training also can help reduce the hazards of static electricity. Foe example, some retail gasoline stations post information to reduce the likelihood of static buildup when customers slide in and out of their vehicle while fueling it or use cellular phones during operations that are likely to generate static charge
There are instruments for measuring the presence and amount or static electricity. The instruments measure electrical potential of charged objects or surfaces.
Hospital patients
medical patients may have equipment and instruments attached inside or outside their bodies. Small currents leaking from one instrument to another may be sufficiently large to cause injury or death. There are many ways a patient can become part of a circuit : a patient could reach out and directly contact equipment ; hospital staff could be in contact with electric equipment and touch a patient ; even a person cleaning the floor with a vacuum cleaner could create a leakage current hazard. A serious exists when a patient has a catheter in or near the heart or has an electrical connection attached to or near the heart during treatment, monitoring, or surgery
A variety of techniques reduce the risk to a patient. Grounding and double insulation help. Isolation of circuits and sensor leads, minimal current for equipment operation,low voltages,and turning off unused equipment can all help. Shielding reduces magnetically induced current. Some patient situations can can become very complex, requiring special analysis to determine a safe solution. There are safe current limits and standards for the safe us of electrical equipment in hospitals and medicine.
Lightning
lightning is the sudden release of static buildup in clouds, particularly during thunderstorms, which can produce very large current. Lightning has occurred at nearly every location on our globe. However, there is a wide range in frequency of occurrence. Each year in the United states, lightning kills approximately 150 people and property damage reaches millions of dollars. Lightning can cause external damage to property, such as structural damage,heating,and fire, as well as internal damage to electrical distribution and communication and data systems within a building.
A system of lightning rods or air terminals connected to a special ground rod is the normal method for providing external protection. Air terminals connected to a special ground rod is the normal method for providing external protection. Air terminals are placed strategically along roof lines, on protruding building elements ( chimneys,dormers,etc.),or in the form of a protective grid. The air terminals intercept lightning in their vicinity and conduct the current to the ground.
Internal protection is achieved most commonly by providing common grounding point for all systems in building. Other means include the use of surge-diverting or protection devices on electrical equipment, placing electrical equipment distant from lightning protection equipment,shielding of equipment and wire,and use of stranded and twisted overcurrent protection