Response of Telecom Protection to Three IEC Waveforms

Since intentional electromagnetic interference (IEMI) is a concern for fixed installations in the future, it is important to understand the performance of currently installed telecom protection devices to a range of transient voltage waveforms including those that have faster rise times and higher voltages than ordinary design levels. For this reason several types of telecom protection were subjected to three types of voltage transients defined in IEC test standards. These standard transient waveforms cover a wide range of rise times and pulse widths. The types of protection included gas discharge tubes (GDT), metal oxide varistors (MOV), transient voltage suppression (TVS) diodes, TVS thyristors, and resettable fuses. The three transient waveforms considered are the EFT (10/50 ns) defined by IEC 61000-4-4, the CWG lightning surge (1.2/50 μs) defined by IEC 61000-4-5, and the telecom surge (10/700 μs) defined by the same standard. The objectives of this study included: (1) documentation of variations in protection voltage with pulse rise time, (2) documentation of the statistical variation of these properties, and (3) determination of the protection voltage for each waveform as related to the voltage marking of each device.