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

1. Product OverviewA Ring Main Unit (RMU) is an electrical apparatus composed of high-voltage switching equipment enclosed in a metal or non-metal insulated cabinet, or configured as modular compartments forming a ring-type power supply unit. Its core components typically include load switches and fuses, offering advantages such as simple structure, compact size, low cost, improved power parameters and performance, and enhanced power supply safety.RMUs are widely used in distribution substations

I. IntroductionThe cabinet structure forms the fundamental basis of low-voltage switchgear, making cabinet manufacturing technology the foundation of all foundations. As a structural enclosure, the cabinet must not only meet the functional integration requirements of various electrical units (such as standardized types, modular combinations, and functional distribution), but also satisfy inherent cabinet requirements (such as robustness, reliability, neat appearance, and ease of adjustment). Due

High-voltage switchgear is a critical electrical device in power systems. Deterioration in switchgear operating conditions is one of the main causes of power system failures. So, what are the common faults in high-voltage switchgear?I.Classification of High-Voltage Switchgear(1) Outdoor and Indoor TypesBased on installation location, high-voltage switchgear can be classified as outdoor or indoor types. Indoor switchgear is commonly used for systems at 10 kV and below. According to primary circui

Long-distance protection of high-voltage transmission lines primarily relies on technologies such as differential protection, distance protection, and automatic reclosing. Together, these technologies effectively ensure safe power transmission and stable grid operation.In the vast power transmission network, high-voltage transmission lines play a crucial role, acting as energy arteries that deliver electricity from power plants to homes and businesses. However, as transmission lines extend over

Function of Surge ArrestersWhen lightning-induced overvoltage travels along overhead power lines into a substation or other buildings, it can cause flashovers or even puncture the insulation of electrical equipment. Therefore, if a protective device—known as a surge arrester—is connected in parallel at the power inlet of the equipment (as shown in Figure 1), it will immediately activate when the overvoltage reaches the preset operating level.The arrester discharges the excess energy, limiting th

I. Common Fault Types and Diagnostic MethodsElectrical Faults Circuit Breaker Failure to Operate or Maloperation: Check the energy storage mechanism, closing/tripping coils, auxiliary switches, and secondary circuits. High-Voltage Fuse Blown: Measure voltage across the fuse terminals; inspect busbar joints, cable terminations, and protection relay settings. Busbar Discharge or Insulator Damage: Listen for discharge sounds, check temperature at busbar connections, and visually inspect insulators

Types and Common Fault Analysis of High-Voltage SwitchgearHigh-voltage switchgear is a critical electrical device in power systems. Deterioration in switchgear operation is one of the main causes of power system failures. What are the common faults in high-voltage switchgear?(1) Outdoor and Indoor TypesBased on installation environment, high-voltage switchgear can be classified as outdoor or indoor types. Equipment rated at 10 kV and below is mostly installed indoors. According to primary circui

Oil-Immersed Transformers: Overview, Features, and ApplicationsAn oil-immersed transformer is a widely used type of power transformer that employs a liquid—typically insulating oil—as both an insulating and cooling medium.Key Features of Oil-Immersed Transformers: Insulating Oil: Insulating oil serves as the primary dielectric medium, electrically isolating the windings from the core and ground. With its high dielectric strength, it effectively prevents electrical breakdown between windings or b

The absorption ratio is defined as follows: When operating a megohmmeter (insulation resistance tester), rotate the handle at a speed of 120 revolutions per minute. Record the insulation resistance reading at 15 seconds (R15) and then at 60 seconds (R60). The absorption ratio is calculated using the formula:Absorption Ratio = R60 / R15, which should be greater than or equal to 1.3.Measuring the absorption ratio helps determine whether the insulation of electrical equipment is damp. When insulati

I. Operational Analysis1.1 Operating ScopeHigh-voltage disconnect switches are classified into outdoor and indoor types based on installation location, and into three-pole or single-pole configurations according to the number of poles. During operation, attention must be closely paid to the switch’s operating current and voltage.If the operating voltage exceeds the rated value, discharge may occur within the porcelain insulator. The degree of heating is closely related to the operating current a