(d) Overshoot voltage. Overshoot voltage should be the lowest voltage that can be obtained,
for the shortest time possible, using the best state-of-the-art suppressors available.
(e) Clamp (discharge) voltage. Clamp voltage of the transient suppressors should be as low
as possible and not more than 225 percent of turn-on voltage when discharging a transient with 1000 amperes
(f) Operating life. The transient suppressor must be capable of discharging the number of
transients listed in Table 1-19 with peak amplitudes that are 90% of those listed in Table 1-19. Clamp voltage
must not change more than 10 percent over the operating lifetime.
(g) Self-restoring capability. The transient suppressor must automatically restore to the off
state when the transient voltage level falls below turn-on voltage.
Low-energy transient suppressor characteristics.
The reverse standoff voltage rating of the transient
(a) Reverse standoff voltage.
suppressor should be between 200 to 300 percent above the nominal line voltage for spark gap type suppressors.
For MOV, ZNR, and SAS type suppressors, the reverse standoff voltage should be 175 25 percent of the
nominal line voltage.
(b) Turn-on voltage. Turn-on voltage of the suppression component at the equipment must
be as close to reverse standoff voltage as possible using state-of-the-art devices, and shall not exceed 125
percent of reverse standoff voltage.
(c) Overshoot voltage. Overshoot voltage must be the lowest value that can be obtained, for
the shortest time possible, using state-of-the-art suppressors. Overshoot voltage shall be low enough to
preclude equipment damage or operational upset. The requirement will apply for transients with rise times as
fast as 5,000/s.
Leakage current to ground should not exceed 100 microamperes at
(d) Leakage current.
reverse standoff voltage.
(e) Clamp voltage. Clamp voltage must remain below the equipment withstand level while
dissipating transient currents with peak amplitude that are 10 percent of those listed in Table 1-19. The clamp
voltage must not change more than 10 percent over the operating lifetime.
(f) Operating life. The transient suppressor must be capable of safely dissipating the
number of transients listed in Table 1-19, with current amplitudes that are 10 percent of those listed in
RF coaxial lines (above 3 MHz). At the present time, there is some difficulty encountered in
providing effective transient suppression for lines that conduct signals above 3 MHz in frequency, and especially
above 10 MHz. Most suppression devices that provide low-level clamping of transients have enough capacitance
to create high insertion losses when installed line to ground on the conductor. Packaging of the devices for in-
line installation without causing high insertion losses is also difficult and expensive. Gas-filled spark gaps have