Possibilities for turbine trip due to hotwell tank level High
The steam after passing through low pressure turbine it goes to the condenser. In the condenser, the steam is turned in to water. Upon passing the turbine, the steam density, temperature and pressure get reduced. Hence, to suck the steam, a vacuum pressure is applied on steam by the condenser. Then the steam reaches the condenser and touches the water tubes which are carrying cool water from cooling towers and then the steam condensates in to the water and the water is collected at the bottom of the condenser. Here, the temperature of the water in the condenser will be approximately 30 to 40 degree Celsius. Hence, condenser is commonly called as HOT WELL.
The hot well level is to be maintained to normal level (200mm). This is why because, if the water level in the hot well goes below the desired level, the vacuum level increases so that the low pressure turbine blades gets sucked along with the steam by the vacuum pressure and if the water level in the condenser raises above the desired level, then deterioration of vacuum takes place. Hence, the water level in the hot well should be maintained to a fixed level. Thus undesired water level in the hot well effects power plant efficiency.
When the water level is less than normal level say 199 mm, then in order to make the water level to normal level, make up valve should be opened so that the water from demineralized water plant will flow in to the hot well and makes water level to normal. If the water level is much less than 199mm i.e., when 190mm then make up valve make use of emergency valve to make the hot well level to the normal level, that means these two valves get open at a time. And if the water level raises above normal level say 201mm then excess water is to be moved out to the DM plant. This will be done by drain valve.