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

1 Insulation Materials and DesignBased on cost statistics for medium-voltage solid-insulated ring main units (RMUs), the insulation structure accounts for over 40% of the total cost. Therefore, selecting appropriate insulation materials, designing rational insulation structures, and determining the correct insulation method are crucial to the value of medium-voltage RMUs. Since the first synthesis of epoxy resin in 1930, various additives have been continuously explored to improve its properties

Development Status at Home and AbroadToshiba Corporation of Japan developed high-performance epoxy resin materials and casting technology in 1999, and subsequently launched a 24 kV solid-insulated ring main unit (RMU) in 2002. The product line has since been expanded, and the company is now advancing toward higher voltage levels of 72 kV and 84 kV. Holec, originally a European pioneer with advanced design concepts and environmentally friendly manufacturing processes that produce no pollution, wa

1.Current Application Status of Solid-Insulated Ring Main Units in Medium-Voltage Distribution Networks1.1 Widespread Application in Urban Residential AreasThe core components of medium-voltage ring main units (RMUs) primarily consist of load switches and fuses. These units offer several advantages, including a simple structure, compact size, and relatively low cost. Additionally, they effectively improve power quality and enhance the reliability and safety of power supply. Observations indicate

Current Application Status of Solid-Insulated Ring Main Units in Medium-Voltage Distribution Networks(1) Solid-insulated ring main units (RMUs) have been widely applied in urban residential areas and other medium-voltage distribution applications. The core components of medium-voltage RMUs mainly include the load switch and the fuse. These units offer advantages such as a simple structure, compact size, and low cost, while effectively improving power supply parameters and enhancing operational s

Power transformers can be classified into several categories based on their purpose, structure, and other characteristics: According to purpose: Step-up transformer:Increases voltage from low to high levels, enabling efficient long-distance power transmission. Step-down transformer:Decreases voltage from high to low levels, supplying power to local or nearby loads through distribution networks. According to phase number: Single-phase transformer Three-phase transformer According to windi

What is a Ground Fault and an Earth Fault?Ground Fault:A ground fault occurs when an unintended connection (fault) develops between a live conductor and the ground or neutral point. In such a fault, the current flows directly to the ground. This can happen in various forms, such as a single line-to-ground fault (L-G), double line-to-ground fault (LL-G), or three line-to-ground fault (LLL-G).Ground faults are particularly severe because they can result in a large magnitude of fault current. If no

1. Characteristics of Fully Insulated SF₆ Switchgear1.1 OverviewFully insulated SF₆ switchgear comprises functional units such as load switches, load switch-fuse combinations, disconnectors-circuit breakers, etc., all sealed within stainless steel gas boxes filled with low-pressure SF₆ gas. This gas serves both as the arc-quenching and insulating medium. The switchgear employs electric or manual spring-operated mechanisms. Each cabinet is an independent gas box, allowing for expansion through bu

1 Ring Network Power Supply and Ring Main UnitsWith the advancement of urbanization, the demand for higher reliability in power distribution continues to grow, and an increasing number of users require two or more power supply sources. The traditional "radial power supply" method faces challenges such as difficulties in cable installation, complicated fault detection, and inflexibility in grid upgrades and expansions. In contrast, "ring network power supply" enables dual or multiple power source

Transformer Main Body Construction and Safety Protection DevicesA power transformer is equipped with several critical safety protection devices to ensure reliable and safe operation. These components play essential roles in monitoring, protecting, and maintaining the integrity of the transformer under varying operating conditions.1. Oil Cushion (Conservator Tank)The oil cushion, also known as the conservator tank, typically has a capacity of approximately 8–10% of the total transformer

1 Live Testing AnalysisDetection of Issues through Live TestingIn October of a certain year, during live partial discharge (PD) testing on 10kV ring main units (RMUs) under our jurisdiction, the maintenance and testing team observed significantly elevated signal amplitudes in several units (Transient Earth Voltage (TEV) readings around 18 dB, and ultrasonic readings around 20 dB). Most of these units were from the same manufacturer. Consequently, a unified test was conducted on 15 RMUs from this