Free Expert Guides on Power Systems, Circuit Design & Electrical Troubleshooting

1. Specific Design1.1 Design ConceptState Grid Corporation of China actively promotes grid energy conservation and low-carbon development to achieve national carbon peak (2030) and neutrality (2060) goals. Environmentally friendly gas-insulated ring main units represent this trend. A new 12kV integrated environmentally friendly gas-insulated ring main unit was designed combining vacuum interrupter technology with three-position disconnectors and vacuum circuit breakers. The design utilized Solid

This article introduces a case of 35kV ring main unit busbar insulation breakdown failure, analyzes the failure causes and proposes solutions [3], providing reference for the construction and operation of new energy power stations.1 Accident OverviewOn March 17, 2023, a photovoltaic desertification control project site reported a ground fault trip accident in the 35kV ring main unit [4]. The equipment manufacturer arranged a team of technical experts to rush to the site to investigate the cause

Intelligent complete sets of electrical switchgear and intelligent controller products are essential components in the manufacturing of intelligent ring main units (RMUs). The intelligent integration of complete switchgear combines advanced manufacturing technologies with information technology, effectively enhancing the power grid’s capabilities in state awareness, data analysis, decision-making, control, and learning, thereby fully embodying the digital, networked, and intelligent development

Air-insulated ring main units (RMUs) are defined in contrast to compact gas-insulated RMUs. Early air-insulated RMUs used vacuum or puffer-type load switches from VEI, as well as gas-generating load switches. Later, with the widespread adoption of the SM6 series, it became the mainstream solution for air-insulated RMUs. Similar to other air-insulated RMUs, the key difference lies in replacing the load switch with an SF6-encapsulated type—where the three-position switch for load and grounding is

Expected service life of 30–40 years, front access, compact design equivalent to SF6-GIS, no SF6 gas handling – climate-friendly, 100% dry air insulation. The Nu1 switchgear is metal-enclosed, gas-insulated, featuring a withdrawable circuit breaker design, and has been type-tested according to relevant standards, approved by the internationally recognized STL laboratory.Compliance Standards Switchgear: IEC 62271-1 High-voltage switchgear and controlgear – Part 1: Common specifications for altern

Solid insulation assistance combined with dry air insulation is a development direction for 24 kV ring main units. By balancing insulation performance and compactness, the use of solid auxiliary insulation allows passing insulation tests without significantly increasing phase-to-phase or phase-to-ground dimensions. Encapsulation of the pole can address the insulation of the vacuum interrupter and its connected conductors.For the 24 kV outgoing busbar, with the phase spacing maintained at 110 mm,

Ring main units (RMUs) are used in secondary power distribution, directly connecting to end-users such as residential communities, construction sites, commercial buildings, highways, etc.In a residential substation, the RMU introduces 12 kV medium voltage, which is then stepped down to 380 V low voltage through transformers. The low-voltage switchgear distributes electrical energy to various user units. For a 1250 kVA distribution transformer in a residential community, the medium-voltage ring m

1. IntroductionRing main units (RMUs) are primary power distribution equipment that house load switches and circuit breakers within a metal or non-metal enclosure. Due to their compact size, simple structure, excellent insulation performance, low cost, easy installation, and fully sealed design [1], RMUs are widely used in medium- and low-voltage power systems across China’s grid network [2], especially in 10 kV distribution systems. With economic growth and increasing electricity demand, requir

1. Insufficient Creepage Distance or Air ClearanceInadequate creepage distance and air gaps are the main causes of insulation failure and accidents in solid-insulated ring main units (RMUs). Especially in drawer-type cabinets, manufacturers reduce cabinet size by minimizing space for circuit breakers, significantly decreasing isolation distances between plug contacts and ground. Without adequate reinforcement of insulation structure, such designs increase the risk of flashover under overvoltage

1. Ring Main Unit (RMU) and Transformer SubstationThe ring main unit (RMU) and transformer substation is a critical terminal in a distribution ring network system. The operational status of this terminal is directly affected by the performance of the distribution ring network system. Therefore, this section discusses the advantages, system composition, and key characteristics of the distribution ring network.1.1 Advantages of RMU and Transformer SubstationDue to technological limitations, radial