Although SF6 gas inside GIS has excellent insulating properties, it is highly sensitive to residual metal particles. Applying the series resonant system to the on-site withstand voltage test of GIS (Gas Insulated Metal Enclosed Switchgear) is the most commonly used method in high-voltage testing. GIS is fully enclosed. Where is the best place to inject the test voltage? There are three common entry points, each with pros and cons:
1. Outdoor Bushings: The most standard method. We connect the resonant reactors directly to the outdoor SF6-to-Air bushings.
2. Cable Terminals: If the GIS is connected to underground cables, we can inject power through the cable end. However, the cable's own insulation and length will add to the total capacitance, requiring more reactors.
3. Dedicated Test Interfaces: High-end GIS often includes a small, specialized SF6-filled test port. This is the "cleanest" method as it doesn't require dismantling parts of the main busbar.
