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

Very Fast Transient Over voltage(VFTO) wave common characteristics in HV& EHV GISSteep wavefront, with a rise time typically ranging from 2 to 20 nanoseconds: When restriking occurs in the contact clearance of a disconnector, the arc - reignition process is extremely rapid. As a result, the voltage waveform injected into the power grid exhibits a very high ascending or descending steepness.Theoretically, the amplitude of Very Fast Transient Overvoltage (VFTO) can reach up to 3.0 per - unit.

Ground switches feature a moving contact that creates or closes a gap between the high - voltage conductor and the enclosure. At the enclosure and the conductor, sliding contacts equipped with suitable electric - field shields are incorporated.A “maintenance” ground switch can be operated either manually or via a motor drive. It takes several seconds to open or close, and when fully closed, it can carry the rated short - circuit current for the specified time period (either 1 or 3 seconds) witho

SteelThe enclosure has two fundamental functions: maintaining internal gas pressure and ensuring gas - tightness to prevent the release of SF6 into the atmosphere. Sheet steel materials are well - suited for fulfilling these functions. In contrast, cast steel has porosity issues and cannot guarantee the high - level gas - tightness required for Gas - Insulated Switchgear (GIS).Steel is relatively easy to weld and shape. Steel enclosures are typically fabricated by mechanically forming steel shee

Requirements for Larger Tank Enclosure in VCB Vacuum breakers permit the use of insulation media other than SF6. When insulating gases such as dry air, nitrogen, or CO2 are chosen, their insulation performance will be inferior compared to that of SF6 at the same pressure. Stray capacitances to the tank negatively impact voltage division within the vacuum interrupter (VI). This may necessitate a larger, higher - rated - voltage VI.Considerations When Applying VCB in GIS Stray capacitances from th

Gas Compartment Design and OptimizationPre-filled SF6 Gas CompartmentsGas compartments are pre-filled with sulfur hexafluoride (SF6) at a pressure slightly above atmospheric pressure for transportation. This ensures that the equipment remains stable during transit and reduces the workload required for on-site installation.Optimization to Minimize SF6 UsageGas compartments are optimized to use the minimum amount of SF6 necessary for a given functionality. Since the lowest achievable SF6 recovery

Advantages of Vacuum InterruptersA vacuum interrupter is a critical component used in medium and high-voltage circuit breakers, primarily for interrupting current and preventing arc restrikes. Compared to traditional air, oil, or SF6 gas interrupters, vacuum interrupters offer several significant advantages. Below is a detailed explanation of these advantages:1. Excellent Arc Quenching Performance Rapid Arc Extinction: In a vacuum environment, there are virtually no gas molecules, so the arc ext

SF6 Gas Leakage Testing on SitePurposeSF6 gas leakage testing is conducted to ensure that there are no gas leaks at the field-assembled joints of Gas-Insulated Switchgear (GIS). Leaks can occur during field assembly due to various factors such as damaged sealing surfaces, improper placement, incorrect application of seals, seal damage or omission, improper application of lubricants and sealants, misalignment or inadequate tightening of mating surfaces, and contamination.Scope Exclusions: There i

The use of gas-insulated metal-enclosed switchgear (GIS) faces the following challenges and limitations:I. In terms of technical complexityHigh requirements for installation and commissioning Challenge: GIS equipment has a complex structure, and the installation and commissioning process requires a high degree of professional technology and precise operation. The installation environment has strict requirements, such as the need for a clean and dry site to ensure the insulation performance insid

The sequence of operations in disconnecting Gas Insulated Switchgear (GIS) is critical to ensure safety and prevent damage to the equipment. Generally, the correct order when disconnecting the power supply in a GIS involves first opening the circuit breaker and then operating the disconnector (also known as an isolator). Here is a detailed explanation:Correct Operational Sequence Open the Circuit Breaker The circuit breaker is the primary device used to interrupt the load current. Before disco

GIS device definitionGIS is the abbreviation of Gas Insulated Switchgear, which is generally translated as a gas insulated fully enclosed combination appliance, usually using SF6 gas as the insulating medium. Includes circuit breaker (CB), isolation switch (DS), ground switch (ES, FES), BUS (BUS), current transformer (CT), voltage transformer (VT), lightning arrester (LA) and other high voltage components. At present, GIS equipment products have covered the voltage range of 72.5 kV ~1200 kV.Char