In residential areas requiring ring network power supply, many ring main unit (RMU) devices are often relocated due to residents' concerns about radiation. Some projects even cannot proceed for this reason. So, do ring main units really emit radiation? First, let's understand what a ring main unit is.
To improve power supply reliability and allow users to obtain power from two directions, the power supply network is usually connected into a ring structure, a mode referred to as "ring network power supply" for short. In AC 10kV power distribution systems such as industrial and mining enterprises, residential districts, ports, and high-rise buildings, due to the small load capacity, the high-voltage circuits are typically controlled by load switches or vacuum contactors and equipped with high-voltage fuses for protection. This system commonly adopts ring network power supply, and the high-voltage switchgear used is customarily called a "ring main unit".
In addition to supplying power to the local substation, the high-voltage bus of the RMU also needs to carry the through current of the ring power supply network (i.e., the current that supplies power to adjacent substations through the bus of the local substation). Therefore, the cross-sectional area of the high-voltage bus of the RMU should be selected based on the sum of the load current of the local substation and the through current of the ring network to ensure that the high-voltage bus does not operate overloaded during operation. Currently, there are various types of RMU products available, such as the HK-10, MKH-10, 8DH-10, XGN-15, and SM6 series.
A ring main unit is a type of electrical equipment consisting of a set of high-voltage switchgear installed in a steel plate metal cabinet or configured as an assembled compartmentalized ring network power supply unit. Its core components include load switches and fuses, featuring advantages such as a simple structure, small size, low cost, improved power supply parameters and performance, and enhanced power supply safety. It is widely used in power distribution stations at load centers (e.g., urban residential districts, high-rise buildings, large public buildings, factories and enterprises) as well as in box-type substations.
Nowadays, underground cable laying has become the mainstream method for cable installation across the country. As a result, many ring main units and power distribution cabinets have faced doubts about radiation during site selection, which is completely unnecessary. From the above, we can learn that the so-called "ring main unit" means each distribution branch is equipped with one switchgear (outgoing line switchgear), and the bus of this switchgear is also part of the ring main line—there is no radiation. Power distribution cabinets only contain cables without exposed wires that can generate radiation. Moreover, in some central substation in cities, there are even 110kV ones. With the advancement of power technology, power workers often perform live-line operations. Therefore, people should not have concerns.
The editor from DAYA will continue to introduce more knowledge about high-voltage ring main units to help you gain a deeper understanding of cable distribution boxes. For more information, please follow DAYA Electric Group Co., Ltd. (https://www.hygraphics.com/). We will update content irregularly.