We first run up to OPC, which takes control of the governer valves and shuts the Reheat stop valves at 103%. We then electrically disable this feature and run up to 108% electrical trip setpoint. After that, we'll disable (via logic point force) the electrical trip and run up to 110% for the mechanical overspeed verification. During all this testing, we verify with a reed tach locally as well as indicated on DCS. Vibration monitoring is also crucial. There is a complete approved procedure we follow, it also states that we must be online at min. 10% load for 4 hours prior to testing. These are completed annually, usually post-overhaul.