Hollow insulator are generally used as weather protection to protect the internal components from the weather. They are used in
- Current transformers
- Voltage transformers
- Capacitive voltage transformers
- Circuit breakers – SF6 & Non-SF6
- Surge (Lightning) arresters.
- Power transformer bushings
- Wall through bushings
Hollow Insulator, which are of hollow construction, are exposed to an inner circumferential stress (compressive stress) in addition to the mechanical bending stress. This requires expertise in the design, manufacture and testing of these isolators.
The Hollow Insulator is subjected to strict process and dimensional controls. The drying and firing process is suitable to ensure proper and complete glazing of the shells. The bowls are then cut and ground to the specific requirements. The chamfer of the inner and outer diameter plays a crucial role in the mechanical performance of the hollow porcelain insulators, and special care is therefore taken to ensure that the ends are properly chamfered. The surface quality is another critical factor that prevents gas / oil from escaping and is therefore critically controlled.
All shells are subjected to an ultrasound test before assembly. The Hollow Insulator is then assembled with the metal parts.
They are then subjected to routine and conformance tests according to customer requirements, IS or IEC standards as required.