As India marches towards the 21st century, power becomes an essential ingredient for infrastructural development. With rapid urbanisation around the corner to sustain the industrial growth, the necessity of transmitting large blocks of power to load centres assumes significance. Over the years, there has been a marked increase in the voltage level for transmission of bulk power, due to the distinct advantages offered by the use of high voltage. This had ushered in the generation of Extra high voltage (EHV) power transmission systems with voltage grades of 66 kV and above. In this context, long-distance underground cable networks provide an ideal solution in many situations where the safety and logistic considerations preclude the use of cross-country overhead tower lines.

Underground EHV cables are also used for evacuating bulk power generated in pumped storage hydroelectric power generating stations, situated at a lower altitude, at outdoor switchyard located at a higher altitude. Similarly, underground cable systems are the appropriate means of power transmission over short distances where erection of overhead tower lines would be infeasible considering the space constraints.

The distinct advantages in achieving low transmission losses when such cable systems are operated at higher voltages for bulk power transfer are well-known.

It is in this context that Cross-linked Polyethylene (XLPE) insulated cables offer significant advantages. As an insulating material, XLPE combines the advantages of improved mechanical and thermal properties with excellent electrical characteristics of high dielectric strength, low relative permittivity and low loss factor. These advantages have rendered what XLPE cables can achieve today - carrying large currents at voltages upto 220 kV and above, with an inherent higher short circuit withstand capacity of 250oC. Additional benefits that accrue are simple construction, easy installation and trouble free operation.

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