zerosekvensnettverk

A zerosekvensnettverk, or zero-sequence network, is a specialized electrical network used in power system analysis, particularly for fault studies. It represents the behavior of unbalanced currents and voltages that flow during certain types of faults, such as three-phase to ground faults. Unlike the positive and negative sequence networks which model balanced conditions, the zero-sequence network accounts for the components that are in phase with each other during an asymmetry.

The structure of the zero-sequence network is derived from the system's impedance parameters. For most components, like transmission lines and transformers, their zero-sequence impedance is different from their positive-sequence impedance. This difference is crucial for accurately calculating fault currents. Generators and motors also have distinct zero-sequence impedances, which are often higher than their positive-sequence counterparts.

The primary application of the zero-sequence network is to determine the magnitude and path of zero-sequence currents during ground faults. These currents flow through the grounding system and can pose significant risks, including equipment damage and safety hazards. By simulating these currents using the zero-sequence network, engineers can design protective relays and grounding schemes to mitigate these risks. Understanding the zero-sequence impedance is also vital for calculating system stability and for the proper operation of protection systems that detect ground faults.