Simulation And Experimental Study On Insulation Damp For Converter Transformers With Long-term Storage

The converter transformer is the core equipment in the HVDC transmission system,and its operating status directly affects the operational reliability of the DC system and the safety of the main grid of the West to East.At present,converter transformers of multiple DC projects have found moisture in transportation and storage processes,causing multiple converter transformer insulation faults.Since the interaction characteristics of insulating paper,residual oil and atmospheric moisture during the transportation and storage of the converter transformer are not effectively grasped,the method for evaluating the insulation state of the converter transformer during transportation and storage process is lacking,and the operation and maintenance personnel are instructed to formulate corresponding measures.In response to the above problems,the main work and research results are as follows:An airflow dynamics model was developed for the dynamic evolution of the dry gas inside the converter transformer and the external atmospheric moisture during the transportation and storage of the converter transformer.The mathematical equations for the diffusion of atmospheric moisture into the internal calculation of the converter transformer are derived.The numerical simulation calculation of the interaction process between the transport and storage of the converter transformer and atmospheric moisture is realized.An equivalent test platform for the interaction between internal dry gas and atmospheric moisture during the transportation and storage of converter transformer was constructed.The test platform for transport and storage of converter transformer under different working conditions was designed and fabricated.The test results obtained by the test platform interacted with moisture.The calculated numerical results have good consistency,which verifies the effectiveness of the numerical simulation method of the airflow dynamics of the converter transformer transporting and storing the internal dry gas and atmospheric moisture dynamic evolution.The test and simulation calculations of good sealing,sealing failure and vacuuming and atmospheric moisture during the transportation and storage of the converter transformer were carried out.The results show that the internal pressure of the converter transformer is the decisive factor for moisture entering the converter transformer,and the temperature change directly causes The change in the air pressure causes the atmospheric moisture to enter the converter transformer.