Evaluation of Electromagnetic Shielding Performance for the Monitoring Unit Shield of an Ultra-High Voltage Converter Valve

UHVDC transmission technology is an important means for the power grid to achieve large-scale power transmission. The performance of its core equipment, the converter valve, is closely related to the operational reliability of the DC transmission project. In order to achieve reliable triggering, protection, and monitoring functions for the converter valve, the circuit board of the online monitoring unit in the valve tower plays a key role. However, due to the circuit board being directly installed near the thyristors inside the converter valve module, it often operates in a harsh environment with high potential, strong electromagnetic fields, and intense heat. If the electromagnetic compatibility performance of the monitoring unit does not meet the requirements, it may lead to issues such as reduced measurement accuracy, high communication error rates, and communication errors. Therefore, this study focuses on the research of electromagnetic protection for the monitoring unit circuit board. First, based on the ± 800kV converter valve structure, a full-circuit simulation model of the converter valve was established. Then, the calculation method of the electromagnetic field during the operation of the converter valve was analyzed. Combining the frequency-domain finite integration method and circuit time-domain calculation, the level of disturbance caused by the switch-off voltage and turn-on current on the PCB board of the TTM were evaluated. Additionally, the shielding performance of the shield cover on the PCB for far-field and near-field disturbances was assessed. The study concludes that the shield cover can effectively protect against the near-field disturbances generated by the valve module, providing theoretical support for the electromagnetic protection design of the online monitoring unit of the converter valve.