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 MIL-HDBK-419A
1.3.3.5.11 Secondary AC Surge Arrester. Installation of a properly selected secondary ac surge arrester at the
facility main service disconnect means provides the best method for ensuring that high energy transients are
not coupled to equipment by ac distribution lines within the facility. The surge arrester installed must have
certain characteristics to ensure adequate protection.
Characteristics.
a.
(1) Be capable of safely dissipating transients of amplitudes and waveforms expected at the
facility for a predetermined period of time. Selection of an arrester that will provide protection for a period of
ten years is recommended.
(2) Have a turn-on time fast enough to ensure that transient energy will not cause damage before
the surge arrester turns on and clamps.
(3) Maintain a low enough discharge (clamp) voltage while dissipating transient current to prevent
damage to protected equipment.
(4)
Have a reverse standoff voltage high enough to ensure nonconduction during normal operation.
(5)
Be capable of complete extinguishing after firing on an energized line.
Additional requirements. In addition to the above, the surge arrester must be properly installed to
b.
ensure optimum operation. The input to each phase arrester contained in the surge arrester should be fused to
provide protection against overload of, or damage to, the ac supply in the event an arrester should short. Also,
indicator lights and an audible alarm that go off when a fuse opens should be provided on the front of the surge
arrester enclosure as a maintenance aid.
1.3.3.5.12 Surge Arrester Installation. Proper installation of the surge arrester is of vital importance for
optimum operation. A surge arrester with excellent operating characteristics cannot function properly if
correct installation procedures are not used. The most important installation criteria are provided below and
applies to surge arrester phase input connections and the ground connection. All surge arresters should be
installed in accordance with the manufacturer% recommendations.
Installation criteria.
a.
(1) If possible, install arresters inside the first service disconnect box to keep interconnecting lead
lengths as short as feasible.
(2) Use interconnecting wire of sufficient size to limit resistance and inductance in the transient
path to ground through the surge arrester.
(3) Interconnecting wiring should be routed as straight and direct as possible with no sharp bends,
and the least number of bends possible.
(4)
Do not include loops in the wiring.
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