Hollow porcelain insulators are basically used as weather shields that protect the internal components from being exposed to the vagaries of 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

These insulators being of hollow construction are subjected to an internal hoop (pressure) stress in addition to the mechanical bending stress. This necessitates expertise in the design, manufacture & testing of these insulators.

The hollow porcelain insulators are manufactured using high strength Aluminous porcelain and subjected to strict process and dimensional controls. The drying and firing process are suited to ensure proper and complete vitrification of the shells. The shells are then cut & ground to the specific requirements. The chamfer of the internal and external diameter plays a critical role in the mechanical performance of the hollow porcelain insulators and hence particular care is taken to ensure proper chamfering of the ends. The surface finish is another such critical factor that prevents gas / oil leakage and hence is critically controlled.

All the shells are subjected to ultrasonic test prior to assembly. The insulators are then assembled with the metal parts as required using Portland cement with the aid of precision assembly fixtures. The cement is cured under conditions of temperature and humidity.

They are then subjected to routine and conformance tests in line with customer requirements, IS or IEC standards as required.

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Hollow Insulators Specification
Voltage Rating from 33kV up to 800 kV
Mechanical rating from 02KN to 50KN
Height Up to 2800mm in single part and up to 4500mm with Epoxy joints
ID Min 65mm to Max 450mm
OD Min 125mm to Max 600mm
Specific Creepage Distance from 12mm/kV to 35mm/kV
Applicable Standards IS, IEC

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