Li Tianwei

Prediction method on corona inception field intensity for HVDC fittings in high altitude area

Corona inception field strength was one of important parameters for designing fittings in ±800kV DC transmission line. So far Peek formula was based on calculating corona inception field strength of the DC lines fittings with large size in high altitude area. Peek formula was obtained by a large of experimental results for electrode with curvature radius less than 50mm at standard atmospheric pressure. Because of different discharge mechanism, Peek formula was inaccurate for predicting corona inception field strength for the electrode with large curvature radius and non-cylinder structure. For predicting accurately corona inception field strength for the fittings with larger curvature and non-cylinder structure, test platform for HVDC fittings was setup in ultra-high voltage(UHV) Nation Engineer laboratory (Kunming) with 2100 meters altitude. Corona inception voltage was measured for test tubes and rings with kinds of size in the Kunming lab. Prediction method to Peek formula was proposed firstly for the electrode with larger curvature radius and non-cylinder structure in high altitude. The method would become one of theory evidence for design to HVDC fittings.

The impulse grounding impedance computation in HVDC transmission line tower

Electromagnetic field and circuit theory combined is applied to calculate the impulse grounding impedance in HVDC transmission line towers in this paper. The mutual inductance of conductor segments are taken into account. At the same time, the images of the self resistance and mutual inductance are considered for the different medium (soil and air) interface on the surface of the ground. To calculate the impulse grounding impedance, the lightning waveform is transferred to frequency domain by FFT. Through comparison between the results in this paper and the authoritative CDEGS, the theoretical correctness is tested and proved reliable. It will provide theoretical basis for grounding optimal design and type selection, and then improve the reliability of HVDC transmission line operation.