Voltage quadrupling on a UD cable

The results of EMTP (electromagnetic transients program) investigations verify the concept of quadrupling of the riser pole arrester discharge voltage when a cable not equipped with an open tie arrester is subjected to a bipolar surge. This phenomenon occurs when the bipolar surge magnitude is sufficient to force the riser pole arrester well into conduction and when the cable is of the proper length. Voltages in the range between two and four times the riser pole arrester discharge voltage can occur as a result of this phenomenon. Furthermore, on cables equipped with open tie arresters, the voltage was found to rise as high as 1.9 times the 10 kA riser pole arrester discharge voltage. The bipolar surge simulations performed with EMTP resulted in cable voltages that were much higher than those created by monopolar surges