An OPC Tutorial is available in the DIgSILENT download area (http://www.digsilent.de/index.php/downloads.html) under Advanced Tutorials.
The tutorial contains an OPC guide with information on how to establish a connection between PowerFactory and an OPC server (connected to other applications like SCADA-Systems, GIS, etc.). Moreover, you will find instructions on how to use the included examples based on Matrikon OPC.