Thermal instability on TR-XLPE 12/20 kV ground cable : Non adiabatic and adiabatic comparison method

Short circuit current constitutes one of the forms of disturbance on transmission system of electric energy, including transmission system through underground cable. Effects of short circuit current disturbance are, among other things: mechanical damage on cable due to electromagnetic force from repulsion between conductors or between conductor and wrapper; the sharp increased temperature due to joule heat on the conductor and wrapper causing thermal instability on the cable. This will further causes the occurrence of tree electric or the failure on insulation; the occurrence of aging on the cable. This is certainly of disadvantage since the continuity of voltage distribution may be disturbed and investment is of disadvantage. The calculation of capacity of thermally permissible short circuit currents in cable is determined by the transfer of heat occurring in cable parts into its surrounding This paper explains calculation/determination of short circuit currents by comparing two methods, namely adiabatic method and non-adiabatic method. The result of study shows that non-adiabatic method better than adiabatic method in determining value of short circuit capacity due to thermal instability on the use of underground TR-XLPE cable of 12/20 kV especially on the selection backfill type, cable burial depth, distance among cables, and distance among lines and also non-adiabatic method is applicable for all durations of short circuit.