CATV electrical and electronics equipment are typically exposed to a wide variety of electrical transients whether underground, on the ground, on the pole or hanging from a strand. Poor local power quality can result in utility line disturbances due to nearby switching, phase imbalances and load changes, entering the AC power supply input wiring. An AC power line protector, e.g. 587B151, can eliminate adverse effects on the input of a ferroresonant transformer or various UPS input circuits by limiting overvoltage levels to a few hundred Volts. A protector on the 60Vac quasi-square wave PS output can work together with the transformer impedance to limit overvoltages on the output. Transients generated by a lightly loaded ferroresonant transformer would also be limited. Transients on the coax, even aggravated by longitudinal sheath currents, seldom pose a threat to the RF path because of its low impedance to ground at the low frequencies typifying such transients. The input to the trunk power supply via the power decoupling network has significantly higher impedance at transient frequencies and can definitely benefit from enhanced overvoltage protection. Trunk amplifier power supplies can use PIP60 type protectors to substantially improve upon the performance of the GDT at the coaxial input. Stopping transient effects in the power supply input circuits can prevent transient energy from reaching and damaging costly broadband RF amplifier modules in trunk and bridger amplifiers.
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