Spændingsstyrte

Spændingsstyrte, also known as voltage collapse or voltage instability, is a critical phenomenon in electrical power systems that occurs when the voltage at a bus or node in the system drops to a critically low level, leading to a loss of voltage stability. This condition can result in a cascading failure of the entire system, causing widespread blackouts and significant economic and social disruption.

Voltage collapse is typically triggered by a combination of factors, including heavy loading conditions, inadequate reactive power support, and the presence of long transmission lines. As the load on the system increases, the demand for reactive power also rises. If the system cannot provide sufficient reactive power, the voltage at the affected bus begins to decline. This decline in voltage further exacerbates the situation, as the reactive power demand increases with the square of the voltage, leading to a positive feedback loop.

Several mechanisms can contribute to voltage collapse, including the loss of excitation in synchronous machines, the tripping of capacitor banks, and the operation of voltage-dependent loads. Once the voltage at a bus drops below a certain threshold, the system may experience a sudden and rapid collapse, resulting in a blackout.

To prevent voltage collapse, power system operators employ various strategies, such as increasing reactive power support, reducing load, and implementing voltage control measures. Additionally, system planning and design considerations, such as the use of flexible AC transmission systems (FACTS) devices and the integration of distributed generation, can help mitigate the risk of voltage instability.