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

Single-Phase ReclosingAdvantage:When a single-phase-to-ground fault occurs on a line and three-phase auto-reclosing is applied, it results in higher switching overvoltages compared to single-phase reclosing. This is because three-phase tripping interrupts the current at zero-crossing, leaving residual charge voltages on the unfaulted phases—approximately equal to the peak phase voltage. Since the de-energized interval during reclosing is relatively short, the voltage on these unfaulted phases do

The rural power grid transformation plays an important role in reducing rural electricity tariffs and accelerating rural economic development. Recently, the author participated in the design of several small-scale rural power grid transformation projects or conventional substations. In rural power grid substations, conventional 10kV systems mostly adopt 10kV outdoor auto circuit vacuum reclosers.To save investment, we adopted a scheme in the transformation that removes the control unit of the 10

An Automatic Circuit Recloser is a high-voltage switching device with built-in control (it inherently possesses fault current detection, operation sequence control, and execution functions without requiring additional relay protection or operating devices) and protective capabilities. It can automatically detect the current and voltage in its circuit, automatically interrupt fault currents according to inverse-time protection characteristics during faults, and perform multiple reclosures accordi

Lightning strikes, fallen tree branches, and even Mylar balloons are enough to interrupt current flow on power lines. That’s why utility companies prevent outages by equipping their overhead distribution systems with reliable recloser controllers.In any smart grid environment, recloser controllers play a critical role in detecting and interrupting transient faults. Although many short circuits on overhead lines can resolve themselves, reclosers help improve service continuity by automatically re

On August 10, a self-developed 750 kV single-column, high-capacity autotransformer manufactured by China Transformer Manufacturing Company successfully passed the national-level technical appraisal for new products. Experts at the appraisal meeting unanimously concluded that the product’s key technical specifications have reached an internationally leading level among similar products, marking a significant advancement for China in the design and manufacturing of extra-high-voltage (EHV) transfo

According to statistics, the vast majority of faults on overhead power lines are transient, with permanent faults accounting for less than 10%. Currently, medium-voltage (MV) distribution networks commonly employ 15 kV outdoor vacuum automatic circuit reclosers in coordination with sectionalizers. This setup enables rapid restoration of power supply after transient faults and isolates faulty line segments in the event of permanent faults. Therefore, it is essential to monitor the operational sta

1 Current Grid StatusWith the continuous deepening of rural power grid transformation, the health level of rural grid equipment is constantly improving, and power supply reliability basically meets user needs. However, regarding the current grid status, due to funding constraints, ring networks have not been implemented, dual power supplies are unavailable, and lines adopt a single radial tree-like power supply method. This resembles a tree trunk with many branches—meaning the lines have numerou

With the improvement of social productivity and people's quality of life, the demand for electricity is continuously increasing. To ensure the effectiveness of power grid system configuration, it is necessary to reasonably construct distribution networks based on actual conditions. However, during the operation of distribution network systems, 17.5kV ring main units play a very important role, so the impact caused by failures is extremely significant. At this point, it is essential to adopt reas

DTU (Distribution Terminal Unit), a substation terminal in distribution automation systems, is secondary equipment installed in switching stations, distribution rooms, N2 Insulation ring main units (RMUs), and box-type substations. It bridges primary equipment and the distribution automation master station. Older N2 Insulation RMUs without DTUs cannot communicate with the master station, failing to meet automation requirements. While replacing entire RMUs with new DTU-integrated models would sol

1. Specific Design1.1 Design ConceptState Grid Corporation of China actively promotes grid energy conservation and low-carbon development to achieve national carbon peak (2030) and neutrality (2060) goals. Environmentally friendly gas-insulated ring main units represent this trend. A new 12kV integrated environmentally friendly gas-insulated ring main unit was designed combining vacuum interrupter technology with three-position disconnectors and vacuum circuit breakers. The design utilized Solid