Abstract: A method of testing a gas-cooled electrical generator (12) for leakage of pressurized coolant gas includes steps of communicating a container (14) with pressurized coolant gas that is within the generator (12); sealing the container (14) once the container (14) becomes filled with coolant gas at a pressure which is equal to a pressure within the sealed space; and subsequently comparing the pressure in the sealed space with the pressure in the sealed container (14), whereby a lower pressure in the sealed space will indicate coolant leakage. Preferably, the container (14) is insulated to preserve the coolant gas at the temperature it was at within the generator (12), for accurate measurements. In contrast to previously known methods, this method can be performed while the generator is operational, resulting in improved and more realistic detection and measurement of leakage.

Abstract: An overspeed trip system for a steam turbine. A pressure switch is installed at the discharge of an oil pump that is driven by the rotor shaft and that rotates at the same speed as the rotor. The discharge pressure of the oil pump is proportional to the rotational speed of its impeller. When the pressure switch senses that the oil pump discharge pressure exceeds a predetermined value, thereby indicating that the rotor has reached an overspeed condition, it activates a solenoid operated valve that causes oil to be dumped from the line supplying control oil pressure to a throttle valve actuator. The throttle valve is spring loaded to close so that when the oil is dumped, the throttle valve closes, thereby effecting a turbine trip.