Steam turbine is the heart of every thermal power plant. Steam turbines in the cogeneration plants primarily generate power and steam for captive consumption purposes, along with export of electricity to the state grid which enhances the energy efficiency and production capacity of process plants. This will not only result in considerable savings, but also leads to a sustainable supply of electricity and additional revenue from the surplus electricity generated.
Steam turbine in the power plant encounters continuos operation and maintenance concerns due to varying grid conditions and process demands. To counter this adequate protections and controls be connected to the turbine system for smooth and reliable operation. For the reliable and trouble free operation and protection of such industrial steam turbines, it is important to include steam turbine control and safety systems to avoid failures thus shutting down the turbine.
Protections and controls for steam turbines should be designed such that the protection system safely isolates the turbine during abnormal grid/fault conditions or shuts down any plant process equipment during abnormal conditions. Such protection and control systmes sense/ determine unsafe conditions and ensure that no single-point failure will affect the complete system reliability or availability. System failures are detected, annunciated, isolated and allowed to be repaired or replaced while the monitored system continues to operate on-line, increase realiability, reduce maintenance, improve diagnostics and employ more precise control onsteam turbines.
With over 4 decades of experience and continuos development in steam turbine technology, Triveni is the preferred brand of power producers internationally wherein steam turbines are engineered, manufactured and commissioned considering the varying grid / process conditions and safety of the system.
With an installed base of more than 3000 units worldwide, Triveni proves that its reliable and robust steam turbines are globally accepted. This paper presents a case study on Triveni’s solutions to the steam turbine control and protection system failures.
The probable causes of non opening of circuit breaker in isolating the fault when the respective protection relay has operated are due to no auxiliary power supply to trip coil of circuit breaker (failure of the mains supplying power to the trip coil) and failure of trip coil of circuit breaker
In case of no auxiliary power supply to trip coil of circuit breaker or failure of trip coil of circuit breaker, if the respective circuit breaker fails to trip even after initiation of trip command from the grid or generator protective relay, breaker backup protection (LLB) or generator protection relays initiates tripping of the next upstream circuit breaker, thus isolating the TG from the grid.
Consequences of failure of circuit breaker opening
Solutions from Triveni