Perlindungan Dari Petir Pada Jembatan timbang

Perlindungan Dari Petir Pada Jembatan timbang

(Lightning Protection)

Perlindungan Dari Petir Pada Jembatan timbang (Lightning Protection)
LIGHTNING PROTECTION

When thunder roars, go indoors!  Taking shelter under trees offers little safety from lightning.

Nearly one-third of the people killed by lightning last year were under a tree when they were hit. Do not just standthere counting the seconds between lightning flash and thunder to estimate the distance between yourself and lightning. By the time you calculate it, it may be too late. Sometimes thunder and lightning happen simultaneously. Another third of lightning-strike victims were on their way to shelter when they were struck.

Lightning safety tips:

• Get into a fully enclosed building or hardtop vehicle at the first rumble of thunder.
• Stay indoors for 30 minutes after the last thunder clap.
• Monitor the weather forecast and have a plan for getting to safety in case of a thunderstorm.
• Do not use a corded phone during a thunderstorm unless it is an emergency; cell phones are safe.
• Keep away from plumbing, electrical equipment and wiring during a thunderstorm.

In this installment, we focus on the importance of proper grounding for safety and the performance of sensitive electronic devices. The idea of grounding is that the earth itself acts as the electrical ground, providing not only a common reference for all electrical devices, but also a standard between devices regardless of location. The earth is used as the common reference conductor. The consideration that the earth acts as a constant conductor is the underlying principle, and in the larger sense, it does. However, the connection to the ground or “earthing” needs to have the lowest resistance possible. Any resistance due to improper or faultyconnections will allow the presence of a current to flow. In the context of safety, currentflowing through a vital organ is what causes injury or death. The frequency of the alternating

current, the duration of contact, and the path of contact are all important factors  in determining the severity of the shock.

Current Level (in milliamperes) Probable effect on human body

1. 1 mA Perception level. Slight tingling sensation. Still dangerous under certain conditions.
2. 5 mA Slight shock felt; not painful but disturbing. Average individual can let go. However, strong involuntary reactions to shocks in this range may lead to injuries.
3. 6-30 mA Painful shock, muscular control is lost. This is called the freezing current or “let-go” range.
4. 50-150 mA Extreme pain, respiratory arrest, severe muscular contractions. Individual cannot let go. Death is possible.
5. 1000-4300 mA Ventricular fibrillation (the rhythmic pumping action of the heart ceases). Muscular contraction and nerve damage occur. Death is most likely.
6. 10,000 mA Cardiac arrest, severe burns and probable death.