Flickering lights can have an adverse effect on health, causing fatigue, lack of concentration, migraines and in some cases, epileptic shock. The severity of reaction and sensitivity varies from person to person. Some people can see a higher rate of flickering light than others. Fluorescent lamps can occasionally develop a fault that can cause them to have noticeable flicker.
While health effects are a main concern, the production line of an industrial plant can also be affected. Workers can feel tired and unable to focus as flicker can impede personnel productivity and your bottom line. Besides health-related issues, flickering lights can cause nuisance tripping of equipment because of the misoperation of relays and contactors. Flicker can also cause unwanted switching of UPS units to battery mode as well as problems with sensitive electronic equipment that requires consistent voltage (i.e. medical laboratories).
Indeed, flickering lights are a common symptom of a power quality issue. A potential source of flickering lights is machinery with rapid fluctuations in load current or voltage. These machines include large motors when they are starting up, machinery with cycloconverters such as rolling mill drives and mine winders, as well as machines that use static frequency converters such as ac motors and electric arc furnaces.
Welders, boilers, elevators and cranes, which rapidly change loads, can also be sources of flickering lights if they are connected to the electrical system. Loose connections are another source of flickering lights.
After a while, diagnosing power-quality problems and identifying how to solve them becomes an art as well as a science. A power-quality analyzer or logger can help you avoid nuisance tripping and find what equipment is causing flicker issues by using the event capture feature, which provides waveforms and additional data.