Statistical models for differential-mode conversion of common-mode impulse voltages measured on telecommunication pairs

Telecommunication networks outside plant facilities are subjected to voltage and current surges caused by lightning storms or by transients on nearby power lines. The impulse voltage induced on a cable pair is common-mode in nature, that is, from each conductor to ground simultaneously. However, the common-mode voltage is converted to a differential-mode voltage between the two conductors of the cable pair by the unbalance of the conductors or the asymmetrical operation of surge protectors. Common-mode voltage levels have been measured in several surveys but not differential-mode voltages. This paper provides statistical models that derive expected differential-mode voltages from measured common-mode voltages. The differential-mode voltages are of interest since they may interfere with digital transmission, and may cause a large number of bit errors.