Flicker is a perceptual phenomenon that results from noticeable changes in light intensity leading to visual disturbances. This effect is primarily due to voltage fluctuations within the electrical system, which, in turn, lead to changes in light density in lamps and other light-emitting devices. From a certain threshold value, the appearance of flicker can be disturbing. This effect of voltage variations depends on the extent of the repetition rate and the curve form of the change in voltage. The short-term flicker strength and long-term flicker strength are defined measures of the disturbing effect.

The impact of flicker can range from mild annoyance to serious disruption. At best, flicker can be a minor distraction. At worst, it can cause headaches, eyestrain, and in extreme cases, can trigger symptoms in individuals with photosensitive epilepsy. In industrial settings, flicker can disrupt sensitive equipment, leading to operational inconsistencies and potential downtime.

A common cause of flicker is the presence of high-power, non-linear loads on the electrical network. Devices like air conditioners, heaters, and industrial equipment can cause substantial voltage fluctuations when they switch on or off. This momentarily disrupts the balance of the system, leading to flicker. Unstable power sources and network faults can also contribute.

Voltage variations caused by individual devices on the low-voltage network are permissible if the resultant flicker disturbance factor is not greater than 1. The long-term flicker disturbance factor, averaged from 12 values, must not exceed a value of 0.65. The simplest method for evaluating the value is the = 1 p.u. curve. P.u. stands for the "unit of perception." This is the maximum tolerance level for interference sensitivity of the human eye's perception of light fluctuations. It is not permissible to exceed the value = 1 p.u. in combination with all interferers.

Managing and mitigating flicker is achievable. Monitoring devices, like our UMG Series, can be used to detect and quantify the level of flicker. Mitigation strategies include balancing loads across phases to prevent sudden voltage drops or spikes, improving power supply stability and utilizing power conditioning devices, such as voltage regulators or power factor correction units. Managing the operation of high-power devices to prevent simultaneous switching can also help reduce flicker.

  • Fig.: Development over time of short-term flicker (PST)

  • Fig.: Practical example for flicker: Gravel quarry

  • Fig.: Development of flicker

  • Fig.: Effective power development dependent on the volume and consistency of material