Voltage Fluctuations (Dips and Swells) - Causes and Remedies [Demo]

Voltage fluctuations (dips and swells) can have various causes. powerqualityonline explains how to identify them and how to take remedial action.

In general, a distinction must be made between

•     self-induced voltage fluctuations (dips and swells)                   and
•     externally caused voltage fluctuations (dips and swells)      

• Fluctuating loads (e.g. welding equipment, four-quadrant drives, laser printers and photocopiers)
• Increased mains impedances (single conductors on flatbeds, voltage matching       transformers, isolating transformers, long supply lines)
• Control processes by energy suppliers (load-tap-changers of the transformers)
• Fluctuating feed-in (e.g. regenerative energies, e.g. wind power generation and       solar energy plants)

Loose or bad contacts are also a possible cause. These can be found very easily by means of Thermography.


Load Change and Mains Impedance:

In general, voltage fluctuations (dips and swells) are always based on the relation between load change and mains impedance. Thus, at a 110 kV transformer station, a small drive will not cause voltage fluctuations (dips and swells). However, a steel mill with electric arc furnaces may cause them.

Conversely, a long low-voltage line with a small cross-section (e.g. in case of remote allotments) may provide stable voltage if the load remains unchanged, but significant voltage dips may occur when the coffee machine is switched on.

Please also refer to the section Flicker.

Finding the Cause:

How can I determine the cause of voltage fluctuations? => Please see Practice Voltage Fluctuations (Dips and Swells) .