No abstract

The RAM system is the reactor control rod drive mechanism power supply system, which is the only power supply designed for the control rod drive mechanism. The RAM (control rod Power System) system of the Nuclear Power Plant only has two synchronous generators (RAM001/002AP) operating in parallel. On November 14, 2019,when one unit has an excitation system failure, due to the unreasonable setting of the protection value of the two units, the over-current protection of the unfailed unit precedes the loss of field protection action of the field lost unit, resulting the two generators in the RAM system tripping one after the other, therefore causing CRDM losing all power supply, resulting in the control rod dropping off and finally causing the automatic shutdown of the reactor, bringing serious consequences to the reactor and power grid. Therefore, the setting of synchronous generator protection in the RAM system is very important for the safe and stable operation of nuclear power plant. This report carries out the digital modeling and simulation of the RAM system of the Nuclear Power Plants, simulates various faults of RAM system synchronous generator RAM001/002AP and provides the important basis for verifying the settings of over-current protection and loss of excitation protection.

In recent years, a number of projects under construction in nuclear power plants have successively experienced excitator failures at key nodes of grid connection and commercial transportation, resulting in downtime, which has had a great impact on the progress and operation performance of the unit. The rotary rectifier bridge is an important part of the generator excitation system and is the most important link in the final realization of the rotor excitation. As a rotary rectifier equipment, it is difficult to achieve online real-time monitoring, the current large-scale nuclear power unit rotary rectifier bridge online real-time monitoring results are not ideal, there is on-site feedback false alarm, the need for high maintenance costs. With the gradual increase of nuclear power units, it is particularly important to develop a real-time online monitoring device for brushless rotary rectifier bridges and to achieve early warning. The equipment can win valuable time for the operation and maintenance of the unit, even if it needs to be protected indirectly by other protections in the event of failure, it can also provide direct data for post-accident problem analysis, locate the fault point, reduce the problem analysis time, improve the maintenance efficiency, and have great economic benefits.

The main and auxiliary switching process involves the large-capacity asynchronous motor used in various systems (such as water pumps, fans, etc.) that are accompanied by strong electrical and mechanical shocks during the restarting or reinput process, especially the influence of the motor group restarting shock. The process includes the dynamic behavior of the electromagnetic and mechanical transient change process. In Order to quantitatively analyze the dynamic behavior of induction motor starting, the general steady-state analysis method can no longer be accurately solved, it is necessary to consider the dynamic load model of the transient process, and select ETAP software to realize the model establishment and transient process simulation calculation. For high-power motor load starting, the motor may fail to start due to low starting torque or other running motors connected to the power grid. Therefore, this paper selects typical high-power motors as the research object as the largest single load, and considers the harsh power supply conditions, and the transient conditions of the above-mentioned plant power switch motor group start, To verify whether the motor starting or restart will cause itself and other motors to stall, or whether it causes the EDG diesel generator to start. Whether the power system of nuclear power plant can resume stable operation after the above transient process has become an important index for evaluating the power system design of nuclear power plant. In this paper, the simulation study of the switching between the main power supply and the auxiliary power supply of the nuclear power plant, and the starting process of the high-power motor is established, the power system model of the power grid is analyzed at high voltage and low voltage, and the transformer is automatically loaded. The on-load voltage regulation, the plant power switching process and the high-power motor starting simulation calculation, effectively reduce the cost of the experiment, Has great economic benefits, it has positive significance for fault analysis.