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

The basic meaning of a high-voltage circuit breaker is, simply put, that under normal conditions, it is used to open (interrupt, trip) and close (make, reclose) circuits, feeders, or specific loads—such as those connected to transformers or capacitor banks. When a fault occurs in the power system, protective relays activate the circuit breaker to interrupt either load current or short-circuit current, thereby ensuring the safe operation of the power system.A high-voltage circuit breaker is a typ

Based on years of field statistics on switchgear accidents, combined with analysis focusing on the circuit breaker itself, the main causes have been identified as: failure of operation mechanism; insulation faults; poor breaking and closing performance; and poor conductivity.1.Failure of Operation MechanismFailure of operation mechanism manifests as delayed operation or unintended operation. Since the most basic and important function of a high-voltage circuit breaker is to operate correctly and

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

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-