1. Field of the Invention
The invention relates to an on-line diagnostic system for a seal oil system associated with a gas-cooled electric generator.
2. Description of the Prior Art
Modern electric generators such as those driven by steam turbines have the capacity to generate currents of thousands of amperes in their stator windings. Such arrangement also generates a large amount of unwanted heat due to stator and rotor winding resistance as well as windage losses. Accordingly, a cooling system must be provided in order to remove the heat resulting from the electrical and windage losses during normal operation.
One type of cooling system utilizes a flow of cooling gas, such as hydrogen, within the generator housing as well as within the rotor and stator structures to remove the produced heat.
The hydrogen cooling atmosphere must remain within the generator housing, and since the rotor shaft ends of the generator extend through the gas tight enclosure, provisions are made to prevent the escape of gas along the shaft. To this end, shaft seals, known as gland seals are provided. An auxiliary seal oil system supplies the gland seals with oil under pressure to prevent the escape of hydrogen gas from the generator as well as to provide lubrication to the gland seals.
The seal oil system includes seal oil pumps, coolers, filters and a multitude of valves and monitoring devices such as gauges and alarm switches. Proper operation of the seal oil system is maintained by an operator's visual inspection of the gauges. Audible alarms are provided for critical functions such as low seal oil pressure or abnormal oil levels, for example.
An abnormal gauge reading may occur at a time when the operator is not monitoring the gauges and an alarm signal may not indicate the basic problem leading up to the alarm. The present invention provides for on-line continuous monitoring of the seal oil system and can indicate to an operator possible abnormal conditions which may be developing so that corrective action, if any, may be taken at the incipient stage of a possible malfunction.