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

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

For SF6 gas leakage rate detection in GIS equipment, when using the quantitative leak detection method, the initial SF6 gas content in the GIS equipment must be accurately measured. According to relevant standards, the measurement error should be controlled within ±0.5%. The leakage rate is calculated based on changes in gas content after a period of time, thereby evaluating the sealing performance of the equipment.In qualitative leak detection methods, direct visual inspection is commonly used,

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

Power Supply Procedure for Low-Voltage Electrical RoomsI. Pre-Power-On Preparations Clean the electrical room thoroughly; remove all debris from switchgear and transformers, and secure all covers. Inspect busbars and cable connections inside transformers and switchgear; ensure all screws are tightened. Live parts must maintain adequate safety clearance from cabinet enclosures and between phases. Test all safety equipment before energizing; use only calibrated measuring instruments. Prepare fire-

Differences Between Ring Main Units (RMUs) and SwitchgearIn power systems, both ring main units (RMUs) and switchgear are common distribution equipment, but they differ significantly in function and structure. RMUs are primarily used in ring-fed networks, responsible for power distribution and line protection, with the key feature being multi-source interconnection through a closed-loop ring network. Switchgear, as a more general-purpose distribution device, handles power reception, distribution

Currently, China's medium-voltage distribution networks predominantly operate at 10kV. With rapid economic development, power loads have surged, increasingly exposing the limitations of the existing power supply methods. Due to the outstanding advantages of 24kV high-voltage switchgear in meeting higher load capacity demands, it has quietly gained traction within the industry. Following the State Grid Corporation's "Notice on Promoting the 20kV Voltage Level," the 20kV voltage class has seen a r

I. Routine Maintenance and Inspection(1) Visual Inspection of Switchgear Enclosure No deformation or physical damage to the enclosure. Protective paint coating shows no severe rust, peeling, or flaking. Cabinet is securely installed, clean on the surface, and free of foreign objects. Nameplates and identification labels are neatly affixed and not falling off.(2) Check of Switchgear Operating Parameters Instruments and meters indicate normal values (comparable to typical operating data, with no s

Advancing Power Equipment Diagnostics: The Role of X-ray Digital ImagingWith continuous advancements in power grid equipment research and manufacturing, an increasing number of new devices are being integrated into power systems. As a result, effective monitoring of in-service equipment has become critically important for ensuring grid reliability and safety.The introduction and successful application of X-ray digital imaging technologies—specifically Computed Radiography (CR) and Digital Radiog

Reactive Power Compensation and Capacitor Switching in Power SystemsReactive power compensation is an effective means to increase system operating voltage, reduce network losses, and improve system stability.Conventional Loads in Power Systems (Impedance Types): Resistance Inductive reactance Capacitive reactanceInrush Current During Capacitor EnergizationIn power system operation, capacitors are switched in to improve power factor. At the moment of closing, a large inrush current is generated.