Voltage fluctuations and flicker - Assessment and mitigation (part 2)

Voltage fluctuations on a network can have various origins, and all industrial processes are likely to produce them if the short-circuit power at the point of connection and evaluation is low. Without going into the details of disturbances for each activity, we can nevertheless classify these disturbances into two main categories: slow fluctuations and fast fluctuations.

Slow fluctuations are caused by slowly varying reactive loads on the network. They are attenuated by network statocompensators. The bandwidth of the actuators used does not exceed a few hertz. What's more, these devices are generally not designed to eliminate a reverse component, so their operation is balanced.

Rapid voltage fluctuations, which cause flicker, mainly originate in metallurgical activities such as arc furnaces, rolling mills and welding machines. Compensation for the nuisance caused by these disturbances can only be achieved with actuators capable of a bandwidth in excess of 20 Hz.

For the sake of completeness, we need to mention network balancing equipment. They are mainly used to balance three-phase networks supplying single-phase rail traction systems.

In the following paragraphs, we will consider only fast flicker compensators; in their power and control, they include all the features of slow network devices, and their sizing necessarily takes into account the need for rebalancing.

The "Static reactive power compensators" package is the subject of four articles:

D 4 315 Voltage fluctuations and flicker. Assessment and mitigation (part 1)

D 4 316 Voltage fluctuations and flicker. Assessment and mitigation (part 2)

D 4 317 Dynamic reactive power control. Static devices

Doc. D 4 318 Find out more

The subjects are not independent of each other.

Readers will need to refer back to the other issues often enough.