Abstract
For high voltage direct current (HVDC) cable, a semi-conductive layer lies between the conductor and the insulation layer; as the charge migrates the path from the conductor to the insulation material, it will affect space charge injection. In this work, the research idea of changing the injection path of moving charges within semi-conductive layer by magnetic particles was proposed. Semi-conductive composites with different SrFe12O19 contents of 1 wt.%, 5 wt.%, 10 wt.%, 20 wt.%, and 30 wt.% were prepared, and the amount of injected charges in the insulation sample was characterized by space charge distribution, polarization current, and thermally-stimulated depolarization current. The experimental results show that a small amount of SrFe12O19 can significantly reduce charge injection in the insulation sample, owing to the deflection of the charge migration path, and only part of the electrons can enter the insulation sample. When the content is 5 wt.%, the insulation sample has the smallest charge amount, 0.89 × 10−7 C, decreasing by 37%, and the steady-state current is 6.01 × 10−10 A, decreasing by 22%. When SrFe12O19 content exceeds 10 wt.%, the charge suppression effect is not obvious and even leads to the increase of charge amount in the insulation sample, owing to the secondary injection of charges. Most moving charges will deflect towards the horizontal direction and cannot direct access to the insulation sample, resulting in a large number of charges accumulation in the semi-conductive layer. These charges will seriously enhance the interface electric field near the insulation sample, leading to the secondary injection of charges, which are easier to inject into the insulation sample.
Highlights
Space charge accumulation and suppression methods of high voltage direct current (HVDC) cable have been hot research topics with the development and application of higher voltage grade cable [1].Space charge accumulation in an insulation layer will cause local electric field distortion, accelerating the degradation and aging of the insulation material [2–5]
The moving charges are subjected to the electric field force in the vertical direction, and only some of the electrons enter the insulation sample
The influence of semi-conductive matrix modified by SrFe12 O19 on charge injection characteristics in the insulation sample were studied
Summary
Space charge accumulation and suppression methods of high voltage direct current (HVDC) cable have been hot research topics with the development and application of higher voltage grade cable [1]. A semi-conductive shielding layer as an essential component of HVDC cable plays an important role in uniform electric field and makes the conductor wire core and the insulation layer connect tightly [6–12]. It is a direct path of charge injected from the conductor to the insulation layer, which has a great impact on charge injection and accumulation in the insulation layer [10,11,13].
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