Corona Control Rings

corona control rings

Corona Control Rings

Corona Control Rings are deployed in EHV/ UHV level for dual purpose of reducing electrical stresses to ensure
extinction of corona below a certain voltage level thereby reducing losses due to corona as well as taking care of voltage grading along insulator string. The design of CC ring also ensures Radio Interference Voltage (RIV) under the acceptable limit. Surface Voltage Gradient on surface of conductor are calculated for Transmission Lines and Sub-stations and are kept within safe limit with respect to corona inception.

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Design of CC Ring for 1200kV Transmission Line and Sub-Station Hardware  - A technical Landmark Achieved by SUPREME

Corona Control (CC) Rings are deployed in EHV/ UHV level for dual purpose of reducing electrical stresses to ensure extinction of corona below a certain voltage level thereby reducing losses due to corona as well as taking care of voltage grading along insulator string. The design of CC ring also ensures Radio Interference Voltage (RIV) under the acceptable limit. Surface Voltage Gradient on surface of conductor are calculated for Transmission Lines and Sub-stations and are kept within safe limit with respect to corona inception. 1200kV system need special attention on the design aspect of CC Rings in view of the large dimension of the CC Ring to cover a large Hardware Fitting set. Surface Voltage Gradient on surface of conductor was calculated for Transmission Lines and Sub-stations and found within safe limit with respect to corona inception. Selection of CC ring has been done by covering a much larger diameter and effective surface area and hence performance with respect to Corona Inception and Losses will be within limit. To achieve this, 100mm diameter 6063 Grade Aluminum Alloy extruded tube with 5mm thickness was selected. Bending of such tubes called for new and higher capacity bending machines along with new dies which were developed in-house. CC ring for Tension Hardware is of such large dimension, it was fabricated(bend) in two halves. Two Couplings having inner diameter close to the tube's outer diameter have been deployed at the two adjoining points of the two halves of CC ring. To facilitate smooth fitment, the couplings are tapered inside from the centre to the outermost point on either side. Opening up of CC ring has been arrested by two structural steel flats bolted with the bracket of CC ring and fastening both the halves of CC ring together.  Studies were conducted by M/s Decan Enterprises to determine voltage distribution along insulator string. Polymer Insulator with Octagonal bundle conductor were considered with two types of outer Corona Control/ Grading rings viz., 700mm and 1100mm ring diameters. Comparative Results of the following:

corona rings