes to help you gain a deeper understanding of them. For more information, please follow DAYA Electric Group Co., Ltd. (https://www.hygraphics.com/). We will update the content irregularly.