Spänningsdipp

Spänningsdipp, often referred to as a voltage dip or sag in English, is a temporary reduction in the voltage level of an electrical power system. It is a common phenomenon that can occur for various reasons, including the starting of large electrical loads, short circuits, or faults within the power grid. During a spänningsdipp, the voltage typically drops to between 10% and 90% of its nominal value for a duration ranging from half a cycle to one minute.

The effects of a spänningsdipp can vary depending on its severity and duration, as well as the sensitivity of the connected equipment. Sensitive electronic devices, such as computers, programmable logic controllers (PLCs), and variable speed drives, can malfunction or shut down completely when subjected to voltage dips. This can lead to disruptions in industrial processes, data loss, and significant economic consequences. In some cases, prolonged or deep voltage dips can cause damage to electrical equipment.

Causes of spänningsdipp are diverse. The most frequent cause is the energization of large inductive loads, such as motors or transformers, which draw a significant amount of current upon startup, temporarily lowering the voltage. Short circuits and ground faults are also major contributors, as they create low-impedance paths that draw large currents, leading to a rapid and substantial voltage drop. Other factors include lightning strikes, switching operations on the power grid, and faults in transmission lines.

Mitigation strategies for spänningsdipp involve a combination of power system design and protection measures. Installing surge protective devices, voltage regulators, and uninterruptible power supplies (UPS) can help protect sensitive equipment. For industrial facilities, proper load management and coordination of starting sequences for large motors can minimize the impact of these events. Power utility companies employ various techniques to maintain grid stability and reduce the occurrence and severity of voltage dips.