DC corona characteristics derived from corona cage tests and simulations

This study presents experimental and simulation studies on DC corona characteristics to investigate the behavior of high voltage direct current transmission (HVDC) lines. Experimental studies are performed using an indoor corona cage and various conductor configurations, which are the scaled models of the prospective HVDC line in Turkey. Following the preliminary tests with single line models of aluminum rods and stranded conductors, DC corona inception voltages (CIVs) of prospective bundled conductor configurations are measured by using a daylight UV corona camera and a high-sensitive micro ammeter. Measurements include three different sub-conductor spacing both for the positive and for the negative DC voltages. Corona currents are measured for the voltages above the CIV levels. Experimental studies are varied by complementary simulations using a FEM based software, COMSOL Multyphysics. Following the development of 3D models of the corona cage and the prospective conductor configurations, electric field distribution along the conductor surfaces are determined. CIV measurements and simulation results are used to compute the corona inception electric field strengths of the aforementioned configurations. Radio interference voltages and audible noise levels of the configurations are finally calculated at a constant test voltage using the empirical formulations and the field simulation results. The results are discussed at the end to guide the design of intended HVDC line in Turkey.