Summary
High voltage gas-insulated switchgear (GIS) using SF6 alternative gas insulation technologies has been developed to meet the global demand for reducing environmental impact. Dry air is an ideal candidate because its GWP equals zero, and its insulation technology has been widely utilized at low and medium voltages around the world. The authors have developed highvoltage rated equipment using dry air (80% N2 and 20% O2) [1] and, with a view toward expanding their applicability to DC equipment, have also advanced the development of a residual-current interrupter (RCS) for DC circuit breaker.
Read more Read lessThis paper reports the results of an investigation into insulation characteristics under DC voltage and the development and experimental validation of a prototype 550 kV DC RCS. The results indicate that, under high-pressure gas conditions, the DC breakdown voltage tended to be lower than lightning impulse (LI) BDV. The DC/LI BDV ratio was found to be larger than the DCWV/LIWV ratio specified in the IEC standards, indicating that the insulation design of the RCS could be based on LI BDV. Furthermore, investigation of the behaviors of contaminated metallic particles inside the tank revealed the occurrence of firefly (FF) phenomena. The partial discharges (PD) associated with FF were shown to be detectable using
UHF sensors.
Based on these findings, a prototype 550 kV DC RCS was designed, manufactured, and verified using withstand tests. The superimposed-voltage tests with 550 kV DC and 1425 kV LIWV were carried out and all withstand tests were conducted in accordance with IEC TS 62271-5 and IEC TS 62271-313 [2, 3]. As for metallic particle contamination tests, the particles were lifted after RCS switching and exhibited FF with a very low probability, on the order of 0.01% per an operation. After FF motion, they fell within five minutes and became trapped to the tank side. The results of the analysis of the RCS interruption duty were presented, and the interruption test results that take the duty into account are also reported. Finally, the decomposition gas produced by residual-current interruption was investigated. Although small amounts of NO and NO2 were detected, health risk evaluation in accordance with IEC 622714 [4] annex indicated that there was no notable risk.
The success of the tests provides a prospect for realizing 550 kV dry air-insulated equipment.
These findings are expected to contribute to the commercialization of dry air insulation equipment in line with the roadmap for carbon neutral.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | A3_10766_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | Japan |
| Study committees | |
| File size | 3 MB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
MIYASHITA Makoto - Mitsubishi Electric Corporation Japan; SASAKI Shimpei - Mitsubishi Electric Corporation Japan; ASHIKAGA Taiki - Mitsubishi Electric Corporation Japan; SAKATA Yuma - Mitsubishi Electric Corporation Japan; MATSUYAMA Kotaro - Mitsubishi Electric Corporation Japan; INAGAKI Takashi - Mitsubishi Electric Corporation Japan
Keywords
Dry Air, Residual Current, Switch, Insulation, Firefly, Partial Discharge, Superimposed Impulse Voltage, Test
