In-Kyu Choi

Field Adaptability Test for the Full Load Rejection of Nuclear Turbine Speed Controllers using Dynamic Simulator

This paper describes the speed control functions of the typical steam turbine speed controllers and the test results of generator load rejection simulations. The goal of the test is to verify the speed controllers ability to limit the steam turbines peak speed within a predetermined level in the event of generator load loss. During normal operations, the balance between the driving force of the steam turbine and the braking force of the generator load is maintained and the speed of the turbine-generator is constant. Upon the generators load loss, in other word, the load rejection, the turbine speed would rapidly increase up to the peak speed at a fast acceleration rate. It is required that the speed controller has the ability to limit the peak speed below the overspeed trip point, which is typically 110[%] of rated speed. If an actual load rejection occurs, a substantial amount of stresses will be applied to the turbine as well as other equipments. In order to avoid this unwanted situation, not an actual test but the other method is necessary. We are currently developing the turbine control system for another nuclear power plant and have plan to do the simulation suggested in this paper.

Selection of Operating Parameters and Management of Operation Console for Protection and Control of Steam Turbine in a Korea Standard Type Nuclear Power Plant

This paper contains the selection of operation parameters for protection and control of steam turbine in a Korea Standard Type Nuclear Power Plant. The safety of nuclear reactor must be ensured which generates nuclear energy and produces steam. Also, the safety of turbine, which consume the nuclear energy as a core machine, must be ensured. For the purpose of this, we describe how the operating parameters were selected, reviewed, implemented into the operator console and finally put into actual operation of the system.

The Reduction of Generator Output Calculation by Using 6σ Method on Steam Turbine Simulator in a Nuclear Power Plant

This paper describes the improvement of the calculation by using method on steam turbine simulator in a nuclear power plant. The simulator is essential to not only verification and validation of control logic but also making sure of control constants in upgrading the long time used control system into the new one. And the dynamic model is a key point in that simulator. The model used during the retrofit period of the turbine controller in Kori Nuclear Power Plant makes difference in calculating generator output and control valve positions. That is because such operating data as the main steam pressure, the main steam temperature and control valve positions of Yongkwang #3 are different from those of Kori #4. Therefore, the model parameters must be tuned by using actual operating data for the high fidelity of simulator in calculating the dynamic characteristic of the model. This paper describes that the method is used in improvement of precision of generator output calculation in the steam turbine model of the simulator.

Development of Process Model for Turbine Control Valve Test in a Power Plant

A turbine control system which has been operated for years in a nuclear power plant was retrofitted with a newly developed digital control system. After completion of the retrofit, turbine valve tests were performed to ensure the integrity of each valve`s control function. The sequence of each valve test is composed of a closing process and a reopening process. To minimize megawatt variation which normally occurs during the test sequence, we employed a kind of compensator algorithm in the new digital control system which also have been used in the old system. There were difficulties finding optimal parameter settings for our new compensator algorithm because the power plant didn`t allow us to perform necessary tuning procedures while the turbine is on load operation. Therefore an alternative measure for the compensator tuning which is independent of the turbine actual operation had to be implemented. So, a process model for the test was required to overcome this situation. We analyzed the operation data of the test and implemented the process model by use of input and output variable relations. Also we verified the process model by use of another condition`s operating data. The result shows that the output of model is similar to the actual operation data.

Determinations of Initial Control Parameters According to the Application of Control System for Feed Water Pump Turbine into a Nuclear Power Plant

This paper describes one of the ways how to decide the initial control parameters after the analog type control system is changed to digital control system. If the old control parameters were already known, the initial control parameters for initial operation could be decided easily. But sometimes, it is very difficult for the control system developer to decide initial parameters before plant machine starts up. In that case, if there is a big difference between initial parameters and optimal parameters, the whole plant itself can be in very dangerous conditions. Here is a very simple experimental method which can be very easy but useful to engineers.

Development of Speed Controller and its Application to a 680[MW] Rated Steam Turbine

An analog type turbine control system in a nuclear power plant in Korea was replaced by a digital type control system successfully. The turbine simulator was used to verify and validate the perfection of newly developed digital control system prior to its actual installation. In this paper, the newly developed turbine speed control system, ie. governor will be introduced together with how to simulate entire control loop. After that, we will compare the comparison of simulation result in laboratory with pre startup simulation result. Eventually the performance of actual operation result was testifed.

Digital control system development for turbine control of nuclear power plant

Turbine control system (TCS) controls the speed of turbine and the load of generator. Its reliability directly affects the stability of turbine operation and the quality of electric power. In Korea, the nuclear power plant (NPP) have supplied fundamental portion of domestic electric energy consumption for over 20 years. Demands for retrofitting old TCSs have increased as time goes on because of maintenance difficulties and spare parts shortage. Last year, Korea Electric Power Institute (KEPRI) developed a digital TCS (DTCS) and used it for retrofitting an analog TCS in a NPP. The result was success, and the turbine has been operated reliably with the new DTCS for over one year from initial start up. This paper describes major features of the developed TCS and the results of application.