Causes of Unbalanced Voltages and Currents

Practical imperfections which can result in unbalances are:

  • A three-phase equipment such as induction motor with unbalance in its windings. If the reactance of three phases is not same, it will result in varying current flowing in three phases and give out system unbalance.

With continuous operation, motor’s physical environment cause degradation of rotor and stator windings. This degradation is usually different in different phases, affecting both, the magnitude and phase angel of current waveform.

A current leakage from any phase through bearings or motor body provides floating earth at times, causing fluctuating current.

  • Any large single-phase load, or several small loads connected to only one phase cause more current to flow from that phase causing voltage drop online.
  • Switching of three phase heavy loads results in current and voltage surges which cause unbalance in the system.
  • Unequal impedances in the power transmission or distribution system cause differentiating current in three phases.

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Posted in Power Quality Monitoring.