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

Dry-type transformers refer to power transformers in which the core and windings are not immersed in oil. Instead, the coils and core are cast together (typically with epoxy resin) and cooled by either natural air convection or forced-air cooling. As a relatively newer type of power distribution equipment, dry-type transformers have been widely used in power transmission and distribution systems in factory workshops, high-rise buildings, commercial centers, airports, ports, subways, and offshore

1. Fundamentals of Transformer Testing1.1 OverviewTransformers are among the most critical pieces of equipment for electric power transmission. Their quality and reliability directly affect the safe and dependable delivery of electricity. Damage to generator transformersor key substation transformers can disrupt power transmission, and repairing or transporting such large units often takes several months.During this downtime, power supply is compromised, adversely impacting industrial and agricu

Recently, Chinese GIS manufacturers announced exciting news: the first ZF11C-252(L) mixed-gas double-break GIS product developed by a Chinese GIS manufacturer successfully passed its on-site power frequency withstand voltage test on the first attempt at a project site. This achievement marks another milestone for Chinese GIS manufacturers in advancing green and high-quality development of power grids.The ZF11C-252(L) mixed-gas double-break GIS that passed the test represents the culmination of t

GIS (Gas-Insulated Switchgear) offers advantages such as compact structure, flexible operation, reliable interlocking, long service life, maintenance-free operation, and small footprint. It also possesses many irreplaceable advantages in insulation performance, environmental friendliness, and energy saving, and is increasingly applied in industrial and mining enterprises, airports, railways, subways, wind power stations, and other fields.A certain enterprise’s 35 kV indoor substation was origina

Can dual-ended grounding be measured?Dual-ended grounding can be measured, but traditional high-voltage circuit breaker motion characteristic testers cannot perform such measurements. The conditions for dual-ended grounding are relatively complex; measurement accuracy must be ensured while simultaneously dealing with numerous electromagnetic interferences such as impedance and high-frequency currents. Therefore, a high-voltage circuit breaker tester specifically designed for dual-ended grounding

1. Overview Ultra-high-voltage (UHV) transformers are core equipment in modern power systems. Understanding their voltage ratings, complex structure, precision manufacturing processes, and critical production techniques reveals why they represent the pinnacle of a nation’s power equipment manufacturing capability. Voltage Level DefinitionThe term "ultra-high-voltage transformer" typically refers to transformers used in AC transmission lines rated at 1,000 kV or higher, or DC transmission lines r

1 IntroductionAccording to the provisions of the national standard GB/T 1094.3-2017, the primary purpose of the line terminal AC withstand voltage test (LTAC) for power transformers is to evaluate the AC dielectric strength from the high-voltage winding terminals to ground. It does not serve to assess inter-turn insulation or phase-to-phase insulation.Compared with other insulation tests (such as full lightning impulse LI or switching impulse SI), the LTAC test imposes a relatively more stringen

1. Methods for Detecting Busbar Discharge1.1 Insulation Resistance TestThe insulation resistance test is a simple and commonly used method in electrical insulation testing. It is highly sensitive to through-type insulation defects, overall moisture absorption, and surface contamination—conditions that typically result in significantly reduced resistance values. However, it is less effective in detecting localized aging or partial discharge faults.Depending on the equipment’s insulation class and

I. IntroductionThe Guanting–Lanzhou East 750kV transmission and substation demonstration project in China was officially put into operation on September 26, 2005. This project includes two substations—Lanzhou East and Guanting (each equipped with four 750kV transformers, three of which form a three-phase transformer bank in operation, with one on standby)—and one transmission line. The 750kV transformers used in the project were independently developed and manufactured in China. During the on-si

Purpose of Grounding System Functional Grounding (Working Grounding):In power systems, grounding is required for normal operation, such as neutral point grounding. This type of grounding is known as working grounding. Protective Grounding:The metal enclosures of electrical equipment may become energized due to insulation failure. To prevent electric shock hazards to personnel, grounding is provided and is referred to as protective grounding. Overvoltage Protection Grounding:Grounding is installe