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It is difficult to reclose transmission line successfully after tree fault occurs, which is easy to cause line outage. At present, most of the existing research focuses on the diagnosis and disposal of tree faults, while the mechanism of tree faults is relatively rare. Firstly, the formation process of tree faults and the typical discharge characteristics at different tree height stages are analyzed. Then, the process of tree-wire gap discharge at different stages is simulated in laboratory environment. With trees approaching transmission lines, corona discharge, hidden discharge and flashover discharge occur in turn, and the discharge increases from weak to strong, and the amplitude increases, while the frequency of discharge waveform tends to decrease.

Common faults on transmission lines, such as insulator pollution flashover, trees flashover, string breakage failure of insulator will undergo a period of discharge before the occurrence of flashover, which is called insulation defect discharge. In this paper, the process of discharge such as floating discharge, insulator pollution discharge and tree discharge is simulated in the laboratory environment and the high frequency current waveform is monitored. The results show that insulation defect discharge will maintain a long period of time and will not immediately form a flashover fault, in addition, a great deal of high frequency discharge current pulses will be generated during this period. The discharge characteristics and the discharge pulses generated by different type of insulation defect discharge are quite different. Frequency of floating discharge current waveform are very high, while the pulse cluster of pollution discharge is dense, and the current waveform generated by tree discharge has notable dispersity. With the degree of discharge increasing, the parameters such as pulse repetition rate and discharge amount are gradually increasing.

Flashover fault is an important cause of trip or even outage of transmission lines. In order to reduce the occurrence of tree flashover failure and strengthen the management of tree growth in the transmission line corridor, it is necessary to study electric field and potential distribution characteristics of trees below transmission lines. Firstly, the influence of tree dielectric constant and conductivity on 3D modelling is analysed. Then the actual 3D simulation model is established. The spatial electric field and potential variation of trees with different shape crowns and different heights and horizontal distances are studied. The starting field strength of flow is used as the gap breakdown criterion, and the critical breakdown distance under different power supply phase angles is calculated. Conclusion shows that the critical distance of tree flashover of 500kV transmission line is 1.76m. In practical applications, trees should be avoided too close to the wire.

Amyloidosis refers to a group of widely diverse conditions characterized by the deposition of insoluble protein within the extracellular space, leading to disruption of normal organ function. AL primary amyloidosis is associated with plasma cell dyscrasias and is caused by the deposition of insoluble kappa or lambda light chains. Cardiac involvement by AL primary amyloidosis has a very poor prognosis, and patients are treated with systemic chemotherapy. Clinically, the presence of cardiac amyloidosis in patients with plasma cell disorders is usually presumed to represent AL primary amyloidosis, and they are often managed as such. We reported four cases of elderly patients with plasma cell disorders who were found to have biopsy-proven cardiac senile transthyretin amyloidosis. Our cases demonstrated that cardiac amyloidosis in patients with plasma cell disorders does not necessarily represent AL primary amyloidosis. Cardiac biopsy is important in making the correct diagnosis. Accurate subtyping of the amyloid has significant implications in the management of patients and discussion of prognosis.