STEAM TURBINE & GENERATOR ARRANGEMENT

STEAM TURBINE ARRANGEMENT

The live steam enters the HP turbine through the main stop valves (MSV) and the main control valves (GOVERNORS). After expansion in the HP turbine, the steam is let to the cold reheat line via power assisted check valve. The steam passes the reheaters of Boiler before it enters the IP turbine via the intercept stop valves (RCV) and the intercept control valves (ICV). The intercept stop and control valves are combined valves, that means stop and control valve are arranged in one common casing. The steam is let from the IP turbine to the LP turbine by the crossover pipe.  From the LP turbine the steam is fed to the condenser.

The turbine has journal two journal bearings for each rotor and one thrust bearing, of forced lubricated type.

 CONTROL  AND LUBRICATING OIL SYSTEM

The lubrication oil for the turbine bearings and control oil for the actuator positioning is supplied by Control and Lubricating oil system. During normal operation, main oil pump (MOP) driven by AC motor supplies the lubrication oil. A standby pump auxiliary oil pump (AOP) driven by AC motor supplies lubricating oil at the failure of (MOP). When MOP and AOP doesn’t work or can’t provide lubricating oil with adequate pressure, an Emergency oil pump (EOP) driven by DC motor supplies the lubricating oil. The oil discharged to supply lubrication oil for the Turbine Bearings.

Control oil is used to operate the “main stop valves, governing valves, reheat stop valves and interceptor valves” Servomotors and to operate an oil supply for trip system, this Control oil is supplied by 2 Control oil pumps (COP).

CONDENSER (HEAT EXCHANGER)

The condenser receives exhaust steam from the low pressure turbine. Circulating water flows through the condenser tubes to remove heat from the condenser, which causes the exhaust steam to condense. a sudden reduction in volume occurs which establishes a Vacuum in the condenser

The condensate steam is collected in the hotwell which is located in the bottom of the condenser. The hotwell stores the condensate for re-use and recirculation in the water/steam cycle.

The condenser is located directly beneath the low pressure turbine. As the steam exits the LP turbine, it flows over the condenser tube bundles which are oriented horizontally and perpendicular to the axis of the turbine.

GENERATOR

 Electrical Generator is the source of Electricity generated at the power plant; it is a synchronous generator whose output voltage is 19000 Volts, 50 Hz, 350 MW, with 3000 rpm.

For this big turbo generator .it is cooled by hydrogen gas for its small density, excellent cooling properties and decrease windage and ventilation loss, Also Hydrogen has large thermal conductivity and heat transfer coefficient, therefore, generator output per unit weight of active materials will increase.