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

1. Introduction Transmission line faults can be classified into two types based on their nature: transient faults and permanent faults. Statistical data shows that most transmission line faults are transient (caused by lightning strikes, bird-related incidents, etc.), accounting for approximately 90% of all faults. Therefore, after a line is disconnected due to a fault, attempting reclosure once can significantly improve power supply reliability. The function of automatically reclosing a circuit

Reclosing can be categorized into single-phase reclosing, three-phase reclosing, and comprehensive reclosing.Single-phase reclosing: After a single-phase fault occurs on the line, single-phase reclosing is performed. If reclosing occurs onto a permanent fault, all three phases are tripped and no further reclosing attempts are made. For interphase faults, all three phases are tripped without reclosing.Three-phase reclosing: Regardless of fault type, all three phases are tripped followed by three-

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

On December 2nd, the South Cairo distribution network loss reduction pilot project in Egypt, led and implemented by a Chinese power grid company, officially passed the acceptance inspection by the South Cairo Electricity Distribution Company of Egypt. The comprehensive line loss rate in the pilot area decreased from 17.6% to 6%, achieving an average daily reduction of lost electricity of approximately 15,000 kilowatt-hours. This project is the first overseas distribution network loss reduction p

A "2-in 4-out 10 kVsolid-insulated ring main unit" refers to a specific type of ring main unit (RMU). The term "2-in 4-out" indicates that this RMU has two incoming feeders and four outgoing feeders.10 kVsolid-insulated ring main unit are equipment used in medium-voltage power distribution systems, primarily installed in substations, distribution stations, and transformer stations to distribute high-voltage power to low-voltage distribution networks. They generally consist of high-voltage incomi

Low-voltage distribution lines refer to the circuits that, through a distribution transformer, step down the high voltage of 10 kV to the 380/220 V level—i.e., the low-voltage lines running from the substation to the end-use equipment.Low-voltage distribution lines should be considered during the design phase of substation wiring configurations. In factories, for workshops with relatively high power demand, dedicated workshop substations are often installed, where transformers supply power direc

1. What Is a Three-Phase Power Surge Protective Device (SPD)?A three-phase power surge protective device (SPD), also known as a three-phase lightning arrester, is specifically designed for three-phase AC power systems. Its primary function is to limit transient overvoltages caused by lightning strikes or switching operations in the power grid, thereby protecting downstream electrical equipment from damage. The SPD operates based on energy absorption and dissipation: when an overvoltage event occ

The Daquan Line has a large power load, with numerous and scattered load points along the section. Each load point has a small capacity, with an average of one load point every 2-3 km, so two 10 kV power through lines should be adopted for power supply. High-speed railways use two lines for power supply: primary through line and comprehensive through line. The power sources of the two through lines are taken from the dedicated bus sections fed by the voltage regulators installed in each power di

In power grid construction, we should focus on actual conditions and establish a grid layout suitable for our own needs. We need to minimize power loss in the grid, save social resource investment, and comprehensively improve China's economic benefits. Relevant power supply and electricity departments should also set work goals centered on effectively reducing power loss, respond to energy conservation calls, and build green social and economic benefits for China.1.Current Status of China's Powe

Railway power systems primarily consist of automatic block signaling lines, through-feeder power lines, railway substations and distribution stations, and incoming power supply lines. They provide electricity to critical railway operations—including signaling, communications, rolling stock systems, station passenger handling, and maintenance facilities. As an integral part of the national power grid, railway power systems exhibit distinct characteristics of both electrical power engineering and