In this paper, we use a standard pulse generator as the test signal source and passing it through a high frequency current transformer (HFCT) to simulate the partial discharge (PD) and study the effect of various configurations of grounding. The detected signals were compared with the original signals generated from the standard pulse generator. When the grounding has different resistance, the detected signal from the HFCT shows different amplitudes for the same simulated PD signal. For the cases of changing the number of groundings to the oil-immersed transformer, the signals that the HFCT measured also show different results. The locations of the simulated PD in the primary winding, second winding, and shell of an oil-immersed transformer, as the coils were not grounded, the amplitude of detected signals by HFCT will also be different. We conclude that when apply the PD measurement using HFCT for high voltage equipments, the measured data should be modified according to the ground resistance, the number of groundings, the PD position, and frequency bands.