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.

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