An HV bushing in a transformer is a high-voltage insulating device that allows a current-carrying conductor to safely pass through the grounded transformer tank or enclosure while maintaining reliable electrical insulation and mechanical support.
1. Electrical Insulation: Separates the high-voltage conductor from the grounded transformer tank.
2. Mechanical Support: Provides strong support for the conductor and withstands mechanical stresses.
3. Sealed Path: Prevents oil, moisture, and contaminants from entering or leaking.
4. Connection Point: Serves as the safe terminal where transformer windings connect to overhead lines, busbars, or switchgear.
1. OIP (Oil Impregnated Paper) Bushing: Traditional type, suitable for high voltages up to 800 kV.
2. RIP (Resin Impregnated Paper) Bushing: Dry-type design, environmentally friendly, low maintenance.
3. RIS (Resin Impregnated Synthetic) Bushing: Uses synthetic material for better moisture and partial discharge resistance.
4. Composite / Epoxy Wall-through Bushing: Often used in dry-type or medium-voltage transformers, made of epoxy resin and fiberglass.
1. Voltage rating (e.g., 72.5 kV, 145 kV, 400 kV)
2. Current rating (up to several thousand amperes)
3. Creepage distance (important for outdoor and polluted environments)
4. Insulation type (OIP, RIP, RIS, Epoxy)
5. Mounting type (outdoor, wall-through, transformer tank bushing)
1. Power transformers at generation and substations
2. Distribution transformers in medium-voltage networks
3. High-voltage switchgear and GIS (as wall bushings)
HV bushing in a transformer is a critical insulated terminal that allows high-voltage current to pass safely from the transformer to the external grid while providing electrical insulation, mechanical support, and environmental protection. It is an essential component for reliable and safe power system operation.