Surge Propagation Characteristic of Cables Fixed to a Tower

Surge propagation chracteristic of cables fixed to a transmission line tower is not studied well, in comparison with the case of the tower itself. This paper studies characteristics of the surge propagating between the cable and the tower based on experiments with a step pulse voltage injection to 77kV XLPE cables fixed to a mean scale tower. We also investigated to the possibility to regard the tower as the ground in EMTP calculation for simulating those experiments. As a result of the test, we have found that aluminum cleats caused a significant influluence to the character of the surge propagation between the cable sheath and the tower. Aluminum cleats fixing cables to the tower makes the apparent speed of the surge to be delayed. Moreover calculation techniques were developed to get more accurate values of surge impedance and velocity, when we considered about the cable with wire stranded shielding in EMTP simulation. This paper describes details of experiments and the mechanism of cleats' influence using numerical simulations by the EMTP.