After a series of ACB tripping at Main Switchboard of a chemical plant in SC Plant Pasir Gudang, the client had commissioned PowerQ to investigate the cause. PowerQ had performed the electrical monitoring of the Main Control Central Board and spot measurement of the MSB supplying power to MCC.
The inrush current was recorded at individual motors was performed at using PQ recorder. The data collected has been analyzed and checked against IEEE 519 standards.
Following recommendations implemented to prevent the tripping problem:
To avoid this scenario, the soft starter was recommended to be set to limit current to 300% and/or ramp time of the soft starter should be increased. Generally, a ramp time of 8 second should be sufficient to limit inrush below 300%. This was be done in confirmation with process' requirements. It was recommended that the correct setting of soft starter shall be implemented so as to reduce chances of tripping due to the starting current.