Fast Evaluation Methods for Voltage Sags in Ship Electrical Power Systems

Induction motors are widely used in ship electrical power applications as they are frequently switched on into the supply system, consuming about 70% of the electrical energy generated. Voltage sag, which is produced by the starting current of induction motors, is one of the main causes of sensitive equipment dropout and, as such, must be considered in ship electrical system designs to comply with classification societies´ rules. A simple and fast method that is able to estimate the expected magnitude of voltage sag disturbances and provide information about the effectiveness of the various mitigation methods is essential. This paper aims at presenting a faster evaluation method for voltage sags due to motor start-ups in ship electrical power systems. The performance of the proposed method is validated by measurements gathered from several motor starter designs in practical ship power applications using the Riemann-summation-principle-based evaluation method. The proposed method can provide engineers with useful information about the actual magnitude of sag disturbances as well as on the effectiveness of motor starters for ship electrical power applications, which will assist them in determining proper motor starter designs.