Insulation for electrical cablessss.pptx

Cable

1. Insulation of Electrical Cables

2. Purpose Insulation is provided to isolate one conductor from other conductors to prevent short circuits and isolate from the environment for safety

3. Type of Polymers Thermoplastic Compound : These material soften when they are heated and solidify when they are cooled. They can be reheated to reshape, hence they can be recycled. Ex. PVC, PE Thermoset Compound : Thermosets undergo a crosslinking reaction when the temperature is raised above a certain temperature. This crosslinking bonds the polymer molecules together to form a three-dimensional network. This network remains intact when the temperature is reduced again. Crosslinking causes an irreversible change in the material, hence cannot be recycled. Ex. XLPE

4. Insulation Material PVC (Polyvinyl Chloride) Type A, General Purpose (Max. Operating Temp 70 DegC , Condt Class 1&2) (Voltage upto 3.3/3.3 KV Type B, General Purpose (Max. Operating Temp 70 DegC , Voltage above 3.3/3.3 KV) Type C, HR (Max. Operating Temp 85 Deg C, Condt Class 1, 2 & 5) Type D, Flexible (Max. Operating Temp 70 Deg C, Condt Class 5) PE (Polyethylene) (Max. Operating Temp 70 DegC ) XLPE (Max. Operating Temp 90 Deg C) TR XLPE (Tree Retardant)

5. Insulation Material Rubber Type IE1, General Purpose (Max. Operating Temp 60 DegC ) Type IE2, EPR, HR (Max. Operating Temp 90 Deg C, Upto 1.1 KV) Type IE3, EPR, HR (Max. Operating Temp 90 Deg C, Above 3.3 KV) Type IE4, CSP, Oil Resistant & Flame Retardant (Max. Operating Temp 90 Deg C) Type IE5, Silicon Rubber (Max. Operating Temp 150 Deg C) LSZH (HFFR) Type HFI-TP 70, Thrmoplastic (Max. Operating Temp 70 DegC ) Type HFI-XL 90, Thrmosetting (Max. Operating Temp 90 DegC )

6. Curing Steam Cure ( Sioplas ) Dry Cure/Gas Cure/Nitrogen Gas Cure (CCV) Catenary Continuous Vulcanization Electron Beam Cure (E-Beam)

7. CCV Catenary - Catenary is the curve that is an idealized hanging chain or cable assumes under its own weight when supported only at its ends in a uniform gravitational field. CCV – The curing operation is carried out in line and continuous in a catenary tube. In the CCV process, the pre-compounded polyethylene, containing an antioxidant and peroxide, is extruded on to a conductor. The insulated conductor immediately enters a heated vulcanization zone, located within a tube which is in the form of a catenary. The now-cured material is cooled in water, or an inert gas. If at elevated temperature it touches the wall of the tube, deformation will occur - hence the need for a tube in the shape of a catenary. The heat required to raise the temperature of the insulation in the curing zone of the tube can be obtained from steam, high temperature nitrogen, radiant heaters fixed on the outside of the tube. In order to keep the voids which are formed within the insulation by these gases down to an acceptable size, the tube is pressurized.

8. TREEING : The insulation weakness as the gasses trapped in voids ionizes. These voids formed within the insulation by compound migration resulting from cable loading and steep inclines. The breakdown of insulation due to ionization occurs through the formation of carbonaceous 'fronds' on the insulation. This is generally known as 'treeing’. This start at the conductor surface, and gradually spread outwards through the insulation, increasing in width and complexity as progression takes place. WATER TREEING : The water contained in a void vaporizes or expands, thus increasing the pressure in the void and so generating fine cracks. The formation of oxygen during this process may accelerate the oxidation of the polyethylene, which would account for the final electrical breakdown.

9. Standard IS 5831 (PVC) IS 7098 (XLPE) IS 6380 (Rubber) IS 17048 (LSZH)

10. Density PVC - 1.4 gm/cm 3 PE/XLPE - 0.93 gm/cm 3