Voltage Flicker

What is Voltage Flicker?

Voltage Flicker, as its name suggests, is an indication of the effect that voltage variations have on the luminescence of an incandescent (filament) light bulb. It has the ability to cause headaches and nausea in staff and nearby residents and can often be one of the most frustrating electrical issues to solve without specialist equipment. If confirmed to be an issue, simply changing bulbs and tubes won’t fix it!

Most people have experienced lights flickering at some point; often during a storm but sometimes for seemingly no reason at all.  In all cases, it is the result of variations in the supply voltage. 

Flicker is a unit-less parameter which is derived from a complex mathematical algorithm that considers both the magnitude of voltage variations and the frequency of these variations.

How is Voltage Flicker Quantified?

In essence, voltage variations are weighted depending on the frequency of the variations, with the highest weighting being applied to magnitudes of approximately 8Hz. Experiments have shown that humans are particularly sensitive to this frequency of light variation.

Figure 1 below shows the waveform of a voltage whose magnitude is varying from cycle to cycle. The result is a lower frequency voltage envelope that’s superimposed on the system voltage; and it is the magnitude of the voltage variation and the frequency of said voltage variation that combines to produce the weighted flicker value.

Figure 1 – voltage variation envelope superimposed on supply voltage

Where does Voltage Flicker come from?

Voltage flicker can either be imported from the supply voltage or generated locally by variations in the load levels.

Locally generated Voltage Flicker is produced by loads that produce rapidly changing reactive power (kVAr). Examples include frequent starting of large motors or thyristor controlled heating.

If Voltage Flicker is locally generated then there are solutions available to minimise its impact. Voltage Conditioners or UPSs on dedicated supplies are an option, or if the voltage to an entire site needs stabilising, dynamic reactive power control or the use of inverters on large motors.

If Voltage Flicker is imported from the grid and it is beyond the IEC 61000-2-2 limits then the consumer can challenge their local distribution network operator (DNO) to implement measures to reduce the voltage flicker.

How we can help

Using our state of the art Power Quality Analysis equipment, PureSine can can identify the presence of Voltage Flicker and its origin (internal or external).

Assuming that the origin of the Voltage Flicker is internal, PureSine are able to offer mitigation equipment through our various partners. We can help throughout the process; from specification right through to installation and commissioning.

Even if our analysis shows that the source of the Voltage Flicker is found to be external then the results of our analysis can be used as evidence to support a request to improve the quality of the supply.

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