Stand-alone outdoor equipment that are less than 6 m (20 ft) tall have a low to moderate probability of a lightning strike in most locations.
If a system (such as a visibility meter) is installed in an open airfield with no other taller structures nearby, the risk of a direct lightning strike increases.
The feasibility of a separate lightning protection system increases when approaching the equator.
The main reason for local grounding is electrical safety, especially in TT distribution systems where the ground is made with a local ground electrode. Observe local or contractual requirements for the needed maximum grounding resistance.
Local safety ground also enables the AC (mains) power line and signal line transient protectors (such as Termbox1200) to conduct the transient currents safely to ground. Systems with two or more structures (for example transmissometers) use a local bonding electrode to interconnect the units to the same potential for signal integrity. This bonding wire also acts as a moderate grounding electrode.
Even in cases of TN or IT systems, connecting the equipment chassis to the ground potential is beneficial to the transient protection.
Vifaa vya nje vya kujitegemea vyenye urefu wa chini ya mita 6 vina uwezekano mdogo wa mshtuko wa umeme katika maeneo mengi. Ikiwa mfumo (kama vile kipima-maono) umewekwa katika uwanja wa ndege ulio wazi bila miundo mingine mirefu karibu, hatari ya mshtuko wa umeme unaongezeka. Uwezekano wa mfumo tofauti wa ulinzi wa umeme huongezeka unapokaribia ikweta. Kwa sababu ya msingi wa ardhi ya ndani ni usalama wa umeme, hasa katika mifumo ya usambazaji wa TT ambapo ardhi ni kufanywa na electrode ya ardhi ya ndani. Kuzingatia mahitaji ya ndani au mkataba kwa ajili ya mahitaji ya kiwango cha juu cha upinzani grounding. Usalama wa ardhi ya ndani pia inaruhusu AC (mains) line nguvu na signal line transient walinzi (kama vile TermBox 1200) kuongoza transient mikondo salama kwa ardhi. Mifumo yenye miundo miwili au zaidi (kwa mfano transmissometers) hutumia electrode ya kuunganisha ya ndani kuunganisha vitengo kwa uwezo sawa wa uadilifu wa ishara. Wire hii ya kuunganisha pia hufanya kazi kama electrode ya ardhi ya wastani. Hata katika kesi ya TN au IT mifumo, kuunganisha chassis vifaa kwa ardhi uwezo ni manufaa kwa ajili ya ulinzi wa muda mfupi.