Simple method of fast discharge of capacitor banks using delta connected transformers: modelling and experimental testing

The discharge of capacitor banks at substations is necessary before their connection to the grid can occur. This study investigates the use of delta-connected transformers for capacitor discharge. The energy from the capacitor banks is discharged by driving the transformers into saturation after disconnection from the grid. To investigate this, simulations were conducted in PSCAD to identify the relationship between the size of the transformer, the size of discharge resistor and the time taken for the capacitor bank to discharge. To confirm the accuracy of the PSCAD simulations, a scaled physical model was constructed in the laboratory and discharge results were recorded. A PSCAD simulation of the scaled model was also created to directly compare the accuracy of PSCAD. It was found that PSCAD produced accurate representations of the laboratory model, resulting in a greater confidence in the full-scale results.