A partial discharge (PD) within a transformer can be considered as a high frequency transient event, therefore the development of high frequency models may inform the process of pd source location and evaluation. PD activity in large transformers can be detected using wideband sensors (vhf up to 500MHz)and therefore any model should be broadband. The use of a laboratory experimental model containing both interleaved and plain disk windings has provided a range of time and frequency response data that has yielded models based on lumped circuit parameters. Other modelling approaches are being investigated as well as techniques for determining PD source location based on the developed models and measurements of PD activity made at the bushing tap and neutral to earth points.