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

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

Leakage in Hydraulic Operating MechanismsFor hydraulic mechanisms, leakage can cause short-term frequent pump starting or excessively long re-pressurization time. Severe internal oil seepage in valves may lead to pressure loss failure. If hydraulic oil enters the nitrogen side of the accumulator cylinder, it can cause abnormal pressure rise, which affects the safe operation of SF6 circuit breakers.Apart from failures caused by damaged or abnormal pressure detection devices and pressure component

1. BackgroundSF6 electrical equipment has been widely applied in power utilities and industrial enterprises, significantly advancing the development of the power industry. Ensuring the reliable and safe operation of SF6 equipment has become a critical task for power departments.The arc-quenching and insulating medium in SF6 equipment is SF6 gas, which must remain sealed—any leakage compromises the reliability and safety of the equipment. Therefore, monitoring the SF6 gas density is essential.Cur

This article categorizes faults into two main types: SF₆ gas circuit faults and circuit breaker failure-to-operate faults. Each is described below:1.SF₆ Gas Circuit Faults1.1 Fault Type: Low gas pressure, but density relay does not trigger alarm or lockout signalCause: Faulty density gauge (i.e., contact not closing)Inspection & Handling: Calibrate actual pressure using a standard gauge. If confirmed, replace the density gauge.1.2 Density Relay Triggers Alarm or Lockout Signal (but pressure

I. Fault Management(1) Basic Principles of Fault Handling Rapidly restrict the development of the fault, eliminate the root cause, and remove threats to personnel, power grid, and equipment safety. Adjust and restore normal power grid operation modes. If the grid has split, quickly restore synchronization. Maintain operation of healthy equipment and ensure continuous power supply to critical users, plant service loads, and substation auxiliary power. Restore power supply to de-energized users an

Our 220 kV substation is located far from the urban center in a remote area, surrounded primarily by industrial zones such as Lanshan, Hebin, and Tasha Industrial Parks. Major high-load consumers in these zones—including silicon carbide, ferroalloy, and calcium carbide plants—account for approximately 83.87% of our bureau’s total load. The substation operates at voltage levels of 220 kV, 110 kV, and 35 kV.The 35 kV low-voltage side mainly supplies feeders to ferroalloy and silicon carbide plants

1.Application Issues and Handling Measures for 10kV Ring Main Units (RMUs)The 10kV ring main unit (RMU) is a core power distribution device in urban 10kV distribution networks, widely used in industrial parks, residential communities, commercial centers, and public facilities for medium-voltage power supply and flexible power distribution. Its primary function is to enable flexible energy distribution, ring-fed operation, and fault isolation at the 10kV voltage level. However, during long-term o

High-Voltage Circuit Breakers: Classification and Fault DiagnosisHigh-voltage circuit breakers are critical protective devices in power systems. They rapidly interrupt current when a fault occurs, preventing damage to equipment from overloads or short circuits. However, due to long-term operation and other factors, circuit breakers may develop faults that require timely diagnosis and troubleshooting.I. Classification of High-Voltage Circuit Breakers1. By Installation Location: Indoor-type: Insta

10 Prohibitions for Transformer Installation and Operation! Never install the transformer too far away—avoid placing it in remote mountains or wilderness. Excessive distance not only wastes cables and increases line losses, but also makes management and maintenance difficult. Never choose transformer capacity arbitrarily. Selecting the right capacity is essential. If the capacity is too small, the transformer may be overloaded and easily damaged—overloading beyond 30% should not exceed two hours