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Teacher Angelo Baggini


The voltage system in any three phase electrical installation is expected to be balanced (voltages equal in magnitude and displaced to each other by 120o). In practice, it is not possible to have the full balance at all nodes of the power system.

The main sources of the long-term unbalance are unbalanced loads, primarily single-phase loads existing mainly in low-voltage and medium-voltage networks. These loads cause non-equal phase currents to flow in the power system and unbalanced voltage drop on the system components. As a consequence, voltage balance at the nodes is lost. Voltage unbalance can also result from different self- and mutual impedances of individual phases of transmission system components, and particularly those of overhead lines. In this case, different voltage losses are produced even when a load is symmetrical.

This course describes the voltage and current unbalance phenomenon in electrical power networks. Considerations relate mainly to long-term unbalance occurring in normal steady state conditions due to operation of loads or asymmetry of network elements. Short-time unbalance can appear only under disturbance conditions, for example during an unsymmetrical short-circuit. Effects of unbalance on the main electrical equipment together with mitigation techniques will be presented.

Target Audience

electrical engineers


electrical engineering

Duration (hours)