A computer model, based upon measured equipment impedances, has been formulated for the prediction of the electromagnetic noise generated by valve firings in HVDC convertor stations. Simple lumped circuit concepts are used so that the model can readily be applied to any convertor station; it can thus be described as generic. It has been used to predict the noise generated in the frequency interval from 5 to 500 kHz at the Dickinson convertor station and validated by comparing the results with RF spectra measured at the station. A key feature is the use of measured impedances of actual equipment in the model, rather than idealised components.