Effective monitoring and control of power system elements enhance safety and reliability of power supply. Interconnection of power systems in the Southern African Power Pool (SAPP) resulted in optimisation of energy resources. However, interconnection brought complexity that threatened reliability. In 2011, SAPP installed an online visualisation tool, named the SAPP System Viewer, to aid monitoring of the interconnected power system. The project was motivated by the need to minimise accumulation of inadvertent energy, to quickly gather information about abnormal power system conditions, and to independently gather data for measurement of control performance. This paper highlights factors that motivated the project, chronicles its implementation, and discusses lessons learnt. Specifically, the SAPP System Viewer's hardware and software components, data protection, system security, and functionalities are presented. Connecting data servers using inter-Control Centre Communications Protocol is an appropriate way for extending power system visualisation and archiving power system data to multiple remote locations.