Thousands of tonnes/hour of Superheated Steam from fossil fuel fired boilers or from atomic reactors of modem power plants and hundreds of tonnes/hour as byproduct from waste heat boilers of many process plants - the ideal motive force - run large capacity steam turbines. Turbine Bypass System (TBS) is necessary for safe boiler start, stabilization, and smooth boiler and turbine runs despite severe load variations and even sudden trips. This article discusses in details first steam conditioning and then TBS.