Data errors caused by surge voltages on paired-conductor lines

Impulse voltages may be coupled onto paired-conductor telecommunication lin es by lightning or by disturbances on nearby power lines. These common-mode impulses are converted to differential-mode by unbalance of the conductors or by operation of surge protectors. Many of these differential-mode impul ses can cause large numbers of bit errors and interfere with digital transm ission. Statistical models have been previously developed to determine the common-m ode to differential-mode conversion of impulse voltages on cable pairs. In this paper, those models are used to predict interference with digital tran smission during lightning activity. This possible interference is expressed as expected number of errored seconds within one hour of lightning activit y. Since operation of surge protectors causes data errors, this paper also examines how impulse limiting voltage of protectors affects data disturbanc es.