This paper presents a study of Temporary Overvoltage (TOV) on the Manitoba Hydro rectifier system under the proposed development of a new HVDC link and generations. The TOV assessment is based on a full load rejection of three Bipoles, which should result in the highest temporary fundamental frequency overvoltage. The detailed PSSE TOV studies include several system topologies regarding generation and transmission line connections as well as new converter ratings. The paper also discusses the relationship between the system strength described by Multi-Infeed Effective Short Circuit Ratio (MIESCR) and the TOV. A more general analytical equation for estimating TOVs was derived by introducing a multiplying factor related to Bipole parameters. The validation of the equation based on PSSE studies indicates that the revised equation could be used as a screening tool for predicting TOVs in a multi-infeed system.